A positive urine pregnancy test (UPT) with adnexal mass; ectopic pregnancy is not the ultimate diagnosis.

A positive urine pregnancy test (UPT) with adnexal mass in ectopic pregnancy is not the ultimate diagnosis. The incidence of ectopic pregnancy is about 27 per 1000 pregnancies [1]. On average, about 6-16% will present to an emergency department with first-trimester bleeding and abdominal pain [2]. On presenting with these symptoms with the simultaneous presence of an adnexal mass and an empty uterus, a UPT is of paramount importance to determine whether the symptoms are pregnancy related or not. When the UPT is positive, an ectopic pregnancy is not the only diagnosis as the rare entity of non-gestational ovarian choriocarcinoma (NGOC) should be considered. Here we present two case reports of NGOC, which were initially diagnosed as ectopic pregnancy. The first case is a 16-year-old girl, with vaginal bleeding and an adnexal mass due to an ovarian choriocarcinoma, She underwent unilateral oophorectomy and received multiple courses of chemotherapy. She is disease free without evidence of recurrence or metastasis after 12 months of follow-up. The second patient is also 16 years old and presented with an acute abdomen. She was diagnosed as a ruptured luteal cyst and underwent partial oophorectomy. When the pathologist diagnosed a choriocarcinoma she received multiple courses of chemotherapy, but thereafter an advanced disease was diagnosed with evidence of distant metastasis.

Secondary brain choriocarcinoma: a case report.

Choriocarcinoma metastasizes widely. One in every ten choriocarcinoma that leaves its primary site, metastasizes to the brain. This 27 years old patient presented with symptoms of space occupying lesion that was confirmed by CT-SCAN. There was no history of vaginal bleeding and amenorrhoea was concealed by unmarried patient. Chest X-ray was normal. Tumor was excised after craniotomy. Histology of tumor was that of secondary choriocarcinoma. Patient responded excellently to chemotherapy and was well one year after. We strongly recommend a high index of suspicion of choriocarcinoma in management of brain tumors. ß-HCG assay should be included in investigation of all patients with intracranial tumors irrespective of sex.

Testicular choriocarcinoma metastatic to skin and multiple organs. Two case reports and review of literature.

Two cases of males with subcutaneous masses as the first clinical sign of testicular choriocarcinoma are reported. The urine and serum human chorionic gonadotropin (hCG) test confirmed high level hCG from male choriocarcinoma. These cases, although very rare, can be a great diagnostic and therapeutic challenge and should be considered in the differential diagnosis of subcutaneous masses occurring in young males.

Use of urine pregnancy test for rapid diagnosis of primary pulmonary choriocarcinoma in a man.

Primary pulmonary choriocarcinoma is an extremely rare tumor in men, with 13 cases reported in the literature. Due to its rarity, primary choriocarcinoma of the lung in men is often incorrectly diagnosed as more common diseases, such as primary or metastatic lung cancer, and therefore potentially curative chemotherapy or surgery may be withheld from the patient. In this report, we present the case of a 23-year-old man with hemoptysis and progressive dyspnea. Airspace consolidation with multiple nodules of varying sizes was found on a chest radiograph. The results of a urine pregnancy test were positive, and the beta-human chorionic gonadotropin level was markedly elevated both in the serum and the urine. Subsequently, testing of a bronchoscopic biopsy specimen proved these tumors to be choriocarcinoma. We conclude that the urine pregnancy test, a simple and convenient method, would be very useful in the rapid diagnosis of primary pulmonary choriocarcinoma in men.

Early pregnancy human chorionic gonadotropin (hCG) isoforms measured by an immunometric assay for choriocarcinoma-like hCG.

Human chorionic gonadotropin (hCG) exhibits molecular heterogeneity in both its protein and carbohydrate moieties. This communication describes changes in hCG isoforms detected directly in clinical samples. These isoforms, quantified in blood or urine specimens, show a progression of change throughout normal pregnancy. Early pregnancy produces a type of hCG that resembles, in terms of immunoreactivity, a major form of hCG excreted in choriocarcinoma. The isoforms predominate for the first 5-6 weeks of gestation and then diminish, being replaced with the hCG isoforms which predominate throughout the remainder of pregnancy. The alteration in hCG isoform content occurs in both blood and urine. The progression of isoforms is best delineated by calculating the change in the ratio of the two forms, as many hCG assays either do not detect or fail to discriminate among these isoforms. An analogous pattern of hCG isoforms was observed in patients with in vitro fertilization pregnancies. hCG isolated from the pituitary displayed binding characteristics similar to those of the hCG derived from normal pregnancy urine. The early pregnancy hCG isoforms appear to have a differential expression in normal pregnancy as opposed to pregnancies which will not carry to term, suggesting that a determination of the relative balance of hCG isoforms may have diagnostic application in predicting pregnancy outcome.

