COMPARISON OF INTEGRIN ALPHA-CHAIN EXPRESSION IN BENIGN AND MALIGNANTSALIVARY-GLAND TUMORS

Objective. This study investigates the distribution of the or chain of the integrin family of extracellular matrix receptors in a series of adenomas and carcinomas of salivary gland origin to determine if the m alignant phenotype is associated with modification of the expression o f these receptors. Study design. Cryostat sections of 36 tumor specime ns were stained by a standard streptavidin-biotin-peroxidase technique using primary monoclonal antibodies against alpha 1-6 and alpha v int egrin chains. The immunohistochemical reaction was scored using a thre e-point scale and the results were analyzed using Fisher's exact test. Results. In salivary adenomas, alpha 2, alpha 3, alpha 4, alpha 6, an d alpha v chains were widely expressed in most of the cases studied. T he alpha 1 subunit was prominently expressed by the epithelial cells o f Warthin's tumor, whereas a minority of pleomorphic adenomas showed i mmunoreactivity for this antigen. We observed alpha 5 subunit expressi on only in the mesenchymal-like component of pleomorphic adenomas. In salivary carcinomas, integrin a chain expression was heterogeneous, va rying greatly between different histotypes and within the same histoty pe. The distribution of the antigens was similar to that of adenomas, except for the alpha 6 chain, which localized not only at the interfac e between cell and matrix, but also at sites of cell-cell contact. Whe n the immunohistochemical levels of integrin alpha chain expression we re compared in adenomas and carcinomas, expression significantly decre ased for the alpha 6 and alpha v chains (p = 0.0007; p = 0.002, respec tively). Conclusions. Loss of alpha 6 and alpha v integrin subunits oc curring in salivary gland carcinomas could modify the adhesive propert ies of malignant cells, contributing to the invasive potential of thes e tumors.