title: Characterization of the ETSA-21 antigen, a glycosylphosphatidyl-inositol anchor glycoprotein identified in breast cancer cells using monoclonal antibody B21.
abstract: Mab B21 is a monoclonal antibody (Mab) that recognizes an epithelial tumor surface antigen (ETSA-B21) from diverse human tumor cell lines including breast, ovary, uterus, and their cognate carcinoma tissues. A lower reactivity has been observed in normal breast tissue and benign hyperplesia. In this study, the characteristics of the ETSA-B21 antigen have been examined in greater detail in the MCF-7, SK-BR-3, and MDA-MB-453 breast cancer cell lines. Treatment with phosphatidylinositol-phospholipase C, but no neuraminidase were found to partially remove the ETSA-B21 signal from the cell surface as revealed by immunofluorescence microscopy. Inhibition of the N-glycosylation pathway by tunicamycin resulted in a decreased ETSA-B21 signal on the cell membrane. In addition, the antigen-antibody complex was internalized in breast cancer cells as demonstrated by an acidic was internalization assay evaluated using immunofluorescence. In conclusion, this study suggests that ETSA-B21 is a GPI anchor N-glycosylated protein promoting specific antibody internalization in breast cancer cells.
authors.affiliation: Institute of Biology and Experimental Medicine, National Research Council of Argentina, Buenos Aires.
authors.forename: N V
authors.initials: NV
authors.lastname: Annibali
authors.forename: A
authors.initials: A
authors.lastname: Baldi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000276:immunology*; D001943:Breast Neoplasms / Q000276:immunology*; D004705:Endocytosis; D005260:Female; D006031:Glycosylation / Q000187:drug effects; D017261:Glycosylphosphatidylinositols / Q000276:immunology*; D006801:Humans; D051379:Mice; D009439:Neuraminidase / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D017261:Glycosylphosphatidylinositols; D010738:Type C Phospholipases; D009439:Neuraminidase; D043265:Phosphatidylinositol Diacylglycerol-Lyase