Observational multicentric study to evaluate efficacy, adverse effects and acceptance of bowel cleansing prior to colonoscopy with sodium picosulfate / magnesium citrate formulation CitraFleet®.

The various efficient methods available for bowel preparation prior to colonoscopy differ in patient acceptance. Combining the laxative sodium picosulfate with hyperosmotic magnesium citrate, used in this study in the formulation CitraFleet(®), allows the uptake of the purgative substances as a solution of low volume. This observational study with 737 patients evaluated efficacy of bowel preparation, potential side or adverse effects and patient acceptance of this medicinal product when used by resident physicians in Germany.Colon cleansing with CitraFleet(®) was considered very good to sufficient in 95.2 % of the patients and inadequate in only 4.8 %. In 75 % of the colonoscopies, bowel preparation was rated very good or good. Compared to the standard regimen of two portions taken the day before endoscopy, cleaning efficacy was better when patients received one of the doses on the morning of the day of colonoscopy. The quality of bowel preparation was rated lower by gastroenterologists without any prior experience with sodium picosulfate/magnesium citrate. The overall assessment of the colon cleansing procedure by the 76 participating physicians was very positive and patient acceptance was also very high which can be considered a clear advantage over alternative methods. Efficacy of colon cleansing with CitraFleet(®) was not substantially affected by typical deviations from the recommended standard procedure, emphasizing the robustness of the method. Only one of the patients reported a mild adverse effect potentially caused by the cleansing agents.

[Basic in vitro studies on VEGF inhibition with aflibercept: similarities and differences to other VEGF-binding therapeutic proteins]. / Grundlegende In-vitro-Untersuchungen zur VEGF-Inhibition mit Aflibercept: Gemeinsamkeiten und Unterschiede zu anderen VEGF-bindenden therapeutischen Proteinen.

Patients suffering from various retinal diseases benefit from therapies directed against the vascular endothelial growth factor (VEGF). Aflibercept (Eylea) is another VEGF-binding protein available for intravitreal injection, in addition to the antibody bevacizumab (Avastin) and the F(ab) fragment ranibizumab (Lucentis). Aflibercept's distinct structure and broader binding specificity may have clinically relevant consequences, which is supported by basic in vitro studies and observations in animal eyes. All pathological processes involving neovascularisation are driven by the dominant action of VEGF, but other factors including placenta growth factor (PlGF), a mitogenic protein for retinal endothelial cells, potentially modulate its effects. Aflibercept is an inhibitor of both VEGF and PlGF and therefore may have superior therapeutic effects in some cases. However, whether or not aflibercept's broader binding specificity or different affinities for the different VEGF-binding proteins to VEGF result in substantially diverse therapeutic efficiencies has not yet been clarified. In vitro studies confirm that aflibercept efficiently prevents or normalises VEGF-stimulation of retinal cells and disturbance of their barrier function. These experiments also show that aflibercept is taken up by important retinal cell types and affects their normal function, i.e., migration of endothelial cells and phagocytosis of pigment epithelial cells. In accordance with a role of the Fc domains of aflibercept and bevacizumab, substantial amounts of both proteins are internalised, whereas only a small portion of ranibizumab enters the cells. Internalisation and storage by ocular cells, also observed in vivo after intravitreal injection into eyes of monkeys, may result in not yet recognised side effects during long-term treatment of patients with certain VEGF-binding proteins.

[Treatment of diabetic macular oedema with the VEGF inhibitors ranibizumab and bevacizumab: conclusions from basic in vitro studies]. / Therapie des diabetischen Makulaödems mit den VEGF-Inhibitoren Ranibizumab und Bevacizumab: Schlüsse aus grundlegenden In-vitro-Untersuchungen.

Diabetic macular oedema (DMO) which may occur at all stages of diabetic retinopathy (DR) is a severe vision-threatening complication. In most cases, laser treatment does not improve visual acuity. Therefore research in ophthalmology focuses on the improvement of the prognosis of DMO patients with a drug-based DMO therapy. Vascular endothelial growth factor (VEGF) is considered the most important therapeutic target because this growth factor also is the most potent permeability factor affecting the inner retinal barrier formed by endothelial cells (ECs). Compared to its angiogenic stimulation of proliferation and migration of ECs, effects of VEGF on permeability have not been studied in all details. In vitro investigations on the behaviour of primary or immortalised retinal endothelial cells confirmed the key role of VEGF in the regulation of the permeability of the inner retinal barrier. Despite the presence of a variety of other factors found to be elevated in DR, a VEGF-disrupted barrier can be completely restored with the VEGF-inhibiting ranibizumab (Lucentis®) and bevacizumab (Avastin®) when applied at clinically achievable concentrations. The antibody bevacizumab, but not the antibody fragment ranibizumab, accumulates in both retinal EC and pigment epithelial cells during prolonged treatment. This observation might be relevant because patients are often treated for several years and additional long-term side effects may be recognised in the future.

