Residual tumor cells are unique cellular targets in glioblastoma.

Residual tumor cells remain beyond the margins of every glioblastoma (GBM) resection. Their resistance to postsurgical therapy is considered a major driving force of mortality, but their biology remains largely uncharacterized. In this study, residual tumor cells were derived via experimental biopsy of the resection margin after standard neurosurgery for direct comparison with samples from the routinely resected tumor tissue. In vitro analysis of proliferation, invasion, stem cell qualities, GBM-typical antigens, genotypes, and in vitro drug and irradiation challenge studies revealed these cells as unique entities. Our findings suggest a need for characterization of residual tumor cells to optimize diagnosis and treatment of GBM.

CXCL16 is expressed in podocytes and acts as a scavenger receptor for oxidized low-density lipoprotein.

Podocytes are a crucial cell type in the kidney and play an important role in the pathology of glomerular kidney diseases like membranous nephropathy (MN). The identification of new factors involved in the progression of glomerular kidney diseases is of great importance to the development of new strategies for the treatment of renal injury. Here we demonstrate that CXCL16 and ADAM10 are constitutively expressed in human podocytes in normal renal tissue. Proinflammatory cytokines like interferon-gamma and tumor necrosis factor-alpha induced the expression of cellular CXCL16 and the release of its soluble form from human podocytes. Using different metalloproteinase inhibitors, we provide evidence that ADAM10 is involved in the interferon-gamma- and tumor necrosis factor-alpha-induced shedding of CXCL16 from human podocytes. In addition, ADAM10 knockdown by siRNA significantly increased both CXCL16 levels and, surprisingly, its ADAM17-mediated release. Notably, targeting of CXCL16 in human podocytes both decreased the chemotaxis of CXCR6-expressing T cells and strongly reduced oxidized low-density lipoprotein uptake in human podocytes. Importantly, in kidney biopsies of patients with MN, increased glomerular CXCL16 expression was accompanied by high levels of oxidized low-density lipoprotein and decreased expression of ADAM10. In addition, we found increased glomerular ADAM17 expression in patients diagnosed with MN. In summary, we presume important roles for CXCL16, ADAM10, and ADAM17 in the development of MN, suggesting these proteins as new therapeutic targets in this glomerular kidney disease.

ADAM10 is expressed in human podocytes and found in urinary vesicles of patients with glomerular kidney diseases.

BACKGROUND: The importance of the Notch signaling in the development of glomerular diseases has been recently described. Therefore we analyzed in podocytes the expression and activity of ADAM10, one important component of the Notch signaling complex. METHODS: By Western blot, immunofluorescence and immunohistochemistry analysis we characterized the expression of ADAM10 in human podocytes, human urine and human renal tissue. RESULTS: We present evidence, that differentiated human podocytes possessed increased amounts of mature ADAM10 and released elevated levels of L1 adhesion molecule, one well known substrate of ADAM10. By using specific siRNA and metalloproteinase inhibitors we demonstrate that ADAM10 is involved in the cleavage of L1 in human podocytes. Injury of podocytes enhanced the ADAM10 mediated cleavage of L1. In addition, we detected ADAM10 in urinary podocytes from patients with kidney diseases and in tissue sections of normal human kidney. Finally, we found elevated levels of ADAM10 in urinary vesicles of patients with glomerular kidney diseases. CONCLUSIONS: The activity of ADAM10 in human podocytes may play an important role in the development of glomerular kidney diseases.

CXCL16 and oxLDL are induced in the onset of diabetic nephropathy.

