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Epigenome reprogramming through H3K27 and H3K4 trimethylation as a resistance mechanism to DNA methylation inhibition in BRAFV600E-mutated CRC. [RNA-Seq]

ABSTRACT: BRAFV600E-mutated colorectal cancer (CRC) exhibits a strong correlation with DNA hypermethylation suggesting this subgroup of tumors is uniquely presenting epigenomic phenotypes. Nonetheless, the traditional epigenomic therapeutic agent, 5-azacitidine, which inhibits DNA methyltransferase activity, did not yield sufficient improvements in the efficacies of BRAFV600E CRC in vivo. We utilized a patient-derived xenograft model and confirmed an effective reduction of DNA methylation levels upon 5-azacitidine treatment yet failed to restore gene expression patterns. This study unbiasedly explored the adaptive engagement of other epigenomic modifications upon the profound decrease in DNA methylation by azacitidine treatment. A loss of histone acetylation and a gain of histone methylations, including H3K27 and H3K4 trimethylation, were observed around hypomethylated regions. Our findings suggested a compensatory increase in repressive histone mark, H3K27 trimethylation, around treatment-induced hypomethylated regions, which suggests the involvement of polycomb repressive complex (PRC) activity around the genome with lost DNA methylation, therefore maintaining the suppression of key genes. Combined inhibition of PRC activity through EZH2 inhibitor with azacitidine treatment additively improved efficacies in BRAFV600E CRC cells. In conclusion, DNA hypermethylation exhibits a close association with H3K27me3 and PRC activity in BRAFV600E CRC, and simultaneous blockade of DNMT and EZH2 holds promise as a potential therapeutic strategy for patients with BRAFV600E-mutated CRC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE254279 | GEO | 2024/09/01

REPOSITORIES: GEO

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Epigenome reprogramming through H3K27 and H3K4 trimethylation as a resistance mechanism to DNA methylation inhibition in BRAFV600E-mutated CRC [ATAC-seq]

Project description:BRAFV600E-mutated colorectal cancer (CRC) exhibits a strong correlation with DNA hypermethylation suggesting this subgroup of tumors is uniquely presenting epigenomic phenotypes. Nonetheless, the traditional epigenomic therapeutic agent, 5-azacitidine, which inhibits DNA methyltransferase activity, did not yield sufficient improvements in the efficacies of BRAFV600E CRC in vivo. We utilized a patient-derived xenograft model and confirmed an effective reduction of DNA methylation levels upon 5-azacitidine treatment yet failed to restore gene expression patterns. This study unbiasedly explored the adaptive engagement of other epigenomic modifications upon the profound decrease in DNA methylation by azacitidine treatment. A loss of histone acetylation and a gain of histone methylations, including H3K27 and H3K4 trimethylation, were observed around hypomethylated regions. Our findings suggested a compensatory increase in repressive histone mark, H3K27 trimethylation, around treatment-induced hypomethylated regions, which suggests the involvement of polycomb repressive complex (PRC) activity around the genome with lost DNA methylation, therefore maintaining the suppression of key genes. Combined inhibition of PRC activity through EZH2 inhibitor with azacitidine treatment additively improved efficacies in BRAFV600E CRC cells. In conclusion, DNA hypermethylation exhibits a close association with H3K27me3 and PRC activity in BRAFV600E CRC, and simultaneous blockade of DNMT and EZH2 holds promise as a potential therapeutic strategy for patients with BRAFV600E-mutated CRC.

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Epigenome reprogramming through H3K27 and H3K4 trimethylation as a resistance mechanism to DNA methylation inhibition in BRAFV600E-mutated CRC. [ChIP-Seq]

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Tretinoin synergistically enhances the antitumor effect of combined BRAF, MEK, and EGFR inhibition in BRAFV600E colorectal cancer [HT29 samples]

Project description:Patients with BRAF-mutated colorectal cancer (BRAFV600E CRC) are currently treated by a combination of BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor. A fundamental problem in treating patients with BRAFV600E CRC is intrinsic and/or acquired resistance to this combination therapy. By screening 78 compounds, we identified tretinoin, a retinoid, as a compound that synergistically enhances the antiproliferative effect of a combination of BRAF inhibition and MEK inhibition with or without EGFR inhibition on BRAFV600E CRC cells. This synergistic effect was also exerted by other retinoids. Tretinoin, added to BRAF inhibitor and MEK inhibitor, upregulated PARP, BAK, and p-H2AX. When either RARα or RXRα was silenced, the increase in cleaved PARP expression by the addition of TRE to ENC/BIN or ENC/BIN/CET was canceled. Our results suggest that the mechanism of the synergistic antiproliferative effect involves modulation of the Bcl-2 family and the DNA damage response that affects apoptotic pathways, and this synergistic effect is induced by RARα- or RXRα-mediated apoptosis. Tretinoin also enhanced the antitumor effect of a combination of BRAF inhibitor and anti-EGFR antibody with or without MEK inhibitor in a BRAFV600E CRC xenograft mouse model. Our data provide a rationale for developing retinoids as a new combination agent to overcome resistance to the combination therapy for patients with BRAFV600E CRC.

