Metformin: New 'wonder drug' may help prevent lung cancer in smokers
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.
At an American Society of Clinical Oncology meeting on genitourinary cancers last month, Dr. Cristiano Ferrario of McGill University in Montreal, Canada, reported that metformin could inhibit the growth of prostate cancer cells in the laboratory -- albeit by inhibiting a different receptor.
Some observational studies have suggested that smokers who are diabetic and taking metformin are less likely to develop lung cancer. Dr. Phillip A. Dennis of the National Cancer Institute tested that idea by giving metformin to mice exposed to a tobacco carcinogen known as nicotine-derived nitrosamine, which normally induces tumors in experimental animals quite easily. He reported at Monday's meeting that administering the drug orally reduced tumor burden by 40% to 50%. Injecting it reduced the burden by 72%. The levels of metformin used in the mice are easily achievable in humans and are not associated with significant side effects, he said.
Some other studies have suggested that metformin may also reduce cardiovascular disease not directly related to diabetes. The problem with all these studies is that metformin is now a generic drug, so there is no incentive for pharmaceutical companies to launch an expensive clinical trial to demonstrate the drug's utility when they would not be the exclusive beneficiary of their findings.
-- Thomas H. Maugh II