Molecular forms of human chorionic gonadotropin in choriocarcinoma serum and urine

Cytotrophoblast stem cell lines derived from human embryonic stem cells and their capacity to mimic invasive implantation events

BACKGROUND

An effective embryonic-maternal interaction is crucial for successful human pregnancy. Failure of this process is a major cause of infertility and can lead to placental dysfunction resulting in recurrent miscarriage, fetal retardation and pre-eclampsia. Research is severely constrained by ethical and practical considerations; therefore, we aimed to generate cytotrophoblast stem (CTBS) cell lines from human embryonic stem cells (HESCs).

METHOD

Beta-HCG was used as a marker of viable trophoblast cells. In defined culture, embryoid bodies were generated from HESCs and selected for trophoblast enrichment by rounds of cellular aggregation and disaggregation. Distinct CTBS cell lines were isolated and characterized. Spheroid cytotrophoblast bodies were generated and their interaction with luteal-phase endometrial stroma was analysed by real-time image analysis.

RESULTS

Three CTBS cell lines were derived, which were maintained in the absence of residual HESCs, fibroblast feeder cells or extracellular matrix. CTBS cells displayed typical cytotrophoblast and syncytiotrophoblast characteristics and exhibited further differentiation to invasive endovascular cell phenotype. One cell line was generated with constitutive expression of enhanced green fluorescent protein (eGFP). Spheroid trophoblast bodies mimicked closely the early invasive stages of implantation when incubated with human endometrial stromal preparations in vitro.

CONCLUSION

These human CTBS cell lines are a significant new model for investigating human placentation and may have considerable potential in cell therapy applications.

Specific Measurement of O-Linked Core 2 Sugar-Containing Isoforms of Hyperglycosylated Human Chorionic Gonadotropin by Antibody B152

There have been a significant number of reports on the clinical utility of measurement of 'hyperglycosylated' isoforms of the pregnancy hormone, human chorionic gonadotropin (hCG). Although there are a variety of hCG isoforms which can be termed 'hyperglycosylated', the measurements were all made using a unique antibody designated B152. This antibody was raised using a choriocarcinoma-derived form of hCG, which was hyperglycosylated with N- and O-glycans and was also 100% 'nicked' hCG. Antibody B152 was recently mapped to a linear epitope around a single O-glycan on the beta-subunit of hCG at residue number 132. Thus, the antibody can only measure isoforms of hCG that possess a core 2 type of branched O-glycan on this portion of the hCG beta-subunit. Isoforms that are hyperglycosylated in the hCG alpha-subunit or only on the N-glycans of hCGbeta will not be recognized by antibody B152. Apparently, measurements of these core 2 hCG isoforms have important clinical application in early pregnancy during which they are the predominant isoform of hCG until the 6th week of gestation. The secretory pattern of these isoforms can be used to predict the health status of the pregnancy in fertility clinics. Moreover, the measurements of these core 2 hCG isoforms are more useful than standard hCG for the prediction of Down syndrome pregnancies. The core 2 isoforms are also of important use in cancer diagnosis and monitoring since their concentration appears to correlate with malignancy.

Detection of circulating breast cancer cells by reverse transcriptase polymerase chain reaction (RT-PCR)

The confounding problem in treatment of breast cancer is the metastasis of breast tumour. Reverse transcriptase polymerase chain reaction (RT-PCR) has been recently used in the detection of circulating breast cancer cells. This review reports on the development of this assay as well as its advantages and disadvantages. We feel that cytokeratin 20 and beta -human chorionic gonadotropin (hCG) mRNA are the best markers for the detection of circulating breast cancer cells. We suggest that the multiple RNA marker RT-PCR assay can help to increase both sensitivity and specificity of detection, and that quantitative RT-PCR assay is more effective than the qualitative assay in the detection of circulating breast cancer cells.