Evaluation of nicked human chorionic gonadotropin content in clinical specimens by a specific immunometric assay.

We report the development and characterization of an IRMA for the direct measurement of nicked human chorionic gonadotropin (hCGn) in blood and urine. hCGn derived from a reference preparation of hCG used as an immunogen elicits monoclonal antibodies (mAbs) with enhanced recognition of human luteinizing hormone epitopes. The most specific assay for pregnancy hCGn is an IRMA composed of one mAb to choriocarcinoma-derived hCGn (C5) and a second mAb developed from immunization with normal-pregnancy hCGn. This assay was used to evaluate hCGn profiles in normal, in vitro fertilization, Down syndrome, and ectopic pregnancies. In all pregnancies, hCGn was usually present in much lower concentrations than the non-nicked hCG isoform. Our results suggest that some form of physical separation from the overwhelming quantities of non-nicked hCG present in clinical specimens will be required before accurate immunochemical estimations of hCGn can be made.

Carbohydrate and peptide structure of the alpha- and beta-subunits of human chorionic gonadotropin from normal and aberrant pregnancy and choriocarcinoma.

Human chorionic gonadotropin (hCG), purified from the urine of 14 individuals with normal pregnancy, diabetic pregnancy, hydatidiform mole, or choriocarcinoma, plus two hCG standard preparations, was examined for concurrent peptide-sequence and asparagine (N)- and serine (O)-linked carbohydrate heterogeneity. Protein-sequence analysis was used to measure amino-terminal heterogeneity and the "nicking" of internal peptide bonds. The use of high-pH anion-exchange chromatography coupled with the increased sensitivity of pulsed amperometric detection (HPAE/PAD) revealed that distinct proportions of both hCG alpha- and beta-subunits from normal and aberrant pregnancy are hyperglycosylated, and that it is the extent of the specific subunit hyperglycosylation that significantly increases in malignant disease. Peptide-bond nicking was restricted to a single linkage (beta 47-48) in normal and diabetic pregnancy, but occurred at two sites in standard preparations, at three sites in hydatidiform mole, and at three sites in choriocarcinoma beta-subunit. In the carbohydrate moiety, alpha-subunit from normal pregnancy hCG contained nonfucosylated, mono- and biantennary N-linked structures (49.3 and 36.7%, means); fucosylated biantennary and triantennary oligosaccharides were also identified (7.3 and 6.9%). In choriocarcinoma alpha-subunit, the level of fucosylated biantennary increased, offset by a parallel decrease in the predominant biantennary structure of normal pregnancy (P < 0.0001). The beta-subunit from normal pregnancy hCG contained fucosylated and nonfucosylated biantennary N-linked structures; however, mono- and triantennary oligosaccharides were also identified (4.6 and 13.7%). For O-linked glycans, in beta-subunit from normal pregnancy, disaccharide-core structure predominated, whereas tetrasaccharide-core structure was also detected (15.6%). A trend was demonstrated in beta-subunit: the proportions of the nonpredominating N- and O-linked oligosaccharides increased stepwise from normal pregnancy to hydatidiform mole to choriocarcinoma. The increases were: for monoantennary oligosaccharide, 4.6 to 6.8 to 11.2%; for triantennary, 13.7 to 26.7 to 51.5% and, for O-linked tetrasaccharide-core structure, 15.6 to 23.0 to 74.8%. For hCG from individual diabetic pregnancy, the principal N-linked structure (34.7%) was consistent with a biantennary oligosaccharide previously reported only in carcinoma; and sialylation of both N- and O-linked antennae was significantly decreased compared to that of normal pregnancy. Taken collectively, the distinctive patterns of subunit-specific, predominant oligosaccharides appear to reflect the steric effect of local protein structure during glycosylation processes. The evidence of alternative or "hyperbranched" glycoforms on both alpha- and beta-subunits, seen at low levels in normal pregnancy and at increased or even predominant levels in malignant disease, suggests alternative substrate accessibility for Golgi processing enzymes, alpha 1,6 fucosyltransferase and N-acetylglucosaminyltransferase IV, in distinct proportions of subunit molecules.

