Combination effect of nelfinavir and tamoxifen on the cell survival of breast cancer cells. (a) A total of 5 × 103 MCF7 and T47 D cells per well were seeded in quadruplicate in 96-well cell culture plates, incubated with the indicated nelfinavir and tamoxifen (TAM) concentrations either alone or in combination, and were analysed for cell viability by an MTT assay after 72 hours of incubation. (b) A similar experiment was performed using different nelfinavir and TAM concentrations, and MTT-derived staining intensities were analysed by a photometer (shown as bar graphs). Values represent the mean ± standard deviation. Significance assumed at P < 0.05 with the nonparametric Wilcoxon rank-sum test.