Investigation the mechanism of the apoptosis induced by lactacystin in gastric cancer cells.

The study aims to investigate the relationship between nuclear factor (nuclear factor kappa B (NF-κB)) viability and lactacystin-mediated cell apoptosis in gastric cancer cells. Two gastric cancer cell lines (MKN28 and SGC7901) were treated with lactacystin-a proteasome inhibitor for 24 h. The cell viability, toxicity, and death were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. DNA binding viability of NF-κB and caspase-3 viability were analyzed by ELISA; the expression of p65 NF-κB nuclear protein was detected by immunocytochemistry and Western blot. Lactacystin reduced DNA binding viability of NF-κB (t = 3.0,P = 0.013) and the NF-κB viability (compared to the 5, 10 μmol/L MKN28 cell (p53 mutant) line, P < 0.001) and the expression of p65 NF-κB nuclear protein decreased parallelled to concentrations of lactacystin in MKN28 cell line, while without obvious effects on NF-κB viability in SGC7901 cell line (P = 0.381), while the viability of caspase-3 increased also along with the raising of lactacystin concentrations (compared to control, 5 μmol/L: SGC7901 cell line P = 0.029, MKN28 cell line P < 0.001; 10 μmol/L: SGC7901 cell line, P < 0.001, MKN28 cell line, P < 0.001). It was concluded that lactacystin had diversified killing effects on gastric cancer cells. The mechanism may be related to induce the apoptosis by downregulation of nuclear factor kappa B viability. There may be additional cell survival/death pathway in SGC7901 gastric cancer cells.