title: Laminin alpha 5 mediates ectopic adhesion of hepatocellular carcinoma through integrins and/or Lutheran/basal cell adhesion molecule.
abstract: Laminins are a diverse group of alpha/beta/gamma heterotrimers formed from five alpha, three beta and three gamma chains; they are major components of all basal laminae (BLs). One laminin chain that has garnered particular interest due to its widespread expression pattern and importance during development is laminin alpha 5. Little is known, however, about the expression and function of laminins containing the alpha 5 chain in human hepatocellular carcinoma (HCC). Here, using a specific antibody, we examined the expression of laminin alpha 5 in normal liver and in HCCs. In normal liver, although laminin alpha 5 was observed in hepatic BLs underlying blood vessels and bile ducts, it was absent from the parenchyma, which may be the origin of HCC. On the other hand, laminin alpha 5 deposition was observed throughout all HCCs tested, regardless of tumor grade. In well-differentiated HCCs, it localized along the trabecules of the tumor. In poorly-differentiated HCCs, it was present in surrounding tumor nodules. In HCC cell lines, laminin alpha 5 heterotrimerized with beta and gamma chains and was secreted into the culture media. To attempt to understand the function of laminins containing alpha 5, the expression of its receptors in HCCs was also determined. In this regard, alpha 3 beta 1/alpha 6 beta 1 integrins and Lutheran/basal cell adhesion molecule (Lu/B-CAM) were expressed in HCC cells. In vitro studies showed that HCC cells readily attached to laminin containing the alpha 5 chain, more so than did primary hepatocytes. In addition to alpha 3 beta 1/alpha 6 beta 1 integrins and Lu/B-CAM, laminin alpha 5 was recognized by integrin alpha 1 beta 1, which also was expressed in HCC cells. These results suggest that laminins containing alpha 5 serve as functional substrates regulating progression of HCC.
authors.affiliation: Laboratory of Clinical Biochemistry, Tokyo University of Pharmacy and Life Sciences, Hachioji 192-0392, Japan.
authors.forename: Yamato
authors.initials: Y
authors.lastname: Kikkawa
authors.forename: Ryo
authors.initials: R
authors.lastname: Sudo
authors.forename: Junko
authors.initials: J
authors.lastname: Kon
authors.forename: Toru
authors.initials: T
authors.lastname: Mizuguchi
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Nomizu
authors.forename: Koichi
authors.initials: K
authors.lastname: Hirata
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mitaka
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D039161:Integrin alpha6beta4 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism*; D007797:Laminin / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D008188:Lutheran Blood-Group System; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C090228:BCAM protein, human; D015815:Cell Adhesion Molecules; D039161:Integrin alpha6beta4; D016023:Integrins; D007797:Laminin; D008188:Lutheran Blood-Group System; D009363:Neoplasm Proteins; C097043:laminin alpha5