Understanding the mechanisms leading to failure in metallic nanowire-based transparent heaters, and solution for stability enhancement.

Silver nanowire (AgNW) networks are emerging as one of the most promising alternatives to indium tin oxide (ITO) for transparent electrodes in flexible electronic devices. They can be used in a variety of optoelectronic applications such as solar cells, touch panels and organic light-emitting diodes. Recently they have also proven to be very efficient when used as transparent heaters (THs). In addition to the study of AgNW networks acting as THs in regular use, i.e. at low voltage and moderate temperature, their stability and physical behavior at higher voltages and for longer durations should be studied in view of their integration into real devices. The properties of AgNW networks deposited by spray coating on glass or flexible transparent substrates are thoroughly studied via in situ measurements. The AgNW networks' behavior at different voltages for different durations and under different atmospheric conditions, both in air and under vacuum, has been examined. At low voltage, a reversible electrical response is observed while irreversibility and even failure are observed at higher voltages. In order to gain a deeper insight into the behavior of AgNW networks used as THs, simple but realistic physical models are proposed and are found to be in fair agreement with the experimental data. Finally, as the stability of AgNW networks is a key issue, we demonstrate that coating AgNW networks with a very thin layer of TiO2 using atomic layer deposition (ALD) improves the material's resistance against electrical and thermal instabilities without altering optical transmittance. We show that the critical annealing temperature associated to network breakdown increases from 270 °C for the as-deposited AgNW networks to 420 °C for AgNW networks coated with TiO2. Similarly, the electrical failure which occurs at 7 V for the as-deposited networks increases to 13 V for TiO2-coated networks. TiO2 is also proved to stabilize AgNW networks during long duration operation and at high voltage. Temperature higher than 235 °C was achieved at 7 V without failure.

Bridge percolation: electrical connectivity of discontinued conducting slabs by metallic nanowires.

The properties of nanostructured networks of conductive materials have been extensively studied under the lens of percolation theory. In this work, we introduce a novel type of local percolation phenomenon used to investigate the conduction properties of a new hybrid material that combines sparse metallic nanowire networks and fractured conducting thin films on flexible substrates. This original concept could potentially lead to the design of a novel composite transparent conducting material. Using a complementary approach including formal analytical derivations, Monte Carlo simulations and electrical circuit representation for the modelling of bridged-percolating nanowire networks, we unveil the key relations between linear crack density, nanowire length and network areal mass density that ensure electrical percolation through the hybrid. The proposed theoretical model provides key insights into the conduction mechanism associated with the original concept of bridge percolation in random nanowire networks.

A short-term colorectal cancer sphere culture as a relevant tool for human cancer biology investigation.

BACKGROUND: Ex vivo colospheres have been previously characterised as a colorectal cancer (CRC) well-rounded multicellular model, exclusively formed by carcinoma cells, and derived from fresh CRC tissue after mechanical dissociation. The ability to form colospheres was correlated with tumour aggressiveness. Their three-dimensional conformation prompted us to further investigate their potential interest as a preclinical cancer tool. METHODS: Patient-derived CRC xenografts were used to produce numerous colospheres. Mechanism of formation was elucidated by confocal microscopy. Expression analysis of a panel of 64 selected cancer-related genes by real-time qRT-PCR and hierarchical clustering allowed comparison of colospheres with parent xenografts. In vitro and in vivo assays were performed for migration and chemosensitivity studies. RESULTS: Colospheres, formed by tissue remodelling and compaction, remained viable several weeks in floating conditions, escaping anoikis through their strong cell-cell interactions. Colospheres matched the gene expression profile of the parent xenograft tissue. Colosphere-forming cells migrated in collagen I matrix and metastasised when subrenally implanted in nude mice. Besides, the colosphere responses to 5-fluorouracil and irinotecan, two standard drugs in CRC, reproduced those of the in vivo original xenografts. CONCLUSION: Colospheres closely mimic biological characteristics of in vivo CRC tumours. Consequently, they would be relevant ex vivo CRC models.

Film-thickness-dependent conduction in ordered Si quantum dot arrays.

