4OHT enhances TMCG/DIPY toxicity in MDA-MB-231 cells. In all cases, the cells were treated for 3 days with vehicle (control); 1 μM 4OHT; 10 μM TMCG and 5 μM DIPY (TMCG/DIPY); or 10 μM TMCG, 5 μM DIPY, and 1 μM 4OHT (TMCG/DIPY/4OHT). (A) The images show the effect of the 4OHT, TMCG/DIPY and TMCG/DIPY/4OHT treatments on the morphology (upper panels) and apoptosis (lower panels) of MDA-MB-231 cells as determined by bright-field microscopy and fluorescence microscopy after DNA staining with Hoechst 33342. The histograms represent the percentage of viable and apoptotic cells calculated from the images shown above. *P < 0.05 compared to the untreated controls; **P < 0.05 compared to TMCG/DIPY-treated cells. (B) Semiquantitative determination of p73 and Apaf1 mRNAs in MDA-MB-231 after different treatments. The estimated relative levels of the specific mRNA with respect to that of β-actin mRNA were calculated and then compared with respect to the expression levels in untreated controls. *P < 0.05 compared to the untreated controls.