Abstract: Metformin is the most widely used antidiabetic drug in the world,and there is an increasing evidence that this agent plays an important role in anti-caner therapy.Firstly,there is a decrease in cancer incidence in metformin-treated patients.Secondly,metformin activates the AMP activated protein kinase(AMPK)pathway,which has been proposed as a promising therapeutic target in cancer.Finally,metformin has a direct inhibitory effect on cancer growth and an antitumoral action.