Antiproliferative activity of the total saponin of Solanum lyratum Thunb in Hela cells by inducing apoptosis

Total saponin of Solanum lyratum Thunb (TSSLT), a species of natural biologically active substances isolated from Solanum lyratum Thunb, possesses various bioactivities. It has been proposed that the induction of Apoptosis may be the basis of its antitumor activity. However, the molecular mechanism underlying the total saponin-induced apoptotic process remains unknown. In the present study, we describe the anti-proliferative effect of TSSLT on human cervical Cancer cells (Hela). The TSSLT induced Apoptosis of Hela in a time-dependent manner with an IC50 for cell viability of 6 microg/ml. The TSSLT-induced cell death was characterized by changes in cell morphology, DNA fragmentation, activation of caspase-like activities, poly (ADP-ribose) polymerase (PARP) cleavage and release of cytochrome c (cyt c) into cytosol. TSSLT activated various caspases such as Caspase-3, -8, and -9 (like) activities but not Caspase-1 like activity. The cell death was completely prevented by the pan Caspase Inhibitor benzyloxy carbonyl-Val-Ala-Asp- fluoromethyl-ketone (Z-VAD-FMK). More than 80% cell survival was observed in the presence of a Caspase-3 inhibitor. In addition, treatment with TSSLT induced the increase of Bax:Bcl-2 ratio in Hela cells. These results suggest that the induction of Apoptosis by TSSLT involves multiple pathways antigen including death receptor and mitochondrial pathway and strongly suggest that the mitochondrial pathway was mediated by low expression of Bcl-2 and upregulation of Bax, release of cyt c and subsequent activation of Caspase-3 followed by down stream events leading to apoptotic cell death.