TET2 Expression Research Articles

Abstract B013: Suppression of TET1 expression down-regulates p16 and contributes to the resistance of SWI/SNF LOF tumors to PRC2 inhibition

Abstract Polycomb repressive complex 2 (PRC2) drives the expansion of H3K27me3 epigenetic marker and suppress the expression of target genes including tumor suppressors. Activation mutations of EZH2, the catalytic subunit of the PRC2 complex, are thought to be the driver for certain malignancies such as diffused large B cell lymphoma (DLBCL). The SWI/SNF complex remodels nucleosomes to modulate transcription, they are generally considered as tumor suppressors and loss-of-function (LOF) mutations are frequently found across a wide variety of cancers. Many studies suggest that PRC2 is important for the proliferation of tumor cells with SWI/SNF LOF mutations, indeed, EZH2 inhibitor tazemetostat was approved by FDA for epithelioid sarcoma with SWI/SNF subunit SMARCB1 deletion. While not all SWI/SNF LOF tumors respond to PRC2 inhibition, we would like to know what subset of these tumors are sensitive to PRC2 inhibition. In this study, we have developed a potent and selective PRC2 inhibitor BR1763 which blocks the interaction of EED with tri-methylated histone H3 at Lys 27 (H3K27me3) and inhibits cellular H3K27me3 levels. By analyzing the gene expression patterns of BR1763 treated cells, we found that up-regulation of CDKN2A/p16 and down-regulation of E2F downstream gene are essential for cellular response to PRC2 inhibition. Further studies also confirmed that PRC2 inhibition caused P16 up-regulation and induced cell senescence for the sensitive cells. Importantly, suppression of TET1 expression contributes to the resistance to PRC2 inhibition in SWI/SNF LOF tumors, which may be caused by PcG hypermethylation on p16 promoters. TET1 expression, together with SWI/SNF LOF mutation status, can largely predict the sensitivity of tumor cells to PRC2 inhibition. Citation Format: Hailong Zhang. Suppression of TET1 expression down-regulates p16 and contributes to the resistance of SWI/SNF LOF tumors to PRC2 inhibition. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr B013.

Oxidative low-density lipoprotein oxLDL induces pyroptosis in trophoblast cells HTR-8/Svneo by downregulating TET2

ObjectiveTo investigate pyroptosis in the trophoblast cells HTR-8/Svneo induced by TET2 in oxidized low-density lipoprotein (oxLDL). MethodsHTR-8/Svneo cells were treated with vehicle (0 mg/L) and 50 mg/L oxLDL for 24 h. The effects of oxLDL on TET2 expression in HTR-8/Svneo cells were detected by Western blot. Knockdown of TET2 was performed in HTR-8/Svneo cells using si-TET2. CCK8, Transwell, and wound healing assays were used to detect the effect of TET2 knockdown on the proliferation, cell cycle, migration, and invasion of HTR-8/Svneo cells, respectively. Western blot was used to quantify the expression levels of the pyroptosis proteins GSDMD and caspase-1 in si-TET2 treated cells. ResultsoxLDL downregulates TET2 expression in a concentration-dependent manner. TET2 knockdown inhibits HTR-8/Svneo invasion and migration but promotes cell proliferation. Western blot results showed that TET2 knockdown upgregulated the expression of GSDMD and caspase-1. ConclusionoxLDL induces pyroptosis of HTR-8/Svneo by downregulating TET2 expression, resulting in decreased trophoblast invasion and migration. These data suggest that TET2-induced pyroptosis play a critical role in gestational pathologies, such as preeclampsia. Further studies can clarify the mechanisms of this process and elucidate potential preventive and therapeutic targets.

Integrated analysis revealing the role of TET3-mediated MUC13 promoter hypomethylation in hepatocellular carcinogenesis.

