Goodman Cancer Institute Research Symposium | November 17th, 2022
Goodman Cancer Institute
Published online: November 17th, 2022Investigating the role of cancer cell mechanosensing and mechanomemory and their influence on metastatic cell progression
2: Department of Biochemistry, McGill University, Canada
3: Department of Bioengineering, McGill University, Canada
4: Department of Anatomy and Cell Biology, McGill University, Canada
5: Department of Medicine, McGill University, Canada.
Corresponding Author: Afnan Abu-Thuraia, email afnan.abu-thuraia@mail.mcgill.ca
Abstract
The ability of the cell to respond to mechanical cues is mediated predominately by integrins and receptors that link the extracellular matrix (ECM) to the cytoskeleton, which leads to intracellular signaling. The ECM stiffness regulates significant phenotypic changes in the cell and alters gene expression programs that alter different cell processes. Previous work suggests that mechanical cues that alter cell migration and invasion can persist for a long period of time and this cellular behavior is termed “mechano-memory”. However, limited evidence is available demonstrating the presence of such memory encoded in signaling pathways. Here we show that ex vivo breast cancer cells isolated from metastatic sites respond to stiffnesses that resemble the stiffness of the tissue they have been extracted from, suggesting the presence of a mechano-memory response. We found that intra-tibially injected cells, when flushed from the bone ex vivo and cultured on substrates of different stiffness in vitro have higher cell migration and more invadopodia formation when plated on stiff substrates in comparison to the softer ones. Interestingly, these cells cultured on plastic for 7 days lost their enhanced migratory phenotypes on stiff substrates when compared to their ex vivo counterparts, suggesting the presence of time-limited mechano-sensing behavior. Furthermore, conditioning breast cancer cells on a soft or stiff substrate for a specified time period and then re-culturing them on a range of substrate stiffnesses, cells seem to have a preference to invade and migrate on the stiffness they have been conditioned on. These observations indicate that breast cancer cells exhibit the ability to respond to different substrate stiffnesses and exhibit a mechano-memory response. We are currently investigating by spontaneous metastasis assays whether long term priming of cells on soft or stiff substrates have a metastatic site preference to seed in vivo and their underlying mechanisms.
Characterizing Putative Novel Drivers of Triple Negative Breast Cancer
2: Rosalind and Morris Goodman Cancer Institute, McGill University
3: Department of Human Genetics, McGill University, Montreal, QC, Canada
4: Department of Physiology, Faculty of Medicine, McGill University, Montreal, QC, Canada
Corresponding Author: Mariam Ali, email mariam.ali2@mail.mcgill.ca
Abstract
Triple Negative Breast Cancer (TNBC) is one of the most aggressive cancer types with an early age of onset, significant metastatic potential, and poor survival rate. Contrary to other types of breast cancer, TNBC tumors do not express hormonal receptors, making them resistant to classical hormonal therapy and harder to treat with conventional chemotherapy. The Cancer Genome Atlas (TCGA) has enabled the discovery of key genomic changes in over 30 types of tumors and has revolutionized our understanding of cancer prevention, diagnosis, and therapy. We recently devised a multi-faceted genomic strategy to rank gene expression and survival outcome in TNBC patient data from the TCGA to identify new putative drivers of breast cancer progression. Using this strategy, we identified genes FAM129B, ADCK5, PPFIA3, NANS, and SHARPIN that are both strongly correlated with survival outcome in TNBC and have known functions in immunomodulation. We hypothesize that theses gene may be novel drivers of TNBC and could be new, much needed therapeutic targets for this devastating disease. To assess the function these genes in TNBC progression and immunomodulation we will knock them down using shRNAs in TNBC murine cell line (4T1). We will first assess changes in proliferation, migration, and invasion using an the Incucyte Live-Cell Analysis platform and transwell migration and invasion assays. Moreover, we will evaluate changes in chemotaxis using immune microfluidic devices. Furthermore, we will inject our knock down cells intravenously in Balb/c mice to examine changes in metastasis in vivo and assess immunological changes in the tumor microenvironment using multiplex spectral flow cytometry. We expect that the gene knockdowns would result in the reduction of proliferation signature and metastatic nature of the TNBC cells. There is a great urgency in identifying the drivers of TNBC, its metastatic signature, and the molecular mechanisms responsible for relapse and treatment resistance.
A study to understand the bias in somatic mutation frequency of the DDX3X gene between male and female melanoma patients
2: McGill Genome Center
3: Department of Biochemistry at McGill University
4: Goodman Cancer Institute
Corresponding Author: Rached Alkallas, email rached.alkallas@mail.mcgill.ca
Abstract
DDX3X is an X-linked gene that encodes for an ATP-dependent RNA helicase best known for its role in facilitating mRNA translation. Mutations in DDX3X have been identified in multiple cancer types, most frequently in melanoma of the skin, where missense and protein-truncating loss-of -function (LoF) mutations demonstrate evidence of positive selection. We recently observed and reported that, in a cohort of nearly 1,000 cutaneous melanoma tumors, DDX3X LoF mutations are exclusively found in males (P < 1x10-4). Existing models that try to explain this bias require additional evidence. For instance, it has been proposed that DDX3X, which is known to escape X chromosome inactivation, is a haplo-sufficient tumor suppressor, requiring two hits in females but only a single hit in males. However, this hypothesis does not address the role of DDX3Y in males, the Y-linked paralogue of DDX3X, which has ~92% amino acid similarity. Moreover, both the Y-chromosome and inactive X are lost in ~20%-30% of male and female melanoma tumors, respectively. Lastly, it is well-established that at least one copy of DDX3X or DDX3Y is required in cells to maintain their viability. To integrate these observations into a unified model and fill this knowledge gap, we used transcriptomic data from human melanoma tumors and a diverse set of cell lines to identify the mRNA targets of DDX3X and to understand how their expression and translation are impacted by loss of DDX3X and DDX3Y. Our findings will be highly relevant to understanding existing differences in melanoma incidence and in response to therapy between males and females.
Investigating the potential of the honeybee Apis mellifera’s Queen Mandibular Pheromone as a novel chemotherapeutic in ovarian cancer
2: Lady Davis Institute
Corresponding Author: Mariam Anwar, email mariam.hanymohamedanwar@mail.mcgill.ca
Abstract
Ovarian cancer is historically known as the “silent killer” with a 46% survival rate 5 years after the diagnosis. Three out of four women who are initially diagnosed at an advanced stage relapse. Once patients’ relapse, most will no longer respond to the medication currently available. Therefore, new classes of cancer pharmacological agents are direly needed. A multidisciplinary approach, utilizing knowledge from social insect societies, and rooted in evolutionary theory, could potentially reveal a novel class of cancer pharmacological agents including Queen Mandibular Pheromone (QMP) in the Honeybees species Apis mellifera. QMP is used by the queen in the honeybee colonies to inhibit worker ovaries. QMP has cross-species effects on termites, crustaceans and flies. Given these cross-species effects, we hypothesize that QMP could target conserved mechanisms across the phylogeny that could potentially extend to mammalian cells. Royal actin, another substance from honeybee colonies, has proliferative effects that extend to mammals, supporting our hypothesis that there could be homologous mechanisms in honeybees and mammals that can be targeted by substances such as royal actin and QMP. This project will test the effect of QMP on cancer cells both in vitro and in vivo and investigate the mechanisms by which it acts on cancer cells. Lying at the intersection oncology, ecological evolutionary biology, and chemical ecology, this study has the potential to identify a new class of cancer pharmacological agents for further study.
Estrogen regulates the immune microenvironment of colorectal liver metastases
2: Research Institute of the McGill University Health Centre, Glen Site.
3: Department of Surgery, McGill University, Montreal, QC, Canada.
4: Department of Oncology, McGill University, Montreal, QC, Canada.
Corresponding Author: Yasmine Benslimane, email yasmine.benslimane@mail.mcgill.ca
Abstract
Liver metastases (LM) remain a major cause of cancer-related death and many cancers preferably metastasize to the liver due to its unique anatomical location, rich blood supply and immune-tolerant microenvironment. Up to 50% of colorectal carcinoma patients develop LM during their disease and this is associated with a poor prognosis. Our laboratory previously identified a sexual dimorphism in the regulation of the immune microenvironment (IME) of LM and showed that estrogen could promote the accumulation of myeloid-derived suppressor cells (MDSCs) and Tregs in the liver in response to invading cancer cells. The objective of this study was to elucidate the role of estrogen in the recruitment and polarization of other immune cells and to determine the therapeutic potential of Selective Estrogen Receptor Degrader (SERD) therapy in CRCLM bearing female mice, and evaluate if SERD would improve immunotherapy efficacy. In estrogen-competent female mice bearing CRCLM, we found increased gene and protein expression of the immunosuppressive cytokine TGF-β, and inversely a decrease in the pro-inflammatory cytokine TNF-alpha. Furthermore, we identified a significant decrease of immunosuppressive CD68+CD163+ M2 macrophages, and an increase of the pro-inflammatory CD68+TNF-alpha+ M1 macrophages in estrogen-depleted (ovariectomized) mice as compared to estrogen-competent mice. This observation was reversed upon estradiol supplementation. Moreover, treatment of female mice with the SERD Fulvestrant, markedly reduced the number of CRCLM compared to vehicle-treated mice, reduced the cell frequencies and counts of M2 macrophages, significantly increased NK cells recruitment in the liver. The addition of SERD to immunotherapy has a better therapeutic effect than both therapies alone. Taken together, our results identify estrogen as a critical regulator of an immunosuppressive TME in the liver and a potential therapeutic target.
May the cell-generated forces be with you: Investigating tissue stress in breast cancer progression
2: Rosalind and Morris Goodman Cancer Institute, McGill University
3: McGill University Health Centre
4: Division of Experimental Medicine, McGill University
5: Gerald Bronfman Department of Oncology, McGill University
6: Department of Biological and Biomedical Engineering, McGill University
Corresponding Author: Christina Boghdady, email christina-marie.boghdady@mail.mcgill.ca
Abstract
Cells and tissues are dynamic constructs which exert and respond to applied forces during development and growth. Dysregulated forces resulting in loss of tissue structure and stability are key progression factors in diseases like cancer. However, measuring and monitoring the evolution of stresses inside live tissues requires visualizable, biocompatible, and sufficiently compliant mechanical sensors. Thus, we have developed cell-scale force measurement sensors to characterize internal and external stress during tumour growth and invasion. Encapsulated non-invasive breast cancer tumours exhibited an abrupt yet temporary increase in internal stress, while external stress remained compressive. Contrastingly, invasive tumours lost significant internal stress upon dispersal, suggesting that such quantitative tools may benefit as more efficient prognostics to improve patient treatment and outcome.
The role of mTOR pathway in the combination therapy of belvarafenib and cobimetinib in melanoma
2: Segal Cancer Centre, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University
Corresponding Author: Feiyang Cai, email feiyang.cai@mail.mcgill.ca
Abstract
Melanoma is a type of skin cancer. Targeted therapies work in patients with BRAF mutated melanomas, which occupy about 50% of patients, but these same therapies do not work for other melanoma subtypes, which have mutations in NRAS and NF1. In addition, most patients receiving targeted therapy eventually progress because melanoma cells can adapt to the presence of the drug. Researchers have found that the combination of a RAF dimer inhibitor (belvarafenib) and a MEK inhibitor (cobimetinib) is effective to treat non-BRAF-mutant melanoma, but intrinsic and adaptive resistance still occurs. In this study, we determine the sensitivity of non-BRAF V600E mutated melanomas to belvarafenib, cobimetinib and mTOR inhibitor (INK128) triple therapy. We also develop models of melanoma with dual resistance to belvarafenib and cobimetinib. Here we show that inhibitors of mTOR signaling robustly induce apoptosis when combined with belvarafenib and cobimetinib, particularly in the hard-to-treat melanomas with NRAS mutations, for which there are currently no effective therapies. mTOR inhibition also induces apoptosis of belvarafenib and cobimetinib resistant melanoma cells. This research may provide a novel therapeutic strategy to treat NRAS-mutant, NF1-mutant and triple wild-type melanomas, for which existing therapies are lacking. mTOR inhibitors might also be effective to treat melanoma patients who become resistant to belvarafenib and cobimetinib, an emerging clinical problem.
The Role of The Extracellular Matrix Deposited Secreted Frizzled Protein 1 in Melanoma
2: University of Western Ontario, Department of Anatomy and Cell Biology, London, Canada.
