SmacN7 enhances the sensitivity of pancreatic cancer cells to tumor necrosis factor-related apoptosis-inducing ligand or gemcitabine.

The aim of this study was to investigate the effect of SmacN7 on the biological characteristics of pancreatic cancer cell lines, and to assess the effect of SmacN7 on the sensitivity to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and gemcitabine. SmacN7 fusion polypeptide was synthesized and characterized using mass spectrometry. The morphology of apoptotic SW1990 cells and apoptotic rates were observed after 24 h of SmacN7 treatment, and the changes of cell growth inhibition rate were investigated following treatment with different concentrations of SmacN7. The combined effects of SmacN7 and different concentrations of TRAIL or gemcitabine for 24 h on the apoptotic rates of SW1990 cells were assessed, and the changes of expression of apoptosis-related proteins including X-linked inhibitor of apoptosis protein (XIAP), cytochrome C and caspase-3 were determined. Mass spectrometric identification of SmacN7 was fully consistent with the expected results. The cell growth inhibition rates of SW1990 cells 24 h post-treatment with TRAIL at different concentrations were 18.11, 37.67, 42.63 and 67.6%, in comparison to 17.65, 31.85, 40.11 and 74.99% following combined treatment of SmacN7 and different concentrations of gemcitabine for 24 h. The combined treatment of SmacN7 and gemcitabine for 24 h resulted in significantly elevated expression of cytochrome C and caspase-3 cleavage fragment, p17, and a significant reduction in XIAP expression (P<0.05). SmacN7 inhibits pancreatic cell growth. The inhibition rates of SW1990 cells caused by treatment with various concentrations of SmacN7 appear in a time- and concentration-dependent manner. The TRAIL- or gemcitabine-induced apoptosis of pancreatic cancer cells, enhanced by SmacN7, may be associated with the activity of intracellular pro-apoptotic proteins such as Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP binding protein with low PI), cytochrome C, XIAP and caspase-3.