Over-activated Notch-1 protects gastric carcinoma BGC-823 cells from TNFα-induced apoptosis

Background/Aim The role of Notch-1 in human gastric carcinoma, one of the most common carcinomas of the human digestive tract, remains poorly characterised. Here, we investigated the effect and mechanism of Notch-1 activation on TNFα-induced apoptosis of human gastric carcinoma BGC-823 cells. Methods Cell viabililty was measured by MTT assay. Apoptosis was detected by flow cytometry assay. Notch-1, Hes-1, caspase-3 p20 and NF-κB p65 expressions were assayed by Western blotting. NF-κB activation was tested by electrophoretic mobility shift assay (EMSA), and caspase-3 activation was tested by colorimetric assay. Results BGC-823 cells underwent apoptosis following stimulation with TNFα. We found that Notch-1 was over-activated by overexpressing exogenous intracellular domain of Notch (ICN) via retrovirus-mediated gene transfer, and over-activated Notch-1 reduced the TNFα-induced growth suppression and apoptosis in BGC-823 cells. Down-regulation of Notch-1 by siRNA targeting Notch-1 enhanced TNFα-induced apoptosis in BGC-823 cells. As the molecular mechanism involved, we showed over-activated Notch-1 partially suppressed TNFα-induced activation of caspase-3. However, TNFα-induced activation of NF-κB was not affected by over-activated Notch-1. Conclusions Our data indicate that over-activated Notch-1 significantly protects BGC-823 cells from TNFα-induced apoptosis, and this effect is mediated, at least in part, by decreasing activation of caspase-3 independent of NF-κB.