BRAF mutation-specific promoter methylation of FOX genes in colorectal cancer

Background: Cancer-specific hypermethylation of (promoter) CpG islands is common during the tumorigenesis of colon cancer. Although associations between certain genetic aberrations, such as BRAF mutation and microsatellite instability, and the CpG island methylator phenotype (CIMP), have been found, the mechanisms by which these associations are established are still unclear. We studied genome-wide DNA methylation differences between

Cleavage of the actin-capping protein alpha -adducin at Asp-Asp-Ser-Asp633-Ala by caspase-3 is preceded by its phosphorylation on serine 726 in cisplatin-induced apoptosis of renal epithelial cells

Decreased phosphorylation of focal adhesion kinase and paxillin is associated with loss of focal adhesions and stress fibers and precedes the onset of apoptosis (van de Water, B., Nagelkerke, J. F., and Stevens, J. L. (1999) J. Biol. Chem. 274, 13328-13337). The cortical actin cytoskeletal network is also lost during apoptosis, yet little is known about the temporal relationship between altered phosphorylation of proteins that are critical in the regulation of this network and their potential cleavage by caspases during apoptosis. Adducins are central in the cortical actin network organization. Cisplatin caused apoptosis of renal proximal tubular epithelial cells, which was associated with the cleavage of alpha-adducin into a 74-kDa fragment; this was blocked by a general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-fmk). Hemagglutinin-tagged human alpha-adducin was cleaved into a similar 74-kDa fragment by caspase-3 in vitro but not by caspase-6 or -7. Asp-Arg-Val-Asp(29)-Glu, Asp-Ile-Val-Asp(208)-Arg, and Asp-Asp-Ser-Asp(633)-Ala were identified as the principal caspase-3 cleavage sites; Asp-Asp-Ser-Asp(633)-Ala was key in the formation of the 74-kDa fragment. Cisplatin also caused an increased phosphorylation of alpha-adducin and gamma-adducin in the MARCKS domain that preceded alpha-adducin cleavage and was associated with loss of adducins from adherens junctions; this was not affected by z-VAD-fmk. In conclusion, the data support a model in which increased phosphorylation of alpha-adducin due to cisplatin leads to dissociation from the cytoskeleton, a situation rendered irreversible by caspase-3-mediated cleavage of alpha-adducin at Asp-Asp-Ser-Asp(633)-Ala.Toxicolog

The homeobox gene MEIS1 is methylated in BRAFp.V600E mutated colon tumors

Development of colorectal cancer (CRC) can occur both via gene mutations in tumor suppressor genes and oncogenes, as well as via epigenetic changes, including DNA methylation. Site-specific methylation in CRC regulates expression of tumor-associated genes. Right-sided colon tumors more frequently have BRAFp.V600E mutations and have higher methylation grades when compared to left-sided malignancies. The aim of this study was to identify DNA methylation changes associated with BRAFp.V600E mutation status. We performed methylation profiling of colon tumor DNA, isolated from frozen sections enriched for epithelial cells by macro-dissection, and from paired healthy tissue. Single gene analyses comparing BRAFp.V600E with BRAF wild type revealed MEIS1 as the most significant differentially methylated gene (log2 fold change: 0.89, false discovery rate-adjusted P-value 2.8*10-9). This finding was validated by methylation-specific PCR that was concordant with the microarray data. Additionally, validation in an independent cohort (n=228) showed a significant association between BRAF p.V600E and MEIS1 methylation (OR: 13.0, 95% CI: 5.2 - 33.0, P<0.0001). MEIS1 methylation was associated with decreased MEIS1 gene expression in both patient samples and CRC cell lines. The same was true for gene expression of a truncated form of MEIS1, MEIS1D27, which misses exon 8 and has a proposed tumor suppression function. To trace the origin of MEIS1 promoter methylation, 14 colorectal tumors were flow-sorted. Four out of eight BRAFp.V600E tumor epithelial fractions (50%) showed MEIS1 promoter methylation, as well as three out of eight BRAFp.V600E stromal fractions (38%). Only one out of six BRAF wild type showed MEIS1 promoter methylation in both the epithelial tumor and stromal fractions (17%). In conclusion, BRAFp.V600E colon tumors showed significant MEIS1 promoter methylation, which was associated with decreased MEIS1 gene expression. Copyright

