[Anti-cancer activity of metformin: new perspectives for an old drug].

Type 2 diabetes is associated with a higher risk of cancer, which appears more obvious since the reduction of cardiovascular mortality. All glucose-lowering oral agents do not have the same impact on cancer: the risk is increased with sulfonylureas and decreased with metformin (and glitazones). Numerous epidemiological observational and case-control studies showed that metformin is associated with a lower incidence of cancer and a lower cancer-related death rate. A dose-response relationship and a relation between duration of prior treatment with metformin and the protective effect against cancer have been reported. Mechanisms involved are the activation of the AMPK enzyme and the inhibition of the mTOR pathway. Studies with metformin are ongoing in the field of oncology, especially as adjunct to treatment of breast cancer.