In recent years, silicon nanostructures have been investigated extensively for their potential use in photonic and photovoltaic applications. So far, for silicon quantum dots embedded in SiO(2), control over inter-dot distance and size has only been observed in multiple bilayer stacks of silicon-rich oxides and silicon dioxide. In this work, for the first time the fabrication of spatially well-ordered Si quantum dots (QDs) in SiO(2) is demonstrated, without using the multilayer approach. This ordered formation, confirmed with TEM micrographs, depends on the thickness of the initially deposited sub-stoichiometric silicon oxide film. Grazing incidence x-ray diffraction confirms the crystallinity of the 5 nm QDs while photoluminescence shows augmented bandgap values. Low-temperature current-voltage measurements demonstrate film thickness and order-dependent conduction mechanisms, showing the transition from temperature-dependent conduction in randomly placed dots to temperature-independent tunnelling for geometrically ordered nanocrystals. Contrary to expectations from dielectric materials, significant conduction and photocarrier generation have been observed in our Si QDs embedded in SiO(2) demonstrating the possibility of forming initial film-thickness-controlled conductive films. This conduction via the silicon quantum dots in thick single layers is a promising result for integration into photovoltaic devices.

Dendritic cells directly trigger NK cell functions: cross-talk relevant in innate anti-tumor immune responses in vivo.

Cytotoxic T lymphocytes and natural killer cells are essential effectors of anti-tumor immune responses in vivo. Dendritic cells (DC) 'prime' tumor antigen-specific cytotoxic T lymphocytes; thus, we investigated whether DC might also trigger the innate, NK cell-mediated anti-tumor immunity. In mice with MHC class I-negative tumors, adoptively transferred- or Flt3 ligand-expanded DC promoted NK cell-dependent anti-tumor effects. In vitro studies demonstrated a cell-to-cell contact between DC and resting NK cells that resulted in a substantial increase in both NK cell cytolytic activity and IFN-gamma production. Thus, DC are involved in the interaction between innate and adaptive immune responses.

Newly characterised ex vivo colospheres as a three-dimensional colon cancer cell model of tumour aggressiveness.

BACKGROUND: New models continue to be required to improve our understanding of colorectal cancer progression. To this aim, we characterised in this study a three-dimensional multicellular tumour model that we named colospheres, directly obtained from mechanically dissociated colonic primary tumours and correlated with metastatic potential. METHODS: Colorectal primary tumours (n=203) and 120 paired non-tumoral colon mucosa were mechanically disaggregated into small fragments for short-term cultures. Features of tumours producing colospheres were analysed. Further characterisation was performed using colospheres, generated from a human colon cancer xenograft, and spheroids, formed on agarose by the paired cancer cell lines. RESULTS: Colospheres, exclusively formed by viable cancer cells, were obtained in only 1 day from 98 tumours (47%). Inversely, non-tumoral colonic mucosa never generated colospheres. Colosphere-forming capacity was statistically significantly associated with tumour aggressiveness, according to AJCC stage analysis. Despite a close morphology, colospheres displayed higher invasivity than did spheroids. Spheroids and colospheres migrated into Matrigel but matrix metalloproteinase (MMP)-2 and MMP-9 activity was detected only in colospheres. Mouse subrenal capsule assay revealed the unique tumorigenic and metastatic phenotype of colospheres. Moreover, colospheres and parental xenograft reproduced similar CD44 and CD133 expressions in which CD44+ cells represented a minority subset of the CD133+ population. CONCLUSION: The present colospheres provide an ex vivo three-dimensional model, potentially useful for studying metastatic process.

Peptide immunogen mimicry of a protein-specific structural epitope on human choriogonadotropin.

It is a challenge to construct synthetic immunogens that elicit antibodies (Abs) both directed to conformational epitopes and specific for a complex protein like human choriogonadotropin (hCG). A monoclonal antibody specific for hCG bound to regions around Lys45 of the alpha subunit (hCG alpha) and Asp112 of the beta subunit (hCG beta). A peptide comprising residues 46 to 55 of hCG alpha and residues 106 to 116 of hCG beta elicited Abs in rabbits that were directed to a discontinuous epitope and were specific for hCG. These Abs inhibited the binding of hCG to its receptor. Thus, a synthetic immunogen can mimic a conformational-specific epitope and can be useful for vaccine development.

Expression of human chorionic gonadotropin beta subunit genes in superficial and invasive bladder carcinomas.

