Elevated tissue concentrations of sialyl Lex-i in cancerous tissues compared with those in noncancerous tissues of various organs.

Sialyl Lex-i (SLX) concentrations in the extracts of noncancerous and cancerous tissues of various human organs were determined by radioimmunoassay for detailed evaluation of SLX. Cancerous tissues had significantly elevated SLX concentrations compared with noncancerous tissues of various organs. Tissue SLX concentration of the cancerous part was significantly higher than that of the adjacent noncancerous part in the same tissue. There was no significant correlation between tissue SLX concentration and serum SLX level. Positive localization of SLX was clearly observed in such cancerous tissues by immunohistochemical study, although not in any noncancerous tissues. Each of the antigens: SLX, CA 19-9, carcinoembryonic antigen, and CA 125 showed a different distribution pattern in tissue concentration or localization in various organs. These results indicate that SLX may be a valuable cancer-associated antigen produced by malignant tissues, suggesting its clinical application as a tumor marker.