Integrin expression on normal and neoplastic human breast epithelium.

Integrin adhesion receptor expression of different benign and malignant breast tumours was examined by means of immunohistochemical techniques. A panel of seven different anti-alpha and two different anti-beta subunit antibodies was used. Normal breast epithelium displayed a well characterized and constant pattern of integrin expression consisting of strong alpha 1,2,3,6 and alpha v, and a relatively weaker beta 1 and beta 3 staining. No staining for alpha 4 or alpha 5 could be detected on the epithelial cells. Benign fibroadenomas did not show changes in their receptor expression compared to normal tissues. In the cases of different types of breast cancer, there was a significant downregulation of all subunits. The staining pattern was distinct if there could a basement membrane like structure be detected around the invading tumour nodules. When laminin and collagen type IV surrounded the tumour cells, those cells in contact with the extracellular matrix components still displayed strong positivity for the integrin subunits. Other cells inside the tumour cell nests or not surrounded by basement membrane did not express integrins. The positively staining cells might be more differentiated owing to the effect the basement membrane. Myoepithelial labeling of the integrin expressing cells gave negative results. The observed integrin expression heterogeneity renders the histologic picture difficult to interpret with regard to clinical behavior of the tumour.