Aim: To explore the function and underlying mechanism of MUC13 in hepatocellular carcinoma (HCC) oncogenesis. Materials & Methods: Online databases and software were used to perform analyses of expression, methylation and enrichment pathway. Experiments were performed to confirm theresults using HCC cells in vitro. Results: MUC13 was upregulated in HCC and liver cancer stem cells (CSCs) and had a positive influence on CSCgeneration. Further analyses revealed that MUC13 with promoter hypomethylatedwas regulated by DNA demethylase TET3, which was overexpressed in HCC and liver CSCs. Conclusion: These results strongly suggested that high TET3 expression in liver CSCsmay mediate MUC13 upregulation via promoter hypomethylationand thereby contribute to hepatocellular carcinogenesis.

Demonstration That Loss of TET2 Impairs DNA Mismatch Repair Resulting in Clonally Restricted Genomic Instability

Epigenetic dysregulation is a common feature of myeloid neoplasia (MN). TET2, along with TET1 and TET3 are the only known enzymes, which progressively oxidize 5-methyl cytosine and thus facilitate active demethylation of CpG islands, a process critical for efficient gene expression and maintenance of genomic integrity. Loss of function TET2 mutations (TET2MT) are one of the most common somatic lesions in MN. To date, the precise mechanisms of TET2MT in leukemogenesis remain unclear. However, two potential mechanisms have been postulated; i) TET2MT may lead to expansion of stem cells by differentiation block and/or increased self-renewal ii) clonally restricted hyper mutations resulting in acquisition of secondary driver mutations. This functional duality may explain proleukemogenic consequences of TET2MT. Both mechanisms are compatible with their relatively moderate driver phenotype. Increased CàT transitions via deamination of 5mC in TET2MT has been postulated; however this report focuses on a novel mechanism of TET2MT- mediated impairment of mismatch repair (MMR). WES was used for analysis of the mutational status of 435 MN cases to test whether TET2MT (n= 82/435; 19%) predispose to acquisition of additional mutations. Following exclusion of dysfunction in known DNA repair genes, we compared the median SNVs in TET2MT vs. TET2WT. TET2MT cases had nearly a 2-fold increased median SNVs (p<0.0001) vs. TET2WT including a 2.1-fold increase in truncations (p=0.03) with a linear correlation (r=0.7) of SNVs vs. clonality, consistent with a gene-dose effect. ShRNA knockdown of TET2 in HeLa and CRISPR knockout in HEK293 cells resulted in a 24- and 30-fold increase in spontaneous mutations in the HPRT assay. The heightened spontaneous mutability in TET2KO/KD cells were reversed by ectopic expression of TET2. In Tet2-/- mice, ~1.5-fold increased mutagenicity at TET2-dependent active demethylation sites were detected suggesting its direct or indirect involvement in one or more DNA repair pathways. Consistent with our hypothesis, endogenous co-immunoprecipitation of TET2 followed by tandem-affinity purification and characterization of protein complexes with LCMS/MS in 4 different systems including human leukemic cell lines (K562 and CMK), murine embryonic stem cell and erythroid leukemia cells MEL identified all the major components of DNA MMR complex as a part of TET2 interactome. In every cell line, MSH6, a main component of MMR complex was an abundant TET2 interacting protein. This result was further confirmed by reverse co-immunoprecipitation using anti-MSH6 antibodies in different cell lines. Using truncating deletion constructs of TET2, MSH6 binding site was mapped on TET2 N-terminal amino acid segment 460-942. Functional MMR fluorescence reporter assay, wherein a point mutant of GFP, if repaired, is converted to BFP, demonstrated that loss of TET2 indeed compromised the rate of MMR in CRISPR generated deletion of TET2 in K562 and HEK293 cells. Ectopic expression of N-terminal (aa 460-942) MSH6 binding domain rescued this defect. The genomic instability due to MMR dysfunction in TET2MT cells may allow therapeutic targeting of DNA repair proteins in a subset of TET2MT MN. Therefore, we tested the therapeutic vulnerability of TET2MT cells against small molecule DNA repair inhibitors (e.g., clinically approved PARP antagonists) in engineered isogenic and natural TET2MT cell lines. The TET2KO/KD cells were 2-10X more sensitive to olaparib and rukaparib compared to parental TET2 proficient cells, both under steady state and under conditions of oxidative stress as observed in gH2AX assays and various apoptotic readouts. In summary, for the first time here we report that TET2 directly binds to MSH6 and recruits MMR complex to the site of mismatch around CpG islands and facilitate the repair. Loss of TET2impairs this process, explaining the accumulation of secondary hits in mutant clones, which by this virtue, progressively increases their leukemogenic fitness. Given that MSH6 is known to interact 5hmC, TET2 may guide MMR to TET2-dependent DNA loci directly linking TET2MTto genomic instability a biologic feature that can be therapeutically exploited. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The NLRC4 Inflammasome Drives Myelodysplastic Syndrome By Linking Epigenetic Reprogramming and Innate Immune Signaling

