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.