Metformin is a potent inhibitor of endometrial cancer cell proliferation--implications for a novel treatment strategy.
OBJECTIVE
Obesity and diabetes are strong risk factors that drive the development of type I endometrial cancers. Recent epidemiological evidence suggests that metformin may lower cancer risk and reduce rates of cancer deaths among diabetic patients. In order to better understand metformin's anti-tumorigenic potential, our goal was to assess the effect of metformin on proliferation and expression of key targets of metformin cell signaling in endometrial cancer cell lines.


METHODS
The endometrial cancer cell lines, ECC-1 and Ishikawa, were used. Cell proliferation was assessed after exposure to metformin. Cell cycle progression was evaluated by flow cytometry. Apoptosis was assessed by ELISA for caspase-3 activity. hTERT expression was determined by real-time RT-PCR. Western immunoblotting was performed to determine the expression of the downstream targets of metformin.


RESULTS
Metformin potently inhibited growth in a dose-dependent manner in both cell lines (IC(50) of 1 mM). Treatment with metformin resulted in G1 arrest, induction of apoptosis and decreased hTERT expression. Western immunoblot analysis demonstrated that metformin induced phosphorylation of AMPK, its immediate downstream mediator, within 24 h of exposure. In parallel, treatment with metformin decreased phosphorylation of S6 protein, a key target of the mTOR pathway.


CONCLUSIONS
We find that metformin is a potent inhibitor of cell proliferation in endometrial cancer cell lines. This effect is partially mediated through AMPK activation and subsequent inhibition of the mTOR pathway. This work should provide the scientific foundation for future investigation of metformin as a strategy for endometrial cancer prevention and treatment.
Cantrell
Leigh A
LA
Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of North Carolina at Chapel Hill, CB #7572, Chapel Hill, NC 27599-7572, USA.
Zhou
Chunxiao
C
Mendivil
Alberto
A
Malloy
Kimberly M
KM
Gehrig
Paola A
PA
Bae-Jump
Victoria L
VL
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D016889:Endometrial Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D008687:Metformin / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics
D012333:RNA, Messenger; D008687:Metformin; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; C509186:TERT protein, human; D019098:Telomerase