Biochemistry, Molecular & Cell Biology
Field Seminar

William Comstock
Smolka Lab

Monday, November 21, 2022
1:00 PM | 105 Riley-Robb Hall

“Deconvoluting Global Signaling Responses to Genotoxic Stresses”

For nearly a century, genotoxic drugs have been used in the treatment of cancer and other human diseases like sickle-cell anemia. Despite their extensive use in the clinic to this day, genotoxin-based monotherapies often prove ineffective and can display very poor selectivity toward cancer cells.The last decade has witnessed a revolution in the design of novel approaches based on synthetic lethality and combination therapy that explores the synergistic effects of targeting complementary pathways essential for cancer cell viability. However, despite this progress, use and design of novel combination therapies have been limited by an incomplete global understanding of how genotoxins impact cellular systems and their responses. Further advance of more effective combination therapies will heavily rely on accurate predictions of drug synergies and desirable phenotypic outcomes, which is only possible after achieving comprehensive understanding of the global cellular response involved. Here I developed and applied an in-depth phosphoproteomic approach to map and deconvolute the global signaling response to genotoxic drugs. Using the prototypical genotoxic chemotherapy camptothecin (CPT), a topoisomerase 1 inhibitor commonly used in the clinic, I show that a global analysis of CPT-induced phospho-signaling reveals hundreds of signaling events that are not attributable to canonical DNA damage sensor kinases. By using inhibitors of both the sensor kinase ATR and nucleases required for resection of double-stranded DNA breaks into ATR-activating recessed junctions, this global signaling network was able to be deconvoluted into subsets attributable to specific kinases that respond to specific forms of DNA damage. However, such deconvolution has also revealed novel non-canonical responses including resection-independent ATR signaling as well as hundreds of sites that cannot be attributed to any of the known DNA damage sensor kinases. Elucidating such global signaling events fills conspicuous gaps in our understanding of how cancer cells respond to these drugs, providing insight for future prediction of combinatorial outcomes in not only CPT-based therapies but for other genotoxic drugs as well.

Committee: Joseph Peters and Haiyuan Yu