Dataset Information

Estrogen induces global reorganization of chromatin structure in human breast cancer cells.

ABSTRACT: In the cell nucleus, each chromosome is confined to a chromosome territory. This spatial organization of chromosomes plays a crucial role in gene regulation and genome stability. An additional level of organization has been discovered at the chromosome scale: the spatial segregation into open and closed chromatins to form two genome-wide compartments. Although considerable progress has been made in our knowledge of chromatin organization, a fundamental issue remains the understanding of its dynamics, especially in cancer. To address this issue, we performed genome-wide mapping of chromatin interactions (Hi-C) over the time after estrogen stimulation of breast cancer cells. To biologically interpret these interactions, we integrated with estrogen receptor ? (ER?) binding events, gene expression and epigenetic marks. We show that gene-rich chromosomes as well as areas of open and highly transcribed chromatins are rearranged to greater spatial proximity, thus enabling genes to share transcriptional machinery and regulatory elements. At a smaller scale, differentially interacting loci are enriched for cancer proliferation and estrogen-related genes. Moreover, these loci are correlated with higher ER? binding events and gene expression. Taken together these results reveal the role of a hormone--estrogen--on genome organization, and its effect on gene regulation in cancer.

SUBMITTER: Mourad R

PROVIDER: S-EPMC4255042 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Estrogen induces global reorganization of chromatin structure in human breast cancer cells.

Mourad Raphaël R Hsu Pei-Yin PY Juan Liran L Shen Changyu C Koneru Prasad P Lin Hai H Liu Yunlong Y Nephew Kenneth K Huang Tim H TH Li Lang L

PloS one 20141203 12

In the cell nucleus, each chromosome is confined to a chromosome territory. This spatial organization of chromosomes plays a crucial role in gene regulation and genome stability. An additional level of organization has been discovered at the chromosome scale: the spatial segregation into open and closed chromatins to form two genome-wide compartments. Although considerable progress has been made in our knowledge of chromatin organization, a fundamental issue remains the understanding of its dyna ...[more]

PMID: 25470140

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Project description:In the cell nucleus, each chromosome is confined to a chromosome territory. This spatial organization of chromosomes plays a crucial role in gene regulation and genome stability. Recently an additional level of organization has been discovered at the chromosome scale: the spatial segregation into open and closed chromatin to form two genome-wide compartments. Although considerable progress has been made in our knowledge of chromatin organization, a fundamental issue remains the understanding of its dynamic, especially in cancer. To address this issue, we performed genome-wide mapping of intra- and interchromosomal interactions (Hi-C) over the time after estrogen (E2) stimulation of breast cancer cells. To biologically interpret these interactions, we integrated with estrogen receptor alpha (ER alpha) binding events, gene expression and multiple epigenetic marks. We show that E2 induces a global reorganization of genome. More specifically, gene-rich chromosomes as well as areas of open and highly transcribed chromatins are moved spatially closer, thus enabling genes to share transcriptional machinery and regulatory elements. At a lower scale, differentially interacting loci are enriched for cancer proliferation and E2 related genes. We also observe that these differentially interacting loci are correlated with higher ER alpha binding events and gene expression. 5 time points: before E2 (0h) and after E2 (0.5h, 1h, 4h and 24h). For each time point, there are two lanes per sample and two biological replicate samples. Please note that a processed data file corresponds to the merging of 2 replicates, and that there are 2 lanes per replicates (4 files in total per processed data file). Information about data merging is provided in the title of the sample. For instance : 0h_replicate_1_lane 1 0h_replicate_1_lane 2 0h_replicate_2_lane_1 0h_replicate_2_lane_2 are merged to generate the processed data hic_0h-all-1M.IC.csv.gz. Several bin sizes are provided for the same processed data: hic_0h-all-1M.IC.csv.gz hic_0h-all-2M.IC.csv.gz hic_0h-all-4M.IC.csv.gz hic_0h-all-500k.IC.csv.gz are the same processed data, but with different bin sizes.