Human villous macrophage-conditioned media enhance human trophoblast growth and differentiation in vitro

In human chorionic villi, numerous macrophages, so-called Hofbauer cells, are located adjacent to trophoblasts. To determine the role of the macrophages in the proliferation and differentiation of trophoblasts, cytotrophoblast cells were cultured in serum-free culture-conditioned media of villous macrophages (VMCM), peritoneal macrophages (PMCM), and villous fibroblasts (VFCM). In VMCM, proliferation of cytotrophoblast cells was detected at 24 h by immunocytochemistry with Ki-67-antibody. A large number (P < 0.001) of multinucleated syncytia was formed in VMCM. In VMCM, cytotrophoblast cell fusion was completed by 96 h, which coincided with the peak of hCG secretion and initiation of human placental lactogen (hPL) release. Levels of hCG (P < 0.001) and hPL (P < 0. 001) secretion from syncytial cells were significantly higher in VMCM than in PMCM or in VFCM. Concentrations of macrophage colony-stimulating factor (M-CSF) and vascular endothelial growth factor (VEGF) analyzed by ELISA were greater in VMCM than in PMCM or in VFCM, whereas monocyte chemoattractant protein-1 (MCP-1) concentration was high in PMCM. The expression patterns of M-CSF, VEGF, and MCP-1 in villous macrophages and peritoneal macrophages by reverse transcriptase-polymerase chain reaction were similar to their secretion patterns. Thus, villous macrophages have a greater ability to stimulate hCG and hPL secretion than do peritoneal macrophages. This study suggests that macrophages within the villous stroma may stimulate the growth and differentiation of trophoblasts through their secreted substances.

The molar vesicle fluid contains the beta-core fragment of human chorionic gonadotropin

The human chorionic gonadotropin (hCG) beta-core fragment (beta-CF) is a major molecular form of hCG beta subunit (hCGbeta) immunoreactivity in the urine of pregnant women and patients with trophoblastic disease. The majority of evidence supports the fact that the beta-CF is a degradative product of intact hCG and free hCGbeta in the kidneys. We found a beta-CF-like substance in the fluid of molar vesicles from a patient with complete hydatidiform mole. The molar fluid beta-CF (mbeta-CF) was indistinguishable from the beta-CF in the patient's urine (ubeta-CF) by immunoreactivity and by elution profile on gel chromatography. The binding study to lectins, however, showed that mbeta-CF contains a carbohydrate moiety that differs from that of ubeta-CF. Immunohistochemistry with anti-beta-CF antibody demonstrated a strong immunoreactivity in a large number of macrophages in the molar villous stroma. In vitro incubation of intact hCG with peritoneal macrophages showed a slow increase of intact hCG in the cell cytosol with the appearance of beta-CF-like substance in the cell supernatant. In conclusion, the source of beta-CF in molar fluid is likely to be macrophages existing in the villous stroma. Thus macrophages may ingest intact hCG and act as a local regulator of gonadotropic hormones.

Human chorionic gonadotropin beta-core fragment is present in the human placenta

The presence of hCG beta-core fragment (beta-core) in the human placenta has been controversial. To clarify its presence in the villous tissue, first, we developed an enzyme immunoassay which is highly specific for beta-core. Then, we investigated the presence of beta-core immunoreactivity in the supernatants of placental organ culture and those of primary culture of trophoblasts as well as in the placental extracts at different stages of gestation. The immunoreactivity of beta-core was demonstrated in each sample, and the amount was at least 5% of intact hCG immunoreactivity. Immunohistochemical analysis of the placental tissue showed localization of beta-core immunoreactivity to the syncytiotrophoblast. Western blot analysis of the supernatants of organ culture as well as urine samples of pregnant women showed two major bands with molecular weight of approximately 15000. On the other hand, beta-core immunoreactivity in the pregnant sera ranged from 0.1 to 0.19% of intact hCG immunoreactivity. These results suggest the presence and possible secretion of beta-core fragment in the human placenta, and its immunoreactivity in the serum is likely to be reduced due to its short half life in the maternal blood.

