title: Ubiquitin ligase Cbl-b represses IGF-I-induced epithelial mesenchymal transition via ZEB2 and microRNA-200c regulation in gastric cancer cells.
abstract: BACKGROUND
  Insulin-like growth factor I (IGF-I) can induce epithelial mesenchymal transition (EMT) in many epithelial tumors; however, the molecular mechanism by which this occurs is not clearly understood. Additionally, little is known about the involvement of IGF-I in gastric cancer.
  
  
  METHODS
  Two gastric cancer cell lines were treated with IGF-I to induce EMT and levels of transcription factor ZEB2 and microRNA-200c (miR-200c) were measured. Cells were treated with Akt/ERK inhibitors to investigate the role of these pathways in IGF-I-mediated EMT. Transfection of shRNA plasmids was used to silence the ubiquitin ligase Cbl-b to assess its involvement in this process. The relationship between IGF-IR and Cbl-b expression, and the effect of IGF-IR and Cbl-b on metastasis were analyzed in primary gastric adenocarcinoma patients.
  
  
  RESULTS
  IGF-I-induced gastric cancer cell EMT was accompanied by ZEB2 up-regulation. Furthermore, both Akt/ERK inhibitors and knockdown of Akt/ERK gene reversed IGF-I-induced ZEB2 up-regulation and EMT through up-regulation of miR-200c, suggesting the involvement of an Akt/ERK-miR-200c-ZEB2 axis in IGF-I-induced EMT. The ubiquitin ligase Cbl-b also ubiquitinated and degraded IGF-IR and inhibited the Akt/ERK-miR-200c-ZEB2 axis, leading to the repression of IGF-I-induced EMT. There was a significant negative correlation between the expression of IGF-IR and Cbl-b in gastric cancer patient tissues (r = -0.265, p < 0.05). More of patients with IGF-IR-positive expression and Cbl-b-negative expression were with lymph node metastasis (p < 0.001).
  
  
  CONCLUSIONS
  Together, these findings demonstrate that the ubiquitin ligase Cbl-b represses IGF-I-induced EMT, likely through targeting IGF-IR for degradation and further inhibiting the Akt/ERK-miR-200c-ZEB2 axis in gastric cancer cells.
authors.forename: Heming
authors.initials: H
authors.lastname: Li
authors.forename: Ling
authors.initials: L
authors.lastname: Xu
authors.forename: Ce
authors.initials: C
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
authors.forename: Yanju
authors.initials: Y
authors.lastname: Ma
authors.forename: Huachuan
authors.initials: H
authors.lastname: Zheng
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ruoyu
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Medical Oncology, the First Hospital of China Medical University, NO,155, North Nanjing Street, Heping District, Shenyang 110001, China. cmuliuyunpeng@hotmail.com.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiujuan
authors.initials: X
authors.lastname: Qu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000368:Aged; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D008207:Lymphatic Metastasis; D008297:Male; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009367:Neoplasm Staging; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000074165:Zinc Finger E-box Binding Homeobox 2
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018398:Homeodomain Proteins; C533896:MIRN200 microRNA, human; D035683:MicroRNAs; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D012097:Repressor Proteins; C492363:ZEB2 protein, human; D000074165:Zinc Finger E-box Binding Homeobox 2; D007334:Insulin-Like Growth Factor I; C492211:CBLB protein, human; D050721:Proto-Oncogene Proteins c-cbl; D051057:Proto-Oncogene Proteins c-akt; D048052:Mitogen-Activated Protein Kinase 3