Metformin blocks migration and invasion of tumour cells by inhibition of matrix metalloproteinase-9 activation through a calcium and protein kinase Calpha-dependent pathway: phorbol-12-myristate-13-acetate-induced/extracellular signal-regulated kinase/activator protein-1.
OBJECTIVE
Population studies have revealed that treatment with the anti-diabetic drug metformin is significantly associated with reduced cancer risk, but the underlying mode of action has not been elucidated. The aim of our study was to determine the effect of metformin on tumour invasion and migration, and the possible mechanisms, using human fibrosarcoma HT-1080 cells.


METHODS
We employed invasion, migration and gelatin zymography assays to characterize the effect of metformin on HT-1080 cells. Transient transfection assays were performed to gene promoter activities, and immunoblot analysis to study its molecular mechanisms of action.


RESULTS
Metformin inhibited migration and invasion by HT-1080 cells at sub-toxic concentrations. In these cells, metformin also suppressed phorbol-12-myristate-13-acetate (PMA)-enhanced levels of matrix metalloproteinases-9 (MMP-9) protein, mRNA and transcription activity through suppression of activator protein-1 (AP-1) activation. In addition, metformin strongly repressed the PMA-induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and protein kinase C(PKC)alpha, whereas the phosphorylation of p38 mitogen-activated protein kinase was not affected by metformin. Metformin decreased the PMA-induced Ca(2+) influx. Furthermore, treatment with an intracellular Ca(2+) chelator (BAPTA-AM) or a selective calmodulin antagonist (W7) markedly decreased PMA-induced MMP-9 secretion and cell migration, as well as activation of ERK and JNK/AP-1.


CONCLUSIONS
Metformin inhibited PMA-induced invasion and migration of human fibrosarcoma cells via Ca(2+)-dependent PKCalpha/ERK and JNK/AP-1-signalling pathways. Metformin therefore has the potential to be a potent anti-cancer drug in therapeutic strategies for fibrosarcoma metastasis.
Hwang
Yong P
YP
Department of Toxicology, College of Pharmacy, Chungnam National University, Daejeon, Korea.
Jeong
Hye G
HG
D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D008687:Metformin / Q000008:administration & dosage* / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009361:Neoplasm Invasiveness / Q000517:prevention & control; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013755:Tetradecanoylphorbol Acetate / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000096:biosynthesis*
D018808:Transcription Factor AP-1; D008687:Metformin; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D020780:Matrix Metalloproteinase 9; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium