PDF file - 3250K, Figure S1 Olaparib has variable levels of anti-tumor activity in human cancer cell lines. Figure S2 Olaparib sensitive cell lines have different patterns of gene expression compared to insensitive cell lines. Figure S3 PTEN expression does not affect olaparib sensitivity. Figure S4 RAD51C expression affects olaparib sensitivity in human cancer cell lines. Figure S5 RAD51C over-expression decreases sensitivity to olaparib in the BT-549 cell line. Figure S6 Olaparib induces G2/M cell cycle arrest and apoptosis in sensitive cell lines. Figure S7 RAD51C depletion increases the accumulation of DNA damage. Figure S8 RAD51C expression decreases in tumor tissues. Figure S9 RAD51C expression is down-regulated in gastric tumor tissues via DNA methylation. Table S1. Sequences of the primers for PCR and real-time PCR analyses. Table S2. BRCA1 and BRCA2 mutations in the gastric cancer cell lines.
ARTICLE ABSTRACT
A PARP inhibitor is a rationally designed targeted therapy for cancers with impaired DNA repair abilities. RAD51C is a paralog of RAD51 that has an important role in the DNA damage response. We found that cell lines sensitive to a novel oral PARP inhibitor, olaparib, had low levels of RAD51C expression using microarray analysis, and we therefore hypothesized that low expression of RAD51C may hamper the DNA repair process, resulting in increased sensitivity to olaparib. Compared with the cells with normal RAD51C expression levels, RAD51C-deficient cancer cells were more sensitive to olaparib, and a higher proportion underwent cell death by inducing G2–M cell-cycle arrest and apoptosis. The restoration of RAD51C in a sensitive cell line caused attenuation of olaparib sensitivity. In contrast, silencing of RAD51C in a resistant cell line enhanced the sensitivity to olaparib, and the number of RAD51 foci decreased with ablated RAD51C expression. We also found the expression of RAD51C was downregulated in cancer cells due to epigenetic changes and RAD51C expression was low in some gastric cancer tissues. Furthermore, olaparib significantly suppressed RAD51C-deficient tumor growth in a xenograft model. In summary, RAD51C-deficient cancer cells are highly sensitive to olaparib and offer preclinical proof-of-principle that RAD51C deficiency may be considered a biomarker for predicting the antitumor effects of olaparib. Mol Cancer Ther; 12(6); 865–77. ©2013 AACR.
