Metformin inhibits the radiation-induced invasive phenotype of esophageal squamous cell carcinoma.
Esophageal cancer is one of the most aggressive tumor types because of its invasiveness and metastatic potential. Several reports have described an association between increased invasiveness after ionizing radiation (IR) treatment and epithelial-to-mesenchymal transition (EMT). The biguanide metformin is reported to prevent transforming growth factor-β (TGF-β)-induced EMT and proliferation of cancer. This study examined whether IR induces EMT and promotes the invasive potential of TE-9 esophageal squamous cell carcinoma cells and the effect of metformin on IR-induced EMT. After IR exposure, TE-9 cells showed a spindle-shaped morphology and lost cell-cell adhesion. Immunoblotting showed that IR induced expression of mesenchymal markers (vimentin and N-cadherin), transcription factors (Slug, Snail, and Twist), and matrix metalloproteinases. A scratch wound assay and Matrigel invasion assay showed that IR enhanced the invasive potential and migratory capacity of TE-9 cells. Expression of hypoxia-related factor-1α and TGF-β was increased after IR. IR also induced phosphorylation of Smad2 and Smad3. Metformin inhibited radiation-induced EMT-like morphological changes, and enhanced invasion and migration of TE-9 cells. Metformin inhibited IR-induced phosphorylation of Smad2 and Smad3. Although phosphorylation of AMP-activated protein kinase was enhanced by IR and metformin, phosphorylation of mammalian target of rapamycin was enhanced by IR and suppressed by metformin. These results indicated that metformin suppressed IR-induced EMT via suppression of the TGF-β-Smad phosphorylation pathway, and a part of the non-Smad pathway. Metformin might be useful to prevent IR-induced invasion and metastasis of esophageal squamous cell carcinoma.
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Akira
A
Nakayama
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Itasu
I
Ninomiya
Center for Biomedical Research and Education, School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Shinichi
S
Harada
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Tomoya
T
Tsukada
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Koichi
K
Okamoto
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Shinichi
S
Nakanuma
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Seisho
S
Sakai
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Isamu
I
Makino
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Jun
J
Kinoshita
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Hironori
H
Hayashi
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Katsunobu
K
Oyama
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Tomoharu
T
Miyashita
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Hidehiro
H
Tajima
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Hiroyuki
H
Takamura
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Sachio
S
Fushida
Department of Gastroenterological Surgery, Division of Cancer Medicine, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8641, Japan.
Tetsuo
T
Ohta
D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion / Q000187:drug effects / Q000528:radiation effects; D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects* / Q000528:radiation effects; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008687:Metformin / Q000494:pharmacology*; D009361:Neoplasm Invasiveness; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014965:X-Rays
D007004:Hypoglycemic Agents; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D008687:Metformin