Unknown,Transcriptomics,Genomics,Proteomics

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Oncogenic EGFR Represses the TET1 DNA Demethylase to Induce Silencing of Tumor Suppressors in Cancer Cells

ABSTRACT: Oncogene-induced DNA methylation-mediated transcriptional silencing of tumor suppressors frequently occurs in cancer, but the mechanism and functional role of this silencing in oncogenesis is not fully understood. Here, we show that oncogenic epidermal growth factor receptor (EGFR) induces silencing of multiple unrelated tumor suppressors in lung adenocarcinomas and glioblastomas by inhibiting DNA demethylase TET oncogene family member 1 (TET1) via the C/EBPÎ± transcription factor. After oncogenic EGFR inhibition, TET1 binds to tumor suppressor promoters and induces their re-expression via active DNA demethylation. Ectopic expression of TET1 potently inhibits lung and glioblastoma tumor growth, and TET1 knockdown confers resistance to EGFR inhibitors in lung cancer cells. Lung cancer samples exhibited reduced TET1 expression or TET1 cytoplasmic localization in a majority of cases. Collectively, these results identify a conserved pathway of oncogenic EGFR-induced DNA methylation-mediated transcriptional silencing of tumor suppressors, which may have therapeutic benefit for oncogenic EGFR-mediated lung cancers and glioblastomas. HCC827-Del (EGFR L747-S752) and HCC827-Del-TM (EGFR L747-S752/T790M) cell lines were treated with Decitibine (2.5 Î¼M) and Vorinostat (1Î¼M) or as a control cells that were treated with DMSO for 72 hrs. Expression profiling was performed using 3 biological replicates for each condition for a total of 12 samples analyzed.

ORGANISM(S): Homo sapiens

SUBMITTER: narendra wajapeyee

PROVIDER: E-GEOD-39292 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:EGFR tyrosine kinase inhibitors (TKIs) have demonstrated tremendous clinical benefits in non-small cell lung cancer (NSCLC) patients. However, resistance emerges rapidly due to a variety of mechanisms including a secondary mutation of T790M in EGFR that abrogates the binding of the drugs. It has been postulated that EGFR TKIs, such as afatinib (BIBW2992), with activity against the T790M mutant EGFR kinase might overcome the drug resistance problem or, when used as the first-line treatment, delay or suppress the emergence of resistance in EGFR. In this study, we generated BIBW2992-resistant cells, HCC827-BR1 and HCC827-BR2, from the parental HCC827 cells. In HCC827-BR cells, EGFR, MET, and Erb2 were down-regulated and no secondary mutation was found to be present in the coding region of EGFR. Gene set enrichment analysis (GSEA) revealed an obvious signature of epithelial to mesenchymal transition (EMT) in the drug resistant cells. Subsequently, the HCC827-BR cells were shown to be more invasive. Most importantly, we strived to seek if alternative medicine might be applied alone or in combination to treat the BIBW2992-resistant cells or to, under BIBW2992 treatment, diminish the emergence of resistant cells. Compared to the parental cells, the HCC827-BR cells were more sensitive to dasatinib, an FDA-approved kinase inhibitor. Furthermore, as revealed in the clonogenicity assay, the reduction of tumor-colony-forming cells after exposure to BIBW2992 was substantially potentiated by low concentration of dasatinib. Thus, prospective clinical investigations may be needed to evaluate if dasatinib can be beneficial to patients receiving second-generation EGFR TKIs for the treatment of NSCLC. Over a period of 3-4 months, BIBW2992-resistant cells were isolated in cell culture by maintenance of HCC827 cells in the presence of escalating concentrations of BIBW2992 up to 2 Î¼M. Two cell lines, HCC827-BR1 and HCC827-BR2, were established based on individual clones. Total RNA of these HCC827, HCC827-BR1 and HCC827-BR2, were extracted for gene expression microarray analysis using Illumina HumanHT12 v3 BeadChip.

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Oncogenic EGFR Represses the TET1 DNA Demethylase to Induce Silencing of Tumor Suppressors in Cancer Cells

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