Loss of VLA‐2 Collagen Receptor in Breast Carcinoma, Facilitating Invasion and Metastasis

The integrin VLA‐2 as a collagen receptor and VLA‐5 as a fibronectin receptor were detected immunohistochemically in normal, benign tumor and carcinoma tissues of the breast. Both proteins were also detected by Western‐blot analysis in some carcinoma cases. Epithelial and myoepitheiial cells of both normal breast and benign tumor were in all cases immunoreactive for VLA‐2 in the plasma membrane. Carcinoma cells in the invasive component were not immunoreactive for VLA‐2 in 31 (46%) of 67 cases. Carcinoma cells in the intraductal components were negative for VLA‐2 in only 4 (11%) of 36 cases, while 20 cases (56%) showed weak expression and 12 cases (33%) showed strong expression. Metastatic carcinoma cells in the lymph nodes of 6 cases showed no immunoreactivity except in one case, whereas, again with the exception of one case, the carcinoma cells in the primary tumors did show VLA‐2 expression. With regard to VLA‐5, there was no difference in its expression in the invasive components and the intraductal components. These findings suggest that the loss of VLA‐2 plays a role in the invasion and metastasis of breast carcinoma.