PARP1 and cancer: In addition, Cai (87) found that the proline isomerase Pin1 can regulate BRCA1 and make cancer cells more sensitive to PARP inhibitors, which provided a new direction for drug development targeting BRCA. The deprivation of ERCC6L2, which is an additional NHEJ component, has also been shown to restore DNA end-resection, resulting in partial restoration of HR and resistance to PARP inhibitors in BRCA1-deficient cells (88).