Pan-caspase inhibitor z-VAD-fmk alleviates SCRT-induced apoptosis in A549 cells. (A) Cells were incubated with 1.5 mg/ml of SCRT for 72 h after 1 h pretreatment with z-VAD-fmk (50 μM). After staining with DAPI solution, the nuclei were observed under a fluorescent microscope (original magnification 400x). (B) The genomic DNA from cells was extracted, separated by agarose gel electrophoresis, and visualized under UV light after staining with EtBr. (C) The percentages of apoptotic cells (annexin V+ cells) were analyzed using flow cytometric analysis. The data is the mean of the two different experiments. (D) Cell viability was determined by MTT assays. Each point represents the mean ± SD of three independent experiments. The significance was determined using Student’s t-test (*p < 0.05 vs. untreated control; #p < 0.05 vs. SCRT-treated cells).