Metformin reduces cancer risk

The anti-diabetic drug metformin is associated with reduced cancer incidence. In a UK based study of 4085 type 2 diabetics who used metformin from 1994 to 2003, investigators compared the incidence of cancer in those diebetics to the rate of cancer in diabetics who did not use metformin. The risk of cancer was reduced by 40 percent among those who took metformin (1). In a study of 1353 patients with type 2 diabetes in the Netherlands, during 9.6 years of follow-up, cancer deaths were significantly reduced among those who took metformin (2).

Among mechanisms for such a benefit are the inhibition of cancer cell growth and suppression of erb-2 oncoprotein overexpression and inhibition of mTOR (3-5). A search using the medical literature search engine, PubMed, shows over 800 papers addressing metformin and cancer ranging from human studies, as noted above, to animal models and tissue culture studies. This rapidly expanding area of laboratory and human evidence points to a role for metformin among diabetic patients. The call for clinical trials is well justified (6).

Literature cited

1. Libby G, Donnelly LA, Donnan PT, Alessi DR, Morris AD, Evans JM. New users of metformin are at low risk of incident cancer: a cohort study among people with type 2 diabetes. Diabetes Care. Sep 2009;32(9):1620-1625.
2. Landman GW, Kleefstra N, van Hateren KJ, Groenier KH, Gans RO, Bilo HJ. Metformin associated with lower cancer mortality in type 2 diabetes: ZODIAC-16. Diabetes Care. Feb 2010;33(2):322-326.
3. Alimova IN, Liu B, Fan Z, et al. Metformin inhibits breast cancer cell growth, colony formation and induces cell cycle arrest in vitro. Cell Cycle. Mar 15 2009;8(6):909-915.
4. Vazquez-Martin A, Oliveras-Ferraros C, Menendez JA. The antidiabetic drug metformin suppresses HER2 (erbB-2) oncoprotein overexpression via inhibition of the mTOR effector p70S6K1 in human breast carcinoma cells. Cell Cycle. Jan 1 2009;8(1):88-96.
5. Vazquez-Martin A, Oliveras-Ferraros C, del Barco S, Martin-Castillo B, Menendez JA. mTOR inhibitors and the anti-diabetic biguanide metformin: new insights into the molecular management of breast cancer resistance to the HER2 tyrosine kinase inhibitor lapatinib (Tykerb). Clin Transl Oncol. Jul 2009;11(7):455-459.
6. Goodwin PJ, Ligibel JA, Stambolic V. Metformin in breast cancer: time for action. J Clin Oncol. Jul 10 2009;27(20):3271-3273.

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