Diabetic nephropathy (DN) is a major cause of end-stage renal failure worldwide. Oxidative stress has been reported to be a major culprit of the disease and increased oxidized low density lipoprotein (oxLDL) immune complexes were found in patients with DN. In this study we present evidence, that CXCL16 is the main receptor in human podocytes mediating the uptake of oxLDL. In contrast, in primary tubular cells CD36 was mainly involved in the uptake of oxLDL. We further demonstrate that oxLDL down-regulated alpha(3)-integrin expression and increased the production of fibronectin in human podocytes. In addition, oxLDL uptake induced the production of reactive oxygen species (ROS) in human podocytes. Inhibition of oxLDL uptake by CXCL16 blocking antibodies abrogated the fibronectin and ROS production and restored alpha(3) integrin expression in human podocytes. Furthermore we present evidence that hyperglycaemic conditions increased CXCL16 and reduced ADAM10 expression in podocytes. Importantly, in streptozotocin-induced diabetic mice an early induction of CXCL16 was accompanied by higher levels of oxLDL. Finally immunofluorescence analysis in biopsies of patients with DN revealed increased glomerular CXCL16 expression, which was paralleled by high levels of oxLDL. In summary, regulation of CXCL16, ADAM10 and oxLDL expression may be an early event in the onset of DN and therefore all three proteins may represent potential new targets for diagnosis and therapeutic intervention in DN.

Downregulation of junctional adhesion molecule-A is involved in the progression of clear cell renal cell carcinoma.

Junctional adhesion molecule-A (JAM-A) is one component of tight junctions which are involved in important processes like paracellular permeability, cell polarity, adhesion, migration, and angiogenesis. Here we describe JAM-A expression in distal convoluted tubule, connecting tubule, and in cells of the collecting duct of the healthy human kidney. In addition, JAM-A was weakly expressed in cells of the proximal tubule. Using immunofluorescence, FACS and Western blot analysis we investigated JAM-A expression in tubular cells in vitro. Interestingly, treatment of HK-2 cells with IFN-gamma and TNF-alpha resulted in a metalloproteinase mediated downregulation of JAM-A. Importantly, in a tissue micro-array JAM-A protein expression was significantly downregulated in patients with clear cell renal cell carcinoma. Furthermore, knockdown of JAM-A with JAM-A specific siRNA induced the migration of RCC4 cells. In summary, downregulation of JAM-A is an early event in the development of renal cancer and increases the migration of renal cancer cells.

Characterization of CXCL16 and ADAM10 in the normal and transplanted kidney.

The chemokine CXCL16 plays an important role in the recruitment of leukocytes to sites of inflammation influencing the course of experimental glomerulonephritis. Here we show that human kidneys highly express CXCL16 in the distal tubule, connecting tubule and principal cells of the collecting duct with weak expression in the thick ascending limb of Henle. Beside the membrane localization, a soluble form of CXCL16 can be proteolytically released which acts as a chemotactic factor. In human renal tissue the expression pattern of the disintegrin-like metalloproteinase ADAM10 is similar to that of CXCL16, suggesting ADAM10 can potentially cleave CXCL16 in vivo. When we tested this in primary tubular cells we found that blockade of ADAM10 activity inhibited the IFN-gamma induced release of soluble CXCL16. Acute tubular damage in renal allografts was associated with elevated urinary CXCL16 and this correlated with focally increased apical CXCL16 expression in the distal tubules and collecting ducts. Renal allograft biopsies, with a histopathological diagnosis of acute interstitial rejection, showed increased basolateral ADAM10 expression together with high numbers of infiltrating T cells. Our results suggest that CXCL16 and ADAM10 are involved in the recruitment of T cells to the kidney and play an important role in inflammatory kidney diseases.

The role of CXCL16 and its processing metalloproteinases ADAM10 and ADAM17 in the proliferation and migration of human mesangial cells.

In this study, we analyzed the regulation and functional role of CXCL16 in human mesangial cells (hMCs). We can show, that CXCL16 is constitutively expressed in hMCs and is further up-regulated by cytokine mix (IFNgamma, TNFalpha, and IL1beta). The constitutive release of CXCL16 from hMCs was rapidly induced by the stimulation with cytokines. We identified ADAM10 and ADAM17 as being responsible for the cytokine-induced shedding of CXCL16. Notably, targeting ADAM10 and ADAM17 in hMCs decreased the chemotaxis of T-Jurkat cells, whereas the inhibition of CXCL16 had no significant influence. This suggests that both proteases are important players in the recruitment of immune cells into the glomerulus, but other substrates than CXCL16 are involved in this process. Finally, we could show that the inhibition of CXCL16, ADAM10, and ADAM17 led to a strong reduction of cell proliferation and migration of hMCs. This finding could be important to develop novel diagnostic and therapeutic strategies to treat mesangial proliferative kidney diseases.

