Olaparib would act against BRCA1 or BRCA2 mutations. AZD2281 is not sensitive to tankyrase-1 with IC50 more than 1 μM. Olaparib could ablate the PARP-1 activity at concentrations of 30-100 nM in SW620 cell. Olaparib is hypersensitive to BRCA1-deficient cell lines (MDA-MB-463 and HCC1937), compared with BRCA1- and BRCA2-proficient cell lines (Hs578T, MDA-MB-231, and T47D).  Olaparib is strongly sensitive to KB2P cells due to suppression of base excision repair by PARP inhibition, which may result in the conversion of single-strand breaks to double-strand breaks during DNA replication, thus activating BRCA2-dependent recombination pathways.