title: Inhibition of MKK7-JNK by the TOR signaling pathway regulator-like protein contributes to resistance of HCC cells to TRAIL-induced apoptosis.
abstract: OBJECTIVE
  The TOR signaling pathway regulator-like (TIPRL) protein, the mammalian ortholog of yeast TIP41, was identified in an expression profiling screen for factors that regulate human liver carcinogenesis. We investigated the role of human TIPRL protein in hepatocellular carcinoma (HCC).
  
  
  METHODS
  We measured the level of TIPRL in HCC and adjacent nontumor tissues from patients. We used small interfering RNAs and zebrafish to study the function of TIPRL. We used annexin V propidium iodide staining and immunoblot analyses to measure apoptosis and activation of apoptotic signaling pathways. We used confocal microscopy, coimmunoprecipitation, and glutathione-S transferase pull-down analyses to determine interactions among mitogen-activated protein kinase kinase 7 (MKK7 or MAP2K7), TIPRL, and the protein phosphatase type 2A (PP2Ac). We studied the effects of TIPRL in tumor xenografts in mice.
  
  
  RESULTS
  Levels of TIPRL were higher in HCC tissues and cell lines than nontumor tissues and primary hepatocytes. Knockdown of tiprl expression in zebrafish led to large amounts of apoptosis throughout the embryos. Incubation of HCC cells, but not primary human hepatocytes, with small interfering RNA against TIPRL (siTIPRL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) caused prolonged activation (phosphorylation) of MKK7 and c-Jun N-terminal kinase (JNK) and led to apoptosis, indicated by cleavage of procaspase-8,-3 and of poly-(adenosine diphosphate-ribose) polymerase. TIPRL bound to MKK7 and PP2Ac and promoted the interaction between MKK7 and PP2Ac. In mice, injection of HCC xenograft tumors with siTIPRL and TRAIL led to tumor apoptosis and regression.
  
  
  CONCLUSIONS
  TIPRL is highly up-regulated in human HCC samples and cell lines, compared with noncancerous liver tissues. TIPRL prevents prolonged activation of MKK7 and JNK and TRAIL-induced apoptosis by mediating the interaction between MKK7 and PP2Ac.
authors: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea; Cardiovascular and Metabolic Disease Center, Inje University, Busan, South Korea.
authors: In Sung
authors: IS
authors: Song
authors: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea; Department of Functional Genomics, University of Science and Technology, Daejeon, South Korea.
authors: Soo Young
authors: SY
authors: Jun
authors: Department of Functional Genomics, University of Science and Technology, Daejeon, South Korea; Renal Division, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors: Hee-Jun
authors: HJ
authors: Na
authors: Department of Biology, Chungnam National University, Daejeon, South Korea.
authors: Hyun-Taek
authors: HT
authors: Kim
authors: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors: So Young
authors: SY
authors: Jung
authors: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors: Ga Hee
authors: GH
authors: Ha
authors: Department of Functional Genomics, University of Science and Technology, Daejeon, South Korea; Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors: Young-Ho
authors: YH
authors: Park
authors: Department of Pathology, School of Medicine, Chungnam National University, Daejeon, South Korea.
authors: Liang Zhe
authors: LZ
authors: Long
authors: Department of Functional Genomics, University of Science and Technology, Daejeon, South Korea; Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors: Dae-Yeul
authors: DY
authors: Yu
authors: Department of Pathology, School of Medicine, Chungnam National University, Daejeon, South Korea.
authors: Jin-Man
authors: JM
authors: Kim
authors: Department of Pathology, Eulji University School of Medicine, Daejeon, South Korea.
authors: Joo Heon
authors: JH
authors: Kim
authors: Daejeon-KRIBB-FHCRC Research Cooperation Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors: Jeong-Heon
authors: JH
authors: Ko
authors: Department of Biology, Chungnam National University, Daejeon, South Korea. Electronic address: zebrakim@cnu.ac.kr.
authors: Cheol-Hee
authors: CH
authors: Kim
authors: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea; Department of Functional Genomics, University of Science and Technology, Daejeon, South Korea. Electronic address: nskim37@kribb.re.kr.
authors: Nam-Soon
authors: NS
authors: Kim
mesh_terms: D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D005260:Female; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D048688:MAP Kinase Kinase 7 / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D054648:Protein Phosphatase 2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D015854:Up-Regulation; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C577326:TIPRL protein, human; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D048688:MAP Kinase Kinase 7; C482569:MAP2K7 protein, human; D054648:Protein Phosphatase 2