Serum glycoprotein hormone alpha subunit levels in patients with cancer

The classification, functions and clinical use of different isoforms of HCG

HCG is composed of two subunits, HCGalpha and HCGbeta. During early pregnancy, HCG stimulates progesterone production in the corpus luteum, and injection of HCG is widely used to induce ovulation in assisted reproduction treatment (ART). Under experimental conditions, the free subunits have been shown to exert functions other than those of HCG, but the relevance of these remains to be determined. Intact HCG, free subunits and degraded forms of these occur in biological fluids, and determinations of these are important for diagnosis and monitoring of pregnancy, pregnancy-related disorders and several types of cancer. Development of optimal methods for the various forms has been hampered by lack of appropriate standards and expression of the concentrations of the various forms in units that are not comparable. Furthermore, the nomenclature for HCG assays is confusing and in some cases misleading. These problems can now be solved; a uniform nomenclature has been established, and new standards are available for HCG, its subunits HCGalpha and HCGbeta, the partially degraded or nicked forms of HCG and HCGbeta, and the beta-core fragment. This review describes the biochemical and biological background for the clinical use of determinations of various forms of HCG. The clinical use of HCG and studies on HCG vaccines are briefly reviewed.

Silencing of the gene for the alpha-subunit of human chorionic gonadotropin by the embryonic transcription factor Oct-3/4

CG is required for maintenance of the corpus luteum during pregnancy in higher primates. As CG is a heterodimeric molecule, some form of coordinated control must be maintained over the transcription of its two subunit genes. We recently found that expression of human CG beta-subunit (hCGbeta) in JAr human choriocarcinoma cells was almost completely silenced by the embryonic transcription factor Oct-3/4, which bound to a unique ACAATAATCA octameric sequence in the hCGbeta gene promoter. Here we report that Oct-3/4 is also a potent inhibitor of hCG alpha-subunit (hCGalpha) expression in JAr cells. Oct-3/4 reduced human GH reporter expression from the -170 hCGalpha promoter in either the presence or absence of cAMP by about 70% in transient cotransfection assays, but had no effect on expression from either the -148 hCGalpha or the -99 hCGalpha promoter. Unexpectedly, no Oct-3/ 4-binding site was identified within the -170 to -148 region of the hCGalpha promoter, although one was found around position -115 by both methylation interference footprinting and electrophoretic mobility shift assays. Site-directed mutagenesis of this binding site destroyed the affinity of the promoter for Oct-3/4, but did not affect repression of the promoter. Therefore, inhibition of hCGalpha gene transcription by Oct-3/4 appears not to involve direct binding of this factor to the site responsible for silencing. When stably transfected into JAr cells, Oct-3/4 reduced the amounts of both endogenous hCGalpha mRNA and protein by 70-80%. Oct-3/4 is therefore capable of silencing both hCGalpha and hCGbeta gene expression. We suggest that as the trophoblast begins to form, reduction of Oct-3/4 expression permits the coordinated onset of transcription from the hCGalpha and hCGbeta genes.

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.

Urinary chorionic gonadotropin subunits and beta-core in nonpregnant women. A study of benign and malignant gynecologic disorders

BACKGROUND

The presence of urinary excretion products of human chorionic gonadotropin (hCG) has been proposed as a tumor marker. To ascertain the clinical value in gynecologic cancers, the authors studied 612 nonpregnant women.

METHODS

Three different assays in four clinical groups were compared: no disease, benign disease, malignant disease, and complete remission of previously treated malignant disease. The assays were for the urinary beta-core, "total" beta-hCG, and free alpha-subunit.

RESULTS

Measurement of the alpha-subunit was of no obvious clinical value. In some patients with benign disease, hCG metabolites were elevated. In the 141 patients with active gynecologic malignancy the sensitivity of the total beta-hCG assay was 47% and that of the beta-core assay was 36%. The specificities were 80.3% and 90.4%, respectively. Advanced cancers generally had higher levels of total beta-hCG and beta-core. Squamous cell and poorly differentiated cervical tumors had higher levels of total beta-hCG than did adenocarcinomas and well-differentiated cervical tumors. Invasive, serous, endometrioid, and germ cell ovarian tumors had higher total beta-hCG, beta-core, and alpha-subunit levels than did borderline, mucinous, and clear cell ovarian tumors. Six of 16 patients with disease in complete remission had elevated levels.

CONCLUSION

The excretion of hCG and its metabolic fragments is a common event in gynecologic cancer, but sensitivity and specificity are low, and there is little consistent relationship between tumor stage and histologic type.

