title: Consideration and implications of tumor antigenic expression.
abstract: This review is an attempt to simplify the myriad descriptions of tumor antigens, by considering such antigens in the perspective of their mechanisms of formation. We believe that most and possibly all tumor antigens previously described and currently under study will ultimately fit into one of the categories discussed in this article, since there are only a finite number of biochemical mechanisms for producing new antigens in any cell--cancerous or otherwise. Pragmatically, we view the vagaries of expression of tumor antigens as among their most important properties, and the search for tumor antigens has in fact opened a Pandora's box of molecular variability. Large tumor masses consisting of multiple subclones with different karyotypes, chromosomal anomalies and mutations would appear to be capable of expressing a motley group of tumor antigens. To the best of our knowledge, no tumor antigen has been shown to be necessary and causal in transformation, except in virally-induced tumors. The presence of tumor antigens appears to be coincidental and reflects dedifferentiation and karyotypic, metabolic and nutritional variations occurring in tumors. Undoubtedly, some antigens may give a tumor a selective advantage of growth, metabolism or metastatic potential, but many antigens may simply reflect the vagaries of the tumor cell. The intratumor and intertumor variations of tumor antigens, their mechanisms of origin and their rather uncanny capabilities to change their phenotype--antigen expression--secondary to environmental selection during tumor expansion or following therapy should be kept in mind when tumor antigens and immunotherapy are considered.
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000302:isolation & purification; D001789:Blood Group Antigens; D002272:Carcinoembryonic Antigen / Q000302:isolation & purification; D002471:Cell Transformation, Neoplastic; D003854:Deoxyribonucleotides / Q000378:metabolism; D007167:Immunotherapy; D008297:Male; D051379:Mice; D009154:Mutation; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000276:immunology / Q000628:therapy; D051381:Rats
chemical_list: D000951:Antigens, Neoplasm; D001789:Blood Group Antigens; D002272:Carcinoembryonic Antigen; D003854:Deoxyribonucleotides