Characterization of a novel neuroglandular antigen (NGA) expressed on abnormal human melanocytes.

Murine monoclonal antibodies (MAbs) were produced with reactivity to human malignant melanoma. Six MAbs, 3 of the IgGI (LS113, LS140, LS152) and 3 of the IgG2a (LS59, LS62, LS76) subclasses, were selected for their binding, with an identical pattern of reactivity, to a novel melanoma-associated antigen. As characterized by the enzyme-linked immunosorbent assay (ELISA), these MAbs were found to be positive on n-octyl-beta-D-glucopyranoside extracts of all 10 melanoma cell lines tested and on extracts of 22 metastatic melanoma tumors. The antibodies had minimal reaction with a panel of 14 normal adult tissue extracts. A degree of cross-reactivity was observed with 50% of 39 non-melanoma tumor extracts. The results obtained with the ELISA on cell line and tissue extracts were duplicated using the ABC method of peroxidase staining. The pattern of cross-reactivity, as demonstrated by the intense staining of paraffin-embedded and frozen tissue sections of normal, benign and malignant tissues, defines the recognized protein as a neuroglandular antigen (NGA). Immunoadsorbents made with the antibodies were used to purify the antigen shed from cultured melanomas. All 6 MAbs recognized this purified antigen while 5 other antimelanoma antibodies did not react with it. On gel electrophoresis this antigen is a highly glycosylated glycoprotein with a protein core of 21 kDa.