Biomedical subjects

Sander H Diks

Publications and source records attributed to Sander H Diks.

9 recordsLinked to original sources

PubMed2006

Comparison of kinome profiles of Barrett's esophagus with normal squamous esophagus and normal gastric cardia.

The precursor metaplastic mucosal lesion that predisposes for esophageal adenocarcinoma is Barrett's esophagus. Because the signal transduction events that occur in Barrett's esophagus are poorly understood, this study aimed at generating a comprehensive description of cellular kinase activity in Barrett's esophagus, normal squamous esophagus, and gastric cardia to gain more insight into the pathogenesis of Barrett's esophagus. Peptide arrays, exhibiting 1,176 specific consensus sequences for protein kinases, were used to produce a global analysis of cellular kinase activity in biopsies of Barrett's esophagus, and results were compared with the neighboring cardia and squamous epithelia. Several differences in kinase activity using immunoblot analysis and enzyme activity assays were validated in biopsies of 27 Barrett's esophagus patients. Three unique kinome profiles are described and compared. We identified cascades of activated kinases showing that mitogen-activated protein kinase and epidermal growth factor receptor activity are both significantly altered in Barrett's esophagus compared with squamous and gastric cardia epithelia. Another novel finding is that the glycolysis pathway is significantly up-regulated in Barrett's esophagus, which is illustrated by an up-regulated pyruvate kinase activity. Here, the unique kinome profile of Barrett's esophagus is made available as a comprehensive database. Several signaling pathways are revealed as specifically expressed in Barrett's esophagus when compared with the adjacent normal epithelia. These unique findings provide novel insight in the pathogenesis of Barrett's esophagus that will ultimately help to resolve the increasing problem of Barrett's esophagus and prevention of esophageal adenocarcinoma.

Adult↗

PubMed2006

The novel gene asb11: a regulator of the size of the neural progenitor compartment.

From a differential display designed to isolate genes that are down-regulated upon differentiation of the central nervous system in Danio rerio embryos, we isolated d-asb11 (ankyrin repeat and suppressor of cytokine signaling box-containing protein 11). Knockdown of the d-Asb11 protein altered the expression of neural precursor genes sox2 and sox3 and resulted in an initial relative increase in proneural cell numbers. This was reflected by neurogenin1 expansion followed by premature neuronal differentiation, as demonstrated by HuC labeling and resulting in reduced size of the definitive neuronal compartment. Forced misexpression of d-asb11 was capable of ectopically inducing sox2 while it diminished or entirely abolished neurogenesis. Overexpression of d-Asb11 in both a pluripotent and a neural-committed progenitor cell line resulted in the stimulus-induced inhibition of terminal neuronal differentiation and enhanced proliferation. We conclude that d-Asb11 is a novel regulator of the neuronal progenitor compartment size by maintaining the neural precursors in the proliferating undifferentiated state possibly through the control of SoxB1 transcription factors.

Amino Acid Sequence↗

PubMed2006

Protein phosphatase 2A is required for mesalazine-dependent inhibition of Wnt/beta-catenin pathway activity.

The rising incidence and poor prognosis of colorectal cancer have aroused substantial interest in novel chemopreventive strategies. Interestingly, treatment of ulcerative colitis with mesalazine, which displays few side effects during long-term treatment, is associated with a reduced incidence of colorectal cancer, but its molecular mechanism is not known. The effect of mesalazine on the Wnt/beta-catenin pathway was studied in colorectal cancer cell lines to find a molecular basis underlying its chemopreventive features. Mesalazine affects the Wnt/beta-catenin pathway in adenomatous polyposis coli mutated cells with intact beta-catenin, judged by luciferase reporter assays. Furthermore, mesalazine treatment reduced expression of nuclear beta-catenin and Wnt/beta-catenin target genes, and increased beta-catenin phosphorylation. This effect on the Wnt/beta-catenin pathway is mediated via protein phosphatase 2A (PP2A): increased phosphorylation of PP2A after mesalazine treatment is observed, which coincides with decreased PP2A enzymatic activity. The inhibition of PP2A enzymatic activity by mesalazine is essential for its effect on the Wnt/beta-catenin pathway, as shown by transient transfection with siPP2A and mutant PP2A. This study shows, using concentrations of mesalazine identical to concentrations seen in patients with inflammatory bowel disease, that mesalazine inhibits the Wnt/beta-catenin pathway via inhibition of PP2A.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2006

