Diabetic drug metformin may help in cancer treatment

Researchers based at the Harvard Medical School, Harvard University, Boston, USA, conducted a lab test on mice carrying human breast cancer cells. They were treated with low doses of metformin combined with doxorubicin -- a drug widely used in cancer chemotherapy.

The researchers found that metformin-chemo combination shrank the breast cancer tumors in the mice and proved more effective than the standard chemotherapy. The mice which were treated with the combination remained cancer-free for four months, while tumors had occurred again in mice which were given either drug alone.

Metformin is an approved drug for treating Type 2 diabetes and makes the body more sensitive to insulin. It is marketed under the brand names Glucophage, Riomet, Fortamet, Glumetza, Obimet, Dianben and Diabex.

Metformin kills cancer stem cells and eases chemotherapy
The study explained that the kind of cells metformin targets are cancer stem cells -- cancer cells found within tumors that possess the ability to give rise to all cell types found in a particular cancer sample. These cancer stem cells are more resistant to the standard chemotherapy, resulting in regeneration of tumors followed by a relapse.

Lead Harvard researcher Kevin Struhl, PhD who led the study said that 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 said.

"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,” he added.

New properties of metformin found
Researchers have discovered certain properties of the drug metformin that can be used in the treatment and prevention of breast cancer as well as other types of cancer in people taking metformin for diabetes.

Struhl said that the study was conducted on breast cancer cells, but a lot of data shows that the drug is capable of reducing risks in other types of cancers too.

Previous studies have also shown that diabetic patients treated with metformin were less likely to develop pancreatic cancer than others.

Clinical trials on humans to begin soon
Struhl informed that researchers are planning clinical trials on humans now, which will be the "ultimate test” to check the effectiveness of metformin in treating breast cancer.

"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,” he maintained.

The effectiveness of the metformin-chemo combination is only in theory as yet, and it’s not certain that metformin would be used to treat cancer patients. Therefore, National Cancer Institute of Canada is sponsoring a clinical trial to test the effectiveness of metformin alone in early stages of breast cancer patients. The U.S. researchers will be participating in the procedure.

Jennifer Ligibel, a breast cancer doctor at Dana-Farber Cancer Institute, Boston, said that the idea is to see how effective is the drug in killing the cancer stem cells and preventing the disease’s recurrence. The patients might start enrolling from next year.

The study has been published in Cancer Research, a journal of the American Association for Cancer Research.