Altered mRNA splicing dependent on mutant p53 identifies novel therapeutic vulnerability in pancreatic cancer

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PROJECT SUMMARY AND ABSTRACT CANDIDATE: I am a postdoctoral research fellow co-mentored by Drs. Steve Leach and Omar Abdel-Wahab at Memorial Sloan Kettering Cancer Center (MSKCC). I have research training background in population and molecular epidemiology, cancer predisposition, cancer biomarker discovery and validation, and molecular and cellular approaches to dissect signaling pathways in disease. My current research focuses on the role of mutant p53 and aberrant alternative splicing in pancreatic ductal adenocarcinoma (PDAC). My goal as an applicant of the K99 award is to pursue answers to the research questions where we hope to identify therapeutic opportunities for pancreatic cancer patients. My long-term goal is to become an independent investigator with the focus of uncovering the transcriptomic foundations of highly aggressive PDAC tumors dictated by well-known driver and unexplored mutations and expression of alternatively spliced variants. To reach this goal, my objectives are to broaden my familiarity and expertise with experimental approaches necessary for the experimental plan outlined in the research strategy, develop further autonomy in research, and recruit and train talented students. RESEARCH: Recent studies have identified PDAC patient molecular subtypes based on gene expression profiles, where the subtype with the worst survival outcome displays enrichment of 1) mutations in TP53, and 2) altered expression of genes encoding the RNA processing machinery. The overarching goal of this proposal is to determine how mutated p53 regulates and depends on specific patterns of alternative mRNA splicing for promotion, initiation, and maintenance of PDAC. My preliminary data shows that the most commonly mutated form of oncoprotein p53, R175H, preferentially promotes splicing of poly-C sequences cassette exon mRNAs, while repressing the inclusion of exons with poly-purine sequences. The poly-C sequences result in the expression of proline-rich, SH3 binding domains in protein isoforms of a class of regulators of small-GTPases, including Ras and Rho. These observations led to my hypothesis that p53R175H alters RNA splicing of GTPase regulators that drive transformation of KRAS-mutant PanIN, to promote PDAC pathogenesis, and presents a potential mechanism of cellular transformation. In addition, we have found that small- molecule inhibitors of the core RNA splicing factors significantly reduced tumor growth and extended the survival of PDAC mice expressing p53R172H, whereas no effect was seen in the absence p53R172H. This suggests that p53R175H’s dependence on regulating gene expression through control of AS may be a viable opportunity to therapeutically intervene and discover vulnerabilities for other p53 mutations in PDAC. ENVIRONMENT: MSKCC is an ideal place for me to perform the research outlined in this proposal and obtain the necessary training and knowledge to become an independent faculty member at a major university. First, I am being mentored by Dr. Leach, the director of the David M. Rubenstein Center for Pancreatic Cancer Research and an investigator recognized for his groundbreaking work on the molecular mechanisms regarding the biology of pancreatic cancer, pancreatic neoplasia and development. In addition, I’m being co-mentored by Dr. Abdel-Wahab, a junior physician-scientist expert in mRNA splicing regulation who has done important contributions by identifying molecular mechanisms of aberrant splicing in acute myeloid leukemia and myelodysplastic syndromes. I am convinced that this is the best environment for me to transition to becoming an independent investigator and training in areas required to become an expert in the fields of RNA and PDAC biology.