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DNA methylation profiling of malignant pleural mesothelioma

ABSTRACT: Diagnosis of malignant pleural mesothelioma (MPM) is a challenging task because of its overlap with other neoplasms or even reactive conditions. Recently, DNA methylation analysis proved to be an effective tool for tumor diagnosis. We thus set out to test this approach for MPM diagnosis. A discovery (n=33) and an independent validation cohort (n=46) of MPM samples were subjected to array-based DNA methylation analyses and their DNA methylation patterns were compared to a representative set of both malignant and benign diagnostic mimics. By both unsupervised hierarchical clustering and t-distributed stochastic neighbor embedding analysis, MPM samples of the discovery cohort exhibited a distinct DNA methylation profile, different from that of other neoplastic and reactive mimics.

ORGANISM(S): Homo sapiens

PROVIDER: GSE164269 | GEO | 2021/03/20

REPOSITORIES: GEO

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Project description:Malignant Pleural Mesothelioma (MPM) is an aggressive cancer that is often diagnosed at an advanced stage and is characterized by a long latency period (20-40 years between initial exposure and diagnosis) and prior exposure to asbestos. Currently accurate diagnosis of MPM is difficult due to the lack of sensitive biomarkers, and despite minor improvements in treatment, median survival rates do not exceed 12 months. Accumulating evidence suggests that aberrant expression of long non-coding RNAs (lncRNAs) play an important functional role in cancer biology. LncRNAs are a class of recently discovered non-protein coding RNAs >200 nucleotides in length with a role in regulating transcription. Here we used NCode long noncoding microarrays to identify differentially expressed lncRNAs potentially involved in MPM pathogenesis. High priority candidate lncRNAs were selected on the basis of statistical (P<0.05) and biological significance (>3-fold difference). Expression levels of 9 candidate lncRNAs were technically validated using RT-qPCR, and biologically validated in three independent test sets: (1) 57 archived MPM tissues obtained from extrapleural pneumonectomy patients, (2) 15 cryopreserved MPM and 3 benign pleura, and (3) an extended panel of 10 MPM cell lines. RT-qPCR analysis demonstrated consistent up-regulation of these lncRNAs in independent datasets. ROC curve analysis showed that two candidates were able to separate benign pleura and MPM with high sensitivity and specificity, and were associated with nodal metastases and survival following induction chemotherapy. These results suggest that lncRNAs have potential to serve as biomarkers in MPM. To identify mRNA and lncRNA biomarkers associated with malignant pleural mesothelioma (MPM), we performed gene expression array analysis on 4 MPM cell lines (H28, MM05, MSTO-211H, H226) compared to the immortalised mesothelial line (MeT-5A). All cell lines were profiled in duplicate. Synthesis of the labelled first strand cDNA was conducted using the Superscript Plus Direct cDNA labeling system with starting material of 10ug total RNA. The labeled dNTP mix was added to the reaction to generate labeled second strand cDNA. Following the hydrolysis reaction, single-stranded cDNA was purified using low elution volume spin cartridges included in the purification module. Samples were labelled using Alexa Fluor 555 dyes. Samples were then hybridised to NCode Long Noncoding RNA Microarrays. Slides were scanned using an Agilent Scanner. Genes differentially expressed between Met-5A and the MPM cell lines were identified on the basis of P-value and fold change.

Project description:Malignant pleural mesothelioma (MPM) is a highly lethal, poorly understood neoplasm that is typically associated with asbestos exposure. We performed transcriptional profiling using high-density oligonucleotide microarrays containing approximately 22,000 genes to elucidate potential molecular and pathobiological pathways in MPM using discarded human MPM tumor specimens (n=40), normal lung specimens (n=4), normal pleura specimens (n=5), and MPM and SV40-immortalized mesothelial cell lines (n=5). In global expression analysis using unsupervised clustering techniques, we found two potential subclasses of mesothelioma which correlate loosely with tumor histology. We also identified sets of genes with expression levels that distinguish between multiple tumor subclasses, normal and tumor tissues, and tumors with different morphologies. Microarray gene expression data were confirmed using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and protein analysis for three novel candidate oncogenes (NME2, CRI1, and PDGFC) and one candidate tumor suppressor (GSN). Finally, we used bioinformatics tools (i.e. software) to create and explore complex physiological pathways that may be relevant in mesothelioma tumorigenesis, pathobiology, or both. Tissues and cell lines profiled using microarrays. Discarded MPM surgical specimens (n=40), normal pleura specimens (n=5), and normal lung specimens (n=4) were freshly collected (and snap frozen) from patients who underwent surgery at Boston's Brigham and Women's Hospital (BWH) between October 1998 and August 2000. All of these patients underwent extrapleural pneumonectomy with heated intra-pleural cisplatin chemotherapy delivered after the specimens were removed. All normal specimens were obtained from patients who were never diagnosed with MPM. Two human MPM cell lines (MS589 and MS428) were kindly provided by Jonathan A. Fletcher, M.D., Department of Pathology, BWH. The JMN1B MPM cell line19,20 has been described previously. The SV40-immortalized, non-tumorigenic mesothelial cell line (Met-5A)21 and the MPM cell line MSTO-211H22 were purchased from the American Type Culture Collection. Normal tissues were obtained from additional consented patients undergoing treatment for diseases other than MPM. All MPM samples used in these studies contained relatively pure tumor (greater than 50% tumor cells per high power field examined in a section adjacent to the tissue used). The microscopic slides from the patients' resection specimens were reviewed by one of the authors (J.G.), and the diagnosis and histologic subclassification of MPM confirmed in all cases. Linked clinical and pathological data were obtained for all patients who contributed tumor specimens. Specimens and data were rendered anonymous to protect patient confidentiality. Studies utilizing human tissues were approved by and conducted in accordance with the policies of the Institutional Review Board at BWH.

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DNA methylation profiling of malignant pleural mesothelioma

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