Increased serum levels of human chorionic gonadotropin beta subunit (hCG beta) were described previously in patients with bladder cancer. To obtain insight into such production of hCG beta, the expression of hCG beta 7, 8, 5, and 3 genes in bladder carcinomas and normal urothelia was investigated by reverse transcription PCR. Surprisingly, hCG beta mRNAs were detected in both normal urothelial and carcinomatous cells. However, tumor progression was characterized by different patterns of transcription of the hCG beta genes; the beta 7 gene was the only gene transcribed in normal urothelia and Ta tumors included in this study, whereas in addition to beta 7, genes beta 5, 8, and 3 were transcribed in T1 to T4 tumors. Moreover, transcription levels of the latter three genes increased with the stage of the disease. These observations showed that dramatic modifications in the expression of hCG beta genes accompany progression of bladder carcinomas.

Identification and measurement of calcitonin precursors in serum of patients with malignant diseases.

Previous studies have suggested that molecular species larger than the mature calcitonin (CT) are produced by tumors of different origin. In order to study these species, we developed a monoclonal immunoradiometric assay for calcitonin precursors (CT-pr). This assay was based on both monoclonal antibody KC01 directed to the 1-11 region of katacalcin and monoclonal antibody CT08 directed to the 11-17 portion of CT. The sensitivity of this monoclonal immunoradiometric assay for CT-pr was less than 100 pg/ml. Only one of 131 healthy subjects had CT-pr serum levels greater than 100 pg/ml; this value was therefore selected as the standard serum value in healthy individuals. CT-pr was present in the serum of seven of ten patients with advanced renal failure and in that of 21 of 52 patients (40%) with benign liver disease but was undetectable in sera of patients with other benign diseases. The serum CT-pr level was correlated with that of mature CT in patients with medullary carcinoma of the thyroid. In contrast, the serum CT-pr level was frequently elevated in the absence of a detectable CT level in patients with various malignant tumors and, particularly, in those with either tumors of the neuroendocrine system (60%) or hepatocellular carcinomas (62%). CT-pr was detected in tumor extract from a patient with a hepatocellular carcinoma. Moreover, hybridization experiments with total RNA extracted from this tumor demonstrated the presence of RNAs hybridizing with complementary DNA encoding for common region, calcitonin, and katacalcin sequences. These results show that CT precursors are excreted by numerous cancers and might well be useful biological markers for the follow-up of productive tumors.

Malignant transformation of nontrophoblastic cells is associated with the expression of chorionic gonadotropin beta genes normally transcribed in trophoblastic cells.

The beta subunit of human chorionic gonadotropin (hCGbeta) is encoded by four nonallelic CGbeta genes. An assay was developed for distinguishing type I CGbeta allelic genes beta7 and beta6, which possess a GCC codon corresponding to an alanine at position 117 of hCGbeta, from type II CGbeta genes beta8, beta5, and beta3 and its allele beta9, which possess a GAC codon corresponding to an aspartic acid at the same position. In normal trophoblast, hCGbeta is encoded by type II CGbeta genes, whereas normal nontrophoblastic tissues of differing histological origin (breast, prostate, skeletal muscle, bladder, adrenal glands, thyroid, colon, and uterus) express only type I CGbeta genes. We studied the expression of CGbeta genes in 86 tumor specimens collected from patients with breast, bladder, prostate, and thyroid cancer and found that up to 61% of these nontrophoblastic tumors expressed type II CGbeta genes. Experiments performed on tumor tissues and their normal counterparts confirmed that the malignant transformation of nontrophoblastic cells is associated with the expression of type II CGbeta genes. These findings provide the basis for a simple test (the CG117 assay) that may be useful for the diagnosis of the most frequent malignancies.

Simple sequence repeat polymorphism within the p53 gene.

This report describes a new polymorphism, in intron 3 of the p53 gene, which consists of a single repeat of 16 nucleotides, absent in the published wild-type p53 gene sequence. In the Caucasian population tested (n = 82), 28% of individuals were heterozygotes for this polymorphism. Using PCR-based analysis, we were able to demonstrate p53 allelic losses in three of six breast tumors from heterozygote patients tested.

Expression of early placenta insulin-like growth factor in breast cancer cells provides an autocrine loop that predominantly enhances invasiveness and motility.