Mass spectrometric characterization of nicked fragments of the beta-subunit of human chorionic gonadotropin.

We describe the use of an HPLC/MS technique for the characterization of nicked fragments of hCG beta-subunit. After reductive alkylation of the nicked hCG beta-subunit with vinylpyridine, endoproteinase Glu-C or trypsin was used to digest the protein to produce peptides that could be analyzed by HPLC/electrospray ionization MS. Human leukocyte elastase digestion was used to produce an experimentally nicked hCG. Two nicking sites were observed, between amino acids 42Thr and 43Arg and between 44Val and 45Leu. The former site has not been previously reported for elastase digestion. The structures of the fragments were confirmed by HPLC/MS after removal of the oligosaccharide by direct mass measurement and by mass determination of their proteolytic digests. Without the glycopeptidase treatment, the microheterogeneity of the two N-linked oligosaccharides could be deduced from the spectra of the proteolytic fragments. Nicking with elastase was found to alter the oligosaccharide structures. Nicked beta-subunit samples isolated from the urine of choriocarcinoma patients were also analyzed and the location of the nicking site(s) agreed with that determined by classical techniques. Important differences in the oligosaccharide structures were also observed in these samples, including the presence of triantennary oligosaccharides not found in hCG from healthy subjects. These findings demonstrate the potential of HPLC/MS for characterization of glycoprotein standard preparations.

[Fragments of human chorionic gonadotropin (hCG): diagnosis of pregnancy and tumors]. / Fragmente des humanen Choriongonadotropins (hCG): Schwangerschafts- und Tumordiagnostik.

The pregnancy and tumor marker human chorionic gonadotropin (hCG) belongs to the family of the glycoprotein hormones. Information on epitope forming sequences of hCG and its subunits hCG alpha and hcg beta has significant impact on the examination of intra- and extracellular metabolism and the standardization of diagnostic assay systems. Variants of hCG appear in biological fluids with variable modifications on different parts of the molecule. These changes may influence the binding patterns of monoclonal antibodies (MCA), thereby causing erroneous results in hCG immunoassays. The aim of the present work was to investigate the influence of peptide bond cleavages and the loss of certain segments of the molecule, which were induced by proteases on the expression of the seven hCG alpha-(alpha 1-alpha 7), nine hCG beta- (beta 1-beta 9) and four hCG beta-core-fragment-epitopes (beta 10-beta 13), previously identified by us [1-10]. To this end, we digested hCG alpha and hCG beta with chymotrypsin. Hormone fragments were separated by high performance liquid chromatography (HPLC) and subsequently immunochemically examined by direct binding radioimmunoassay (DB-RIA), competitive RIA and immunoenzymometric assays (IEMA). Fractions containing hCG-like immunoreactivity were sequenced by Edman and carboxypeptidase-Y degradation. It appeared that: (I) Amino acids (AA) alpha 41-47 and the peptide bonds between AA alpha 40/41, alpha 47/48 and alpha 29/30 do not influence the expression of the 7 alpha-epitopes, (II) The absence of the hCG beta N-terminus plays a crucial role for the formation of epitopes beta 10 and beta 13. (III) Neither the presence nor the absence of the C-terminal peptide of hCG beta (hCG beta CTP, AA beta 114-145) has any importance for the expression of epitopes beta 1-beta 7 and beta 10-beta 13 (IV).(ABSTRACT TRUNCATED AT 250 WORDS)

[Urinary gonadotropin fragment measurement in the monitoring of trophoblastic disease].

Urinary gonadotropin fragment (UGF) is a small peptide which is present in the urine of pregnant women and of women with trophoblastic diseases as well as with certain nontrophoblastic malignancies. 275 samples each of urine and blood from 46 patients with trophoblastic diseases were taken for UGF and hCG measurements and compared. 24 samples from 12 healthy, nonpregnant women were taken as control. Cut-off values of UGF and hCG used for measuring the sensitivity of trophoblastic diseases were respectively > 0.2 microgram/L and above 20 micrograms/L. It was found that 64.0% of the urine samples gave UGF values > 0.2 microgram/L and 66.5% of the blood samples showed hCG levels above 20 micrograms/L (P > 0.1). No false-positive rate was observed in the control group. However, among patients who were found to have low or negative hCG values, 57.6% showed positive UGF levels. These findings suggest that in patients with positive levels of both UGF and hCG, the UGF measurement may not be necessary. But for patients with low or negative blood hCG values, certain percentage of urine UGF could still be detected.

