The Production and Characterization of a Monoclonal Antibody to a Naturally Occurring Aminomalonic Acid Epitope and a Comparison with an Antibody to a Synthetically Derived Aminomalonic Acid Epitope

The goal for this project is to undertake the first step in the study of blocking metastasis by a monoclonal antibody. The long range goal of this line of research is to study a novel mechanism for the blocking of tumor metastasis in general and prostatic cancer metastasis in particular. The problem that this addresses is the growing number of cases of prostatic cancer in the increasingly aging male population. This cancer is not lethal unless it metastasizes, yet there is no cure for the metastatic disease. The inherent specificity of a monoclonal antibody combined with the uniqueness of the epitope and its presumed importance as an adhesion molecule vital for metastasis make this an interesting approach to cancer treatment. The mAb-Amasyn antibody (Ortho Diagnostic Systems Clone #57D4B6G2B11), developed by immunizing mice with a synthetic aminomalonic acid (Ama) epitope made by the conjugation of N-acetyl Ama ethyl amide to BSA (Koch et al.), was used to identify a source (human prostate cancer cell line, DU-145) of naturally occurring anti-Amasyn antibody-reactive protein (DU-145 Ag). A monoclonal antibody, anti-Amanat (IgG1 kappa), to this antigen was produced which binds specifically to synthetic Ama epitopes and when tested with the anti-Amasyn antibody, binds with partial additivity to synthetic and naturally occurring Ama epitopes. This antibody does not cross-react with fresh frozen normal human prostate or any other normal tissues tested. This antibody may be more specific for the DU-145 antigen than the anti-Amasyn antibody. The DU-145 Ag contains an acid-labile antibody binding site, possibly indicating the presence of Ama, and is upregulated on cells associated with a more metastatic phenotype. This antigen is a 200 kD glycoprotein containing GlcNAc with a pI of 4.7. This antigen may be part of a metastasis-associated adhesion molecule. The results indicate that the anti-Amanat antibody may be able to play a role in histological diagnosis, in vivo detection, and eventual therapy of prostatic cancer. They also affirm the importance of deriving an antibody from a naturally occurring protein