title: Downregulation of receptor for activated C-kinase 1 (RACK1) suppresses tumor growth by inhibiting tumor cell proliferation and tumor-associated angiogenesis.
abstract: By behaving as molecular hubs, scaffold proteins can assemble a large number of signaling molecules and organize complicated intracellular signaling networks in time and space. Owing to their crucial role in mediating intracellular signaling related to tumor cell growth and migration, recent studies have highlighted the relevance of scaffold proteins in human cancers and indicated that interfering with their expression and/or their ability to bind effector proteins can inhibit cancer progression. Here, we show that receptor for activated C-kinase 1 (RACK1), a ubiquitously expressed scaffolding protein, plays a crucial regulatory role in tumor growth. Using an RNA silencing approach, we found that downregulation of RACK1 expression in HeLa and A673 tumor cells markedly suppressed the proliferation and invasion of these cells in vitro and tumor development in vivo. Consequently, we found that significant suppression of constitutive phosphorylation of Akt and MAPK by RACK1 silencing may contribute to the inhibition of tumor growth. Moreover, RACK1 silencing significantly attenuated tumor-associated angiogenesis by, at least in part, inhibiting the expression of two critical angiogenic factors, namely vascular endothelial growth factor-B and fibroblast growth factor 2. The results of the present study show that RACK1 is a potent enhancer of tumor growth and, thus, a potential anti-cancer therapeutic target.
authors.affiliation: Department of Molecular Oncology, Graduate School of Medicine and Dentistry, Tokyo Dental and Medical University, Tokyo, Japan.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Osawa
authors.forename: Rika
authors.initials: R
authors.lastname: Tsuchida
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Yuasa
authors.forename: Masabumi
authors.initials: M
authors.lastname: Shibuya
mesh_terms: D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D045744:Cell Line, Tumor; D015536:Down-Regulation; D019204:GTP-Binding Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000502:physiology*; D009389:Neovascularization, Pathologic; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000502:physiology*; D012208:Rhabdomyosarcoma / Q000473:pathology; D015398:Signal Transduction; D014410:Tumor Stem Cell Assay; D042561:Vascular Endothelial Growth Factor B; D023041:Xenograft Model Antitumor Assays
chemical_list: D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D034741:RNA, Small Interfering; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; C467485:VEGFB protein, human; D042561:Vascular Endothelial Growth Factor B; D019204:GTP-Binding Proteins