[Effect of VEGF165 and the VEGF aptamer pegaptanib (Macugen) on the protein composition of tight junctions in microvascular endothelial cells of the retina]. / Wirkung von VEGF165 und dem VEGF-Aptamer Pegaptanib (Macugen) auf die Zusammensetzung der Tight Junctions mikrovaskulärer Endothelzellen aus der Retina.

BACKGROUND: VEGF signalling is deregulated in diabetic retinopathy. Therefore, VEGF inhibitors like the modified RNA-oligonucleotide pegaptanib (VEGF aptamer, Macugen) which inhibits the interaction of VEGF(165) with its receptors, are currently being discussed as therapeutic options in the treatment of diabetic retinopathy. VEGF(165) does not only stimulate the proliferation and migration of endothelial cells but also induces delocalization of occludin which is part of the so-called tight junctions of endothelial cells likely associated with the breakdown of the blood-retina barrier. METHODS AND MATERIAL: To further investigate the mechanisms of action of VEGF and its inhibitor, we studied the influence of VEGF(165) and/or pegaptanib on the protein composition of tight junctions in immortalised endothelial cells of the bovine retina (iBREC) by immunofluorescence staining. RESULTS: The tight junction proteins ZO-1, occludin and claudin-5 are strongly expressed at the plasma membrane in confluent iBREC, but are located in the cytoplasm in non-confluent cells. In the presence of 50 ng/ml VEGF(165), occludin was found in the cytoplasm after 1 to 2 days, whereas claudin-5 was not and ZO-1 was only weakly influenced. However, after addition of 33 microg/ml pegaptanib for 24 h to VEGF(165)-treated iBREC, all tight junction proteins tested were again strongly expressed in the plasma membrane. CONCLUSION: These results confirm an important role of tight junction proteins in the mechanisms of action of VEGF and pegaptanib on endothelial cells.

[In vitro studies on the mechanism of action of VEGF and its inhibitors]. / In-vitro-Untersuchungen zum Wirkungsmechanismus von VEGF und seinen Inhibitoren.

VEGF expression and signalling are deregulated in diabetic retinopathy. Cellular processes like migration and proliferation as well as control of the permeability of the endothelium by VEGF are regulated as a consequence of its binding to the VEGF receptor 2. Proteins forming tight junctions between microvascular endothelial cells of the retina are delocated to the cytoplasm after treatment with VEGF(165), likely leading to the breakdown of the blood-retina barrier. VEGF-inhibitors such as a VEGF-aptamer (modified RNA-oligonucleotide; pegaptanib) or specific antibodies/antibody fragments (bevacizumab, ranibzumab) which directly interfere with the interaction of VEGF with its receptors are considered to be promising novel therapeutics to treat diabetic retinopathy and age-related macular degeneration. In vitro studies using microvascular endothelial cells will help to clarify the mechanisms of action of VEGF and its inhibitors. In particular, the influence of VEGF isoforms and the inhibitor ranibizumab on the proliferation and migration of bovine retinal microvascular endothelial cells was studied, as well as the rearrangement of tight-junction proteins after treatment of the cells with VEGF(165) and specific inhibitors. In addition to a review of recent publications in the field, primary data from our own studies are presented in this article.

[Predicting response to therapy in breast cancer]. / Vorhersage des Therapieansprechens beim Mammakarzinom.

Molecular staging of breast cancer with microarray technologies leads to different gene expression profiles distinguishing 4 special groups: luminal A and B subtype, HER2 subtype and basal subtype. These 4 groups show a different prognosis as well as different behaviours and responses to adjuvant therapy. The development of gene expression profiles to classify breast cancer may contribute to the targeted institution of adjuvant therapies. Especially the 21-gene recurrence score (Oncotype DX) and the 70-gene profile (Mamma-print) have become intensively examined prognostic and predictive tools. As chemotherapy is an integral component of adjuvant therapy in early breast cancer but estrogen-receptor-positive breast cancer is the most common type, patient selection for adjuvant chemotherapy is of particular interest. In instances when the benefit from chemotherapy seems modest, there is a decision making tool beside traditional histopathological parameters that might provide additional objective prognostic and predictive information. Those genomic decision making approaches may yield more rational treatment choices and may keep patients from systemic treatment modalities of lower value.

