Helicobacter pylori is the definitive carcinogen for stomach cancer and is known to induce proinflammatory cytokines, such as tumor necrosis factor-$alpha$ (TNF-$alpha$) and interleukin-1(IL-1) in the stomach. Based on our findings that TNF-$alpha$ is an endogenous tumor promoter, we identified the TNF-$alpha$ inducing protein (Tip$alpha$) gene family, and confirmed Tip$alpha$ and HP-MP1 as new carcinogenic proteins of H. pylori. Tip$alpha$ protein is unique to H. pylori, and this paper shows the strong tumor promoting activity of Tip$alpha$ gene family, in cooperation with Ras protein and its mechanisms of action in relation to NF-${kappa}B$ activation, and discusses the carcinogenic role of Tip$alpha$ in stomach cancer. Our recent finding showing that penicillin-binding proteins of other bacteria are weak homologues of Tip$alpha$ is also discussed.