title: Sustained Mutant KIT Activation in the Golgi Complex Is Mediated by PKC-θ in Gastrointestinal Stromal Tumors.
abstract: OBJECTIVE
  Tumorigenesis of gastrointestinal stromal tumors (GIST) is driven by gain-of-function mutations in the KIT gene, which result in overexpression of activated mutant KIT proteins (MT-KIT). However, the mechanism of MT-KIT overexpression is poorly understood.
  
  
  METHODS
  By protein expression analysis and immunofluorescent microscopic analysis, we determine the stability and localization of MT-KIT in four GIST cell lines with different mutations and HeLa cells transfected with mutant KIT model vectors. We also used 154 human GIST tissues to analyze the relationship between the expression of PKC-θ and MT-KITs, and correlations between PKC-θ overexpression and clinicopathological parameters.
  
  
  RESULTS
  We report that four different MT-KIT proteins are intrinsically less stable than wild-type KIT due to proteasome-mediated degradation and abnormally localized to the endoplasmic reticulum (ER) or the Golgi complex. By screening a MT-KIT-stabilizing factor, we find that PKC-θ is strongly and exclusively expressed in GISTs and interacts with intracellular MT-KIT to promote its stabilization by increased retention in the Golgi complex. In addition, Western blotting analysis using 50 GIST samples shows strong correlation between PKC-θ and MT-KIT expression (correlation coefficient = 0.682, P < 0.000001). Immunohistochemical analysis using 154 GISTs further demonstrates that PKC-θ overexpression significantly correlates with several clinicopathological parameters such as high tumor grade, frequent recurrence/metastasis, and poor patient survival.
  
  
  CONCLUSIONS
  Our findings suggest that sustained MT-KIT overexpression through PKC-θ-mediated stabilization in the Golgi contributes to GIST progression and provides a rationale for anti-PKC-θ therapy in GISTs. Clin Cancer Res; 23(3); 845-56. ©2016 AACR.
authors.affiliation: Department of Pathology and Brain Korea 21 PLUS Projects for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Won Kyu
authors.initials: WK
authors.lastname: Kim
authors.affiliation: Department of Pathology and Brain Korea 21 PLUS Projects for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: SeongJu
authors.initials: S
authors.lastname: Yun
authors.affiliation: Department of Pathology and Brain Korea 21 PLUS Projects for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Cheol Keun
authors.initials: CK
authors.lastname: Park
authors.affiliation: Sarcoma Center, West German Cancer Center, University Hospital Essen, University Duisburg-Essen, Essen, Germany and German Cancer Consortium (DKTK), Heidelberg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bauer
authors.affiliation: Department of Pharmacology, Pharmacogenomic Research Center for Membrane Transporters, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Jiyoon
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Pharmacology, Pharmacogenomic Research Center for Membrane Transporters, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Min Goo
authors.initials: MG
authors.lastname: Lee
authors.affiliation: Department of Pathology and Brain Korea 21 PLUS Projects for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea. hkyonsei@yuhs.ac.
authors.forename: Hoguen
authors.initials: H
authors.lastname: Kim
mesh_terms: D000818:Animals; D002460:Cell Line; D018572:Disease-Free Survival; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004789:Enzyme Activation; D005770:Gastrointestinal Neoplasms / Q000201:enzymology* / Q000401:mortality / Q000473:pathology; D046152:Gastrointestinal Stromal Tumors / Q000201:enzymology* / Q000401:mortality / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic; D006056:Golgi Apparatus / Q000201:enzymology*; D006801:Humans; D053208:Kaplan-Meier Estimate; D009154:Mutation; D009363:Neoplasm Proteins / Q000235:genetics* / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D000074121:Protein Kinase C-theta / Q000502:physiology*; D059748:Proteolysis; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D019009:Proto-Oncogene Proteins c-kit; D000074121:Protein Kinase C-theta; D046988:Proteasome Endopeptidase Complex