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Tretinoin synergistically enhances the antitumor effect of combined BRAF, MEK, and EGFR inhibition in BRAFV600E colorectal cancer [RKO samples]

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DNA methylation analysisof KRAS mutated colorectal tumors and adjacent tissues from cancer patinets and KRAS mutated Aberrant Crypt Foci and matching normal crypts from healthy individuals by using RRBS

Project description:Colorectal cancer (CRC) is characterized by genome-wide alterations to DNA methylation that influence gene expression and genomic stability. Less is known about the extent to which methylation is disrupted in the earliest stages of CRC development. In this study we have combined laser-capture microdissection (LCM) with reduced representation bisulfite sequencing (RRBS) to identify cancer associated DNA methylation changes in human aberrant crypt foci (ACF), the earliest putative precursor to CRC. Using this approach, methylation profiles have been generated for 10 KRAS-mutant ACF and 10 CRCs harboring a KRAS mutation, as well as matched samples of normal mucosa. Of 811 differentially methylated regions (DMRs) identified in ACF, 537 (66%) were hypermethylated and 274 (34%) were hypomethylated. DMRs located within intergenic regions were heavily enriched for AP-1 transcription factor binding sites and were frequently hypomethylated. Furthermore, gene ontology (GO) analysis demonstrated that DMRs associated with promoters were enriched for genes involved in intestinal development, including homeobox genes and targets of the Polycomb repressive complex 2 (PRC2).Consistent with their role in the earliest stages of colonic neoplasia, 75% of the methylation changes identified in ACF were also present in the CRC samples. Together, these data demonstrate that DNA methylation changes, including significant hypomethylation, occur more frequently in early colonic neoplasia than previously believed, and identify epigenomic features of ACF that may provide new targets for cancer chemoprevention or lead to the development of new biomarkers for CRC risk.

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Coding and noncoding transcriptome sequencing of KRAS mutated colorectal tumors and adjacent tissues from cancer patients and KRAS mutated Aberrant Crypt Foci and matching normal crypts from healthy individuals [RNA-Seq]

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Frequent switching of Polycomb repressive marks and DNA hypermethylation in the PC3 prostate cancer cell line

Project description:Epigenetic reprogramming is commonly observed in cancer, and is hypothesized to involve multiple mechanisms, including DNA methylation and Polycomb repressive complexes (PRCs). Here we devise a new experimental and analytical strategy using customized high density tiling arrays to investigate coordinated patterns of gene expression, DNA methylation and Polycomb marks which differentiate prostate cancer cells from their normal counterparts. Three major changes in the epigenomic landscape distinguish the two cell types. Developmentally significant genes containing CpG islands which are silenced by PRCs in the normal cells acquire DNA methylation silencing and lose their PRC marks (epigenetic switching). Since these genes are normally silent this switch does not cause de novo repression but might significantly reduce epigenetic plasticity. Two other groups of genes are silenced by either de novo DNA methylation without PRC occupancy (5mC reprogramming) or by de novo PRC occupancy without DNA methylation (PRC reprogramming). Our data suggest that the two silencing mechanisms act in parallel to reprogram the cancer epigenome, and that DNA hypermethylation may replace Polycomb based repression near key regulatory genes, possibly reducing their regulatory plasticity. Profiling 5mC and H3K27m3/Suz12 occupancy in the PC3 cancer line and the PrEC system. Hybridization over a custom array including a representative set of promoters (-2.5 to +1 kb) with variable CpG content levels and variable expression levels in the two cell systems.

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Enhanced epigenetic profiling of classical human monocytes reveals a specific signature of healthy aging in the DNA methylome

Project description:The impact of healthy aging on molecular programming of immune cells is poorly understood. Here, we report comprehensive characterization of healthy aging in human classical monocytes, with a focus on epigenomic, transcriptomic, and proteomic alterations, as well as the corresponding proteomic and metabolomic data for plasma, using healthy cohorts of 20 young and 20 older males (~27 and ~64 years old on average). For each individual, we performed eRRBS-based DNA methylation profiling, which allowed us to identify a set of age-associated differentially methylated regions (DMRs) – a novel, cell-type specific signature of aging in DNA methylome. Hypermethylation events were associated with H3K27me3 in the CpG islands near promoters of lowly-expressed genes, while hypomethylated DMRs were enriched in H3K4me1 marked regions and associated with age-related increase of expression of the corresponding genes, providing a link between DNA methylation and age-associated transcriptional changes in primary human cells.

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Frequent switching of Polycomb repressive marks and DNA hypermethylation in the PC3 prostate cancer cell line

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Oncogenic BRAFV600E remodels the melanocyte transcriptome and induces BANCR to regulate melanoma cell migration [HT-seq]

Project description:Most cancer genomics papers to date have focused on aberrations in genomic DNA and protein-coding transcripts. However, around 50% of transcripts have no coding potential and may exist as non-coding RNA. We performed RNA-seq in BRAFv600e melanoma skin cancer and on melanocytes over-expressing oncogenic BRAF to catalog transcriptome remodeling. We discovered that BRAF regulates expression of 1027 protein coding transcripts, 39 annotated lncRNAs and 70 novel transcripts. Many of the novel transcripts are lncRNAs. We used an indepenedent dataset to interrogate our novel transcripts and found that the novel lncRNA BANCR is a BRAF-regulated lncRNA recurrently upregulated in melanoma. Knockdown of BANCR impairs melanoma cell migration. Whole transcriptome RNA-seq followed assembly to Refseq/Gencode and de novo transcript assembly. RNA-seq performed on: 2 BRAFv600e melanomas, melanocytes+RFP control and melanocytes + BRAFv600e. We discovered protein-coding transcripts, annotated ncRNAs and novel transcripts (including lncRNAs) regulated by BRAFv600e also coordinately expressed in melanoma.

2012-04-28 | E-GEOD-33092 | biostudies-arrayexpress

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