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Breast Cancer Health Center

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Diabetes Drug Fights Breast Cancer

Metformin Kills Breast Cancer Stem Cells, May Fight Many Cancers

Metformin Kills Cancer Stem Cells continued...

Struhl says cancer stem cells are "far more nasty" than regular cancer cells.

"The bulk of the cells in a tumor are cancer cells which grow but are killed by chemotherapy," Struhl says. "But there is also a small population of cancer stem cells, which are better able to form tumors on their own and more resistant to chemotherapy than cancer cells. After standard chemotherapy, they can remain and essentially regenerate the tumor, and the disease is back again."

Different researchers have recently described new compounds that selectively kill cancer stem cells. Whether these compounds might one day become safe and effective cancer drugs remains to be shown.

Struhl -- who, with Harvard Medical School, holds a patent on the combined use of metformin and low-dose chemotherapy -- says metformin is already known to be safe and merely needs to be proven effective in human clinical trials.

Easier Cancer Chemo With Metformin?

Another reason researchers are excited about the study findings is that metformin and standard chemotherapy seem to make each other work better.

"Because of this synergy with chemotherapy, metformin could be used with lower doses of chemotherapy," Struhl suggests. "Chemotherapy is quite a toxic thing for people to deal with, and if one could lower the dose that would be very nice."

Metformin itself has an outstanding safety record.

"This drug at low doses can be considered a very good candidate for cancer prevention before a person has any cancer at all," Rauscher said. "The hope is we can use a drug like metformin and continue to deplete the levels of these inherently chemotherapy-resistant, dormant cancer stem cells."

Can Metformin Prevent Breast Cancer Recurrence?

Ligibel, who was not involved in the Struhl study, has argued that metformin should be tested in people.

Taking her own advice, she is participating in a human study led by Canada's national cancer institute that will test whether metformin can prevent breast cancer from coming back after treatment. The study, which will take place at multiple cancer centers in Canada and the U.S., has not yet begun enrollment.

Unfortunately, Ligibel said, there are no plans for studies combining metformin with chemotherapy. But Struhl said that because metformin is an approved drug, such studies could begin relatively soon.

"We are hoping for researchers to actually try that experiment," Struhl said. "The idea of using this as a combined treatment is the main point of our paper."

"These concepts should be moved forward in clinical trials," Rauscher agreed.

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