The heterogeneity of human chorionic gonadotropin (hCG). I. Characterization of peptide heterogeneity in 13 individual preparations of hCG.

Peptide variations in the alpha-subunit (molecules starting at alpha 3 and alpha 4) and beta-subunit (missing linkages at beta 44-45 and beta 47-48) of hCG have been reported by several investigators. Studies, however, have been limited to standard hCG preparations (purified from large pools of urine) and other hCG samples from mixed urines. In this study we used chromatographic procedures to purify the total hCG content of 13 individual urines, 6 from patients with pregnancy and 7 from those with trophoblast disease (no hCG-containing fractions were excluded). Then, we examined for the first time the peptide variability among individual samples of hCG. We report 1) that individual hCG preparations have nicks (missing linkages) in the beta-subunit, primarily between residue 47-48 (11 of 13 samples) and, less commonly, at the linkage 44-45 or 46-47 (3 of 13 samples); 2) the extent of nicking varies greatly between individual preparations (range, 0-100% of molecules); 3) varying alpha-subunit N-terminal heterogeneity (N-terminus starting at alpha 3 or alpha 4) was also present (range, 0-28% of molecules), but was confined to preparations from individuals with trophoblast disease (6 of 7 samples from trophoblast disease urine, 0 of 6 from pregnancy urine); 4) hCG missing the beta-subunit C-terminal region was also detected (2 of 13 hCG preparations); and 5) 1 of 13 preparations was nicked on the hCG alpha-subunit, between residues 70 and 71. Thus, 12 of 13 individual hCG samples demonstrated at least 1 of 4 different forms of peptide heterogeneity. We conclude that individual hCG samples vary widely in the type and extent of peptide heterogeneity, an observation that is not appreciated when pools of hCG are studied.

The heterogeneity of human chorionic gonadotropin (hCG). III. The occurrence and biological and immunological activities of nicked hCG.

Nicks, or missing peptide linkages, have been found in hCG beta-subunit between residues 44 and 45 and between residues 47 and 48. We examined the occurrence and biological and immunological activities of nicked hCG. As shown by sequence analysis, CR127 standard hCG is approximately 20% nicked, half at beta 44-45 and half at beta 47-48. Treatment with human leukocyte elastase increased the extent of nicking of CR127 standard hCG. The longer the incubation of CR127 standard with human leukocyte elastase (0, 2, and 21 h), the greater the extent of nicked hCG (20%, 46%, and 89%). As the extent of nicking increased, the receptor-binding ability diminished, as did the ability to stimulate progesterone production by rat corpus luteal cells in vitro (0.9, 0.74, and 0.29 microgram/microgram hCG, respectively). In a regression analysis, a linear relationship was indicated between the extent of nicking and receptor binding values (97% correlation) and between the extent of nicking and steroidogenic activity in vitro (99% correlation). From the intercepts of the regression lines, it was estimated that nicks reduced receptor binding by 11-fold and reduced the steroidogenic activity of hCG by 5-fold. We examined eight individual hCG preparations, three purified from pregnancy urine, three from urine from patients with hydatidiform mole, and two from urine from women with choriocarcinoma. In descending order, the eight individual hCG preparations were 100%, 100%, 85%, 76%, 42%, 41%, 0%, and 0% intact. Although no correlation was observed between the percent intact and the ability of the eight individual samples to displace 50% [125I]hCG in binding CG/LH receptor (r less than 0.5), a close correlation was noted between the percent intact and the steroidogenic activity in vitro (98% correlation). This separated the effects of nicking on receptor binding and steroidogenic activities and indicated that while multiple factors influence receptor binding, only nicking suppresses the steroidogenic activity of bound hCG. We examined the recognition of nicked hCG molecules by different hCG immunoassays. The Hybritech Tandem assay measured total hCG and did not distinguish nicked and intact hCG molecules (in a regression analysis, immunoactivity vs. percent intact hCG, r less than 0.5). In contrast, the immunometric assay using B109 hCG dimer-specific monoclonal antibody and anti-beta-peroxidase only detected the intact component of hCG (in a regression analysis, immunoreactivity vs. percent intact hCG, 98% correlation). We used these assays together to estimate the percentage of intact hCG and to deduce the extent of nicking.(ABSTRACT TRUNCATED AT 400 WORDS)

Urinary excretion of degradation products of prostacyclin and thromboxane is increased in patients with gestational choriocarcinoma.

