Oncotarget

Research Papers:

Epigenetic silencing of tumor suppressor long non-coding RNA BM742401 in chronic lymphocytic leukemia

Lu Qian Wang, Kwan Yeung Wong, Zhen Hai Li and Chor Sang Chim _

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Oncotarget. 2016; 7:82400-82410. https://doi.org/10.18632/oncotarget.12252

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Abstract

Lu Qian Wang1, Kwan Yeung Wong1, Zhen Hai Li1, Chor Sang Chim1

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

Correspondence to:

Chor Sang Chim, email: jcschim@hku.hk

Keywords: BM742401, lncRNA, tumor suppressor, DNA methylation, chronic lymphocytic leukemia

Received: January 20, 2016     Accepted: September 20, 2016     Published: September 26, 2016

ABSTRACT

BM742401 is a tumor suppressor lncRNA downregulated in gastric cancer. As the promoter region and the entire transcript are embedded in a CpG island, we postulated that BM742401 is a tumor suppressor lncRNA inactivated by DNA methylation in chronic lymphocytic leukemia (CLL). The promoter of BM742401 was unmethylated in normal controls including three each of normal bone marrow, peripheral blood buffy coats, and CD19-sorted peripheral B-cells, but methylated in four (57.1%) CLL cell lines. Methylation of BM742401 correlated inversely with expression. In the completely methylated WAC3CD5+ CLL cells, 5-Aza-2′-deoxycytidine treatment led to promoter demethylation and re-expression of BM742401 transcript. Functionally, stable overexpression of BM742401 resulted in inhibition of cellular proliferation and enhanced apoptosis through caspase-9-dependent intrinsic but not caspase-8-dependent extrinsic apoptosis pathway, suggesting a tumor suppressor role of BM742401 in CLL. In primary CLL samples, methylation of BM742401 was detected in 43/98 (43.9%) of patients. Moreover, among CLL patients with standard-risk cytogenetic aberrations, methylation of BM742401 correlated with advanced Rai stage (≥ stage 2)(P = 0.002). Furthermore, BM742401 methylation was associated with miR-129-2 methylation (P = 0.05). BM742401 is a tumor suppressor lncRNA frequently methylated in CLL. The mechanism of BM742401 as a tumor suppressor warrants further studies.


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