Opinion: Bacterial toxins and cancer--a case to answer?

Since the discovery that Helicobacter pylori infection leads to gastric cancer, other chronic bacterial infections have been shown to cause cancer. The bacterial and host molecular mechanisms remain unclear. However, many bacteria that cause persistent infections produce toxins that specifically disrupt cellular signalling to perturb the regulation of cell growth or to induce inflammation. Other bacterial toxins directly damage DNA. Such toxins mimic carcinogens and tumour promoters and might represent a paradigm for bacterially induced carcinogenesis.