Abstract PR01: A functional variomic chemi-genetic screen in C. elegans identifies new synthetic lethal interactions with PARP inhibition that are conserved from worm to human

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Abstract Poly ADP-ribose polymerase (PARP) inhibitors are anti-cancer therapeutics that are synthetic lethal (SL) with mutations affecting the homologous recombination genes BRCA1 or BRCA2. Previous work from our lab found that cohesin mutations, which are common in a range of tumour types, also confer sensitivity to PARP inhibition. We want to extend the SL profile of PARP inhibitors to identify the full spectrum of genetic variants that result in sensitivity to PARP inhibitors alone or in combination with DNA damaging agents. To this end, we are using the model organism Caenorhabditis elegans to screen for new SL interactions with PARP inhibitors. C. elegans provides an excellent in vivo system with which to investigate SL interactions with cancer-associated mutations, as many of the pathways and genes implicated in cancer are conserved between humans and C. elegans. In many ways, C. elegans is an animal model that combines the technical advantages of a single celled organism, such as yeast, with increased developmental complexity and a gene complement more akin to humans. We have developed a high throughput in vivo variomics approach using the C. elegans Million Mutation Project strain collection to screen 2,000 mutagenized and sequenced strains containing >800,000 homozygous genetic variations. To date we have found 16 strains that were sensitive to the PARP inhibitor olaparib. Frequency analysis of the variants in the sensitive strains identified multiple mutations affecting mus-81 and eme-1, which comprise the structure specific Mus81 endonuclease. Further investigation of the interaction with the Mus81 endonuclease mutants found that PARP inhibitor-treated mus-81 and eme-1 mutants exhibit profound somatic proliferation defects characterized by persistent anaphase bridges and that the mus-81 PARP inhibitor-mediated synthetic lethality was not suppressed by loss of non-homologous end joining proteins. We found that the synthetic lethality between MUS81 mutations and PARP inhibitor treatment is conserved in human cells. Similar to C. elegans, PARP inhibitor treated MUS81 knockout cells accumulate anaphase bridges and exhibit a phenotype distinct from PARP inhibitor treated BRCA2 knockout cells. Our variomic screening approach has identified new SL interactions with PARP inhibitors and has expanded our understanding of the mechanism underlying PARP inhibitor-mediated synthetic lethality. Citation Format: Nigel J. O’Neil, Melanie L. Bailey, Philip Hieter. A functional variomic chemi-genetic screen in C. elegans identifies new synthetic lethal interactions with PARP inhibition that are conserved from worm to human [abstract]. In: Proceedings of the AACR Precision Medicine Series: Opportunities and Challenges of Exploiting Synthetic Lethality in Cancer; Jan 4-7, 2017; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2017;16(10 Suppl):Abstract nr PR01.