VEGF-induced effects on proliferation, migration and tight junctions are restored by ranibizumab (Lucentis) in microvascular retinal endothelial cells.

BACKGROUND: Because vascular endothelial growth factor (VEGF) signalling is deregulated in diabetic retinopathy, the potential therapeutic effects of VEGF inhibitors such as the human VEGF-specific antibody ranibizumab are currently being tested. A study was undertaken to determine whether VEGF-stimulated processes in retinal endothelial cells are reversed by ranibizumab. METHODS: The influence of VEGF(121) and VEGF(165) on the proliferation and migration of immortalised bovine retinal endothelial cells (iBREC) was studied in the presence and absence of ranibizumab. In addition, the protein composition of tight junctions in the presence of VEGF and its inhibitor in iBREC was investigated. RESULTS: While both isoforms stimulated proliferation of iBREC, only VEGF(165) influenced cell migration. The addition of ranibizumab counteracted this stimulation without inhibition of the basal levels of migration and proliferation. Plasma membrane staining of the tight junction proteins occludin and claudin-1 disappeared in the presence of VEGF(165); there was no effect on claudin-5 and ZO-1 was only weakly affected. The addition of ranibizumab restored plasma membrane localisation of occludin and claudin-1. For claudin-1, the variation in total protein expression corresponded with the observed effects of VEGF(165) and ranibizumab. CONCLUSION: Ranibizumab reverses proliferation and cell migration stimulated by VEGF and delocalisation of tight junction proteins induced by VEGF(165) in iBREC.

Ultrasound-guided large-core needle biopsies of breast lesions: analysis of 962 cases to determine the number of samples for reliable tumour classification.

The objective of this one-institutional study was to determine the number of large-core needle biopsies (LCNB), under three-dimensional ultrasound (3D-US) validation, that are sufficient to obtain a reliable histological diagnosis of a sonographically detectable breast lesion. Over an 28-month period, 962 sonographically guided LCNB were performed under 3D-US validation to assess 962 breast lesions. All biopsies were carried out with an automated core biopsy device fitted with 14-gauge (22 mm excursion) needles. Data of 962 biopsied breast lesions were gathered. Surgical follow-up was available for 659 lesions. Breast malignancies were diagnosed by ultrasound-guided LCNB with a sensitivity of 98.2% by performing three cores per lesion. In few cases, the open surgical specimen revealed the presence of invasive carcinomas in contrast to initial LNCB-based classification as ductal carcinomas in situ (DCIS, 11 lesions), lobular carcinoma in situ (one lesion), and atypical ductal hyperpasia (one lesion). Owing to disagreement between classification based on breast-imaging and histological findings, eight of these tumours were subsequently excised. Of the lesions that were removed at the patients' requests despite benign LCNB diagnosis, two were infiltrating carcinoma and one a DCIS. We demonstrate that three 3D-US-guided percutaneous core specimens are sufficient to achieve tissue for a reliable histological assessment of sonographically detectable breast lesions and allow the detection of malignancies with high sensitivity and low rate of false-negative diagnoses.

Methylation mosaicism of 5'-(CGG)(n)-3' repeats in fragile X, premutation and normal individuals.

Fragile X syndrome (FRAXA) is characterized at the molecular level by an expansion of a naturally occurring 5'-(CGG)(n)-3' repeat in the promoter and 5'-untranslated region (5'-UTR) of the fragile X mental retardation (FMR1) gene on human chromosome Xq27.3. When expanded, this region is usually hypermethylated. Inactivation of the FMR1 promoter and absence of the FMR1 protein are the likely cause of the syndrome. By using the bisulfite protocol of the genomic sequencing method, we have determined the methylation patterns in this region on single chromosomes of healthy individuals and of selected premutation carriers and FRAXA patients. In control experiments with unmethylated or M- Sss I-premethylated DNAs, this protocol has been ascertained to reliably detect all cytidines or 5-methylcytidines as unmethylated or methylated nucleotides, respectively. Analyses of the DNA from FRAXA patients reveal considerable variability in the lengths of the 5'-(CGG)(n)-3' repeats and in the levels of methylation in the repeat and the 5'-UTR. In one patient (OEl) with high repeat length hetero-geneity ( n = 15 to >200), shorter repeats (n = 20-80) were methylated or unmethylated, longer repeats ( n = 100-150) were often completely methylated, but one repeat with n = 160 proved to be completely unmethylated. This type of methylation mosaicism was observed in several FRAXA patients. In healthy females, methylated 5'-CG-3' sequences were found in some repeats and 5'-UTRs, as expected for the sequences from one of the X chromosomes. The natural FMR1 promoter is methylation sensitive, as demonstrated by the loss of activity in transfection experiments using the unmethylated or M- Sss I-premethylated FMR1 promoter fused to the luciferase gene as an activity indicator.