Gestational choriocarcinoma metastasizes rapidly, in which process the vasoactive prostanoids may be significant. We therefore compared the urinary excretion of prostacyclin and thromboxane A2 (TxA2) metabolites in 19 women with gestational choriocarcinoma and 20 healthy age-matched women by assessing spot urine samples for 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and 2,3-dinor-6-keto-prostaglandin F1 alpha (2,3-dinor-6-keto-PGF1 alpha) (degradation products of prostacyclin) as well as for thromboxane B2 (TxB2) and 2,3-dinor-TxB2 (degradation products of TxA2) by high-pressure liquid chromatography, followed by radioimmunoassay; the data were related to urinary creatinine concentration. The urinary output of 6-keto-PGF1 alpha [29.56 +/- 7.0 versus 25.08 +/- 3.91 ng/mmol creatinine (SE)] in patients with choriocarcinoma was normal, but that of 2,3-dinor-6-keto-PGF1 alpha in cancer patients was higher than in controls (24.44 +/- 5.20 versus 14.84 +/- 1.94, P less than 0.02), as was that of TxB2 (22.72 +/- 4.69 versus 9.69 +/- 1.52, P less than 0.001) and 2,3-dinor-TxB2 (114.21 +/- 30.81 versus 51.81 +/- 10.40, P less than 0.01). The ratio of net prostacyclin output (6-keto-PGF1 alpha plus 2,3-dinor-6-keto-PGF1 alpha) to the net TxA2 output (TxB2 plus 2,3-dinor-TxB2) in cancer patients [0.52 +/- 0.1 (SE)] was lower (P less than 0.03) than in the controls (0.83 +/- 0.1), and in an inverse relation (r = -0.54, P less than 0.05) to the scoring index of poor prognosis for the disease. We conclude that the prostanoid excess in gestational trophoblastic disease, as evidenced for the first time in this study, may originate from choriocarcinoma cells, or may be a paraneoplastic phenomenon, and we conclude also that TxA2 excess may contribute to the tumor growth and/or formation of metastases.

Altered glycosylation of human chorionic gonadotropin decreases its hormonal activity as determined by cyclic-adenosine 3',5'-monophosphate production in MA-10 cells.

Human chorionic gonadotropin (hCG) purified from pooled urine of normal pregnant women contains four asparagine-linked sugar chains and four mucin-type sugar chains. The structures of asparagine-linked sugar chains of this hormone are constant and site-specific. hCGs obtained from the urine of patients with invasive mole or choriocarcinoma have quite different sets of oligosaccharides although the primary structures of the polypeptides and the numbers of the sugar chains are the same as those of normal hCG. In order to examine the biological activities of these hCGs with altered glycosylation, we measured the amount of cAMP produced in a murine Leydig tumour cell line, MA-10, after incubation with the hCG samples. The extent of sialylation of oligosaccharides in the three hCG samples used in this study were 88% in normal hCG, 82% in invasive mole hCG and 63% in choriocarcinoma hCG. The hormonal activity of invasive mole hCG was slightly lower while that of choriocarcinoma hCG was significantly (P less than 0.01) lower than that of normal hCG. Complete desialylation induced remarkable loss of full activities in all the samples. However, the hormonal activities of the three samples were different even after desialylation. The full activities of the desialylated samples of invasive mole hCG and choriocarcinoma hCG were 78 and 65% of that of desialylated normal hCG. These results indicated that the structures of the neutral oligosaccharide portion are also important for the expression of full hormonal activity.

Occurrence of fragmentation of free and combined forms of the beta-subunit of human chorionic gonadotropin.

