Serological and immunohistochemical studies on sialylated carbohydrate antigens in colorectal carcinoma.

Sialylated carbohydrate antigens, such as CA19-9 (sialyl Lea), CA-50 (sialyl Le4), CSLEX1 (sialyl Lex) and SLX (sialyl Lex-i), were assayed in the same preoperative serum samples of 63 patients with colorectal cancer, and compared with CEA. In addition immunohistochemical expressions of sialyl Lea, sialyl lex and sialyl Lex-i antigens were studied in 62 colorectal carcinomas and 42 normal mucosal sites remote from the malignant lesion using monoclonal antibodies CSLEA1, CSLEX1 and FH-6, respectively, in order to elucidate their tumor-specificity and clinical usefulness as a tumor-associated antigen. Serologically, the percent positive rates of CA19-9, CA-50, CSLEX1, SLX and CEA were 30.2%, 17.7%, 23.8%, 16.1% and 44.4%, respectively. In dukes' A and B, these sialylated carbohydrate antigens, especially CSLEX1 and SLX, showed low positive rates, but the percent positive rates of CSLEX1 and SLX correlated with operative radicality. The positive spectrum of CSLEX1 differed from that of CA19-9 in sera, and CEA had no correlation with these two antigens. The immunohistochemical expression rates of sialyl Lea, sialyl Lex and sialyl Lex-i were 88.1%, 17.0% and 9.5% in normal mucosa, but were 77.8%, 90.5% and 71.4% in carcinoma, respectively. These data suggested that the type 2 chain antigens CSLEX1 and SLX, which have high tumor-specificity compared with CA19-9, may be useful in preoperative diagnosis for extension of carcinoma and operative radicality, although early diagnosis using these sialylated carbohydrate antigens may be difficult, while the combined use of CA19-9, CSLEX1 and CEA should make it possible to detect a wide range of colorectal cancer patients.