3: University of Alberta, Department of Oncology, Edmonton, Canada.
4: McGill, Gerald Bronfman Department of Oncology, Montreal, Canada.
5: Queen's University, Biomedical and Molecular Sciences, Kingston, Canada.
Corresponding Author: Nabila Chekkal, email nabila.chekkal@mail.mcgill.ca
Abstract
Secreted Frizzled Protein 1 (SFRP1) is a protein deposited in the extracellular matrix (ECM) that belongs to the family of Secreted Frizzled Proteins. These proteins are thought to act as Wnt antagonists. Aberrant Wnt signaling was identified as a major actor in the initiation and development of certain cancers. However, our preliminary studies revealed that SFRP1 overexpression correlates with poor patient outcomes in melanoma. Unlike most cancers that are often highly glycolytic, melanomas switch to oxidative phosphorylation during dissemination and in response to therapeutic stress. We hypothesize that SFRP1 driven ECM signaling is involved in melanoma metabolic reprograming. SFRP1 expression was genetically modified in C8161 and A2058 melanoma lines and tumor growth wAS measured. Steady-state RNA was isolated from xenograft tumors of the modified cells and analyzed by RNAseq. Seahorse and steady-state Metabolome analysis were performed. SFRP1 loss in C8161 cells decreased cell proliferation in vitro. Moreover, there was a reduction in subcutaneous tumor growth in vivo that was partially rescued by SFRP1 re-expression. Hence, SFRP1 may exhibit tumor-promoting properties in melanoma. Also, our results show that reduced SFRP1 levels are paralleled by profound cellular bioenergetics perturbations. RNAseq revealed enrichment in genes involved in metabolic regulation and mRNA translation upon SFRP1 loss. SFRP1-deficient cells have an increased dependence on glycolysis compared to SFRP1-proficient cells. SFRP1 loss increased mTORC2-AKT pathway activity, which acts as a major stimulating signaling pathway of glycolysis. Our results support the idea that SFRP1 driven ECM signaling modulates metabolic reprograming in melanoma to fuel cancer progression. By understanding the role of SFRP1 in melanoma, we hope to identify predictive response markers to SFRP1 inhibition therapy in patients, as well as shed better light on the molecular foundations of ECM signaling in cancer.
Germline missense variants in CDC20 result in aberrant mitotic progression and familial cancer
2: Department of Biochemistry, McGill University
3: Department of Human Genetics, McGill University
4: McGill University and Génome Québec Innovation Centre
5: Lady Davis Institute, Jewish General Hospital
6: Research Institute of the McGill University Health Centre
7: Department of Biology, McGill University
8: Department of Epidemiology, Biostatistics & Occupational Health, McGill University
9: Department of Pediatric Hematology and Oncology, Pediatrics III, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany
10: Clinic of Pediatrics, Dortmund Municipal Hospital, Dortmund, Germany
11: Institute of Human Genetics, University of Ulm & Ulm University Medical Center, Ulm, Germany
12: Department of Histopathology, King Edward Memorial Hospital, and School for Women’s and Infants’ Health, University of Western Australia, Perth, Australia
13: Institute of Cancer Research, London, United Kingdom
14: Faculty of Health Sciences, University of Macau, Macau SAR, China
15: Department of Medical Genetics, National Institute for Health Research Cambridge Biomedical Research Centre, University of Cambridge, Cambridge, United Kingdom
Corresponding Author: Owen Chen, email owen.chen2@mail.mcgill.ca
Abstract
CDC20 is a coactivator of the anaphase promoting complex/cyclosome (APC/C) and is essential for mitotic progression. The APC/CCDC20 complex is inhibited by the spindle assembly checkpoint (SAC), which prevents premature separation of sister chromatids and aneuploidy in daughter cells. Although overexpression of CDC20 is common in many cancers, oncogenic mutations have never been identified in humans. Using whole-exome sequencing, we identified heterozygous missense CDC20 variants (L151R and N331K) that segregate with ovarian germ cell tumors in two families. Functional characterization showed these mutants retain APC/C activation activity but have impaired binding to BUBR1, a component of the SAC. Expression of L151R and N331K variants promoted mitotic slippage in HeLa cells and primary skin fibroblasts derived from carriers. Generation of mice carrying the N331K variant using CRISPR-Cas9 showed that, although homozygous N331K mice were nonviable, heterozygotes displayed accelerated oncogenicity of Myc-driven cancers. These findings highlight an unappreciated role for CDC20 variants as tumour-promoting genes.
Pro-oncogenic role of the HuR RNA-binding protein V225I Mutation in Adult T-cell Leukaemia/Lymphoma
2: Rosalind & Morris Goodman Cancer Institute, McGill University, Montreal, QC, Canada
3: KAUST Smart-Health Initiative and Biological and Environmental Science and Engineering (BESE) Division, King Abdullah University of Science and Technology (KAUST), Jeddah, Saudi Arabia
Corresponding Author: Bianca Colalillo, email bianca.colalillo@mail.mcgill.ca
Abstract
HuR is a ubiquitously expressed RNA-binding protein and post-transcriptional regulator that plays a role in mRNA localization, turnover, and processing, by binding to the 3’UTR of its target transcripts. HuR has been shown to be involved in apoptosis, whereby in response to lethal stress, HuR is cleaved at Aspartate 226 (D226) to generate two cleavage products which induce cell death. A recent study identified a mutation in HuR, HuR-V225I, of a patient with Adult T-cell Leukemia/Lymphoma (ATLL). ATLL is a rare neoplasm of mature T-cells caused by infection with the human T-lymphotropic virus type-I (HTLV-I) retrovirus. This Hur-V225I mutation is of particular interest due to its proximity to HuR’s apoptotic cleavage site. Given that HuR is involved in apoptosis, and that the apoptotic pathway is commonly dysregulated in transformed ATLL cells, this study aims to determine whether HuR-V225I affects HuR’s role as a pro-apoptotic factor and whether HuR-V225I contributes to apoptotic resistance in ATLL. Using GFP-tagged wild-type or V225I mutant HuR, we aim to assess the effect of the V225I mutation on the localization of HuR, its caspase-mediated cleavage, and the resulting percentage of apoptotic cells. We plan to determine if the V225I mutation affects HuR’s interaction with its known protein partners, such as PP32, by performing immunoprecipitation experiments. Finally, we will examine whether the V225I mutation interferes with the post-transcriptional regulation of the caspase-9 mRNA by assessing the stability and expression of this mRNA. We believe that this study will lead to a better understanding of HuR’s role in cancer-associated immune evasion/apoptotic resistance and uncover a tumor suppressive role for HuR in ATLL that can be abolished through mutation at V225I.
Surveying the tumor suppressive genetic network underlying chr4p deletion in TNBC
2: Department of Biochemistry, University of Toronto
3: Rosalind & Morris Goodman Cancer Institute, Department of Human Genetics, McGill University
Corresponding Author: Joseph Del Corpo, email joseph.delcorpo@concordia.ca
Abstract
Triple negative breast cancer (TNBC) is a breast cancer subtype lacking targetable biomarkers, resulting in worse patient prognosis. TNBC has been characterized by various large copy number variants, resulting in the deletion and amplifications of many genes. Our group showed that chromosome 4p (chr4p) is recurrently deleted in basal breast cancer, correlating with poor prognosis and a highly proliferative state. In this study, we aim to identify specific chr4p genes and their genetic interactions that drive tumor growth by uncovering tumor suppressors and mapping the tumor suppressive genetic interaction network underlying chr4p deletion. We are using an arrayed CRISPR-enCas12 screen and MCF10A cell models to generate loss of function mutants involving 112 chr4p protein-coding genes and characterize their effects on cell proliferation, apoptosis, senescence and cell transformation. An enCas12-expressing MCF10A cell line and dual guide-RNA library will be used to test a subset of these genes for all possible pairwise combinations to identify tumor suppressive genetic interactions. Proliferation of these double gene deletion mutants will be monitored and compared to the single gene deletion mutants to quantify the resulting genetic interactions, which will be used to generate a comprehensive map of the tumor suppressive genetic network in chr4p. This work will be the first to systematically identify tumor suppressor genes within chr4p, map the tumor suppressive genetic interaction network promoting TNBC tumor initiation and progression, and provide in-depth understanding of the genetic network of large copy number variants in TNBC.
Chromosome Arm Aneuploidies As Genetic Vulnerabilities Of Triple-Negative Breast Cancer
2: Centre for Applied Synthetic Biology, Concordia University, Montreal, QC, Canada.
3: Department of Biochemistry, McGill University, Montreal, QC, Canada.
4: Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC, Canada.
5: Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
6: Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
7: Department of Human Genetics, McGill University, Montreal, QC, Canada.
Corresponding Author: Rohan Dandage, email rohan.dandage@concordica.ca
Abstract
Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer. It has no approved targeted therapies due to the lack of the expression of key biomarkers, namely Estrogen and Progesterone receptors, and HER2 amplification. As a result, TNBC has the worst prognosis compared to other breast cancer subtypes. We previously showed that chromosome 4p (chr4p) loss is recurrent, correlates with poor prognosis, is an early event in tumor evolution, and confers a proliferative advantage. Here, we propose to leverage chr4p loss as a genetic vulnerability of TNBC by identifying its genetic interactions (GIs) with genes whose inactivation leads to synthetic lethality — loss of viability of chr4p copy loss cells, but not of the chr4p copy neutral cells — or suppression i.e., positive GIs. We first classified breast cancer cell lines with TNBC enriched molecular subtype called basal-like, as chr4p copy loss (9) and chr4p copy neutral (7), using copy number data from CCLE. Associated with chr4p copy loss, the differential expression analysis carried out using CCLE data revealed global transcriptomic changes that distinctly cluster the chr4p copy loss and chr4p copy neutral cell lines. We then used the publicly available CRISPR-based genome-wide gene inactivation data from the DepMap project and quantified chr4p loss associated GIs using multiple scoring methods such as drugZ and MAGeCK. After integrating the GIs, we prioritized a subset of them for subsequent experimental validation using CRISPR-Cas9 based gene editing in TNBC cancer cell line models. Alongside, using the publicly available drug sensitivity data obtained from the PRISM project, we identified drugs that impair cell growth in a chr4p loss specific manner. Collectively, the set of GIs, the drug sensitivities, and the computational methods we have generated are unique resources for developing precision oncology therapeutic strategies for TNBC, as well as other cancers harboring chr4p loss.
Characterization of KMT2A-rearrangement acute myeloid leukemia biomarkers
Corresponding Author: Sarah Denford, email sarah.denford@umontreal.ca
Abstract
Following the development of acute myeloid leukemia driven by KMT2A-MLLT3 fusions in murine models and patient samples, several genes were found to be biasedly expressed in these cells compared to healthy or other other leukemic cells. In an attempt to determine if and how these genes influence leukemogenesis, we are characterizing selected putative biomarkers by identifying their modes of regulation and cellular functions in AML cell lines, the first of which is METTL7B. This methyltransferase protein of the methyltransferase-like family has been found to have an impact on cell proliferation and metastasis in solid cancers. Results of METTL7B microscopy and knockout experiments in KMT2A-MLLT3 AML cell lines have demonstrated that METTL7B is a cytoplasmic protein localized at the endoplasmic reticulum and involved in cell proliferation. Alongside microscopy data showing ties to the ER, BioID interactome results have also identify multiple interactions between METTL7B and proteins involved in protein synthesis, folding and transport. Since METTL7B is a biomarker in KMT2A-MLLT3 AML, analysis of its function within leukemic cells should identify the changes in cellular properties associated within the translocation. Therefore, the characterization of METTL7B should, in turn, elucidate if this is a lucrative biomarker for therapeutic targeting.