Introduction Myelodysplastic syndromes (MDS) are a heterogeneous group of hematopoietic stem cell (HSC) malignancies characterized by dysplastic and ineffective hematopoiesis. Despite emerging evidence that chronic inflammation contributes to the development of MDS, the mechanisms underlying the dysregulation of innate immune and inflammatory signaling pathways in hematopoietic stem and progenitor cells (HSPCs) remain poorly characterized. We have used multiple MDS mouse models to identify a tumor suppressive role for the EP300 epigenetic histone acetyltransferase enzyme in the progression of MDS to AML. Based on the gene expression changes we observed, we have used one specific mouse model, that lacks Tet2 expression, to define the role that chronic inflammation plays in promoting MDS development and the mechanisms involved. Methods We have conducted a series of in vitro, in vivo, and in silico experiments using Tet2-deficient mice, and chronic, low-dose LPS treatment to model chronic inflammation. Cytokine array immunoassays were performed to evaluate the inflammatory response of WT or Tet2-deficient mice to LPS treatment. Chimeric mice transplanted with bone marrow (BM) cells isolated from LPS or vehicle (PBS) treated WT or Tet2-deficient mice were monitored for the development of MDS and survival. Serial competitive bone marrow transplantation assays and flow cytometry profiling were used to determine the competitive advantage of LPS or PBS-treated BM cells, and their differentiation. Bioinformatic analyses of RNA sequencing (RNA-seq) results from our mouse model were performed to characterize the transcriptional profiling and identify novel innate immune pathways. Colony-forming unit (CFU) and qPCR assays were used to evaluate HSPC proliferative capacity, self-renewal, and gene expression changes. Results We find that mice lacking Tet2 develop a hyper-inflammatory status, marked by the expression of a number of pro-inflammatory cytokines, such as Il-1b and Il-6, which are further fueled by LPS-induced chronic inflammation. Chimeric mice transplanted with BM cells isolated from LPS-treated Tet2-deficient mice exhibit a significantly shorter life span and early onset of MDS phenotypes, including dysplastic hematopoiesis and thrombocytopenia, compared to age-matched chimeric mice transplanted with BM cells isolated from PBS-treated Tet2-deficient mice or LPS-treated WT mice. Chronic inflammation promotes the self-renewal and myeloid differentiation of Tet2-deficient HSPCs in the short term; however, it accelerates HSC exhaustion in the long run. Transcription profiling and subsequent bioinformatic analyses identify functional clusters in LPS-treated Tet2-deficient HSPCs, including genes involved in the regulation of epigenetics, immunity, metabolism, and cell cycle. Detailed inspection of the most highly differentially expressed genes reveals that many genes in the Nlrc4 inflammasome pathway are upregulated in LPS-treated Tet2-deficient HSPCs. We validate changes in the expression of these genes by qPCR, and then show that deleting Nlrc4 suppresses the colony formation of Tet2-deficient HSPCs in vitro. Ongoing work focuses on evaluating the effects of deleting Nlrc4 or blocking Nlrc4 function using a small molecule inhibitor on MDS development in vivo. Conclusions The combinatory role of intrinsic and extrinsic factors drives the development of MDS in this Tet2-deficient MDS mouse model. It is likely that different genetic mutations generate unique sensitivity to certain signaling pathways, and we demonstrate the epigenetic rewiring and activation of the Nlrc4 inflammasome pathway as a mechanistic basis for the inflammatory component of MDS [or clonal hematopoiesis of indeterminate potential (CHIP)] pathogenesis in Tet2-deficient cells. Our work has the potential to provide novel targeting opportunities in MDS management and confirm the importance of different components of inflammasome signaling in MDS.

