Metformin Induces Apoptosis and Cell Cycle Arrest Mediated by Oxidative Stress, AMPK and FOXO3a in MCF-7 Breast Cancer Cells

Abstract

Recent studies have demonstrated that the anti-diabetic drug, metformin, can exhibit direct antitumoral effects, or can indirectly decrease tumor proliferation by improving insulin sensitivity. Despite these recent advances, the underlying molecular mechanisms involved in decreasing tumor formation are not well understood. In this study, we examined the antiproliferative role and mechanism of action of metformin in MCF-7 cancer cells treated with 10 mM of metformin for 24, 48, and 72 hours. Using BrdU and the MTT assay, it was found that metformin demonstrated an antiproliferative effect in MCF-7 cells that occurred in a time- and concentration- dependent manner. Flow cytometry was used to analyze markers of cell cycle, apoptosis, necrosis and oxidative stress. Exposure to metformin induced cell cycle arrest in G0-G1 phase and increased cell apoptosis and necrosis, which were associated with increased oxidative stress. Gene and protein expression were determined in MCF-7 cells by real time RT-PCR and western blotting, respectively. In MCF-7 cells metformin decreased the activation of IRβ, Akt and ERK1/2, increased p-AMPK, FOXO3a, p27, Bax and cleaved caspase-3, and decreased phosphorylation of p70S6K and Bcl-2 protein expression. Co-treatment with metformin and H2O2 increased oxidative stress which was associated with reduced cell number. In the presence of metformin, treating with SOD and catalase improved cell viability. Treatment with metformin resulted in an increase in p-p38 MAPK, catalase, MnSOD and Cu/Zn SOD protein expression. These results show that metformin has an antiproliferative effect associated with cell cycle arrest and apoptosis, which is mediated by oxidative stress, as well as AMPK and FOXO3a activation. Our study further reinforces the potential benefit of metformin in cancer treatment and provides novel mechanistic insight into its antiproliferative role.

Metformin use and survival after colorectal cancer: A population‐based cohort study

“…6 Adjusted model contains all variables in " 1" along with BMI prior to diagnosis (in individuals with BMI available). 7 Adjusted model contains all variables in " 1" along with smoking prior to diagnosis (in individuals with smoking available). 8 Adjusted model contains all variables in " 1" along with tumour grade prior to diagnosis (in individuals with grade available).…”

“…[2][3][4] Although not fully elucidated, the potential anti-tumour effects of metformin are thought to be due to inhibition of the mammalian target of rapamycin (mTOR) signalling pathway, resulting in suppression of cellular proliferation 5 tumour cell migration and invasion 6 as well as an increase in apoptosis. 7 Despite mounting preclinical evidence supporting a possible therapeutic role for metformin in colorectal cancer, only two epidemiological studies have evaluated the impact of post-diagnostic metformin exposure on cancer outcomes in colorectal cancer patients with type 2 diabetes. A Korean study of 595 colorectal cancer patients with type 2 diabetes reported substantial reductions in risk of colorectal cancerspecific and all-cause mortality among metformin users after diagnosis.…”

The association between glucose-lowering drug use and mortality among breast cancer patients with type 2 diabetes

“…Several laboratory studies show that metformin use is associated with cell growth suppression in breast cancer cells, possibly mediated by activation of 5'-adenosine monophosphate-activated protein kinase (AMPK) [5,6]. Observational studies also show that metformin use is associated with a 20-30% lower breast cancer incidence [7][8][9].…”

Exosomes and development of cancer cell resistance to metformin: pilot study

“…Выбор для работы именно этого соединения был обусловлен 2 основными факторами. С одной стороны, метформин принадлежит к совершен-но отличному от стероидов классу соединений, и его противоопухолевая активность ассоциирована, преиму-щественно, с подавлением АМРК и mTOR-сигналинга [14]. С другой стороны, в основе приобретенной рези-стентности к метформину лежит компенсаторная реак-тивация сигнальных путей [7], как и в случае гормо-нальной резистентности, что могло свидетельствовать о существовании общих механизмов распространения обоих видов резистентности.…”