title: Hypoxia inducible factor 1α and hypoxia inducible factor 2α play distinct and functionally overlapping roles in oral squamous cell carcinoma.
abstract: 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.
authors.affiliation: West China Hospital of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Gui-quan
authors.initials: GQ
authors.lastname: Zhu
authors.forename: Ya-ling
authors.initials: YL
authors.lastname: Tang
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Zheng
authors.forename: Jian
authors.initials: J
authors.lastname: Jiang
authors.forename: Xiao-yu
authors.initials: XY
authors.lastname: Li
authors.forename: Si-xiu
authors.initials: SX
authors.lastname: Chen
authors.forename: Xin-hua
authors.initials: XH
authors.lastname: Liang
mesh_terms: 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
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human