An immunosorbent assay for blood group I antigens in breast carcinoma

Tumor cells elaborate and release into the circulation a variety of glycoproteins. An enzyme-linked immunosorbent assay (ELISA) was developed to monitor carbohydrate structures secreted into the circulation. Among these antigens are the structures specific for the blood group I antigens, which are incompletely converted to ABH antigens on the membranes of tumor cells. The I antigens in the sera of 67 women with breast carcinoma (BCa), 58 with benign breast disease (BBD), and 47 controls were measured by the ELISA. In this assay, I antigen from ovarian cyst mucin was bound to the wells of polystyrene microtiter plates. The monoclonal human anti-I antibody (Hy) was added to the wells along with perchloric acid extracts of patient and control sera at five different dilutions. The anti-I binding to the solid-phase I antigen was determined after incubation steps with peroxidase-labeled anti-human IgM and substrate. The amount of sera extracts giving 50% inhibition of anti-I (Hy) binding was determined from the inhibition curves which were corrected by integrating the slope values into that of the standard curve obtained with extracts of normal sera. The I antigens were significantly higher in pathologic stage (PS) IV sera (P < 0.001), and comparable in PS I, PS II, and PS III and BBD sera to those in control sera. The anti-I (Hy) binds strongly Gal 1,4 GlcNAc 1,6 Gal (αGalNAc); Gal 1,4 GlcNAc, 1,6 (Gal 1,4 GlcNAc 1,3) Gal; and to a lesser extent Gal 1,4 GlcNAc 1,3 Gal 1,4 GlcNAc (0.06, 0.09, and 0.35 mM, giving 50% inhibition, respectively). It was concluded that similar or related structures may be expressed on the membrane of metastatic BCa cells.