The circulating alpha subunit of human chorionic gonadotrophin in gynaecologic tumours

Pathophysiological importance of various molecular forms of human choriogonadotropin

Human chorionic gonadotropin (hCG), its subunits and fragments are widely used for diagnostic purposes. In addition to the diagnosis of pregnancy and pregnancy related disorders, hCG determinations are used for diagnosis of trophoblastic and recently also nontrophoblastic tumors. The use for diagnosis of nontrophoblastic tumors requires highly specific and ultrasensitive assays. With these, it is possible to measure the concentrations of both hCG, the free beta-subunits and the so called beta-core fragment in healthy subjects. Therefore it is important to establish reference values for these and also to be aware of the influence of physiological factors on the serum and urine concentrations. Improved standardization of the assay methods is also essential for these novel applications of hCG determinations to become useful.

Measurement of human chorionic gonadotropin-related immunoreactivity in serum, ascites and tumour cysts of patients with gynaecologic malignancies

Human chorionic gonadotropin (hCG)-like molecules have been reported to be elevated in a substantial fraction of serum samples from patients with various gynaecologic tumours and have been discussed as possible markers in these malignancies. Employing highly sensitive and specific immunoradiometric assays, we determined total hCG-related immunoreactivity (hCG/hCG beta), as well as free alpha-subunit (alpha-SU), common to all glycoprotein hormones, in serum (n = 106) and malignant effusions (n = 26) of women with gynaecologic malignancies. For comparison, we also measured hCG/hCG beta in nonmalignant ascitic fluids (n = 21). HCG/hCG beta serum levels were elevated (> 5 IU L-1) in 39 of 106 patients (37%) with gynaecologic malignancies, whereas free alpha-SU was above normal range only in seven (6.6%). Frequencies of hCG/hCG beta elevations were similar in women with endometrial, (n = 39), cervical (n = 40) and ovarian (n = 27) cancer, being 30%, 35% and 41%, respectively. In malignant ascites (n = 15) and tumour cyst fluids (n = 11) of patients with ovarian cancer, hCG/hCG beta concentrations were significantly higher than in the corresponding serum samples and benign ascitic samples. Free alpha-SU, on the other hand, was increased in only one of 26 malignant effusions. In conclusion, hCG/hCG beta is frequently elevated in serum of patients with endometrial, cervical and ovarian cancer and may serve as a tumour marker in these malignancies, particularly in patients where other markers are negative. In this respect, analysis of ascitic or tumour cyst fluids may be of higher diagnostic value as serum measurements.

[Free alpha-subunit glycoprotein hormones: physiological and pathological data]

The glycoprotein hormone alpha-subunit is secreted as a free molecule as well as a molecule combined to a glycoprotein hormone beta-subunit. In human subjects, plasma levels of the free alpha-subunit were measured by means of a specific radioimmunoassay. Plasma concentrations were high during the neonatal period, then decreased to a nadir at the age of 6 years. A significant pubertal increase occurred in both sexes, more pronounced in girls. In female subjects mean levels (+/- SEM) were 0.21 +/- 0.05 before puberty and 0.51 +/- 0.03 ng 1 degrees IRP-hCG alpha/ml in follicular phase. During menstrual cycle, a typical preovulatory surge was seen simultaneous with the LH surge. During aging, plasma levels increased slowly in males, abruptly in menopausal females. The pituitary reserve as assessed by LH-RH stimulation test (100 micrograms i.v./m2) exhibited a significant pubertal maturation in boys and girls. Chronic administration of LH-RH agonist induced a marked increase of alpha-subunit levels, whereas LH levels were deeply suppressed. LH-RH injections in children treated for precocious puberty with a LH-RH agonist induced a significant release of alpha-subunit despite an almost complete abolition of LH release. In conclusion, from a quantitative point of view, the glyco-protein hormone alpha-subunit is a major secretory product of the pituitary. It seems that there is a specific regulation of its secretion, resembling but not identical to LH secretion regulation. Whether or not it plays a biological role remains uncertain.

