Ectopic production of the isolated beta subunit of human chorionic gonadotropin

Human chorionic gonadotropin in cancer

Human chorionic gonadotropin (hCG) is mainly used for detection and monitoring of pregnancy and pregnancy-related disorders but it is also an extremely sensitive and specific marker for trophoblastic tumors of placental and germ cell origin. Thus treatment of relapsing choriocarcinomas and testicular germ cell tumors is often initiated on the basis of rising hCG levels even in the absence of clinical or histological evidence of a relapse. While these tumors mostly produce the intact heterodimeric hormone consisting of an alpha (hCGalpha), and a beta subunit (hCGbeta), many nontrophoblastic tumors produce only hCGbeta This is usually a sign of aggressive disease and elevated serum levels of hCGbeta are strongly associated with poor prognosis. Elevated serum levels are observed in 45-60% of patients with biliary and pancreatic cancer and in 10-30% of most other cancers. Methods that detect hCG and hCGbeta together are mainly used for measurement of hCG-like immunoreactivity in serum. However, the reference range for hCG is 5-8 fold higher than that for hCGbeta and thus moderately elevated levels can be identified only with a specific and sensitive hCGbeta assay.

Mechanism of gonadotropin gene expression. Identification of a novel negative regulatory element at the transcription start site of the glycoprotein hormone alpha-subunit gene

Regulation of the glycoprotein hormone alpha-subunit (GPHalpha) gene has been studied extensively in pituitary and placental cell lines, but little is known of the transcriptional regulators important for its ectopic expression. To investigate the molecular basis for ectopic expression, it was critical to define cis-regulatory elements and their cognate trans-acting factors that modulate promoter activity in epithelial cell types that do not normally express GPH. DNA-mediated transient expression of promoter-reporter constructs was used to identify a novel negative regulatory element located at the GPHalpha gene transcription start site. Truncation or site-directed mutagenesis of this element produced up to a 10-fold increase in promoter activity. Electrophoretic mobility shift analysis detected a protein that binds specifically to a DNA motif encompassing the cap site. Based on competitive DNA binding studies with mutated oligonucleotides, it was determined that bases from -5 to -2 and +4 to +11 are critical for protein binding. The DNA sequence flanking the transcription start site from -9 to +11 is an imperfect palindrome; consequently, this motif is referred to as the cap site diad element (CSDE) and the cognate factor as the cap site-binding protein (CSBP). CSBP activity was present at different levels in nuclear extracts prepared from a variety of cell types. Significantly, the ratio of activities exhibited by the GPHalpha promoter with a mutated CSDE compared with the promoter with a wild-type CSDE was dependent on the transfected cell line and its content of CSBP. These results indicate that a negative regulatory element centered at the GPHalpha gene cap site and its cognate DNA-binding protein make a significant contribution to the production of alpha-subunit in a variety of tumor tissues. A detailed understanding of this cis/trans pair may further suggest a mechanism to explain, at least in part, how this gene becomes activated in nonendocrine tumors.

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.

Method dependence of interpretation of immunoassay results

The interpretation of results obtained by immunoassays is affected by many different factors and especially by assay sensitivity and specificity. The introduction of sandwich-type immunometric assays using highly sensitive non-radioactive labels and monoclonal antibodies has greatly improved sensitivity while reducing assay time and simplifying performance. Thus determination of subnormal levels of several hormones has become possible. This approach has also enabled more exact tuning of specificity but at the same time it has introduced the risk of too high selectivity. Hapten assays have also become simpler to perform, but in this case no substantial improvement in assay sensitivity has been achieved.

Enhancement by theophylline of the butyrate-mediated induction of choriogonadotropin alpha-subunit in HeLa cells. I. Lack of correlation with cAMP

The glycoprotein hormone common alpha-subunit can be induced in HeLa and other nontrophoblastic tumor cell lines by sodium butyrate. This report demonstrates that production of alpha-subunit can be further modulated by theophylline, especially in conjunction with butyrate. This synergism was not observed with other phosphodiesterase inhibitors such as xanthine, caffeine, theobromine, or methylisobutylxanthine. Induction by a combination of the short chain fatty acid plus the methylxanthine results from a decrease in the lag time after effector addition as well as a change in the rate of subunit accumulation. The increase in alpha-subunit is correlated with an increase in the levels of alpha-subunit mRNA, suggesting that induction is manifest at a pretranslational stage. The production of alpha-subunit was only marginally affected in cultures treated with 8-Br-cAMP or forskolin. Intracellular levels of cAMP were increased approximately threefold by methylisobutylxanthine, twofold by theophylline, fourfold by forskolin, and about 50% by butyrate, yet significant induction was achieved only by butyrate and theophylline. Taken together, these data suggest that the synergism between butyrate and theophylline is not mediated by cAMP.

