Effect of MAL on HNSCC cell apoptosis. (A) Sub-G1 apoptotic cells induced by ectopic expression of MAL in Tca cells transfected with pcDNA3.1-MAL vector were analyzed using PI staining and flow cytometry at different time points. Parental cells with an empty vector were used as a control. The lower histogram shows that exogenous MAL markedly induced apoptosis after transient transfection for 48 hours as compared with the control vector (P < 0.01). (B) To further observe the effect of MAL on cell apoptosis, after transient transfection for 72 hours, the cells were harvested and stained with 7-AAD and Annexin V-PE and then analyzed using flow cytometry. (C) Expression of cleaved PARP was assessed by Western blotting after transient transfection with pcDNA3.1-MAL and the empty vector for 48 hours and 72 hours.