Hypoxia-induced epithelial-mesenchymal transition is regulated by phosphorylation of GSK3-β via PI3 K/Akt signaling in oral squamous cell carcinoma.
OBJECTIVE
Epithelial-mesenchymal transition (EMT) plays an important role in cancer invasion and metastasis induced by hypoxia. Here, we examined whether phosphorylation of GSK3-β via phosphoinositide 3-kinase (PI3 K)/Akt signaling is involved in enhancing the hypoxia-induced EMT in oral squamous cell carcinoma (OSCC).


METHODS
Experiments were performed in OSCC cell lines (HSC-2, HSC-3, HSC-4, SAS, and HO-1-U-1) under normoxic or hypoxic conditions. The EMT was assessed by Matrigel invasion assays and wound healing assays. OSCC cell lines (HSC-2 and HSC-4) overexpressing hypoxia-inducible factor (HIF)-1α were established to examine the effects of HIF-1α on EMT-related factors. Immunohistochemical staining was performed to examine phosphorylation of GSK3-β in 33 cases of tongue squamous cell carcinoma.


RESULTS
Under hypoxic conditions, OSCC cell lines exhibited HIF-1α expression and showed evidence of the EMT. In cells overexpressing HIF-1α, the levels of phospho-Akt and phospho-GSK3-β were increased, resulting in induction of the EMT. Inhibition of GSK3-β phosphorylation suppressed these effects. Moreover, the intensity of pGSK3-β staining was significantly increased with cN stage and cTNM stage in patients with tongue squamous cell carcinoma.


CONCLUSIONS
Our data showed that the hypoxia-induced EMT in OSCC was enhanced by GSK3-β phosphorylation, suggesting that GSK3-β may be important in the invasion and metastasis of OSCC.
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Takeshi
T
Kaneko
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan. Electronic address: Dehari@sapmed.ac.jp.
Hironari
H
Dehari
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Takanori
T
Sasaki
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Tomohiro
T
Igarashi
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Kazuhiro
K
Ogi
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Jun-Ya
JY
Okamoto
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Mayumi
M
Kawata
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Jun-Ichi
JI
Kobayashi
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Akihiro
A
Miyazaki
Division of Oral and Maxillofacial Surgery, Naha City Hospital, Naha, Japan.
Kenji
K
Nakamori
Department of Oral Surgery, Sapporo Medical University School of Medicine, Sapporo, Japan.
Hiroyoshi
H
Hiratsuka
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000201:enzymology* / Q000473:pathology; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013194:Staining and Labeling; D014062:Tongue Neoplasms / Q000201:enzymology* / Q000473:pathology
D019869:Phosphatidylinositol 3-Kinases; D038362:Glycogen Synthase Kinase 3