Expression of beta human chorionic gonadotrophin by non-trophoblastic non-endocrine 'normal' and malignant epithelial cells

Expression of hCG and its free subunits by non-trophoblastic tumours is well recognised. Previously we reported hCG secretion by normal and malignant bladder epithelial cells in vitro. Here we examined culture medium from 83 different cell lines derived mainly from common epithelial tumours. Thirty-two of the cell lines were found to secrete hCG-like material into their culture media. Partial immunochemical characterisation showed that of these only choriocarcinoma and fetal tissue cell lines produced intact hCG and alpha subunit. The remaining 28 hCG-expressing epithelial cell lines, which are of mucosal origin, only secreted free beta subunit. Expression of free beta hCG by non-trophoblastic nonendocrine cells would appear to be especially characteristic of mucosal epithelia from the genitourinary and oral/respiratory tracts. Furthermore, this phenomenon may be characteristic of epithelium with transitional and/or squamous cell-like properties.

Chorionic gonadotropin synthesis by human tumor cell lines: examination of subunit accumulation, steady-state levels of mRNA, and gene structure

A number of tumor cell lines have been examined that differentially produce human chorionic gonadotropin and the isolated alpha- or beta-subunits. It has been demonstrated that all of the cell lines studied to date contain genes for both alpha- and beta-subunits, indicating that differential and exclusive expression of one subunit is not the result of a particular cell line having lost the gene for the alternate subunit as a consequence of chromosome changes accompanying cell transformation. Because many of these established cell lines are aneuploid, it is also significant that no evidence was found for gene amplification in cell lines producing alpha-subunit at very high levels compared to those with very low level expression. Analysis of restriction endonuclease digests of tumor cell DNAs has demonstrated identical patterns for beta-subunit in KpnI digests and KpnI/HindIII double digests. Polymorphisms were observed for alpha-subunit in EcoRI and HindIII digests, but these did not correspond with expression of the alpha-subunit. Significant levels of either mRNA (as determined by dot blot and Northern transfer hybridization analysis) were accompanied by corresponding elevated levels of alpha- and beta-subunits (as determined by radioimmunoassay), suggesting that regulation of subunit production most likely occurs at a pretranslational stage. However, there were apparent differences in the relative ratio of alpha- and beta-subunits and their cognate mRNAs among the cell lines.

Urinary gonadotropin fragment (UGF) measurements in the diagnosis and management of ovarian cancer

UGF is a small peptide present in the urines and tissues of patients with gynecologic cancers. Published research (which, at present, mainly comes from our laboratory) on the general application of UGF as a tumor marker, and on its use in the diagnosis of ovarian cancer, is reviewed, and new studies on its use, alone and with CA125, in the management of patients with ovarian cancer, are presented. In 234 healthy women, 89 with benign disease, and 79 with ovarian cancer, UGF levels were above 3 fmol/ml (low cut-off) in 12 percent, 7 percent, and 82 percent, respectively, and above 8 fmol/ml (high cut-off) in 1.7 percent, less than 1.1 percent, and 59 percent, respectively. Similarly, 11 percent, 14 percent, and 70 percent, respectively, had CA125 levels above 35 U/ml (low cut-off), and less than 1.9 percent, 1.2 percent, and 49 percent had levels above a 200 U/ml (high cut-off). Ideally, the higher UGF and CA125 cut-offs should be used for diagnostic applications, like differentiation of a benign from a malignant pelvic mass (false-positive rate: UGF, less than 1.1 percent; CA125, 1.2 percent), but raising the cut-offs diminishes sensitivities for malignancy (UGF, 59 percent; CA125, 49 percent). The populations detected by the two markers only partially overlap, however, so that, together, UGF or CA125 can identify 75 percent of malignant pelvic masses. Levels of UGF (cut-off, greater than 3 fmol/ml) and CA125 (35 U/ml) were also monitored in 30 women undergoing therapy for ovarian cancer. Clinical observations were reflected at each clinic visit by UGF alone in 67 percent, by CA125 alone in 57 percent, and by UGF and CA125 together in 87 percent of cases. While separately UGF and CA125 levels predicted 71 percent and 57 percent, together they forecast 86 percent of recurrent cancers prior to clinical manifestations. UGF and CA125 should be used together in the detection and management of ovarian cancers.

Modulation of glycoprotein hormone alpha-subunit levels, alkaline phosphatase activity, and DNA replication by antimetabolites in HeLa cultures

