Sequence specific effects on DNA and cell damage with the PARP inhibitor olaparib (AZD2281) and carboplatin

5025 Background: We have found clinical activity of carboplatin (C) with the PARP inhibitor olaparib (O) in BRCA1/2mut or BRCA-like breast and ovarian cancers. Current clinical trials are testing the hypothesis that PARP inhibition will sensitize tumors to platinum agents. We have examined sequence specificity of C and O combinations in cell lines, including two BRCA1mut (HCC1937, UWB1.289) and two BRCA-WT lines (OVCAR8, HeyA8), on the development of DNA damage and cell injury. Methods: Cell injury was measured with XTT assays. DNA damage was examined using Comet assay with tail quantification and γH2AX foci by immunofluorescence. Platinum DNA-adduct formation was measured using atomic absorption spectrometry and normalized to DNA input. Results: Exposure to O prior to C for 24 hours (O>C) reduced the efficiency of double stranded DNA damage compared to C alone or O+C (p C vs. C or O+C) measured by γH2AX foci/nucleus in BRCA1mut cell lines, UWB1.289: 11.0 (O>C), 40.9 (C), 46.4 (O+C); HCC1937: 1...