Metformin is the most widely used antidiabetic drug for type II diabetes in the world. Recent studies provide clues that the use of metformin may be associated with reduced incidence and improved prognosis of certain cancers and there is increasing evidence of a potential efficacy of
this agent as an anticancer drug. This observation led us to hypothesize that metformin might inhibit human breast cancer cells (MCF-7) growth. Here, we report that metformin induced apoptosis in human breast carcinoma cell lines MCF-7 cells via novel signaling pathway. Metformin induced apoptosis
by arresting cells in G1 phase and reducing cyclin D level and increasing the expression of p21 and cyclin E. Molecular and cellular studies indicated that metformin significantly elevated p53 and Bax levels and reduced STAT3 and Bcl-2. Inhibitors of signaling proteins were used
to study the mechanism(s) of metformin function. Receptor inhibitor studies indicated that p53 activation was mediated through insulin receptor (IR), not insulin-like growth factor-1 receptor (IGF-1R). Furthermore, MEK inhibitor significantly suppressed metformin-induced p53 and Bax elevation
while ERK inhibitor generated a slight reduction in p53 levels. In contrast, PI3K inhibitor did not produce any effect on the metformin-elevated p53 levels. Finally, SAPK/JNK, known to be involved in apoptosis, was activated in cells treated with metformin and the activation appeared to occur
downstream of ERK. All these results suggested that metformin activated p53, Bax, and induced tumor cell apoptosis through the ERK signaling pathway. This pathway has not been previously described for IR, p53, Bax activation, or apoptosis. Metformin, a novel inducer of apoptosis, and its analogs
may offer a novel strategy for the treatment of cancer cells.
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Document Type: Research Article
June 1, 2011
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Formerly: Oncology Research Incorporating Anti-Cancer Drug Design
Oncology Research Featuring Preclinical and Clincal Cancer Therapeutics publishes research of the highest quality that contributes to an understanding of cancer in areas of molecular biology, cell biology, biochemistry, biophysics, genetics, biology, endocrinology, and immunology, as well as studies on the mechanism of action of carcinogens and therapeutic agents, reports dealing with cancer prevention and epidemiology, and clinical trials delineating effective new therapeutic regimens.
From Volume 23, Oncology Research Featuring Preclinical and Clinical Cancer Therapeutics is Open Access under the terms of the Creative Commons CC BY-NC-ND license.