Tetrahydroxyquinone induces apoptosis of leukemia cells through diminished survival signaling.

OBJECTIVE: Tetrahydroxyquinone is a molecule best known as a primitive anticataract drug but is also a highly redox active molecule that can take part in a redox cycle with semiquinone radicals, leading to the formation of reactive oxygen species (ROS). Its potential as an anticancer drug has not been investigated. METHODS: The effects of tetrahydroxyquinone on HL60 leukemia cells are investigated using fluorescein-activated cell sorting-dependent detection of phosphatidylserine exposure combined with 7-amino-actinomycin D exclusion, via Western blotting using phosphospecific antibodies, and by transfection of constitutively active protein kinase B. RESULTS: We observe that in HL60 leukemia cells tetrahydroxyquinone causes ROS production followed by apoptosis through the mitochondrial pathway, whereas cellular physiology of normal human blood leukocytes was not affected by tetrahydroxyquinone. The antileukemic effect of tetrahydroxyquinone is accompanied by reduced activity of various antiapoptotic survival molecules including the protein kinase B pathway. Importantly, transfection of protein kinase B into HL60 cells and thus artificially increasing protein kinase B activity inhibits tetrahydroxyquinone-dependent cytotoxicity. CONCLUSION: Tetrahydroxyquinone provokes cytotoxic effects on leukemia cells by reduced protein kinase B-dependent survival signaling followed by apoptosis through the mitochondrial pathway. Thus, tetrahydroxyquinone may be representative of a novel class of chemotherapeutic drugs, inducing apoptosis in cancer cells through diminished survival signaling possibly as a consequence of ROS generation.

Apoptosis↗

PubMed2004

Kinome profiling for studying lipopolysaccharide signal transduction in human peripheral blood mononuclear cells.

The DNA array technique allows comprehensive analysis of the genome and transcriptome, but the high throughput array-based assessment of intracellular signal transduction remains troublesome. The goal of this study was to test a new peptide array technology for studying the activity of all kinases of whole cell lysates, the kinome. Cell lysates from human peripheral blood mononuclear cells before and after stimulation with lipopolysaccharide were used for in vitro phosphorylation with [gamma-33P]ATP arrays consisting of 192 peptides (substrates for kinases) spotted on glass. The usefulness of peptide arrays for studying signal transduction was demonstrated by the generation of the first comprehensive description of the temporal kinetics of phosphorylation events induced by lipopolysaccharide stimulation. Furthermore analysis of the signals obtained suggested activation of p21Ras by lipopolysaccharide, and this was confirmed by direct measurement of p21Ras GTP levels in lipopolysaccharide-stimulated human peripheral blood mononuclear cells, which represents the first direct demonstration of p21Ras activation by stimulation of a Toll receptor family member. Further confidence in the usefulness of peptide array technology for studying signal transduction came from Western blot analysis of lipopolysaccharide-stimulated cells, which corroborated the signals obtained using peptide arrays as well as from the demonstration that kinase inhibitors effected peptide array phosphorylation patterns consistent with the expected action of these inhibitors. We conclude that this first metabolic array is a useful method to determine the enzymatic activities of a large group of kinases, offering high throughput analysis of cellular metabolism and signal transduction.

Amino Acid Sequence↗

PubMed2004

FVIIa:TF induces cell survival via G12/G13-dependent Jak/STAT activation and BclXL production.

