title: Inhibition of endoplasmic reticulum chaperone protein glucose-regulated protein 78 potentiates anti-angiogenic therapy in renal cell carcinoma through inactivation of the PERK/eIF2α pathway.
abstract: Tumor microenvironments are characterized by decreased oxygen and nutrition due to the rapid and progressive nature of tumors and also stresses induced by several anti-tumor therapies. These intense cell stressors trigger a protective cell survival mechanism heralded by the unfolded protein response (UPR). The UPR is induced by an accumulation of unfolded proteins in the endoplasmic reticulum (ER) following cell starvation. Although the ER stress response is implicated in cytoprotection, its precise role during anti-angiogenic therapy remains unclear. One of the major proteins involved in ER stress is glucose-regulated protein 78 (GRP78), which binds to unfolded proteins and dissociates from membrane-bound ER stress sensors. To determine the role of ER stress responses during anti-angiogenic therapy and the potential role of GRP78 in combined therapy in renal cell carcinoma (RCC), we used GRP78 overexpressing or knockdown RCC cells under hypoxic or hypoglycemic conditions in vitro and in animal models treated with sunitinib. Here, we report that GRP78 plays a crucial role in protecting RCC cells from hypoxic and hypoglycemic stress induced by anti-angiogenic therapy. Knockdown of GRP78 using siRNA inhibited cancer cell survival and induced apoptosis in RCC cells in vitro and also resulted in ER stress-induced apoptosis and hypoxic/hypoglycemic stress-induced apoptosis by inactivating the PERK/eIF-2α pathway. Finally, GRP78 knockdown showed potent suppression of tumor growth and enhanced the antitumor effect of sunitinib in RCC xenografts. Our findings suggest that GRP78 may serve as a novel therapeutic target in combination with anti-angiogenic therapy for the management of RCC.
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.|Department of Urology and Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Kyung Seok
authors.initials: KS
authors.lastname: Han
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Pater A
authors.initials: PA
authors.lastname: Raven
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Ladan
authors.initials: L
authors.lastname: Fazli
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Frees
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Ettinger
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Ki Chung
authors.initials: KC
authors.lastname: Park
authors.affiliation: Department of Urology and Urological Science Institute, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Hong
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Martin E
authors.initials: ME
authors.lastname: Gleave
authors.affiliation: Vancouver Prostate Centre and Department of Urologic Science, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Alan I
authors.initials: AI
authors.lastname: So
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000473:pathology*; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D055785:Gene Knockdown Techniques; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007211:Indoles / Q000494:pharmacology; D007680:Kidney Neoplasms / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D018613:Microscopy, Confocal; D011758:Pyrroles / Q000494:pharmacology; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological; D000077210:Sunitinib; D014162:Transfection; D023041:Xenograft Model Antitumor Assays; D019892:eIF-2 Kinase / Q000378:metabolism*
chemical_list: D020533:Angiogenesis Inhibitors; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D007211:Indoles; D011758:Pyrroles; D034741:RNA, Small Interfering; C460640:EIF2AK3 protein, human; D019892:eIF-2 Kinase; D000077210:Sunitinib
keywords: endoplasmic reticulum response; glucose-regulated protein 78; hypoxia; renal cell carcinoma; sunitinib