Epigenetic silencing of E-cadherin gene induced by lncRNA MALAT-1 in acute myeloid leukaemia.

Background: Epigenetic abnormalities in acute myeloid leukaemia provide us with a target for novel therapeutic strategies. The aim of the study was to verify the epigenetic regulatory mechanism of E-cadherin gene silencing induced by long non-coding RNA MALAT-1 in AML.

Methods: Expression of MALAT-1, E-cadherin, EZH2, SUZ12 and EED genes in AML patients was detected by RT-qPCR. After MALAT-1 silencing in AML cell lines, levels of the E-cadherin, EZH2, SUZ12, EED, DNMT1, DNMT3A and DNMT3B genes and encoded proteins were detected by RT-qPCR and Western blotting. The level of CpG island methylation and trimethylation modification of histone H3K27 in the promoter region of E-cadherin was detected by pyrosequencing and ChIP-qPCR. RIP-qPCR was used to detect the interaction between MALAT-1 and proteins.

Results: MALAT-1, EZH2 and EED gene expression was markedly increased in AML patients with E-cadherin down-regulation. A positive correlation between EZH2 or SUZ12 and MALAT-1 expression was observed. After MALAT-1 silencing, the expression of E-cadherin was up-regulated, whereas the expression of EZH2, SUZ12, DNMT1, DNMT3A and DNMT3B was down-regulated. Results of Western blotting were consistent with those of RT-qPCR. Methylation levels of E-cadherin in AML patients were higher than that in normal controls, which appeared to increase with age. Methylation of the CpG island and H3K27 trimethylation of E-cadherin were decreased after MALAT-1 silencing. RIP-qPCR suggested that MALAT-1 might be enriched by EZH2 and SUZ12.

Conclusions: Our findings verified that MALAT-1 might lead to the transcriptional silencing of E-cadherin gene through the trimethylation of H3K27 mediated by recruiting EZH2 and SUZ12.