Cisplatin sensitivity and BRCA1 expression in the breast and ovarian cancer derived cell lines evaluated in this study. A) MTT cell viability assays comparing the responses of a panel of cell lines to 2 μg/ml cisplatin. Cell viability was assayed with the activity of untreated cells taken to be 100%. Values represent the mean +/- SEM of three separate experiments. B) Western blot analysis of basal expression levels of BRCA1 protein in a panel of cell lines. Actin was employed as a loading control. Numbers indicate protein densitometry readings with MCF7 used as the calibrator and set to 1.0. The experiment was repeated with similar results. C) Basal levels of BRCA1 mRNA analyzed by RT-PCR. Relative expression for each cell line was calculated following normalization to GAPDH levels and then further normalized to MCF-7 for ease of comparison and expressed as the mean +/- SEM of three separate experiments.