High frequency of incomplete human chorionic gonadotropin in patients with testicular seminoma

We measured human chorionic gonadotropin by 2 immunometric assays that require that the entire human chorionic gonadotropin molecule is intact, and by a competitive radioimmunoassay that measures intact human chorionic gonadotropin and its free beta-chain. The sera tested were samples from male cancer patients with elevated human chorionic gonadotropin levels obtained by the radioimmunoassay method. Elevated levels were confirmed in 67 of 92 samples (72 per cent) with the immunometric methods. However, in 25 of 97 patients (28 per cent) elevated human chorionic gonadotropin was found with the radioimmunoassay, whereas the values were in the normal range when measured with the immunometric assays. These discrepancies were found in 22 patients with seminomatous tumors, including 2 extragonadal germ cell tumors, which constitutes 42 per cent of all seminoma patients tested. Of the remaining 3 discrepant patients 2 had lung cancer and 1 had metastases from an unknown primary cancer.

Ectopic production of human chorionic gonadotrophin-like material by breast cancer

Human chorionic gonadotrophin (hCG) is a placental protein whose ectopic secretion by nontrophoblast tumors has been claimed to be of clinical relevance. Serum levels of hCG were measured in 570 patients with breast disease. A double-antibody radioimmunoassay (RIA) using antisera to hCG-beta was employed. Approximately 14% of patients with breast cancer were found to have elevated serum hCG levels. Such raised titers were not stage- or tumor-type-related, but occurred only in postmenopausal subjects. Further study showed that those patients with elevated hCG levels also had raised levels of human luteinizing hormone (hLH). Assay cross-reactivity was shown to account for the "spurious" hCG elevations. An immunocytochemical study also failed to find hCG an ectopic breast tumor constituent and/or product. It is concluded that hCG is not produced by breast tumors and has no clinical utility.

Excretion of a tumor-associated trypsin inhibitor (TATI) in urine of patients with gynecological malignancy

In earlier studies we reported the finding of a tumor-associated peptide that also occurred at high concentrations in early amniotic fluid. Determination of the N-terminal sequence of this peptide revealed that it is closely related or identical to the pancreatic secretory trypsin inhibitor. Therefore, the peptide is called tumor-associated trypsin inhibitor (TATI). The concentration of TATI was determined by radioimmunoassay in the urine of 148 patients with various forms of gynecologic malignancy and in a reference population consisting of 98 patients with non-malignant gynecologic disease, and also in 40 patients with severe infections or inflammatory disease. In the reference population, the median urinary concentration of TATI was 22 micrograms/g creatinine and the central 95% reference interval was 7-50 micrograms/g creatinine. Elevated urinary levels were observed in 53% of all patients with gynecologic cancer, in 63% of those with active disease and 26% of those in clinical remission. The highest urinary TATI level (11,000 micrograms/g creatinine) was over 200 times the upper limit of the reference range. Patients with cervical cancer had the highest frequency of elevated values. Increased excretion of TATI was also observed in patients with severe bronchopulmonary infections and pancreatitis. Although increased excretion of TATI is not cancer-specific, the distinction by elevated levels of TATI between malignant and nonmalignant gynecologic disease is better than by most other putative tumor markers, and the increased excretion of TATI in patients with active disease can be important for the understanding of tumor biology.

Distribution and characterization of alpha hCG in the serum and tumor cytosol of patients with breast cancer

Serum and tumor tissue from breast cancer patients were evaluated for the presence of alpha subunit of hCG, by means of the specific radioimmunoassay. Elevated serum levels occurred in 0/50 (0%) of normal female controls, 1/17 (6%) of patients with benign breast disease, 3/53 (6%) of patients with primary breast cancer, and 12/84 (14%) of patients with metastatic breast cancer. Cytosols from 10/56 (18%) primary tumors and 10/37 (28%) metastatic tumors were found to contain the alpha subunit. Comparison of serum and tumor cytosol levels in nine patients with metastatic disease showed a correspondence between elevated cytosol levels and elevated serum levels. No similar correspondence in 25 patients with primary disease was observed. Alpha subunit was isolated from one tumor cytosol and was characterized with respect to its immunochemical cross-reactivity and molecular weight as compared with native alpha subunit from hCG. For both parameters, the native and ectopic alpha subunit were found to be identical.