Is it the time for metformin to take place in adjuvant treatment of Her-2 positive breast cancer? Teaching new tricks to old dogs

Med Hypotheses. 2009 Oct;73(4):606-7. doi: 10.1016/j.mehy.2009.05.027. Epub 2009 Jun 27.


Breast cancer is the most common malignancy diagnosed among women. According to the new molecular subclassification, basal like and Her-2 positive breast cancers have the worst outcome and these are the ones in which chemotherapy is a must as a part of adjuvant treatment. New treatment options that could be used as an adjuvant maintenance treatment are still being investigated. Insulin hormone is one of the reasons of breast cancer recurrence and death in breast cancer survivors. Targeting insulin as a therapeutic modality in breast cancer could be an option in the adjuvant treatment of breast cancer. It seems that insulin may signal to activate a cascade of proliferative and anti-apoptotic events in the cancer cell. Metformin, an oral anti-diabetic known for 50 years, may also have direct effects on cancer cells. Metformin causes Her-2 suppression via the inhibition of mTOR in breast cancer cells. Thus, we believe that the time has arrived both to target insulin reduction and to alter Her-2 oncogene based molecular pathogenetic steps in breast cancer by using metformin as an adjuvant therapy in breast cancer patients.

MeSH terms

  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism*
  • Chemotherapy, Adjuvant / methods
  • Drug Delivery Systems / methods*
  • Humans
  • Hypoglycemic Agents / administration & dosage
  • Insulin / metabolism*
  • Metformin / administration & dosage*
  • Models, Biological*
  • Protein Kinases / metabolism*
  • Receptor, ErbB-2 / antagonists & inhibitors*
  • Signal Transduction / drug effects
  • TOR Serine-Threonine Kinases


  • Hypoglycemic Agents
  • Insulin
  • Metformin
  • Protein Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Receptor, ErbB-2