Early placenta insulin-like growth factor (EPIL) is expressed by a subpopulation of the Her2-positive SKBR3 breast cancer cell line displaying high motility and transendothelial invasiveness in vitro, as recently shown by our group. As a consequence of this, we established cellular models by generating an EPIL-overexpressing SKBR3 cell line, knocked down EPIL by adding specific small interfering RNA (siRNA) to those cells and produced EPIL-enriched and depleted serum-free culture media. EPIL-expressing cells as well as EPIL-induced SKBR3 cells acquired a high capacity for transendothelial invasiveness. We observed a thin and outspread morphology caused by enhanced formation of lamellipodia, i.e. protrusions in the initial phase of motility. In parallel, Her2-positive MDAHer2 breast cancer cells also showed increased invasiveness when induced by EPIL-conditioned medium. A downstream signaling impact of EPIL could be observed in the form of reduced phosphorylation of Her2, erk1/2 and akt, while phospholipase Cgamma1 phophorylation remained unaffected. As an in vivo model for highly motile tumor cells, Paget's disease of the nipple showed simultaneous EPIL and Her2 expression upon immunohistochemical examination using specific antibodies. Such experimental data have been translated to a clinical setting by using a prognostic tissue microarray established from 603 breast cancer cases. Survival data analysis found a significant association between expression levels of EPIL and 5-year overall survival that was dose dependent: EPIL (negative) 84%, EPIL (moderately positive) 77%, EPIL (strongly positive) 48% (P < 0.005). One particular subgroup (7.6% of the cases with full clinical records) that comprised tumors simultaneously expressing EPIL and Her2 represented patients with the poorest 5-year overall survival. The results suggested that EPIL might be a cancer cell-produced growth factor that influences lateral Her2 signaling. Moreover, EPIL may be induced by factors apart from Her2 and may independently provide signaling for cancer invasion and motility.

Human chorionic gonadotropin Molecular forms, detection, and clinical implications.

Different molecular forms of human chorionic gonadotropin (hCG) have been identified in biologic fluids of patients with various physiopathologic processes. These materials include (a) the intact heterodimer hCG comprising two mature a and beta subunits, and (b) the uncombined or free forms of the a (hCGalpha) and beta subunit (hCGbeta), and several fragments o f hCG such as the nicked forms o f both hCG and free hCGbeta and its ending degradation product, the beta-core fragment or hCGbetacf The determination of hCG and related molecules in biologic fluids is usually achieved by immunologic procedures, but discrepancies among kits remain a problem in clinical practice. Specific measurements of hCG and of, independently, its free beta subunit are important in the diagnosis and follow-up of either trophoblastic diseases or testicular cancers, whereas only the free hCGbeta has to be assayed for detection in nongonadal and nonplacental tumors.

Prognostic value of chorionic gonadotropin beta gene transcripts in human breast carcinoma.

The beta subunit of human chorionic gonadotropin is potentially encoded by six genes, which can be categorized into two types based on a sequence change at codon 117: GCC for the type I and GAC for the type II genes. We previously showed that, whereas type I genes were exclusively expressed in normal breast tissues, expression of type II genes was associated with malignant transformation (Bellet, D., et al. Cancer Res., 57: 516-523, 1997). We designed a simple and robust test (the CG117 assay) that measures the percentage of type II over both types of chorionic gonadotropin beta mRNAs. Normal breast tissues consistently had a negative CG117 index, whereas cancer breast tissues showed indexes ranging from 0 to 100%. The prognostic significance of the CG117 index was investigated in a series of 99 unilateral invasive primary breast cancer patients with known long-term outcome (median follow-up, 9 years). The CG117 index was positive in 48 (48.5%) of the 99 tumor mRNA samples. The index was not significantly associated with standard prognostic parameters, including clinical and macroscopic tumor size, histopathological grade, and lymph node status or steroid receptor status. Patients with a positive CG117 index in primary tumor mRNA had significantly shorter metastasis-free survival (P = 0.014) and overall survival (P = 0.038) after surgery, compared to patients with a negative index. The prognostic significance of the CG117 index persisted in Cox multivariate regression analysis, both for metastasis-free survival (P = 0.008) and overall survival (P = 0.016), together with lymph node status (P = 0.027 and P = 0.009, respectively). These findings indicate that the CG117 index may contribute to the identification of high-risk breast cancer patients.

Immune recognition of a molecule naturally presented as a monomeric or an oligomeric structure: the model of the human chorionic gonadotropin alpha subunit.

