Oncotarget

Research Papers:

Epigenetic silencing of tumor suppressor miR-3151 contributes to Chinese chronic lymphocytic leukemia by constitutive activation of MADD/ERK and PIK3R2/AKT signaling pathways

Lu Qian Wang, Kwan Yeung Wong, Anders Rosèn and Chor Sang Chim _

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Oncotarget. 2015; 6:44422-44436. https://doi.org/10.18632/oncotarget.6251

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Abstract

Lu Qian Wang1, Kwan Yeung Wong1, Anders Rosèn2, Chor Sang Chim1

1Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Hong Kong

2Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden

Correspondence to:

Chor Sang Chim, e-mail: jcschim@hku.hk

Keywords: microRNA, miR-3151, tumor suppressor, DNA methylation, chronic lymphocytic leukemia

Received: August 16, 2015     Accepted: October 14, 2015     Published: October 27, 2015

ABSTRACT

We hypothesize that miR-3151, localized to a GWAS-identified chronic lymphocytic leukemia (CLL) risk locus (8q22.3), is a tumor suppressor miRNA silenced by promoter DNA methylation in CLL. The promoter of miR-3151 was methylated in 5/7 (71%) CLL cell lines, 30/98 (31%) diagnostic primary samples, but not normal controls. Methylation of miR-3151 correlated inversely with expression. Treatment with 5-Aza-2′-deoxycytidine led to promoter demethylation and miR-3151 re-expression. Luciferase assay confirmed MAP-kinase activating death domain (MADD) and phosphoinositide-3-kinase, regulatory subunit 2 (PIK3R2) as direct targets of miR-3151. Moreover, restoration of miR-3151 resulted in inhibition of cellular proliferation and enhanced apoptosis, repression of MADD and PIK3R2, downregulation of MEK/ERK and PI3K/AKT signaling, and repression of MCL1. Lastly, miR-3151 methylation was significantly associated with methylation of miR-203 and miR-34b/c in primary CLL samples. Therefore, this study showed that miR-3151 is a tumor suppressive miRNA frequently hypermethylated and hence silenced in CLL. miR-3151 silencing by DNA methylation protected CLL cells from apoptosis through over-expression of its direct targets MADD and PIK3R2, hence constitutive activation of MEK/ERK and PI3K/AKT signaling respectively, and consequently over-expression of MCL1.


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