Synthesis of the glycoprotein hormone common alpha-subunit and alkaline phosphatase (placental isozyme) has been examined in HeLa S3 cells. A variety of compounds that inhibit DNA synthesis lead to the increased production of both proteins. Experiments presented in this communication were undertaken to determine whether protein induction and DNA synthesis inhibition are coordinated. In general, nucleoside analogs and compounds that alter deoxynucleotide metabolism were good inducers of these ectopic products, whereas agents that altered DNA by intercalation, crosslinking, and covalent modification were poor inducers. The former class of effectors includes 5-bromo-2'-deoxyuridine, 5-fluoro-2'-deoxyuridine, 2'-deoxythymidine, 1-beta-D-arabinofuranosylcytosine, methotrexate, hydroxyurea, N-phosphonoacetyl-L-aspartic acid, and sodium butyrate; and the latter class of compounds includes ethidium bromide, acridine, bleomycin, mitomycin C, cesalin, macromomycin, and cis-diamminedichloroplatinum(II). A direct correlation between protein induction and DNA synthesis inhibition is unlikely based on the following observations: (i) for some effectors, the concentrations required to induce alpha-subunit and PAP were significantly different from those necessary to inhibit DNA synthesis; (ii) several agents inhibit DNA replication but do not enhance hormone or enzyme production; (iii) the kinetics of ectopic protein induction were similar for a number of inducers whereas the kinetics of DNA synthesis inhibition elicited by the same compounds were quite different. It is difficult from the data obtained, however, to rule out the possibility that inhibition of DNA synthesis may be required but is not sufficient for protein induction.

In vitro secretion of human chorionic gonadotrophin by bladder tumour cells

Human chorionic gonadotrophin (hCG) and alphafetoprotein (AFP) were measured in culture media from a panel of 29 cell lines including 9 bladder carcinomas, 5 'normal' bladder epithelia, 10 germ cell tumours, and 5 miscellaneous tumours and 'normal' cell lines. In 7 of the 9 bladder carcinomas and 4 of the 5 'normal' bladder epithelia, the media contained hCG at levels ranging from between 34 and 3,600 IU l(-1). All other cell lines, including the 10 germ cell tumour lines gave negative results for hCG. These findings indicate that in vitro secretion of hCG is a common feature of normal and neoplastic bladder transitional epithelia, and support the hypothesis that parts of the genito-urinary epithelium have a potential for hCG production.

Human chorionic gonadotropin in the rectosigmoid colon. Immunohistochemical study on unbalanced distribution of subunits

For investigation of cellular localization of subunits of human chorionic gonadotropin (hCG) in normal and neoplastic rectosigmoid colon, immunohistochemical studies were performed on nonneoplastic colons (10 fetuses, 3 infants, and 23 adults, including 4 cases of ulcerative colitis) and 7 carcinoid tumors, 19 adenomas, and 50 carcinomas of the rectosigmoid colon. The alpha-hCG immunoreactive cells were present in endocrinelike cells of non-neoplastic glands (6 fetuses older than 14th gestational week, 3 infants and 19 of 23 adults). Many of the positive cells were argyrophilic, and all were nonimmunoreactive for beta subunits of glycoprotein hormones. alpha-hCG immunoreactivity was also present in many argyrophilic cells of all carcinoid tumors and in some of the endocrine cell micronests. The immunoreactive cells for isolated beta-hCG were found in 14 infiltrating carcinomas. The distribution of hCG subunits was unbalanced, and both subunits may be expressed through an independent mechanism, commonly in normal and neoplastic rectosigmoid colon.

Human chorionic gonadotropin in gastric carcinoma. An immunohistochemical study suggesting independent regulation of subunits

To investigate the production of human chorionic gonadotropin (hCG) in gastric carcinoma, 124 gastric carcinomas and a choriocarcinoma with adenocarcinoma were examined immunohistochemically, using anti-hCG alpha and beta antibodies. In choriocarcinoma, many trophoblastic cells were synchronously positive for both subunits. In contrast, the distribution of hCG-subunits in gastric carcinoma was unbalanced with hCG alpha in 39 and hCG beta in 63 cases. 26 cases contained alpha and beta positive cells, whereas synchronous cells were extremely rare in four cases. Incidences of hCG-subunit-positivities were not different between early and advanced carcinomas. HCG alpha-positive cells appeared endocrine-like in papillotubular carcinomas and some positive cells were argyrophilic in serial sections in 23 of 39 cases. HCG beta-positive cells were much more frequent in deranged glands, especially of microtubular-mucocellular carcinomas and most were not argyrophilic. In surrounding non-neoplastic mucosa, hCG alpha-positive cells were more numerous with endocrine-like configurations, but hCG beta-positive cells were rarely present in deranged glands. Although subunit-profile of hCG in gastric carcinomas was different from that of normal, the difference may be quantitative: hCG-subunits may be expressed through an independent mechanism but commonly in gastric mucosa and carcinoma. These results are also discussed in relation to trophoblastic tumours arising in non-trophoblastic tissues.

Phosphorylation of the glycoprotein hormone alpha-subunit secreted by human tumor cell lines

The synthesis of ectopic proteins by tumors is thought to result from derepression of normally silent genes. One approach to a better understanding of this phenomenon is to characterize the physicochemical properties of the ectopic products, comparing them to their normal counterparts. In the following communication, evidence will be presented to indicate that the glycoprotein hormone alpha-subunits secreted by a number of human tumor cell lines are phosphorylated. This novel covalent modification occurs in cell lines derived from both trophoblastic (JAR, JEG) and nontrophoblastic (HeLa, ChaGo) tumors. A choriocarcinoma cell line (JAR), which secretes both hCG-alpha and hCG-beta, phosphorylates only the alpha-subunit.

