Metformin has always been the old reliable for treating new onset type 2 diabetes, but it’s beginning to look like it’s got a new calling as a cancer treatment. Diabetes Health recently reported on the fact that metformin reduces a type 2 person’s risk of pancreatic cancer by up to 62 percent. It’s also been observed that people with type 2 who take metformin have a much lower cancer incidence than those who don’t. Now it appears that metformin can help with breast cancer treatment as well. A study of mice with breast cancer generated from human breast cancer cells has found that they remained tumor-free for nearly three months on metformin combined with doxorubicin, a standard cancer chemotherapy. In mice given only the doxorubicin, the tumors recurred.
How metformin suppresses cancer has been unclear, but now researchers believe that they may have the answer. According to Dr. Kevin Struhl of Harvard Medical School, the lead researcher of the study, metformin selectively kills cancer stem cells. This is an extremely valuable talent because stem cells, which make up five to ten percent of a tumor’s cells, are resistant to chemotherapy. Although standard chemotherapy kills the mature cancer cells that comprise most of the tumor, it can’t vanquish the cancer stem cells. Consequently, the tumor is able to regrow after standard chemotherapy. But the combination of standard chemo and metformin appears to be very powerful.
The researchers hope that by adding metformin to the cancer treatment regimen, it will be possible to reduce the dose of standard chemo. According to Dr. Struhl, current chemo regimens load patients up with as much as they can possibly tolerate. With metformin, however, the doses of standard chemo could possibly be reduced, allowing good results with fewer side effects.
Dr. Struhl’s study grew out of another project, during which he found that the gene activity changes that occur when cells transform into cancer are a lot like what goes on in diabetes and other inflammatory conditions. He reasoned that if a common genetic pathway underlies different diseases, drugs that work against one disease might also work against another. After screening a number of drugs, he found that metformin was most effective in inhibiting cells from transforming into cancer. Those findings led to his current study, the results of which were published in the September 14 online edition of Cancer Research, a journal of the American Association for Cancer Research.
Although the current research was conducted on mice, their cancer cells were actually of human origin, which is promising. The researchers are now planning clinical trials conducted on humans. This normally lengthy process might be hastened by the fact that metformin is already an accepted drug that is known to be safe. In fact, a clinical trial to see if metformin alone is effective in preventing breast cancer from recurring in early stage breast cancer patients who have already had surgery and chemo will begin enrolling patients next year.
Interestingly, Dr. Struhl and Harvard Medical School have already applied for a patent that would cover a combination of metformin and a lower dose of chemotherapy to treat cancer.
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e! Science News article
Cancer Research online edition