Metformin for Cancer?

Most people know Metformin is the original, cheapest, and still the best prescription drug for Diabetes. But what few know is there is a body of research currently being conducted on metformin and cancer. You probably won't hear much about this in the news, because metformin is an old drug that is generic now, and big pharma sees no profits from doing trials on it's effects against cancer. From Life Extension's article on metformin...

"Some of metformin’s most compelling effects are in cancers of the reproductive system because it blocks the enzyme called aromatase, which can stimulate estrogen-dependent cancer growth. (21) Breast cancer is the most common malignancy diagnosed in women. (22) Fortunately, most varieties of breast cancer are proving to be especially susceptible to metformin prevention in the laboratory, and to metformin treatment in human patients, as shown by studies that have emerged over just the past two years. (23)

Metformin suppresses a specific cancer-inducing protein (human epidermal growth factor receptor 2, or HER2) (24) that dramatically increases the risk of breast cancer. (25) By suppressing HER2, which can stop cancers from developing in the first place, metformin halts cancer cells’ reproductive cycle, preventing them from growing once they have developed. (26)

Via a different set of mechanisms, metformin selectively targets cancer stem cells, cells that resist chemotherapy drugs and can regenerate and cause relapse of the disease. (27) In live animal studies, metformin suppressed breast cancers, especially in animals on a high-calorie diet. (20) In a dramatic 2010 study, metformin extended the life span of mice with HER2-positive breast cancers, delayed the onset of tumor development, and inhibited the growth of implanted tumors. (19)

The combination of all these effects means that metformin is effective against many different types of breast cancers, including those that are estrogen receptor positive and negative, and those that express both normal and excessive amounts of HER2. (28) Indeed, data appeared in 2010 that long-term (greater than 5-year) metformin use by humans is associated with a substantial (56%) reduction in risk for developing breast canceras compared with no use of metformin. (1)

Human trials have already demonstrated that diabetic patients with breast cancer who receive metformin plus chemotherapy have a higher rate of complete remission than do those not taking metformin. Complete remission occurred in 24% of diabetic patients taking metformin, 8% of diabetic patients not taking metformin, and 16% of non-diabetic patients not taking metformin. (29) And a 2009 study showed that metformin induced unique, multitargeted responses in so-called “triple-negative” breast cancer cells, which represent some of the most difficult-to-treat forms of the malignancy. (30)

All of these findings speak to metformin’s tremendous potential as a true breast cancer chemopreventive agent—one that can and should be used long before any sign of cancer has appeared. Scientists from around the world believe that the time has come to leverage these effects in breast cancer chemoprevention and treatment. " (22,23,31,32)


Metformin inhibits Cancer


Read more about Metformin's benefits on Life Extension's website here



  • Cindy Benson

    Did they check it out with aromitace inhibitors? Can you take metformin with arimidex and prediabetic? Er/pr 95% + her2- IDC

  • John Boyce

    Hi Denise,
    There are great studies on Metformin helping fight ER positive breast cancer.

    Tamoxifen, an endocrine therapy drug used to treat breast cancer, is designed to interrupt estrogen signaling by blocking the estrogen receptor (ER). However, many ER-positive patients are low reactive or resistant to tamoxifen. Metformin is a widely used anti-diabetic drug with noteworthy anti-cancer effects. We investigated whether metformin has the additive effects with tamoxifen in ER-positive breast cancer therapy.

    The efficacy of metformin alone and in combination with tamoxifen against ER-positive breast cancer was analyzed by cell survival, DNA replication activity, plate colony formation, soft-agar, flow cytometry, immunohistochemistry, and nude mice model assays. The involved signaling pathways were detected by western blot assay.

    When metformin was combined with tamoxifen, the concentration of tamoxifen required for growth inhibition was substantially reduced. Moreover, metformin enhanced tamoxifen-mediated inhibition of proliferation, DNA replication activity, colony formation, soft-agar colony formation, and induction of apoptosis in ER-positive breast cancer cells. In addition, these tamoxifen-induced effects that were enhanced by metformin may be involved in the bax/bcl-2 apoptotic pathway and the AMPK/mTOR/p70S6 growth pathway. Finally, two-drug combination therapy significantly inhibited tumor growth in vivo.

    The present work shows that metformin and tamoxifen additively inhibited the growth and augmented the apoptosis of ER-positive breast cancer cells. It provides leads for future research on this drug combination for the treatment of ER-positive breast cancer.

    “Collectively, our results suggest that one of the anticancer mechanisms of metformin could be attributable to the repression of expression and transcriptional activity of ERα. Metformin may be a good therapeutic agent for treating ERα-positive breast cancer by inhibiting the expression and function of ERα. In addition, metformin may be useful to treat tamoxifen-resistant breast cancer.”

  • John Boyce

    Hi Janet,
    General contraindications for Metformin are Liver, Kidney and Respiratory problems…if you have them already, speak to your doctor first. But generally Metformin will not be prescribed unless you are already a diabetic…unfortunately too late. Since you have breast cancer in your family, our product Cell Stop at half a normal dosage (2 caps instead of 4 caps), would be strongly encouraged for prevention.

  • Denise assalian

    If you are a breast cancer survivor , from a very estrogen positive breast cancer , would metformin help ?

  • Janet Feig

    I know there are side effects to any prescription but would that apply to non drug form too? I do have prediabetes. And don’t want to get breast cancer. It’s in my maternal family line.

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