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Biomedical subjects

W Schmiegel

Publications and source records attributed to W Schmiegel.

At least 19 recordsLinked to original sources
PubMed2000

Smad4/DPC4-mediated tumor suppression through suppression of angiogenesis.

Smad4/DPC4 (deleted in pancreatic carcinoma, locus 4) is a tumor suppressor gene lost at high frequency in cancers of the pancreas and other gastrointestinal organs. Smad4 encodes a key intracellular messenger in the transforming growth factor beta (TGF-beta) signaling cascade. TGF-beta is a potent inhibitor of the growth of epithelial cells; thus, it has been assumed that loss of Smad4 during tumor progression relieves this inhibition. Herein, we show that restoration of Smad4 to human pancreatic carcinoma cells suppressed tumor formation in vivo, yet it did not restore sensitivity to TGF-beta. Rather, Smad4 restoration influenced angiogenesis, decreasing expression of vascular endothelial growth factor and increasing expression of thrombospondin-1. In contrast to the parental cell line and to control transfectants that produced rapidly growing tumors in vivo, Smad4 revertants induced small nonprogressive tumors with reduced vascular density. These data define the control of an angiogenic switch as an alternative, previously unknown mechanism of tumor suppression for Smad4 and identify the angiogenic mediators vascular endothelial growth factor and thrombospondin-1 as key target genes.

Animals↗
PubMed2000

Does glucagon stimulation predict oral glucose tolerance in patients after simultaneous pancreas-kidney transplantation?

BACKGROUND: Exogenous glucagon rapidly stimulates insulin secretion. This test has been used to estimate insulin secretory capacity, which may predict oral glucose tolerance in patients after pancreas transplantation. METHODS: In 32 pancreas-kidney transplant recipients, in 10 nondiabetic kidney transplant recipients, and in 9 healthy control subjects, a glucagon stimulation test (1 mg i.v.) and a 75-g oral glucose tolerance test were performed with determination of glucose, insulin, and C-peptide profiles. RESULTS: Of 16 pancreas transplant recipients with the lowest insulin responses after glucagon, 7 had an impaired oral glucose tolerance, in contrast to 1 of 16 with high insulin responses (P=0.037). A low insulin response after glucagon was associated with significantly lower 120-min glucose concentrations (P=0.043) and a lower integrated incremental insulin response after oral glucose (P=0.006). CONCLUSIONS: In pancreas-kidney transplant recipients, a low insulin response after intravenous glucagon predicts a reduced insulin response after oral glucose and an impaired oral glucose tolerance. This simple test may be helpful in the follow-up of pancreas transplant recipients.

Adult↗
PubMed2000

Induction of cell proliferation arrest and apoptosis in hepatoma cells through adenoviral-mediated transfer of p53 gene.

BACKGROUND/AIM: Loss of p53 function is common in hepatocellular carcinoma and is associated with an extremely poor prognosis. The aim of the study was to evaluate the biologic effect of adenoviral-mediated gene transfer of wild-type p53 gene in four hepatoma cell lines with different p53 genetic makeup. METHODS: Recombinant adenovirus expressing wild-type p53 was used. Recombinant adenoviruses with either an empty expression cassette or expressing beta-galactosidase gene served as controls. RESULTS: High-level expression of wild-type p53 was achieved with adenoviral-mediated gene transfer. The expressed p53 protein showed nuclear localization and its expression was associated with an induction of p21 and bax expression. Expression of the p53 gene was associated with inhibition of tumor cell proliferation and induction of apoptosis. Expression of p53 was also associated with an upregulation of CD95 (Apo-1/Fas) gene expression, which may predispose the tumor cells to undergo apoptosis induced by the Fas Ligand/Fas cytolytic pathway. An additional anti-tumor effect, in terms of allowing the replication-defective adenovirus to replicate, was observed in hepatoma cells with homozygous deletion of p53 genes and to a lesser extent, hepatoma cells with mutated p53 genes. CONCLUSIONS: These data showed that adenoviral-mediated gene transfer is effective in delivering p53 gene to tumor cells, and the multiple pathways involved in their antitumor activities.

