title: Metformin inhibits growth and decreases resistance to anoikis in medullary thyroid cancer cells.
abstract: Medullary thyroid cancer (MTC) is associated with activation of mammalian target of rapamycin (mTOR) signaling pathways. Recent studies showed that the antidiabetic agent metformin decreases proliferation of cancer cells through 5'-AMP-activated protein kinase (AMPK)-dependent inhibition of mTOR. In the current study, we assessed the effect of metformin on MTC cells. For this purpose, we determined growth, viability, migration, and resistance to anoikis assays using two MTC-derived cell lines (TT and MZ-CRC-1). Expressions of molecular targets of metformin were examined in MTC cell lines and in 14 human MTC tissue samples. We found that metformin inhibited growth and decreased expression of cyclin D1 in MTC cells. Treatment with metformin was associated with inhibition of mTOR/p70S6K/pS6 signaling and downregulation of pERK in both TT and MZ-CRC-1 cells. Metformin had no significant effects on pAKT in the cell lines examined. Metformin-inducible AMPK activation was noted only in TT cells. Treatment with AMPK inhibitor (compound C) or AMPK silencing did not prevent growth inhibitory effects of metformin in TT cells. Metformin had no effect on MTC cell migration but reduced the ability of cells to form multicellular spheroids in nonadherent conditions. Immunostaining of human MTC showed over-expression of cyclin D1 in all tumors compared with corresponding normal tissue. Activation of mTOR/p70S6K was detected in 8/14 (57.1%) examined tumors. Together, these findings indicate that growth inhibitory effects in MTC cells are associated with downregulation of both mTOR/6SK and pERK signaling pathways. Expression of metformin's molecular targets in human MTC cells suggests its potential utility for the treatment of MTC in patients.
authors.affiliation: Department of Pediatrics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814-4712, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Klubo-Gwiezdzinska
authors.forename: Kirk
authors.initials: K
authors.lastname: Jensen
authors.forename: John
authors.initials: J
authors.lastname: Costello
authors.forename: Aneeta
authors.initials: A
authors.lastname: Patel
authors.forename: Victoria
authors.initials: V
authors.lastname: Hoperia
authors.forename: Andrew
authors.initials: A
authors.lastname: Bauer
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Burman
authors.forename: Leonard
authors.initials: L
authors.lastname: Wartofsky
authors.forename: Vasyl
authors.initials: V
authors.lastname: Vasko
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D023102:Anoikis / Q000187:drug effects; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018278:Carcinoma, Neuroendocrine; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D008687:Metformin / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D008687:Metformin; D011494:Protein Kinases; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases