Immunologic and physical characterization of human chorionic gonadotropin (hCG) secreted by tumors.

ABSTRACT Plasma, urine and tumor extracts of patients with hCG-secreting tumors were examined for the presence of altered forms of hCG and its subunits by chromatography on a calibrated Sephadex G-100 column. Each eluate was radio-immunoassayed in homologous hCG, hCGα and hCGβ assays. All patients' tumors secreted intact hCG as the predominant form of that hormone. In addition, all patients had at least one of the hCG subunits readily detectable in urine and proportionally smaller amounts in plasma, possibly reflecting differences among the plasma half-lives of hCG and its subunits. Since subunits and other aberrant forms of hCG were present in both urine and plasma, the altered forms of hCG were not an artifact of excretion. Extracts of tumor tissue strongly suggested that altered forms of hCG arise during synthesis. Qualitative and quantitative differences of hCG and its subunits extracted from the primary tumor and its metastases suggest that in vivo cloning of tumor cells may occur.