Repression of transforming growth factor-β receptor type I promoter expression by Sp1 deficiency

Periyasamy, Sumudra; Ammanamanchi, Sudhakar; Tillekeratne, Manoranjani; Brattain, Michael G.

doi:10.1038/sj.onc.1203822

Cited by 30 publications

(24 citation statements)

References 30 publications

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“…The present results suggest that 5-aza may activate at least three genes involved in Top-I modulation: p16, p53, and (40,41). It has been shown that DNMT inhibitors may activate Sp1 transcription (16), which in turn, upregulates the promoter activity of many Sp1-dependent genes (42). Thus, Sp1 overexpression may be an additional mechanism of Top-I up-regulation by 5-aza.…”

Section: Epigenetic Mechanisms Of Irinotecan Sensitivitymentioning

confidence: 84%

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Crea

Giovannetti

Cortesi

et al. 2009

Molecular Cancer Therapeutics

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Irinotecan is a topoisomerase-I (Top-I) inhibitor used for the treatment of colorectal cancer. DNA demethylating agents, including 5-azacytidine (5-aza), display synergistic antitumor activity with several chemotherapy drugs. 5-Aza may enhance irinotecan cytotoxicity by at least one of the following mechanisms: (a) Top-I promoter demethylation, (b) activation of genes involved in Top-I transcriptional regulation (p16 or Sp1), and (c) modulation of the cell cycle and apoptosis after DNA damage. The growth-inhibitory effects of SN38, the active metabolite of irinotecan, 5-aza, and their combinations, were studied in four colorectal cancer cell lines. The effects of treatments on cell cycle were analyzed by flow cytometry, and apoptosis was measured by fluorescence microscopy. Top-I, Sp1, and p53 expression modulated by 5-aza were measured by real-time PCR. Methylation of Top-I, p16, 14-3-3σ, and hMLH1 promoters before and after 5-aza treatment were measured by MethyLight PCR and DNA bisulfite sequencing. Low-dose 5-aza significantly enhanced the apoptotic effect of irinotecan in all colorectal cancer cells, whereas a synergistic cytotoxic effect was observed only in p53-mutated cells (HT29, SW620, and WiDr). This synergistic effect was significantly correlated with Top-I upregulation by 5-aza, and coupled to p16 demethylation and Sp1 up-regulation. p16 demethylation was also associated with enhanced cell cycle arrest after irinotecan treatment. In contrast, 5-aza down-regulated Top-I expression in the p53 wild-type LS174T cells in a p53-dependent manner, thereby reducing SN38 cytotoxicity. In conclusion, 5-aza modulates Top-I expression by several mechanisms involving Sp1, p16, and p53. If confirmed in other models, these results suggest that p16 and p53 status affects the 5-aza-irinotecan interaction.

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Section: Epigenetic Mechanisms Of Irinotecan Sensitivitymentioning

confidence: 84%

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Crea

Giovannetti

Cortesi

et al. 2009

Molecular Cancer Therapeutics

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“…Other investigators have shown that the inhibition of DNA methyltransferase (DNMT) (14,30,34,43,53) leads to a significant increase in p21…”

Section: Discussionmentioning

confidence: 99%

Methylation of Adjacent CpG Sites Affects Sp1/Sp3 Binding and Activity in the p21^Cip1 Promoter

Zhu¹,

Srinivasan²,

Dai

et al. 2003

Molecular and Cellular Biology

239

192

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DNA methylation in the promoter of certain genes is associated with transcriptional silencing. Methylation affects gene expression directly by interfering with transcription factor binding and/or indirectly by recruiting histone deacetylases through methyl-DNA-binding proteins. In this study, we demonstrate that the human lung cancer cell line H719 lacks p53-dependent and -independent p21Cip1 expression. p53 response to treatment with gamma irradiation or etoposide is lost due to a mutation at codon 242 of p53 (C3W). Treatment with depsipeptide, an inhibitor of histone deacetylase, was unable to induce p53-independent p21Cip1 expression because the promoter of p21Cip1 in these cells is hypermethylated. Although a strong correlation between promoter methylation and gene silencing has been extensively demonstrated (5,24,35), the molecular mechanisms of this methylation-modulated gene inactivation remains unclear. Two hypotheses have been proposed to explain transcriptional inactivation from promoter methylation. One of them is based on the finding that methyl-CpG-binding proteins (MBPs), such as MeCP2, specifically bind to symmetrically methylated DNA through a methyl-CpG-binding domain (11,41). MBPs then recruit transcriptional repressors such as Sin3, NuRD, and histone deacetylases (HDACs) through its transcriptional-repression domain (25,32,54). Since Sin3 and HDACs are known transcriptional repressors (2, 50), methylated DNA may repress gene expression indirectly through MeCP2 and other MBPs. In addition, deacetylation of histones results in a net increase in positively charged lysines and arginines at the N-terminal tail of the histones (18, 21), thus inducing a tighter noncovalent linkage between the positively charged histones and the negatively charged DNA (3, 47). Consequently, transcription factors have difficulty accessing their DNA-binding sites (4, 29, 47), with a reduction or silencing of gene transcription. This hypothesis, based on the interaction between DNA methylation and histone acetylation status, has been extensively supported by accumulated experimental evidence (7,16,37,40). For example, trichostatin A (TSA), an inhibitor of HDAC, induces a robust reexpression of silenced genes when used with minimal doses of the demethylating agent, 5-aza-2Ј-deoxycytidine (5-azaCdR), although TSA or 5-aza-CdR alone do not lead to gene reexpression (7). Our previous data also show a link between histone acetylation status and DNA methylation, such that 5-aza-CdR significantly enhances acetylation of histones H3 and H4 induced by a HDAC inhibitor, depsipeptide. Related to this, depsipeptide-induced apoptosis is dramatically increased in cells pretreated with 5-aza-CdR (56). In addition, p19 INK4D expression is greatly enhanced when human lung cancer cells are treated with depsipeptide and 5-aza-CdR together compared to treatment with each agent alone (55). These studies support the notion that methylation and histone acetylation work cooperatively to influence gene expression and other biological processes.A...

