ME491 melanoma-associated glycoprotein family: antigenic identity of ME491, NKI/C-3, neuroglandular antigen (NGA), and CD63 proteins.
BACKGROUND
Numerous monoclonal antibodies (MAbs) have been produced to antigens found in human melanomas. Three of the best characterized melanoma antigens include the melanoma-associated glycoproteins (MAGs) defined by two reagent families--the ME491 family (including ME491, 8-1H, and 8-2A) and the NKI/C-3 family (including NKI/C-3 and NKI/black-13)--as well as the neuroglandular antigen (NGA) defined by MAbs LS59, LS62, and LS140. These three antigens have significant similarities in tissue distribution, biosynthesis, and structure. The ME491 MAG has been cloned, mapped, and sequenced. Numerous non-melanoma-associated proteins (Sm23, CO-029, R2, TAPA-1, CD9, CD37, CD53, and CD63) have recently been shown to have significant homology to this sequence.


OBJECTIVE
We conducted this study to investigate the similarity between the two MAG antigens and NGA.


METHODS
Several reagents defining the three different melanoma antigens were compared, using competition immunoprecipitation, immunoassay, and inhibition radioimmunoassay techniques.


RESULTS
Immunoassay experiments show that MAbs defining the three melanoma antigens bind to affinity-purified ME491 antigen and inhibit each other from binding in an inhibition radioimmunoassay. Competition immunoprecipitation experiments demonstrate that the ME491 and NKI/C-3 antibodies bind to NGA. Rabbit anti-ME491 idiotype serum recognizes determinants shared by NKI/C-3 and the anti-NGA MAbs. A competition immunoprecipitation experiment also confirms the identity of CD63, as defined by MAb RUU-SP 2.28, with the three melanoma antigens.


CONCLUSIONS
These data indicate that the MAGs defined by ME491 and NKI/C-3 as well as the anti-NGA antibodies are epitopes of the same molecule, which is identical to CD63 by both immunochemical and molecular genetic investigations.


CONCLUSIONS
Our results indicate that the data obtained in studies of these three melanoma antigens may be pooled, and we propose that the molecule recognized by these reagents be classified as CD63.
Oncology Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
D J
DJ
Demetrick
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D
Herlyn
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M
Tretiak
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D
Creasey
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H
Clevers
L A
LA
Donoso
C J
CJ
Vennegoor
W T
WT
Dixon
L M
LM
Jerry
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology; D000951:Antigens, Neoplasm / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D008545:Melanoma / Q000276:immunology*; D058950:Melanoma-Specific Antigens; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000276:immunology*; D010980:Platelet Membrane Glycoproteins / Q000276:immunology; D011233:Precipitin Tests; D011863:Radioimmunoassay; D060149:Tetraspanin 30; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000951:Antigens, Neoplasm; C554586:CD63 protein, human; D000939:Epitopes; D006023:Glycoproteins; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D010980:Platelet Membrane Glycoproteins; D060149:Tetraspanin 30