The purpose of this work was to investigate whether
sucrase-
isomaltase from enterocyte-like differentiated human colon
carcinoma cell lines carries
blood group antigens of the ABH system. Six cultured lines of
blood group A (HT-29, SW-480, Co-115) or O phenotype (Caco-2, HRT-18, HCT-8R) were studied. Only HT-29 cells grown in the absence of
glucose (HT-29 Glc-) and Caco-2 cells express an enterocytic differentiation with the presence of
sucrase-
isomaltase on the apical surface of the cells. Binding of anti-A
antibodies to HT-29 Glc- and of UEA-I to Caco-2 cells gave the same apical immunofluorescence pattern of staining as did anti-
sucrase-
isomaltase antibodies, whereas only a membrane binding was observed in nondifferentiated cells.
Sucrase-
isomaltase immunoisolated from HT-29 Glc- and Caco-2 cells reacted with anti-A
antibodies and Ulex europaeus
agglutinin-I (UEA-I), respectively, at
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis and immunoblot. Immunoprecipitation of solubilized brush border-enriched fractions from the same cells with UEA-I or anti-A
antibodies resulted in an inhibition of
sucrase activity which reached congruent to 80% for Caco-2 cells with UEA-I and approximately equal to 50% for HT-29 cells with anti-A
antibodies. Similar results were obtained in the corresponding
tumors in nude mice: anti-A
antibodies in HT-29 and UEA-I in Caco-2
tumors bound to the same apical structures as did anti-
sucrase-
isomaltase antibodies;
sucrase-
isomaltase immunoisolated from the
tumors bound anti-A
antibodies (HT-29) or UEA-I (Caco-2). These results support the hypothesis that
sucrase-
isomaltase from enterocyte-like differentiated human
colon cancer cells carries
blood group antigens of the ABH system. These findings suggest that
colon cancers which have been shown to display an apical pattern of expression of ABH
antigens should be screened for their possible enterocytic differentiation.