Biomarkers of quercetin-mediated modulation of colon carcinogenesis

Colorectal cancer (CRC) is hypothesized to be prevented by intake of fruits and vegetables that contain anti-carcinogenic compounds, including the<span class=SpellE>flavonoid</span><span class=SpellE>quercetin</span>that is found in apples and onions. In this thesis,<span class=SpellE>quercetin's</span>mechanisms of cancer-preventive action were studied both in vitro and in vivo . The in vitro experiments were performed using the human Caco-2 cell line as a model for CRC, and<span class=SpellE>quercetin</span>stabilized by<span class=SpellE>ascorbate</span>in the culture medium. Unexpectedly,<span class=SpellE>ascorbate</span>-stabilized<span class=SpellE>quercetin</span>showed enhancement of cellular processes involved in CRC-development, including stimulated cell proliferation, reduced cell differentiation and enhancement of pathways that stimulate cell survival. Furthermore,<span class=SpellE>transcriptomics</span>showed that<span class=SpellE>quercetin</span><span class=SpellE>downregulated</span>expression of genes involved in<span class=SpellE>tumor</span>suppression and phase II metabolism, and<span class=SpellE>upregulated</span><span class=SpellE>oncogenes</span>. Comparison with Caco-2 cells exposed to<span class=SpellE>quercetin</span>in the absence of<span class=SpellE>ascorbate</span>showed the opposite, i.e. anti-carcinogenic effects by this<span class=SpellE>flavonoid</span>. This led to the hypothesis that<span class=SpellE>quercetin</span>-induced reactive oxygen species that eradicate<span class=SpellE>tumor</span>cells were scavenged by vitamin C, causing<span class=SpellE>tumor</span>cell survival. Without<span class=SpellE>ascorbate</span>, these reactive oxygen species may be responsible for anti-carcinogenic effects, pointing to beneficial effects of supposed adverse reactive intermediates.<o:p></o:p></span>Subsequently, the CRC-modulating potency of<span class=SpellE>quercetin</span>and its conjugate<span class=SpellE>rutin</span>were investigated in a rat model for CRC.<span class=SpellE>Quercetin</span>, but not its conjugate<span class=SpellE>rutin</span>decreased the<span class=SpellE>tumor</span>incidence, which was associated with the blood plasma levels of this anti-oxidant, but not reflected by the putative<span class=SpellE>preneoplastic</span>biomarker lesions, designated aberrant crypt foci. The combination of<span class=SpellE>transcriptomics</span>and proteomics showed that<span class=SpellE>quercetin</span>inhibited the potentially<span class=SpellE>oncogenic</span><span class=SpellE>mitogen</span>-activated protein<span class=SpellE>kinase</span>(<span class=SpellE>Mapk</span>) pathway and enhanced expression of<span class=SpellE>tumor</span>suppressor genes, cell cycle inhibitors, and genes involved in<span class=SpellE>xenobiotic</span>metabolism. In addition,<span class=SpellE>quercetin</span>affected the energy production pathways, by increasing mitochondrial fatty acid degradation, and inhibiting<span class=SpellE>glycolysis</span>. This observation provided a new hypothesis pointing at another anti-carcinogenic mechanism for<span class=SpellE>quercetin</span>, based on an alteration in routes for energy metabolism, shifting them in<span class=SpellE>favor</span>of non-<span class=SpellE>tumor</span>like pathways like mitochondrial fatty acid degradation at the cost of the<span class=SpellE>tumor</span>-like<span class=SpellE>glycolytic</span>pathway for cellular energy supply.<o:p></o:p></span>Overall, the studies presented in the present thesis provided new hypotheses for the mode of action of<span class=SpellE>quercetin</span>as an anti-<span class=SpellE>tumor</span>agent, but it appeared that the actual dose needed to exert this beneficial effect amounted to about 60 - 100 times the already relatively high prescribed dose for<span class=SpellE>quercetin</span>supplements. Therefore, it is concluded that health claims on the use of<span class=SpellE>quercetin</span>as an anti-cancer agent need better scientific support

