Hypoxia inducible factor 1α and hypoxia inducible factor 2α play distinct and functionally overlapping roles in oral squamous cell carcinoma.
OBJECTIVE
This study aimed to investigate the functional difference between hypoxia inducible factor (HIF)-1α and HIF-2α in oral squamous cell carcinomas (OSCC).


METHODS
We evaluated the correlations between HIF-1α and HIF-2α expression and the clinical-pathologic characteristics of 97 patients with OSCC by immunohistochemical staining. OSCC cell lines transfected with lentivirus encoding short hairpin RNA against HIF-1α/2α were used to investigate the HIF-1α/2α-dependent target genes. Xenograft tumors in nude mice were established using cells affected by lentivirus, and tumor growth, angiogenesis, proliferation, and apoptosis were measured.


RESULTS
HIF-1α expression was significantly associated with T stage (P = 0.004), lymph node involvement (P = 0.006), histologic differentiation (P = 0.013), and microvessel density (P = 0.014), whereas that of HIF-2α was associated with T stage (P = 0.011) and microvessel density (P = 0.005). Patients with positive HIF-1α nuclear staining had a significantly worse overall survival (P < 0.001) and disease-free survival (P < 0.001) than those with negative HIF-1α staining. When OSCC cells were cultured at 5% O(2), only HIF-2α contributed to the expression of vascular endothelial growth factor. At 1% O(2), vascular endothelial growth factor was regulated by both HIF-1α and HIF-2α, but glucose transporter 1, carbonic anhydrase 9, and urokinase-type plasminogen activator receptor were regulated by HIF-1α rather than by HIF-2α. Knocking down HIF-1α or HIF-2α individually inhibited the xenograft tumor angiogenesis and growth, and knocking them down simultaneously revealed a better inhibitory effect than knocking down either unit alone.


CONCLUSIONS
HIF-1α and HIF-2α correlated with different clinical-pathologic parameters, stabilized at different oxygen levels, and regulated different genes in OSCC. However, both HIF-1α and HIF-2α showed promoting roles in tumor angiogenesis and growth, and therapeutic outcome may benefit from combined targeting of HIF-1α and HIF-2α.
Zhu
Gui-quan
GQ
West China Hospital of Stomatology, Sichuan University, Chengdu, China.
Tang
Ya-ling
YL
Li
Ling
L
Zheng
Min
M
Jiang
Jian
J
Li
Xiao-yu
XY
Chen
Si-xiu
SX
Liang
Xin-hua
XH
D000328:Adult; D000368:Aged; D000818:Animals; D017209:Apoptosis; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D049109:Cell Proliferation; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy; D009389:Neovascularization, Pathologic; D011379:Prognosis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human