Characterization of a glycosphingolipid antigen defined by the monoclonal antibody MBr1 expressed in normal and neoplastic epithelial cells of human mammary gland

The antigen defined by a monoclonal antibody, MBr1, was found to be expressed in normal human mammary gland epithelia and human mammary carcinoma cells (Menard, S., Tagliabue, E., Canevari, S., Fossati G., and Colnaghi, M.I. (1983) Cancer Res. 43, 1295-1300). The antigen has been isolated from breast cancer cell line MCF-7, which was used as immunogen, and its structure was determined by methylation analysis, NMR spectroscopy, direct probe mass spectrometry, and enzymatic degradation as identified below. Fucα1→2Galβ1-→3GalNAcβ1→3Galα1→4Galβ1→4Glcβ1→1Cer. The antibody cross-reacted weakly with fucosylasialo-G(M1) (IV³FucGg₄), which shares the same terminal sequence, Fucα1→2Galβ1→3GalNAc, with this antigen. However, various other structures, including lactoseries H structure (Fucα1→2Galβ1→4/or3GlcNAcβ1→3Gal), did not show any reactivity with this antibody. Therefore, this antigen represents a blood group H antigen with a globo-series structure which is abundant in human teratocarcinoma (Kannagi, R., Levery, S.B., Ishigami, F., Hakomori, S., Shevinsky, L.H., Knowles, B.B., and Solter, D. (1983) J. Biol. Chem. 258, 8934-8942), although its presence must be limited in normal adult human tissue.