Stimulation of human chorionic gonadotropin secretion by glucocorticoids

Aberrant trophoblastic differentiation in human cancer: An emerging novel therapeutic target (Review)

Various types of human cancer may develop aberrant trophoblastic differentiation, including histological changes and altered expression of β‑human chorionic gonadotropin (β‑hCG). Aberrant trophoblastic differentiation in epithelial cancer is usually associated with poor differentiation, tumor metastasis, unfavorable prognosis and treatment resistance. Since β‑hCG‑targeting vaccines have failed in an early phase II trial, it is crucial to obtain a better understanding of the molecular pathogenesis of trophoblastic differentiation in human cancer. The present review summarizes the clinical and translational research on this topic with the aim of accelerating the development of an effective targeted therapy. Ectopic expression of β‑hCG promotes proliferation, migration, invasion, vasculogenesis and epithelial‑mesenchymal transition (EMT) in vitro, and enhances metastatic and tumorigenic capabilities in vivo. Signaling cascades modulated by β‑hCG include the TGF‑β receptor pathway, EMT‑related pathways, the c‑MET receptor tyrosine kinase and mitogen‑activated protein kinase/ERK pathways, and the SMAD2/4 pathway. Taken together, these findings indicated that TGF‑β receptors, c‑MET and ERK1/2 are potential therapeutic targets. Nevertheless, further investigation on the molecular basis of aberrant trophoblastic differentiation is mandatory to improve the design of precision therapy for this aggressive type of human cancer.

Mitochondrial ROS Accumulation Contributes to Maternal Hypertension and Impaired Remodeling of Spiral Artery but Not IUGR in a Rat PE Model Caused by Maternal Glucocorticoid Exposure

Increased maternal glucocorticoid levels have been implicated as a risk factor for preeclampsia (PE) development. We found that pregnant rats exposed to dexamethasone (DEX) showed hallmarks of PE features, impaired spiral artery (SA) remodeling, and elevated circulatory levels of sFlt1, sEng IL-1β, and TNFα. Abnormal mitochondrial morphology and mitochondrial dysfunction in placentas occurred in DEX rats. Omics showed that a large spectrum of placental signaling pathways, including oxidative phosphorylation (OXPHOS), energy metabolism, inflammation, and insulin-like growth factor (IGF) system were affected in DEX rats. MitoTEMPO, a mitochondria-targeted antioxidant, alleviated maternal hypertension and renal damage, and improved SA remodeling, uteroplacental blood flow, and the placental vasculature network. It reversed several pathways, including OXPHOS and glutathione pathways. Moreover, DEX-induced impaired functions of human extravillous trophoblasts were associated with excess ROS caused by mitochondrial dysfunction. However, scavenging excess ROS did not improve intrauterine growth retardation (IUGR), and elevated circulatory sFlt1, sEng, IL-1β, and TNFα levels in DEX rats. Our data indicate that excess mitochondrial ROS contributes to trophoblast dysfunction, impaired SA remodeling, reduced uteroplacental blood flow, and maternal hypertension in the DEX-induced PE model, while increased sFlt1 and sEng levels and IUGR might be associated with inflammation and an impaired energy metabolism and IGF system.

Review: hCGs: different sources of production, different glycoforms and functions

Human chorionic gonadotropin (hCG) is the first hormonal message from the placenta to the mother. It is detectable in maternal blood two days after implantation and behaves like an agonist of LH stimulating progesterone secretion by the corpus luteum. hCG has also a role in quiescence of the myometrium and local immune tolerance. Specific to humans, hCG is a complex glycoprotein composed of two glycosylated subunits. The α-subunit is identical to the pituitary gonadotropin hormones (LH, FSH, TSH), contains two N-glycosylation sites, and is encoded by a single gene (CGA). By contrast the β-subunits are distinct in each of the hormones and confer receptor and biological specificity. The hCG β-subunit contains two sites of N-glycosylation and four sites of O-glycosylation and is encoded by a cluster of genes (CGB). In this review, we will stress the importance of hCG glycosylation state, which varies with the stage of pregnancy, its source of production and in the pathology. It is well established that hCG is mainly secreted by the syncytiotrophoblast into maternal blood where it peaks around 8-10 weeks of gestation (WG). The invasive extravillous trophoblast also secretes hCG, and in particular like choriocarcinoma cells, hyperglycosylated forms of hCG (hCG-H). In maternal blood hCG-H is high during early first trimester. In addition to its endocrine role, hCG has autocrine and paracrine roles. It promotes formation of the syncytiotrophoblast and angiogenesis through LHCG receptor. In contrast, hCG-H stimulates trophoblast invasion and angiogenesis by interacting with the TGFβ receptor 2. hCG is largely used in antenatal screening and hCG-H represents a serum marker of early trophoblast invasion. Other abnormally glycosylated hCG are described in aneuploidies. In conclusion, hCG is the major pregnancy glycoprotein hormone, whose maternal concentration and glycan structure change all along pregnancy. Depending on its source of production, glycoforms of hCG display different biological activities and functions that are essential for pregnancy outcome.