The human 20-kDa 5'-(CGG)(n)-3'-binding protein is targeted to the nucleus and affects the activity of the FMR1 promoter.

Previous reports have described the human DNA CGG repeat-binding protein (CGGBP1 or p20), which binds specifically to nonmethylated, but not to methylated, 5'-(CGG)(n)-3' repeats in the promoter of the fragile X mental retardation 1 (FMR1) gene. The results of transfection experiments into human HeLa cells using a p20-green fluorescent protein fusion construct indicate that the p20 protein is targeted to the nucleus. By deletion analyses, a nuclear localization signal has been found between amino acids 80 and 84. Deletions between amino acids 69 and 71 and between 95 and 167 interfere with 5'-(CGG)(n)-3' binding. The results of electrophoretic mobility shift assays using DNA with 5'-(CGG)(n)-3' repeats of different lengths render it likely that oligomers of the p20 protein bind to the repeat. In cotransfection experiments, the activity of the FMR1 promoter is reduced by the presence of p20. Upon transfection of the p20 cDNA construct into HeLa cells, transcription of the endogenous FMR1 gene is decreased. The green fluorescent protein-p20 fusion protein associates preferentially with the telomeres of the short arms of human chromosomes 13, 14, 15, 21, and 22. Their telomeres carry the genes for the 28 S rRNA, which contain 5'-(CGG)(n)-3' repeats. The translated region of the p20 gene from three healthy, five fragile X syndrome, and five premutation-carrying individuals has been sequenced, but mutations have not been detected.

Neural cell surface differentiation antigen gp130(RB13-6) induces fibroblasts and glioma cells to express astroglial proteins and invasive properties.

Transient expression of the differentiation and tumor cell surface antigen gp130(RB13-6) characterizes a subset of rat glial progenitor cells susceptible to ethylnitrosourea-induced neurooncogenesis. gp130(RB13-6) is as a member of an emerging protein family of ecto-phosphodiesterases/nucleotide pyrophosphatases that includes PC-1 and the tumor cell motility factor autotaxin. We have investigated the potential role of gp130(RB13-6) in glial differentiation by transfection of three cell lines of different origin that do not express endogenous gp130(RB13-6) (NIH-3T3 mouse fibroblasts; C6 and BT7Ca rat glioma cells) with the cDNA encoding gp130(RB13-6). The effect of gp130(RB13-6) expression was analyzed in terms of overall cell morphology, the expression of glial cell-specific marker proteins, and invasiveness. Transfectant sublines, consisting of 100% gp130(RB13-6)-positive cells, exhibited an altered, bipolar morphology. Fascicular aggregates of fibroblastoid cells subsequently developed into mesh-like patterns. Contrary to the parental NIH-3T3 and BT7Ca cells, the transfectant cells invaded into collagen type I. As shown by immunofluorescence staining of the transfectant sublines as well as of primary cultures composed of gp130(RB13-6)-positive and -negative cells, expression of gp130(RB13-6) induced coexpression of proteins typical for glial cells and their precursors, i.e., glial fibrillary acidic protein, the low affinity nerve growth factor receptor, and the neural proteins Thy-1, Ran-2, and S-100. In accordance with its expression in the immature rat nervous system, gp130(RB13-6) may thus have a significant role in the glial differentiation program and its subversion in neurooncogenesis.

Rapid protein sequencing by tandem mass spectrometry and cDNA cloning of p20-CGGBP. A novel protein that binds to the unstable triplet repeat 5'-d(CGG)n-3' in the human FMR1 gene.

