Biomedical subjects

Stephan C Schäfer

Publications and source records attributed to Stephan C Schäfer.

5 recordsLinked to original sources

PubMed2006

Expression of multiple epigenetically regulated cancer/germline genes in nonsmall cell lung cancer.

Cancer/germline (CG) antigens represent promising targets for widely applicable mono- and multiantigen cancer vaccines for nonsmall cell lung cancer (NSCLC). Since little is known about their composite expression in this tumor type, we analyzed 7 CG genes (MAGE-A3, NY-ESO-1, LAGE-1, BRDT, HOM-TES-85, TPX-1 and LDHC) in 102 human NSCLC specimens. About 81% of NSCLC express at least 1 and half of the specimen at least 2 CG genes. Activation of most of these genes occurs more frequently in squamous cell cancer than in adenocarcinomas. Even though we found all genes but one to be regulated by genomic methylation, not all of them are co-expressed. In particular, combining CG genes not localized on the X-chromosome may provide effective treatment for an extended number of patients.

Antigens, Neoplasm↗

PubMed2006

CD4+ CD25+ regulatory T cells suppress contact hypersensitivity reactions by blocking influx of effector T cells into inflamed tissue.

CD4+ CD25+ regulatory T cells (Treg) exert suppressive functions on effector T cells in vitro and in vivo. However, the exact cellular events that mediate this inhibitory action remain largely unclear. To elucidate these events, we used intravital microscopy in a model of contact hypersensitivity (CHS) and visualized the leukocyte-endothelium interaction at the site of antigen challenge in awake C57BL/6 mice. Injection of Treg i.v. into sensitized mice at the time of local hapten challenge significantly inhibited rolling and adhesion of endogenous leukocytes to the endothelium. A similar inhibition of leukocyte recruitment could be recorded after injection of Treg-derived tissue culture supernatant. Thus, these data indicate that soluble factors may account for the suppressive effects. Accordingly we found that IL-10, but not TGF-beta, was produced by Treg upon stimulation and that addition of anti-IL-10 antibodies abrogated the suppressive effects of Treg and tissue culture supernatant in CHS reactions. Moreover, CD4+ CD25+ T cells isolated from IL-10-/- mice were not able to suppress the immune response induced by hapten treatment in C57BL/6 mice. In conclusion, our data suggest that cytokine-dependent rather than cell-cell contact-dependent mechanisms play a pivotal role in the suppression of CHS reactions by Treg in vivo.

Animals↗

PubMed2005

Reduced expression of Hugl-1, the human homologue of Drosophila tumour suppressor gene lgl, contributes to progression of colorectal cancer.

The human gene, human giant larvae (Hugl-1/Llg1/Lgl1) has significant homology to the Drosophila tumour suppressor gene lethal(2)giant larvae (lgl). The lgl gene codes for a cortical cytoskeleton protein, Lgl, that binds Myosin II and is involved in maintaining cell polarity and epithelial integrity. The human protein, Hugl-1 contains several conserved functional domains found in Lgl, suggesting that these proteins may have closely related functions. Whether loss of Hugl expression plays a role in human tumorigenesis has so far not been extensively investigated. Thus, we evaluated tumour tissues from 94 patients undergoing surgery for colorectal cancer (CRC) for loss of Hugl-1 transcription and compared our findings with the clinical data from each of these patients. We found that Hugl-1 was lost in 75% of tumour samples and these losses were associated with advanced stage and particularly with lymph node metastases. Reduced Hugl-1 expression during the adenoma-carcinoma sequence occurring as early as in colorectal adenomas was detected by both immunohistochemical and reverse transcription-polymerase chain reaction analysis. Functional assays with ecdysone-inducible cell lines revealed that Hugl-1 expression increased cell adhesion and decreased cell migration. Our studies thus indicate that downregulation of Hugl-1 contributes to CRC progression.

Adenoma↗

PubMed2005

Midostaurin upregulates eNOS gene expression and preserves eNOS function in the microcirculation of the mouse.

Nitric oxide (NO) derived from endothelial NO synthase (eNOS) is a powerful vasodilator and possesses vasoprotective effects. Therefore, augmentation of eNOS expression and -activity by pharmacological means could provide protection against cardiovascular disease. However, this concept has been questioned recently, because in several disease models, eNOS upregulation was associated with a dysfunctional enzyme (referred to as eNOS uncoupling). In contrast, the present study demonstrates that an eNOS gene expression-enhancing compound with additional protein kinase C (PKC) inhibitory properties can upregulate eNOS while preserving its enzymatic function. Apolipoprotein E-knockout mice were treated for 7 days with midostaurin (4'-N-benzoyl staurosporine, compound CGP 41251, 50-125 mg/kg/day), a PKC inhibitor previously shown to increase eNOS expression and NO production in cultured human endothelial cells. Midostaurin treatment enhanced eNOS mRNA expression (RNase protection assay) in mouse aorta, kidney, and heart in a dose-dependent fashion. In the dorsal skinfold microcirculation, midostaurin produced an arteriolar vasorelaxation (intravital microscopy), which could be prevented by the NOS inhibitor L-NAME, indicating that the upregulated eNOS remained functional. In organ chamber experiments, the aorta from midostaurin-treated mice showed an enhanced NO-mediated relaxation in response to acetylcholine. Accordingly, serum levels of nitrite/nitrate (NO-Analyzer) were increased, and the production of reactive oxygen species in the aorta (L-012 chemiluminescence) was reduced by midostaurin. Thus, in mice in vivo, midostaurin treatment results in enhanced expression of eNOS with preserved enzyme function and enhanced production of bioactive NO. Given the beneficial effects of endothelial-derived NO, vasoprotective and anti-atherosclerotic effects are likely to ensue.

Animals↗

PubMed2005

Paradoxical attenuation of leukocyte rolling in response to ischemia- reperfusion and extracorporeal blood circulation in inflamed tissue.

In contrast to acute preparations such as the exteriorized mesentery or the cremaster muscle, chronically instrumented chamber models allow one to study the microcirculation under "physiological" conditions, i.e., in the absence of trauma-induced leukocyte rolling along the venular endothelium. To underscore the importance of studying the naive microcirculation, we implanted titanium dorsal skinfold chambers in hamsters and used intravital fluorescence microscopy to study venular leukocyte rolling in response to ischemia-reperfusion injury or extracorporeal blood circulation. The experiments were performed in chambers that fulfilled all well-established criteria for a physiological microcirculation as well as in chambers that showed various extents of leukocyte rolling due to trauma, hemorrhage, or inflammation. In ideal chambers with a physiological microcirculation (<30 rolling leukocytes/mm vessel circumference in 30 s), ischemia-reperfusion injury and extracorporeal blood circulation significantly stimulated leukocyte rolling along the venular endothelium and, subsequently, firm leukocyte adhesion. In contrast, both stimuli failed to elicit leukocyte rolling in borderline chambers (30-100 leukocytes/mm), and in blatantly inflamed chambers with yet higher numbers of rolling leukocytes at baseline (>100 leukocytes/mm), we observed a paradoxical reduction of leukocyte rolling after ischemia-reperfusion injury or extracorporeal blood circulation. A similar effect was observed when we superfused leukotriene B4 (LTB4) onto the chamber tissue. The initial increase in leukocyte rolling in response to an LTB4 challenge was reversed by a second superfusion 90 min later. These observations underscore 1) the benefit of studying leukocyte-endothelial cell interaction in chronically instrumented chamber models and 2) the necessity to strictly adhere to well-established criteria of a physiological microcirculation.

Animals↗