Pretranslational regulation of ectopic hCG alpha production in ChaGo lung cancer cells by sodium butyrate

Ectopic production of hCG and its free alpha subunit by ChaGo lung cancer cells is stimulated by sodium butyrate. To investigate pretranslational regulation in this system, we examined the response of the hCG alpha and beta subunit mRNAs in ChaGo-K1 cells, a clone that produces free hCG alpha but no hCG or hCG beta in the basal state. When a Northern blot of total RNA from ChaGo cells was hybridized to a [32P]- labeled hCG alpha cDNA probe, a single band was detected that was identical in size (approximately 850 bases) to placental hCG alpha mRNA. RNA from butyrate-stimulated (5 mM, 24 h) ChaGo cells contained 7.7 times as much hCG alpha mRNA as RNA from control ChaGo cells. This increase appeared to be relatively selective since no difference in total polyA-containing mRNA levels was detected between butyrate-treated and control cells by [32P]oligo(dT) hybridization. In addition, no hCG beta mRNA was detected when Northern and dot blots were hybridized to an hCG beta cDNA probe. In a time course experiment, hCG alpha mRNA accumulation in butyrate-treated cells increased significantly by 8 h with a maximum increase of 6.1-fold at 24 h compared to control values. Major differences in immunoactive hCG alpha accumulation were not apparent, however, until after 24 h. These studies show that stimulation of ChaGo hCG alpha production by butyrate can be completely accounted for by pretranslational events and that failure to detect hCG or free hCG beta production by these cells is not due to poorly translatable RNA or post-translational protein degradation. Thus, exclusive ectopic production of only one of the hCG subunits is likely to be due to selective genomic expression.

Human chorionic gonadotropin and human placental lactogen in extragonadal tumors. An immunoperoxidase study of ten non-germ cell neoplasms

The immunoperoxidase localization of the alpha and beta subunits of human chorionic gonadotropin (hCG) and of human placental lactogen (hPL) was studied in ten extragonadal nontrophoblastic tumors associated with raised serum levels of one or more of these placental proteins. Three of the tumors were bronchial carcinomas, one was a gastric carcinoma, two were malignant carcinoids (one bronchial and one gastric), two were pancreatic islet cell carcinomas, and two were metastatic carcinomas with an unknown primary site. The maximum alpha subunit serum level was 33,000 ng/ml (gastric carcinoid), the maximum hCG/hCG-beta level was 705,000 ng/ml, and the maximum hPL level was 50 ng/ml (both in the gastric carcinoma). An indirect immunoperoxidase technique and rabbit polyclonal affinity-purified antibodies and peroxidase conjugates were used on formalin-fixed, paraffin-embedded sections. Five blocks (eight cases) or six blocks (two cases) from various sites were obtained from each patient at surgery and/or autopsy. Positive stains for hCG/hCG-beta were seen in six of seven tumors (25/37 blocks) with raised levels, for the alpha subunit in nine of nine tumors (30/47 blocks), and for hPL in two of five tumors (4/26 blocks). Only a relatively minor number of the cells were positive, and within the same case, there was considerable site-to-site variation in the number of positive cells. Large bizarre cells contained hCG/hCG-beta as well as the alpha subunit, if it was demonstrated in the same tumor as the beta subunit. Otherwise, the alpha subunit was found in small unremarkable cells. Giant cells that were smaller than those positive for hCG/hCG-beta contained in hPL. In some serial sections, hCG-alpha, hCG/hCG-beta, and hPL were segregated in different cell populations, supporting the concepts of their separate genetic control.

Tumor markers: value and limitations in the management of cancer patients

Sixteen tumor markers are reviewed, and measured to the ideal: produced by the tumor cell alone absent in health and in benign disease present in all patients with a given malignancy level in the blood representative of tumor mass detectable in occult disease. The only marker that approaches the ideal is human chorionic gonadotropin (HCG) in gestational trophoblastic tumors. In this malignancy, the HCG level suggests the diagnosis and stage, confirms response to therapy, and predicts relapse. The three most widely used and intensely studied tumor markers are carcinoembryonic antigen (CEA), alphafetoprotein (AFP), and HCG. CEA cannot be used in screening for cancer, but in carcinoma of the colon its elevation preoperatively increases the likelihood of advanced disease and postoperative recurrence. Postoperatively, elevated titers are often but not invariably associated with recurrent disease. AFP and HCG are useful in the management of nonseminomatous germ cell testicular tumors. Like CEA, they cannot be used for screening. They are more likely to be increased with advancing stage, and after therapy rising levels almost always mean recurrent disease. Some markers are valuable in specific circumstances, such as calcitonin in screening for familial medullary carcinoma of the thyroid. In multiple myeloma, immunoglobulins are useful in determining the tumor mass and response to therapy. In neuroblastoma, catecholamine metabolites are useful primarily in making the diagnosis. In some malignancies, the absence of effective therapy lowers the value of the marker, as for AFP in hepatoma. The remaining markers are too unreliable or too little studied to be useful in the management of an individual patient with cancer. The purpose of this paper is to provide the clinician with an understanding of the limitations of the present tumor markers that will lead to wiser use of the tests, and to provide standards to which future tumor markers should be measured.

