Helicobacter pylori induces antiapoptosis through nuclear factor-κB activation

Although Helicobacter pylori is classified as a definite carcinogen, the mechanism underlying gastric carcinogenesis is not yet clear. We previously have shown that H. pylori activates an antiapoptotic gene, the cellular inhibitor of apoptosis protein 2 (c-IAP2), the underlying mechanism of which was investigated in the present study. cDNA array and real-time PCR analyses indicated that H. pylori showed a stimulatory effect on the expression of c-IAP2. Isogenic mutant strains with impaired cag pathogenicity island (cagPAI) expression showed weaker induction. Analyses that used the in situ terminal deoxynucleotide transferase-mediated dUTP nick end-labeling method indicated suppression of antiapoptosis by the antisense c-IAP2 oligonucleotide. Reporter assays with deletion and mutation constructs for the c-IAP2 promoter showed that nuclear factor-kappaB (NF-kappaB) binding sites are indispensable for transactivation. Super-repressor IkappaBalpha or NF-kappaB inhibitor reduced c-IAP2 transactivation by H. pylori, and exogenous expression of c-IAP2 inhibited apoptosis seen with H. pylori. In conclusion, H. pylori induces antiapoptosis through c-IAP2 transactivation following cagPAI-dependent NF-kappaB activation. The interaction of these stimuli may play a role in gastric carcinogenesis.