Differential diagnostic patterns of lung neuroendocrine tumours

A series of 3 tumourlets (TLs), 81 typical carcinoids (TCs), 14 atypical carcinoids (ACs) (well-differentiated neuroendocrine carcinomas, WDNCs) and 24 small cell-intermediate cell carcinomas (SCC-ICCs) of the lung were studied. Histopathological features were correlated with amine and peptide hormone immunoreactivity and with clinical data. All types of tumours expressed general neuroendocrine (NE) markers: Grimelius positivity and chromogranins were detected more frequently in well-differentiated (TLs, TCs) than in less well differentiated tumours [ACs (WDNCs) and SCC-ICCs] whereas neuron specific enolase (NSE) was prominent in the latter tumours. TLs and peripheral TCs were benign, often showing a paraganglioid pattern and frequently expressing gastrin-releasing peptide (GRP), which is present in the peripheral airways of normal lung. Central TCs were associated with lymph node metastases in 8.5% of the cases, frequently had a trabecular architecture, often associated with human milk fat globule 2 (HMFG2)-positive acinar and rosette-like structures, and were mainly immunostained for the alpha-subunit of human chorionic gonadotrophin (alpha-hCG) and serotonin. ACs (WDNCs) were associated with intrathoracic and/or extrathoracic metastases in 57.1% of the cases with a mortality rate of 35.7%. Their histological and cytological features were intermediate between those of TCs and SCC-ICCs. ACs (WDNCs) expressed serotonin and alpha-hCG less frequently than TCs. All SCC-ICCs were surgically treated and displayed a mortality rate of 91.6% with a mean survival of 10.2 months after operation. These tumours were characterized by high expression of HMFG2 and NSE, while the expression of both orthotopic (serotonin, GRP) and ectopic (ACTH) specific NE substances was very low. Since all TCs (either central or peripheral) had a favourable outcome, while about 36% of ACs (WDNCs) were fatal, the latter seem more appropriately designated "well-differentiated NE carcinomas". The differential diagnosis between different NE tumours of the lung is important and is mainly based on morphology. Both panendocrine and specific immunohistochemical markers are helpful in distinguishing the less aggressive, mostly benign varieties from the more malignant varieties.

Expression of alpha- and beta-human chorionic gonadotropin subunits in cultured human cells

We surveyed several human cell lines for production of alpha- and beta-human chorionic gonadotropin (hCG) under a variety of conditions known to induce gene expression. alpha- and beta-hCG subunits were monitored in culture media by specific radioimmunoassays and were shown to be quite sensitive to serum refeeding and growth state of all cell types studied. The permanent line JEG-3 secreted both alpha- and beta-subunits whereas HeLa cells secreted only the alpha-subunit. Production of both subunits was augmented in these permanent cell lines, for each growth state, by pretreating cells with 5-azacytidine; in contrast, spontaneous beta-hCG production by normal human fibroblasts (four of six strains) was only rarely increased after 5-azacytidine treatment, and more often was suppressed by 30 to 40%. Three of five strains from inherited chromosomal breakage syndromes produced immunoassayable beta-hCG spontaneously, two of which increased secretion upon treatment with either UV or mitomycin C. Surprisingly, one normal cell strain of fetal origin was induced to secrete alpha-hCG, but not beta-hCG, after UV irradiation. JEG-3 and HeLa cells produced detectable cognate mRNA for alpha- or beta-hCG subunits or both by Northern and S1 nuclease protection analyses, whereas such transcripts from untransformed human fibroblasts were consistently below detectable levels. Quantitation of beta-hCG mRNA by RNA:RNA annealing kinetics indicates that even the fibroblast strain producing the highest secreted beta-hCG levels contained cognate mRNAs at only approximately 0.1 per cell. We conclude that hCG expression in human fibroblasts is strongly repressed at the transcriptional level, although a variety of conditions (growth state, serum refeeding, cell senescence, or DNA damage) can affect the level of "leaky" expression, at least in some responding fraction of cells.

[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.

Free alpha-subunit response to gonadotropin-releasing hormone in women with polycystic ovaries

The response of glycoprotein hormone free alpha-subunit to gonadotropin-releasing hormone (GnRH) was evaluated in 12 women with polycystic ovaries (PCOs). Six of these women were premedicated for 3 days with micronized 17 beta-estradiol before receiving a 100-micrograms bolus of GnRH. In nonmedicated PCO patients, GnRH did not significantly alter basal free alpha-subunit levels. In four of the six PCO patients receiving estrogen premedication, a significant increase in free alpha-subunit was observed; these four patients had low progesterone levels at the time of the GnRH test. Among the six premedicated patients, two had elevated (greater than 4 ng/ml) progesterone levels, and the GnRH tests showed no significant effect on the levels of free alpha-subunit. The study revealed a dissociation between the free alpha-subunit responses to GnRH and the responses of luteinizing hormone; a closer relationship was observed between free alpha-subunit and follicle-stimulating hormone responses. It was concluded that the lack of a free alpha-subunit response to GnRH in PCO patients is not due to a primary inability of the pituitary gonadotroph to produce free alpha-subunit but is a consequence of an altered estrogenic milieu, and a free alpha-subunit response to GnRH may reflect the replenishment of both follicle-stimulating hormone and luteinizing hormone in the gonadotrope.

