MIIP inhibits clear cell renal cell carcinoma proliferation and angiogenesis via negative modulation of the HIF-2α-CYR61 axis
Authors:   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi&, Yan Fengqi ,   #x2019,   an 710032, China,   Department of Urology, Tang Du Hospital, the Fourth Military Medical University, Xi&,   #x2019,   an 710038, China, Wang Qinhao ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Xia Mingyuan ,   Department of Urology, Tang Du Hospital, the Fourth Military Medical University, Xi’an 710038, China, Ru Yi ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Hu Wei ,   Department of Urology, Tang Du Hospital, the Fourth Military Medical University, Xi’an 710038, China, Yan Guang ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Xiong Xin ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Zhang Mei ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Wang Jiancai ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China, Li Qi ,   Department of Neurosurgery, Xi Jing Hospital, the Fourth Military Medical University, Xi’an 710032, China, Zhang Bo ,   Department of Urology, Tang Du Hospital, the Fourth Military Medical University, Xi’an 710038, China, Wang He ,   Department of Urology, Tang Du Hospital, the Fourth Military Medical University, Xi’an 710038, China, Lin Wei ,   Department of Neurosurgery, Xi Jing Hospital, the Fourth Military Medical University, Xi’an 710032, China, Wu Guojun ,   Urology and Nephrology Hospital, Xi’an People’s Hospital, Xi’an 710100, China, Li Xia ,   State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, the Fourth Military Medical University, Xi’an 710032, China
Published: February 2022

Objective: In various cancers, migration and invasion inhibitory protein (MIIP) is expressed at low level and is involved in cancer pathogenesis. Herein, we sought to explore the function of MIIP in clear cell renal cell carcinoma (ccRCC). Methods: CCK-8, colony formation, cell cycle, and endothelial cell tube formation assays were performed to evaluate the roles of MIIP in ccRCC proliferation and angiogenesis. To explore the underlying mechanism, we conducted RNA-sequencing, GSEA, qRT-PCR, Western blot, ELISA, cell transfection, coimmunoprecipitation, and ubiquitination assays in ccRCC cell lines. Furthermore, xenograft tumor growth in nude mice, and Ki-67 and CD31 staining in xenograft tissues were examined. Finally, the association of MIIP expression with clinical pathology and the expression status of HIF-2α and cysteine-rich 61 (CYR61) were further analyzed in human RCC tissues through Western blot and immunohistochemistry. Results: Both in vitro and in vivo functional experiments indicated that forced expression of MIIP inhibited ccRCC proliferation and angiogenesis, whereas silencing MIIP either in normal HK-2 cells or in ccRCC cells had the opposite effect (P < 0.05). Mechanistically, CYR61 was identified as a gene significantly downregulated by MIIP overexpression, and was required for the suppressive role of MIIP in ccRCC. MIIP was found to promote HSP90 acetylation and thus impair its chaperone function toward HIF-2α. Consequently, RACK1 binds HIF-2α and causes its ubiquitination and proteasomal degradation, thus decreasing the transcription of its target, CYR61. Finally, analyses of clinical samples demonstrated that MIIP is significantly downregulated in cancer vs. normal tissues in RCC cases, and its expression is negatively associated with histological grade, metastasis, the prognosis of patients with RCC, and the expression of HIF-2α and CYR61 (P < 0.05). Conclusions: MIIP is a novel tumor suppressor in ccRCC via negative regulation of HIF-2α-CYR61 axis.