Cancerous Immunoglobulins in Cancer Immunology

The expression of immunoglobulins by cancer cells have been known for two decades. However, the mechanisms of action behind these cancerous immunoglobulins (cIgG) are not well understood and may be different from immunoglobulins secreted by normal B lymphocytes. Therefore, the structural and functional roles of cIgG have been actively investigated to resolve this mystery. A monoclonal antibody, RP215, was generated in 1987 and was shown to react with a carbohydrate-associated epitope localized mainly on the heavy chains of cIgG but not on normal immunoglobulins. The knowledge of cIgG has been greatly advanced by using RP215 as a unique probe. Not only was RP215 shown to act as an anti-cIgG to induce apoptosis of cultured cancer cells in vitro/in vivo, it was also shown to elicit complement-dependent cytotoxicity (CDC) reactions to trigger lysis of cancer cells. It has now been established that besides serving to preserve growth/proliferation of cancer cells by capturing growth factors from the human serum, cIgG may also interact with certain human serum proteins which may be harmful to cancer cells. Thus, the hypothesis of dual functional roles of cIgG can be adequately explained in cancer immunology. Furthermore, RP215 may also be used to target cancer cells with surface bound cIgG for development of antibodybased anti-cancer drugs, provided that bioequivalent humanized RP215 is available for preclinical and clinical studies of immunotherapy.