Histone methylation is implicated in a number of biological and pathological processes, including cancer development. In this study, we investigated the molecular mechanism for the recruitment of Polycomb repressive complex-2 (PRC2) and its accessory component, JARID2, to chromatin, which regulates methylation of lysine 27 of histone H3 (H3K27), during epithelial-mesenchymal transition (EMT) of cancer cells. The expression of MEG3 long noncoding RNA (lncRNA), which could interact with JARID2, was clearly increased during transforming growth factor-β (TGF-β)-induced EMT of human lung cancer cell lines. Knockdown of MEG3 inhibited TGF-β-mediated changes in cell morphology and cell motility characteristic of EMT and counteracted TGF-β-dependent changes in the expression of EMT-related genes such as CDH1, ZEB family, and the microRNA-200 family. Overexpression of MEG3 influenced the expression of these genes and enhanced the effects of TGF-β in their expressions. Chromatin immunoprecipitation (ChIP) revealed that MEG3 regulated the recruitment of JARID2 and EZH2 and histone H3 methylation on the regulatory regions of CDH1 and microRNA-200 family genes for transcriptional repression. RNA immunoprecipitation and chromatin isolation by RNA purification assays indicated that MEG3 could associate with JARID2 and the regulatory regions of target genes to recruit the complex. This study demonstrated a crucial role of MEG3 lncRNA in the epigenetic regulation of the EMT process in lung cancer cells.

Long noncoding RNAs (lncRNAs) are important regulatory molecules in various biological and pathological processes, including cancer development. We have previously shown that the MEG3 lncRNA plays an essential role in transforming growth factor-β (TGF-β)-induced epithelial-mesenchymal transition (EMT) of human lung cancer cells. In this study, we investigated the function of another lncRNA, MEG8, which shares the DLK1–DIO3 locus with MEG3, in the regulation of EMT. MEG8 lncRNA expression was immediately induced during TGF-β–mediated EMT of A549 and LC2/ad lung cancer and Panc1 pancreatic cancer cell lines. MEG8 overexpression specifically suppressed the expression of microRNA-34a and microRNA-203 genes, resulting in up-regulation of Snail family transcriptional repressor 1 (SNAI1) and SNAI2 transcription factors, which repressed expression of Cadherin 1 (CDH1)/E-cadherin. Mechanistic investigations revealed that MEG8 associates with enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) protein and induces its recruitment to the regulatory regions of the two microRNA genes for histone H3 methylation and transcriptional repression. Interestingly, expression of both MEG8 and MEG3, but not each individually, could induce EMT-related cell morphological changes and increased cell motility in the absence of TGF-β by activating the gene expression program required for EMT. MEG8 knockdown indicated that endogenous MEG8 lncRNA is indispensable for TGF-β–induced EMT in A549 lung cancer and Panc1 pancreatic cancer cells. Our findings indicate that MEG8 lncRNA significantly contributes to epigenetic EMT induction and increase our understanding of the lncRNA-mediated regulatory mechanisms involved in malignant progression of cancer.

Histone methylation is implicated in various biological and pathological processes including cancer development. In this study, we discovered that ectopic expression of KDM5B, a histone H3 lysine 4 (H3K4) demethylase, promoted epithelial-mesenchymal transition (EMT) of cancer cells. KDM5B increased the expression of transcription factors, ZEB1 and ZEB2, followed by downregulation of E-cadherin and upregulation of mesenchymal marker genes. The expression of the microRNA-200 (miR-200) family, which specifically targets ZEB1 and ZEB2, was reduced in the cells with KDM5B overexpression. We found that KDM5B repressed the expression of the miR-200 family by changing histone H3 methylation status of their regulatory regions. The introduction of miR-200 precursor in the cells inhibited EMT induction by KDM5B, suggesting that miR-200 family was a critical downstream mediator of KDM5B-promoted EMT. Furthermore, knockdown of KDM5B was shown to affect the expression of EMT-related genes, indicating the involvement of endogenous KDM5B. Our study demonstrated a novel role of KDM5B histone lysine demethylase in EMT, which may contribute to malignant progression of cancer.

Histone methylation plays a crucial role in various biological and pathological processes including cancer development. In this study, we discovered that JARID2, an interacting component of Polycomb repressive complex-2 (PRC2) that catalyzes methylation of lysine 27 of histone H3 (H3K27), was involved in Transforming Growth Factor-beta (TGF-ß)-induced epithelial-mesenchymal transition (EMT) of A549 lung cancer cell line and HT29 colon cancer cell line. The expression of JARID2 was increased during TGF-ß-induced EMT of these cell lines and knockdown of JARID2 inhibited TGF-ß-induced morphological conversion of the cells associated with EMT. JARID2 knockdown itself had no effect in the expression of EMT-related genes but antagonized TGF-ß-dependent expression changes of EMT-related genes such as CDH1, ZEB family and microRNA-200 family. Chromatin immunoprecipitation assays showed that JARID2 was implicated in TGF-ß-induced transcriptional repression of CDH1 and microRNA-200 family genes through the regulation of histone H3 methylation and EZH2 occupancies on their regulatory regions. Our study demonstrated a novel role of JARID2 protein, which may control PRC2 recruitment and histone methylation during TGF-ß-induced EMT of lung and colon cancer cell lines.