The autonomous expansion of the unstable 5'-d(CGG)n-3' repeat in the 5'-untranslated region of the human FMR1 gene leads to the fragile X syndrome, one of the most frequent causes of mental retardation in human males. We have recently described the isolation of a protein p20-CGGBP that binds sequence-specifically to the double-stranded trinucleotide repeat 5'-d(CGG)-3' (Deissler, H., Behn-Krappa, A., and Doerfler, W. (1996) J. Biol. Chem. 271, 4327-4334). We demonstrate now that the p20-CGGBP can also bind to an interrupted repeat sequence. Peptide sequence tags of p20-CGGBP obtained by nanoelectrospray mass spectrometry were screened against an expressed sequence tag data base, retrieving a clone that contained the full-length coding sequence for p20-CGGBP. A bacterially expressed fusion protein p20-CGGBP-6xHis exhibits a binding pattern to the double-stranded 5'-d(CGG)n-3' repeat similar to that of the authentic p20-CGGBP. This novel protein lacks any overall homology to other known proteins but carries a putative nuclear localization signal. The p20-CGGBP gene is conserved among mammals but shows no homology to non-vertebrate species. The gene encoding the sequence for the new protein has been mapped to human chromosome 3.

Characterization of FMR1 promoter elements by in vivo-footprinting analysis.

Fragile X syndrome is associated with silencing of the FMR1 gene. We studied the transcriptional regulation, by analysis of the FMR1 promoter region for the presence of in vivo protein/DNA interactions and for cytosine methylation at the single-nucleotide level. Four protein-binding sites were present in the unmethylated promoter of the active FMR1 gene. In the methylated promoter of inactive genes no footprints were detected, and no evidence of active repression was found in the region investigated. We propose that the silencing of FMR1 gene transcription results from a lack of transcription-factor binding.

In vitro differentiation of neural progenitor cells from prenatal rat brain: common cell surface glycoprotein on three glial cell subsets.

Glial progenitor cell differentiation and cell lineage relationships during brain development are complex hierarchical processes depending on genetic programming, cell-cell interactions, and microenvironmental factors. The identification of precursor cell-specific antigens provides a tool for the study of both normal development and deviations from lineage-specific differentiation associated with malignant transformation. Monoclonal antibody (mAb) RB13-6 recognizes a 130-kDa cell surface glycoprotein (gp130RB13-6) expressed by a subset of 9OAcGD3-positive glial precursor cells scattered in the rat neuroepithelium on prenatal day (PRD) 13. During prenatal development the fraction of gp130RB13-6-positive fetal brain cells (FBC) decreased from about 18% (PRD 14) to about 1.5% (PRD 22), coinciding with increasing fractions of more mature cell types, as indicated by the elevated expression of p24RB21-15, another cell surface determinant specified by mAb RB21-15 (Kindler-Röhrborn et al.; Differentiation 30:53-60, 1985) and other neural cell type-specific markers. Accordingly, gp130RB13-6 positive precursor cells were localized in the ventricular zones throughout brain development. Concomitant with their formation and in the adult rat brain, ependymal layers lining the ventricular surface, choroid plexus, and the leptomeninges were intensely labeled by anti-gp130RB13-6 mAb. As visualized by confocal laser scanning microscopy of FBC cultures from PRD 13, gp130RB13-6 was coexpressed with the RC1 antigen by progenitor cells morphologically resembling radial glia cells. In addition, a very small subpopulation of astrocytes coexpressing gp130RB13-6 and glial fibrillary acidic protein (GFAP; < 5%) occurred 3 days after seeding. Primary FBC cultures from PRD 18 contained an increased subset of astrocytes coexpressing gp130RB13-6 and GFAP (approximately 25% of all gp130RB13-6 expressing cells), apparently generated from gp130RB13-6-positive precursors. Corresponding to in vivo conditions, ciliated ependymal cells but also microglial cells/macrophages and leptomeningeal cells showed strong expression of gp130RB13-6 in culture. We thus present a new glycoprotein on the cell surfaces of a glial progenitor cell subset for further studies of cell lineage relationships between radial glia cells, astrocytes, and ependymal cells.

Characterization of rat NCA/CD9 cell surface antigen and its expression by normal and malignant neural cells.

