Antiproliferative Activity and Induction of Apoptosis in Human Melanoma Cells by Houttuynia cordata Thunb Extract

Background/Aim: To analyze the apoptotic effect of Houttuynia cordata Thunb (HCT) extract on human melanoma A375 cells and its underlying mechanisms. Materials and Methods: The effects of HCT on cell death were determined using the MTT assay. Hoechst 33342 staining was conducted to confirm the detection of cell apoptosis. Caspase-3 and caspase-8 mRNA and cleaved protein levels were investigated by RT-PCR and western blotting, respectively. The release of high mobility group box 1 (HMGB1) and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by ELISA. Results: Caspase-3 and caspase-8 specific inhibitors suppressed HCT-induced cell death. HCT increased caspase-3 and caspase-8 mRNA, protein levels, and caspase activities in a concentration- and time-dependent manner. HCT induced MAPK phosphorylation in a time-dependent fashion. Pretreatment of cells with a selective inhibitor of p38 MAPK reduced apoptosis and reversed the levels of HMGB1 release in response to HCT treatment. Conclusion: HCT induces A375 programmed cell death by activating the caspase-dependent pathway and by p38 phosphorylation associated with HMGB1 reduction.