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Amitzi, Leanne

University of British Columbia

Genotype-driven therapies are a new paradigm for cancer treatment. These approaches rely on identification of genetic vulnerabilities and genotype-linked therapeutic agents. One approach utilizes synthetic lethality (SL), which occurs when disruption of two gene products individually is non-lethal, but simultaneous disruption of both gene products results in lethality. A synthetic lethal target identified in our lab is the helicase DDX11, the human homolog of yeast CHL1. In yeast, CHL1 is a highly-connected synthetic lethal hub, that genetically interacts with many genes involved in processes often defective in tumours, such as sister-chromatid cohesion (SCC) and replication fork stability, and as such, would make a good synthetic lethal therapeutic target. The overarching goal of this research is to advance development of DDX11 inhibition as a synthetic lethal therapeutic. Previous work in our lab identified a genetic interaction between cohesin mutations and CHL1 in yeast. We first directly tested a potential genetic interaction between DDX11 and the cancer-mutated cohesin gene STAG2 in human cell lines and found that it did not result in synthetic lethality. We then conducted an unbiased screen for DDX11 genetic interactions in human cells and identified many genes involved in SCC, supporting the conserved role of DDX11, as well as supporting DDX11 inhibition as a potential SL-based therapy for tumours with cohesion defects. To date, only one SL-based drug has reached the clinic, PARP inhibitors, which trap PARP on the DNA creating a cytotoxic complex. Small molecule-induced trapping may represent a generalized mechanism for clinically relevant synthetic lethal interactions. We hypothesized that missense mutations that model such inhibitors can be utilized as an alternative to knock-out/knock-down based screens. As a proof-of principle, we expressed missense mutations in CHL1 that inhibited enzymatic activity but retained substrate binding, and found that these mutations elicited a dominant synthetic lethal phenotype consistent with the generation of cytotoxic intermediates. These results point to the utility of modeling trapping mutations in pursuit of more clinically relevant synthetic lethal interactions. Finally, we developed a biochemical method for high-throughput screening for DDX11 inhibitors. Together, this work contributes to the development of DDX11 inhibition as an anti-cancer therapeutic.

Text

2022-11-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/80155

Medical Genetics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/