Altered integrin expression in adenocarcinoma of the breast: Analysis by in situ hybridization

The integrin superfamily of adhesion receptors mediates interactions between cells and the extracellular matrix. Our earlier immunohistochemical analysis showed that normal mammary epithelium expressed high levels of the α₂β₁ collagen/laminin receptor and intermediate levels of the α₅β₁ fibronectin receptor. In contrast, malignant cells of adenocarcinoma of the breast exhibited marked diminution or loss of the α₂β₁ and α₅β₁ integrins. We have now evaluated the level of α₂, α₅, and β₁ integrin subunit messenger (m)RNA by in situ hybridization in adenocarcinoma of the breast. Normal breast ducts and ductules expressed high levels of all three integrin subunit mRNAs. Poorly differentiated lesions expressed low to undetectable levels of α₂, α₅, and β₁ mRNA. Well- and moderately differentiated lesions expressed all three subunits at intermediate levels. Thus, decreased expression of the α₂β₁, and α₅β₁ integrins in mammary carcinoma is the result of decreased steady-state integrin subunit mRNA levels due to altered expression of the integrin genes.