Expression of alpha and beta genes of human chorionic gonadotropin in lung cancer

To confirm the ectopic production of human chorionic gonadotropin (hCG) in lung cancer, we attempted to detect the presence of mRNA transcripts of the alpha and beta genes for hCG in lung cancer tissues obtained from surgical operations. Although we were able to show the presence of hCG beta mRNA transcripts in lung cancer tissue by Northern blot, the sensitivity of the assay was too low for a precise analysis of hCG beta mRNA transcripts in most lung cancers. Using reverse transcription PCR (RT-PCR) and Southern blot analysis, however, various amounts of mRNA transcripts of hCG beta genes 3, 5, 7 and 8 were demonstrated in 9 of the 14 lung cancer tissues examined, while no mRNA transcripts were detectable in 12 normal lung tissues from the same patients. Our results are consistent with a clear difference in serum and urinary hCG beta levels observed between normal subjects and lung cancer patients. The expression of the hCG alpha gene, however, was detected in normal lung tissues more frequently than in lung cancer tissues using RT-PCR Southern blot. Our results strongly suggest the production of hCG beta as being part of the phenotype of malignantly transformed lung cells and further strengthen its superior specificity over intact hCG or hCG alpha as a tumor marker for lung cancers.

Metabolism of hCG and hLH to multiple urinary forms

Human chorionic gonadotropin (hCG) is synthesized primarily in the placenta while human luteinizing hormone (hLH) is produced in the pituitary. Both hormones are highly homologous in structure and both appear to be altered to analogous molecular forms as the hormones are proteolytically processed, or metabolized, from tissue of origin, through the circulation, and finally to the urine. Placental hCG is excreted into urine as heterodimeric hormone, heterodimeric nicked hCG, free subunits (some nicked), and predominantly as the hCG beta core fragment. A pituitary form of heterodimeric hCG, which is partly sulfated as is pituitary hLH, was recently isolated and is likely the form of hCG observed in the urine of healthy postmenopausal women and nonpregnant premenopausal women as well. A pituitary form of the hLH beta core fragment, highly analogous in structure to that of urinary hCG beta core fragment, has been used to develop specific monoclonal antibody assays to measure urinary hLH beta core fragment which is excreted at significantly higher molar concentrations than is hLH in the urine of ovulating women 1 or 2 days after the LH surge. This fragment of LH appears in the urine of postmenopausal women as well. The development of the capability to distinguish the hCG beta core fragment from the hLH beta core fragment in urine may have useful applications in tumor marker assays, pregnancy tests, and menopause. While hCG urinary assays have been widely employed, urinary assays for hCG and hLH metabolites are much less used since the urinary molecular forms are only partly known. Our studies of hCG and hLH urinary metabolites are directed towards improvement of the utility of urinary measurements of molecules derived from these hormones. Since many of the molecular forms of these two hormones in urine differ from their forms in blood, it may be necessary to produce new immunoassays as well as novel urinary reference preparations to accurately measure these molecules within their urinary matrix.

[Significance of serum beta-hCG as a tumor marker for stomach carcinoma]

INTRODUCTION

Recent investigations indicate that in 50% of patients with gastric cancer, beta-hCG-positive cells can be found in the tumour by immunohistochemical investigations. The objective of this study was to investigate how often beta-hCG-immunoreactive gastric carcinomas were accompanied by an elevation in serum beta-hCG, that could have been used as a course control variable.

METHODS

In 54 patients with gastric carcinoma a monoclonal antibody directed against beta-hCG was used for immunohistochemical marking in the APAAP system. The evaluation was graded positive or negative. In parallel, serum beta-hCG was determined preoperatively using an enzyme immunoassay (MEIA). Tumour stage, grading and tumour localization were determinants in the evaluation.

RESULTS

We found that 41% (22 of 54) of the carcinomas induced a positive immunohistochemical response to beta-hCG, regardless of their location in the stomach. In relation to tumour stage, a positive beta-hCG immunoreactivity was apparent in 27% (6/22) of tumours without lymph node or distant metastases (T1-4N0M0), in 54% (7/13) of tumours with lymph node and without distant metastases (T1-4N > or = 1M0) and in 47% (9/35) of tumours with distant metastases. Poorly differentiated tumours (G3-4) were positive in 42% (15/36) and well-differentiated tumors (G1-2) in 39% (7/18) of cases. In only 1 patient was the beta-hCG level in serum elevated, however.

CONCLUSIONS

beta-hCG-Positive gastric carcinomas are found more frequently in advanced tumour stages and poorly differentiated carcinomas. These carcinomas, however, seem not to excrete beta-hCG in sufficient amounts to produce measurable serum values. Therefore, beta-hCG cannot be used a prognostic factor or for course control. The relevance of beta-hCG expression of tumour cells to the patients' prognosis remains obscure.

