American Association for Cancer Research

Press Releases: 2012

Metformin in Combination With Common Cancer Drug Increased BRAF-Mutant Melanoma Tumor Response

March 31, 2012

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  • Drug combination superior to cancer drug alone.
  • Data emphasize importance of understanding genetic mutations.
  • Combination could be effective treatment for BRAF-mutant melanoma.

PHILADELPHIA — The combination of metformin, a commonly prescribed antidiabetic drug, and vascular endothelial growth factor-A inhibitors increased suppression of tumor growth in melanoma tumors with BRAF mutations compared with treatment with the inhibitors alone, according to the results of a study published in Cancer Discovery, a journal of the American Association for Cancer Research.

“Our results were surprising because combining metformin and vascular endothelial growth factor-A (VEGF-A) inhibitors was much more effective at blocking tumor growth than would be expected given the effect of either drug on its own,” said Richard Marais, Ph.D., who was recently appointed professor of molecular oncology and director at The Paterson Institute for Cancer Research in Manchester, England.

Although recent research has suggested that metformin may have anticancer properties, few studies have evaluated how metformin might affect the growth of melanoma, the most aggressive form of skin cancer.

To examine this association, Marais and colleagues at the Institute for Cancer Research in London tested how metformin affected a series of patient-derived melanoma cells, specifically those with two of the most common genetic mutations, BRAF and NRAS. First, they tested metformin on NRAS-mutant and BRAF-mutant melanoma cells grown in culture.

“When grown in culture, metformin had little effect on the growth of BRAF-mutant melanoma cells because BRAF activated a protein called RSK that promotes metformin resistance,” Marais said.

Next, researchers grew BRAF-mutated melanoma tumors in mice. In this setting, they found that metformin caused BRAF-mutated cells to secrete increased levels of VEGF-A, a molecule that promotes blood vessel formation and increases tumor growth. This observation prompted the researchers to use an animal model to test metformin in combination with commonly used VEGF-A inhibitors.

Tumor growth increased twofold with metformin alone. However, when metformin was combined with axitinib, tumor growth was suppressed by 45 percent; when combined with bevacizumab, tumor growth was suppressed by 64 percent compared with 34 percent for bevacizumab alone.

“Our results suggest that care should be taken when prescribing metformin to patients with BRAF-mutant melanoma as it could potentially worsen their disease,” Marais said. “Most importantly, our findings regarding the effectiveness of the metformin/VEGF-A inhibitor combination could be directly tested in the clinic.”

Moving forward, Marais and colleagues plan to research the mechanism behind this combination blocking tumor growth.

“We wish to initiate a clinical trial testing the combination of metformin and VEGF-A inhibitors in patients with BRAF-mutant melanoma, with the hope that this becomes an effective treatment option for people suffering from this deadly disease,” Marais said.

This study was funded by the Association for International Cancer Research, Cancer Research U.K. and the Institute of Cancer Research.

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Founded in 1907, the American Association for Cancer Research (AACR) is the world’s first and largest professional organization dedicated to advancing cancer research and its mission to prevent and cure cancer. AACR’s membership includes 34,000 laboratory, translational and clinical researchers; population scientists; other health care professionals; and cancer advocates residing in more than 90 countries. The AACR marshals the full spectrum of expertise of the cancer community to accelerate progress in the prevention, biology, diagnosis and treatment of cancer by annually convening more than 20 conferences and educational workshops, the largest of which is the AACR Annual Meeting with more than 18,000 attendees. In addition, the AACR publishes seven peer-reviewed scientific journals and a magazine for cancer survivors, patients and their caregivers. The AACR funds meritorious research directly as well as in cooperation with numerous cancer organizations. As the Scientific Partner of Stand Up To Cancer, the AACR provides expert peer review, grants administration and scientific oversight of individual and team science grants in cancer research that have the potential for patient benefit. The AACR actively communicates with legislators and policymakers about the value of cancer research and related biomedical science in saving lives from cancer.  

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