CDK9 is co-expressed with BRCA1 in ovarian cancer. A. The correlation between CDK9 and BRCA1 protein expression in ovarian cancer patients retrieved from the TCGA dataset was investigated by GEPIA (gene expression profiling interactive analysis, http://gepia.cancer-pku.cn). B. The expression of BRCA1 and CDK9 proteins in six ovarian cancer cell lines, HO8910, OVCAR-5, SKOV3, A2780, OVCAR-8, and OVCA433, as determined by Western blot analysis. C, D. The cytotoxic effects of olaparib (C) and CDKI-73 (D) at various concentrations on the six ovarian cancer cells for 48 hr were measured with the CCK-8 assay. E. IC50 values of the above cells were calculated using GraphPad Prism software.