Carcinogenesis, apoptosis and cell proliferation.

Biological agents, especially viruses, have been linked to the carcinogenesis process in major human cancers, especially lymphomas (retroviruses), hepatocarcinomas (hepatitis viruses) and carcinomas of the female genital organs (papilloma viruses). Chronic infection and inflammation have long been suspected to play a role in human carcinogenesis. Helicobacter pylori is the first bacterial infection recognized as a human carcinogen, essentially on the basis of epidemiological evidence of causality. Contrary to most other recognized human carcinogens, experimental evidence of carcinogenesis is lacking. As a consequence, mechanistic explanations of H. pylori carcinogenesis at this point in time are hypothetical.