BRCA2 and pachyonychia congenita: It was observed that PARP1−/− mice did not develop early-onset malignancy, but BRCA2-deficient cells were sensitive to PARP inhibitors [15], so the rationale and application of adding PARP inhibitors such as olaparib to cause death of tumor cells especially with defective HRR capacity has been developed in treatment for cancers including PC [16].