posted on 2014-06-07, 00:00authored byZiyan Lu, Yufeng Tian, Helen R. Salwen, Alexandre Chlenski, Lucy A. Godley, J. Usha Raj, Qiwei Yang
Background: Neuroblastoma (NB), a childhood neoplasm arising from neural crest
cells, is characterized by a diversity of clinical behaviors ranging from spontaneous
remission to rapid tumor progression and death. In addition to genetic abnormalities,
recent studies have indicated that epigenetic aberrations also contribute to NB
pathogenesis. However, the epigenetic mechanisms underlying the pathogenesis of NB
are largely unknown.
Methods: Inhibition of euchromatic histone-lysine N-methyltransferase 2 (EHMT2) was
evaluated through the measurement of H3K9Me2 levels. Cell proliferation was
examined by the use of cell counting in human NB cell lines (LA1-55n, IMR-5 and
NMB). The RNA expression of EHMT2, MYCN, and p21 was measured by real-time
PCR. The expression of PCNA, MYCN, p53, cyclinD1, H3, H3K27M2, and H3K9Me2
was examined by Western blot analysis. In vitro invasion and the effects of the EHMT2
inhibitor (BIX-01294) were assessed in the Transwell chamber assay. Caspase-3 and -8
activities were measured by a Caspase-Glo assay kit. The level of global DNA
methylation was measured by liquid chromatography-mass spectroscopy.
Results: BIX-01294, a specific inhibitor of EHMT2 (a key enzyme for histone H3
dimethylation at lysine-9), specifically decreases global H3K9Me2 level but not
H3K27Me2. The inhibition of EHMT2 decreased proliferation of NB cells and induced
apoptosis by increasing caspase 8/caspase 3 activity. BIX-01294 inhibited NB cell
mobility and invasion. This was accompanied with a decreased expression of the MYCN
oncogene. Inhibition of EHMT2 enhanced a doxorubicin induced inhibitory effect on cell
proliferation. Finally EHMT2 inhibition modulated global DNA methylation levels in NB
Conclusion: Our results demonstrate that histone lysine methylation is involved in cell
proliferation, apoptosis, cell invasion, and global DNA methylation in human NB cells.
Further understanding of this mechanism may provide insight into the pathogenesis of
NB progression and lead to novel treatment strategies.
This work was supported in part by Children’s Neuroblastoma Cancer Foundation (QY),
National Institutes of Health grants R01 HL075187 (JUR) and R01 HL059435 to (JUR).
Post print version of article may differ from published version. The final publication is available at www.lww.com/; DOI: 10.1097/CAD.0b013e32835ffdbb