PHILADELPHIA — Metformin, a drug commonly used to treat type 2 diabetes, shows potential in the prevention of tobacco-induced lung tumors and possibly colorectal tumors, according to two studies published in Cancer Prevention Research.
The first study, conducted by researchers at the NCI, showed that metformin significantly decreased lung tumor burden in mice exposed to a nicotine-derived nitrosamine called NNK, which is the most prevalent carcinogen in tobacco. Researchers treated the mice with metformin either orally or by injection. Those treated orally had between 40 and 50 percent fewer tumors, while those mice treated with injection had 72 percent fewer tumors. Based on these findings, clinical trials of metformin are being considered to determine if this compound could be used as an effective chemoprevention agent for smokers at high risk of developing lung cancer.
A second study, conducted by researchers in Japan, showed, non-diabetics taking metformin had a significantly lower rate of rectal aberrant crypt foci, a surrogate marker of colorectal cancer. Patients in the treatment group had a mean of 5.11 foci compared with 7.56 in the control group.
Results of these studies were discussed at a teleconference hosted by Scott Lippman, M.D., editor-in-chief of Cancer Prevention Research, and professor and chair in the department of thoracic head and neck medical oncology at the University of Texas M. D. Anderson Cancer Center on Wednesday, Sept. 1, 2010, at 10:30 a.m. ET.
Metformin significantly decreased lung tumor burden in mice exposed to a nicotine-derived nitrosamine called NNK, which is the most prevalent carcinogen in tobacco. Metformin has been previously shown to activate an enzyme called AMP-activated protein kinase that is known to inhibit mTOR, a protein that regulates cell growth and survival in tobacco carcinogen-induced lung tumors.
Download* a recording of the teleconference. (10.7 MB, 46 minutes and 51 seconds)
*On a PC, right mouse click on the “Download” link and select “Save link as…” in Firefox or “Save Target as…” in Internet Explorer.
The following panelists participated in the teleconference:
Philip Dennis, M.D., Ph.D., a senior investigator at the NCI, treated the mice with metformin either orally or by injection. Those treated orally had between 40 and 50 percent fewer tumors, while those mice treated with injection had 72 percent fewer tumors. Based on these findings, clinical trials of metformin are being considered to determine if this compound could be used as an effective chemoprevention agent for smokers at high risk of developing lung cancer.
“Although smoking cessation is the most important step for current smokers, over half of lung cancer cases are diagnosed in former smokers, raising the importance of identifying those at highest risk and identifying effective preventive treatments,” said Dennis.
In addition to Lippman and Dennis, the following panelists will participate in the teleconference:
Michael Pollak, M.D., professor in the department of medicine and oncology at McGill University and author of a mini-review on metformin published in Cancer Prevention Research:
“This important laboratory study, together with prior laboratory and epidemiology research, suggests that metformin may be useful in cancer prevention and treatment. There is new information available about the mechanisms by which this drug, which is based on compounds present in lilac, may be useful for cancer control.”
Jeffrey A. Engelman, M.D., Ph.D., director of the centers for thoracic cancers at Massachusetts General Hospital and co-author of an accompanying editorial published in Cancer Prevention Research:
“Previous epidemiology studies have shown that diabetics taking metformin have a lower risk of developing cancer. In this study, researchers carefully controlled for glucose levels, which suggests that the effect may be seen beyond the diabetic population.”
Lewis Cantley, Ph.D., director of the cancer center at Beth Israel Deaconess Medical Center and the second co-author of the accompanying editorial published in Cancer Prevention Research:
“Targeted therapies have impacted the course of cancer treatments, but they have yet to be widely utilized as agents for chemoprevention. As we work to better understand the mechanisms of action, therapies like metformin hold promise for delaying or preventing cancer progression and having a substantial, beneficial impact on cancer mortality.”
The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, the AACR is the world’s oldest and largest professional organization dedicated to advancing cancer research. The membership includes 32,000 basic, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and more than 90 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants, research fellowship and career development awards. The AACR Annual Meeting attracts more than 17,000 participants who share the latest discoveries and developments in the field. Special conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care. The AACR publishes six major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; and Cancer Prevention Research. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists. CR provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship and advocacy.
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