Project description:We propose the hypothesis that loss of estrogen receptor function which leads to endocrine resistance in breast cancer, also results in trans-differentiation from an epithelial to a mesenchymal phenotype that is responsible for increased aggressiveness and metastatic propensity. siRNA mediated silencing of the estrogen receptor in MCF7 breast cancer cells resulted in estrogen/tamoxifen resistant cells (pII) with altered morphology, increased motility with rearrangement and switch from a keratin/actin to a vimentin based cytoskeleton, and ability to invade simulated components of the extracellular matrix. Phenotypic profiling using an Affymetrix Human Genome U133 plus 2.0 GeneChip indicated geometric fold changes ≥ 3 in approximately 2500 identifiable unique sequences, with about 1270 of these being up-regulated in pII cells. Changes were associated with genes whose products are involved in cell motility, loss of cellular adhesion and interaction with the extracellular matrix. Selective analysis of the data also showed a shift from luminal to basal cell markers and increased expression of a wide spectrum of genes normally associated with mesenchymal characteristics, with consequent loss of epithelial specific markers. Over-expression of several peptide growth factors and their receptors are indicative of an increased contribution to the higher proliferative rates of pII cells as well as aiding their potential for metastatic activity. Signalling molecules that have been identified as key transcriptional drivers of epithelial to mesenchymal transition were also found to be elevated in pII cells. These data support our hypothesis that induced loss of estrogen receptor in previously estrogen/antiestrogen sensitive cells is a trigger for the concomitant loss of endocrine dependence and onset of a series of possibly parallel events that changes the cell from an epithelial to a mesenchymal type. Inhibition of this transition through targeting of specific mediators may offer a useful supplementary strategy to circumvent the effects of loss of endocrine sensitivity.

Project description:In laboratory studies, acquired resistance to long-term antihormonal therapy in breast cancer evolves through two phases over 5 y. Phase I develops within 1 y, and tumor growth occurs with either 17?-estradiol (E(2)) or tamoxifen. Phase II resistance develops after 5 y of therapy, and tamoxifen still stimulates growth; however, E(2) paradoxically induces apoptosis. This finding is the basis for the clinical use of estrogen to treat advanced antihormone-resistant breast cancer. We interrogated E(2)-induced apoptosis by analysis of gene expression across time (2-96 h) in MCF-7 cell variants that were estrogen-dependent (WS8) or resistant to estrogen deprivation and refractory (2A) or sensitive (5C) to E(2)-induced apoptosis. We developed a method termed differential area under the curve analysis that identified genes uniquely regulated by E(2) in 5C cells compared with both WS8 and 2A cells and hence, were associated with E(2)-induced apoptosis. Estrogen signaling, endoplasmic reticulum stress (ERS), and inflammatory response genes were overrepresented among the 5C-specific genes. The identified ERS genes indicated that E(2) inhibited protein folding, translation, and fatty acid synthesis. Meanwhile, the ERS-associated apoptotic genes Bcl-2 interacting mediator of cell death (BIM; BCL2L11) and caspase-4 (CASP4), among others, were induced. Evaluation of a caspase peptide inhibitor panel showed that the CASP4 inhibitor z-LEVD-fmk was the most active at blocking E(2)-induced apoptosis. Furthermore, z-LEVD-fmk completely prevented poly (ADP-ribose) polymerase (PARP) cleavage, E(2)-inhibited growth, and apoptotic morphology. The up-regulated proinflammatory genes included IL, IFN, and arachidonic acid-related genes. Functional testing showed that arachidonic acid and E(2) interacted to superadditively induce apoptosis. Therefore, these data indicate that E(2) induced apoptosis through ERS and inflammatory responses in advanced antihormone-resistant breast cancer.

Dataset Information

Estrogen induces global reorganization of chromatin structure in human breast cancer cells.

Publications

Estrogen induces global reorganization of chromatin structure in human breast cancer cells.

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