PARP1 and cancer: The effectiveness of PARP inhibitors can be examined in cancers that possess BRCAness gene defects. BRCAness can be described as tumors that do not have germline line BRCA mutation but have gene defects that share phenotypic similarities with BRCA mutations and have defective HRR. This review focuses mainly on the clinical trials of several PARP inhibitors to date and those currently underway to assess the efficacy of PARP inhibitors in the treatment of pancreatic cancer (Table 2) [30-32].