The prognostic role of C-KIT, TET1 and TET2 gene expression in Acute Myeloid Leukemia

Aimwas to assess the role of C-KIT, TET1 and TET2 expression in the diagnosis and prognosis of acute myeloblastic leukemia (AML).MethodsThe expression levels of C-KIT, TET1 and TET2 were assessed in the bone marrow (BM) aspirate of 152 AML patients compared to 20 healthy control using quantitative real-time polymerase chain reaction (qRT-PCR). Data were correlated with the clinico-pathological features of the patients, response to treatment, disease-free survival (DFS), and overall survival (OS) rates.ResultsC-KIT, TET1 and TET2 were significantly upregulated in AML patients [0.25 (0–11.6), 0.0113 (0–3.301), and 0.07 (0–4); respectively], compared to the control group [0.013 (0.005–0.250), P < 0.001, 0.001 (0–0.006), P < 0.001, and 0.02 (0.008–0.055), P = 0.019; respectively]. The sensitivity, specificity, and area under curve of of C-KIT were (48.7%, 100%, 0.855; respectively, P = 0.001), and that of TET1 were (63.4%, 100%, 0.897; respectively, P = 0.001), while that of TET2 were (56.8%, 100%, 0.766; respectively, P = 0.019). When combining the three markers, the sensitivity was 77.5%, however it reached the highest sensitivity (78.6%) and specificity (100%) when combining both c-KIT + TET1 together for the diagnosis of AML. C-KIT overexpression associated with shorter DFS (P = 0.05) and increased incidence of relapse (P = 0.019). Lymph nodes involvement [HR = 2.200, P = 0.005] is an independent risk factor for shorter OS rate of AML patients. Increased BM blast % [HR = 7.768, P = 0.002], and FLT3-ITD mutation [HR = 2.989, P = 0.032] are independent risk factors for shorter DSF rate of the patients.ConclusionC-KIT, TET1, and TET2 could be used as possible useful biomarkers for the diagnosis of AML.

Interactive regulation of DNA demethylase gene TET1 and m6A methyltransferase gene METTL3 in myoblast differentiation

DNA methylation (5mC) and mRNA N6-methyladenosine (m6A) play an essential role in gene transcriptional regulation. DNA methylation has been well established to be involved in skeletal muscle development. Interacting regulatory mechanisms between DNA methylation and mRNA m6A modification have been identified in a variety of biological processes. However, the effect of m6A on skeletal muscle differentiation and the underlying mechanisms are still unclear. It is also unknown whether there is an interaction between DNA methylation and mRNA m6A modification in skeletal myogenesis. In the present study, we used m6A-IP-qPCR, LC–MS/MS and dot blot assays to determine that the DNA demethylase gene, TET1, exhibited increased m6A levels and decreased mRNA expression during bovine skeletal myoblast differentiation. Dual-luciferase reporter assays and RIP experiments demonstrated that METTL3 suppressed TET1 expression by regulating TET1 mRNA stability in a m6A-YTHDF2-dependent manner. Furthermore, TET1 mediated DNA demethylation of itself, MYOD1 and MYOG, thereby stimulating their expression to promote myogenic differentiation. Ectopic expression of TET1 rescued the effect of METTL3 knockdown on reduced myotubes. In contrast, TET1 knockdown impaired the myogenic differentiation promoted by METTL3 overexpression. Moreover, ChIP experiments found that TET1 could bind and demethylate METTL3 DNA, which enhanced METTL3 expression. In addition, TET1 knockdown decreased m6A levels. ChIP assays also showed that TET1 knockdown contributed to the binding of H3K4me3 and H3K27me3 to METTL3 DNA. Our results revealed a negative feedback regulatory loop between TET1 and METTL3 in myoblast differentiation, which unveiled the interplay among DNA methylation, RNA methylation and histone methylation in skeletal myogenesis.

AHR/TET2/NT5E axis downregulation is associated with the risk of systemic lupus erythematosus and its progression.