Tissue factor (TF), apart from activating the extrinsic pathway of the blood coagulation, is a principal regulator of embryonic and oncogenic angiogenesis, inflammation, leukocyte reverse transmigration, and tumor progression. It has become clear that these events are mediated by intracellular signal transduction elicited by TF/factor VIIa (FVIIa) interaction, but the details of this signaling remain largely obscure. In this study, we show that FVIIa/TF-interaction produces STAT5 phosphorylation, STAT5 nuclear translocation and transactivation of a STAT5 reporter construct. FVIIa-dependent STAT5 activation was dependent on FVIIa proteolytic activity but not on generation of the downstream coagulation factors Xa and thrombin, nor on the TF cytoplasmic domain. FVIIa-induced STAT5 phosphorylation was dependent on functional G12/G13 class G proteins and Jak2 activity, but not Jak1 or Tyk2. Finally, we show that FVIIa leads to cell survival through a Jak2/STAT5-dependent production of the antiapoptotic STAT5 target Bcl(XL) as well as Jak2-dependent activation of the antiapoptotic protein PKB. In conclusion, our results show that FVIIa induces cell survival through STAT5-dependent Bcl(XL) production and Jak2-dependent activation of PKB. Finally, we demonstrated for the first time that TF/FVIIa-signal transduction is dependent on G12/G13 class G proteins.

Active Transport, Cell Nucleus↗

PubMed2004

Single cell proteomics for personalised medicine.

Recently, multicolour FACS combined with phosphospecific antibodies has been developed, enabling the determination of the relative phosphorylation of signal transduction intermediates in individual cells. It has become clear that, when stimulated with cytokines, individual leukemia cells exhibit marked differences in phosphoprotein patterns and that these patterns correlate with disease outcome. Thus, single cell phosphoproteomic techniques might be superior to other proteomic approaches for the molecular diagnosis of disease and instrumental for the development of personalised medicine.

Antibodies, Phospho-Specific↗

PubMed2004

LPS signal transduction: the picture is becoming more complex.

Lipopolysaccharide (LPS) is the principal initiator of septic shock and it is to a large extent responsible for post-operative mortality. The use of antibiotics is still the most successful therapy against infection that may lead to sepsis and septic shock. With the advent of antibiotic resistant strains like MRSA the usefulness of conventional antibiotics is declining and new treatment strategies for LPS-mediated septic shock are called for. In this review we discuss the molecular mechanisms that are involved in the recognition of LPS and in the initiation of an immune response. Furthermore, we also review the recent insights in the signal transduction including receptor clustering and signalosome activation. Further insight into LPS-dependent signal transduction will assist the development of novel rational therapy.

Animals↗

PubMed2003

Activation of the canonical beta-catenin pathway by histamine.

Histamine signaling is a principal regulator in a variety of pathophysiological processes including inflammation, gastric acid secretion, neurotransmission, and tumor growth. We report that histamine stimulation causes transactivation of a T cell factor/beta-catenin-responsive construct in HeLa cells and in the SW-480 colon cell line, whereas histamine did not effect transactivation of a construct containing the mutated response construct FOP. On the protein level, histamine treatment increases phosphorylation of glycogen synthase kinase 3-beta in HeLa cells, murine macrophages, and DLD-1, HT-29, and SW-480 colon cell lines. Furthermore, histamine also decreases the phosphorylated beta-catenin content in HeLa cells and murine macrophages. Finally, pharmacological inhibitors of the histamine H1 receptor counteracted histamine-induced T cell factor/beta-catenin-responsive construct transactivation and the dephosphorylation of beta-catenin in HeLa cells and in macrophages. We conclude that the canonical beta-catenin pathway acts downstream of the histamine receptor H1 in a variety of cell types. The observation that inflammatory molecules, like histamine, activate the beta-catenin pathway may provide a molecular explanation for a possible link between inflammation and cancer.

Alkaline Phosphatase↗