Jiancheng Zhou1, Kaijie Wu2, Dexuan Gao3, Guodong Zhu2, Dapeng Wu2, Xinyang Wang2, Yule Chen2, Yuefeng Du2, Wenbin Song2, Zhenkun Ma2, Craig Authement4, Debabrata Saha4, Jer-Tsong Hsieh5, Dalin He6. 1. 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. 2. Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China. 3. Department of Urology, Shandong Provincial Hospital affiliated with Shandong University, Ji'nan, China. 4. Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas. 5. Department of Urology, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas. Electronic address: jt.hsieh@utsouthwestern.edu. 6. Department of Urology, First Affiliated Hospital of Medical School, Xi'an Jiaotong University, Xi'an, China. Electronic address: dalinhe@yahoo.com.
Abstract
PURPOSE: 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 AND MATERIALS: 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.
PURPOSE: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 AND MATERIALS: 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: Tadas K Rimkus; Richard L Carpenter; Sherona Sirkisoon; Dongqin Zhu; Boris C Pasche; Michael D Chan; Glenn J Lesser; Stephen B Tatter; Kounosuke Watabe; Waldemar Debinski; Hui-Wen Lo Journal: Cancer Res Date: 2018-02-20 Impact factor: 12.701