The prognosis of systemic lupus erythematosus (SLE) is unpredictable. This study aimed to examine the regulatory mechanism of the AHR/TET2/NT5E pathway during SLE progression. The AHR, TET2 and NT5E expression levels were examined in T regulatory cells (Tregs) of patients with SLE. The correlation of AHR, TET2 or NT5E expression levels with the immunosuppressive functions of Tregs was analysed. In patients with SLE, the number of CD4+ IL2RA- FOXP3+ T cell subset was positively correlated with the SLE disease activity index value and negatively correlated with the AHR and TET2 expression levels in CD4+ IL2RA+ FOXP3+ Tregs. Transcriptional profiles of 79 patients with SLE obtained from the Gene Expression Omnibus database (GSE61635 dataset) revealed a significant positive correlation between the mRNA expression levels of AHR and TET2. In silico analysis predicted that the TET2 promoter comprises an AHR-binding site. Kynurenine (KYN) promoted the binding of AHR to the TET2 promoter in Tregs of patients with SLE and Jurkat T cell lines. Furthermore, NT5E expression was significantly downregulated in Tregs of patients with SLE, which can be attributed to the dysregulation of NT5E promoter methylation status induced by downregulated TET2 activity. Furthermore, the Treg immunosuppressive activity, which is mediated through the TET2 and A2AR-adenosine pathways, in the KYN-treated group was approximately two-fold higher than that in the control group. The AHR/TET2/NT5E axis mediates the Treg immunosuppressive activity. These findings provide novel insights for the development of therapeutic approaches for SLE and related autoimmune diseases.

Knockdown of Tet2 Inhibits the Myogenic Differentiation of Chicken Myoblasts Induced by Ascorbic Acid.

Ascorbic acid (also called Vitamin C, VC) strengthens the function of Tets families and directly increases DNA demethylation level to affect myogenic differentiation. However, the precise regulatory mechanism of DNA methylation in chicken myogenesis remains unclear. Results of present study showed that the mRNA expression of MyoD significantly decreased and MyoG and MyHC increased in myoblasts treated with 5 μM 5-azacytidine (5-AZA) and 5 μM VC (p &lt; 0.05). Results also indicated the formation of myotubes was induced by 5-AZA or VC, but this effect was attenuated after knockdown of Tet2. In addition, the protein expression of TET2, DESMIN and MyHC was remarkable increased by the addition of 5-AZA or VC, and the upregulation was inhibited after knockdown of Tet2 (p &lt; 0.05). DNA dot blot and immunofluorescence staining results suggested that the level of 5hmC was significantly increased when treated with 5-AZA or VC, even by Tet2 knockdown (p &lt; 0.05). Moreover, 5-AZA and VC reduced the level of dimethylation of lysine 9 (H3K9me2) and trimethylation of lysine 27 of histone 3 (H3K27me3), and this inhibitory effect was eliminated after Tet2 knockdown (p &lt; 0.05). These data indicated that Tet2 knockdown antagonized the increased levels of 5hmC and H3K27me3 induced by 5-AZA and VC, and eventually reduced myotube formation by modulating the expression of genes involved in myogenic differentiation. This study provides insights that epigenetic regulators play essential roles in mediating the myogenic program of chicken myoblasts.

Enhanced BPGM/2,3-DPG pathway activity suppresses glycolysis in hypoxic astrocytes via FIH-1 and TET2

