Syndecan in carcinomas produced from transformed epithelial cells in nude mice.

Expression of syndecan, a cell surface proteoglycan, was studied in carcinomas induced by implanting chemically transformed keratinocytes and mammary epithelial cells into nude mice. By immunohistochemistry and in situ hybridization, syndecan was localized in keratinizing cells within moderate- to well-differentiated squamous cell carcinomas in a pattern resembling that of normal epidermis, whereas almost total loss of expression was detected in poorly-differentiated areas within these tumors. In anaplastic spindle cell carcinomas, syndecan expression was barely detectable. In biphasic tumors, induced by mammary epithelial cells, and consisting of cysts overlaying an adenocarcinoma, syndecan was unquely localized to differentiated epithelial structures such as secretory epithelial lining of the cysts as well as aberrant glands and ducts within the carcinoma. Based on the expression pattern of syndecan in the tumors studied, we conclude that the expression of this developmentally regulated molecule is associated with epithelial differentiation also during neoplastic growth.