Characterization of cluster 13: The epithelial/carcinoma antigen recognized by MAb RS7

Authors

  • Rhona Stein,

    1. Garden State Cancer Center at the Center for Molecular Medicine and Immunology, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
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  • Amartya Basu,

    1. Department of Biochemistry and Molecular Biology, Graduate School of Biomedical Science, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
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  • David M. Goldenberg,

    Corresponding author
    1. Garden State Cancer Center at the Center for Molecular Medicine and Immunology, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
    • Center for Molecular Medicine and Immunology, 1 Bruce Street, Newark, NJ 07103, USA
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  • Kenneth O. Lloyd,

    1. Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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  • M Jules. Mattes

    1. Garden State Cancer Center at the Center for Molecular Medicine and Immunology, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
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Abstract

Cluster 13 was defined by 2 independently derived murine monoclonal antibodies (MAbs), RS7 (IgG1) and MR54 (IgG2a), which were raised against human squamous-cell carcinoma of the lung and a human ovarian-carcinoma cell line, respectively, Immunologic and biochemical evidence demonstrated that RS7 and MR54, as well as 2 additional MAbs, MR6 (IgG2a) and MR23 (IgG1), generated in the same fusion as MR54, recognize the same antigen, a 46- to 48-kDa glycoprotein. Evaluation of the expression of antigen on the surface of tumor cell lines, Western blotting analyses, competitive binding studies, and double-determinant ELISA assays, support this conclusion. Two distinct epitopes are defined by these MAbs.

In order to further characterize this antigen, amino-acid-sequence analyses were performed on peptides derived from antigen purified by affinity chromatography with MAb RS7. The sequence data obtained from 2 peptides, which were independently generated by CNBr cleavage and trypsin digestion respectively indicated identity to GA733-1. The GA733-1 genomic DNA sequence predicted a type-1 membrane protein of 35 kDa, with 4 potential N-linked glycosylation sites. The GA733-1 protein product has not been identified previously, and MAbs to this tumor-associated antigen were not previously known.

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