Absent in Melanoma 2 (AIM2) is a member of the HIN-200 family of hematopoietic, IFN-inducible nuclear proteins associated with infection defense and tumor pathology. Recently, AIM2 was found to act as a DNA sensor in innate immunity. In addition, a high frequency of AIM2-alterations was observed in microsatellite unstable tumors. To elucidate AIM2 function in colorectal tumors, we here addressed AIM2-responsive genes by microarray. Among genes up-regulated by AIM2, there were a number of interferon-stimulated genes (ISGs: IFIT1, IFIT2, IFIT3, IFI6, IRF7, ISG15, HLA-DRA, HLA-DRB, TLR3 and CIITA) as well as genes involved in intercellular adhesion and matrix remodeling. Expression of ISGs correlated with expression of AIM2 in ten different IFN- treated colorectal cancer cell lines. Moreover, knock-down of AIM2 resulted in reduced expression of HLA-DRA, HLA-DRB, and CIITA in IFN- treated cells. IFN- independent induction of HLA-DR genes and their encoded proteins was also demonstrated upon transient induction of AIM2. STAT-signaling was not involved in IFN- independent induction of ISGs, arguing against participation of cytokines released in an autocrine manner. Our data indicate that AIM2 mediates IFN- dependent and independent induction of several Interferon stimulated genes (ISGs) including genes encoding the MHC II antigens HLA-DR and .
Absent in Melanoma 2 (AIM2) is an important mediator of interferon-dependent and -independent HLA-DRA and HLA-DRB gene expression in colorectal cancers.
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The aim was to investigate mechanisms contributing to quercetins previously described effects on cell-proliferation and -differentiation, which contradicted its proposed anti-carcinogenic potency. In a 10-day experiment, 40 M quercetin stabilized by 1mM ascorbate reduced Caco-2 differentiation up to 50% (P<0.001). Caco-2 RNA from days 5 and 10, hybridized on HG-U133A2.0 Affymetrix GeneChips, showed 1,743 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).
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.
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Quercetin has been shown to act as an anti-carcinogen in experimental colorectal cancer (CRC). The aim of the present study was to characterise transcriptome and proteome changes occurring in the distal colon mucosa of rats supplemented with 10 g quercetin/kg diet for 11 weeks. Transcriptome data analysed with Gene Set Enrichment Analysis showed that quercetin significantly downregulated the potentially oncogenic mitogen-activated protein kinase (Mapk) pathway. In addition, quercetin enhanced expression of tumor suppressor genes, including Pten, Tp53 and Msh2, and of cell cycle inhibitors, including Mutyh. Furthermore, dietary quercetin enhanced genes involved in phase I and II metabolism, including Fmo5, Ephx1, Ephx2 and Gpx2. Quercetin increased PPAR target genes, and concomitantly enhanced expression genes in volved in of mitochondrial fatty acid degradation. Proteomics performed in the same samples revealed 33 affected proteins, of which 4 glycolysis enzymes and 3 heatshock proteins were decreased. A proteome-transcriptome comparison showed a low correlation, but both pointed out towards altered energy metabolism.
Transcriptome and proteome profiling of colon mucosa from quercetin fed F344 rats point to tumor preventive mechanisms, increased mitochondrial fatty acid degradation and decreased glycolysis.
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