11β-Hydroxysteroid Dehydrogenase Inhibitor Carbenoxolone Stimulates Chorionic Gonadotropin Secretion from Human Term Cytotrophoblast Cells Differentiated In Vitro *

PROBLEM

To investigate the effect of altering local glucocorticoid concentration on human chorionic gonadotropin (hCG) production by cultured placental trophoblast cells.

METHOD OF STUDY

Human placental trophoblasts were isolated from fresh placentas. Cytotrophoblasts were purified and placed into 24-well multiplates. For cultivation Dulbecco's modified Eagle's medium (DMEM) with 15 mm HEPES and 15% FBS was used. 11beta-Hydroxysteroid dehydrogenase (11beta-HSD) activity and its inhibition by carbenoxolone (CE) were measured in cultured cells. Cultures were exposed to CE for 16-20 hr. Overnight production of hCG was measured by radioimmunoassay in control and treated cells.

RESULTS

The 11beta-HSD activity in these cultures was inhibited by nm concentrations of CE, the apparent Ki being 2.5 nm. Inhibition of 11beta-HSD activity with 0.1 nm CE resulted in 1.5-fold increase in the production of hCG.

CONCLUSIONS

Increasing local glucocorticoid concentration by the inhibition of 11beta-HSD results in higher hCG secretion, which in turn enhance cell differentiation.

Effect of antenatal dexamethasone therapy on maternal plasma human chorionic gonadotrophin, oestradiol and progesterone

The aim of this study was to determine whether the current regimen of dexamethasone administration to induce fetal lung maturation affected the circulating concentrations of placental hormone. A standard regimen of dexamethasone that comprised two doses of 12-mg intramuscular injections, 12 h apart was administered to 12 pregnant women to promote fetal lung maturation in anticipation of premature delivery before 34 completed weeks of gestation. Blood samples were collected before starting the dexamethasone therapy, 24 h, and 48 h after completing therapy for the measurement of the plasma concentrations of human chorionic gonadotrophin (HCG), oestradiol and progesterone. There was a progressive fall in the plasma concentrations of HCG following dexamethasone therapy (P = 0.049 and P = 0.034, 24-h and 48-h post therapy respectively). There was an initial fall in the plasma concentrations of oestradiol after dexamethasone therapy (z = 3.059; P = 0.002, 24-h post therapy), which recovered by 48 h (P = 0.239). There was no difference between the plasma concentrations of progesterone at the three time points. The effect of dexamethasone on HCG concentrations suggests that it has a direct inhibitory effect on placental hormone synthesis or secretion. Further studies are needed to define the mechanism of action of dexamethasone on placental HCG production.

Antibody directed enzyme prodrug therapy (ADEPT). A review of some theoretical, experimental and clinical aspects

The concept of generating cytotoxic agents from non-toxic prodrugs at tumour sites by antibody vectored enzyme introduces a wide range of opportunities. Various prodrug-enzyme combinations have been described and encouraging results reported in xenograft models. Whilst the mouse model is a valuable tool in this approach translation to the human patient may expose more complex issues. The objective of restricting drug action to tumour sites and thus allowing greatly increased cytotoxic action requires more precise restriction of enzyme activity to tumour sites than has been achieved with an antibody vector and natural clearance alone. Assisted clearance mechanisms have been found effective. Alternatively, or additionally, the difference between prodrug and active drug creates the opportunity to degrade active drug selectively in blood and thus protect normal tissues. In order to give more than one cycle of treatment it will be necessary for the antibody-enzyme conjugate to be nonimmunogenic or for the concurrent administration of immunosuppressive agents. A pilot scale clinical trial with a prototype prodrug indicated the feasibility of antibody directed enzyme prodrug therapy (ADEPT).

