Expression of tenascin during carcinogenesis and involution of hormone-dependent tissues.

Cytotactin/tenascin/hexabrachion, now referred to as tenascin-C (TN-C), is a hexameric glycoprotein of the extracellular matrix of mesenchymal tissue constituents. A high expression was found in embryonic development and during carcinogenesis of almost all organs. TN-C expression by the mesenchyme thereby appears to be induced by paracrine-acting, epithelial-derived (growth) factors. In normal adult organs there is little, if any, TN-C expression. In the human endometrium for instance, tenascin expression is low in the normal proliferative endometrium and undetectable in the normal secretory endometrium. In this paper, the appearance and expression of TN-C in hormone-dependent tissues, regressing hormone-dependent tissues, and tumors of the endometrium, breast and prostate is reviewed. Further, the regulation of TN-C expression is summarized and possible functions of TN-C during regression and carcinogenesis of hormone-dependent tissues are discussed.