title: Knockdown of RPL9 expression inhibits colorectal carcinoma growth via the inactivation of Id-1/NF-κB signaling axis.
abstract: Ribosomal protein L9 (RPL9), a component of the 60S subunit for protein synthesis, is upregulated in human colorectal cancer. In the present study, we investigated whether RPL9 gained extraribosomal function during tumorigenesis and whether targeting of RPL9 with small interfering (si) RNA could alter the course of colorectal cancer progression. Our results showed that siRNA knockdown of RPL9 suppresses colorectal cancer (CRC) cell growth and long-term colony formation through an increase in sub-G1 cell population and a strong induction of apoptotic cell death. To obtain insights into the molecular changes in response to RPL9 knockdown, global changes in gene expression were examined using RNA sequencing. It revealed that RPL9-specific knockdown led to dysregulation of 918 genes in HCT116 and 3178 genes in HT29 cells. Among these, 296 genes showed same directional regulation (128 upregulated and 168 downregulated genes) and were considered as a common RPL9 knockdown signature. Particularly, we found through a network analysis that Id-1, which is functionally associated with activation of NF-κB and cell survival, was commonly downregulated. Subsequent western blot analysis affirmed that RPL9 silencing induced the decrease in the levels of Id-1 and phosphorylated IκBα in both HCT116 and HT29 cells. Also, the same condition decreased the levels of PARP-1 and pro-caspase-3, accelerating apoptosis. Furthermore, inhibition of RPL9 expression significantly suppressed the growth of human CRC xenografts in nude mice. These findings indicate that the function of RPL9 is correlated with Id-1/NF-κB signaling axis and suggest that targeting RPL9 could be an attractive option for molecular therapy of colorectal cancer.
authors.affiliation: Department of Molecular Medicine, Keimyung University School of Medicine, Daegu, Republic of Korea.
authors.forename: In Hye
authors.initials: IH
authors.lastname: Baik
authors.affiliation: Myunggok Eye Research Institute, Kim's Eye Hospital, Konyang University College of Medicine, Seoul, Republic of Korea.
authors.forename: Guk-Heui
authors.initials: GH
authors.lastname: Jo
authors.affiliation: Severance Biomedical Science Institute, Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Daekwan
authors.initials: D
authors.lastname: Seo
authors.affiliation: Department of Molecular Medicine, Keimyung University School of Medicine, Daegu, Republic of Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Ko
authors.affiliation: Department of Obstetrics and Gynecology, Keimyung University School of Medicine, Daegu, Republic of Korea.
authors.forename: Chi Heum
authors.initials: CH
authors.lastname: Cho
authors.affiliation: Department of Pharmacology and Brain Korea 21 Project for Medical Sciences, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Min Goo
authors.initials: MG
authors.lastname: Lee
authors.affiliation: Department of Molecular Medicine, Keimyung University School of Medicine, Daegu, Republic of Korea.
authors.forename: Yun-Han
authors.initials: YH
authors.lastname: Lee
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002453:Cell Cycle; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D051798:Inhibitor of Differentiation Protein 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: C497453:ID1 protein, human; D051798:Inhibitor of Differentiation Protein 1; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012269:Ribosomal Proteins; C049650:ribosomal protein L9