A new article in the March 2010 issue of Clinical Cancer Research has suggested that the anti-diabetes drug metformin should be studied as a breast cancer treatment. Metformin influences two important, related pathways that are involved in cancer growth: the insulin/insulin-like growth factor-1 signaling pathway and the adenosine mono-phosphate-activated protein kinase (AMPK) pathway. Metformin reduces gluconeogenesis in the liver, enhances the uptake of glucose in muscles, and reduces the level of circulating glucose. Metformin also reduces circulating insulin levels, increases insulin sensitivity, and reduces insulin resistance-associated excess levels of circulating insulin in the blood. At the cell level, metformin activates AMPK.

Extensive studies have reported anticancer effects of metformin in all breast cancer subtypes in the laboratory, including in chemotherapy-resistant cells. In addition, epidemiological and retrospective data support the anti-cancer effects of metformin. The authors conclude that metformin should be studied as a breast cancer therapy in a variety of clinical settings.