A ROLE OF VLA-6 LAMININ RECEPTOR IN INVASION OF BREAST-CARCINOMA

The integrin VLA-6 as a laminin receptor and laminin as a ligand for l aminin receptor were detected immunohistochemically in normal, benign tumor and carcinoma tissues of the breast. Epithelial cells of both no rmal breast and benign tumor were in almost all cases strongly immunor eactive for VLA-6 in the plasma membrane. Carcinoma cells in 34 of 70 cases (49%) with an invasive component were not immunoreactive for VLA -6, and no carcinoma cells showed strong positivity. Although carcinom a cells in only four of 51 cases (8%) with intraductal components were negative for VLA-6, 37 cases (72%) showed weak expression of VLA-6 an d 10 cases (20%) showed strong expression of VLA-6. A concordant expre ssion of VLA-6 on carcinoma cells and laminin around carcinoma cell ne sts with an invasive component was observed, and VLA-6 expression in c arcinoma cells was correlated to tubular formation in carcinoma cell n ests as an indicator of differentiation. These findings suggest that l oss of VLA-6 plays a role in the invasion of breast carcinoma, and tha t VLA-6 laminin receptor and laminin may contribute to tubular differe ntiation of breast carcinoma cells.