Loss of Dnmt3b function upregulates the tumor modifier Ment and accelerates mouse lymphomagenesis
Ryan A. Hlady, … , Judith K. Christman, Rene Opavsky
Ryan A. Hlady, … , Judith K. Christman, Rene Opavsky
Published December 1, 2011
Citation Information: J Clin Invest. 2012;122(1):163-177. https://doi.org/10.1172/JCI57292.
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Research Article Hematology

Loss of Dnmt3b function upregulates the tumor modifier Ment and accelerates mouse lymphomagenesis

Abstract

DNA methyltransferase 3B (Dnmt3b) belongs to a family of enzymes responsible for methylation of cytosine residues in mammals. DNA methylation contributes to the epigenetic control of gene transcription and is deregulated in virtually all human tumors. To better understand the generation of cancer-specific methylation patterns, we genetically inactivated Dnmt3b in a mouse model of MYC-induced lymphomagenesis. Ablation of Dnmt3b function using a conditional knockout in T cells accelerated lymphomagenesis by increasing cellular proliferation, which suggests that Dnmt3b functions as a tumor suppressor. Global methylation profiling revealed numerous gene promoters as potential targets of Dnmt3b activity, the majority of which were demethylated in Dnmt3b–/– lymphomas, but not in Dnmt3b–/– pretumor thymocytes, implicating Dnmt3b in maintenance of cytosine methylation in cancer. Functional analysis identified the gene Gm128 (which we termed herein methylated in normal thymocytes [Ment]) as a target of Dnmt3b activity. We found that Ment was gradually demethylated and overexpressed during tumor progression in Dnmt3b–/– lymphomas. Similarly, MENT was overexpressed in 67% of human lymphomas, and its transcription inversely correlated with methylation and levels of DNMT3B. Importantly, knockdown of Ment inhibited growth of mouse and human cells, whereas overexpression of Ment provided Dnmt3b+/+ cells with a proliferative advantage. Our findings identify Ment as an enhancer of lymphomagenesis that contributes to the tumor suppressor function of Dnmt3b and suggest it could be a potential target for anticancer therapies.

Authors

Ryan A. Hlady, Slavomira Novakova, Jana Opavska, David Klinkebiel, Staci L. Peters, Juraj Bies, Jay Hannah, Javeed Iqbal, Kristi M. Anderson, Hollie M. Siebler, Lynette M. Smith, Timothy C. Greiner, Dhundy Bastola, Shantaram Joshi, Oksana Lockridge, Melanie A. Simpson, Dean W. Felsher, Kay-Uwe Wagner, Wing C. Chan, Judith K. Christman, Rene Opavsky

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Figure 2

Loss of Dnmt3b results in enhanced proliferation of tumors in vivo.

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Loss of Dnmt3b results in enhanced proliferation of tumors in vivo. EGFP...
EGFP expression (A), apoptosis (B), and BrdU incorporation assay (C), as determined by FACS analysis of thymocytes isolated from MYC;Dnmt3b+/+ and MYC;Dnmt3b–/– mice at 20, 35, and 50 days of age as well as in terminally ill mice (Final). Anti–annexin V and anti-BrdU antibodies were used to evaluate apoptosis and BrdU incorporation, respectively. Representative examples of FACS analysis at the indicated ages are shown; percent positive cells in the FACS profile is shown within each plot. Error bars represent ± SEM; n as indicated. *P < 0.05, pairwise comparisons, Student’s t test with Bonferroni correction.