Genome-wide methylation and expression profiling study identifies candidate DNA methylation drivers of acquired cisplatin resistance in ovarian cancer.
ABSTRACT: This SuperSeries is composed of the following subset Series: GSE28646: Gene expression profiling in A2780, CP70 and CP70 following Decitabine and/or PXD101 treatment GSE28647: Genome-wide methylation profiling identifies candidate DNA methylation drivers of acquired cisplatin resistance in ovarian cancer. Refer to individual Series
Project description:Multiple DNA methylation changes have been associated with the acquisition of drug resistance; however it remains uncertain how many of these changes may represent critical DNA methylation drivers of chemoresistance. Using gene expression profiling method on HGU133plus2 array, we identified a total of 1370 genes showing significant gene expression changes with 687 genes going up and 683 genes going down in the resistant (cp70) versus sensitive cell lines (A2780) by Rank Product (FDR<5%). Combining expression profiling with methylation profiling data we found out of 245 hypermethylated and down-regulated genes in the resistant cell line, 41 genes were up-regulated following Decitabine treatment alone, 45 genes up-regulated following combined treatment of Decitabine and PXD101, and only 10 genes up-regulated following PXD101 treatment alone. Altogether we found a small set of genes as being potential key drivers of chemoresistance and should be further evaluated as predictive biomarkers, both to existing chemotherapies, but also to epigenetic therapies used to modulate drug resistance. Gene expression profiling was obtained from A2780, and CP70 before and after Decitabine and/or PXD101 treatment. Each sample have biological triplicates. Using Rank Product package in R (version 2.10.1), differentially expressed genes with FDR<5% were identified.
Project description:Epithelial ovarian cancer is the leading cause of death among gynecologic malignancies. Diagnosis usually occurs after metastatic spread, largely reflecting vague symptoms of early disease combined with lack of an effective screening strategy. Epigenetic mechanisms of gene regulation, including DNA methylation, are fundamental to normal cellular function and also play a major role in carcinogenesis. To elucidate the biological and clinical relevance of DNA methylation in ovarian cancer, we conducted expression microarray analysis of 43 cell lines and 17 primary culture specimens grown in the presence or absence of DNA methyltransferase (DNMT) inhibitors. Two parameters, induction of expression and standard deviation among untreated samples, identified 378 candidate methylated genes, many relevant to TGF-beta signaling. We analyzed 43 of these genes and they all exhibited methylation. Treatment with DNMT inhibitors increased TGF-beta pathway activity. Hierarchical clustering of ovarian cancers using the 378 genes reproducibly generated a distinct gene cluster strongly correlated with TGF-beta pathway activity that discriminates patients based on age. These data suggest that accumulation of age-related epigenetic modifications leads to suppression of TGF-beta signaling and contributes to ovarian carcinogenesis. The cancer stem cell hypothesis posits that malignant growth arises from a rare population of progenitor cells within a tumor that provide it with unlimited regenerative capacity. Such cells also possess increased resistance to chemotherapeutic agents. Resurgence of chemoresistant disease following primary therapy typifies epithelial ovarian cancer and may be attributable to residual cancer stem cells, or cancer initiating cells, that survive initial treatment. As the cell surface marker CD133 identifies cancer initiating cells in a number of other malignancies, we sought to determine the potential role of CD133+ cells in epithelial ovarian cancer. We detected CD133 on ovarian cancer cell lines, in primary cancers, and on purified epithelial cells from ascitic fluid of ovarian cancer patients. We found CD133+ ovarian cancer cells generate both CD133+ and CD133- daughter cells, whereas CD133- cells divide symmetrically. CD133+ cells exhibit enhanced resistance to platinum-based therapy, drugs commonly used as first line agents for treatment of ovarian cancer. Sorted CD133+ ovarian cancer cells also form more aggressive tumor xenografts at a lower inoculum than their CD133- progeny. Epigenetic changes may be integral to the behavior of cancer progenitor cells and their progeny. In this regard, we found that CD133 transcription is controlled by both histone modifications and promoter methylation. Sorted CD133- ovarian cancer cells treated with DNA methyltransferase and histone deacetylase inhibitors show a synergistic increase in cell surface CD133 expression. Moreover, DNA methylation at the ovarian tissue active P2 promoter is inversely correlated with CD133 transcription. We also found that promoter methylation increases in CD133- progeny of CD133+ cells, with CD133+ cells retaining a less methylated or unmethylated state. Taken together, our results show that CD133 expression in ovarian cancer is directly regulated by epigenetic modifications and support the idea that CD133 demarcates an ovarian cancer initiating cell population. The activity of these cells may be epigenetically detected and such cells might serve as pertinent chemotherapeutic targets for reducing disease recurrence. The objective of the study was to identify genes that are subject to DNA methylation through pharmacological inhibition of DNA methyltransferase activity in a panel of cancer cell lines. Cells were mock treated with culture media (mock treated) or treated with 5 µM decitabine for 72 hours. Resulting expression profiles were compared to identify genes with altered expression following decitabine treatment. These data represent two experiments: In the first, 43 established cell lines were mock treated or treated with decitabine to enable identification of genes differentially expressed as a result of inhibition of DNA methyltransferase activity. HEYA8-decitabine treated cells were run in replicate. In the second experiment, A2780 and PEO1 cells underwent flow activated cell sorting to separate CD133(+) from CD133(-) cells in each cell line; the sorted cell populations were cultured in the same manner as the first experiment and similarly mock treated or treated with decitabine. All specimens were arrayed in parallel and used for RMA normalization.
