EXPLORING THE ROLE OF GENETIC MODIFIERS IN DNA REPAIR AND BREAST CANCER

Training PlanWith the influx and refinement of new high-throughput technologies in this post-genome age, the paradigm for cancer genetics research is constantly being rewritten, and new iterations favor an unprecedented level of synergy between the lab bench and the computing cluster. My prior background in physics and astronomy helped me to build a broad set of mathematical and computational skills that provide a highly unique complement to my current training in molecular genetics. Upon completion of the proposed training program at the Fred Hutchinson Cancer Research Center, I will be expertly trained to perform highly interdisciplinary breast cancer research. I believe this will allow me to innovate as a cancer biologist in this new era, and my long-term goal is to profoundly contribute to the early detection of breast cancer by advancing our understanding of the genetics underlying tumorigenesis.Research PlanBackground: If we could identify major genetic factors that contribute to breast cancer risk, we would be able to provide comprehensive early identification of individuals at risk and tailor prevention and treatment regimens. This is an extremely difficult problem since although rare breast cancers arise in the setting of monogenic syndromes (e.g., BRCA1), heritable risk for common forms of breast cancer is a result of multiple gene-gene interactions, which are extraordinarily difficult to identify. Our specific approach is based on the observation that defects in the cellular DNA damage response (an intermediate phenotype for breast cancer susceptibility) are heritable, making it possible to characterize and map gene-gene interactions responsible for this phenotype.Objective: We hypothesize that gene-gene interactions governing sensitivity to DNA damage are conserved between yeast and humans and are excellent candidates for breast cancer susceptibility genes. Our laboratory has developed a rapid screening approach for identifying novel low penetrance breast cancer susceptibility alleles that leverages the model system S. cerevisiae for genome-wide screening and uses sensitivity to DNA damaging agents as an intermediate phenotype for cancer susceptibility.Specific Aims: Our approach will be to use the yeast S. cerevisiae to perform genome-wide screens for mutations that synergize with homologs of human breast cancer tumor suppressor genes to confer sensitivity to DNA damage (Aim 1). In Aim 2, we will characterize functional consequences of each double-deletion candidate, which may explain synthetic sensitivity to DNA damaging agents. In Aim 3, we will screen (using computational biology and functional genomics) among these identified synthetic interactions for those that are conserved in human mammary epithelial cells and are predicted to contribute to cancer susceptibility.Study Design: We will create a tel1(delta) (tumor suppressor ATM homolog)-based double deletion library in S. cerevisiae and screen for double-mutants that yield synthetic sensitivity to DNA damaging agents. Identified candidates will be characterized for their involvement in DNA repair by a number of methods, including mutation and recombination rate assays. We will implement an integrative genomic approach to identify the subset of yeast candidates that are most likely to have functional importance in human breast cancer and will test for conservation of high priority gene-gene interactions in human mammary epithelial cells by performing double knockdowns of human homologs using siRNA, and screening for sensitivity to DNA damaging agents.Impact: The proposed project will provide excellent training in both laboratory and computational methods for exploring the molecular genetics of DNA repair and breast cancer. With this screen, we seek to identify new breast cancer susceptibility alleles, which may result in new targets for drug development and may have an immediate and profound impact on cancer screening.