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

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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 α and β subunits as well as the whole molecule of hCG were found in all these samples, the proportion of β subunit was much higher in these tumor extracts than in the placental extracts. Since the α and β subunits are known to be translated from separate mRNAs, such increase of subunit is probably due to the predominant increase of mRNA encoding β 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, α, and β 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 β subunit were present in all urine samples. The significance of these heterogeneities remains to be elucidated.