Project description:This SuperSeries is composed of the following subset Series: GSE25427: Gene expression profiles of primary cultured ovarian cells in the presence and absence of a DNA methyltransferase inhibitor GSE25428: Gene expression profiles of ovarian cancer cell lines in the presence and absence of a DNA methyltransferase inhibitor Refer to individual Series
Project description:Cisplatin and carboplatin are the primary first-line therapies for the treatment of ovarian cancer. However, resistance to these platinum-based drugs occurs in the large majority of initially responsive tumors, subsequently resulting in a poor long-term prognosis. To model the onset of drug resistance, and investigate the DNA methylation alterations associated with cisplatin resistance, we treated clonally derived, drug-sensitive A2780 epithelial ovarian cancer cells with increasing concentrations of cisplatin. After several cycles of drug selection, the isogenic drug-sensitive and -resistant pairs were subjected to global CGI methylation microarray analyses. We treated clonally derived, drug-sensitive A2780 epithelial ovarian cancer cells with increasing concentrations of cisplatin. After several cycles of drug selection, the isogenic drug-sensitive and -resistant pairs were subjected to global CGI methylation analyses by differential methylation hybridization (DMH) using a customed 44K promoter CGI microarray.
Project description:Acute myeloid leukemia (AML), and other myeloid malignancies, are frequently treated with hypomethylating agents like decitabine. Alterations in the epigenome, induced by decitabine, are likely to result in gene expression changes. The effects of decitabine have not been systemically studied using primary AML samples. We cultured 18 different primary AML samples for 7 days, the last 3 days of which included 100 nM decitabine (DAC) or 100 nm cytarabine (AraC). We hypothesized that decitabine treatment would result in detectable and consistent gene expression changes. For comparison, we also analyzed mRNA from cells treated with DMSO control (mock) and mRNA from uncultured cells taken at the time of diagnosis.
Project description:The taxanes are widely used in the treatment of breast and other cancers. While their cytotoxicity has been attributed to the induction of cell cycle arrest in mitosis through the stabilization of microtubules, we found that docetaxel promotes soluble tumor necrosis factor alpha (TNF-alpha production in MCF-7 breast tumor cells. TNF-alpha induces apoptotic cell death in a variety of cell types by binding to one of its receptors (TNFR1) which promotes death-inducing signaling complex (DISC) formation. Consistent with this view, we also report that selection of MCF-7 cells for survival in increasing concentrations of paclitaxel or docetaxel results in selection of drug-resistant variants that are resistant to TNF-alpha cytotoxicity. MCF-7 cells selected to 3-5 nM docetaxel produced >30-fold more TNF-alpha than control MCF-7CC cells but had strongly reduced levels of TNFR1. In contrast, expression of TNFR2 was unchanged, resulting in enhanced cell survival through the activation of the NF-kappaB p50 and p65 subunits. Gene expression profiling of docetaxel resistant MCF-7 cells compared to parental MCF-7 cells was performed for the changes of TNF related genes, and also confirmed in ovarian cell line A2780. Two docetaxel resistant cell lines of breast MCF-7 and ovarian A2780 were generated for gene expression profilling. Two colour microarray of Agilent whole human genome nucleotide arrays was conducted with two replicate of both forward and reverse labellings for MCF-7. Four arrays were used for this experiments. And it was four replicate of both forward and reverse labellings for A2780 cells. Eight arrays were used for this experiments
Project description:DNA methylation can be abnormally regulated in human disease and associated with effects on gene transcription that appear to be causally related to pathogenesis. The potential to use pharmacological agents that reverse this dysregulation is therefore an attractive possibility. To test how 5-aza-2’-deoxycytidine (5-aza-CdR) influences the genome therapeutically, we exposed non-malignant cells in culture to the agent and used genome-wide assays to assess the cellular response. We found that cells allowed to recover from 5-aza-CdR treatment only partially recover DNA methylation levels, retaining an epigenetic “imprint” of drug exposure. We show very limited transcriptional responses to demethylation of not only protein-coding genes but also loci encoding non-coding RNAs, with a limited proportion of the induced genes acquiring new promoter activation within gene bodies. The data revealed an uncoupling of DNA methylation effects at promoters, with demethylation mostly unaccompanied by transcriptional changes. The limited panel of genes induced by 5-aza-CdR resembles those activated in other human cell types exposed to the drug, and represents loci targeted for Polycomb-mediated silencing in stem cells, suggesting a model for the therapeutic effects of the drug. Our results do not support the hypothesis of DNA methylation having a predominant role to regulate transcriptional noise in the genome, and indicate that DNA methylation acts only as part of a larger complex system of transcriptional regulation. The targeting of 5-aza-CdR effects with its clastogenic consequences to euchromatin raises concerns that the use of 5-aza-CdR has innate tumorigenic consequences, requiring its cautious use in diseases involving epigenetic dysregulation. Examination of RNAPII Ser5(P) localization by ChIP-seq in HEK 293T cell after treatment with 5-aza-CdR.
