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Genetic and Epigenetic Somatic Alterations in Head and Neck Squamous Cell Carcinomas Are Globally Coordinated but Not Locally Targeted (GoldenGate methylation)

ABSTRACT: Solid tumors, including head and neck squamous cell carcinomas (HNSCC), arise as a result of genetic and epigenetic alterations in a sustained stress environment. Since it has been hypothesized that epigenetic alterations may act by providing the second carcinogenic hit in gene silencing, we sought to identify genome-wide DNA copy number alterations and CpG dinucleotide methylation events and examine the global/local relationships between these types of alterations in HNSCC. Importantly, we found that the global pattern of copy number alterations in these tumors was significantly associated with tumor methylation profiles. However at the local level, gene promoter regions did not exhibit a correlation between copy number and methylation , and the spectrum of genes affected by each type of alteration was unique. A case-series of 19 tumors and matched blood referents were hybrizided to Affymetrix Human Mapping 500k arrays and copy number was determined via HMM with Copy Number Analysis Tool v4.0.1.

ORGANISM(S): Homo sapiens

PROVIDER: GSE20742 | GEO | 2010/03/11

SECONDARY ACCESSION(S): PRJNA124985

REPOSITORIES: GEO

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Project description:Integrated profiling of somatic molecular alterations present in tumors is necessary to further our understanding of the tumorigenic process. We investigated the potential relationships between gene copy number alterations and DNA methylation profiles in a case series of pleural mesotheliomas (n=23). Gene copy number (CN) alterations profiled with 500K SNP arrays and DNA methylation measured at over 750 cancer-related genes with methylation bead-arrays were examined concomitantly. Considering each probed locus, there were no instances of significantly correlated CN alteration and methylation (no loci with Q < 0.05) and averaging loci over their associated genes revealed only two genes with significantly correlated CN and methylation alterations (Q < 0.04). In contrast to the lack of discrete correlations, the overall extent of tumor CN alteration was significantly associated with DNA methylation profile when comparing CN alteration extent among methylation profile classes (P < 0.02), and there was evidence that this association was partially attributable to prevalent allele loss observed at the maintenance DNA methyltransferase DNMT1. Taken together, this work indicates a strong association between global genetic and global epigenetic dysregulation in mesothelioma rather than a discrete, local coordination of gene inactivation, and further highlights the utility and necessity of integrative genomics approaches in cancer biology. From the total study population, 23 tumors from the incident case series were chosen for copy number alteration profiling by hybridizing 5ml containing â¥ 50ng/ml of tumor or matched peripheral blood DNA to each of the two GeneChipsÂ® that comprise the Human Mapping 500K single-nucleotide polymorphism array set (Affymetrix, Santa Clara, CA), following manufacturer protocols and standard operating procedures at the Harvard Partners Microarray Core servicing facility. Probe intensities at each locus were determined in the GCOS software and genotypes calls were generated using the Genotyping Analysis Software (Affymetrix). Probe signals were normalized to their matched referent peripheral blood sample data using the Copy Number Analysis Tool v4.0.1 software (CNAT) (Affymetrix) with median scaling and default tuning parameters, and copy number states were inferred by Hidden Markov Model analysis. The supplementary file 'GSE21057_tumor_copy_number.txt' contains the (blood-normalized) copy number calls for each tumor sample.

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Genetic and Epigenetic Somatic Alterations in Head and Neck Squamous Cell Carcinomas Are Globally Coordinated but Not Locally Targeted (GoldenGate methylation)

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