Fig. 6. Combination of tamoxifen and gefitinib synergistically induces apoptosis in in vitro. (A, B) After 24 h serum starvation, we treated cells with or without 10 mM 4-OHT and/or gefitinib for 4 h. (A) Cell viability was analyzed by MTT assays. (B) Levels of PARP-1 and procaspase-3 protein were detected by western blots. (C) Cells were treated with or without 10 mM 4-OHT and/or gefitinib in agarose plates for colony-forming assays. Values are mean ± SEM. * P<0.05, ** P<0.01 vs. (-) control.