RRR-α-tocopheryl succinate induces apoptosis in human gastric cancer cells via the NF-κB signaling pathway

To investigate the effects of the nuclear factor (NF)-kappa B signaling pathway on the induction of apoptosis by vitamin E succinate (RRR-alpha-tocopheryl succinate; YES) in human gastric carcinoma cells. Human gastric carcinoma SGC-7901 cells were treated with temperate concentrations of YES and pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappa B. Cell viability and apoptosis were respectively estimated by methylthiazol tetrazolium (MTT) assay and the Annexin V-FITC method. Western blot analysis was used to evaluate the protein expressions of NF-kappa Bp65 and Bcl-2 family members Bcl-2, Bax and cleavage of caspase-3, caspase-9, and poly (ADP-ribose) polymerase (PARP). The DNA-binding activity of NF-kappa Bp65 was measured by electrophoretic mobility shift assay (EMSA). Reverse transcription and polymerase chain reaction (RT-PCR) was implemented to evaluate the transcription of inhibitor of apoptosis (IAP) genes. Apoptosis assessment showed that YES induces apoptotic cell death in human gastric carcinoma cells. In the following experiments, PDTC (100 mu M) was used in cell treatment 2 h before YES. The decreased ratio of the nuclear and cytosolic NF-kappa Bp65 protein level was induced by YES and PDTC reinforced this trend. PDTC treatment significantly enhanced the decrease of NF-kappa B-DNA binding activity induced by YES in human gastric SGC-7901. The decrease in protein expression of Bcl-2 as well as the increase in the protein expression of Bax were induced by YES treatment. The cleavage of caspase-9, caspase-3 and PARP was induced. There was no effect on the gene transcription of c-IAP-1, c-IAP-2, and x-linked IAP (XIAP) compared with the control group, whereas mRNA levels of survivin and the neuronal apoptosis inhibitory protein (NAIP) markedly decreased. Notably, pretreatment with PDTC reinforced all the above YES-induced effects. In conclusion, YES-induced apoptosis in SGC-7901 cells is accompanied by the inhibition of the NF-kappa B signaling pathway, including changes in Bcl-2 family members, cleavage of caspases and gene transcription of survivin and NAIP.