Unknown,Transcriptomics,Genomics,Proteomics

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Exome and whole genome sequencing of esophageal adenocarcinoma identifies recurrent driver events and mutational complexity

ABSTRACT: The incidence of esophageal adenocarcinoma (EAC) has risen 600% over the last 30 years. With an extremely poor five-year survival rate of only 15%, identification of new therapeutic targets for EAC is of great importance. Here, we analyze the mutation spectra from the whole exome sequencing of 149 EAC tumors/normal pairs, 15 of which have also been subjected to whole genome sequencing. We identify a novel mutational signature in EACs defined by a high prevalence of A to C transversions at Ap*A dinucleotides. Statistical analysis of the exome data identified 26 genes that are mutated at a significant frequency. Of these 26 genes, only four (TP53, CDKN2A, SMAD4, and PIK3CA) have been previously implicated in EAC. The novel significantly mutated genes include several chromatin modifying factors and candidate contributors to EAC: SPG20, TLR4, ELMO1, and DOCK2. Notably, functional analyses of EAC-derived mutations in ELMO1 increase cellular invasion. Therefore, we suggest a new hypothesis about the potential activation of the RAC1 pathway to be a contributor to EAC tumorigenesis. The study aimed to analyze 150 primary, human esophageal adenocarcinoma samples by whole genome and whole exome sequencing (which will be deposited to dbGAP following the TCGA practice). RNA expression data was used to determine gene expression in 14 of the samples analyzed by whole genome sequencing. No normals were analyzed.

ORGANISM(S): Homo sapiens

SUBMITTER: Shouyong Peng

PROVIDER: E-GEOD-42363 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Esophageal adenocarcinoma (EAC) has become a major concern in Western countries due to rapid rises in incidence coupled with very poor survival rates. One of the key risk factors for the development of this cancer is the presence of Barrett’s esophagus (BE), which is believed to form in response to repeated gastro-esophageal reflux. In this study we performed comparative, genome-wide expression profiling (using Illumina whole-genome Beadarray) on total RNA extracted from esophageal biopsy tissues from individuals with EAC, BE (in the absence of EAC) and those with normal squamous epithelium. We combined these data with publically accessible raw data from three similar studies to investigate key gene and ontology differences between these three tissue states. The results support the deduction that BE is a tissue with enhanced glycoprotein synthesis machinery (DPP4, ATP2A3, AGR2) designed to provide strong mucosal defenses aimed at resisting gastro-esophageal reflux. EAC exhibits the enhanced extracellular matrix remodeling (collagens, IGFBP7, PLAU) effects expected in an aggressive form of cancer, as well as evidence of reduced expression of genes associated with mucosal (MUC6, CA2, TFF1) and xenobiotic (AKR1C2, AKR1B10) defenses. When our results are compared to previous whole-genome expression profiling studies keratin, mucin, annexin and trefoil factor gene families are the most frequently represented gene families. Eleven genes identified here are also represented in at least 3 other profiling studies. We used these genes to discriminate squamous, BE and EAC within the two largest cohorts using a support vector machine leave one out cross validation analysis. While this method was satisfactory for discriminating squamous and BE, it demonstrates the need for more detailed investigations into profiling changes within BE leading to the progression towards EAC. A comparison of three esophageal biopsy groups from separate individuals: normal squamous (n=9), Barrett's esophagus without dysplasia (n=22) & adenocarcinoma (n=23). Adenocarcinoma samples overlap with members of DNA copy number analysis GEO series GSE10506 such that, in each case genomic DNA and total RNA were extracted from the same biopsy. The matching copy number data GEO samples IDs are noted in characteristics: Matching CN Sample ID

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Exome and whole genome sequencing of esophageal adenocarcinoma identifies recurrent driver events and mutational complexity

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