Smac peptide potentiates TRAIL- or paclitaxel-mediated ovarian cancer cell death in vitro and in vivo

: Second mitochondria-derived activator of caspases (Smac) is a recently identified protein that is released from mitochondria in response to apoptotic stimuli and promotes apoptosis by antagonizing the inhibitor of apoptosis proteins (IAPs). Our previous study showed that ectopic overexpression of Smac sensitizes drug-resistant tumor cells to TRAIL- or paclitaxel-induced apoptosis in vitro. The present study was designed to explore the effect of the synthesized Smac N7 peptide in a human ovarian cancer cell line and xenograft model. The results showed that the single-agent Smac N7 had a non-cytotoxic effect, but it effectively enhanced TRAIL- or paclitaxel-induced inhibition of cell proliferation in a dose-dependent manner, even in TRAIL-resistant A2780 cells. When Smac N7 was combined with TRAIL or paclitaxel in treating A2780 cell tumor xenografts, synergistic anticancer effects were achieved. Furthermore, the combination therapy caused less damage in normal tissues and more apoptosis in tumor xenografts compared with TRAIL or paclitaxel alone. Increased apoptosis was associated with the downregulation of XIAP, survivin and the increased activity of caspase-3, along with an increased amount of cleaved PARP. In conclusion, this Smac N7 peptide is a promising candidate for ovarian cancer combination therapy, and Smac may be the target for the development of a novel class of anticancer drugs.