Anti-tumor activity of CrTX in human lung adenocarcinoma cell line A549

Aim: To assess the cytotoxic effect of crotoxin (CrTX), a potent neurotoxin extracted from the venom of the pit viper Crotalus durissus terrificus, in human lung adenocarcinoma A549 cells and investigated the underlying mechanisms. Methods: A549 cells were treated with gradient concentrations of CrTX, and the cell cycle and apoptosis were analyzed using a flow cytometric assay. The changes of cellular effectors p53, caspase-3 and cleaved caspase-3, total P38MAPK and pP38MAPK were investigated using Western blot assays. A549 xenograft model was used to examine the inhibition of CrTX on tumor growth in vivo. Results: Treatment of A549 cells with CrTX (25-200 mu g/mL) for 48 h significantly inhibited the cell growth in a dose-dependent manner (IC(50)=78 mu g/mL). Treatment with CrTX (25 mu g/mL) for 24 h caused G1 arrest and induced cell apoptosis. CrTX (25 mu g/mL) significantly increased the expression of wt p53, cleaved caspase-3 and phospho-P38MAPK. Pretreatment with the specific P38MAPK inhibitor SB203580 (5 mu mol/L) significantly reduced CrTX-induced apoptosis and cleaved caspase-3 level, but G(1) arrest remained unchanged and highly expressed p53 sustained. Intraperitoneal injection of CrTX (10 mu g/kg, twice a week for 4 weeks) significantly inhibited A549 tumor xenograft growth, and decreased MVD and VEGF levels. Conclusion: CrTX produced significant anti-tumor effects by inducing cell apoptosis probably due to activation of P38MAPK and caspase-3, and by cell cycle arrest mediated by increased wt p53 expression. In addition, CrTX displayed anti-angiogenic effects in vivo.