Adenoviridae↗
PubMed2000

Expression patterns of placenta growth factor in human melanocytic cell lines.

Expression patterns of the angiogenic placenta growth factor and its receptor neuropilin-1 were assessed in normal human melanocytes, SV40T-transformed melanocytes, and melanoma cells derived from primary and metastatic lesions. As determined by reverse transcription-polymerase chain reaction all primary and metastatic melanoma cell lines tested and SV40T-transformed melanocytes coexpressed two placenta growth factor splice variants (placenta growth factor-1 and -2) as well as neuropilin-1 mRNA. Placenta growth factor protein was detected in conditioned media derived from five of eight melanomas and from SV40T-transformed melanocytes. In contrast to melanoma cells, normal melanocytes did not express placenta growth factor mRNA at detectable levels and did not secrete placenta growth factor protein. By contrast, neuropilin-1 transcripts were detected in some of the normal melanocytes. Secretion of placenta growth factor by melanoma cells appeared to be constitutive because it was not affected by the addition of exogenous growth factors including insulin, epidermal growth factor, or basic fibroblast growth factor to culture media. Although melanoma cells expressed both, neuropilin-1 and flt-1, exogenous homodimeric placenta growth factor had no effect on melanoma cell growth. Similarly, placenta growth factor did not induce urokinase-type plasminogen activator production in these cells. These findings demonstrate that melanoma progression is accompanied by deregulated, constitutive placenta growth factor expression. Placenta growth factor, however, serves no apparent autocrine role in melanoma proliferation. Further studies are needed to define the relative contribution of placenta growth factor to the angiogenic properties of human melanomas.

Angiogenesis Inducing Agents↗
PubMed2000

Mesalazine changes apoptosis and proliferation in normal mucosa of patients with sporadic polyps of the large bowel.

BACKGROUND AND STUDY AIMS: Regular intake of nonsteroidal anti-inflammatory drugs (NSAIDs) may reduce the occurrence of colorectal adenoma and carcinoma, possibly by inducing apoptosis and/or decreasing proliferation in colorectal epithelial cells. Mesalazine is widely used in the treatment of patients with inflammatory bowel disease, and well tolerated. We investigated its effect on apoptosis and proliferation of colorectal mucosa in 21 patients with sporadic polyps of the large bowel. PATIENTS AND METHODS: In total, 17 patients with sporadic colorectal polyps (> or = 5 mm) underwent polypectomy and biopsy of uninvolved mucosa before and after treatment with 1 g/d mesalazine for 1, 3, 7 or 14 days. Four additional patients served as untreated controls. Apoptotic index (AI) was measured by terminal deoxynucleotidyl transferase-mediated d-uridine triphosphate nick-end labeling (TUNEL) assay; proliferation index (PI) was measured by immunohistochemical examination with anti-Ki67 antibody. RESULTS: AI was significantly increased 1 and 3 days after initiation of treatment with mesalazine compared with controls (P= 0.0107 for the 1-day treatment group and P=0.0142 for the 3-day treatment group), and seemed to remain largely unchanged after longer treatment duration. Proliferation appeared to be decreased by mesalazine in all treatment groups, while proliferation in controls did not change (P=0.0107 for the 1-day treatment group and P= 0.0142 for the 3-day treatment group compared with controls. CONCLUSIONS: Mesalazine significantly induces apoptosis and decreases proliferation in colorectal mucosa in patients with sporadic polyps of the large bowel. This may be clinically relevant in that it may lower the rate of polyp recurrence after polypectomy, thereby possibly contributing to the chemoprevention of sporadic colorectal carcinoma.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Lack of germline mutations in the preproglucagon gene region coding for glucagon-like peptide 1 in Type 2 diabetic (NIDDM) patients.