Isolated ectopic production of the free beta subunit of chorionic gonadotropin by an epidermoid carcinoma of unknown primary site

Metastatic choriocarcinoma was suspected in a 39-year-old woman who presented 7 months postpartum with fatigue, pelvic pain, a massive pleural effusion, and a positive urine pregnancy test. Subsequent evaluation resulted in discovery of the isolated production of the free beta-subunit of chorionic gonadotropin (CG-beta) by a widespread, poorly differentiated epidermoid carcinoma. Chemotherapy was ineffective, the woman died, and at autopsy the primary site of the tumor could not be determined. The patient's serum (185 ng/ml) and a tumor metastasis (720 ng/g) contained large amounts of immunoactive material that diluted in parallel to CG-beta standard, but neither chorionic gonadotropin (CG), its alpha subunit, nor other placental proteins were detected. A monoclonal antibody that recognizes free CG-beta, but not intact CG, was instrumental in implicating an ectopic source of the CG-beta before a tissue diagnosis was obtained. When the patient's serum was chromatographed on a dextran gel, the CG-beta immunoactivity eluted in a position of higher apparent molecular weight than either standard CG or CG-beta, suggesting that this neoplasm secreted an altered molecular form of the CG-beta subunit.

The effect of protein and RNA synthesis inhibitors on the synthesis and secretion of hCG, alpha- and beta-hCG subunits, in organ culture

The relationship between the rate of RNA and protein synthesis and that of and its alpha- and beta-subunits was studied in an organ culture system using RNA and protein synthesis inhibitors. It was found that inhibiting protein synthesis by puromycin or cycloheximide results also in a nearly complete inhibition of the synthesis and/or processing of RNA molecules. Protein synthesis was found to be dependent upon continuous poly A(-) RNA synthesis. The intracellular content of hCG, alpha-hCG and beta-hCG remains constant during the entire incubation period and does not change in response to any of the inhibitors used. However, in the presence of some inhibitors, changes are observed in the amount of the secreted hormone and its two subunits as well as in the association ability of the subunits to form the complete native hormone. Nevertheless, synthesis and secretion of hCG, alpha-hCG and beta-hCG were almost identically affected by alpha-amanitin. These results might suggest that the mRNAs coding for the two subunits have the same relative metabolic stability and/or that these mRNAs are mobilized molecules from free cytoplasmic mRNP pools. The specific alpha- and beta-mRNAs seem to be less stable, however, than the mRNAs coding for the other newly synthesized proteins, since the inhibition of alpha- and beta-hCG synthesis by alpha-amanitin was consistently higher than the corresponding average inhibition of total protein synthesis.

Pseudohypergonadotropinemia and pseudohyperprolactinemia induced by heterophilic antibodies?

The serum of 20 apparently hypergonadotropic and/or hyperprolactinemic patients (14 females, 6 males, ages 13-75 years) without evidence of neoplasia or pituitary adenomas was found to contain a large amount of molecular material (MW ca. 100,000) resulting in factitiously elevated levels of peptide hormones when measured by double-antibody radioimmunoassay with a long second incubation time. The interference by this material with the test system could be avoided by using polyethylene glycol (PEG) for the separation of free from bound antigen, or by preincubation of the samples with normal rabbit serum. No definite disease process can as yet be linked to these findings. They rather seem to be caused by the presence of heterophilic antibodies in serum, as the serum of approximately one half of the patients was found to give a positive Paul-Bunnell test. Moreover, the beta hCG activity in the urine of these patients was low, probably as a result of the low clearance of substances with igh MW. It is therefore suggested to apply to following diagnostic measures before clinical consequences are being considered in a case of hypergonadotropinemia and/or hyperprolactinemia without pertinent clinical findings: (1) validation of the immunoassay, (2) preincubation of the samples with serum from other species, (3) the use of another separation procedure than the double-antibody method, and (4) measurement of the respective hormone in urine.