Project description:A2780 ovarian cancer cells and a cisplatin resistant derivate of A2780 cells, obtained from ECACC, UK, No. 93112519 [A2780] and No. 93112517 [A2780 cis] were seeded out in T-75 flasks at a density of 2x106 for A2780sens and 3x106 for A2780cis cells in 15 ml of medium and preincubated overnight. Medium was removed and 15 ml fresh medium (37°C) with different concentrations of cisplatin, liposomal cisplatin or empty liposomes were added and incubated for 72 h at 37°C in a 5% CO2 incubator. In case of A2780sens cells, 1.72 µM cisplatin (IC50 concentration) and in case of A2780cis cells 8.94 µM cisplatin (IC50 concentration) were added. Liposomal formulations contained equal cisplatin concentrations. Empty liposomes were added in the same concentration as the liposomal cisplatin, to analyze the impact of liposomal lipids (A2780sens: 0.80µmol lipid, A2780cis: 4.15 µmol lipid). After incubation, medium was removed and cells were washed thrice with 10 ml PBS. 1 ml RLT-buffer was added and cells lysates were stored at -80°C until RNA extraction.
Project description:The human Werner and Bloom syndromes (WS and BS) are caused by deficiencies in the WRN and BLM RecQ helicases, respectively. WRN, BLM and their S. cerevisiae homologue Sgs1, are particularly active in vitro in unwinding G-quadruplex DNA (G4-DNA), a family of non-canonical nucleic acid structures formed by certain G-rich sequences. Recently, mRNA levels from loci containing potential G-quadruplex-forming sequences (PQS) were found to be preferentially altered in sgs1 mutants, suggesting that G4-DNA targeting by Sgs1 directly affects gene expression. Here, we extend these findings to human cells. Using microarrays to measure mRNAs obtained from human fibroblasts deficient for various RecQ family helicases, we observe significant associations between loci that are upregulated in WS or BS cells and loci that have PQS. No such PQS associations were observed for control expression datasets, however. Furthermore, upregulated genes in WS and BS showed no or dramatically reduced associations with sequences similar to PQS but that have considerably reduced potential to form intramolecular G4-DNA. These findings indicate that, like Sgs1, WRN and BLM can regulate transcription globally by targeting G4-DNA. Cell culture conditions and media Human fibroblast cell strains (WS: AG05229, AG12795, AG12797; BS: GM02932, GM03402, GM16891; RTS: AG18371, AG18375, AG05013; Normal/Wild-type: AG04054, AG06310, AG09975) were obtained from the Coriell Repository (Camden, NJ), from donors matched for gender and of similar ages, and were at similar passage levels. Cells were cultured in MEM supplemented with Earle’s salts, 20% fetal bovine serum, 1x penicillin/streptomycin, and 1x fungizone in 3% O2 at 37oC and harvested for RNA extraction during active growth and at ~ 80% confluence. GeneChip microarray expression Total RNA from the 12 fibroblast cell strains was isolated by extraction with TRIzol (Invitrogen) and purified using the RNeasy system (Qiagen). Total RNA was amplified by in vitro transcription using the Ovation RNA Amplification System V2 (NuGen). The resultant cDNA was fragmented and labeled using the FL-Ovation cDNA Biotin Module V2 (NuGen), and then purified using QIAquick columns (Qiagen), as specified by the Ovation System manual. Labeled probe was hybridized to Affymetrix U133A 2.0 GeneChips, and ultimately scanned using an Axon GenePix array scanner. Statistical analysis of microarray expression experiment The output files were normalized by Robust Multiarray Average (RMA), using the R package GCRMA and gene expression levels were log2-transformed.