Distribution of CD44 variant isoforms in human skin: differential expression in components of benign and malignant epithelia.

Expression of cell adhesion molecules regulates epithelial cell differentiation and organization of complex tissues such as skin. The CD44 family of adhesion molecules is generated by alternative splicing of up to 10 variant exons encoding inserts into the extracellular domain. Expression of CD44 variant exons has been correlated with metastatic potential of some epithelial malignancies. We studied the distribution of total and variant CD44 isoforms containing exons v4, v6, and v9 in normal skin, basal cell carcinoma, and in control tissues using immunohistologic assays. While normal epidermis and other stratified squamous epithelia reacted strongly with antibodies specific for standard CD44 (CD44S) and CD44 isoforms containing exons v4, v6, and v9, the epithelium of eccrine glands was reactive, often in a polarized distribution, only with antibodies specific for CD44S and isoforms containing exon v9. These studies suggest that differential expression of CD44 variant exons may be important in development and organization of epithelial structures within skin. Malignant cells in basal carcinoma tissues were found to have low reactivity with antibodies specific for CD44S or variant CD44 molecules. The low expression of CD44 molecules in basal cell carcinomas may play a role in the relatively low probability of metastasis of these neoplasms.