CTCF Loss Potentiates P53 Mediated Gene Transcription in Breast Tissue
Corresponding Author: Meredyth Elisseou, email Meredyth.Elisseou@mail.mcgill.ca
Abstract
A single copy loss of CTCF is found in about 50% of breast cancer patients. Based on clinical TCGA data we hypothesized that the loss of CTCF may potentiate TP53 target gene expression in patients. Using MCF10A cells as a model, we deleted a single copy of CTCF using CRISPR/Cas9. We found, using qPCR and RNA-seq, that cells carrying low CTCF displayed an enhanced TP53 response after exposure to chemotherapeutics. Using ATAC-seq, we aimed to explore whether the elevated induction of TP53 target gene transcription was associated with changes in open or closed chromatin structure. Specifically, we were interested in comparing chromatin accessibility at TP53 target genes within MCF10A CTCF +/- cells compared to control cells following the induction of DNA damage (6uM cisplatin for 8h). We discovered that accessibility of the transcription start site is associated with heightened gene expression in CTCF+/- cells compared to the control. Interestingly, for a subset of TP53 response genes, there is increased accessibility on both transcriptional start sites and termination sites following the induction of DNA damage. The importance of chromatin accessibility at these two regions is still under investigation. Additionally, accessible gene regions at both sites also appear to have greater enrichment within TADS in the CTCF+/- cell compared to the control. We propose that the increased accessibility of P53 target genes following damage represents a mechanism enhancing the efficacy of the TP53-regulated DNA damage response.
DELINEATING METABOLIC PROGRAMS IN COLORECTAL CANCER LIVER METASTASES
2: Department of Medicine, McGill University
3: Cancer Research Program, McGill University Health Center Research Institute
4: Translational Cancer Research Unit, GZA Hospitals, Iridium Netwerk and University of Antwerp, Antwerp, Belgium
5: Department of Biochemistry, McGill University
Corresponding Author: Charlotte Girondel, email charlotte.girondel@mail.mcgill.ca
Abstract
INTRODUCTION. Metabolic reprogramming is a hallmark of cellular transformation, yet less is known about metabolic changes that accompany metastasis. Here, we investigate metabolic programming in colorectal cancer liver metastases (CRCLMs) exhibiting two major histopathological growth patterns (HGPs), including desmoplastic (DHGP) and replacement (RHGP) type lesions. While histopathological characteristics have been identified for each HGP, the cellular and molecular mechanisms involved are only now being elucidated. METHODS. The use of unique patient-derived xenografts (PDXs) established from CRCLM patients diagnosed with either DHGP of RHGP type liver metastases, combined with robust metabolomics and transcriptomic approaches will enable a thorough characterization of these two HGPs. RESULTS. Our principal hypothesis is that DHGP and RHGP will engage specific metabolic programs contributing to their different prognostic values. Furthermore, RHGP type CRCLMs may exhibit a greater degree of reliance on hepatocyte-derived metabolites for their growth when compared to DHGP type lesions. Interestingly, creatine (Cr) and phosphocreatine (PCr) have been shown to promote the growth of CRCLMs in different mouse models. Preliminary analysis of transcriptomic data sets of CRCLM patients shows that several of the Cr/PCr enzymes are up-regulated in RHGPs compared to DHGPs lesions. We are currently assessing how creatine is used by DHGPs and RHGPs by examining the expression levels of the proteins involved in the Cr/PCr system and measuring Cr expression in DHGPs and RHGPs patient samples and PDXs. CONCLUSIONS. We expect that unique histopathological features associated with the different types of lesions will result in different metabolic programming in these CRCLMs. IMPACT. Understanding how these distinct metastases fulfill their bioenergetic needs may reveal therapeutic vulnerabilities that can be exploited to better manage CRC patients with liver metastases.
Identification and Functional Characterization of Novel Metastasis Driving Mutations from Gastroesophageal Adenocarcinoma
2: McGill University
3: McGill Genome Center
4: Human Genetics Department
Corresponding Author: Ansley Gnanapragasam, email ansley.gnanapragasam@mail.mcgill.ca
Abstract
Gastroesophageal adenocarcinoma (GEA) is a leading cause of cancer-related death worldwide with a five-year survival rate of less than twenty percent. The development of peritoneal metastasis (PM) is the most common progression of GEA and leads to an exceptionally poor prognosis with a median survival rate of less than four months. The lack of actionable target genes involved in the progression of GEA has made it difficult to understand and treat its progression. Through whole exome sequencing of 10 patient-matched primary GEA tumors, peritoneal metastases, and adjacent normal tissues (n=30), we have identified several genes that are enriched with somatic mutations among the PM samples when compared to their gene-specific mutation frequency in a large, publicly available, sample from The Cancer Genome Atlas (n=289). Most strikingly, we identified a novel recurrent mutation, p.A17E, in the bicaudal D homolog 2 (BICD2) gene in forty percent (4/10) of our PM samples. The p.A17E mutation of BICD2 has been observed at low frequency in other cancer types, including those that metastasized to the peritoneum. Overexpression of mutant BICD2 in multiple cell lines reveals significant differences in proliferation, adhesion, morphology, and ploidy. Furthermore, preliminary in vivo results reveal an increase in metastasis in mice orthotopically injected with cells expressing mutant BICD2. Our work has identified multiple novel candidate genes potentially driving the progression of GEA to PM, including BICD2. By assessing the role of BICD2 and the p.A17E mutation in the progression of gastric cancer to PM, we will determine whether it represents a new driver of metastasis and potentially actionable pathway for the treatment of GEA and its progression. Furthermore, functional investigation of the other significantly mutated genes we identified can lead to the discovery of additional GEA progression genes allowing for stratification of patients and improved targeted therapies.
Title: Deciphering the regulation of p21 in ovarian cancer senescent cells according to p53 status
2: Université de Montréal, Département de radiologie, radio-oncologie et médecine nucléaire
Corresponding Author: Erwan Goy, email erwan.goy.chum@ssss.gouv.qc.ca
Abstract
Introduction: Ovarian cancer (OC) has different subtypes, among them: High-grade serous carcinoma (HGSC), the most common and often p53 mutated; Clear cell carcinoma (CCC), resistant to chemotherapy, and often wild type for p53. We showed that HGSC cells could enter in senescence with therapy. Cell senescence is a stable proliferation arrest that can be caused by DNA damage including from cancer therapies. DNA damages will activate the p53 pathway, a transcription factor of p21, a Cyclin Dependant Kinase Inhibitor responsible for cell cycle arrest. In HGSC, we have shown that senescence is targetable by senolytics drugs. In preliminary experiments, we find that senescence in HGSC depends on p21, but not p53. Alternatively, senescence depends on p53/p21 in CCC. In general, CCC are highly resistant to therapy, but whether p53 status and p53-independent p21 regulation influence therapy success remains unknown. Thus, my objective is to decipher the regulation of p21 and its role in cell fate after therapy Results: We identified p21SEN, a p53-independent senescence-specific fragment of the p21 promoter. We created a reporter of p21SEN activity: p21SEN-tGFP In HGSC cells (P53 mutated) or in CCC cells with shP53, we show an increase in p21sen activity after radiation. We also show that p21SEN is activated by Histone Deacetylase inhibitor thus independently of DNA damage. Moreover, the activity of p21 p53-independent is correlated with senescence induction. The DNA sequence of p21SEN reveals different Transcription Factors (TFs) binding sites. We are investigating their role in p21SEN regulation by shRNA. Conclusion: Our preliminary results indicate that P21 regulation is independent of p53 and DNA damage. Moreover, p21 may have a role in senescence induction which remain to test by RNA interference. By fusing the p21SEN promoter with luciferase we will investigate the induction of senescence in treated xenograft and its sensitivity to senolytics.
Recurrence of β1 integrin-deficient mammary tumours from dormancy involves both cancer cell intrinsic and extrinsic adaptations
2: Department of Biochemistry, McGill University, Montreal, Canada
Corresponding Author: Yu Gu, email yu.gu3@mail.mcgill.ca
Abstract
The molecular and cellular mechanisms behind mammary tumour dormancy are unclear and how these processes are dynamically orchestrated to allow for tumour recurrence remains to be elucidated. Here, we report that mammary epithelial specific disruption of β1 integrin in a murine model of Luminal B human breast cancer drastically impairs tumour growth. This phenotype is accompanied with proliferation block, apoptosis induction and cellular senescence, altogether resulting in tumour mass dormancy. Dormant lesions show activation of p53 tumour suppressor, and tumours that eventually escape dormancy possess mutations in this pathway analogous to that in human disease. We further validate that mammary epithelial deletion of p53 in β1 integrin-deficient mice fully rescues dormant tumour phenotype and bypasses cellular senescence. Additionally, recurrent β1 integrin-deficient tumors exhibit fibrosis with increased cancer-associated fibroblast infiltration and extracellular matrix deposition. Taken together, these observations argue that β1 integrin modulates p53-dependent cellular senescence resulting in tumour dormancy and that intrinsic genetic mutation and pro-tumourigenic stromal cues are required for recurrence.
The Role of ERRα in Dictating the Hepatic Metabolic Response to Dietary Sugars
2: Department of Biochemistry McGill
3: Faculty of medicine, McGill University, Montreal, Canada
Corresponding Author: Christina Guluzian, email christina.guluzian@mail.mcgill.ca
Abstract
Over the past 40 years, increased consumption of sucrose and HFCS in sweetened beverages has paralleled the rising incidence of obesity, diabetes and NAFLD in Canadians. Both of these added sweeteners are composed sugar monomers, glucose and fructose, two six membered carbon rings that have vastly different metabolic fates in the body. In particular, liquid fructose on a high fat diet (HFD) uniquely causes mitochondrial dysfunction and altered morphology, resulting in a compensatory upregulation of the master regulator of mitochondrial biogenesis, PGC1-α. The PGC1 co-activator family has been extensively linked to the transcriptional activities of another well known group of metabolic regulators, the estrogen-related receptors (ERRs). As such, we hypothesize that fructose could be another external modulator of the ERR/PGC1 transcriptional axis and sought to detangle the role of the nuclear receptor ERRa in this process. Gain and loss of function ERRa mouse models were subject to a HFD supplemented with 30% glucose or fructose solutions for 10 weeks. Overall, loss of ERRα in mice fed a HFD supplemented with glucose gained significantly less weight, despite increased caloric intake as compared to just a HFD. These mice seemed to be protected from diet induced obesity, hepatic steatosis, and glucose intolerance, as they showed decreased adipose tissue mass, liver weights and lowered fasting glucose levels. Conversely, overabundant ERRa protein expression in mice fed a HFD supplemented with fructose, showed a similar protective phenotype, highlighting a possible divergent role for ERRa in the glucose fructose metabolism. Overall the project falls in line with previous literature and our understanding of ERRa regulating genes involved in lipid utilization, insulin sensitivity, and mitochondrial function but its loss and overabundance in protecting against excess glucose and fructose consumption is novel and merits further investigation.
Investigating the role of mTOR/AR/NuRD on gene regulation in prostate cancer
2: Department of Biochemistry, McGill University
Corresponding Author: Stephanie Han, email lingwei.han@mail.mcgill.ca
Abstract
Prostate cancer (PCa) progression is largely regulated through androgen acting on the androgen receptor (AR), leading to a global change in gene transcription. Mammalian target of rapamycin (mTOR) is another key factor in PCa progression and emerging studies revealed that mTOR directly regulates gene expression by associating with chromatin in the nucleus (nmTOR). However, the detailed mechanism on how nmTOR regulates gene expression with AR in PCa remains unclear. Recently our group uncovered a nmTOR-AR functional crosstalk in PCa cells where upon androgen stimulation, nmTOR associates with chromatin and activates an oncogenic metabolic gene program in an AR-dependent manner. Using a proteomic approach referred to as rapid immunoprecipitation mass spectrometry of endogenous protein (RIME), we previously identified the nucleosome remodeling and deacetylase (NuRD) complex as a partner of nmTOR-AR bound on chromatin in PCa cells. Here we demonstrate a mTOR-AR-NuRD functional transcriptional complex where nmTOR, AR, and the catalytic subunits of NuRD, HDAC1/2 and CHD4, associate and dissociate with their common target genes at the same timepoints, subsequently affecting transcription of these genes. Loss of HDAC2 resulted in a delay of chromatin binding of mTOR, AR, and other NuRD components and concomitant decrease in target gene transcription.
The validation of novel small-molecule neuroserpin inhibitors as a corrective therapy for NGF maturation deficits in Alzheimer’s disease.
