Induction of apoptosis in A431 cells by GBT. (A) The observation of DNA laddering induced by GBT using the DNA fragmentation assay for 12 and 24 h, respectively. (B) Activation of caspase-3 in GBT-induced apoptosis for 24 h. Results are representative of three independent experiments. *P<0.05 and **P<0.01 versus untreated control cells. (C) The effect of GBT on the expression of pro-apoptotic proteins in A431 cells for 24 h. Band intensity compared to untreated cells was calculated using ImageJ after normalization to β-actin expression. The data represent two independent experiments. (D) The investigation of apoptotic effect of GBT for 24 h using the caspases inhibitor study. Cells were pretreated with the caspase inhibitors Z-VAD-fmk (general), Z-DEVD-fmk (caspase-3), Z-IETD-fmk (caspase-8), and Z-LEHD-fmk (caspase-9) (all at a concentration of 10 μM) for 30 min. Cell viability was determined by MTT assay, and the results are shown as the means ± SD of two independent triplicate experiments. **
P<0.01 versus untreated control cells; #
P<0.05 and ##
P<0.01 versus cells treated with GBT only.