The immune recognition of a molecule naturally presented as a monomeric or an oligomeric structure is analyzed using the human chorionic gonadotropin alpha subunit (hCG-alpha) as a model. Indeed, hCG-alpha circulates as either a free subunit or combined to the beta subunit (hCG-beta) to form the dimeric hCG hormone. A T cell study was performed in BALB/c (H-2d) mice which were found to be high responders to hCG-alpha. Mice were immunized with the free hCG-alpha or the dimeric hCG alpha/beta, and their lymph node cells were challenged in vitro with either alpha subunits from different species, hCG or peptides spanning the entire primary structure of hCG-alpha. Proliferation and IL-2 assays demonstrated that hCG-alpha-primed lymph node cells responded equally well to hCG-alpha and hCG alpha/beta, suggesting that both the free and combined hCG-alpha subunits are processed in a similar way. Among the various synthetic peptides used, only those mimicking the hCG-alpha(59-92) C-terminus portion were able to stimulate hCG-alpha-primed lymph node cells, demonstrating that this region contains immunodominant T cell recognition site(s). The hCG-alpha(23-43) and (32-59) peptides, although incapable of stimulating T cells primed with hCG-alpha, elicited a T cell response when used as immunogens. These regions encompassed cryptic epitopes which were not generated during hCG-alpha processing in H-2d mice. The T cell epitopes of hCG-alpha above described as immunodominant or cryptic on the free alpha subunit, had similar characteristics when the alpha/beta dimer was used as the immunogen. In contrast, T cells primed with peptides mimicking immunodominant sites recognized differently the hCG-alpha and the hCG alpha/beta antigens. Moreover, the analysis of the B cell response to all the immunogenic hCG-alpha peptides indicated that they bear B and T cell epitopes as well. Antibodies elicited against the hCG-alpha(59-92) or (32-59) peptide were capable of recognizing the alpha subunit in its free form but not in the alpha/beta hCG dimer. Such study deserves attention for the comprehensive mechanisms of the immune response to hCG as well as for the design of anti-hCG vaccines.

The immune response to a synthetic peptide analogous to the 109-145 beta hCG carboxyl-terminus is directed against two major and two minor regions.

The immune response to a 37-amino acid synthetic peptide analogous to the carboxyl-terminal part (109-145) of the human chorionic gonadotropin beta subunit (beta hCG) was studied with monoclonal antibodies selected from 31 cell fusion experiments. Analysis of the immunogenic determinants borne on the synthetic peptide (CTP) showed a prevailing response to two immunodominant regions. The first was located on the 110-116 amino acid sequence of the CTP which is also the most hydrophilic region: 50% of anti-CTP antibodies selected for their high binding to 125I beta hCG were directed to this sequence. A second immunodominant portion was recognized by four antibodies, and comprised amino acids 134 to 139, representing a highly O-glycosylated region on the native protein. Moreover, a unique antibody designated FB13 bound to a region located on the last seven amino acids (139-145) of beta hCG. Finally, a hypothetical conformational determinant was recognized by antibody FB02 within the 121-145 region. Thus, the immune response to CTP was directed against two major and two minor regions. These antigenic determinants were demonstrated to be accessible for antibody binding on both the hCG molecule and its beta subunit. Localization of these epitopes suggests a relationship between the hydrophilicity and the immunological potency of different CTP regions.

Structural probing of human lutropin using antibodies raised against synthetic peptides constructed by classical and multiple antigen peptide system approaches.

Antibodies were elicited against a synthetic peptide which encompassed two different regions of the human lutropin beta-subunit (hLH-beta). These antibodies were raised against either the peptide which was assembled using a conventional approach and conjugated to the tetanus toxoid, or with the peptide assembled using the multiple antigen peptide system approach. Automated simultaneous synthesis of the two forms of the immunizing peptide was successfully achieved. Animal injected with the peptide conjugated to tetanus toxoid produced high titers of antibodies to the synthetic peptide, but did not bind to the native hLH-beta subunit. In contrast, antisera induced by the peptide in its MAP form displayed reactivity with both the peptide and the native hLH-beta subunit; these latter antisera appeared to preferentially recognize the beta 47-55 portion of the molecule and were able to bind to the beta-subunit of human choriogonadotropin. Present results demonstrate that the beta 47-55 region is accessible to antibody binding and appears to be located at the surface of both hLH-beta and hLH. Moreover, this study confirms that the MAP approach provides a chemically unambiguous method for obtaining antibodies of predetermined specificity, capable of recognizing cognate sequences of various native proteins.

