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Epigenetics in hepatocellular carcinoma development and therapy: The tip of the iceberg. JHEP Rep 2020; 2:100167. [PMID: 33134907 PMCID: PMC7585149 DOI: 10.1016/j.jhepr.2020.100167] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/22/2020] [Accepted: 07/24/2020] [Indexed: 02/08/2023] Open
Abstract
Hepatocellular carcinoma (HCC) is a deadly tumour whose causative agents are generally well known, but whose pathogenesis remains poorly understood. Nevertheless, key genetic alterations are emerging from a heterogeneous molecular landscape, providing information on the tumorigenic process from initiation to progression. Among these molecular alterations, those that affect epigenetic processes are increasingly recognised as contributing to carcinogenesis from preneoplastic stages. The epigenetic machinery regulates gene expression through intertwined and partially characterised circuits involving chromatin remodelers, covalent DNA and histone modifications, and dedicated proteins reading these modifications. In this review, we summarise recent findings on HCC epigenetics, focusing mainly on changes in DNA and histone modifications and their carcinogenic implications. We also discuss the potential drugs that target epigenetic mechanisms for HCC treatment, either alone or in combination with current therapies, including immunotherapies.
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Key Words
- 5acC, 5-acetylcytosine
- 5fC, 5-formylcytosine
- 5hmC, 5-hydoxymethyl cytosine
- 5mC, 5-methylcytosine
- Acetyl-CoA, acetyl coenzyme A
- BER, base excision repair
- BRD, bromodomain
- CDA, cytidine deaminase
- CGI, CpG island
- CIMP, CGI methylator phenotype
- CTLA-4, cytotoxic T-lymphocyte-associated protein 4
- DNMT, DNA methyltransferase
- DNMTi, DNMT inhibitor
- Epigenetics
- FAD, flavin adenine dinucleotide
- HAT, histone acetyltransferases
- HCC, hepatocellular carcinoma
- HDAC, histone deacetylase
- HDACi, HDAC inhibitor
- HDM, histone demethylase
- HMT, histone methyltransferase
- Hepatocellular carcinoma
- KMT, lysine methyltransferase
- LSD/KDM, lysine specific demethylases
- NAFLD, non-alcoholic fatty liver disease
- NK, natural killer
- NPC, nasopharyngeal carcinoma
- PD-L1, programmed cell death ligand-1
- PD1, programmed cell death protein 1
- PHD, plant homeodomain
- PTM, post-translational modification
- SAM, S-adenosyl-L-methionine
- TDG, thymidine-DNA-glycosylase
- TERT, telomerase reverse transcriptase
- TET, ten-eleven translocation
- TME, tumour microenvironment
- TSG, tumour suppressor gene
- Therapy
- UHRF1, ubiquitin like with PHD and ring finger domains 1
- VEGF, vascular endothelial growth factor
- ncRNAs, non-coding RNAs
- α-KG, α-ketoglutarate
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Effects of particulate matter exposure on blood 5-hydroxymethylation: results from the Beijing truck driver air pollution study. Epigenetics 2016; 10:633-42. [PMID: 25970091 PMCID: PMC4623004 DOI: 10.1080/15592294.2015.1050174] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Previous studies have reported epigenetic changes induced by environmental exposures. However, previous investigations did not distinguish 5-methylcytosine (5mC) from a similar oxidative form with opposite functions, 5-hydroxymethylcytosine (5hmC). Here, we measured blood DNA global 5mC and 5hmC by ELISA and used adjusted mixed-effects regression models to evaluate the effects of ambient PM10 and personal PM2.5 and its elemental components—black carbon (BC), aluminum (Al), calcium (Ca), potassium (K), iron (Fe), sulfur (S), silicon (Si), titanium (Ti), and zinc (Zn)—on blood global 5mC and 5hmC levels. The study was conducted in 60 truck drivers and 60 office workers in Beijing, China from The Beijing Truck Driver Air Pollution Study at 2 exams separated by one to 2 weeks. Blood 5hmC level (0.08%) was ∼83-fold lower than 5mC (6.61%). An inter-quartile range (IQR) increase in same-day PM10 was associated with increases in 5hmC of 26.1% in office workers (P = 0.004), 20.2% in truck drivers (P = 0.014), and 21.9% in all participants combined (P < 0.001). PM10 effects on 5hmC were increasingly stronger when averaged over 4, 7, and 14 d preceding assessment (up to 132.6% for the 14-d average in all participants, P < 0.001). PM10 effects were also significant after controlling for multiple testing (family-wise error rate; FWER < 0.05). 5hmC was not correlated with personal measures of PM2.5 and elemental components (FWER > 0.05). 5mC showed no correlations with PM10, PM2.5, and elemental components measures (FWER > 0.05). Our study suggests that exposure to ambient PM10 affects 5hmC over time, but not 5mC. This finding demonstrates the need to differentiate 5hmC and 5mC in environmental studies of DNA methylation.
