ALTERED INTEGRIN EXPRESSION IN ADENOCARCINOMA OF THE BREAST - ANALYSIS BY INSITU HYBRIDIZATION

The integrin superfamily of adhesion receptors mediates interactions b etween cells and the extracellular matrix. Our earlier immunohistochem ical analysis showed that normal mammary epithelium expressed high lev els of the alpha2beta1 collagen/laminin receptor and intermediate leve ls of the alpha5beta1 fibronectin receptor. In contrast, malignant cel ls of adenocarcinoma of the breast exhibited marked diminution or loss of the alpha2beta1 and alpha5beta1 integrins. We have now evaluated t he level of alpha2, alpha5, and beta1 integrin subunit messenger (m)RN A by in situ hybridization in adenocarcinoma of the breast. Normal bre ast ducts and ductules expressed high levels of all three integrin sub unit mRNAs. Poorly differentiated lesions expressed low to undetectabl e levels of alpha2, alpha5, and beta1 mRNA. Well- and moderately diffe rentiated lesions expressed all three subunits at intermediate levels. Thus, decreased expression of the alpha2beta1 and alpha5beta1 integri ns in mammary carcinoma is the result of decreased steady-state integr in subunit mRNA levels due to altered expression of the integrin genes .