CRISPR/Cas9-induced saturated mutagenesis identifies Rad51 haplotype as a marker of PARP inhibitor sensitivity in breast cancer

Breast cancer treatment with poly(ADP-ribose)polymerase (PARP) inhibitors is currently limited to cells defective in the homologous recombination repair (HRR) pathway. The chemical inhibition of many HRR deficiency genes may sensitize cancer cells to PARP inhibitors. In the present study, Rad51, a central player in the HRR pathway, was selected to explore additional low variation and highly representative markers for PARP inhibitor activity. A CRISPR/Cas9-based saturated mutation approach for the Rad51 WALKER domain was used to evaluate the sensitivity of the PARP inhibitor olaparib. Five amino acid mutation sites were identified in olaparib-resistant cells. Two Rad51 haplotypes were assembled from the mutations, and may represent useful pharmacogenomic markers of PARP inhibitor sensitivity.