Менеджмент современной брендинговой политики

Изменение имени очередного бренда приводит к росту объемов потребления, расширению ассортимента, а также создает новые рабочие места не только на фирме-производителе, а и в каналах распределения продукции. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/2066

Pathway and single gene analyses of inhibited Caco-2 differentiation by ascorbate-stabilized quercetin suggest enhancement of cellular processes associated with development of colon cancer

The aim was to investigate mechanisms contributing to quercetin's previously described effects on cell-proliferation and -differentiation, which contradicted its proposed anticarcinogenic potency. in a 10-day experiment, 40 mu M quercetin stabilized by I mM ascorbate reduced Caco-2 differentiation up to 50% (p <0.001). Caco-2 RNA from days 5 and 10, hybridized on HG-U133A2.0Affymetrix Gene Chips(circle dot), showed 1743 affected genes on both days (p <0.01). All 14 Caco-2 differentiation-associated genes showed decreased expression (p <0.01), including intestinal alkaline phosphatase, that was confirmed technically (qRT-PCR) and functionally (enzyme-activity). The 1743 genes contributed to 27 pathways (p <0.05) categorized under six gene ontology (GO) processes, including apoptosis and cell-cycle. Genes within these GO-processes showed fold changes that suggest increased cell-survival and -proliferation. Furthermore, quercetin down-regulated expression of genes involved in tumor-suppression and phase 11 metabolism, and up-regulated oncogenes. Gene expression changes mediated by ascorbate-stabilized quercetin were concordant with those occurring in human colorectal carcinogenesis (approximate to 80-90%), but were opposite to those previously described for Caco-2 cells exposed to quercetin without ascorbate (approximate to 75-90%). In conclusion, gene expression among Caco-2 cells exposed to ascorbate-stabilized quercetin showed mechanisms contrary to what is expected for a cancer-preventive agent. Whether this unexpected in vitro effect is relevant in vivo, remains to be elucidated

Chronic quercetin exposure affects fatty acid catabolism in rat lung

Dietary quercetin intake is suggested to be health promoting, but this assumption is mainly based on mechanistic studies performed in vitro. Previously, we identified rat lung as a quercetin target tissue. To assess relevant in vivo health effects of quercetin, we analyzed mechanisms of effect in rat lungs of a chronic (41 weeks) 1% quercetin diet using whole genome microarrays. We show here that fatty acid catabolism pathways, like beta-oxidation and ketogenesis, are up-regulated by the long-term quercetin intervention. Up-regulation of genes (Hmgcs2, Ech1, Acox1, Pcca, Lpl and Acaa2) was verified and confirmed by quantitative real time PCR. In addition, free fatty acid levels were decreased in rats fed the quercetin diet, confirming that quercetin affects fatty acid catabolism. This in vivo study demonstrates for the first time that fatty acid catabolism is a relevant process that is affected in rats by chronic dietary quercetin

Tissue distribution of quercetin in rats and pigs

Quercetin is a dietary polyphenolic compound with potentially beneficial effects on health. Claims that quercetin has biological effects are based mainly on in vitro studies with quercetin aglycone. However, quercetin is rapidly metabolized, and we have little knowledge of its availability to tissues. To assess the long-term tissue distribution of quercetin, 2 groups of rats were given a 0.1 or 1% quercetin diet [50 or 500 mg/kg body weight (wt)] for 11 wk. In addition, a 3-d study was done with pigs fed a diet containing 500 mg quercetin/kg body wt. Tissue concentrations of quercetin and quercetin metabolites were analyzed with an optimized extraction method. Quercetin and quercetin metabolites were widely distributed in rat tissues, with the highest concentrations in lungs (3.98 and 15.3 nmol/g tissue for the 0.1 and 1% quercetin diet, respectively) and the lowest in brain, white fat, and spleen. In the short-term pig study, liver (5.87 nmol/g tissue) and kidney (2.51 nmol/g tissue) contained high concentrations of quercetin and quercetin metabolites, whereas brain, heart, and spleen had low concentrations. These studies have for the first time identified target tissues of quercetin, which may help to understand its mechanisms of action in viv

The homeobox gene MEIS1 is methylated in BRAFp.V600E mutated colon tumors

10.1371/journal.pone.0079898PLoS ONE811e7989