Effect of ethanol and progesterone on monoamine oxidase activity in cultured cells of human term placenta

OBJECTIVE

The aim of this study was to evaluate the effect of ethanol and progesterone on the monoamine oxidase activity in cultured human term placental cells.

STUDY DESIGN

Human placental cells were prepared from normal human term placentas by enzymatic dispersion in Dulbecco's modified Eagle medium. The viability of placental cells prepared by our method was 90%, and the yield of placental cells was 0.6 x 10(6) cells per gram of wet placental tissue. Five milliliters of Dulbecco's modified Eagle medium containing 3 x 10(5) placental cells was plated in a 25 cm2 flask and cultured for 8 days in an incubator at 37 degrees C under an atmosphere of 5% carbon dioxide and 95% oxygen with a saturated humidity. During the culture period the culture medium was replenished every 2 days. A confluent monolayer condition was achieved after 8 days in culture. The cultured placental cells were treated with different concentrations of ethanol (0, 34.6, and 69.2 mmol/L) and progesterone (0, 16, and 32 mumol/L) on day 8 of culture for 48 hours. At the end of treatment placental cells from control and treated flasks were harvested for the analysis of monoamine oxidase activity by spectrophotometry. The effects of ethanol and progesterone on cultured placental cells were statistically analyzed by one-way analysis of variance followed by Duncan's multiple comparisons procedure.

RESULTS

A human placental cell culture system has been established from normal human term placentas. The monoamine oxidase activity in 8-day-cultured human term placental cells was significantly higher than that of freshly prepared placental cells. Ethanol concentrations at 34.6 and 69.2 mmol/L significantly increased and progesterone concentration at 32 mumol/L significantly decreased the monoamine oxidase activity.

CONCLUSION

These results suggest that the cultured human term placental cells can be used to examine the in vitro effects of ethanol and progesterone on monoamine oxidase activity. However, the physiologic significance of progesterone's inhibitory effect and the stimulatory effect of ethanol monoamine oxidase activity in the in vivo system have yet to be further investigated.

Measurement of human chorionic gonadotrophin (hCG): indications and techniques for the clinical laboratory

The structure of human chorionic gonadotrophin (hCG) is so similar to that of luteinizing hormone (LH) that a variety of assay techniques have been devised to differentiate between these two hormones. The principal indications for measurement of hCG using these methods have not changed greatly over the past decade but the improvements in the sensitivity, specificity and the development of assays for free subunits and metabolic fragments have expanded the use of hCG assays. The review discusses the use of hCG measurement in a routine clinical immunoassay laboratory and emphasizes different requirements for clinical situations.

Effects of fetal sex and dexamethasone on preterm maternal serum concentrations of human chorionic gonadotropin, progesterone, estrone, estradiol, and estriol

The serum human chorionic gonadotropin concentration for the 43 female-bearing gestations was significantly higher (geometric mean 15,603 mIU/ml; 95% confidence interval 12,337 to 19,733) than that for 26 male-bearing pregnancies (geometric mean 8902 mIU/ml; 95% confidence interval 6288 to 12,596), p = 0.0087. The mean gestational age was 32 +/- 2.4 weeks (mean +/- SD). There was no significant difference between male- and female-bearing pregnancies for progesterone, cortisol, estrone, estradiol, estriol, or gestational age. In 19 placebo-treated pregnancies and 14 dexamethasone-treated pregnancies with a mean gestational age of 31.5 +/- 2.7 weeks, there was no significant change from the baseline value observed for either maternal serum human chorionic gonadotropin level or maternal serum progesterone level at 42 hours after institution of treatment. In the dexamethasone-treated subjects the geometric mean was reduced to 20% of baseline for cortisol; 42% of baseline for estrone; 30% of baseline for estradiol; and 41% of baseline for estriol (all p less than 0.001).

