Expression of beta 1 integrins in non-neoplastic mammary epithelium, fibroadenoma and carcinoma of the breast.

beta 1 Integrins were examined immunohistochemically in normal and mastopathic mammary glands, 12 benign tumours and 90 carcinomas of the breast using monoclonal antibodies against beta 1 and alpha 1 to alpha 6 subunits. When compared with epithelial cells of non-neoplastic mammary glands and of benign tumours, carcinoma cells showed considerable quantitative changes in the pattern of alpha 2, alpha 3 and alpha 6 subunit expression. In contrast, the distribution pattern of beta 1, alpha 1, alpha 4 and alpha 5 antigens corresponded to the situation observed in non-neoplastic mammary gland epithelium in most instances. An abnormal expression of alpha 2 was found in 71.0% of the carcinomas ranging from a remarkably low number of alpha 2-positive tumour cells in 27.5% of the cases to a complete absence of the alpha 2 molecule in 43.5% of the carcinomas. Of the carcinomas 39.9% exhibited quantitative changes in alpha 3 expression with an abnormally low content of alpha 3-positive neoplastic cells in 15.4% and a complete absence of this molecule in 24.5% of the cases. Expression of alpha 6 was abnormal in 73.2% of the carcinomas, consisting in a greater number of alpha 6-negative tumour cells in 31.9% and in a complete absence of alpha 6 in 41.3% of the tumours. The abnormally low expression/absence of alpha 2 and alpha 3 subunits correlated with oestrogen receptor negativity (P < 0.033 and P < 0.04, respectively). In addition, abnormally low expression/absence of alpha 2 correlated with poor differentiation of the tumours (P < 0.014). The quantitative changes in the expression pattern of beta 1-associated alpha subunits in breast carcinomas may cause a disturbed cell-cell and/or cell-matrix interaction that increases the invasive and migratory property of the tumour cells.