title: Role of microRNA-155 at early stages of hepatocarcinogenesis induced by choline-deficient and amino acid-defined diet in C57BL/6 mice.
abstract: MicroRNAs (miRs) are conserved, small (20-25 nucleotide) noncoding RNAs that negatively regulate expression of messenger RNAs (mRNAs) at the posttranscriptional level. Aberrant expression of certain microRNAs plays a causal role in tumorigenesis. Here, we report identification of hepatic microRNAs that are dysregulated at early stages of feeding C57BL/6 mice choline-deficient and amino acid-defined (CDAA) diet that is known to promote nonalcoholic steatohepatitis (NASH)-induced hepatocarcinogenesis after 84 weeks. Microarray analysis identified 30 hepatic microRNAs that are significantly (P < or = 0.01) altered in mice fed CDAA diet for 6, 18, 32, and 65 weeks compared with those fed choline-sufficient and amino acid-defined (CSAA) diet. Real-time reverse transcription polymerase chain reaction (RT-PCR) analysis demonstrated up-regulation of oncogenic miR-155, miR-221/222, and miR-21 and down-regulation of the most abundant liver-specific miR-122 at early stages of hepatocarcinogenesis. Western blot analysis showed reduced expression of hepatic phosphatase and tensin homolog (PTEN) and CCAAT/enhancer binding protein beta (C/EBPbeta), respective targets of miR-21 and miR-155, in these mice at early stages. DNA binding activity of nuclear factor kappa B (NF-kappaB) that transactivates miR-155 gene was significantly (P = 0.002) elevated in the liver nuclear extract of mice fed CDAA diet. Furthermore, the expression of miR-155, as measured by in situ hybridization and real-time RT-PCR, correlated with diet-induced histopathological changes in the liver. Ectopic expression of miR-155 promoted growth of hepatocellular carcinoma (HCC) cells, whereas its depletion inhibited cell growth. Notably, miR-155 was significantly (P = 0.0004) up-regulated in primary human HCCs with a concomitant decrease (P = 0.02) in C/EBPbeta level compared with matching liver tissues.
  
  
  CONCLUSIONS
  Temporal changes in microRNA profile occur at early stages of CDAA diet-induced hepatocarcinogenesis. Reciprocal regulation of specific oncomirs and their tumor suppressor targets implicate their role in NASH-induced hepatocarcinogenesis and suggest their use in the diagnosis, prognosis, and therapy of liver cancer.
authors.affiliation: Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, OH, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.forename: Sarmila
authors.initials: S
authors.lastname: Majumder
authors.forename: Gerard
authors.initials: G
authors.lastname: Nuovo
authors.forename: Huban
authors.initials: H
authors.lastname: Kutay
authors.forename: Stefano
authors.initials: S
authors.lastname: Volinia
authors.forename: Tushar
authors.initials: T
authors.lastname: Patel
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Schmittgen
authors.forename: Carlo
authors.initials: C
authors.lastname: Croce
authors.forename: Kalpana
authors.initials: K
authors.lastname: Ghoshal
authors.forename: Samson T
authors.initials: ST
authors.lastname: Jacob
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002796:Choline Deficiency / Q000378:metabolism*; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000150:complications*; D006801:Humans; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008113:Liver Neoplasms / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D051059:PTEN Phosphohydrolase / Q000378:metabolism
chemical_list: D000596:Amino Acids; C452880:Atp5md protein, rat; D022782:CCAAT-Enhancer-Binding Protein-beta; C524942:MIRN155 microRNA, human; D008565:Membrane Proteins; D035683:MicroRNAs; C544354:Mirn122 microRNA, mouse; C532623:Mirn155 microRNA, mouse; D016328:NF-kappa B; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse