Knockout of alpha6 beta1-integrin expression reverses the transformed phenotype of hepatocarcinoma cells

Background & aims: 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.