In an attempt to further study various fragments of free and combined forms of hCG beta present in biological fluids, we performed one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by Western immunoblotting using antipeptide antibodies directed to the hCG beta-(111-116) portion (monoclonal antibody FB12) antiserum to the hCG beta(8-16) portion or antiserum which was specific for fragments ending at residue 47. Results observed in a crude preparation of urinary hCG demonstrated that in addition to the carboxyl-terminal part of the reduced hCG beta nicked subunit (beta NS) [hCG beta-(48-145)], three other fragments of mol wt 18,000 (F1), 16,500 (F2), and 12,000 (F3) were detectable after cleavage of disulfide bonds. Both the immunoreactivity pattern and peptide sequencing revealed that the F1 fragment was constituted of the hCG beta-(1-47) sequence, whereas the F2 fragment comprised the 6-47 portion. We then studied the beta NS in urine from either pregnant women or four patients with choriocarcinomas. Results showed that both hCG and the free beta-subunit contained beta NS. Furthermore, free hCG beta present in those urine samples appeared to be extensively, if not totally, nicked. Results observed in urine were confirmed using separation of hCG from its beta-subunit by a two-step chromatography procedure, identification of hCG and hCG beta immunoreactive peaks by specific monoclonal immunoradiometric assay, and analysis of resulting preparations by one-dimensional electrophoresis under reducing conditions, followed by Western immunoblotting with FB12. This latter protocol was also used to investigate the presence of beta NS in sera of four patients with choriocarcinoma tumors. In those sera, hCG appeared to be nicked. This study demonstrates that the beta-subunit of hCG is modified by multiple fragmentations.

Characterization of a small immunoreactive HCG-like component isolated from urine of a patient with choriocarcinoma.

An immunoreactive hCG-like substance with low molecular weight was isolated from the urine of a patient with choriocarcinoma and its characteristic properties were studied. The urinary hCG preparation was fractionated by gel filtration on a Sephadex G75 column and each fraction was assayed for hCG activities by an enzyme linked immunosorbent assay using a monoclonal antibody to hCG (Mab-5D4). Two immunoreactive hCG peaks were obtained. One was coeluted with ordinary hCG and the other was eluted after hCG-alpha. After refractionation on the same column, the hCG peak (Ag-2) with low molecular weight was radioiodinated with 125INA and applied to an immunoaffinity column bound Mab-5D4 for further purification. The purified 125I-labelled Ag-2 showed a high binding activity to a conventional rabbit anti-hCG serum and Mab-5D4. This Mab had binding specificity to hCG, hCG-beta and LH but not to hCG-alpha. However, this fraction did not bind to Mab-6E4 which possessed binding activities only to hCG, hCG-alpha and LH, nor to Mab-2F8 which was specific only to hCG. Autoradiography after SDS-Page of the immune precipitate which was made by 125I-labelled Ag-2 and Mab-5D4, revealed that the Ag-2 had a molecular weight of approximately 14,000 daltons. Lectin (LeH) affinity chromatography of the urinary hCG specimen from the same patient revealed that it contained two kinds of immunoreactive hCG. One did not bind to LeH column but the other did. A small immunoreactive molecule (Ag-2) was detected in the LeH-unbound fraction but not in the LeH-bound fraction. These results suggest that choriocarcinoma patients excrete in the urine a small LeH-unbound immunoreactive component which contains an antigen epitope common to hCG, hCG-beta and LH.

Fragmentation of the beta-subunit of human chorionic gonadotropin produced by choriocarcinoma.

When human chorionic gonadotropin (hCG) was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions with dithiothreitol (DTT), a smaller weight material (CTP'), in addition to the beta-subunit, could be detected by Western blot analysis using antiserum for hCG beta-carboxy-terminal peptide (CTP). The CTP' band was much more apparent with urinary hCG from a patient with choriocarcinoma than with that from normal pregnant women. Second-dimensional electrophoresis of the choriocarcinoma hCG (c-hCG) after reduction with DTT indicated that the CTP', Mr 25,000, was released from the beta-subunit. The carbohydrate structure of the CTP' was analyzed by affinity with lectin-peroxidase on a nitrocellulose membrane. The CTP' did not interact with Concanavalin A, but exhibited strong interaction with both RCA120 and Arachis hypogaea after removal of sialic acid, indicating that it was released as a fragment containing an O-linked sugar chain as was found in the hCG beta carboxy-terminal portion. Western blot analysis using the antisera for hCG alpha, hCG beta, and hCG beta-CTP showed that the CTP' contains not only the carboxy-terminal portion but also a part of the internal (core) portion of the beta-subunit molecule. This dissociation of the c-hCG beta was further supported by the presence of a faster moving component (FMC) which may correspond to the NH2-terminal side counterpart. The desialylated FMC could be detected by Concanavalin A and RCA120 but not by Arachis hypogaea, indicating that it contains N-linked rather than O-linked sugar chains. The FMC does not contain any of the epitopes for the antisera examined in Western blot. These results indicate that the beta-subunit of the choriocarcinoma urine hCG has an unusual site which is dissociated into two components of Mr 25,000 (CTP') and Mr 18,000 (FMC) by DTT reduction.