Combination assay of urinary beta-core fragment of human chorionic gonadotropin with serum tumor markers in gynecologic cancers

Ectopic production of the immunoreactive beta-subunit of human chorionic gonadotropin (IR-hCG beta) by gynecologic malignancies has been well recognized, but IR-hCG beta has not yet been established as a clinically useful tumor marker, except for germ cell tumors. We measured the concentrations of IR-hCG beta-related molecules, intact hCG, free hCG beta, and beta-CF, in the sera and urine of patients with various gynecologic cancers (cervical, endometrial, and ovarian cancers) to assess their clinical usefulness as a tumor marker in comparison with serum tumor markers such as CEA, SCC, CA125, and CA19-9. The highest incidence of IR-hCG beta was obtained in the assay for beta-CF in the urine, with positive rates of 47.7% (94 of 197) for cervical, 37.8% (14 of 37) for endometrial, and 84.4% (38 of 45) for ovarian cancers with a cut-off value of 0.2 ng/mg of creatinine. In cervical cancer, there was no significant correlation between the concentrations of urinary beta-CF and serum SCC, and 57.9% (114 of 197) of the patients were detected by the combination assay of these tumor markers. Serial determination in 22 cervical cancer patients with elevated urinary beta-CF level prior to therapy showed that its level decreased after successful treatment, but 4 of 5 patients with persistent or recurrent disease had elevated levels of urinary beta-CF. All of the ovarian cancer patients examined were detected by the combination assay of urinary beta-CF and serum CA125. The levels of urinary beta-CF showed little correlation with those of the serum tumor markers, indicating the usefulness of the combination assay of urinary beta-CF with serum tumor markers for detecting cervical and ovarian cancers.

Assessment of urinary beta-core fragment of human chorionic gonadotropin as a new tumor marker of lung cancer

BACKGROUND

Some patients with lung cancer have been found to have elevated levels of serum immunoreactive human chorionic gonadotropin (hCG)/hCG beta (IR-beta), but it is uncertain whether it would be valuable as a tumor marker. Recently, IR-beta has been demonstrated to consist of at least three different molecules, intact hCG, free hCG beta, and hCG beta-core fragment (beta-CF), in body fluids. In this study, the authors qualitatively analyzed IR-beta in the serum and urine of patients with lung cancer and assessed its clinical usefulness as a tumor marker.

METHODS

Highly sensitive and specific enzyme immunoassays were established to measure intact hCG, free hCG beta, and beta-CF in the serum and urine of patients with lung cancer.

RESULTS

Of 99 patients with lung cancer, almost half of the patients achieved positive values of IR-beta in the urine, although only 12 had elevated values of IR-beta in the serum. The greater part of the elevated urinary IR-beta was identified to be beta-CF by gel chromatography on Sephadex G-100 (Pharmacia LKB Biotechnology, Tokyo, Japan), leading the authors to assess its usefulness as a tumor marker for lung cancer. Based on the cutoff value (0.2 ng/mg of creatinine) from healthy subjects, the overall positive rate of urinary beta-CF for lung cancer was 48.5% (48 of 99 patients). The incidence of the marker increased with stage of disease, from 35.7% (15 of 42) in Stage I and 35.7% (5 of 14) in Stage II to 62.5% (20 of 32) in Stage III and 72.7% (8 of 11) in Stage IV. These positive rates exceeded or equaled those of the serum tumor markers, carcinoembryonic antigen, and squamous cell carcinoma (SCC)-related antigen, measured simultaneously in the same patients. The author were encouraged that there was no significant difference in the positive rates of urinary beta-CF between two major types of lung cancer: adenocarcinoma (49.2%) and SCC (45.2%). Immunohistochemical study revealed positive staining of IR-beta in the cancer tissues from 5 of 12 patients with elevated levels of IR-beta, in which most of the positive cases had the elevated levels of serum free hCG beta (> 0.5 ng/ml) and/or urinary beta-CF (> 1.0 ng/mg of creatinine).

CONCLUSIONS

Ectopic production of IR-beta by lung cancer is not rare, and urinary beta-CF might be a potential tumor marker of lung cancer.