Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Characterization of HCT8 clones with MDR phenotype.

ABSTRACT: We selected and characterized doxorubicin/5FU resistant HCT-8/R clones from sensitive parental cells, analyzing several parameters: cell cycle phase distribution, apoptotic activity, expression, distribution and functionality of the P-gp efflux pump, ultrastructural features, invasiveness and transcriptomic profiles.

ORGANISM(S): Homo sapiens

SUBMITTER: Cristina Luceri

PROVIDER: E-MTAB-3780 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:We explored the combinatorial interactions between p53, estrogen receptors and NFkB using the breast adenocarcinoma-derived MCF7 cells. Recently, we have established that p53 can modulate transcription also through non-canonical response elements (REs), consisting of half-sites and ¾ sites. In particular, we identified a half-site p53 response element in the promoter of FLT1/VEGFR-I gene that was required but not sufficient for the p53 responsiveness of the promoter. The transcriptional control required also estrogen receptor (ER) half-sites (EREs) located in close proximity to the p53 RE. Further studies led us to establish that p53-mediated transcription from the FLT1 half site RE is dependent on ER binding at the EREs and strongly influenced by the level of ER proteins, and the specific nature of the p53-inducing stress as well as ER ligand. In another study we found an enrichment of NFkB REs nearby p53 REs in p53 target genes, suggesting an additional mode of functional interactions between these two transcription factors. To identify at a genome scale the transcriptional network that selectively responds to the concomitant activation of p53, ER and/or NFkB, we measured gene expression upon treatment with specific chemotherapeutic agents combined with 17-β estradiol (E2) and/or the inflammatory cytokine TNFα. Firstly we measured using MCF7 cells growing in estrogen-depleted media the transcriptome changes induced by doxorubicin (doxo) and 5-fluorouracil (5FU), two different drugs both able to stabilize and activate the p53 protein. We next obtained the expression profiles in the presence of E2 with or without doxo or 5FU. We also measured transcriptome changes in response to TNFαalone or in combination with doxo and/or E2. All these analyses were conducted using the same batch of MCF7 cells (wild type for p53, ERα, ERβ -weakly-, and NFkB positive) that we had previously used to characterize the cis-mediated transcriptional cooperation between p53 and ER at the FLT1 gene. Keywords: transcription factor, transcriptional networks, p53, ER, NFkB, p53-ER-NFkB crosstalk, doxorubicin, 5-fluorouracil, 17-β estradiol, TNFα, combined genotoxic, estrogenic and inflammatory responses, composite DNA binding site signatures, MCF7. The cooperation at the transcriptional level among p53, ERs and NFkB was analyzed by transcriptome analysis in response to different stimuli (doxo or 5FU, E2, TNFα). To identify mRNA molecules that would be modulated by the coordinated activity of the three TFs, gene expression signals derived from the combinatorial treatment were compared by microarrays analyses to those obtained from each drug when individually administered. Total RNA was isolated from MCF7 cells grown in estrogen-depleted medium and treated so as to stimulate the activity of the three different transcription factors (p53, ERs and NFkB). Cells lysates were collected after 10 hours from the treatments. All experiments were run from triplicate to septuples.

Project description:We investigated the influence of genome position on propensity to amplify. First, we integrated a mutant form of DHFR into different positions in the human genome, challenged cells with methotrexate and then studied the genomic alterations arising in drug resistant cells. We observed site specific differences in methotrexate sensitivity, organization of amplicons and amplification frequency. One site was uniquely associated with a significantly enhanced propensity to amplify and recurrent amplicon boundaries, possibly implicating a rare folate sensitive fragile site in initiating amplification. Hierarchical clustering of gene expression patterns and subsequent gene enrichment analysis revealed two clusters differing significantly in expression of MYC target genes independent of integration site. We introduced a mutant form of DHFR (L22F), which confers greater resistance to methotrexate than the wild type (endogenous) gene into HCT116+chr3 cells and isolated independent clones containing DHFR* at different positions in the genome and identified genome sequences flanking the integration site of DHFR* using inverse PCR. For further analysis, we selected only clones, which were considered to have a single insertion of DHFR* by inverse PCR (13 independent insertion sites). The individual insertion site clones were further characterized with respect to genome copy number profiles. To select methotrexate resistant colonies, we exposed cells to a concentration of methotrexate that was three to four times the IC-50 for each integration site. Genomic copy number profiles were obtained for isolated resistant colonies (GSE6262) by using UCSF HumArray platform (GPL4421). Twelve methotrexate resistant colonies (four different integration sites) were selected for microarray analysis of gene expression at the mRNA level. The untreated integration site clone was used as the reference (Cy5 labeled cDNA) for each of the hybridizations with its respective resistant colonies (Cy3 labeled cDNA). Hybridizations were carried out on arrays of printed long oligonucleotides (70mers) containing 21,000 elements (Operon V2.0, printed in J. David Gladstone Institutes, Genomics Core Laboratory).

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Characterization of HCT8 clones with MDR phenotype.

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