Butyrate regulates glycosylation of the glycoprotein hormone alpha subunit secreted by "glucose-starved" human liver cells

The alpha-subunit secreted by Chang human liver cells was labeled in vitro with [35S]Met, [3H]GlcN, or [3H]Fuc, and the biosynthetic products were studied by SDS-PAGE. Cells labeled with [35S]Met secreted a homogeneous 23K-24K alpha. In contrast, alpha secreted from cells labeled with [3H]GlcN and [3H]Fuc in the absence of glucose ("glucose-starved") was heterogeneous. This size heterogeneity was altered by glucose and by butyrate, but was little affected by dibutyryl adenosine 3', 5'-monophosphate. In the presence of 0.56 mM (10 mg/dl) or 5.6 mM (100 mg/dl) glucose, or 2 mM butyrate, primarily the larger and presumably more highly glycosylated 24K-25K alpha was secreted. Moreover, the effect of 2 mM butyrate on the alpha secreted by "glucose-starved" cells was qualitatively and quantitatively similar to the effect of 0.56 mM glucose in the absence of butyrate. Likewise, 2 mM butyrate + 0.56 mM glucose was nearly equivalent to 5.6 mM glucose alone. These results demonstrate a novel effect of butyrate on glycoprotein biosynthesis; it is the only agent, reported thus far, which has the same effects as Glc or Man on protein glycosylation in "glucose-starved" cells.

Human chorionic gonadotropin and alpha chain of glycoprotein hormones in patients with inflammatory bowel disease

In twenty patients with Crohn's disease and ten patients with ulcerative colitis serum levels of human chorionic gonadotropin and the common alpha-subunit of glycoprotein hormones were determined by radioimmunoassay. In contrast to published data, all serum samples except one revealed levels within the normal range of 148 controls (human chorionic gonadotropin levels up to 3.9 IU/l, alpha-subunit up to 3.8 micrograms/l). Neither the serum levels of human chorionic gonadotropin nor of the alpha-subunit differed significantly between patients with Crohn's disease (median/maximum: 0.9/4.4 IU/l; 0.7/3.6 micrograms/l) and ulcerative colitis (1.0/3.4 IU/l; 0.8/2.2 micrograms/l). Furthermore, the serum levels studied in patients with active (0.9/3.0 IU/l; 0.7/3.5 micrograms/l) and inactive (0.9/4.4 IU/l; 0.8/3.6 micrograms/l) Crohn's disease and in patients with active (1.1/3.4 IU/l; 0.9/2.2 micrograms/l) and inactive (0.9/2.9 IU/l; 0.8/1.3 micrograms/l) ulcerative colitis were not significantly different. There was no relationship of the duration of the disease or a bowel resection to the serum levels of human chorionic gonadotropin or the alpha-subunit. It is concluded that both parameters are not useful as markers in patients with Crohn's disease or ulcerative colitis. The normal serum levels found in patients with inflammatory bowel diseases indicate human chorionic gonadotropin as a highly specific marker for malignant diseases.

Qualitative and quantitative analyses of human chorionic gonadotropin and its subunits produced by malignant tumors

Human chorionic gonadotropin (hCG) and its subunits in plasma, urine, ascites, and tumor extracts from four patients with hCG-producing tumors (undifferentiated cell carcinoma and choriocarcinoma of the bladder, malignant teratoma of the retroperitoneum, and pancreatic carcinoma) were measured by the radioimmunoassays specific to each component. While both free alpha and beta subunits as well as the whole molecule of hCG were found in all these samples, the proportion of beta subunit was much higher in these tumor extracts than in the placental extracts. Since the alpha and beta subunits are known to be translated from separate mRNAs, such increase of subunit is probably due to the predominant increase of mRNA encoding beta subunit of hCG in the hCG-producing tumors. Gel filtration of the extracts of these four tumors on Sephadex G-100 and G-150 columns demonstrated a heterogeneity of hCG, alpha, and beta subunits in these tumor extracts, and the elution profiles of plasma, urine and tumor extracts were slightly different. Lower molecular weight forms of hCG and its beta subunit were present in all urine samples. The significance of these heterogeneities remains to be elucidated.

Predominance of gonadotropin alpha-subunit resulting from preferential loss of hCG beta production in an established cell line

The BeWo line of trophoblastic cells, maintained in continuous culture since 1966, was employed to investigate the phenomenon of gonadotropin alpha-subunit predominance that exists in several cell lines. The secretion of complete human chorionic gonadotropin (hCG) relative to alpha-subunit was compared in several different BeWo sublines, all of where were derived from BeWo stock roller tube colonies. In all of the BeWo sublines, secretion of hCG originally exceeded secretion of alpha-subunit. With time in culture, however, there was a marked decline in production of hCG/hCG beta, but not in alpha-subunit. Thus it appears that the production of hCG beta by BeWo choriocarcinoma cells is more labile than the production of the alpha-subunit.

