Qualitative and quantitative analyses of human chorionic gonadotropin and its subunits produced by malignant tumors

Abstract

Human chorionic gonadotropin (hCG) and its subunits in plasma, urine, ascites, and tumor extracts from four patients with hCG-producing tumors (undifferentiated cell carcinoma and choriocarcinoma of the bladder, malignant teratoma of the retroperitoneum, and pancreatic carcinoma) were measured by the radioimmunoassays specific to each component. While both free alpha and beta subunits as well as the whole molecule of hCG were found in all these samples, the proportion of beta subunit was much higher in these tumor extracts than in the placental extracts. Since the alpha and beta subunits are known to be translated from separate mRNAs, such increase of subunit is probably due to the predominant increase of mRNA encoding beta subunit of hCG in the hCG-producing tumors. Gel filtration of the extracts of these four tumors on Sephadex G-100 and G-150 columns demonstrated a heterogeneity of hCG, alpha, and beta subunits in these tumor extracts, and the elution profiles of plasma, urine and tumor extracts were slightly different. Lower molecular weight forms of hCG and its beta subunit were present in all urine samples. The significance of these heterogeneities remains to be elucidated.