To empirically test whether olaparib can target ATM-deficient human cell lines, we used CRISPR/Cas9 to deplete ATM and DNA-PKcs from A549 cells, a human lung adenocarcinoma cell line, and used these cells to interrogate the mechanism by which lung adenocarcinoma cells respond to olaparib. The gene discussed is PRKDC; the disease is lung adenocarcinoma.