Free α-subunit, free β-subunit of human chorionic gonadotropin (hCG), and intact hCG in sera of healthy individuals and testicular cancer patients

Abstract

To determine the serum concentrations of human chorionic gonadotropin (hCG), its free β-subunit (hCGβ), and the free α-subunit (free a) common to all human glycoprotein hormones under physiological and pathological conditions, we developed monoclonal antibody-based immunoenzymometric assays. Free α-subunit was detected in the sera of all healthy individuals of both sexes; hCG was measurable in sera of 54% of the men, and 46% were positive for free hCGβ in nonpregnant women, 69.5% were positive for hCG, 68.4% for the free α-subunit. Pathological conditions, i.e., hCG-producing tumors, were studied in vitro and in vivo. In vitro, the concentrations of hCG, free hCGα, and free α in tissue-culture supernates of a choriocarcinoma cell-line ("JAR") showed a parallel pattern during time-course analysis. In vivo, in long-term follow-up studies of 13 patients with testicular cancer, serum concentrations of the three analytes paralleled each other, whether the disease was in remission or not. Because of a selective increase of free hCGβ and free α in 27% of seminomatous tumor patients and in 13% of the nonseminomatous patients, the percentage of tumor-marker-positive sera was increased from 15% to 42% and 57% to 70%, respectively, by the additional measurement of free hCGβ and free a. Thus hCG, free hCGα, and free α are physiologically present in a high percentage of the sera from healthy men, and the determination of free hCGα and free a, although not of prognostic value, improves the diagnostic possibilities in patients with testicular cancer.