Western blot analysis of glycoproteins bearing Lewis(a) and sialyl-Lewis(a) antigens in human colorectal mucosa.

Glycoproteins (GPs) bearing Lewis(a) and sialyl-Lewis(a) antigens (Le(a), sialyl-Le(a)) derived from human colorectal carcinomas and their surrounding non-neoplastic mucosa (normal mucosa) were analyzed using Western blotting. GPs bearing Le(a) were detected mainly as segmental bands of M(r) 310, 220, 160, and 80 kDa in 80% of the normal mucosa, but these GPs were detected predominantly as broad bands ranging from high to low molecular weight (MW) in 71% of the carcinoma tissues. GPs bearing sialyl-Le(a) were detected only in 23% of the normal mucosa and limited on huge MW bands, i.e., more than 400 kDa, whereas these GPs were detected predominantly as broad bands in 49% of the carcinoma tissues. In the cases with lymph node metastasis, the MW of GPs bearing sialyl-Le(a) varied over a wide range and were detected as broad bands, compared with the cases without metastasis. In conclusion, the MW of GPs bearing Le(a) and sialyl-Le(a) in normal colorectal mucosa was different from that in colorectal carcinomas. That is, the MWs of GPs bearing Le(a) varied more in carcinoma tissues, and the GPs bearing sialyl-Le(a) from carcinoma tissues had lower MWs than those from normal mucosa. It was, furthermore, suggested that the increased expression of lower MW GPs bearing sialyl-Le(a) are associated with an increased metastatic potential of the tumor cells.