2: Department of Pharmacology, McGill University
3: Department of Pharmacology, Oxford University
Corresponding Author: Benjamin Kannel, email benjamin.kannel@mail.mcgill.ca
Abstract
In Alzheimer’s disease (AD) there is a progressive loss of the cholinergic neurotransmitter system which plays a vital role in memory functions and cognition in general. The neurons involved in this system, called basal forebrain cholinergic neurons, require the mature form of nerve growth factor (mNGF) to maintain their health. Starting at preclinical stages of the AD progression, the extracellular pathway which generates mNGF becomes dysregulated, and these neurons become atrophic. This atrophy of the cholinergic neurotransmitter system is considered central to the onset of clinical symptoms in AD. As such, we hypothesize that it is this dysregulation of the mNGF pathway in AD, lowering the bio-availability of mNGF, which results in the progressive atrophy of cholinergic synapses and heavily contributes to downstream symptoms. Therefore, correcting this dysregulated mNGF pathway could serve as a therapeutic target to preserve the cholinergic neurotransmitter system and delay the onset of symptoms in AD. A key candidate of intervention in the dysregulated mNGF pathway is to downregulate neuroserpin, which is upregulated in the disease resulting in a lack of mNGF production. To this end, we have first identified 22 candidate neuroserpin inhibitors out of 1000,000 molecules through in-silico analyses. Then we generated an in vitro assay for testing the effectiveness of the potential neuroserpin inhibitors. Our next plan will be to move from in-vitro small-molecule validation to an in-vivo model of AD modification. If successful, this approach could offer a new paradigm in the treatment of AD.
Investigating the importance of the RGG/RG motif in SARS-CoV-2 infection
Corresponding Author: Sarah Khan, email sarah.khan6@mail.mcgill.ca
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious positive-sense single-stranded RNA virus that expresses four main structural proteins: spike, envelope, membrane, and nucleocapsid (N). Protein arginine methyltransferases (PRMTs) are known to methylate viral proteins and regulate their biology. It was previously unknown whether PRMTs methylate and regulate SARS-CoV-2 proteins. Recently, we reported that the N protein is methylated by PRMT1 at RGG/RG sites, R95 and R177 (1). Further, we showed that arginine methylation of the N protein supports viral replication as it is required for N protein binding to the 5’ UTR of SARS-CoV-2 genomic RNA, a requirement for viral packaging, and suppresses stress granule formation, which likely functions to suppress the host immune response and favor viral replication. These findings identify a new post-translational modification that regulates SARS-CoV-2 biology and potentially widens the range of applications for type I PRMT inhibitors currently in clinical trials for the treatment of cancer. Herein, my project aims to identify new arginine methylation sites within SARS- CoV-2 proteins and their interacting cellular proteins. We identify components of RNA-binding protein complexes involved in splicing and translation with monomethylated, asymmetrically dimethylated, and symmetrically dimethylated N R95. Additionally, my project aims to characterize autoantibody responses in SARS-CoV-2-infected patients. We report that infected patients develop IgG antibodies for cellular RGG/RG motifs, and the development of these antibodies is significantly increased by infection.
The CNNMs-PRLs interaction in signaling and kidney genetic diseases.
2: Department of Biochemistry, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada
3: Radboud institute for molecular life sciences, Radboud University Medical Center, P.O.Box 9101, 6500 HB Nijmegen, the Netherlands
Corresponding Author: Hira Khursheed, email hira.khursheed@mail.mcgill.ca
Abstract
The CNNMs (1-4) consist of a four homologous gene subfamily encoding magnesium transporters. One of those, Cyclin M2 (CNNM2), is ubiquitously expressed in mammalian tissues notably in brain, kidneys, and lungs. Importantly, CNNM2 was reported to be involved in Mg2+ homeostasis in kidney. Patients’ mutations identified to date have revealed CNNM2 involvement in rare diseases presenting various severities of hypomagnesemia, seizure, and intellectual disability (HSMR) characterized by low Mg2+ serum level. Our previous work uncovered that the four CNNMs interact directly and are regulated by the Phosphatases of Regenerating Liver (PRLs), also known as PTP4A1,2,3. This complex formation seems to be increased in condition like hypomagnesemia to modulate the intracellular Mg2+ level. We recently identified another set of interactors named ADP-ribosylation factor-like 15 (ARL15). This protein interacts directly with CNNM2 and modulates its N-glycosylation activity thus affecting CNNM2 plasma membrane localization and Mg2+ uptake. We performed biochemical studies of these patient reported CNNM2 mutations to characterize the interaction with PRLs and ARL15 that could explain this disease condition. The basic and applied knowledge gain and potential applications in genetic and infectious diseases, open innovative avenues to understand fundamental biology, their associated genetic and putative directions for novel therapeutics.
Role of Mammary Macrophages in Early Breast Cancer
2: Division of Experimental Medicine, McGill University
Corresponding Author: Rachel Kim, email rachel.kim2@mail.mcgill.ca
Abstract
Currently, there is no accurate way of predicting risk of progression from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). All DCIS patients are treated, leading to concerns of overtreatment. An improved understanding of the factors governing DCIS progression is needed to develop biomarkers to stratify patients. In the breast, ductal macrophages (DMs) detect and eliminate apoptotic epithelial cells. Stromal macrophages (SMs) remodel the extracellular matrix during development and promote invasion in breast cancer. The role of DMs during cancer progression is unclear. Immunostaining of DCIS from mouse models and patient biopsies revealed that activated macrophages reside in the lumen of DCIS lesions. The presence of these luminal macrophages (LMs) correlates with a reduction in DMs and eventual accumulation of SMs at the tumour periphery. We hypothesize that DMs are recruited to the lumen of ducts to remove dying epithelial cells in DCIS, which exerts an anti-cancer effect. In my immunostaining, I observed that only LMs express the protein C1q. LMs appear bloated compared to DMs and SMs, and they associate with nests of dying epithelial cells in the ductal lumen and often contain epithelial debris, indicating phagocytic activity. I will investigate C1q’s role in LMs by immunostaining mouse and human tissue sections for C1q’s receptors and by using a blocking antibody to inhibit C1q function in mice. To study the interactions of DMs with their epithelial microenvironment, I have devised a novel organoid model termed MacO. These organoids consist of mouse mammary duct fragments with their resident DMs that are maintained in culture. MacOs are an efficient model: isolation from a single mouse yields numerous organoids, which nearly all have at least one DM. Using clodronate liposomes, I will ablate DMs from MacOs and apply this in combination with oncogene induction in MacOs to study the functional consequences of DMs during tumour progression.
Determining the role of GREB1L in trophoblast cells
2: Department of Electrical and Computer Engineering, McGill University
3: The Meakins-Christie Laboratories at the Research Institute of McGill University Health Centre
4: Mila, Quebec AI Institute
5: The Rosalind & Morris Goodman Cancer Institute, McGill University
Corresponding Author: Brenda Lynn Koborsy, email brenda.koborsy@mail.mcgill.ca
Abstract
By analyzing data from CRISPR/Cas9 screens conducted by the DepMap consortium, we have determined that Growth Regulation by Estrogen in Breast Cancer 1 Like (GREB1L) is selectively essential for the survival of placental cancers called choriocarcinomas. This suggests a role for GREB1L in placental development. GREB-family proteins have been implicated in glycosylation of nuclear receptors, retinoic acid signaling, and vertebrate renal system development. However, GREB1L’s role in the placenta has never been investigated. We generated GREB1L knockout (KO) human trophoblast stem cells (hTSCs) using CRISPR/Cas9. GREB1L KO hTSCs show no morphological or survival abnormality. However, flow cytometry indicates downregulation of the differentiation marker Integrin-α-1, suggesting impaired propensity for differentiation. Using immunofluorescence staining, hCG ELISA, and RNA-sequencing, we determined that loss of GREB1L impairs differentiation to syncytiotrophoblast lineage. Additionally, differentiation into extra villous trophoblasts is impaired in the KO cells as demonstrated by flow cytometry. In summary, our preliminary data indicates a role for GREB1L in facilitating differentiation of placental cells.
Purification of recombinant soluble Prorenin Receptor to study its effect on cancer.
2: Department of Biochemistry
Corresponding Author: Daniel Krauss, email daniel.krauss@mail.mcgill.ca
Abstract
The Prorenin Receptor (PRR) is a single-spanning transmembrane protein. PRR is cleaved to form an N-terminal secreted fragment called secreted PRR (sPRR), and a short intracellular transmembrane C-terminal fragment called M8.9. sPRR is an important component of the renin angiotensin system for blood pressure regulation. M8.9 is an essential co-factor required for the activity of the V-ATPase proton pump. The V-ATPase complex is required for the acidification of intracellular vesicles and is critical for many processes in cancer including autophagy and growth. Recently, the lab screened for secreted factors affected by the loss of PTEN, a common mutation in cancers. We were able to demonstrate that sPRR was increased in cancers with PTEN loss, and higher amount of sPRR correlates with the tumor size in these patients. We genetically engineered mice (called PRRpm) with a point mutation in the PRR (ATP6AP2) gene preventing the cleavage of PRR into sPRR and M8.9, and have isolated mouse embryonic fibroblasts (MEFs) from both PRRpm and wild-type littermates. Investigations in the lab have shown that the mutated mice have little or no sPRR present in their blood. Although they do possess V-ATPase activity, lysotracker analysis on the MEFs has shown that the wild-type MEFs have significantly higher V-ATPase activity than their PRRpm counterparts. We have also crossed our PRRpm mice with Eµ/Myc mice and found that our mutation protects these mice from the cancer burden. Another group of researchers has produced recombinant sPRR (rsPRR), and injected it into obese mice, reversing the obesity. This, with the phenotype of our engineered mice, suggests that sPRR may play a role as a metabolic regulator. We purified 6His-tagged rsPRR from a baculovirus expression system using Sf9 cells in suspension and metal affinity resin. Using this rsPRR and various assays including a lysotracker and lentiviral transformation assay, we hope to help elucidate the role of PRR in cancer.
ERR𝛾 loss promotes neuroendocrine differentiation in PTEN-deficient prostate cancer
2: Department of Biochemistry, McGill University
Corresponding Author: Letty Ting Li, email letty.ting.li@mcgill.ca
Abstract
Increasingly effective therapies targeting the androgen receptor have paradoxically contributed to the incidence of neuroendocrine prostate cancer (NEPC). Although NEPC is the most lethal subtype of castration-resistant prostate cancer, the underlying mechanisms remain incompletely understood and effective treatments remain undiscovered. Here, by generating a novel mouse models, we demonstrate that prostate specific deletion of the nuclear receptor ERR𝛾 promotes neuroendocrine differentiation of prostate adenocarcinoma triggered by PTEN deficiency, promotes prostate cancer progression, and accelerate tumor growth in mice. A human NEPC dataset also shows that expression of ERR𝛾 is downregulated in primary and treatment-induced NEPC. The loss of ERR𝛾 results in a global metabolic reprogramming through an mTORC1-driven pathway, which supports cell proliferation and favor the development of NEPC characteristics. Re-expression of ERR𝛾 reverses high levels of NEPC markers and inhibits NEPC differentiation and impedes growth of PTEN-deficient prostate cancer cells. Altogether, we have uncovered a metabolic vulnerability triggered by ERR𝛾 deficiency in NEPC, which offers potentially actionable targets to prevent therapy resistance in PCa.
What is shaping epithelial cells in aggregates?
2: Department of Human Genetics, McGill University
3: Department of Biochemistry, McGill University
Corresponding Author: Jenny Li, email yuwen.li2@mail.mcgill.ca
Abstract
The factors that govern cellular morphology and aggregation are the keystone for complex developmental processes like tissue formation in metazoans. While all epithelial cells form cell-cell contacts, the morphology of the epithelial cells can vary in different tissues of the body. Previous studies (Turlier 2015) have theorised that contractile forces within the cells can modulate the interactions at the cell-cell interface. Currently, there is a gap in knowledge in the process by which cells alter their internal structure which then affect the interactions at the cellular surface. Our work focuses on investigating a colorectal cancer cell line, COLO205 which has surface expression of fucntional e-cadherin, but is defective in cell adhesion. This cell line can form some e-cadherin dependent aggregation over time (Aono 1999), but the associations are looser compared to treatments with drugs such as Src inhibitors which induce a tighter aggregate formation. Since cell contractility can be changed as a biomechanical response to environmental cues including hypoxia, stiffness of surrounding material and pH levels, we will be looking for changes in aggregation patterns by manipulating these variables.
