SIALYL-LEWIS(X) AND RELATED CARBOHYDRATE ANTIGENS IN THE PROSTATE

Alteration of cell surface carbohydrate antigens during malignant tran sformation is a well-known phenomenon observed in various tumors. In p rostatic carcinoma, nearly total deletion of normally occurring ABO an d type I-based Lewis antigens, Le(a) and Le(b), has been observed in s everal studies. We studied expression of the closely related type II a ntigens Le(X), Le(y), and sialyl-lewis(X) (SLe(X)) using monoclonal an tibodies. Thirty formalin-fixed specimens obtained from radical prosta tectomy, containing prostatic carcinoma as wed as benign tissue, were evaluated by immunohistochemistry In both cancer and benign tissue, Le (X) expression was minimal or absent. In benign tissue, Le(y) was expr essed in ducts and in the basal layer of glandular epithelium. In tumo r tissue, Le(y) expression was greatly increased and extensive stainin g was observed in 26 of 30 cases. The SLe(X) expression in benign tiss ue was observed only in larger ducts, never in glandular secretory epi thelial cells. In carcinoma, rare cells positive for SLe(X) were prese nt in 8 of 30 cases, and stronger expression with focal to patchy dist ribution was observed in 14 of 30 cases. The results suggest an altera tion in glycosyl transferase activity in prostatic carcinoma, with pre served or increased activity of enzymes responsible for the synthesis of the type II core sequence. This sequence is further glycosylated an d expressed as the difucosylated compound Le(y) or the monofucosyl, mo nosialyl compound SLe(X). For prostate, Le(y) and SLe(X) are the only blood group-related antigens known to be minimal or absent in benign s ecretory epithelial cells that are more highly expressed in malignant tissue. The biological significance of these antigens in terms of tumo r growth and metastasis remains unknown, but their detection by immuno histochemistry may be useful for diagnostic purposes. Clinical studies correlating antigen expression with tumor grade and stage, and patien t outcome are needed. Copyright (C) 1995 by W.B. Saunders Company