ObjectiveBisphosphoglycerate mutase (BPGM) is expressed in human erythrocytes and responsible for the production of 2,3-bisphosphoglycerate (2,3-DPG). However, the expression and role of BPGM in other cells have not been reported. In this work, we found that BPGM was significantly upregulated in astrocytes upon acute hypoxia, and the role of this phenomenon will be clarified in the following report. MethodsThe mRNA and protein expression levels of BPGM and the content of 2,3-DPG with hypoxia treatment were determined in vitro and in vivo. Furthermore, glycolysis was evaluated upon in hypoxic astrocytes with BPGM knockdown and in normoxic astrocytes with BPGM overexpression or 2,3-DPG treatment. To investigate the mechanism by which BPGM/2,3-DPG regulated glycolysis in hypoxic astrocytes, we detected the expression of HIF-1α, FIH-1 and TET2 with silencing or overexpression of BPGM and 2,3-DPG treatment. ResultsThe expression of glycolytic genes and the capacity of lactate markedly increased with 6 h, 12 h, 24 h, 36 h and 48 h 1 % O2 hypoxic treatment in astrocytes. The expression of BPGM was upregulated, and the production of 2,3-DPG was accelerated upon hypoxia. Moreover, when BPGM expression was knocked down, glycolysis was promoted in HEB cells. However, overexpression of BPGM and addition of 2,3-DPG to the cellular medium in normoxic cells could downregulate glycolytic genes. Furthermore, HIF-1α and TET2 exhibited higher expression levels and FIH-1 showed a lower expression level upon BPGM silencing, while these changes were reversed under BPGM overexpression and 2,3-DPG treatment. ConclusionsOur study revealed that the BPGM/2,3-DPG pathway presented a suppressive effect on glycolysis in hypoxic astrocytes by negatively regulating HIF-1α and TET2.

Decitabine-induced DNA methylation-mediated transcriptomic reprogramming in human breast cancer cell lines; the impact of DCK overexpression.

Decitabine (DAC), a DNA methyltransferase (DNMT) inhibitor, is tested in combination with conventional anticancer drugs as a treatment option for various solid tumors. Although epigenome modulation provides a promising avenue in treating resistant cancer types, more studies are required to evaluate its safety and ability to normalize the aberrant transcriptional profiles. As deoxycytidine kinase (DCK)-mediated phosphorylation is a rate-limiting step in DAC metabolic activation, we hypothesized that its intracellular overexpression could potentiate DAC’s effect on cell methylome and thus increase its therapeutic efficacy. Therefore, two breast cancer cell lines, JIMT-1 and T-47D, differing in their molecular characteristics, were transfected with a DCK expression vector and exposed to low-dose DAC (approximately IC20). Although transfection resulted in a significant DCK expression increase, further enhanced by DAC exposure, no transfection-induced changes were found at the global DNA methylation level or in cell viability. In parallel, an integrative approach was applied to decipher DAC-induced, methylation-mediated, transcriptomic reprogramming. Besides large-scale hypomethylation, accompanied by up-regulation of gene expression across the entire genome, DAC also induced hypermethylation and down-regulation of numerous genes in both cell lines. Interestingly, TET1 and TET2 expression halved in JIMT-1 cells after DAC exposure, while DNMTs’ changes were not significant. The protein digestion and absorption pathway, containing numerous collagen and solute carrier genes, ranking second among membrane transport proteins, was the top enriched pathway in both cell lines when hypomethylated and up-regulated genes were considered. Moreover, the calcium signaling pathway, playing a significant role in drug resistance, was among the top enriched in JIMT-1 cells. Although low-dose DAC demonstrated its ability to normalize the expression of tumor suppressors, several oncogenes were also up-regulated, a finding, that supports previously raised concerns regarding its broad reprogramming potential. Importantly, our research provides evidence about the involvement of active demethylation in DAC-mediated transcriptional reprogramming.

Aberrant methylation of Serpine1 mediates lung injury in neonatal mice prenatally exposed to intrauterine inflammation

BackgroundIntrauterine inflammation (IUI) alters epigenetic modifications in offspring, leading to lung injury. However, the epigenetic mechanism underlying IUI-induced lung injury remains uncertain. In the present study, we aim to investigate the effect of IUI on lung development, and to identify the key molecule involved in this process and its epigenetic regulatory mechanism.ResultsSerpine1 was upregulated in the lung tissue of neonatal mice with IUI. Intranasal delivery of Serpine1 siRNA markedly reversed IUI-induced lung injury. Serpine1 overexpression substantially promoted cell senescence of both human and murine lung epithelial cells, reflected by decreased cell proliferation and increased senescence-associated β-galactosidase activity, G0/G1 cell fraction, senescence marker, and oxidative and DNA damage marker expression. IUI decreased the methylation level of the Serpine1 promoter, and methylation of the promoter led to transcriptional repression of Serpine1. Furthermore, IUI promoted the expression of Tet1 potentially through TNF-α, while Tet1 facilitated the demethylation of Serpine1 promoter. DNA pull-down and ChIP assays revealed that the Serpine1 promoter was regulated by Rela and Hdac2. DNA demethylation increased the recruitment of Rela to the Serpine1 promoter and induced the release of Hdac2.ConclusionIncreased Serpine1 expression mediated by DNA demethylation causes lung injury in neonatal mice with IUI. Therefore, therapeutic interventions targeting Serpine1 may effectively prevent IUI-induced lung injury.

