title: Role of protein kinase C and epidermal growth factor receptor signalling in growth stimulation by neurotensin in colon carcinoma cells.
abstract: BACKGROUND
  Neurotensin has been found to promote colon carcinogenesis in rats and mice, and proliferation of human colon carcinoma cell lines, but the mechanisms involved are not clear. We have examined signalling pathways activated by neurotensin in colorectal and pancreatic carcinoma cells.
  
  
  METHODS
  Colon carcinoma cell lines HCT116 and HT29 and pancreatic adenocarcinoma cell line Panc-1 were cultured and stimulated with neurotensin or epidermal growth factor (EGF). DNA synthesis was determined by incorporation of radiolabelled thymidine into DNA. Levels and phosphorylation of proteins in signalling pathways were assessed by Western blotting.
  
  
  RESULTS
  Neurotensin stimulated the phosphorylation of both extracellular signal-regulated kinase (ERK) and Akt in all three cell lines, but apparently did so through different pathways. In Panc-1 cells, neurotensin-induced phosphorylation of ERK, but not Akt, was dependent on protein kinase C (PKC), whereas an inhibitor of the β-isoform of phosphoinositide 3-kinase (PI3K), TGX221, abolished neurotensin-induced Akt phosphorylation in these cells, and there was no evidence of EGF receptor (EGFR) transactivation. In HT29 cells, in contrast, the EGFR tyrosine kinase inhibitor gefitinib blocked neurotensin-stimulated phosphorylation of both ERK and Akt, indicating transactivation of EGFR, independently of PKC. In HCT116 cells, neurotensin induced both a PKC-dependent phosphorylation of ERK and a metalloproteinase-mediated transactivation of EGFR that was associated with a gefitinib-sensitive phosphorylation of the downstream adaptor protein Shc. The activation of Akt was also inhibited by gefitinib, but only partly, suggesting a mechanism in addition to EGFR transactivation. Inhibition of PKC blocked neurotensin-induced DNA synthesis in HCT116 cells.
  
  
  CONCLUSIONS
  While acting predominantly through PKC in Panc-1 cells and via EGFR transactivation in HT29 cells, neurotensin used both these pathways in HCT116 cells. In these cells, neurotensin-induced activation of ERK and stimulation of DNA synthesis was PKC-dependent, whereas activation of the PI3K/Akt pathway was mediated by stimulation of metalloproteinases and subsequent transactivation of the EGFR. Thus, the data show that the signalling mechanisms mediating the effects of neurotensin involve multiple pathways and are cell-dependent.
authors.affiliation: Department of Pharmacology, Institute of Clinical Medicine, Faculty of Medicine and Oslo University Hospital, University of Oslo, Oslo, Norway. k.mueller@hotmail.no
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Müller
authors.forename: Ingun H
authors.initials: IH
authors.lastname: Tveteraas
authors.forename: Monica
authors.initials: M
authors.lastname: Aasrum
authors.forename: John
authors.initials: J
authors.lastname: Ødegård
authors.forename: Mona
authors.initials: M
authors.lastname: Dawood
authors.forename: Olav
authors.initials: O
authors.lastname: Dajani
authors.forename: Thoralf
authors.initials: T
authors.lastname: Christoffersen
authors.forename: Dagny L
authors.initials: DL
authors.lastname: Sandnes
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D009496:Neurotensin / Q000494:pharmacology*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D009496:Neurotensin; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051058:Oncogene Protein v-akt; D011493:Protein Kinase C; D002118:Calcium