Unknown,Transcriptomics,Genomics,Proteomics

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Intratumor heterogeneity of gene expression profiles in early stage non-small cell lung cancer (NSCLC)

ABSTRACT: Gene expression profiling of NSCLC tissues let to the establishment of several prognostic, predictive gene signatures with little overlap. To study factors introducing variability into gene expression microarray studies we compared interpatient (patient-to-patient) and intrapatient (tumor sub-sample) variations in gene expression profiles in stage I and II NSCLC tissues. We identified 128 probe sets which showed variable intratumoral expression Four different sites (A,B,C,D) of individual primary tumors and matched distant normal lung tissue (N) from 20 patients were used to establish gene expression patterns captured by Affymetrix HG-U133 Plus 2.0 arrays (n = 100).

ORGANISM(S): Homo sapiens

SUBMITTER: Michael Meister

PROVIDER: E-GEOD-33532 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:We have performed bioinformatic approaches to identify the level of enrichment between gene expression profiles characterizing MSI tumors and gene changes induced in vitro by the PARP-1 inhibitor Phenanthridinone and others using the Connectivity Map tool. In a first step, we have anyzed the expression of 300 colorectal cancers from the MECC study and generated a gene expression signature by microsatellite status. The criteria followed for selection of probe sets and detailed lists to be submitted subsequently to the Connectivity Map have been published previously by us in Clinical Cancer Research in 2009. In a second step, once we observed that deficiency in MRE11 exist among MSI tumors, our interest was focused on assessing if the homologous recombination pathway showed evidence of deregulation in MSI tumors. Therefore, we examined the expression levels of those genes integrated in the KEGG pathway hsa03440 using the previously generated gene expression data set. The dataset generated from our samples included a total of 300 colorectal fresh frozen tumors collected from the MECC study and were analyzed in two batches. The first batch was hybridized to the Affymetrix U133A chip and the second one to U133 Plus 2.0 (Supplementary Table S3). The final list of probe sets defining gene expression of MSI-H compared to MSS tumors was selected based on the strength of multiplicity adjusted P-values (cut-off P-value of < 0.001) and ratio of mean expression values across the two groups (cut-off Fold-change >1.3 and <0.7). It contained 442 upregulated and 480 downregulated probe sets. Then, MSI-H tumors present with changes in gene expression related to the homologous recombination pathway. Therefore, we examined the expression levels of those genes integrated in the KEGG pathway hsa03440 using the same data set. A total of 14 genes out of 30 were significantly differentially expressed in MSI-H compared to MSS tumors (Multiplicity adjusted Benjamini-Hochberg P-value<0.05). MRE11 and RAD50 probe sets showed a lower expression in MSI-H tumors and simultaneously other probe sets such as PARP-1 were significantly upregulated, probably secondary to the deficiency in the MRN complex proteins. This data provides evidence of significant differential expression of the homologous recombination pathway in MSI tumors.

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Intratumor heterogeneity of gene expression profiles in early stage non-small cell lung cancer (NSCLC)

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