title: Reciprocal regulation of hypoxia-inducible factor 2α and GLI1 expression associated with the radioresistance of renal cell carcinoma.
abstract: OBJECTIVE
  Renal cell carcinoma (RCC) is often considered a radioresistant tumor, but the molecular mechanism underlying its radioresistance is poorly understood. This study explored the roles of hypoxia-inducible factor 2α (HIF2α) and sonic hedgehog (SHH)-GLI1 signaling in mediating the radioresistance of RCC cells and to unveil the interaction between these 2 signaling pathways.
  
  
  METHODS
  The activities of SHH-GLI1 signaling pathway under normoxia and hypoxia in RCC cells were examined by real-time polymerase chain reaction, Western blot, and luciferase reporter assay. The expression of HIF2α and GLI1 in RCC patients was examined by immunohistochemistry, and their correlation was analyzed. Furthermore, RCC cells were treated with HIF2α-specific shRNA (sh-HIF2α), GLI1 inhibitor GANT61, or a combination to determine the effect of ionizing radiation (IR) on RCC cells based on clonogenic assay and double-strand break repair assay.
  
  
  RESULTS
  RCC cells exhibited elevated SHH-GLI1 activities under hypoxia, which was mediated by HIF2α. Hypoxia induced GLI1 activation through SMO-independent pathways that could be ablated by PI3K inhibitor or MEK inhibitor. Remarkably, the SHH-GLI1 pathway also upregulated HIF2α expression in normoxia. Apparently, there was a positive correlation between HIF2α and GLI1 expression in RCC patients. The combination of sh-HIF2α and GLI1 inhibitor significantly sensitized RCC cells to IR.
  
  
  CONCLUSIONS
  Cross-talk between the HIF2α and SHH-GLI1 pathways was demonstrated in RCC. Cotargeting these 2 pathways, significantly sensitizing RCC cells to IR, provides a novel strategy for RCC treatment.
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China; Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Kaijie
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Urology, Shandong Provincial Hospital affiliated with Shandong University, Ji'nan, China.
authors.forename: Dexuan
authors.initials: D
authors.lastname: Gao
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Guodong
authors.initials: G
authors.lastname: Zhu
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Dapeng
authors.initials: D
authors.lastname: Wu
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Xinyang
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Yule
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Yuefeng
authors.initials: Y
authors.lastname: Du
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Zhenkun
authors.initials: Z
authors.lastname: Ma
authors.affiliation: Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Craig
authors.initials: C
authors.lastname: Authement
authors.affiliation: Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Saha
authors.affiliation: Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: jt.hsieh@utsouthwestern.edu.
authors.forename: Jer-Tsong
authors.initials: JT
authors.lastname: Hsieh
authors.affiliation: Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China. Electronic address: dalinhe@yahoo.com.
authors.forename: Dalin
authors.initials: D
authors.lastname: He
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002292:Carcinoma, Renal Cell / Q000378:metabolism* / Q000532:radiotherapy*; D015687:Cell Hypoxia / Q000502:physiology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D049410:Luciferases, Renilla / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D011836:Radiation Tolerance / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014410:Tumor Stem Cell Assay; D015854:Up-Regulation; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D049410:Luciferases, Renilla; D009363:Neoplasm Proteins; D011725:Pyridines; D011743:Pyrimidines; D014157:Transcription Factors; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000071676:Zinc Finger Protein GLI1; D000099162:Endothelial PAS Domain-Containing Protein 1; C551027:GANT 61; C400551:GLI1 protein, human