Dataset Information

Uncovering Driver DNA Methylation Events in Nonsmoking Early Stage Lung Adenocarcinoma.

ABSTRACT: As smoking rates decrease, proportionally more cases with lung adenocarcinoma occur in never-smokers, while aberrant DNA methylation has been suggested to contribute to the tumorigenesis of lung adenocarcinoma. It is extremely difficult to distinguish which genes play key roles in tumorigenic processes via DNA methylation-mediated gene silencing from a large number of differentially methylated genes. By integrating gene expression and DNA methylation data, a pipeline combined with the differential network analysis is designed to uncover driver methylation genes and responsive modules, which demonstrate distinctive expressions and network topology in tumors with aberrant DNA methylation. Totally, 135 genes are recognized as candidate driver genes in early stage lung adenocarcinoma and top ranked 30 genes are recognized as driver methylation genes. Functional annotation and the differential network analysis indicate the roles of identified driver genes in tumorigenesis, while literature study reveals significant correlations of the top 30 genes with early stage lung adenocarcinoma in never-smokers. The analysis pipeline can also be employed in identification of driver epigenetic events for other cancers characterized by matched gene expression data and DNA methylation data.

SUBMITTER: Zhang X

PROVIDER: S-EPMC5005773 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Uncovering Driver DNA Methylation Events in Nonsmoking Early Stage Lung Adenocarcinoma.

Zhang Xindong X Gao Lin L Liu Zhi-Ping ZP Jia Songwei S Chen Luonan L

BioMed research international 20160817

As smoking rates decrease, proportionally more cases with lung adenocarcinoma occur in never-smokers, while aberrant DNA methylation has been suggested to contribute to the tumorigenesis of lung adenocarcinoma. It is extremely difficult to distinguish which genes play key roles in tumorigenic processes via DNA methylation-mediated gene silencing from a large number of differentially methylated genes. By integrating gene expression and DNA methylation data, a pipeline combined with the differenti ...[more]

PMID: 27610367

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Project description:BackgroundEarly-stage female lung adenocarcinoma is the most common type of lung cancer encountered in thoracic surgery departments. Tumor-node-metastasis (TNM) staging does not adequately explain a significant stratification phenomenon in the prognosis of patients with stage I lung adenocarcinoma. We aimed to investigate the contributory role of miR-940 in the prognosis prediction.MethodsWe analyzed the microRNA (miRNA) expression level in tumor tissues (high-risk group vs. low-risk group) from 12 non-smoking female patients with stage I lung adenocarcinoma using miRNA array. Bioinformatic analyses of miR-940 were also carried out based on the public database. Then, quantitative reverse-transcription polymerase chain reaction (qRT-PCR) tests of the tissue samples were further validated. And miR-940's function was analyzed and potential target genes were predicted.ResultsIn all, 24 miRNAs were found to be significantly different between the high-risk group and low-risk group. The expression level of miR-940 was lower in tumor tissue (P=0.011), and the survival rate in the high miR-940 group was higher [hazard ratio (HR) =0.688; P=0.011]. Gene Ontology (GO) analysis showed that the assembly functions of targets regulated by miR-940 were mainly enriched in regulation of myeloid cell differentiation, G1/S transition of mitotic cell cycle, and cellular response to environmental stimulus. miR-940 is involved in transforming growth factor-beta (TGF-beta) signaling pathway; TNF signaling pathway; and estrogen signaling pathway. The number of lung adenocarcinoma cells (A549) was significantly decreased after miR-940 was transfected. Ten epithelial-to-mesenchymal-transition (EMT)-associated genes (MMP9, ZEB1, CDH1, KRT8, KRT18 KET19, TWIST1, VIM, SNAI1, and SNAI2) were found to be significantly related to miR-940.ConclusionsThe present study showed that miR-940 might be a protective factor for positive prognosis in early stage nonsmoking female lung adenocarcinoma, with transforming growth factor-beta (TGF-beta) pathway, TNF pathway, and matrix metalloprotein (MMP9) being potential targets.

Project description:BackgroundEarly-stage lung cancers radiologically manifested as ground-glass opacities (GGOs) have been increasingly identified, among which pure GGO (pGGO) has a good prognosis after local resection. However, the optimal surgical margin is still under debate. Precancerous lesions exist in tumor-adjacent tissues beyond the histological margin. However, potential precancerous epigenetic variation patterns beyond the histological margin of pGGO are yet to be discovered and described.ResultsA genome-wide high-resolution DNA methylation analysis was performed on samples collected from 15 pGGO at tumor core (TC), tumor edge (TE), para-tumor tissues at the 5 mm, 10 mm, 15 mm, 20 mm beyond the tumor, and peripheral normal (PN) tissue. TC and TE were tested with the same genetic alterations, which were also observed in histologically normal tissue at 5 mm in two patients with lower mutation allele frequency. According to the difference of methylation profiles between PN samples, 2284 methylation haplotype blocks (MHBs), 1657 differentially methylated CpG sites (DMCs), and 713 differentially methylated regions (DMRs) were identified using reduced representation bisulfite sequencing (RRBS). Two different patterns of methylation markers were observed: Steep (S) markers sharply changed at 5 mm beyond the histological margin, and Gradual (G) markers changed gradually from TC to PN. S markers composed 86.2% of the tumor-related methylation markers, and G markers composed the other 13.8%. S-marker-associated genes enriched in GO terms that were related to the hallmarks of cancer, and G-markers-associated genes enriched in pathways of stem cell pluripotency and transcriptional misregulation in cancer. Significant difference in DNA methylation score was observed between peripheral normal tissue and tumor-adjacent tissues 5 mm further from the histological margin (p < 0.001 in MHB markers). DNA methylation score at and beyond 10 mm from histological margin is not significantly different from peripheral normal tissues (p > 0.05 in all markers).ConclusionsAccording to the methylation pattern observed in our study, it was implied that methylation alterations were not significantly different between tissues at or beyond P10 and distal normal tissues. This finding explained for the excellent prognosis from radical resections with surgical margins of more than 15 mm. The inclusion of epigenetic characteristics into surgical margin analysis may yield a more sensitive and accurate assessment of remnant cancerous and precancerous cells in the surgical margins.

Dataset Information

Uncovering Driver DNA Methylation Events in Nonsmoking Early Stage Lung Adenocarcinoma.

Publications

Uncovering Driver DNA Methylation Events in Nonsmoking Early Stage Lung Adenocarcinoma.

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