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Key Words
- 10 μm
- 2.5 μm
- 5-hydroxymethylcytosine
- 5-methylcytosine
- 5hmC, 5-hydroxymethylcytosine
- 5mC, 5-methylcytosine
- Al, aluminum
- BC, black carbon
- BMI, body mass index
- CI, confidence interval
- Ca, calcium
- DNA methylation
- ELISA, enzyme-linked immunosorbent assay
- Epigenetics
- FWER, family-wise error rate
- Fe, iron
- HPLC, high-performance liquid chromatography
- K, potassium
- PM, particulate matter
- PM10, particulate matter ≤
- PM2.5, particulate matter ≤
- Particulate Matter
- S, sulfur
- Si: silicon
- TET, ten-eleven translocation enzymes
- Ti, titanium and Zn: zinc.
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The ubiquitous transcription factor CTCF promotes lineage-specific epigenomic remodeling and establishment of transcriptional networks driving cell differentiation. Nucleus 2015; 6:15-8. [PMID: 25565413 DOI: 10.1080/19491034.2015.1004258] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Cell differentiation relies on tissue-specific transcription factors (TFs) that cooperate to establish unique transcriptomes and phenotypes. However, the role of ubiquitous TFs in these processes remains poorly defined. Recently, we have shown that the CCCTC-binding factor (CTCF) is required for adipocyte differentiation through epigenomic remodelling of adipose tissue-specific enhancers and transcriptional activation of Peroxisome proliferator-activated receptor gamma (PPARG), the main driver of the adipogenic program (PPARG), and its target genes. Here, we discuss how these findings, together with the recent literature, illuminate a functional role for ubiquitous TFs in lineage-determining transcriptional networks.
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Key Words
- 5hmC, 5-hydroxymethylcytosine
- 5mC, 5-methylcytosine
- CCCTC-binding factor (CTCF)
- CEBP, CCAAT/enhancer binding protein
- CTCF, CCCTC-binding factor
- DNA hydroxymethylation
- H3K27ac, acetylation of histone H3 lysine 27
- H3K4me1, monomethylation of histone H3 lysine 4
- KLF, Krüppel-like factors
- PPARG, Peroxisome proliferator-activated receptor gamma
- TET methylcytosine dioxygenase
- TET, Ten-eleven translocation methylcytosine dioxygenase
- TF, Transcription factor
- cell differentiation
- cistrome
- enhancer
- epigenome
- transcriptome
- ubiquitous transcription factor
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Hydroxylation of methylated DNA by TET1 in chondrocyte differentiation of C3H10T1/2 cells. Biochem Biophys Rep 2015; 5:134-140. [PMID: 28955815 PMCID: PMC5600463 DOI: 10.1016/j.bbrep.2015.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 11/05/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023] Open
Abstract
DNA methylation is closely involved in the regulation of cellular differentiation, including chondrogenic differentiation of mesenchymal stem cells. Recent studies showed that Ten-eleven translocation (TET) family proteins converted 5-methylcytosine (5mC) to 5-hydroxymethylcytosine, 5-formylcytosine and 5carboxylcytosine by oxidation. These reactions constitute potential mechanisms for active demethylation of methylated DNA. However, the relationship between the DNA methylation patterns and the effects of TET family proteins in chondrocyte differentiation is still unclear. In this study, we showed that DNA hydroxylation of 5mC was increased during chondrocytic differentiation of C3H10T1/2 cells and that the expression of Tet1 was particularly enhanced. Moreover, knockdown experiments revealed that the downregulation of Tet1 expression caused decreases in chondrogenesis markers such as type 2 and type 10 collagens. Furthermore, we found that TET proteins had a site preference for hydroxylation of 5mC on the Insulin-like growth factor 1 (Igf1) promoter in chondrocytes. Taken together, we showed that the expression of Tet1 was specifically facilitated in chondrocyte differentiation and Tet1 can regulate chondrocyte marker gene expression presumably through its hydroxylation activity for DNA.