Characterization of myelin deficits in rats with Alzheimer’s-like tauopathy
2: Visiting professor, Department of Pharmacology, Oxford University
Corresponding Author: Ai Liu, email ai.liu@mail.mcgill.ca
Abstract
Background: One hallmark of Alzheimer’s disease is abnormal tau accumulation, forming tangles inside neurons which coincide with neurodegeneration and cognitive dysfunction. It is also reported that myelin damage is common in dementia and may contribute to functional decline. However, there is no direct evidence on the relationship between tau pathology and demyelination. Therefore, our overarching goal is to evaluate whether and how a progressive tauopathy leads to myelin defects and relate to cognitive capabilities. Method: To explore the effects of a progressive tauopathy on myelin health, we will apply our newly generated McGill-R955-hTau transgenic rats, which expresses the longest form of human tau with the P301S mutation. To better correlate the effects of tauopathy-driven myelin defects with cognition, we will first characterize the cognitive function of McGill-R955-hTau heterozygotes and homozygotes transgenic rats at 12 months and 20 months in comparison to wild-type rats. For this we will apply behavior tests such as open field, novel object, Y-maze, social interaction, Morris water maze and fear conditioning. To elucidate the correlation of tau pathology and demyelination, we will examine region-specific alterations in myelination patterns and in oligodendrocyte marker expression profiles as well as the main features of human tauopathies and neurodegeneration. Conclusions: Homozygous McGill R955-hTau transgenic rats display age-dependent increases in human-specific tau immunoreactivity (HT7) and Phospho-Tau (AT8Ser202-Thr205). They also show cognitive impairments in specific behavior tests at 20 months of age which are more pronounced than in heterozygous rats. At 12 months of age, although tau hyperphosphorylation at Ser202/Thr205 is present, homozygous McGill R955-hTau transgenic rats do not show impairments in the tests applied. Analysis of myelination and oligodendrocyte markers is ongoing.
Characterizing the epigenome of melanoma subtypes to reveal insights into immune therapy response
2: Department of Human Genetics, McGill University, Montréal, Québec, Canada
3: Department of Biochemistry, McGill University, Montréal, Québec, Canada
4: Institute for the Advanced Study of Human Biology (WPI-ASHBi), Kyoto University, Kyoto, Japan
5: Canadian Center for Computational Genomics, McGill University, Montreal, Québec, Canada
6: McGill Genome Center, Montréal, Québec, Canada
Corresponding Author: Rong Ma, email rong.ma2@mail.mcgill.ca
Abstract
Melanocytes are found in the basal layer of the epidermis, but also reside throughout the human body, and are the cell of origin of melanomas. Therefore, melanomas arise most commonly in sun-exposed skin, but also in the uvea of the eye and mucosal membranes. A subtype called acral melanomas also develops in non-sun exposed skin such as the palms of the hands. Interestingly, melanomas from these various anatomical sites acquire different sets of driver mutations. Part of this melanoma-subtype specific accumulation of mutations may be due to differences in sun exposure of melanocytes, but may also be attributable to the cell of origin of melanocytes and their epigenetic states while residing in diverse microenvironments (e.g. skin, uvea, and mucosal membranes). Furthermore, cutaneous melanomas have high response rates to immune checkpoint inhibitors (ICIs), but responses are less common in mucosal and uveal melanomas. Although significant effort has been made in determining mutations that correlate with therapy resistance, few studies have examined the role of the epigenome in ICI response. To address whether different melanoma subtypes exhibit different epigenetic states, we performed a multi-omic analysis with epigenome (DNA methylome) and transcriptome profiling of 483 cutaneous, 113 uveal, 63 mucosal, and 49 acral melanomas. Specifically, we examined subtype-specific differences in DNA methylation and transposable elements (TEs) expression, a mechanism of viral mimicry linked to the immune response in other cancers. We observed uveal melanoma exhibited a completely different DNA methylation pattern compared to the other melanoma subtypes, whereby cutaneous, acral and mucosal melanomas were indistinguishable from each other. Furthermore, loss of epigenetic regulation leading to up-regulation of TEs (primarily LTR classes) was most commonly found in cutaneous melanomas and least in uveal melanomas which have the lowest ICI response rates amongst melanoma subtypes.
Lymphangiogenesis in cancer modulated by PTP-PRL2
2: Experimental Medicine Department, McGill University, Montreal, Canada
3: Biochemistry Department, McGill University, Montreal, Canada
4: Université de Bordeaux, Pessac, France
5: INSERM U1312 – BRIC, Pessac, France
6: INSERM U1297 – I2MC, Toulouse, France
Corresponding Author: Capucine Magaut, email rarahu.magaut@mail.mcgill.ca
Abstract
Lymphangiogenesis is the process of creating novel lymphatic vessels. These vessels are essential for tissue fluid homeostasis, immune cell trafficking, and dietary fat absorption. Lymphatic and blood vessels share similarities as the lymphatic vasculature takes its origin in veins. In recent collaborative work, we showed that the protein tyrosine phosphatase PRL2 (PTP-PRL2, PRL2, PTP4A2) modulates vascular development (Poulet M. et al., 2020). Based on the close relationship between these two types of vasculatures, we hypothesized that PRL2 would likely also play an essential function in forming lymphatic vessels. By functional assay, we demonstrate that silencing PRL2 in lymphatic endothelial cells (LECs) induces a drastic decrease in cell proliferation, migration, and sprouting. Further examination of this phenotype points to some critical signaling cascade modulated by PRL2. Under vascular endothelial growth factor (VEGF-A or VEGF-C) stimulation, ERK and Akt signaling pathways are affected by the absence of PRL2, decreasing and increasing phosphorylation respectively. Moreover, Notch1/DLL4 signaling pathway is also modified by a reduction of its signaling in these cells. We follow-up on the role of PRL2 since it is often upregulated in cancer, particularly within metastatic lymph nodes (Hardy S. et al., 2018), and we undertook in vivo experiments to determine if the absence of PRL2 expression in LECs could inhibit lymphangiogenesis, thus reduce metastasis in tumour-bearing mice. Our preliminary findings suggest that the known increase in PRL2 phosphatase in many cancers may contribute to the lymphatic vessels formation towards the tumor and potentially promote cancer metastasis. Further studies are ongoing to validate this hypothesis using mice with a specific PRL2 gene knock-out in LECs.
Understanding the role of eIF4E phosphorylation during breast cancer metastasis
2: Department of Biochemistry, McGill University
Corresponding Author: Niaz Mahmood, email niaz.mahmood@mail.mcgill.ca
Abstract
Despite the advancements in cancer treatments that improved clinical outcomes of patients with localized primary tumors, metastasis remains the most morbid aspect of breast cancer. Regulation of mRNA translation plays a crucial role in tumor progression, particularly during metastasis. The eukaryotic translation initiation factor 4E (eIF4E) functions as a rate-limiting factor for mRNA translation which encodes several key oncogenic and pro-metastatic proteins and thereby plays a crucial role in tumor progression. Importantly, phosphorylation of eIF4E at serine 209 (p-eIF4E) by the upstream MNK1/2 (MAPK (Mitogen-Activated Protein Kinase)-Interacting Kinase) is required to mediate the oncogenic activities within the tumors and its microenvironment. The p-eIF4E promotes mammary tumor metastasis to the lungs. However, the role of p-eIF4E in the extravasation and subsequent growth of breast tumor cells in the lung microenvironment is not fully understood. Herein, we have used an experimental lung metastasis model where mouse E0771 breast tumor cells were injected via tail-vein of wildtype (WT) and eIF4E S209A knock-in (KI) mice. We found that breast cancer lung colonization is significantly reduced in the KI mice compared to WT group, suggesting the involvement of p-eIF4E in the extravasation step of metastasis. Emerging evidence supports the role of metastasis-associated macrophages in breast tumor cell colonization to the lung. Several translationally regulated chemokines are involved in the recruitment of macrophages to the site of tumor growth. We will, therefore, determine the role of p-eIF4E in regulating tumor-macrophage interactions using various in vitro and in vivo approaches and the results will be presented and discussed. We anticipate that the results from this study will provide a better understanding of the role of p-eIF4E during metastasis extravasation that will help guide the development of new therapeutic strategies to target metastatic breast cancer.
Highly multiplexed imaging reveals the spatial immune landscape of highly and minimally invasive brain metastases
2: Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, QC, Canada
3: Department of Physiology, Faculty of Medicine, McGill University, Montreal, QC, Canada
4: Department of Human Genetics, Faculty of Medicine, McGill University, Montreal, QC, Canada
5: Departments of Psychology and Computer Science, University of Toronto, Toronto, ON, Canada
6: Medical Oncology Department, McGill University, Montreal, QC, Canada
7: Department of Diagnostic Radiology, Faculty of Medicine, McGill University, Montreal, QC, Canada
8: McGill University and Genome Quebec Innovation Centre, Montreal, QC, Canada
9: Department of Biochemistry, Faculty of Medicine, McGill University, Montreal, QC, Canada
10: Montreal Neurological Institute-Hospital, McGill University Health Centre, Montreal, QC, Canada
11: Department of Neurology and Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC, Canada
12: Department of Pathology, Faculty of Medicine, McGill University, Montreal, QC, Canada
13: Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, QC, Canada
Corresponding Author: Sarah Maritan, email sarah.maritan@mail.mcgill.ca
Abstract
Cancer metastasis to the brain is a common complication of advanced disease with limited therapeutic options. Inefficient treatment is influenced, in part, by the unique brain microenvironment. Brain metastases (BrM) grow in two distinct patterns, either as highly invasive (HI) or minimally invasive (MI) lesions. HI-BrM are associated with poor prognoses compared to MI-BrM; however, differences in the immune microenvironments between these two lesion types remain largely unknown. Here, we leverage single cell technologies with spatial resolution to assess the tumor immune microenvironment of HI and MI-BrM. We performed imaging mass cytometry on 119 BrM samples from 46 patients. Samples represent BrM from various primary sites, including cancers of the lung, breast, and skin. Analyzed tissues include patient-matched samples from the brain-tumor interface (‘margin’) or the centre of the metastatic lesion (‘core’). We performed single cell analysis of over 350,000 cells to identify 20 different cell lineages, activation states, and spatially-defined cellular neighbourhoods. HI-BrM were found to be characterized by abundant astrocytes at the margins, while MI-BrM displayed greater immune infiltration when compared to HI-BrM, both at margins and within cores. This was consistent with elevated interferon gamma signaling in the MI-BrM compared to HI-BrM, as detected by Nanostring Digital Spatial Profiling. Further, our imaging mass cytometry spatial analyses revealed 9 distinct cellular neighbourhoods (CNs). Tumor cores showed similar CN distribution across primary types, while margin samples revealed enrichment of macrophage-rich and vascular-niche CNs in melanoma BrM compared to lung or breast BrM. This study provides the first spatially-resolved single-cell dataset of the BrM microenvironment in MI and HI-BrM. The immune-rich microenvironment of MI versus HI-BrM suggests potential immune-regulation of BrM invasion, which warrants further investigation.
Battle for the Brain: Combatting Brain Tumor Progression with Glioma Inhibitory Macrophages
2: Division of Experimental Medicine, McGill University, Montreal, Canada
3: Department of Oncology, University of Calgary, Calgary, Canada
4: Gerald Bronfman Department of Oncology, McGill University, Montreal, Canada
Corresponding Author: Shyam Menon, email shyam.menon@mail.mcgill.ca
Abstract
Glioblastoma is one of the most aggressive human cancers that affects ~1,500 Canadians each year. Despite modern sophisticated treatment regimens, including surgery, chemotherapy, and radiotherapy, survival outcomes for these patients remains at a dismal 14.6 months. Of growing importance is the complex interaction between glioma cells and the plethora of cell types composing the tumor microenvironment. Previously, we found that the dual-function (secreted and nuclear) cytokine IL-33 is a key regulator of the inflammatory microenvironment that aids glioma tumorigenesis through phenotypic changes in the innate immune cell repertoire. Strikingly, when IL-33 is prevented from entering the nucleus, by deletion of its nuclear localization signal (ΔNLS IL-33), but is still secreted, tumor growth is dramatically suppressed through activation of a population of glioma-inhibitory macrophages (GIMs). Using spatial transcriptome profiling and multiplex immunohistochemistry with temporal resolution at different stages of tumor progression, we identified a unique transcriptome signature and cell surface markers of this novel innate immune cell population. Assessment of xenografts generated from patient brain tumor initiating cells found an enrichment of GIMs in xenografts with long-term survival (>300 days) compared to short-term survivors (<100 days). This prompted investigation into the ability of GIMs to inhibit glioma progression. By establishing tumors using a combination of ΔNLS IL-33 expressing cancer cells together with highly tumorigenic cells, we found that the growth inhibitory phenotype of ΔNLS IL-33 dominated the environment and significantly prolonged survival through the polarization and activation of GIMs. Further characterization of this phenotype and development of clinically relevant strategies to deliver ΔNLS IL-33 to the brain tumor microenvironment is necessary to determine if activation of GIMs is a translatable therapeutic strategy for glioma patients.