Glucagon-like peptide 1 (GLP-1) has antidiabetic effects and many facets of Type 2 diabetes could theoretically be the consequence of a reduction in or lack of GLP-1 function. Exogenous GLP-1 is exquisitely effective in Type 2 diabetic patients, making receptor defects unlikely. GLP-1 responses after meals as detected by radioimmunoassay are not overtly reduced in Type 2 diabetic patients. Therefore, a sequence analysis of exon 2 of the preproglucagon gene coding for the GLP-1 protein was initiated in order to exclude potential germline mutations. 24 Type 2 diabetic patients and in 14 control subjects with normal oral glucose tolerance (WHO criteria) were studied. In all specimens of peripheral blood leukocyte DNA examined, no germline mutations of the GLP-1 sequence were identified, thus excluding mutations in the GLP-1 sequence as a major contributor to the pathophysiological appearance of the Type 2 diabetic phenotype. Rare mutations, however, cannot be excluded due to the small number of Type 2 diabetic patients examined.

Aged↗
PubMed2000

The nonfunctional allele TCRBV6S1B is strongly associated with Helicobacter pylori infection.

To determine genetic susceptibility factors for Helicobacter pylori infection, polymorphic T-cell receptor gene elements were investigated in 203 H. pylori-infected individuals and 180 uninfected individuals (controls). H. pylori infection is highly associated with individuals homozygous for the nonfunctional TCRBV6S1B element (odds ratio = 5.9; chi(2) = 13; P = 0.00032; P value corrected for multiple comparisons [Bonferroni correction] = 0. 00063).

Alleles↗
PubMed2000

Neoadjuvant, hyperfractionated irradiation induces apoptosis and decreases proliferation in squamous cell cancer of the oral cavity.

Twenty-eight patients with squamous cell carcinoma of the oral cavity were treated with a total dose of 20 Gy. Tissue samples for immunohistochemistry were taken at the time of diagnostic biopsy and at surgery after radiotherapy (RX). For detection of proliferating cells, the immunoperoxidase reaction with Ki67 was performed. Apoptotic cells were detected by the TdT-mediated biotin dUTP nick end labeling (TUNEL) method. RX reduced proliferation in 27 patients, only in one case did the proliferation index (PI) increase. Delta PI (PI before RX PI following RX) amounted to 4.11% (SD=3.2%; P<0.0001). The apoptotic index (AI) increased significantly subsequent to neoadjuvant RX. Delta AI (AI after RX--AI before RX) measured 1.82% (SD=0.9; P<0.001). These data indicate that RX of patients suffering from squamous cell carcinoma of the oral cavity with a dosis of 20 Gy induces apoptosis and inhibits proliferation of tumor cells.

Adult↗
PubMed1999

Hollow-spheres: a new model for analyses of differentiation of pancreatic duct epithelial cells.

We discovered a unique feature of a subclone of the pancreatic carcinoma cell line A818. A818-1-derived hollow-spheres developed under three-dimensional growth conditions. Hollow-spheres consist of a single layer of 50-200 epithelial cells surrounding an inner lumen. In contrast to A818-1, the subclone A818-4 and all other pancreatic tumor cell lines tested (n = 5), formed spheroids as the only three-dimensional phenotype. A dramatically reduced proliferation rate compared to the corresponding monolayer was observed in hollow-spheres when bromodeoxyuridine (BrdU) incorporation was measured. This finding was confirmed by immunostaining using the MIB-1 antibody. Mechanically disrupted hollow-spheres not only attached but also grew as monolayer with the same doubling time as the founder cells. Hollow-spheres developed in fetal calf serum (FCS) containing RPMI 1640 medium without additionally added cytokines. A818-1 hollow-sphere formation and integrity was influenced by interferon-gamma. Tumor necrosis factor-alpha (TNF-alpha) led to cell death. Exogenously added hepatocyte growth factor (HGF) showed no effect neither on hollow-sphere formation nor on the integrity of completely developed hollow-spheres. Moreover, no changes were observed when cells were treated with a neutralizing antibody for HGF. Interestingly, hollow-spheres showed intensive immunoreactivity for the HGF-receptor (c-met) and its ligand (HGF). Immunostaining for the biliary glycoprotein (BGP), the non-specific cross-reacting antigen 95 (NCA95) and beta-catenin revealed a polar organization of hollow-spheres. Immunhistochemically, hollow-spheres were negative for the carcinoembryonic antigen (CEA). When hollow-spheres were embedded into matrigel, duct-like tubes grew out. Taken together, A818-1 hollow-spheres resemble normally differentiated duct-like structures and will serve as an excellent model to study differentiation of human pancreatic epithelial cells.

