LOCALIZATION OF BINDING-SITES OF ULEX-EUROPAEUS-I, HELIX-POMATIA AND GRIFFONIA-SIMPLICIFOLIA I-B-4 LECTINS AND ANALYSIS OF THEIR BACKBONE STRUCTURES BY SEVERAL GLYCOSIDASES AND POLY-N-ACETYLLACTOSAMINE-SPECIFIC LECTINS IN HUMAN BREAST CARCINOMAS

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 lect ins such as Helix pomatia agglutinin (HPA) and Griffonia simplicifolia agglutinin I-B-4 (IGSAI-B?4) 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 r elationship between such phenotypically distinct events. For this purp ose, we examined whether the binding sites of these lectins and Ulex e uropaeus 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 t he blood group (ABO) of the patients and was not affected by the histo logical type of the carcinomas. Observation of serial sections stained with these lectins revealed that the distribution of HPA binding site s was almost identical to that of GSAI-B-4 in most cases. Furthermore, in some cases, UEA-I binding patterns were similar to those of HPA an d GSAI-B-4 but in other cases, mosaic staining patterns with these lec tins were also observed, i.e., some cell clusters were stained with bo th HPA and GSAI-B-4 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 cell s following endo-beta-galactosidase digestion. Among the lectins speci fic to poly-N-acetyllactosamine, Lycopersicon esculentum agglutinin (L EA) most vividly and consistently stained the cancer cells. Next to LE A, pokeweed mitogen agglutinin was also effective in staining these ce lls. Carcinoma cells reactive with these lectins corresponded well to those stained with both HPA and GSAI-B-4, and in some cases, with UEA- I. These results demonstrate that the binding sites of UEA-I, HPA, and GSAI-B-4 are expressed concomitantly in the same carcinoma cells and all carry linear and branched poly-N-acetyllactosamine on N-glycans, s uggesting that the synthesis of this complex carbohydrate is one of th e most important and basic processes leading to the malignant transfor mation of cells, invasion, and metastasis of carcinoma cells.