The value of immunohistochemistry in medullary thyroid carcinoma: a systematic study of 30 cases

Thirty cases of medullary thyroid carcinoma were investigated by immunoperoxidase staining techniques to evaluate the diagnostic significance of neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), somatostatin (SOM), a-subunit of human chorionic gonadotrophin (a-hCG), serotonin (5-HT) and adrenocorticotropic hormone (ACTH) immunoreactivity as diagnostic markers in comparison to different calcitonin (CT) staining patterns. Twenty three cases exhibited a strong (group I) or moderate (group II) staining intensity for CT and did not need further immunocytochemical proof for classifying them as medullary carcinoma. From seven cases which showed only a weak or borderline CT-immunoreactivity (group III), six stained positively for NSE and four positively for CEA. SOM-positive cells were identified in six cases and a-hCG or 5-HT-positive cells respectively in three cases of group III. Twenty follicular and 20 papillary carcinomas also included in this study did not react with any of the above mentioned antibodies. Therefore, NSE and CEA represent useful additional diagnostic markers particularly for the identification of medullary carcinoma with weak or borderline CT-immunoreactivity. The identification of other peptides may also be helpful in demarcating it from thyroid tumours of follicular cell origin.

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.

Hyperthyroidism and acromegaly due to a thyrotropin- and growth hormone-secreting pituitary tumor. Lack of hormonal response to bromocriptine

A 47-year-old woman with acromegaly and hyperthyroidism was found to have an inappropriately normal serum thyrotropin level (1.5 to 2.5 microU/ml) that responded poorly to thyrotropin-releasing hormone but showed partial responsiveness to changes in circulating thyroid hormones. Serum alpha-subunit levels were high-normal and showed a normal response to thyrotropin-releasing hormone. Growth hormone and thyrotropin hypersecretion persisted despite radiotherapy and bromocriptine treatment. Selective trans-sphenoidal removal of a pituitary adenoma led to normalization of both growth hormone and thyrotropin levels. Both thyrotropes and somatotropes were demonstrated in the adenoma by the immunoperoxidase technique and electron microscopy.

Glycoprotein-hormone alpha-chain production by pancreatic endocrine tumors: a specific marker for malignancy. Immunocytochemical analysis of tumors of 155 patients

Human chorionic gonadotropin (hCG) or its alpha- and beta-subunits have been proposed as specific quantitative markers for malignant pancreatic endocrine tumors. Since proof of malignancy of pancreatic endocrine tumors is difficult early in the course of the illness, we tested retrospectively a series of 157 pancreatic endocrine tumors of 155 patients for alpha- or beta-subunits of hCG by immunocytochemistry. Human CG-alpha-immunoreactive cells were present in 42 of 56 (75%) functioning malignant pancreatic endocrine tumors but in only one, possibly benign, glucagonoma of 67 functioning benign tumors, in only one of 17 nonfunctioning malignant and in none of 17 nonfunctioning benign tumors. No beta-hCG-immunoreactivity was localized in the tumors. Human CG-alpha appears to be a reliable quantitative and qualitative marker for malignancy in functioning pancreatic endocrine tumors.

Anterior pituitary hormone levels in the cerebrospinal fluid of patients with pituitary and parasellar tumors

Cerebrospinal fluid (CSF) concentrations of growth hormone, prolactin (PRL), adrenocorticotropin, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, and the glycoprotein hormone alpha subunit were determined in 30 patients with pituitary and parasellar tumors. Although many of the patients had elevated hormone levels, no differentiation between patients with intrasellar tumors and those with pituitary tumors with suprasellar extension or primary suprasellar tumors could be made based upon the absolute CSF hormone concentration. A highly significant correlation between serum and CSF PRL concentrations was found (r = 0.87; P less than 0.001), suggesting that CSF PRL is derived from the serum. No correlation was found between the serum and CSF concentrations of the other anterior pituitary hormones.

Serum glycoprotein hormone alpha subunit, hormone receptors and disease stage in patients with breast cancer

The concentration of the common alpha subunit of the glycoprotein hormones was high in the serum of 21/56 (38%) of premenopausal patients and 22/106 (21%) of postmenopausal patients with primary breast cancer, at the time of presentation. 7/59 (12%) of patients with benign disease also had high alpha subunit levels. Tumour cytosol oestrogen and progesterone receptor status was determined in 80% of the patients with cancer, and there was a trend towards higher alpha levels in patients without receptors, but this was not statistically significant. In the premenopausal patients with cancer there was a significant correlation between alpha subunit level and disease stage, R = 0.47, P = 0.0001, but not in the postmenopausal patients. In view of the correlation with disease stage, high levels of alpha subunit in premenopausal patients with breast cancer at presentation with the primary tumour may indicate poor prognosis.