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Whole DNA methylome profiling in lung cancer cells before and after epithelial-to-mesenchymal transition.

ABSTRACT: Metastatic lung cancer is one of the leading causes of cancer death. In recent years, epithelial-to-mesenchymal transition (EMT) has been found to contribute to metastasis, as it enables migratory and invasive properties in cancer cells. Previous genome-wide studies found that DNA methylation was unchanged during EMT induced by TGF-? in AML12 cells. In this study, we aimed to discover EMT-related changes in DNA methylation in cancer cells, which are poorly understood.We employed a next-generation sequencing-based method, MSCC (methyl-sensitive cut counting), to investigate DNA methylation during EMT in the A549 lung cancer cell line.We found that methylation levels were highly correlated to gene expression, histone modifications and small RNA expression. However, no differentially methylated regions (DMRs) were found in A549 cells treated with TGF-? for 4 h, 12 h, 24 h and 96 h. Additionally, CpG islands (CGIs) showed no overall change in methylation levels, and at the single-base level, almost all of the CpGs showed conservation of DNA methylation levels. Furthermore, we found that the expression of DNA methyltransferase 1, 3a, 3b (DNMT1, DNMT3a, DNMT3b) and ten-eleven translocation 1 (TET1) was altered after EMT. The level of several histone methylations was also changed.DNA methylation-related enzymes and histone methylation might have a role in TGF-?-induced EMT without affecting the whole DNA methylome in cancer cells. Our data provide new insights into the global methylation signature of lung cancer cells and the role of DNA methylation in EMT.The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1112892497119603.

SUBMITTER: Liu F

PROVIDER: S-EPMC4108085 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Whole DNA methylome profiling in lung cancer cells before and after epithelial-to-mesenchymal transition.

Liu Fatao F Zhou Yi Y Zhou Daizhan D Kan Mengyuan M Niu Xiaomin X Zhang Zhou Z Zhang Di D Tao Liming L He Lin L Zhan Lixing L Liu Yun Y

Diagnostic pathology 20140320

<h4>Background</h4>Metastatic lung cancer is one of the leading causes of cancer death. In recent years, epithelial-to-mesenchymal transition (EMT) has been found to contribute to metastasis, as it enables migratory and invasive properties in cancer cells. Previous genome-wide studies found that DNA methylation was unchanged during EMT induced by TGF-β in AML12 cells. In this study, we aimed to discover EMT-related changes in DNA methylation in cancer cells, which are poorly understood.<h4>Metho ...[more]

PMID: 24655585

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Project description:Epithelial-mesenchymal transition (EMT) is an important process in embryonic development, especially during gastrulation and organ formation. Furthermore EMT is widely observed in pathological conditions, e.g., fibrosis, tumor progression and metastasis. Madin-Darby Canine Kidney (MDCK) cells are widely used for studies of EMT and epithelial plasticity. MDCK cells show an epithelial phenotype, while oncogenic Ras-transformed MDCK (MDCK-Ras) cells undergo EMT and show a mesenchymal phenotype.RNA-Seq and miRNA-Seq analyses were performed on MDCK and MDCK-Ras cells. Data were validated by qRT-PCR. Gene signature analyses were carried out to identify pathways and gene ontology terms. For selected miRNAs target prediction was performed.With RNA-Seq, mRNAs of approximately half of the genes known for dog were detected. These were screened for differential regulation during Ras-induced EMT. We went further and performed gene signature analyses and found Gene Ontology (GO) terms and pathways important for epithelial polarity and implicated in EMT. Among the identified pathways, TGF?1 emerged as a central signaling factor in many EMT related pathways and biological processes. With miRNA-Seq, approximately half of the known canine miRNAs were found expressed in MDCK and MDCK-Ras cells. Furthermore, among differentially expressed miRNAs, miRNAs that are known to be important regulators of EMT were detected and new candidates were predicted. New dog miRNAs were discovered after aligning our reads to that of other species in miRBase. Importantly, we could identify 25 completely novel miRNAs with a stable hairpin structure. Two of these novel miRNAs were differentially expressed. We validated the two novel miRNAs with the highest read counts by RT-qPCR. Target prediction of a particular novel miRNA highly expressed in mesenchymal MDCK-Ras cells revealed that it targets components of epithelial cell junctional complexes. Combining target prediction for the most upregulated miRNAs and validation of the targets in MDCK-Ras cells with pathway analysis allowed us to identify two novel pathways, e.g., JAK/STAT signaling and pancreatic cancer pathways. These pathways could not be detected solely by gene set enrichment analyses of RNA-Seq data.With deep sequencing data of mRNAs and miRNAs of MDCK cells and of Ras-induced EMT in MDCK cells, differentially regulated mRNAs and miRNAs are identified. Many of the identified genes are within pathways known to be involved in EMT. Novel differentially upregulated genes in MDCK cells are interferon stimulated genes and genes involved in Slit and Netrin signaling. New pathways not yet linked to these processes were identified. A central pathway in Ras induced EMT is TGF? signaling, which leads to differential regulation of many target genes, including miRNAs. With miRNA-Seq we identified miRNAs involved in either epithelial cell biology or EMT. Finally, we describe completely novel miRNAs and their target genes.

Project description:BackgroundLung cancer is the most common and lethal malignancy worldwide. TCTP is highly expressed in various cancers including lung cancer. Epithelial-mesenchymal transition (EMT) could increase cancer cell invasion. Whether TCTP's expression is associated with EMT in lung adenocarcinoma is largely unknown.MethodsSeveral Gene Expression Omnibus datasets were used to analyze the correlation between TCTP expression and overall survival of lung adenocarcinoma patients by Kaplan-Meier survival analysis. Then, 24 surgically removed fresh lung adenocarcinoma tissue samples and paired paracancer tissue samples were used to analyze the correlation between TCTP expression and tumor stage by immunohistochemical analysis. Furthermore, stable cell lines were generated using lentiviral transduction systems to knock down or overexpress TCTP in A549 cells. Cell migration and invasion were measured by scratch and transwell assays, and EMT marker proteins such as α-SMA, ZEB1, and E-cadherin were quantitated by Western blot. The expression levels of miR-200a, miR-141, and miR-429 were determined by real-time quantitative PCR, and their target genes were predicted by an online database miRTarBase. The interaction between TCTP and these genes was analyzed by String database and visualized by Cytoscape.ResultsTCTP was highly expressed in tumor tissues compared to paracancer tissues. The expression of TCTP was associated with shorter overall survival. TCTP knockdown experiment in A549 cells suggested that TCTP knockdown could decrease the migration and invasion of lung cancer cells, and the expression level of ZEB1 and α-SMA, but increase the expression of E-cadherin and p53. Vice versa, overexpression of TCTP could increase the migration and invasion of cancer cells, and the expression level of ZEB1 and α-SMA, but decrease the expression of E-cadherin and p53. Furthermore, we found the expression of miR-200a, miR-141, and miR-429 was associated with TCTP expression.ConclusionTCTP promotes EMT in lung adenocarcinoma, and this effect may be associated with miR-200 family members like miR-200a, miR-141, and miR-429.

Dataset Information

Whole DNA methylome profiling in lung cancer cells before and after epithelial-to-mesenchymal transition.

Publications

Whole DNA methylome profiling in lung cancer cells before and after epithelial-to-mesenchymal transition.

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