Targeting tumor-brain crosstalk in invasive spread of cancer in the brain
2: Experimental Medicine, Department of Medicine, McGill University
Corresponding Author: Caitlyn Mourcos, email caitlyn.mourcos@mail.mcgill.ca
Abstract
It is estimated that 20 to 40% of cancers will spread to the brain and develop into brain metastases (BrM). These tumors come with bleak prognoses for patients, but research efforts to investigate the biology of BrM and develop efficient and innovative therapeutic strategies are ongoing. Recent advances by our group discovered minimally (MI) and highly invasive(HI) BrM. Whereas MI BrM remain limited in area and are easier to surgically remove, HI BrM spread through the brain, and lead to post-resection recurrence in patients. Many studies have discovered that factors released from cancer cells and brain cells, such as growth factors and immune modulating factors (cytokines), can promote BrM progression. These factors can act as direct pro-invasion signals for cancer cells or alter the cellular landscape surrounding the metastases to promote growth of the lesion, for instance to escape an anti-tumor immune response. I am interested in identifying secreted factors from tumor cells and brain cells that drive the formation of HI BrM. This project is important as it will help uncover mediators of cancer-brain crosstalk, which may be exploited therapeutically for patients with HI BrM. This knowledge is crucial given the clinical availability of targeted growth-factorsignaling inhibitors and cancer immunotherapies that could disrupt this crosstalk. For instance, my initial investigation of melanoma BrM derived factors has already identified a growth factor enriched in HI BrM, which is known to promote cell growth and invasion. This factor can be blocked with existing targeted therapy, therefore further research will be important to confirm this factor’s role in HI BrM and determine whether targeting it could represent a promising treatment modality for certain HI BrM patients.
Deciphering the Role of Faciogenital Dysplasia 1 (FGD1) in Melanoma Progression
2: Department of Pathology & Oncology, McGill University, Lady Davis Institute, McGill University Health Center
Corresponding Author: Guy Namir, email guy.namir@mail.mcgill.ca
Abstract
Cutaneous melanoma is one of the most metastatic human cancers, and its incidence has increased faster than other types. In Canada in 2021, there were about 8,700 melanoma new cases and around 1,240 deaths, with a significant majority to men. Many studies have shown that sex is an independent predictor of patients' survival. Accumulating data suggests that melanoma may also be facilitated by X-linked genes, such as FGD1. FGD1, a Guanine nucleotide Exchange Factor, activates the GTPase Cdc42 that targets several downstream intracellular signaling pathways. Due to FGD1 involvement in cell cycle, cell morphology, motility, and extracellular matrix degradation, its amplification was found as related to several cancer types’ progression. However, the role of FGD1 during melanoma development remains unknown. We analyzed the mRNA FGD1 expression from 556 normal skin and 469 melanoma samples, using the GTEx, TCGA, and GSEA databases. We show higher levels of FGD1 in tumors compared to normal tissue. Additionally, ATAC-seq analysis shows that the FGD1 locus is more accessible in melanoma tumors compared to other cancer types, and has the potential to be translated to high protein levels. Moreover, we show a correlation between high FGD1 levels to poor patients’ survival rates. Furthermore, we show a contribution of high or low levels of FGD1 to proliferative or invasive transcriptional states respectively. We develop several human and mouse melanoma cell lines with different FGD1 levels, including CRISPR-Cas9 for FGD1 KO and Tet-On inducible system for FGD1 overexpression. These cell lines will provide insight into the effect and mechanism of FGD1 on several melanoma phenotypes, including proliferation, cell cycle, migration, and invasion. We will validate the findings using in vivo models and patients samples. By deciphering the role of FGD1 in melanoma progression, we may be able to identify new biomarkers and innovative treatments to treat melanoma.
Targeting GD2 and GD3 Gangliosides for Safe and Effective Cancer Immunotherapy that Synergizes with Immune-checkpoint Inhibition Blockade
2: Pharmacology and Therapeutics, McGill University
Corresponding Author: Ali Nejatie, email ali.nejatie@mail.mcgill.ca
Abstract
Introduction GD2 is a glycolipid tumor marker present on the cell membrane at high levels in ovarian cancer and melanoma, but essentially absent in normal tissues. GD2 provides cancer with growth advantages by direct activation of tyrosine kinases, and causes immunosuppression allowing the tumor to evade immunity. In spite of GD2 being an attractive target, it remains underexploited because it is very difficult to generate antibodies against it. In more than 40 years of research only one anti-GD2 mAb was FDA-approved, but which has very limited clinical benefits, and a low therapeutic index due to serious adverse side effects (e.g. pain and optic nerve neuropathy in mice and humans). We sought to develop novel anti-GD2 mAbs for immunotherapy. Methods Using chemical biology approaches (Tong et al, Cell Chemical Biology 2020) we generated 11 unique anti-GD2 mAbs. Two mAbs were evaluated for therapeutic efficacy in cancer models in vivo in immunocompetent mice. We used the EL4 syngeneic implanted tumor model, and the genetic mouse model with inducible BRAFV600E/PTEN-/-mutations. Results Two anti-GD2 mAbs, clone 4 and clone 17, are highly effective as monotherapy, for treating established tumors with a relatively low dose and frequency. The mAbs afford a significant reduction of primary tumor and metastatic nodes; a high therapeutic index without the side effects known to occur in mice with the FDA-approved mAb, and promote long-term survival. Conclusions Two anti-GD2 mAbs are promising new therapeutics in robust cancer models, and should be evaluated in ovarian cancer models as all human OVCA subtypes express GD2. Future work will address further optimization of the anti-GD2 mAb therapeutic paradigms as well as adjuvant or combination therapy.
The Role of LC3C in Cancer
2: Department of Experimental Medicine, McGill University
Corresponding Author: Annika Pedersen, email annika.pedersen@mail.mcgill.ca
Abstract
Cancer is the leading cause of death worldwide, and breast cancer is the second most common cancer in Canada. Despite improvements in cancer treatments and clinical outcomes, there remain many unknowns behind the mechanisms that allow these cancers to progress and spread. Autophagy, a cellular degradation pathway, is usually used to maintain normal cell function and growth but can assist or reduce the growth of tumour depending on the tumour type and tumour microenvironment. Different proteins in the autophagy pathway play a variety of roles that are still being characterized today. Our lab established that an autophagy protein called LC3C specifically targets the Met receptor protein for degradation. Met activation has been associated with poor prognosis in several cancers. When activated, Met can trigger cell invasion, so its targeting by LC3C inhibits Met-induced invasion. Furthermore, LC3C expression is decreased in several cancers, including breast cancer. Together, this suggests a tumour suppressive role for LC3C, but how LC3C is mediating this inhibition remains unknown. I hypothesize that LC3C decreases tumour progression and metastasis by inhibiting the process of cell invasion. I will be adding back LC3C into low LC3C expressing breast cancer cells that usually spread to see if this decreases cell invasion in mice and in cell assays. I will also decrease levels of LC3C in breast cancer cells that metastasize less to see if this increases metastasis. Additionally, I will explore how LC3C inhibits cell invasion by investigating new protein interaction candidates for interaction with LC3C and study the interactions using microscopy to determine the mechanism behind LC3C-induced tumour suppression. This work will provide novel insight into the role of LC3C in an anti-tumourigenic autophagy pathway, which could contribute to better stratifying cancer patients for autophagy inhibitor treatments that are currently being developed in clinical trials.
Investigating the role of CD13 in polarity initiation and alteration of polarity programs in breast cancer progression
2: Goodman Cancer Institute
3: Department of Medicine, Division of Experimental Medicine, McGill University
4: Department of Oncology, McGill University
Corresponding Author: Marie-Ève Proulx, email marie-eve.proulx2@mail.mcgill.ca
Abstract
Breast cancer represents 24.5% of new cancer cases diagnosed among women, making it the most diagnosed cancer in this group. Detection of pre-cancerous breast lesions is routine, however, there are no tests currently available to reliably predict which lesions are most likely to progress to breast cancer. It is estimated that fewer than half of precursor lesions will progress to breast cancer within 5 years, which has led to concerns of overtreatment in the clinic. Therefore, there is a need to better understand the mechanism underlying early breast cancer development to stratify precancerous lesion based on risk and improve health care for women. Polarized epithelial cells are organized to form hollow breast ducts. Disruption of this organization is a hallmark of progression to breast cancer. Our lab identified CD13 as a pioneer polarity factor required to establish apical-basal polarity. By immunostaining CD13 in patient samples from a spectrum of breast cancer stages we observed that CD13 is lost in a subset of cells in precursor lesions. Cell populations lacking CD13 were expanded to become the exclusive population in invasive cancer. We hypothesize that loss of CD13 causes disrupted polarity in breast cancer and its loss is associated with clonal expansion of malignant cells during tumor progression. As further evidence for a central role of CD13 in cancer progression, our preliminary data in oncogene-expressing 3D organotypic models show that CD13 over expression reverses the malignant phenotype, characterized by solid epithelial structures that lack a prominent lumen, and push the spheroid to a single layered polarized cyst. Finally, CD13 knockdown in mouse mammary organoids led to a loss of polarity and a disorganized epithelial organization characteristic of early breast lesions. This reveals a role for CD13 regulating cell polarity during breast cancer progression.
Identification of p-eIF4E as a new regulator of regulatory T-cell activity
2: Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
3: McGill Centre for Translational Research in Cancer, McGill University, Montreal, Quebec, Canada
Corresponding Author: François Santinon, email francoissantinon@gmail.com
Abstract
Phosphorylated Eukaryotic translation initiation factor 4E (p-eIF4E) is a critical regulator of protein synthesis and is phosphorylated on serine 209 by MNK1/2 to promote the translation of a subset of mRNAs. We have shown that blocking the eIF4E phosphorylation increased the anti-tumor immune response and especially the CD8 T-cells activation. However, the role of p-eIF4E in CD4 T-cell subsets, and in particular regulatory T cells (Tregs) is unknown. The aim of our study was to explore the impact that the absence of p-eIF4E could have on the Treg activity as well as in an inflammatory context. To investigate the role of p-eIF4E on Treg activity, we used two approaches, (1) genetically modified mice expressing a non-phosphorylatable form of eIF4E (KI mice) and (2) a MNK1/2 inhibitor. First, we analyzed Treg activity in WT and KI mice and the same mice subjected to dextran sulfate sodium (DSS)-induced colitis. We also analyzed the infiltration of colonic immune cells using spectral flow cytometry and CODEX technology. Using our mouse models, we observed that the absence of p-eIF4E led to a decrease in the Treg stability in vitro as well as a decrease in their ability to control the helper T-cells proliferation. We were able to reproduce these results by pre-treating WT Tregs with a MNK1/2 inhibitor. In the context of colitis, we observed an increase in the disease severity in KI mice compared to WT mice characterized by an increase in immune infiltration in the colon and in a worse colon disease severity histological score. Furthermore, our immunophenotyping of the colons and the mesenteric lymph nodes revealed a significant decrease in Treg among colonic T-cells, and an associated increase in helper T-cells expressing IFNγ in KI mice compared to WT mice. These results demonstrate for the first time the preponderant role of the MNK1/2-eIF4E axis in the Treg stability control and in its ability to regulate inflammation both in vitro and in vivo.