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“…MMTV-PyMT transgenic mice express polyomavirus middle T antigen and develop spontaneous multifocal mammary tumors with a rapid conversion of mammary epithelium to the malignant state (10). Epigenetic silencing of tumor suppressor and growth regulatory genes has been implicated in breast cancer (11)(12)(13)(14)(15) and dysregulated DNA methyltransferase activity may also be a contributing factor to breast cancer development (16). Therefore, to determine the ability of zebularine to prevent or treat breast cancer, we tested if daily oral treatment with zebularine affects mammary tumor growth in these MMTV-PyMT mice.…”

Section: Introductionmentioning

confidence: 99%

DNA Methyltransferase Inhibitor, Zebularine, Delays Tumor Growth and Induces Apoptosis in a Genetically Engineered Mouse Model of Breast Cancer

Chen

Shabashvili

Nawab

et al. 2012

Molecular Cancer Therapeutics

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Zebularine is a novel potent inhibitor of both cytidine deaminase and DNA methylation. We examined the effect of zebularine on mammary tumor growth in genetically engineered MMTV-PyMT transgenic mice that develop mammary tumors at 60 days of age with 100% penetrance. The MMTV-PyMT transgenic mice were randomized at 46 days of age into control (n ¼ 25) and zebularine (n ¼ 25) treatment groups and monitored for parameters of tumor growth. Zebularine was administered at 5 mg/mL in drinking water. We observed a significant delay in the growth of mammary tumors in zebularine-treated mice with a statistically significant reduction (P ¼ 0.0135) in total tumor burden at 94 days of age when the mice were sacrificed. After 48 days of zebularine treatment, the tumors were predominantly necrotic compared with untreated animals. In addition, a high apoptotic index by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was observed as early as 13 days following treatment. Immunoblot analysis showed depletion of DNMT1 and partial depletion of DNMT3b after zebularine treatment. Microarray analyses of global gene expression identified upregulation of twelve methylation-regulated genes as well as a set of candidate cancer genes that participate in cell growth and apoptosis. In summary, zebularine inhibits the growth of spontaneous mammary tumors and causes early onset of tumor cell necrosis and apoptosis in a genetically engineered mouse model of breast cancer. Defining the parameters of zebularine-mediated tumor inhibition may advance the future development of DNA methyltransferase inhibitors as an effective cancer treatment. Mol Cancer Ther; 11(2); 370-82. Ó2011 AACR.

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Repression of transforming growth factor-β receptor type I promoter expression by Sp1 deficiency

Cited by 30 publications

References 30 publications

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Methylation of Adjacent CpG Sites Affects Sp1/Sp3 Binding and Activity in the p21^Cip1 Promoter

DNA Methyltransferase Inhibitor, Zebularine, Delays Tumor Growth and Induces Apoptosis in a Genetically Engineered Mouse Model of Breast Cancer

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Repression of transforming growth factor-β receptor type I promoter expression by Sp1 deficiency

Cited by 30 publications

References 30 publications

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Epigenetic mechanisms of irinotecan sensitivity in colorectal cancer cell lines

Methylation of Adjacent CpG Sites Affects Sp1/Sp3 Binding and Activity in the p21Cip1 Promoter

DNA Methyltransferase Inhibitor, Zebularine, Delays Tumor Growth and Induces Apoptosis in a Genetically Engineered Mouse Model of Breast Cancer

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Product

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Methylation of Adjacent CpG Sites Affects Sp1/Sp3 Binding and Activity in the p21^Cip1 Promoter