LCK Regulates Homologous Recombination DNA Repair Identifying a New Target for Sensitizing PARP Inhibitors in HR Proficient Ovarian Cancer

Abstract

Poly-ADP Ribose Polymerase (PARP) inhibitors are clinically approved for the treatment of homologous recombination (HR) repair deficient tumors. PARP targeted therapy has limited efficacy in HR-proficient cancer. In this study, we identified the non-receptor lymphocyte-specific protein tyrosine kinase (LCK) as a novel regulator of HR repair pathways in endometrioid epithelial ovarian cancer (eEOC). Inhibition of LCK attenuates the expression of RAD51, BRCA1, and BRCA2 proteins necessary for HR-mediated DNA repair. HR repair in eEOC cells is LCK dependent. Upon DNA damage LCK expression is increased, and autophosphorylated, activated LCK is localized in the nucleus. LCK inhibition impairs RAD51 foci formation but augments gamma H2AX formation during DDR indicating reduced ability to repair DNA damage. DNA damage leads to direct interaction of LCK with RAD51 and BRCA1. Finally, attenuation of LCK sensitized HR-proficient eEOC cells to PARP inhibitor. Collectively, the findings identify a mechanism for expanding utility of PARP inhibitors.