Identification of novel hepatic ERRa transcriptional partners
2: Departments of Biochemistry, Faculty of Medicine, McGill University, Montréal, QC, Canada
Corresponding Author: Charlotte Scholtes, email charlotte.scholtes@mcgill.ca
Abstract
ERRα plays a critical role in the regulation of cellular bioenergetics and metabolism, and perturbations in ERRα activity has been associated with the progression of non-alcoholic fatty liver disease (NAFLD) in mice. It is currently unknown whether the interactions and dynamic interplay between ERRα and its coactivators/corepressors are modulated by metabolic stressors, and whether the full complement of ERRα associated proteins on chromatin has been identified. We have used the powerful RIME (Rapid Immuno-precipitation Mass spectrometry of Endogenous proteins) approach to study the dynamic interactions of known ERRα interactors and identify novel new ERRα partners in mouse liver. Among these novel ERRα partners, we focused our attention on HCFC1 (Host cell factor C1), a ubiquitously expressed nuclear protein that associates with several chromatin modifiers to activate and/or repress transcription. Interestingly, liver specific HCFC1 knockout mice display a nonalcoholic steatohepatitis phenotype that is underpinned by mitochondrial dysfunctions, but the mechanisms underlying the role played by HCFC1 in the transcription of metabolic genes remain elusive. Herein, we highlight the functional relationship between ERRα and HCFC1 in the co-regulation of metabolic programs, most particularly on the expression of components of the respiratory chain and overall influence on mitochondrial function.
Identifying genetic vulnerabilities of chromosome 4p large copy number variants in triple negative breast cancer
2: Rosalind & Morris Goodman Cancer Institute, McGill University, Montreal, Canada
3: Centre for Applied Synthetic Biology, Concordia University, Montreal, Quebec
4: Department of Biology, Concordia University, Montreal, Quebec
5: McGill Genome Centre, McGill University, Montreal, Canada
6: Human Genetics Department, McGill University, Montreal, Canada
7: Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
8: Department of Human Genetics, McGill University, Montreal, QC, Canada.
Corresponding Author: Michael Schwartz, email michael.schwartz4@mail.mcgill.ca
Abstract
The basal-like breast cancer subtype often lacks biomarkers, such as hormone receptor expression and Her2 amplification (i.e., triple negative breast cancer, TNBC), which are therapeutically targetable. However, it exhibits recurrent large chromosomal deletions. It has been previously shown that chromosome 4p (chr4p) loss is a large copy number variant observed in over 60% of basal breast cancer cases. Here, we set out to investigate the genetic vulnerabilities associated with chr4p deletion in TNBC to understand the genetic mechanisms that maintain chr4p deletion in the genome. First, we leveraged the Cancer Cell Line Encyclopedia, as well as a Primary Tumor (PT)/ Patient-Derived Xenograft (PDX) panel to identify basal-like breast cancer cell models with chr4p deletion and copy-neutral status. A Gene-Set Enrichment Analysis demonstrated that chr4p deletion is associated with a global transcriptomic change involving differentially expressed genes annotated to oxidative phosphorylation and reduction/oxidation (redox) balance. We analyzed the DepMap’s genome-wide genetic screen data using established statistical models to identify negative and positive genetic interactions (GI) specific to chr4p deletion in basal breast cancer. These GIs were similarly enriched for oxidative phosphorylation, and redox balance pathways. Additionally, we analyzed pharmacological screen data from PRISM and identified chr4p-delete basal breast cancer cell lines to be more sensitive to treatment with drugs targeting antioxidant pathways. Lastly, we characterized chr4p-delete and -copy-neutral basal breast cancer cell lines using immunofluorescent staining of mitochondria to identify morphology changes associated with these oxidative metabolic signatures. Ultimately, this study provides a unique dataset for studying how large chromosomal deletions can be used as targetable biomarkers in TNBC, revealing potential novel therapeutic avenues for precision oncology.
CD36 as a Potential Novel Target in Metastasizing Aggressive Uveal Melanoma.
2: Lady Davis Institute for Medical Research
Corresponding Author: Heejin Hayley Shin, email heejin.shin@mail.mcgill.ca
Abstract
Uveal melanoma is the most common intra-ocular malignant cancer type in adults that occur in approximately 5 in every 1 million population. 50% of patients experience metastasis which occurs primarily to the liver quite early on from the onset of the disease. Unfortunately, from hereon, ~80% of patients die within the first year. There are also currently no standardized testing platform for diagnosis nor an effective therapy unlike the use of MEK inhibitors in cutaneous melanoma. Uveal melanoma has also been recognized as a highly heterogenous cancer type which has been studied to be the proposed mechanism underlying the ability of cancer cells to metastasize. Hence, we’ve developed a multi-coloured FACS panel composed of multiple classical cell state markers (Axl, CD36, CD166, NGFR, GFRA2, MelanA, GP100) in order to characterize 10 uveal melanoma cell lines derived from primary tumors or metastasized tumors from patients. Careful phenotyping of all cell lines with above mentioned markers gave us a broad spectrum of expression levels for each marker amongst the different cell lines. Particularly, CD36 was highly expressed in multiple cell lines along with moderate expression in some of the others. It is also a molecule that has been studied in other types of cancer such as Cervical Cancer and Glioblastoma Multiforme reporting to increase tumor burden as well as having a negative correlation with patient survival. Hence, we depleted CD36 in one of our cell lines and saw that this had affected the tumor cells’ ability to close a wound in a scratch assay, as well as reducing their ability to invade observed through a boyden-chamber invasion assay. From our data, CD36 appears to be a promising target and so we plan to study the effect of CD36 depletion in vivo where we would like to study the cells’ ability to travel and metastasize at the liver, their tumor burden, as well as the phenotypic differences in tumor cells that are able to metastasize vs those that cannot.
Characterizing the interactions between cancer derived EVs and neutrophil subsets and their impact on NETosis and triple negative breast cancer metastasis
2: Rosalind and Morris Goodman Cancer Research Centre, McGill University
3: Department of Biomedical Engineering, Faculty of Medicine and Health Sciences, McGill University
4: Department of Biochemistry, McGill University
5: Department of Medicine, Faculty of medicine and Health Sciences, McGill University
Corresponding Author: Emilie Solymoss, email emilie.solymoss@mail.mcgill.ca
Abstract
Breast cancer is the cancer with the highest incidence in women for which tumour metastasis remains a marker of poor prognosis particularly in triple negative breast cancer (TNBC) that has limited treatment options compared to other invasive cancer subtypes. Individually, cancer derived extracellular vesicles (EVs) as well as neutrophils and their release of neutrophil extracellular traps (NETs) have been shown to aid in cancer progression and metastasis. Our study aimed to characterize EV and neutrophil interactions by quantifying neutrophil uptake of EVs and the subsequent effects EVs had on NET release (NETosis) across two neutrophil subpopulations. Five cell lines were used in our study: non-transformed mouse mammary epithelial cells (NMuMG), non-metastatic (67NR) and metastatic 4T1 TNBC cell lines (parental (4T1-P), liver (2776), and lung (526) metastatic 4T1). EVs were isolated from conditioned media (CM) by ultracentrifugation and co-incubated with either immature low-density (iLDNs) or high-density neutrophils (HDNs) isolated from tumor-bearing Balb/c mice by density centrifugation. Subsequently, NETs were quantified by immunofluorescent staining. For both iLDNs and HDNs, the highest NETosis incidence was when the neutrophils were primed with EVs derived from the 4T1-P, 2776 and 526 metastatic cell lines. The tumorigenic but non-metastatic 67NR induced and intermediate NETosis response compared to the metastatic cell line derived EVs. In comparison, EV-depleted CM and EVs from non-tumorigenic NMuMG cells did not induce NETosis beyond background levels. Our findings suggest metastatic cancer derived EVs can promote NETosis to a greater extent than EVs from non-metastatic cells. This is of interest based on previous and emerging studies linking NETosis, specifically enhanced NETosis, the promotion of tumour growth and metastasis.
Inhibition of arginine methylation improves efficacy of cancer immunotherapy
2: Segal Cancer Center, Lady Davis Institute for Medical Research, Montréal, QC H3T 1E2, Canada; Gerald Bronfman Department of Oncology, McGill University, Montréal, QC H3A 1G5, Canada; Department of Medicine, McGill University, Montréal, QC H3A 1A1, Canada; Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
3: Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
4: Segal Cancer Center, Lady Davis Institute for Medical Research, Montréal, QC H3T 1E2, Canada; Department of Medicine, McGill University, Montréal, QC H3A 1A1, Canada.
5: Segal Cancer Center, Lady Davis Institute for Medical Research, Montréal, QC H3T 1E2, Canada; Gerald Bronfman Department of Oncology, McGill University, Montréal, QC H3A 1G5, Canada; Department of Medicine, McGill University, Montréal, QC H3A 1A1, Canada.
6: Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada.
7: Segal Cancer Center, Lady Davis Institute for Medical Research, Montréal, QC H3T 1E2, Canada; Gerald Bronfman Department of Oncology, McGill University, Montréal, QC H3A 1G5, Canada; Department of Medicine, McGill University, Montréal, QC H3A 1A1, Canada; Department of Human Genetics, McGill University, Montréal, QC H3A 0C7, Canada; Department of Biochemistry, McGill University, Montréal, QC H3A 1A3, Canada.
Corresponding Author: Nivine Srour, email nivine.srour@mail.mcgill.ca
Abstract
Tumor cells evade antitumoral immunosurveillance and this has led to development of immune checkpoint inhibitors (ICI). Despite the success of ICI therapy for cancer, resistance and relapse are frequent. Combination therapies are expected to enhance response rates and overcome this resistance. Herein, we report that combining protein arginine methyltransferase (PRMT7) inhibition with ICI therapy induces a strong anti-tumor T cell immunity and restrains tumor growth in vivo by increasing immune cell infiltration. Consistently, TCGA database analysis showed an inverse correlation between PRMT7 expression and T cell infiltration in human melanomas. PRMT7-deficient B16.F10 melanoma exhibits increased expression of genes in the interferon pathway, antigen presentation, and chemokine signaling. PRMT7 deficiency or inhibition with SGC3027 in B16.F10 melanoma results in reduced DNMT expression, loss of DNA methylation in the regulatory regions of endogenous retroviral elements (ERVs) causing their increased expression. Furthermore, PRMT7-deficient cells increase RIG-I and MDA5 expression with a reduction in the H4R3me2s repressive histone mark at their gene promoters. Our findings identify PRMT7 as a regulatory checkpoint for RIG-I, MDA5, and their ERV-double-stranded RNA (dsRNA) ligands, facilitating immune escape and anti-tumor T cell immunity to restrain tumor growth. Thus, targeting PRMT7 in tumor treatment should receive valuable and considerable attention.
Optimization and validation of novel mCARs for the treatment of leukemia
2: Institute of Research in Immunology and Cancer (IRIC), University of Montreal, CANADA
Corresponding Author: Margaux Tual , email margaux.tual@umontreal.ca
Abstract
Over the past 15 years, there has been an emergence of new therapies to treat cancer patients. One avenue of research focuses on harnessing the patient's T cells to eradicate tumors. To do so, T cells from a cancer patient are harvested and transduced to express a chimeric antigen receptor (CAR), capable of recognizing tumor cells, then reinfused into the patient to attack the cancer. CARs are synthetic proteins composed of a tumor cell targeting domain, a transmembrane domain, and a complex signaling domain to promote T cell mediated tumor cell lysis. These therapies are exceptionally effective in the treatment of young patients with leukemia and lymphoma. Nevertheless, complications arise due to defects in CAR signaling leading to aberrant immune responses. For this, the Gagnon lab has developed a new CAR architecture, which mimics the assembly and signaling efficiencies of the T cell receptor. These new modular CARs (mCARs) show better signaling efficacy and tumor cell killing compared to clinically approved CARs. The type of signals received by T cells have a critical impact on both functionality and longevity. The modular aspect of the mCAR allow us to quickly optimize all aspects of the signaling domain. Currently, we are optimizing mCARs previously developed in the lab and are benchmarking them to the clinically approved CARs in a clinically-relevant mouse tumor model which recapitulates clinical aspects of tumor progression in humans, including the complications observed in patients. This optimization will be done using a screen of signaling domains measuring tumor cell killing and T cell persistence. This first set of experiments will allow us to pick the best combination of signaling cues for mCAR to pursue characterization. Together, the findings made here will help determine the efficacy of the newly optimized mCARs in maintaining cell survival and functionality and set the framework for their clinical implementation to improve CAR T cell therapy.