Ectopic hormone syndromes

Ectopic hormone production is not always associated with endocrine manifestations and if extensive studies of tumour hormones are made it is found that asymptomatic hormone production is often concomitant with neoplasms. The nature of tumour hormones seems essentially indistinguishable from that of native hormones, although there exists in some cases an abundance of precursor or hormone fragments and unbalanced biosynthesis of subunits. Production of multiple hormones by a tumour is not uncommon. These facts may suggest abnormal gene expression as the basic mechanism responsible for ectopic hormone production. During the process of cellular differentiation, most of the genes are inactivated. Neoplastic transformation may activate repressed genes, thus producing hormones that are not produced by differentiated cells (derepression hypothesis). This hypothesis, however, makes it difficult to explain the higher incidence of ACTH-LPH-producing tumours among APUD tumours. Some investigators have postulated that only APUD tumours elaborate ACTH-LPH or other APUD hormones (neuro-endocrine cell hypothesis). However, there have been reported some definite non-APUD tumours which elaborate ACTH-LPH. These facts can be explained by the stepwise, irreversible repression hypothesis of cellular differentiation. In APUD cells, the gene for ACTH-LPH coding may be repressed at the terminal stage of differentiation and may, therefore, be very easily derepressed by neoplastic transformation. On the other hand, the ACTH-LPH gene may be repressed at a relatively early stage in non-APUD cells and be difficult to reactivate even after neoplastic transformation. Further studies on ectopic hormone producing tumours may clarify the mechanism of ectopic hormone production and yield new insights into the fundamental process of malignant change.

Circulating choriogonadotropin beta subunit in a patient with primary amenorrhea and embryonal ovarian carcinoma

A 20-year-old patient, phenotypically female, genotypically male, who had previously sought medical attention for primary amenorrhea, developed an embryonal carcinoma in the right gonad. Selective formation of the beta subunit of choriogonadotropin was demonstrated by positive test results on native serum and after gel filtration with a classical "beta-HCG" assay and a specific assay for the beta subunit, but negative results with a specific assay for choriogonadotropin. The concentrations of placental lactogen, alpha-fetoprotein and choriogonadotropin alpha subunit were normal. This case illustrates the necessity for early diagnosis of primary ovarian insufficiency in cases of primary amenorrhea. The results indicate that, for the detection of certain neoplastic disorders, the lower specificity of the choriogonadotropin assay introduced in 1972 by Vaitukaitis and coworkers [25]--reacting equally well with choriogonadotropin and with free beta subunit--may have advantages over the more specific assays for choriogonadotropin and for the beta subunit described by Franchimont et al. [8,28,29]. The availability of the latter assays, however, facilitates the identification of the immunoreactive material found with the former assay. The ambiguity of the present nomenclature for "beta-HCG" assay is pointed out.

Ectopic production of human chorionic gonadotropin (hCG) by neoplasms: the value of measurements of immunoreactive hCG in the urine as a screening procedure

Immunoreactive human Chorionic Gonadotropin (hCG) was measured in serum and urine extracts from patients with malignant disease using a radioimmunoassay that detects efficiently hCG and its betasubunit. Of the 70 patients examined, 12 (17.1%) were positive for hCG in serum and 31 44.3%) in urine. Eleven patients who were positive in serum were also positive in urine; 20 patients (28.6%) were positive only in urine. Sephadex G-100 chromatography of urine from two serum-negative and urine-positive patients showed that the hCG immunoreactive material in the urine of these patients was mostly a molecular species smaller than hCG and hCG-beta. The nature of this molecule(s) is unknown and is called here metabolite(s) "X" of hCG-beta. The urine of 2 patients who where positive for hCG in both serum and urine contained considerable amount of metabolite(s) "X" as well as the native hCG-beta subunit, which was present also in the serum of these 2 patients. The metabolite(s) "X" was also shown by chromatography in the urine of a pregnant woman. It is concluded that the ectopic production of hCG is found more than twice as frequently in urine as compared to when serum alone is examined. The urine of serum-negative tumor patients can be positive for hCG because of the presence in it of the metabolite(s) "X" of hCG-beta or hCG which presumably circulates in the blood of these patients at non-detectable levels.

Prospective evaluation of some candidate tumor markers in the diagnosis of pancreatic cancer

As part of a prospective diagnostic protocol, patients suspected of having pancreatic cancer had systemic and portal venous blood samples assayed, in coded batches, for peptide hormones and enzymes thought to be of potential value as tumor markers. An average of 111 patients were tested for each candidate marker. Results were analyzed by dividing patients into three groups according to the definitive diagnoses. These were pancreatic cancer (32% of patients), other cancers (27%), and benign diseases (41%). Although elevated mean levels of fasting plasma glucose and serum alkaline phosphatase were found in the pancreatic cancer group, there were no significant differences in the mean levels of any of the candidate markers studied in the three groups. The diagnostic values of normal and elevated levels of each candidate marker studied have been calculated. None has proven to be as useful as the serum level of pancreatic oncofetal antigen, fasting plasma glucose, or serum alkaline phosphatase in the diagnosis or exclusion of pancreatic cancer.

