The phenomenon of acquired resistance to metformin in breast cancer cells: The interaction of growth pathways and estrogen receptor signaling

Alexander M. Scherbakov, Danila V. Sorokin, Victor V. Tatarskiy, Nikolay S. Prokhorov, Svetlana E. Semina, Lev M. Berstein, Mikhail A. Krasil'Nikov

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Metformin, a biguanide antidiabetic drug, is used to decrease hyperglycemia in patients with type 2 diabetes. Recently, the epidemiological studies revealed the potential of metformin as an anti-tumor drug for several types of cancer, including breast cancer. Anti-tumor metformin action was found to be mediated, at least in part, via activation of adenosine monophosphate-activated protein kinase (AMPK) - intracellular energy sensor, which inhibits the mammalian target of rapamycin (mTOR) and some other signaling pathways. Nevertheless, some patients can be non-sensitive or resistant to metformin action. Here we analyzed the mechanism of the formation of metformin-resistant phenotype in breast cancer cells and its role in estrogen receptor (ER) regulation. The experiments were performed on the ER-positive MCF-7 breast cancer cells and metformin-resistant MCF-7 subline (MCF-7/M) developed due to long-term metformin treatment. The transcriptional activity of NF-κB and ER was measured by the luciferase reporter gene analysis. The protein expression was determined by immunoblotting (Snail1, (phospho)AMPK, (phospho)IκBα, (phospho)mTOR, cyclin D1, (phospho)Akt and ERα) and immunohistochemical analysis (E-cadherin). We have found that: 1) metformin treatment of MCF-7 cells is accompanied with the stimulation of AMPK and inhibition of growth-related proteins including IκBα, NF-κB, cyclin D1 and ERα; 2) long-term metformin treatment lead to the appearance and progression of cross-resistance to metformin and tamoxifen; the resistant cells are characterized with the unaffected AMPK activity, but the irreversible ER suppression and constitutive activation of Akt/Snail1 signaling; 3) Akt/Snail1 signaling is involved into progression of metformin resistance. The results presented may be considered as the first evidence of the progression of cross-resistance to metformin and tamoxifen in breast cancer cells. Importantly, the acquired resistance to both drugs is based on the constitutive activation of Akt/Snail1/E-cadherin signaling that opens new perspectives to overcome the metformin/tamoxifen resistance of breast cancer.

Original languageEnglish (US)
Pages (from-to)281-292
Number of pages12
JournalIUBMB Life
Issue number4
StatePublished - Apr 1 2016


  • breast cancer
  • cell signaling
  • epithelial-mesenchymal transition
  • metformin
  • signal transduction
  • signal transduction pathways

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Genetics
  • Clinical Biochemistry
  • Cell Biology


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