As part of investigations on ethylnitrosourea (EtNU)-induced neuro-oncogenesis in the rat, we have produced monoclonal antibodies (Mabs) specific for neural cell surface antigens (NCAs) by immunization with cells of the clonal tumorigenic neural rat cell line BT4Ca. Mabs designated as anti-NCA (alpha NCA1, alpha NCA2, alpha NCA3, alpha NCA4, and alpha NCA5) recognize proteins of 25 kDa and 23 kDa, as shown by immunoprecipitation and Western blot. The predominant 25-kDa protein was purified from BT4Ca cells by immunoaffinity chromatography with immobilized Mab alpha NCA1 and identified by N-terminal sequencing as the rat homologue of the CD9 antigen. Identification of proline as N-terminal amino acid of the purified protein suggests post-translational modification of CD9 in the rat central nervous system. The NCA/CD9 protein was localized in distinct regions of fetal and adult rat brain by immunofluorescence staining of frozen sections. Flow cytometric analyses of isolated fetal rat brain cells (FBC) showed that the proportion and number of NCA/CD9-expressing cells increased during prenatal development. Immunoreactivity of approximately 40% of brain cells isolated 13 days post conception (p.c.) indicated that NCA/CD9 is expressed by neuronal precursors at this stage of development. In primary cultures of rat FBC isolated 18 days p.c., the NCA/CD9 antigen was expressed by all premature and mature astrocytes, oligodendrocytes, ependymal cells, and microglial cells, but not by E-N-CAM-expressing neuronal progenitor cells and neurons. Furthermore, eight out of ten EtNU-induced malignant neural rat cell lines as well as EtNU-induced tumors of the central and peripheral nervous system exhibited intermediate or strong immunoreactivity with Mab alpha NCA1. Expression of the NCA/CD9 protein is, therefore, characteristic of both normal glial precursor cells and their malignant counterparts in the rat.

Purification of nuclear proteins from human HeLa cells that bind specifically to the unstable tandem repeat (CGG)n in the human FMR1 gene.

Autonomous expansions of trinucleotide repeats with the general structure 5'-d(CNG)n-3' are associated with several human genetic diseases. We have characterized nuclear proteins binding to the unstable 5'-d(CGG)n-3' repeat. Its expansion in the human FMR1 gene leads to the fragile X syndrome, one of the most frequent causes of mental retardation in human males. Electrophoretic mobility shift assays using nuclear extracts from several human and other mammalian cell lines and from primary human cells demonstrated specific binding to double-stranded DNA fragments containing only a 5'-d(CGG)17-3' repeat or the repeat and flanking genomic sequences of the human FMR1 gene. Protein binding was inhibited by complete methylation of the trinucleotide repeat. The complex formed with crude nuclear extract apparently did not contain the human transcription factor Sp1 that binds to a characteristic GC-rich sequence. A 20-kDa protein involved in specific binding to the double-stranded 5'-d(CGG)17-3' repeat was purified from HeLa nuclear extracts by DNA affinity chromatography.

Restriction endonuclease BsoFI is sensitive to the 5'-methylation of deoxycytidines in its recognition sequence.

The isoschizomeric restriction endonucleases Fnu4HI and BsoFI cleave DNA at 5'-GCdecreasesNGC-3' sequences. Fnu4HI has been shown to be inhibited by 5'-CG-3'methylation in the sequences 5'-GmCGGC-3' or 5'-GCGGmCG-3'. We have now investigated the methylation sensitivity of BsoFI by testing its activity on plasmid DNA 5'-CG-3' methylated with the M.SssI DNA methyltransferase or on synthetic (CGG)n repetitive oligodeoxyribonucleotides which have been partly or completely C methylated. The data demonstrate that BsoFI cannot cleave at its recognition sequence when it is completely 5'-CG-3' methylated. These enzymes have proven to be useful in analyses of the methylation status in (CGG)n repeats of the human genome.

Affinity purification and cDNA cloning of rat neural differentiation and tumor cell surface antigen gp130RB13-6 reveals relationship to human and murine PC-1.

Monoclonal antibody RB13-6 recognizes a subset of rat brain glial precursor cells that are highly susceptible to malignant conversion by the carcinogen N-ethyl-N-nitrosourea. The corresponding cell surface antigen was identified as a membrane glycoprotein (gp130RB13-6) and purified by immunoaffinity chromatography from the tumorigenic neuroectodermal rat cell line BT4Ca. Sequencing of 5 endoproteinase-generated peptides of the purified antigen permitted the specific amplification of a cDNA fragment by reverse transcription-polymerase chain reaction and subsequent isolation of the complete coding sequence from a fetal rat brain cDNA library. The derived amino acid sequence indicates that the RB13-6 antigen is related to the human and murine plasma cell membrane protein PC-1, a nucleotide pyrophosphatase/alkaline phosphodiesterase and ectoprotein kinase. Similarly, purified gp130RB13-6 possesses 5'-nucleotidase activity that can be inhibited with EDTA. Different from PC-1, gp130RB13-6 isolated from BT4Ca cells is not a disulfide-linked dimer and contains an RGD-tripeptide sequence which, together with other structural features, suggests a possible function in cell adhesion and its subversion in malignant phenotypes.