Quercetin Mediated TET1 Expression Through MicroRNA-17 Induced Cell Apoptosis in Melanoma Cells.

A previous report suggested that the expression of ten-eleven translocation (TET) proteins is abnormal in certain cancers. Quercetin has been demonstrated as anti-cancer role in cancer development. In order to explore the inhibitory effect and mechanism of quercetin on uveal melanoma cells, the expression of TET proteins was analyzed in the present study. Our results suggest that the expression of TET1 was increased following treatment with quercetin in OCM-1, SK-MEL-1, and B16 cells. In addition, quercetin treatment induced apoptosis and inhibited migration and invasion. To further investigate the association of the expression of TET1 with cell growth, apoptosis, migration, and invasion, cell lines in which TET1 was knocked-down or overexpressed were constructed. The results showed that the increased expression of TET1-induced apoptosis, increased 5-hydroxymethylcytosine (5hmC). and inhibited invasion. Our bioinformatics studies indicated that TET1 is a target gene of microRNA-17 (miR-17) Our results showed that inhibition of the expression of miR-17 resulted in increased TET1 expression in OCM-1 cells. Furthermore, our results indicated that quercetin treatment increased TET1 expression and inhibited melanoma growth in nude mice. Taken together, our results suggest that quercetin can regulate cell proliferation and apoptosis through TET1 via miR-17 in melanoma cells.

Novel Germline TET2 Mutations in Two Unrelated Patients with Autoimmune Lymphoproliferative Syndrome-Like Phenotype and Hematologic Malignancy.

Somatic mutations in the ten-eleven translocation methylcytosine dioxygenase 2 gene (TET2) have been associated to hematologic malignancies. More recently, biallelic, and monoallelic germline mutations conferring susceptibility to lymphoid and myeloid cancer have been described. We report two unrelated autoimmune lymphoproliferative syndrome-like patients who presented with T-cell lymphoma associated with novel germline biallelic or monoallelic mutations in the TET2 gene. Both patients presented a history of chronic lymphoproliferation with lymphadenopathies and splenomegaly, cytopenias, and immune dysregulation. We identified the first compound heterozygous patient for TET2 mutations (P1) and the first ALPS-like patient with a monoallelic TET2 mutation (P2). P1 had the most severe form of autosomal recessive disease due to TET2 loss of function resulting in absent TET2 expression and profound increase in DNA methylation. Additionally, the immunophenotype showed some alterations in innate and adaptive immune system as inverted myeloid/plasmacytoid dendritic cells ratio, elevated terminally differentiated effector memory CD8 + T-cells re-expressing CD45RA, regulatory T-cells, and Th2 circulating follicular T-cells. Double-negative T-cells, vitamin B12, and IL-10 were elevated according to the ALPS-like suspicion. Interestingly, the healthy P1's brother carried a TET2 mutation and presented some markers of immune dysregulation. P2 showed elevated vitamin B12, hypergammaglobulinemia, and decreased HDL levels. Therefore, novel molecular defects in TET2 confirm and expand both clinical and immunological phenotype, contributing to a better knowledge of the bridge between cancer and immunity.

