Several studies have shown the deletion of
blood group A or B
antigens and the accumulation of H
antigens in human
breast carcinomas. Other studies have independently demonstrated that the binding sites of
lectins such as
Helix pomatia agglutinin (HPA) and Griffonia simplicifolia
agglutinin I-B4 (GSAI-B4) are highly expressed in these cells. In order to clarify the molecular mechanisms of malignant transformation and
metastasis of
carcinoma cells, it is important to understand the relationship between such phenotypically distinct events. For this purpose, we examined whether the binding sites of these
lectins and Ulex europaeus
agglutinin I (UEA-I) are expressed concomitantly in the same
carcinoma cells and analyzed their backbone structures. The expression of the binding sites of these
lectins was observed independently of the
blood group (ABO) of the patients and was not affected by the histological type of the
carcinomas. Observation of serial sections stained with these
lectins revealed that the distribution of HPA binding sites was almost identical to that of GSAI-B4 in most cases. Furthermore, in some cases, UEA-I binding patterns were similar to those of HPA and GSAI-B4 but in other cases, mosaic staining patterns with these
lectins were also observed, i.e., some cell clusters were stained with both HPA and GSAI-B4 but not with UEA-I and adjacent cell clusters were stained only with UEA-I. Digestion with
endo-beta-galactosidase or
N-glycosidase F markedly reduced the staining intensity of these
lectins. Together with the reduction of staining by these
lectins, reactivity with
Griffonia simplicifolia agglutinin II appeared in
carcinoma cells following
endo-beta-galactosidase digestion. Among the
lectins specific to
poly-N-acetyllactosamine, Lycopersicon esculentum
agglutinin (LEA) most vividly and consistently stained the
cancer cells. Next to LEA,
pokeweed mitogen agglutinin was also effective in staining these cells.
Carcinoma cells reactive with these
lectins corresponded well to those stained with both HPA and GSAI-B4, and in some cases, with UEA-I. These results demonstrate that the binding sites of UEA-I, HPA, and GSAI-B4 are expressed concomitantly in the same
carcinoma cells and all carry linear and branched
poly-N-acetyllactosamine on N-
glycans, suggesting that the synthesis of this complex
carbohydrate is one of the most important and basic processes leading to the malignant transformation of cells, invasion, and
metastasis of
carcinoma cells.