PARP1 and cancer: Most notably, this approach led to the recent Food and Drug Administration (FDA) approval of PARP inhibition for metastatic breast cancer (11) and as maintenance therapy for ovarian cancers (12), for individuals with germline mutations in BRCA1 or BRCA2. Unlike the implicated role of PARP inhibition in facilitating cell death in cancer cells, new evidence is emerging in which PARP inhibition can enhance the response of immune checkpoint inhibitors (13, 14).