Isolation of two novel sialyl-Lewis X-active oligosaccharides by high-performance liquid affinity chromatography using monoclonal antibody Onc-M26.

A monoclonal antibody, Onc-M26, that recognizes a cancer-associated antigen expressed by most human adenocarcinomas of the breast was shown previously to recognize a carbohydrate epitope carried on a hexaglycosyl ganglioside carrying the sialyl-Lewis X (SLex) antigen (P.S. Linsley et al., 1988, Cancer Res. 48, 2138-2148). Evidence that the antibody binds even more avidly to minor gangliosides containing more complex carbohydrate chains prompted us to search for a higher affinity epitope among sialylated oligosaccharides from pooled human milk. Affinity chromatography of a partially purified fraction of monosialylated milk oligosaccharides on a column containing monoclonal antibody Onc-M26 bound to a macroporous silica matrix gave a peak with a retention volume significantly greater than that of a standard SLex-active hexasaccharide. The retained material consisted of two nonasaccharides, each containing the SLex tetrasaccharide sequence, Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3) GlcNAc, linked beta 1-6 to a 3,6-disubstituted galactosyl residue.