Tumor markers of the central nervous system: biological basis and clinical relevance

Markers in form of tumor-associated antigens have been identified in a variety of human tumors including those of the central nervous system. As their biological function is not yet clear, they are detectable at present only by various immunological means. Immunodiffusion, counter-current electrophoresis, immunofluorescence, and radioimmunoassays have been used to investigate sera of patients with gliomas and other intracranial tumors for the presence of circulating antibodies directed against glioma-associated polypeptides. In our own studies, 75% of the glioma patients' sera contained cross-reacting antibodies, whereas sera from a variety of cancer patients with diseases other than glioma, as well as from patients without cancer, were negative in this respect. These circulating antibodies were used to monitor the course of the disease in glioma patients undergoing chemotherapy. A correlation between the antibody titer and the extent of the disease, as revealed by computer tomography, could be observed. Our findings are comparable with a variety of other reports on glioma-associated antigens, including astrocytin and malignin. Finally, the specificity of these tumor markers as well as the sensitivity of their detection test will be evaluated with respect to their clinical utility.