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Abstract
The development and progression of melanoma have been attributed to independent or combined genetic and epigenetic events. There has been remarkable progress in understanding melanoma pathogenesis in terms of genetic alterations. However, recent studies have revealed a complex involvement of epigenetic mechanisms in the regulation of gene expression, including methylation, chromatin modification and remodeling, and the diverse activities of non-coding RNAs. The roles of gene methylation and miRNAs have been relatively well studied in melanoma, but other studies have shown that changes in chromatin status and in the differential expression of long non-coding RNAs can lead to altered regulation of key genes. Taken together, they affect the functioning of signaling pathways that influence each other, intersect, and form networks in which local perturbations disturb the activity of the whole system. Here, we focus on how epigenetic events intertwine with these pathways and contribute to the molecular pathogenesis of melanoma.
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Key Words
- 5hmC, 5-hydroxymethylcytosine
- 5mC, 5-methylcytosine
- ACE, angiotensin converting enzyme
- ANCR, anti-differentiation non-coding RNA
- ANRIL, antisense noncoding RNA in INK4 locus
- ASK1, apoptosis signal-regulating kinase 1
- ATRA, all-trans retinoic acid
- BANCR, BRAF-activated non-coding RNA
- BCL-2, B-cell lymphoma 2
- BRAF, B-Raf proto-oncogene, serine/threonine kinase
- BRG1, ATP-dependent helicase SMARCA4
- CAF-1, chromatin assembly factor-1
- CBX7, chromobox homolog 7
- CCND1, cyclin D1
- CD28, cluster of differentiation 28
- CDK, cyclin-dependent kinase
- CDKN2A/B, cyclin-dependent kinase inhibitor 2A/B
- CHD8, chromodomain-helicase DNA-binding protein 8
- CREB, cAMP response element-binding protein
- CUDR, cancer upregulated drug resistant
- Cdc6, cell division cycle 6
- DNA methylation/demethylation
- DNMT, DNA methyltransferase
- EMT, epithelial-mesenchymal transition
- ERK, extracellular signal-regulated kinase
- EZH2, enhancer of zeste homolog 2
- GPCRs, G-protein coupled receptors
- GSK3a, glycogen synthase kinase 3 α
- GWAS, genome-wide association study
- HDAC, histone deacetylase
- HOTAIR, HOX antisense intergenic RNA
- IAP, inhibitor of apoptosis
- IDH2, isocitrate dehydrogenase
- IFN, interferon, interleukin 23
- JNK, Jun N-terminal kinase
- Jak/STAT, Janus kinase/signal transducer and activator of transcription
- MAFG, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog G
- MALAT1, metastasis-associated lung adenocarcinoma transcript 1
- MAPK, mitogen-activated protein kinase
- MC1R, melanocortin-1 receptor
- MGMT, O6-methylguanine-DNA methyltransferase
- MIF, macrophage migration inhibitory factor
- MITF, microphthalmia-associated transcription factor
- MRE, miRNA recognition element
- MeCP2, methyl CpG binding protein 2
- NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells
- NOD, nucleotide-binding and oligomerization domain
- PBX, pre-B-cell leukemia homeobox
- PEDF, pigment epithelium derived factor
- PI3K, phosphatidylinositol-4, 5-bisphosphate 3-kinase
- PIB5PA, phosphatidylinositol-4, 5-biphosphate 5-phosphatase A
- PKA, protein kinase A
- PRC, polycomb repressor complex
- PSF, PTB associated splicing factor
- PTB, polypyrimidine tract-binding
- PTEN, phosphatase and tensin homolog
- RARB, retinoic acid receptor-β2
- RASSF1A, Ras association domain family 1A
- SETDB1, SET Domain, bifurcated 1
- SPRY4, Sprouty 4
- STAU1, Staufen1
- SWI/SNF, SWItch/Sucrose Non-Fermentable
- TCR, T-cell receptor
- TET, ten eleven translocase
- TGF β, transforming growth factor β
- TINCR, tissue differentiation-inducing non-protein coding RNA
- TOR, target of rapamycin
- TP53, tumor protein 53
- TRAF6, TNF receptor-associated factor 6
- UCA1, urothelial carcinoma-associated 1
- ceRNA, competitive endogenous RNAs
- chromatin modification
- chromatin remodeling
- epigenetics
- gene regulation
- lncRNA, long ncRNA
- melanoma
- miRNA, micro RNA
- ncRNA, non-coding RNA
- ncRNAs
- p14ARF, p14 alternative reading frame
