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 less than 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 (alpha GalNAc); 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.