title: Neurotensin signaling activates microRNAs-21 and -155 and Akt, promotes tumor growth in mice, and is increased in human colon tumors.
abstract: OBJECTIVE
  Neurotensin promotes inflammation and colon cancer via the neurotensin-1 receptor (NTR1). MicroRNAs (miR) regulate protein synthesis by degrading or preventing translation of mRNAs. We analyzed expression of 365 different microRNAs by human colonic epithelial cells (NCM460) after activation of NTR1.
  
  
  METHODS
  We performed microarray analysis of mRNA expression by neurotensin-stimulated NCM460 cells that overexpressed NTR1. Nuclear factor-κB (NF-κB) binding sites were identified and tumorigenesis was assessed using soft agar assays and xenograft analysis of severe combined immunodeficiency mice. Targets of neurotensin-regulated microRNAs were identified via bioinformatic, real-time polymerase chain reaction, and immunoblot analyses. We analyzed RNA samples from human normal colon and tumor samples.
  
  
  RESULTS
  Neurotensin stimulated differential expression of 38 microRNAs, including miR-21 and miR-155, which have been associated with tumor growth and contain NF-κB binding sites. Neurotensin expression increased colony formation by HCT-116 cells. Blocking miR-21 and/or miR-155 prevented colony formation (P < .001). In mice, intraperitoneal administration of neurotensin increased the growth rate of HCT-116 xenograft tumors; blocking miR-21 and/or miR-155 slowed this tumor growth. Neurotensin activated Akt in HCT-116 cells; this effect was inhibited by blocking miR-21 and/or miR-155 (P < .001). Neurotensin activated AKT through miR-155-mediated suppression of the phosphatase protein phosphatase 2A catalytic subunit alpha (PPP2CA). Levels of phosphatase and tensin homolog (PTEN) and suppressor of cytokine signaling 1 (SOCS1) mRNA, potential targets of miR-21 and miR-155, respectively, were down-regulated by these miRs. Levels of NTR1, miR-21, and miR-155 increased significantly in human colon tumor samples, compared with normal tissues, whereas PPP2CA, SOCS1, and PTEN mRNAs were reduced significantly.
  
  
  CONCLUSIONS
  NTR1 activation stimulates expression of miR-21 and miR-155 in colonocytes, via Akt and NF-κB, to down-regulate PTEN and SOCS1 and promote growth of tumors in mice. Levels of NTR1, miR-21, and miR-155 increase in human colon tumor samples and correlate with tumor stage.
authors.affiliation: Division of Digestive Diseases, Inflammatory Bowel Disease Center, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
authors.forename: Kyriaki
authors.initials: K
authors.lastname: Bakirtzi
authors.forename: Maria
authors.initials: M
authors.lastname: Hatziapostolou
authors.forename: Iordanes
authors.initials: I
authors.lastname: Karagiannides
authors.forename: Christos
authors.initials: C
authors.lastname: Polytarchou
authors.forename: Savina
authors.initials: S
authors.lastname: Jaeger
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Iliopoulos
authors.forename: Charalabos
authors.initials: C
authors.lastname: Pothoulakis
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology*; D004195:Disease Models, Animal; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D018028:Receptors, Neurotensin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism; D014183:Transplantation, Heterologous
chemical_list: C524942:MIRN155 microRNA, human; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D018028:Receptors, Neurotensin; C108944:SOCS1 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C114036:neurotensin type 1 receptor; D009496:Neurotensin; D051057:Proto-Oncogene Proteins c-akt; C517189:PPP2CA protein, human; D054648:Protein Phosphatase 2; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human