Oncogenic signaling pathways and deregulated target genes.

A limited number of somatic mutations are known to trigger malignancy via chronic activation of cellular signaling pathways. High-throughput analysis of gene expression in cancer cells has revealed a plethora of deregulated genes by far exceeding the number of known genetic alterations. Targeted tumor therapy takes advantage of deregulated signaling in cancer. However, cancer cells may evade successful therapy, e.g., targeting oncogenic kinases, due to mutation of the target protein or to resistance mechanisms acting downstream of or parallel to the therapeutic block. To improve therapy and molecular diagnostics, we need detailed information on the wiring of pathway components and targets that ultimately execute the malignant properties of advanced tumors. Here we review work on Ras-mediated signal transduction and Ras pathway-responsive targets. We introduce the concept of signal-regulated transcriptional modules comprising groups of target genes responding to individual branches of the pathway network. Furthermore, we discuss functional approaches based on RNA interference for elucidating critical nodes in oncogenic signaling and the targets essential for malignancy.

Transcriptional basis of KRAS oncogene-mediated cellular transformation in ovarian epithelial cells.

To understand the relationship between oncogenic signaling and the reprogramming of gene expression, we performed transcriptional profiling in rat ovarian surface epithelial cells (ROSE), in which neoplastic transformation is driven by a mutated KRAS oncogene. We identified >200 genes whose expression was elevated or reduced following permanent KRAS expression. Deregulated KRAS-responsive genes encode transcriptional regulators, signaling effectors, proteases, extracellular matrix and adhesion proteins, transformation-suppressing proteins and negative growth regulators. Many of them have not been previously identified in cells expressing oncogenic RAS genes or in other well-studied models of oncogenic signaling. The number of critical genes related to the execution of anchorage-independent proliferation and epithelial-mesenchymal transition was narrowed down to 79 by selectively inhibiting the mitogen-activated protein kinase (MAPK/ERK) and phosphatidylinositol 3-kinase (PI3K) pathways. Blocking MAPK/ERK-signaling caused reversion to the normal epithelial phenotype in conjunction with the reversal of deregulated target transcription to pretransformation levels. In addition, silencing of the overexpressed transcriptional regulator Fra-1 by RNA interference resulted in growth reduction, suggesting that this factor partially contributes to, but is not sufficient for the proliferative capacity of KRAS-transformed epithelial cells.

Intraperitoneal dissemination of Ad12-induced undifferentiated neuroectodermal hamster tumors: de novo methylation and transcription patterns of integrated viral and of cellular genes.

The intramuscular (i.m.) injection of human adenovirus type 12 (Ad12) into newborn Syrian hamsters caused widespread dissemination of up to 15 tumors over the entire peritoneal cavity in 70-90% of the animals within 30-50 days. Subcutaneous (s.c.) injections led to local tumor formation only. Independent of location, tumor histology revealed Homer-Wright rosette-like structures typical for primitive neuroectodermal tumors (PNET). All tumor cells showed markers indicative of neuroectodermal and mesenchymal derivations. Each Ad12-induced tumor cell carried multiple copies of integrated Ad12 genomes at one chromosomal site which was different for each tumor. For Ad12 tumor induction in hamsters, the patterns of Ad12 viral and cellular gene expression were important and were affected by changes in DNA methylation, both in the integrated Ad12 DNA and the cellular genome. By applying the bisulfite protocol, the de novo DNA methylation in the integrated Ad12 genomes was determined. These patterns were complex, characterized by regional initiation and by excluding genome segments in the E1A and E1B promoters. In all tumors, the Ad12 segments E1A, E1B, E2A, parts of E3 and E4 were similarly transcribed, as shown by the RT-PCR and DNA microarray methods. Changes in the transcription of a large number of cellular genes was assessed by using mouse gene microarrays encompassing about 1980 different mouse genes with 87-96% homology to hamster genes. Similarities and differences existed in the transcription of cellular genes of different functional classes among the different Ad12-induced tumors. These alterations in cellular gene transcription may be an important parameter in the oncogenic transformation by Ad12.

