title: Significance of integrin αvβ5 and erbB3 in enhanced cell migration and liver metastasis of colon carcinomas stimulated by hepatocyte-derived heregulin.
abstract: To study the mechanisms of the highly liver-metastatic character of colon carcinoma cells, we studied the expression pattern of surface integrins on LS-LM6 (a highly liver-metastatic human colon cancer cell line) and the effects of hepatocyte-derived soluble factors on cell migration. LS-LM6 showed significantly higher expression of integrin αvβ5, a ligand for vitronectin (VN), as compared with its parental cell line (LS174T). A conditioned medium of cultured mouse hepatocytes enhanced VN-mediated cell migration of LS-LM6, which was blocked by neutralizing antibody against integrin αvβ5, while the medium did not affect cell adhesion to VN-coated plastic surfaces. The conditioned medium induced phosphorylation of erbB3 and its heterodimeric partner, erbB2. Heregulin (HRG), a ligand for erbB3, exerted similar effects on VN-mediated cell migration and phosphorylation of erbB3 and erbB2. The conditioned medium contained HRG, and depletion of HRG from the medium by pre-absorption with HRG antibody abolished its effects on cell migration. Heregulin (HRG) was expressed in some hepatocytes in the liver with carcinoma cell metastasis. Furthermore, knockdown of integrin αv and erbB3 by small-interfering RNAs significantly inhibited cell migration induced by HRG as well as liver metastasis in vivo. Finally, we found that HRG-induced cell migration was associated with marked phosphorylation of Akt and that cell migration was suppressed by treatment with specific inhibitors of phosphatidylinositol 3-kinase. Our study suggests that hepatocyte-derived HRG might participate in a highly liver-metastatic phenotype of LS-LM6 through enhancement of integrin αvβ5-mediated cell migration and erbB3/erbB2 signaling.
authors.affiliation: Department of Molecular Pathology and Tumor Pathology, Akita University Graduate School of Medicine, Akita, Japan. yoshiokt@med.akita-u.ac.jp
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishikawa
authors.forename: Reiko
authors.initials: R
authors.lastname: Ito
authors.forename: Makiko
authors.initials: M
authors.lastname: Kawamata
authors.forename: Yuko
authors.initials: Y
authors.lastname: Doi
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshida
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Omori
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kotanagi
authors.forename: Takashi
authors.initials: T
authors.lastname: Masuko
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Enomoto
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017077:Culture Media, Conditioned / Q000378:metabolism / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D039081:Integrin alpha5beta1 / Q000235:genetics / Q000378:metabolism*; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000556:secondary; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020890:Neuregulin-1 / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D020893:Receptor, ErbB-3 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014183:Transplantation, Heterologous
chemical_list: D017077:Culture Media, Conditioned; D039081:Integrin alpha5beta1; D020890:Neuregulin-1; D018719:Erb-b2 Receptor Tyrosine Kinases; D020893:Receptor, ErbB-3