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Reduction of DNA methylation suppresses colon carcinogenesis through induction of tumor cell differentiation

ABSTRACT: In this study, we analyzed global gene expressions of colon tumors from DNA hypomethylated and the control mice. We found that DNA hypomethylated tumors express significantly higher levels of intestinal differentiation-related genes when compared with the control tumors. These results suggest that DNA methylation may play a role in the maintenance of undifferentiated state of colon tumor cells. Two different Dnmt1 mutant alleles were used in this study; hypomorphic Dnmt1chip allele and conventional KO Dnmt1c allele, which described previously. Previous studies indicated that Dnmt1chip/c mice have reduced DNA methylation contents at pericentromeric satellite repeats, while Dnmt1chip/+ mice have the same levels of genomic methylation as wildtype mice. Experimental mice in an isogenic F1 hybrid background were obtained by breeding Dnmt1c/+; ApcMin/+ mouse in the C57BL/6 background with Dnmt1chip/chip; Apc+/+ mouse in the 129Sv4 background. Six-week-old DNA hypomethylated (Dnmt1chip/c; ApcMin/+) and the control (Dnmt1chip/+; ApcMin/+) mice were fed with 2% (w/v) dextran sodium sulfate (DSS), a potent promoter for colon carcinogenesis. At 20 weeks of age, colon tumors were harvested from both cohorts (n=3 for both DNA hypomethylated tumors and the control tumors) and analyzed for their gene expressions.

ORGANISM(S): Mus musculus

SUBMITTER: Yasuhiro Yamada

PROVIDER: E-GEOD-60620 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Reducing DNA methylation suppresses colon carcinogenesis by inducing tumor cell differentiation.

Hatano Yuichiro Y Semi Katsunori K Hashimoto Kyoichi K Lee Myeong Sup MS Hirata Akihiro A Tomita Hiroyuki H Kuno Toshiya T Takamatsu Manabu M Aoki Koji K Taketo Makoto M MM Kim Young-Joon YJ Hara Akira A Yamada Yasuhiro Y

Carcinogenesis 20150504 7

The forced reduction of global DNA methylation suppresses tumor development in several cancer models in vivo. Nevertheless, the mechanisms underlying these suppressive effects remain unclear. In this report, we describe our findings showing that a genome-wide reduction in the DNA methylation levels induces cellular differentiation in association with decreased cell proliferation in Apc (Min/+) mouse colon tumor cells in vivo. Colon tumor-specific DNA methylation at Cdx1 is reduced in the DNA-hyp ...[more]

PMID: 25939752

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Project description:To identify the precise molecular mechanisms that could contribute to the increase in colon carcinogenesis, microarray gene expression analysis was performed on colon RNA isolated from 5-week-old VhlF/F and VhlΔIE, VhlΔIE/Apcmin/+ and VhlF/F/Apcmin/+ mice. Hypoxia-inducible factor (HIF) is a key modulator of the transcriptional response to hypoxia and is increased in colon cancer. However, the role of HIF in colon carcinogenesis in vivo remains unclear. Intestinal epithelium-specific disruption of the von Hippel-Lindau tumor suppressor protein (VHL) resulted in constitutive HIF signaling, and increased HIF expression augmented colon tumorigenesis in the Apcmin/+ intestinal tumor model. Intestine-specific disruption of Vhl increased colon tumor multiplicity and progression from adenomas to carcinomas. These effects were ameliorated in mice with double disruption of Vhl and Hif-2α. Activation of HIF signaling resulted in increased cell survival in normal colon tissue, however tumor apoptosis was not affected. Interestingly, a robust activation of cyclin D1 was observed in tumors of Apcmin/+ mice in which HIF-2α was activated in the intestine. Consistent with this result, BrdU incorporation indicated that cellular proliferation was increased in colon tumors following HIF activation. Further analysis demonstrated that dysregulation of the intestinal iron absorption transporter divalent metal transporter-1 (DMT-1) was a critical event in HIF-2α-mediated colon carcinogenesis. These data provide a mechanistic basis for the widely reported link between iron accumulation and colon cancer risk. Together, our findings demonstrate that a chronic increase in HIF-2α in the colon initiates pro-tumorigenic signaling which may have important implications in developing preventive and therapeutic strategies for colon cancer. Global gene expression profiling in colon RNAs isolated from 5-week-old VhlF/F (n=4, Shah 001), VhlF/F/Apcmin/+(n=3, Shah 003), VhlΔIE (n=3, Shah 002) and VhlΔIE/Apcmin/+ mice (n=5, Shah 004).

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Reduction of DNA methylation suppresses colon carcinogenesis through induction of tumor cell differentiation

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Reducing DNA methylation suppresses colon carcinogenesis by inducing tumor cell differentiation.

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