ADAM10 is upregulated in melanoma metastasis compared with primary melanoma.

ADAM10 (a disintegrin and metalloproteinase 10) is involved in the ectodomain shedding of various substrates, including adhesion molecules such as L1 cell adhesion molecule (L1-CAM) and CD44, which are known to have important roles in the development of malignant melanoma. In our study, we characterized the expression of ADAM10 in melanoma cells in vitro and in vivo. Immunohistochemical analysis on tissue microarrays indicated that ADAM10 expression was significantly elevated in melanoma metastasis compared with primary melanomas. In vitro downregulation of ADAM10 with specific small interfering RNA (siRNA) resulted in a suppression of the anchorage-independent cell growth and reduced the migration of melanoma cells. In addition, overexpression of ADAM10 induced the migration of melanoma cells. In cell lines from melanoma patients with metastasis, ADAM10 was significantly overexpressed, and ADAM10 expression correlated with increased cell proliferation. Furthermore, we present evidence that ADAM10 is involved in the release of L1-CAM from melanoma cells. It is important that knockdown of cellular L1-CAM reduced the migration of melanoma cells and abrogated the chemoresistance against cisplatin. In contrast, soluble L1-CAM had no effect on melanoma cell migration or cell survival. Taken together, our data demonstrate that ADAM10 and L1-CAM have important roles during melanoma progression and both molecules represent attractive targets for therapeutical intervention of melanomas.

Overexpression of CXCL16 in lesional psoriatic skin.

BACKGROUND: Psoriasis is characterized as an autoimmune disease resulting in an exaggerated innate immune response. The CXC-chemokine ligand 16 (CXCL16) is described to function as an adhesion molecule, a scavenger receptor or as a soluble molecule it acts as a chemoattractant. CXCL16 has been reported to be expressed in a variety of inflammatory diseases. However, no information has been reported in the literature about the expression of CXCL16 in psoriatic skin. PURPOSE: The present study was designed to analyze the expression and localization of CXCL16 in human psoriatic skin tissues. RESULTS: In normal skin, cytpoplasmic expression of CXCL16 was increased in keratinocytes of upper epidermal cell layers as compared to the lower epidermal cell layers. In lesional psoriatic skin, CXCL16 immunoreactivity was increased in the cytoplasm of keratinocytes of lower epidermal layer kerartinocytes as compared to the normal epidermis. Cytoplasmic CXCL16 expression was increased in the capillary endothelial cells of psoriatic dermis as compared to capillary endothelial cells of the normal dermis. Notably, almost all inflammatory cells in the dermis were negative for CXCL16. MATERIALS AND METHODS: Ten paraffinized specimens of human lesional psoriatic skin and five paraffinized specimens of normal skin were studied using an immunohistochemical streptavidinperoxidase technique. CONCLUSION: We here report for the first time alterations in the immunohistochemical staining pattern of CXCL16 in lesional psoriatic skin compared to the normal skin. These results suggest that CXCL16 may play a role in the pathogenesis of psoriasis.

Hair-cycle dependent differential expression of ADAM 10 and ADAM 12: An immunohistochemical analysis in human hair follicles in situ.