Aged↗
PubMed1999

DPC4/SMAD4 mediated tumor suppression of colon carcinoma cells is associated with reduced urokinase expression.

We recently identified DPC4/Smad4 as a candidate tumor suppressor gene mutated or lost in one half of pancreatic carcinomas and in a subset of colon and biliary tract carcinomas. DPC4 plays a key role in signal transduction of the TGF-beta superfamily of molecules and inactivation of TGF-beta mediated growth inhibition is supposed to be the driving force for DPC4 inactivation in human tumors. However, DPC4 mediated tumor suppression by reconstitution of defective cells has not yet been reported. Here we show suppression of tumorigenicity in nude mice by stable reexpression of DPC4 in SW480 colon carcinoma cells. In vitro growth of DPC4-transfected cells was not affected and resistance towards TGF-beta mediated growth inhibition was retained. Instead, cells exhibited morphological alterations and adhesion and spreading were accelerated. These phenotypic changes were associated with reduced expression levels of the endogenous urokinase-type plasminogen activator (uPA) and plasminogen-activator-inhibitor-1 (PAI-1) genes, the products of which are implicated in the control of cell adhesion and invasion. In patients, high expression levels of uPA and PAI-1 correlate with poor prognosis. Thus, reduced expression of uPA and PAI-1 is consistent with suppression of tumorigenicity in DPC4 reconstituted cells. These results demonstrate DPC4's tumor suppressive function and suggest a potential role for DPC4 as a modulator of cell adhesion and invasion.

Animals↗
PubMed1999

Mutations of the DPC4/Smad4 gene in neuroendocrine pancreatic tumors.

Tumors of the endocrine pancreas are extremely rare, and molecular mechanisms leading to their development are not well understood. A candidate tumor suppressor gene, DPC4, located at 18q21, has recently been shown to be inactivated in half of pancreatic adenocarcinoma xenografts. The close anatomical relationship of the exocrine and endocrine pancreas prompted us to determine the role of DPC4 in the tumorigenesis of 25 pancreatic islet cell tumors (11 insulinomas, nine non-functioning endocrine carcinomas, three gastrinomas, two vipomas). A mutation screening of the highly conserved COOH-terminal domain of DPC4 (exons 8-11) was performed by single-strand conformational variant (SSCP) analysis and a PCR-based deletion assay. Five of nine (55%) non-functioning endocrine pancreatic carcinomas revealed either point mutations, small intragenic deletions or homozygous deletion of DPC4 sequences compared to none of the insulinomas, gastrinomas or vipomas. These results suggest that DPC4 is an important target gene promoting tumorigenesis of non-functioning neuroendocrine pancreatic carcinomas.

Adenoma, Islet Cell↗
PubMed1999

Helicobacter pylori infection and polymorphisms in the tumor necrosis factor region.

