[ElaineM]

1. http://search.lef.org/cgi-src-bin/MsmGo.exe?grab_id=0&page_id=598&query=Metformin&hi word=METFORMINS%20Metformin%20
2. http://search.lef.org/cgi-src-bin/MsmGo.exe?grab_id=0&page_id=3015&query=Metformin&h iword=METFORMINS%20Metformin%20
Breast Cancer

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 cancer as 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
What You Need to Know: Metfo