Causal role of Helicobacter pylori infection and eradication therapy in gastric carcinogenesis

Many epidemiological reports indicate that Helicobacterpylori(H pylori)infection plays an important role ingastric carcinogenesis.Several genetic and epigeneticalterations contribute to the initiation,promotion,andprogression of the cancer cells in a multi-step manner.H pylori is known to induce chronic inflammation in thegastric mucosa.Its products,including superoxides,participate in the DNA damage followed by initiation,andthe inflammation-derived cytokines and growth factorscontribute to the promotion of gastric carcinogenesis.By eradicating H pylori,gastric inflammation can becured; the therapy diminishes the levels not onlyof inflammatory cell infiltration,but also atrophy/intestinal metaplasia in part.A randomized controlledtrial revealed that the eradication therapy diminishedthe gastric cancer prevalence in cases without pre-cancerous conditions.In addition,recent epidemiologicalstudies from Japanese groups demonstrated thatthe development of gastric cancer,especially of theintestinal type,was decreased by successful eradicationtherapy,although these were designed in a non-randomized manner.However,it should be mentionedthat endoscopic detection is the only way to evaluate thedegree of gastric carcinogenesis.We have reported thatthe endoscopic and histological morphologies could bemodified by eradication therapy and it might contributeto the prevalence of gastric cancer development.Considering the biological nature of cancer cellproliferation,it is considered that a sufficiently long-termfollow-up would be essential to discuss the anticancereffect of eradication therapy.