Targeting obesity-associated monocytosis in CRC liver metastasis
2: Department of Experimental Medicine, McGill University
Corresponding Author: Ozgun Varol, email ozgun.varol@mail.mcgill.ca
Abstract
Introduction: Colorectal cancer (CRC) is the 3rd most diagnosed cancer in Canada, and the 2nd deadliest. Most CRC deaths are caused by liver metastasis, affecting ~90% of patients with stage IV disease. Obesity enhances CRC death by >40% in men, >30% in women, and affects ~24% of Canadians. Our lab has found that obesity promotes cancer metastasis through alterations in the myeloid compartment. We discovered that obesity-induced monocytes suppress cancer immune surveillance processes within the adaptive arm of the immune system, which enables CRC liver metastasis to thrive. Yet, how monocyte phenotypic changes are regulated by obesity, and their impact on CRCLM outgrowth, remain unknown. Aims and Methods: My project involves exploring local regulation of monocyte states within CRCLM lean vs obese hosts. Our lab has previously revealed that monocytes are metabolically and ontogenically distinct in the context of obesity. I will explore broad differences in the CRCLM immune compartment between lean and obese hosts using single cell RNA-sequencing; then focus on the myeloid fraction in more detail. Next, I will explore systematic regulation of monocyte development in lean vs obese hosts as it remains unknown whether enhanced myelopoiesis in obese hosts is reversible or epigenetically imprinted. Lastly, I will perform imaging mass cytometry on patient CRCLM samples to spatially characterize monocyte interactions within the tumor microenvironment. Conclusion: These results will uncover effects of obesity on the immune tumour microenvironment and translational relevance. Given the rising incidence of obesity, this project will bring invaluable implications for a substantial proportion of CRC patients where liver metastasis is common and therapeutic options remain limited.
The Function of BCL11B in Base Excision Repair Explains its Dual Role as an Oncogene and a Haplo-Insufficient Tumor Suppressor Gene
2: Department of Biochemistry, McGill University
3: Department of Medicine, McGill University
4: Department of Oncology, McGill University
5: Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto
6: Department of Molecular Genetics, University of Toronto, Toronto
7: Department of Biology, Université de Sherbrooke, Sherbrooke
Corresponding Author: Elise Vickridge, email elise.vickridge@mail.mcgill.ca
Abstract
Genetic studies in mice and human cancers established BCL11B as a haploinsufficient tumor suppressor gene. Paradoxically, BCL11B is overexpressed in some human cancers and BCL11B knockdown is synthetic lethal in T-cell lymphoma and glioblastoma cells. We identified the BCL11B protein in a proximity-dependent biotinylation screen performed with the DNA glycosylase NTHL1. In vitro DNA repair assays demonstrate that both BCL11B and a small recombinant BCL11B213-520 protein that is devoid of transcription regulation potential can stimulate the enzymatic activities of two base excision repair (BER) enzymes: NTHL1 and Pol β. In cells, BCL11B is rapidly recruited to sites of DNA damage caused by laser microirradiation. BCL11B knockdown delays, whereas ectopic expression of BCL11B213-520 accelerates, the repair of oxidative DNA damage. Inactivation of one BCL11B allele in TK6 lymphoblastoid cells causes an increase in spontaneous and radiation-induced mutation rates. In turn, ectopic expression of BCL11B213-520 cooperates with the RAS oncogene in cell transformation by reducing DNA damage and cellular senescence. Thus, BCL11B functions as a BER accessory factor that protects normal cells from the acquisition of mutations, but also enables the survival of cancer cells that would otherwise become senescent in response to oxidative DNA damage caused from the increased production of reactive oxygen species.
Inactivating hard-to-target tumorigenic transcription factors by SUMOylation: a proof of concept.
2: Département de biochimie et médecine moléculaire de l'Université de Montréal, UdeM
Corresponding Author: Anaïs Vivet, email anais.jeannine.irene.vivet@umontreal.ca
Abstract
The oestrogen receptor (ERα) detected in 70% of breast tumours is an oncogenic transcription factor (TF) that drives cancer cell survival and proliferation. Treatments to repress its activity are used clinically including anti-oestrogens: oestrogen analogues that compete for receptor binding but block its activity by different mechanisms. Whilst tamoxifen harbours partial agonist activity in other tissues than breast, fulvestrant defined as pure antioestrogen, provokes a greater global repression of ER-induced transcription. Fulvestrant induces SUMOylation of ERα, which involves the addition of SUMO peptides (Small Ubiquitin Like Modifiers). This causes chromatin closure and inhibits the transcription of proliferative genes induced by this TF. Data from the laboratory show that the E3 SUMO ligases PIAS1 and PIAS2 contribute to SUMOylation of ERα by fulvestrant. The overall negative impact of SUMOylation on TFs activity suggests that recruitment of the SUMOylation machinery to oncogenic TFs could lead to their inactivation. A proof of concept is needed to determine the potency of SUMOylation targeted TF inactivation. Our hypothesis aims to test if the recruitment of a SUMO E3 ligase activity to an oncogenic TF like ERα is sufficient to cause its SUMOylation and transcriptional inactivation. My preliminary results demonstrate that a ERα-PIAS1 chimeric protein is SUMOylated in the presence of oestrogen, is located within the nucleus, is transcriptionally inactive and can inhibit the activity of a non-fused receptor in transfected HEK293 cells. We will then test whether this fusion protein induces chromatin closure at target genes and degradation of the endogenous receptor in breast cancer cells. This project will test whether a directed SUMOylation strategy of oncogenic TFs represent a potential route for therapeutic inactivation of these factor and could be applicable to other oncogenic TFs for which SUMOylation has inactivating properties, such as Myc, c-Fos and Jun.
Studying the role of the G0S2 protein in lipid metabolism, inflammation, and colorectal cancer
2: Department of Biochemistry, McGill University
Corresponding Author: Yilin Wang, email yilin.wang4@mail.mcgill.ca
Abstract
Colorectal cancer is the third most common cancer worldwide as well as in Canada. Prior history of chronic intestinal inflammation is a major risk factor for CRC. For this reason, Inflammatory bowel disease (IBD) patients, who suffer from chronic inflammation of their gastrointestinal tracts, are at higher risk of developing colorectal cancer and die from it. Our lab has observed that the gene G0S2 (G0/G1 switch gene 2) is increased in IBD patients. The protein encoded by G0S2 has been shown to function as an inhibitor of lipid breakdown by binding to adipose triglyceride lipase (ATGL). We previously created mice in which the G0S2 was deleted and found G0S2 deleted mice are resistant to experimentally induced colitis and intestinal cancer. They displayed less pro-inflammatory cytokine production in the colon and bone marrow derived macrophages were also less pro-inflammatory. We have shown that G0S2 deletion results in increased ATGL activity. ATGL was recently shown to create palmitic acid esters of hydroxy stearic acids (PAHSAs, that are known to be potent inhibitors of inflammation). We hypothesize that G0S2 deletion causes increased PAHSA levels by promoting ATGL accelerated lipid breakdown, thus resulting in lower colon inflammation and colitis-associated tumour formation in colorectal cancer. A possible role of G0S2 in inflammation or immune system modulation has never been addressed experimentally in a physiological animal model in the content of intestinal inflammation and colorectal cancer. My research aims to use our G0S2 deleted mouse model to understand how altered lipid breakdown affects IBD and colorectal cancer on the molecular level, and elucidate the relationship between lipid metabolism, inflammation, and colorectal cancer. Our research in understanding the role of altered lipid metabolism may have implications in the development and treatment of inflammatory bowel disease and G0S2 could be a novel drug target for colorectal cancer treatment.
Oncogenic transformation promotes breast cancer onset by overcoming tissue-intrinsic anti-cancer barriers .
2: Department of Biochemistry, McGill University
3: Gerald Bronfman Department of Oncology, McGill University
Corresponding Author: Mara Whitford, email mara.whtiford@mail.mcgill.ca
Abstract
Breast cancer accounts for 15% of all cancer-related deaths in women. A hallmark of carcinoma development, including breast cancer, is loss of epithelial tissue architecture, whereby simple epithelial monolayers lose organization and become multilayered. Unfortunately, the mechanisms of tissue disorganization during early breast cancer development remain poorly understood. Improving our understanding of this process is critical to reliably predict progression, to better stratify patients and personalize care. To investigate the mechanisms by which oncogenes disrupt epithelial organization, I performed live confocal microscopy of 3-dimensional epithelial cysts. This allowed me to visualize cell division behaviour following the expression of oncogenes frequently expressed in human cancers (KRAS, ERBB2). While many control divisions occur within the epithelial plane, 20% of divisions occur out-of-plane, which can produce cells in a multilayered pattern at the end of cell division. Surprisingly, these divisions are rapidly corrected, and do not result in persistent disorganization of the epithelial layer. Conversely, expression of KRAS increases the proportion of out-of-plane divisions that occur, and impairs out-of-plane division resolution, to promote tissue disorganization. A novel mechanism of cell multilayering, which we have termed “apical budging”, is observed upon ERBB2 expression. The mitotic cell moves apically, followed by an in-plane division in front of its now basally located neighbouring cells. These results reveal that mechanisms of multilayering are oncogene dependent. Additionally, epithelial tissues can protect against multilayering by resolving out-of-plane divisions to maintain normal tissue architecture. The ability of KRAS to impede out-of-plane division resolution indicates that out-of-plane divisions per se may not be the primary mechanism driving tissue disorganization by this oncogene, but rather the ability to correct out-of-plane divisions.
Investigating the Metabolic Differences of Monocytes Derived from Obese and Lean Mice
2: Department of Microbiology and Immunology, McGill University, Qc, Canada.
3: Goodman Cancer Research Institute, Montreal, Qc, Canada.
4: Department of Human Genetics, McGill University, Qc, Canada.
5: Department of Medicine, Experimental Medicine, McGill University, Qc, Canada.
Corresponding Author: Liam Wilson, email liam.wilson@mail.mcgill.ca
Abstract
One of the leading modifiable risk factors for cancer mortality is obesity, largely resulting from enhanced metastasis. It has been recently discovered that obesity-stimulated monocytes contribute to enhanced lung metastasis in breast cancer due to their ability to stimulate neutrophil activation, which then mediates cancer cell transmigration across the vasculature. Interestingly, RNA-seq data obtained from obese and lean lung monocytes demonstrates differences in fatty acid uptake and mitochondrial trafficking of fatty acids. However, the functional impact of these transcriptional signatures on monocyte biology are unknown. The objective of my project is to functionally investigate the metabolic differences between monocytes derived from obese and lean mice. We hypothesize that there are differences in mitochondrial function and fatty acid uptake between obese- and lean-derived monocytes, echoing findings from transcriptomic analyses. Through palmitate substrate uptake assays performed with monocytes isolated from the bone marrow of obese versus lean mice, we have discovered that there are significant differences in palmitate uptake into these cells. To assess mitochondrial function, I will perform the XFe96 Seahorse MitoStress assay that I have optimized on bone marrow-derived monocytes from obese vs lean mice. These findings will support the RNA-seq data already obtained, demonstrating how the metabolism in monocytes differs between a state of obesity and of healthy weight.
TAOK3 limits sex and age-associated inflammation by negatively modulating macrophage differentiation and their production of TNFα
2: Department of Experimental Medicine, McGill University, Montréal, Québec, Canada.
3: Department of Microbiology and Immunology, McGill University, Montréal, Québec, Canada.
4: Department of Biochemistry, McGill University, Montréal, Québec, Canada.
5: Faculty of Medicine, McGill University, Montréal, Québec, Canada.
Corresponding Author: Chenyue Wu, email chenyue.wu2@mail.mcgill.ca
Abstract
Inflammaging, also known as age-related inflammation, is a state of chronic inflammation where the pro- and anti-inflammatory balance is disturbed. Macrophages have been found to be key players in age related inflammation, through their capacity to produce pro-inflammatory mediators but also by their importance in tissue homeostasis. TAOK3 is an important but poorly understood protein that plays an important role in the progression of chronic inflammation. Using cohorts of aged mice, we found that TAOK3 caused age-related skin lesions and accumulation of massive myeloid cells in the spleen in female, which are indications of severe inflammatory disease. Flow cytometry of the hematopoietic progenitor cells in the bone marrow revealed that Taok3-/- mice were biased towards myelopoiesis rather than lymphopoiesis. This progenitor skewage induced the accumulation of myeloid cells in the periphery and their production of pro-inflammatory mediators, such as CXCL9, IL-6 and TNFα. TAOK3 is also shown to impede monocyte migration following local inflammation. Ultimately, it was found that through its kinase domain, TAOK3 negatively regulates the differentiation of bone-marrow-derived-marcophages (BMDMs) and pro-inflammatory cytokine production. TAOK3 is thus a key enzyme that mitigates age-related inflammation.
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