Metformin inhibits IGF-1 and possibly cancer.

Metformin, a safe and inexpensive drug widely used to lower blood glucose in Type 2 diabetics, may have a variety of other uses, researchers are finding. The newest, reported Monday at a Washington meeting of the American Assn. for Cancer Research, is to prevent lung cancer in smokers.

Metformin inhibits a hormone called insulin-like growth factor-1, or IGF-1, which explains its anti-diabetes activity. But IGF-1 also plays a crucial role in cancer development, and a variety of observational studies have hinted that, by blocking its activity, metformin may inhibit cancer. Studies have shown, for example, that women being treated for breast cancer who are also diabetic and taking metformin have a threefold better response to their chemotherapy. Researchers are now organizing a clinical trial to test its effects.