Synthesis and processing of human chorionic gonadotropin subunits in cultured choriocarcinoma cells

Pulse and pulse-chase experiments have identified the presence of partially glycosylated precursors of the alpha and beta subunits of human chorionic gonadotropin (hCG) in cultured JAR choriocarcinoma cells. The alpha subunit precursor has an apparent molecular weight (by sodium dodecyl sulfate/polyacrylamide gel electrophoresis) of 18,000 (compared to 22,000 for fully processed alpha subunit); the beta subunit precursor has an apparent molecular weight of 24,000 (fully processed, 34,000). Both of these precursors appear to have an intracellular half-life of at least 1 hr and to contain the mannose core but not the terminal carbohydrate sequences. Fully processed alpha and beta subunits do not accumulate intracellularly, indicating that further processing of the precursors is followed by rapid secretion.

Human chorionic gonadotropin in the plasma of normal, nonpregnant subjects

To determine whether ectopic secretion of a protein hormone can occur normally, we studied plasma from normal, nonpregnant subjects for the presence of a placental hormone, human chorionic gonadotropin. We extracted and purified this hormone from other plasma proteins. We identified the hormone in the final residue on the basis of its dose-response curves in a specific radioimmunoassay and calculated the plasma concentration after correction for losses. Because this assay is sensitive to concentrations as low as 2 pg per milliliter, human chorionic gonadotropin could be detected in the plasma of 12 of 16 blood donors; the median concentration was 19 pg per milliliter (range, less than 2 to 361). This immunologic human chorionic gonadotropin was further characterized from a pool of normal plasma by gel filtration on Sephadex G-100 and was found to be identical to the standard form of the hormone. The concentration in this pool from 13 normal men was 18 pg per milliliter. The source of this ectopic hormone production is unknown, but may be normal, rapidly proliferating nonmalignant cells.

Identification of separate mRNAs coding for the alpha and beta subunits of thyrotropin

A 9S mRNA, purified from mouse thyrotropic pituitary tumors by sucrose density gradient centrifugation of poly(A)-enriched mRNA, directed the synthesis of only alpha and beta subunits of thyrotropin in the reticulocyte lysate translation system. Analysis of radioiodinated 9S mRNA, repurified by oligo(dT)-cellulose chromatography and sucrose gradient centrifugation, yielded two species of RNA on urea/polyacrylamide gel electrophoresis. The major RNA species contained 620 nucleotides, and the minor RNA species contained 560 nucleotides. Unlabeled 9S mRNA was further purified by urea/polyacrylamide gel electrophoresis; the mRNAs were separately eluted from slices of the gel containing material migrating with an apparent length of 620 and 560 nucleotides. Translation of these mRNAs in the reticulocyte lysate showed that the longer mRNA coded for the alpha subunit and the shorter mRNA coded for the beta subunit of mouse thyrotropin. Because more alpha than beta subunit of thyrotropin was consistently synthesized, unbalanced amounts of thyrotropin subunits appear to be synthesized by translation of unbalanced amounts of individual mRNAs. We have demonstrated that the synthesis of thyrotropin is directed by two separate mRNA molecules, each coding for a different subunit of the hormone.

Human chorionic gonadotropin and malignant mesothelioma

A 56-year-old male presented with ascites and gynecomastia. Laparoscopy demonstrated peritoneal tumors which were biopsied. Conventional histology and electron microscopy revealed the tumor to be a malignant mesothelioma. The ascitic fluid and tumor cell lysate, but not serum, contained hCG by specific assay, and the immunoreactive hCG had characteristics similar to purified hCG in filtration on Sephadex G-100. Malignant mesothelioma is a tumor which may be associated with elevated hCG concentrations. Demonstration of hCG in ascitic fluid should suggest the presence of neoplasm.

mRNA-directed biosynthesis of alpha subunit of thyrotropin: translation in cell-free and whole-cell systems

mRNA from mouse thyrotropic pituitary tumors was translated in frog oocytes (a whole-cell system) and in wheat germ extract and reticulocyte lysate (cell-free systems) in the presence of [(35)S]methionine. Synthesized peptides related to thyrotropin were identified in the three systems by immunoprecipitation with subunit-specific antisera developed against the alpha subunit of ovine lutropin (luteinizing hormone) and the beta subunit of bovine thyrotropin. In wheat germ extract and reticulocyte lysate, a single immunoprecipitable form of the alpha subunit of thyrotropin was synthesized with an apparent molecular weight of 14,000 by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. In the frog oocyte, three forms of immunoprecipitable alpha subunit of thyrotropin were synthesized with apparent molecular weights of 20,000, 14,000, and 10,000. The 20,000 form is similar to unlabeled rat pituitary standard alpha subunit and (35)S-labeled mouse tumor alpha subunit in cell cultures (20,000-21,000); thus, it may represent a precursor-cleaved and glycosylated form. The 14,000 form synthesized in all three systems probably represents the pre-alpha subunit of thyrotropin; the 10,000 form, synthesized only in the frog oocyte, could be a proteolytically cleaved but unglycosylated form. Because only the alpha subunit of thyrotropin was identified and no larger molecular weight immunoprecipitable form of either subunit was detected in any of the translation systems, alpha and beta subunits of thyrotropin appear to be translated from separate mRNAs.