Knockout of alpha6 beta1-integrin expression reverses the transformed phenotype of hepatocarcinoma cells.
OBJECTIVE
Hepatocellular carcinoma is a common complication in liver cirrhosis. The integrin alpha6 beta1, a receptor for the laminin family of extracellular matrix proteins, has been found to be overexpressed in hepatocarcinoma. In an effort to further characterize the involvement of alpha6 beta1-integrin in hepatocarcinoma progression and to study alpha6 beta1-mediated functions, a human hepatocarcinoma cell line, HepG2, that express high surface levels of alpha6 beta1 and uses only this integrin to mediate adhesion on laminin was identified.


METHODS
To assess the role of alpha6 beta1 in these cells, a cytoplasmic domain deletion mutant of the beta4-integrin subunit by complementary DNA transfection was expressed. The expression of the mutant beta4 subunit in association with endogenous alpha6 showed a dominant-negative effect on alpha6 beta1 expression.


RESULTS
Stable transfectants of HepG2 that expressed the mutant beta4 subunit showed a reduced ability to adhere and migrate on laminin matrices and to invade Matrigel. Furthermore, transfected cells showed significantly lower growth rates and reduced anchorage-independent growth compared with mock-transfected cells.


CONCLUSIONS
These findings on the expression and function of alpha6 beta1 in hepatocarcinoma cells emphasize the potential contribution of this laminin receptor in the neoplastic transformation of hepatocytes.
Istituto di Medicina Interna, Universita' di Firenze, Firenze, Italy.
V
V
Carloni
R G
RG
Romanelli
A M
AM
Mercurio
M
M
Pinzani
G
G
Laffi
G
G
Cotrozzi
P
P
Gentilini
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D017353:Gene Deletion; D006801:Humans; D039121:Integrin alpha6beta1; D039663:Integrin beta4; D016023:Integrins / Q000235:genetics*; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D009361:Neoplasm Invasiveness / Q000503:physiopathology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D017474:Receptors, Laminin / Q000378:metabolism; D014162:Transfection / Q000502:physiology; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D039121:Integrin alpha6beta1; D039663:Integrin beta4; D016023:Integrins; D010446:Peptide Fragments; D017474:Receptors, Laminin