PARP1 and ovarian cancer: Olaparib, as an oral PARP1/2 inhibitor, was the first FDA approved PARPi which is currently being used for treating individuals with ovarian cancers harboring germline BRCA1/BRCA2 mutations (Kim et al., 2015[19]), but metaplastic breast and ovarian cancer cells displayed intrinsic resistance to this drug (Vaidyanathan et al., 2016[37]).