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Epigenetic inactivation of mir-34b/c in addition to mir-34a and DAPK1 in chronic lymphocytic leukemia
University of Hong Kong, China.
University of Hong Kong, China.
Queen Elizabeth Hospital, Hong Kong, China.
Pamela Youde Nethersole Hospital, Hong Kong, China.
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2014 (English)In: Journal of Translational Medicine, ISSN 1479-5876, Vol. 12, no 52Article in journal (Refereed) Published
Abstract [en]


TP53 mutation/deletion is uncommon in chronic lymphocytic leukemia (CLL). We postulated that components of TP53-centered tumor suppressor network, miR-34b/c, in addition to DAPK1 and miR-34a might be inactivated by DNA hypermethylation. Moreover, we tested if miR-34b/c methylation might correlate with miR-203 or miR-124-1 methylation in CLL.


miR-34b/c, miR-34a and DAPK1 methylation was studied in 11 normal controls, 7 CLL cell lines, and 78 diagnostic CLL samples by methylation-specific polymerase chain reaction. MEC-1 cells were treated with 5-Aza-2'-deoxycytidine for reversal of methylation-associated miRNA silencing. Tumor suppressor properties of miR-34b were demonstrated by over-expression of precursor miR-34b in MEC-1 cells.


miR-34b/c promoter was unmethylated in normal controls, but completely methylated in 4 CLL cell lines. miR-34b/c expression inversely correlated with miR-34b/c methylation. Different MSP statuses of miR-34b/c, including complete methylation and complete unmethylation, were verified by quantitative bisulfite pyrosequencing. 5-Aza-2'-deoxycytidine treatment resulted in promoter demethylation and miR-34b re-expression in MEC1 cells. Moreover, over-expression of miR-34b resulted in inhibition of cellular proliferation and increased cell death. In primary CLL samples, miR-34a, miR-34b/c and DAPK1 methylation was detected in 2.6%, 17.9% and 34.6% of patients at diagnosis respectively. Furthermore, 39.7%, 3.8% and 2.6% patients had methylation of one, two or all three genes respectively. Overall, 46.2% patients had methylation of at least one of these three genes. Besides, miR-34b/c methylation was associated with methylation of miR-34a (P = 0.03) and miR-203 (P = 0.012) in CLL.


Taken together, miR-34b/c is a tumor suppressor miRNA frequently methylated, and hence silenced in CLL. Together with DAPK1 methylation, miR-34b/c methylation is implicated in the disruption of the TP53-centered tumor suppressor network. Moreover, the association of miRNA methylation warrants further study.

Place, publisher, year, edition, pages
BioMed Central, 2014. Vol. 12, no 52
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-104694DOI: 10.1186/1479-5876-12-52ISI: 000335533000002PubMedID: 24559316OAI: diva2:698576
Available from: 2014-02-24 Created: 2014-02-24 Last updated: 2014-06-03Bibliographically approved

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Rosén, Anders
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