Inhibition of DNA-PK was shown to resensitize BRCA2 deficient, PARPi resistant mammary tumor cells.58 In addition to NHEJ, microhomology-mediated end joining (MMEJ) is another important alternative DSB repair pathway that may facilitate resistance to PARPi.59 MMEJ is an error-prone mechanism that uses short regions of microhomology to align DNA ends, often resulting in deletions at the repair site. The gene discussed is PRKDC; the disease is breast cancer.