- p16INK4a, p16 inhibitor of CDK4
- pRB, retinoblastoma protein
- snoRNA, small nucleolar RNA
- α-MSHm, α-melanocyte stimulating hormone
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Abstract
DNA methylation is a chemical modification of DNA involved in the regulation of gene expression by controlling the access to the DNA sequence. It is the most stable epigenetic mark and is widely studied for its role in major biological processes. Aberrant DNA methylation is observed in various pathologies, such as cancer. Therefore, there is a great interest in analyzing subtle changes in DNA methylation induced by biological processes or upon drug treatments. Here, we developed an improved methodology based on flow cytometry to measure variations of DNA methylation level in melanoma and leukemia cells. The accuracy of DNA methylation quantification was validated with LC-ESI mass spectrometry analysis. The new protocol was used to detect small variations of cytosine methylation occurring in individual cells during their cell cycle and those induced by the demethylating agent 5-aza-2'-deoxycytidine (5AzadC). Kinetic experiments confirmed that inheritance of DNA methylation occurs efficiently in S phase and revealed a short delay between DNA replication and completion of cytosine methylation. In addition, this study suggests that the uncoupling of 5AzadC effects on DNA demethylation and cell proliferation might be related to the duration of the DNA replication phase.
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Local chromatin microenvironment determines DNMT activity: from DNA methyltransferase to DNA demethylase or DNA dehydroxymethylase. Epigenetics 2015; 10:671-6. [PMID: 26098813 PMCID: PMC4622917 DOI: 10.1080/15592294.2015.1062204] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 06/03/2015] [Accepted: 06/09/2015] [Indexed: 12/22/2022] Open
Abstract
Insights on active DNA demethylation disproved the original assumption that DNA methylation is a stable epigenetic modification. Interestingly, mammalian DNA methyltransferases 3A and 3B (DNMT-3A and -3B) have also been reported to induce active DNA demethylation, in addition to their well-known function in catalyzing methylation. In situations of extremely low levels of S-adenosyl methionine (SAM), DNMT-3A and -3B might demethylate C-5 methyl cytosine (5mC) via deamination to thymine, which is subsequently replaced by an unmodified cytosine through the base excision repair (BER) pathway. Alternatively, 5mC when converted to 5- hydroxymethylcytosine (5hmC) by TET enzymes, might be further modified to an unmodified cytosine by DNMT-3A and -3B under oxidized redox conditions, although exact pathways are yet to be elucidated. Interestingly, even direct conversion of 5mC to cytosine might be catalyzed by DNMTs. Here, we summarize the evidence on the DNA dehydroxymethylase and demethylase activity of DNMT-3A and -3B. Although physiological relevance needs to be demonstrated, the current indications on the 5mC- and 5hmC-modifying activities of de novo DNA C-5 methyltransferases shed a new light on these enzymes. Despite the extreme circumstances required for such unexpected reactions to occur, we here put forward that the chromatin microenvironment can be locally exposed to extreme conditions, and hypothesize that such waves of extremes allow enzymes to act in differential ways.
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Key Words
- 5caC, 5-carboxylcytosine
- 5fC, 5-formylcytosine
- 5hmC, 5 hydroxymethylcytosine
- 5mC, 5-methylcytosine
- AID, activation-induced cytidine deaminase
- APOBEC, apolipoprotein B mRNA editing enzyme catalytic polypeptide-like
- BER, base excision and repair
- C, cytosine
- CGI, CpG islands
- DNA dehydroxymethylation
- DNA demethylation
- DNMT, DNA methyltransferase
- DNMTs
- GADD45, growth arrest and DNA-damage-inducible protein 45
- RARE, retinoic acid response element
- S-adenosyl methionine (SAM)
- SAM, S-adenosyl methionine
- TDG, thymine DNA glycosylase
- TET, ten-eleven translocation.
- chromatin microenvironment
- oxidizing redox state
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