HUMAN COLON-CARCINOMA CELLS USE MULTIPLE RECEPTORS TO ADHERE TO LAMININ - INVOLVEMENT OF ALPHA-6-BETA-4 AND ALPHA-2-BETA-1 INTEGRINS

In this study, we used clone A, a human colon carcinoma cell line, to characterize those integrins that mediate colon carcinoma adhesion to laminin. Monoclonal antibodies specific for the human β1 subunit inhibited clone A adhesion to laminin. They also precipitated a complex of surface proteins that exhibited an electrophoretic behavior characteristic of α2β1 and α3β1. A monoclonal antibody specific for α2 (PIH5) blocked clone A adhesion to laminin, as well as to collagen I. An α3-specific antibody (P1B5) had no effect on clone A adhesion to laminin, even though it can block the adhesion of other cell types to laminin. Thus, the α2β1 integrin can function as both a laminin and collagen I receptor on clone A cells. Although these cells express α3β1, an established laminin receptor, they do not appear to use it to mediate laminin adhesion. In addition, the monoclonal antibody GoH3, which recognizes the α6 integrin subunit, also inhibited carcinoma adhesion to laminin but not to fibronectin or collagen I. This antibody precipitated the α6 subunit in association with the β4 subunit. There was no evidence of α6β1 association on these cells. In summary, the results obtained in this study indicate that multiple integrin α subunits, in association with two distinct β subunits, are involved in colon carcinoma adhesion to laminin. Based on the behavior of α3β1 and α2β1, the results also suggest that cells can regulate the ability of a specific integrin to mediate adhesion. © 1990 by The American Society for Cell Biology.