Anti-tumor activity of CrTX in human lung adeno- carcinoma 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 μg/mL） for 48 h significantly inhibited the cell growth in a dose-dependent manner （IC50=78 μg/mL）. Treatment with CrTX （25 μg/mL） for 24 h caused G1 arrest and induced cell apoptosis. CrTX （25 μg/mL） significantly increased the expression of wt p53, cleaved caspase-3 and phospho-P38MAPK. Pretreatment with the specific P38MAPK inhibitor SB203580 （5 μmol/L） significantly reduced CrTX-induced apoptosis and cleaved caspase-3 level, but G1 arrest remained unchanged and highly expressed p53 sustained. Intraperitoneal injection of CrTX （10 μg/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.