Optimization of silver nanowire-based transparent electrodes: effects of density, size and thermal annealing.

Silver nanowire (AgNW) networks are efficient as flexible transparent electrodes, and are cheaper to fabricate than ITO (Indium Tin Oxide). Hence they are a serious competitor as an alternative to ITO in many applications such as solar cells, OLEDs, transparent heaters. Electrical and optical properties of AgNW networks deposited on glass are investigated in this study and an efficient method to optimize them is proposed. This paper relates network density, nanowire dimensions and thermal annealing directly to the physical properties of the nanowire networksusing original physical models. A fair agreement is found between experimental data and the proposed models. Moreover thermal stability of the nanowires is a key issue in thermal optimization of such networks and needs to be studied. In this work the impact of these four parameters on the networks physical properties are thoroughly investigated via in situ measurements and modelling, such a method being also applicable to other metallic nanowire networks. We demonstrate that this approach enables the optimization of both optical and electrical properties through modification of the junction resistance by thermal annealing, and a suitable choice of nanowire dimensions and network density. This work reports excellent optical and electrical properties of electrodes fabricated from AgNW networks with a transmittance T = 89.2% (at 550 nm) and a sheet resistance of Rs = 2.9 Ω â–¡(-1), leading to the highest reported figure of merit.

Specific detection of type II human chorionic gonadotropin beta subunit produced by trophoblastic and neoplastic cells.

BACKGROUND: The sequence of the beta-subunit of human chorionic gonadotropin (hCGß) varies depending on whether hCGß is encoded by type I or type II genes. Type II genes are upregulated in trophoblast and cancer but hCGß can be detected in the serum of nonpregnant women and healthy individuals. We aimed to determine whether monoclonal antibody (mAb) FBT11-II specifically detects hCGß encoded by type II genes (type II hCGß). METHODS: Competitive inhibition assays with synthetic peptides, immunocytochemical and immunohistochemical studies, type II hCGß dosing immunoassays and sequencing of CGB genes were performed. RESULTS: Competitive inhibition assays determined that mAb FBT11-II recognizes the type II hCGß derived peptide. CGB mRNA sequencing of JEG-3 (trophoblastic) and T24 (bladder) cell lines confirmed that JEG-3 expresses type II genes while T24 expresses exclusively type I. FBT11-II only recognizes JEG-expressed hCGß. Placenta immunohistochemical studies confirmed that type II hCGß expression is restricted to the syncytiotrophoblast. Immunoassays detected type II hCGß in serum of patients with either nontrophoblastic cancers or fetal Down syndrome. CONCLUSION: Type II gene expression can be detected using FBT11-II. This specific recognition could improve the clinical usefulness of assays aimed at either managing aggressive tumors or screening for Down syndrome.

Ectopic beta-human chorionic gonadotropin production by a human hepatoma cell line (FOCUS): isolation and immunochemical characterization.

We have established a human hepatocellular carcinoma cell line designed FOCUS that produces and secretes the beta-subunit of hCG. In the study of beta hCG production by FOCUS cells, we have developed and employed a series of monoclonal immunoradiometric assays (IRMAs) that detect epitopes unique to beta hCG, alpha hCG, hCG, and sequence-specific regions of the carboxyl-terminal peptide of beta hCG. The cells secrete approximately 15 ng beta hCG/10(6) cells and per 24 h; however, we were unable to detect either hCG or the alpha-subunit. The ectopic beta hCG was subsequently affinity purified from the culture medium and partially characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The mol wt of ectopic beta hCG was approximately 35,000 daltons. Immunochemical analysis of ectopic beta hCG by sequence-specific monoclonal antibodies revealed that epitopes corresponding to amino acid sequences 109-115, 121-145, 134-140, and 139-145 of the carboxyl-terminal peptide were present. FOCUS cells also demonstrate an intracytoplasmic localization of beta hCG by immunoperoxidase-staining techniques. Taken together, these findings suggest that FOCUS cells produce and secrete only beta hCG and that thus far, its physical properties appear indistinguishable from those of the native subunit. This unique cell line will be useful to study beta hCG gene(s) regulation as well as the mechanisms of ectopic beta hCG production and secretion.