The anti-proliferative effect of metformin in triple-negative MDA-MB-231 breast cancer cells is highly dependent on glucose concentration: implications for cancer therapy and prevention.
BACKGROUND
Metformin has been shown to have a strong anti-proliferative effect in many breast cancer cell lines, mainly due to the activation of the energy sensing kinase, AMP-activated protein kinase (AMPK). MDA-MB-231 cells are aggressive and invasive breast cancer cells that are known to be resistant to several anti-cancer agents as well as to the anti-proliferative effect of metformin. As metformin is a glucose lowering drug, we hypothesized that normoglycemia will sensitize MDA-MB-231 cells to the anti-proliferative effect of metformin.


METHODS
MDA-MB-231 cells were treated with increasing metformin concentrations in hyperglycemic or normoglycemic conditions. The growth inhibitory effect of metformin was assessed by MTT assay. The expression of several proteins involved in cell proliferation was measured by Western blotting.


RESULTS
In agreement with previous studies, treatment with metformin did not inhibit the growth of MDA-MB-231 cells cultured in hyperglycemic conditions. However, metformin significantly inhibited MDA-MB-231 growth when the cells were cultured in normoglycemic conditions. In addition, we show that metformin-treatment of MDA-MB-231 cells cultured in normoglycemic conditions and not in hyperglycemic conditions caused a striking activation of AMPK, and an AMPK-dependent inhibition of multiple molecular signaling pathways known to control protein synthesis and cell proliferation.


CONCLUSIONS
Our data show that normoglycemia sensitizes the triple negative MDA-MB-231 breast cancer cells to the anti-proliferative effect of metformin through an AMPK-dependent mechanism.


CONCLUSIONS
These findings suggest that tight normoglycemic control may enhance the anti-proliferative effect of metformin in diabetic cancer patients.
Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Beshay N M
BN
Zordoky
Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Diana
D
Bark
Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Carrie L
CL
Soltys
Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
Miranda M
MM
Sung
Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada. Electronic address: jason.dyck@ualberta.ca.
Jason R B
JR
Dyck
D055372:AMP-Activated Protein Kinases / Q000502:physiology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008687:Metformin / Q000494:pharmacology*; D050811:Octamer Transcription Factor-1 / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000502:physiology; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control
D000970:Antineoplastic Agents; D007328:Insulin; D050811:Octamer Transcription Factor-1; D008687:Metformin; C546842:MTOR protein, human; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D005947:Glucose
AMP-activated protein kinase; Breast cancer; Diabetes; MDA-MB-231; Metformin