The First Bagshawe lecture. Towards generating cytotoxic agents at cancer sites

Several years of experience have now accumulated in the targeting of anti-cancer agents so that we can take stock, identify problems and look for ways round them. Three major obstacles seem to limit present approaches. These are heterogeneity in the distribution of target molecules within the cancer cell population, the pharmacokinetic characteristics of macromolecules and host antibody response to foreign protein. An approach which we have been investigating uses antibodies or other vectors to carry enzymes which have no close human homologue to tumour sites. After clearing residual enzyme activity from the blood by one of several possible techniques, a relatively non-toxic prodrug is given. This prodrug is a substrate for the tumour located enzyme which results in the generation of a highly toxic molecule able to penetrate the tumour mass and cross cell membranes. Genetic engineering methods now offer the prospect of human immunoglobulins with tumour binding and catalytic sites having the potential to minimise host response. Whether this can be achieved depends on having antibodies with adequate specificity and our ability to develop enzyme-prodrug systems with the required characteristics. Early results encourage us to think progress can be made in this direction.

The effects of various hormones on human chorionic gonadotropin production in early and late placental explant cultures

Although human chorionic gonadotropin production peaks in early pregnancy, little is known of the factors regulating it at this time. We have compared human chorionic gonadotropin output in placental explants of 6 to 12 and 37 to 40 weeks' gestational age after addition of hormones on days 4 and 5 of 8 days of culture. Human chorionic gonadotropin production was sevenfold greater in early versus late cultures. In early cultures human chorionic gonadotropin output was increased threefold to fourfold by progesterone, dehydroepiandrosterone, and cortisol whereas late cultures responded only to progesterone and dehydroepiandrosterone. The output of combinations of steroids was additive or better (up to fifteenfold). Gonadotropin-releasing hormone increased human chorionic gonadotropin output only slightly (onefold to twofold) while testosterone was inhibitory (early) or ineffective (late). Estradiol had no effect. These studies demonstrate that explants of early placental tissue provide a useful model for study of human chorionic gonadotropin production, that there are many similarities but some clear differences between early and late secretion, and that steroids exert significant effects on human chorionic gonadotropin production of placental cultures.

Effect of estradiol and progesterone on human chorionic gonadotropin secretion in vitro

Many of the substances known to control the secretion of pituitary gonadotropins also modulate the secretion of human chorionic gonadotropin (hCG) by the placenta. In order to study the effect of estrogens and progestins on hCG secretion, term placental explants were cultured in culture media for 144 hours. During the culture period, hCG secretion increased after 48 hours, and a fortyfold increase was observed after 144 hours (p less than 0.001). Compared to concentrations of hCG in control cultures, secretion of hCG was markedly suppressed in the presence of progesterone 2.25 X 10(-5)M (p less than 0.001), a concentration similar to that found in term placental tissue (1.7 +/- 0.2 micrograms/gm of tissue). Suppression of hCG by progesterone occurred in a dose-response manner (r = -0.9100, p less than 0.01). Estradiol, an important steroid modulator of pituitary gonadotropins, did not significantly suppress the secretion of hCG, except in pharmacologic concentrations (10(-4)M), and physiologic concentrations of estradiol had no effect on the suppression of hCG by progesterone. These results suggest that the mechanism by which progesterone suppresses the secretion of hCG differs from the manner in which steroids modulate the secretion of pituitary gonadotropins.

The measurement of glucocorticoid receptors in human placental cytosol

Cytosol preparations of human term placenta in Tris-HCl buffer containing dithiothreitol were incubated with [3H]dexamethasone at 4 degrees C. Under these conditions the specific binding of [3H]dexamethasone was low when compared with cytosol preparations of sheep fetal lung or ovine placenta. The inclusion of sodium molybdate in the homogenization buffer and the removal of endogenous steroids by treating the cytosol with charcoal before incubation led to a faster and increased uptake of [3H]dexamethasone by human placenta. Scatchard plot analysis of the data showed that the placenta possesses a single class of high-affinity (Kd = 13 +/- 2 nM) low-capacity (193 +/- 34 fmol/mg protein) binding sites for [3H]dexamethasone. The binding of [3H]dexamethasone was reversible and was not due to plasma contamination. The specificity of the binding sites was confirmed by competition experiments in which the highest displacement of [3H]dexamethasone from the binding sites was caused by natural and synthetic corticosteroids. These findings indicate that the human placenta at term contains specific glucocorticoid receptors in high concentrations.