EXPRESSION OF BETA-1 INTEGRINS IN NONNEOPLASTIC MAMMARY EPITHELIUM, FIBROADENOMA AND CARCINOMA OF THE BREAST

Beta1 Integrins were examined immunohistochemically in normal and mast opathic mammary glands, 12 benign tumours and 90 carcinomas of the bre ast using monoclonal antibodies against beta1 and alpha1 to alpha6 sub units. When compared with epithelial cells of non-neoplastic mammary g lands and of benign tumours, carcinoma cells showed considerable quant itative changes in the pattern of alpha2, alpha3 and alpha6 subunit ex pression. In contrast, the distribution pattern of beta1, alpha1, alph a4 and alpha5 antigens corresponded to the situation observed in non-n eoplastic mammary gland epithelium in most instances. An abnormal expr ession of alpha2 was found in 71.0% of the carcinomas ranging from a r emarkably low number of alpha2-positive tumour cells in 27.5% of the c ases to a complete absence of the alpha2 molecule in 43.5% of the carc inomas. Of the carcinomas 39.9% exhibited quantitative changes in alph a3 expression with an abnormally low content of alpha3-positive neopla stic cells in 15.4% and a complete absence of this molecule in 24.5% o f the cases. Expression of alpha6 was abnormal in 73.2% of the carcino mas, consisting in a greater number of alpha6-negative tumour cells in 31.9% and in a complete absence of alpha6 in 41.3% of the tumours. Th e abnormally low expression/absence of alpha2 and alpha3 subunits corr elated with oestrogen receptor negativity (P < 0.033 and P < 0.04, res pectively). In addition, abnormally low expression/absence of alpha2 c orrelated with poor differentiation of the tumours (P < 0.014). The qu antitative changes in the expression pattern of beta1-associated alpha subunits in breast carcinomas may cause a disturbed cell-cell and/or cell-matrix interaction that increases the invasive and migratory prop erty of the tumour cells.