BACKGROUND: ADAM proteases play important roles in processes of development and differentiation. However, no report has been found in the literature addressing the expression and function of ADAM proteases during hair cycling. RESULTS: Cytoplasmic expression pattern of ADAM 10, 12 was similar between normal epidermis and hair infundibulum. In addition, cytoplasmic expression of ADAM 10 was observed in the hair bulb keratinocytes and fibroblasts of dermal papilla in anagen I-III hair follicles. In contrast, decreased ADAM 10 expression was observed in the hair matrix keratinocytes as compared to the hair bulb keratinocytes in anagen I-III hair follicles. Interestingly, ADAM 10 immunoreactivity was expressed weakly in the lower portion of outer root sheath (ORS) of anagen VI hair follicles, and strong ADAM 10 expression was detected in the ORS of catagen and telogen hair follicles. By contrast, ADAM 12 expression was not detected in the hair bulb keratinocytes of anagen I-III hair follicles. ADAM 12 immunoreactivity firstly appeared in the inner root sheath ( IRS ) of anagen IV-V hair follicles and was down-regulated in the IRS and hair cortex and medulla of catagen hair follicles, Strong ADAM 12 immunoreactivity was observed in the ORS of catagen and telogen hair follicles. MATERIAL AND METHODS: Samples of normal human skin (n = 30) were used. Immunohistochemical analysis was performed using ADAM 10, 12 specific polyclonal antibodies and a sensitive streptavidin-peroxidase technique. CONCLUSION: Our study demonstrates a comparable staining pattern of decreased ADAM 10 immunoreactivity in hair matrix keratinocytes and the basal cell layer of normal epidermis and hair infundibulum. Expression of ADAM 10 in dermal papilla cells may imply a role in the induction and development of anagen hair follicles. In addition, expression of ADAM 10 in the ORS and hair bulb assume the involvment of ADAM 10 in the downward migration of anagen hair follicles. Furthermore ADAM 12 expression in the IRS may indicate a role in the differentiation of anagen hair follicles. Downregulation of ADAM 12 upon the onset of catagen hair stage suggests that ADAM 12 may play an important role of ADAM 12 in the apoptosis of hair follicle keratinocytes. In summary our findings suggest that ADAM 10 and 12 may be of importance for the regulation of hair cycling.

A systems biological approach suggests that transcriptional feedback regulation by dual-specificity phosphatase 6 shapes extracellular signal-related kinase activity in RAS-transformed fibroblasts.

Mitogen-activated protein kinase (MAPK) signaling determines crucial cell fate decisions in most cell types, and mediates cellular transformation in many types of cancer. The activity of MAPK is controlled by reversible phosphorylation, and the quantitative characteristics of MAPK activation determine the cellular response. Many systems biological studies have analyzed the activation kinetics and the dose-response behavior of the MAPK signaling pathway. Here we investigate how the pathway activity is controlled by transcriptional feedback loops. Initially, we predict that MAPK signaling regulates phosphatases, by integrating promoter sequence data and ontology-based classification of gene function. From this, we deduce that MAPK signaling might be controlled by transcriptional negative feedback regulation via dual-specificity phosphatases (DUSPs), and implement a mathematical model to further test this hypothesis. Using time-resolved measurements of pathway activity and gene expression, we employ a model selection approach, and select DUSP6 as a highly likely candidate for shaping the activity of the MAPK pathway during cellular transformation caused by oncogenic RAS. Two predictions from the model were confirmed: first, feedback regulation requires that DUSP6 mRNA and protein are unstable; and second, the activation kinetics of MAPK are ultrasensitive. Taken together, an integrated systems biological approach reveals that transcriptional negative feedback controls the kinetics and the extent of MAPK activation under both physiological and pathological conditions.

Tumoural CXCL16 expression is a novel prognostic marker of longer survival times in renal cell cancer patients.

The aim of our study was to analyse the expression of CXCL16, ADAM10 and CXCR6 in renal cell carcinoma (RCC) tissue and to correlate the expression pattern with clinicopathologic data, including patient survival. Furthermore, we investigated CXCL16, ADAM10 and CXCR6 expressions by FACS, immunofluorescence and ELISA analysis in renal carcinoma cell lines. Our immunohistochemical analysis on tissue microarray of renal cancer samples of 104 patients revealed that ADAM10 correlated significantly with tumour stage, pathological nodal status, M status and lymphangiosis carcinomatosa. CXCL16, CXCR6 and ADAM10 were significantly increased in papillary carcinomas. Importantly, high levels of CXCL16 expression in renal cancer tissue correlated with better survival of patients, and CXCL16 correlated inversely to the tumour stage. In addition, inhibition of CXCL16 induced the migration of renal cancer cells assuming an anti-migratory function of transmembrane CXCL16. Taken together, our data demonstrate that downregulation of CXCL16 plays an important role in renal cancer development and progression, and that CXCL16 in RCC is an independent prognostic marker for better patient survival.