| 1. |
- Dock, H., et al.
(författare)
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Maintenance of the E.coli dcm Methylation of the CMV Promoter, in Contrast to Hypomethylation of the Recognition Sequence of Transcription Factor NFkB in Transfected GBM Cells
- 2016
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Ingår i: Cloning & Transgenesis. - : OMICS Publishing Group. - 2168-9849. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- The human cytomegalovirus (CMV) immediate early promoter has been extensively used to drive target gene expression in transgenic mammalian cells. DNA methylation of the CMV promoter has been shown to be the reason for a reduced promoter activity and silencing of the target gene. We have established an in vitro model system, in which human brain cancer cells (glioblastoma multiforme, GBM) were transfected with pAdTrack-CMV-GFP plasmid, isolated from a dcm positive (dcm+) E. coli strain. We found that in two CCTGG sequences located at position from -304 to -300 nt and from -497 to -493 nt of the CMV promoter region, the internal C was methylated in all analyzed clones, i.e., the E. coli dcm methylation pattern is maintained in the CMV promoter region after its integration into the human genome. In contrast, we found that the recognition sites for the transcription factor NFkB and certain other transcription factors in the enhancer region of the CMV promoter (from -107 to -270 nt) were hypomethylated. This might explain why the CMV promoter maintained an active mode, driving the GFP expression despite the demonstrated methylation of the CMV promoter. We noticed that the CCTGG sequence is also contained in the binding sequence motif of transcription factor NFkB. Hence we have comprehensively studied transcription factors through a database searching, and the responsive elements that contain dcm methylation sequences CCW(A/T)GG. A list of transcription factors and the corresponding regulated genes are presented.
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| 2. |
- Liu, Hua, et al.
(författare)
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Low dose Zebularine treatment enhances immunogenicity of tumor cells
- 2007
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Ingår i: Cancer Letters. - : Elsevier BV. - 1872-7980 .- 0304-3835. ; 257:1, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- Strategy: We have investigated how alterations in gene expression induced by the demethylating drug Zebularine affect the immune response tumor cells elicit. The rational has been to treat syngeneic rat colon cancer cells with Zebularine at different concentrations and then use these cells to study gene expression of different genes involved in cancer immunogenicity. Gene expressions were monitored by semi-quantitative PCR and real-time PCR. Results: Intriguingly there was a large increase in the production of indoleamine 2,3-dioxygenase (IDO) after treatment with 100 mu M Zebularine as compared with untreated tumor cells, whereas treatment with 20 mu M Zebularine caused a significant decrease of the IDO production. After immunization with syngeneic tumor cells, spleen cells were isolated and restimulated in vitro with irradiated tumor cells. Immune reactivity was measured by proliferation, and production of interferon gamma and interleukinl0. The immunogenicity of tumor cells treated in vitro with a low dose of Zebularine increased, whereas it decreased after high dose exposure. The inhibition of immunogenicity by 100 mu M Zebularine was shown to be counteracted by the IDO inhibitor I methyl-tryptophan (1MT), confirming that this effect of Zebularine is mainly caused by IDO induction. Differences using Zebularine-treated or non-treated cells for in vitro restimulation were marginal. Conclusion: Low dose treatment with Zebularine (20 mu M) decreases the production of the immunosuppressive IDO from rat colon cancer cells and enhances their immunogenicity, whereas high dose Zebularine treatment (100 mu M) enhances the IDO production from the cancer cells and suppresses their immunogenicity. This immunosuppression should be considered when cancer is treated with Zebularine or drugs acting in a similar way. (C) 2007 Published by Elsevier Ireland Ltd.
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| 3. |
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| 4. |
- Nittby, Henrietta, et al.
(författare)
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Zebularine induces long-term survival of pancreatic islet allotransplants in streptozotocin treated diabetic rats.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- Coping with the immune rejection of allotransplants or autologous cells in patients with an active sensitization towards their autoantigens and autoimmunity presently necessitates life-long immune suppressive therapy acting on the immune system as a whole, which makes the patients vulnerable to infections and increases their risk of developing cancer. New technologies to induce antigen selective long-lasting immunosuppression or immune tolerance are therefore much needed.
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| 5. |
- Xue, Zhongtian, et al.
(författare)
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An epigenetic mechanism for high, synergistic expression of indoleamine 2,3-dioxygenase 1 (IDO1) by combined treatment with zebularine and IFN-γ: Potential therapeutic use in autoimmune diseases.
- 2012
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Ingår i: Molecular Immunology. - : Elsevier BV. - 1872-9142 .- 0161-5890. ; 51:2, s. 101-111
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Tidskriftsartikel (refereegranskat)abstract
- IDO1 can be induced by interferon gamma (IFN-γ) in multiple cell types. We have earlier described that the DNA methyltransferase inhibitor zebularine also induces IDO1 in several rat cell clones. We now describe a synergistic induction of IDO1 expression by IFN-γ and zebularine. To elucidate the mechanism of the IDO1 induction we have studied the methylation status in the promoter region of the IDO1 gene from both human monocytic THP-1 cells and H1D2 rat colon cancer cells. Interestingly, the IDO1 promoter is hypermethylated and IFN-γ is shown to induce a significant demethylation. The synergism in effect of zebularine and IFN-γ on IDO1 expression is paralleled by a similar synergistic effect on expression of two other IFN-γ-responsive genes, the transcription factors STAT1 and IRF1 with binding sites in the IDO1 promoter region. The demonstrated synergistic activation of IDO1 expression has implications in relation to therapeutic induction of immunosuppression in autoimmunity and chronic inflammation.
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