Twin studies evidence that genetic factors of the host influence the acquisition and the clinical outcome of Helicobacter pylori infections in addition to bacterial and environmental factors. In the tumor necrosis factor (TNF) alpha-gene, allelic frequencies of the polymorphic microsatellite TNFa and the promoter polymorphism TNF-308 were studied for 209 H. pylori+ patients and compared to 184 H. pylori- controls. In the H. pylori+ group 34 individuals suffered from duodenal ulcer and 45 from gastric ulcer. Genotyping of the TNFa microsatellite and TNF-308 polymorphisms was performed after polymerase chain reaction by polyacrylamide gel electrophoresis (PAGE) and allele-specific oligonucleotide hybridizations, respectively. The phenotype frequency of microsatellite allele TNFa6 was lower in the H. pylori+ females as well as infected females with gastric ulcer compared to uninfected controls. Infected men with duodenal ulcer had a decreased frequency of allele TNFa10. The genotype TNF1/TNF1 of the polymorphism TNF-308 is a risk factor for duodenal ulcer in H. pylori+ females; p = 0.01; relative risk (RR) = 10.7; corrected p-value (Pc) = 0.05. Thus, the TNF region is crucial in the complex genetic predisposition for H. pylori infection for certain patient subgroups.

Adolescent↗
PubMed1999

Serum levels of vascular endothelial growth factor and basic fibroblast growth factor in patients with soft-tissue sarcoma.

PURPOSE: Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have been suggested to be important mediators for tumor-induced angiogenesis. We measured serum VEGF and bFGF levels from patients with soft-tissue sarcomas and correlated serum VEGF and bFGF levels with tumor status at surgery and histological grading. MATERIALS AND METHODS: A group of 18 healthy controls and 85 patients with soft-tissue sarcoma were enrolled in this study. The patients were classified according to tumor status at surgery. Serum levels of VEGF and bFGF were also correlated with histological grading. VEGF and bFGF levels were determined by enzyme-linked immunosorbent assay (Quantikine R&D Systems). RESULTS: Serum VEGF and bFGF levels were significantly elevated in the patient group (VEGF: 580pg/ml, bFbF: 21pg/ml, P = 0.0001). The highest concentrations of serum VEGF and bFGF were found in patients with macroscopic tumor lesions or G3 histology. Serum VEGF levels showed a statistically significant correlation with tumor status and grading (P = 0.006 for tumor status, P = 0.0001 for grading). CONCLUSIONS: This study reveals that elevated preoperative serum VEGF and bFGF levels can be detected in the majority of patients with soft-tissue sarcoma. The significant correlation with tumor mass and histological grading suggests that a consecutive monitoring of VEGF and bFGF in the serum of patients with soft-tissue sarcoma might be a valuable marker for tumor follow-up.

Biomarkers, Tumor↗
PubMed1999

Melanoma-associated expression of vascular endothelial growth factor and its receptors FLT-1 and KDR.

The expression patterns of vascular endothelial growth factor (VEGF) and its two receptors, flt-1 and KDR, were assessed in normal human melanocytes, transformed melanocytes expressing the simian virus 40 Tgene (SV40T), and melanoma cells derived from primary and metastatic lesions. Constitutive expression of VEGF, flt-1, and KDR mRNA and proteins was observed in the majority of primary and metastatic melanoma cell lines, and in SV40T-transformed melanocytes. VEGF expression in melanoma cell lines was further enhanced by exogenous growth factors including insulin and fetal calf serum. By contrast, neonatal melanocytes did not express VEGF or VEGF receptors and VEGF expression could not be induced by exogenous growth factors. Exogenous VEGF had no significant effects on melanoma cell proliferation or on production of a transcriptional target for VEGF, urokinase-type plasminogen activator. Down-regulation of VEGF expression in the metastatic melanoma cell line WM164 through transfection of a VEGF antisense construct similarly did not affect proliferation of the transfected cells in the presence or absence of exogenous VEGF. In summary, coexpression of VEGF and its receptors is a tumor-associated phenomenon in melanoma development. However VEGF production does not support autocrine proliferation of the melanoma cell lines tested.

Antibody Specificity↗