Induced hepatic stem cells maintain self-renewal through the high expression of Myc coregulated by TET1 and CTCF

BackgroundInduced hepatic stem cells (iHepSCs) with the capacities of self-renewal and bidifferentiation into hepatocytes and cholangiocytes were generated from mouse embryonic fibroblasts (MEFs) by lineage reprogramming in our previous research. However, the mechanism of iHepSC self-renewal has not been elucidated. Active demethylation regulated by Tet1 plays an important role in the self-renewal of stem cells, including pluripotent stem cells and adult stem cells. Here, we investigated the role and mechanism of Tet1-regulated demethylation in the self-renewal of iHepSCs.MethodsThe methylation levels and the expression of Tet1 in iHepSCs and MEFs were analyzed by immunofluorescent staining, quantitative reverse transcription PCR and western blotting. Then, the effects of Tet1 knockdown on the proliferation and self-renewal of iHepSCs were analyzed by CCK8, colony formation, and sphere formation assays. The mechanism by which Tet1 regulates the self-renewal of iHepSCs was investigated by chromatin immunoprecipitation, bisulfite sequence PCR, and methylation-sensitive restriction endonuclease-PCR.ResultsThe high level of 5hmC and the low level of 5mC in iHepSCs were accompanied by high expression of Tet1. After Tet1 expression was knocked down by shRNA in iHepSCs, the proliferation and self-renewal capacities were inhibited, and the expression of Myc was also decreased. The higher expression level of Myc in iHepSCs maintained its self-renewal and was regulated by Tet1, which directly binds to CBS-1 and site A regions of the Myc promoter and demethylates the CpG cytosine. In addition, CTCF also binds to the CBS-1 and site A regions of the Myc promoter and regulates Myc expression along with TET1.ConclusionThe self-renewal of iHepSCs was maintained by the higher expression of Myc, which was coregulated by TET1 and CTCF. This study may provide new insights into the self-renewal of stem cells, which can promote the research and application of ‘reprogrammed’ stem cells.

Associationof vitamin B12/ferritin deficiencyin cancer patients with methylomic changes at promotors of TETmethylcytosine dioxygenases.

Aim: To investigate potential DNA methylation in methylcytosine dioxygenases and correlation of TET genes with vitamin B12/ferritin levels in cancer patients. Materials & methods: 200 blood samples were obtained from both cancer patients and healthy individuals. Results: The expression of DNMT1, DNMT3a and DNMT3b was increased in patients with low vitamin B12 and ferritin levels, while the expression of MTR, TET1 and TET3 significantly decreased. DNA methylation analysis in patients with deficient vitamin B12/ferritin levels showed methylomic changes within the location 318/CG and 385/CG in the promoter region of TET1 and TET3, respectively. Conclusion: Vitamin B12/ferritin deficiency contributes to DNA methylation progress in cancer patients.

MYCN and HIF-1 directly regulate TET1 expression to control 5-hmC gains and enhance neuroblastoma cell migration in hypoxia

ABSTRACT Ten-Eleven-Translocation 5-methylcytosine dioxygenases 1–3 (TET1-3) convert 5-methylcytosine to 5-hydroxymethylcytosine (5-hmC), using oxygen as a co-substrate. Contrary to expectations, hypoxia induces 5-hmC gains in MYCN-amplified neuroblastoma (NB) cells via upregulation of TET1. Here, we show that MYCN directly controls TET1 expression in normoxia, and in hypoxia, HIF-1 augments TET1 expression and TET1 protein stability. Through gene-editing, we identify two MYCN and HIF-1 binding sites within TET1 that regulate gene expression. Bioinformatic analyses of 5-hmC distribution and RNA-sequencing data from hypoxic cells implicate hypoxia-regulated genes important for cell migration, including CXCR4. We show that hypoxic cells lacking the two MYCN/HIF-1 binding sites within TET1 migrate slower than controls. Treatment of MYCN-amplified NB cells with a CXCR4 antagonist results in slower migration under hypoxic conditions, suggesting that inclusion of a CXCR4 antagonist into NB treatment regimens could be beneficial for children with MYCN-amplified NBs.

Investigation of perturbation of DNMT and TET enzymes in endometrial cancer (308)

Investigation of perturbation of DNMT and TET enzymes in endometrial cancer (308)

Early Expression of Tet1 and Tet2 in Mouse Zygotes Altered DNA Methylation Status and Affected Embryonic Development.

Ten-eleven translocation (Tet) dioxygenases can induce DNA demethylation by catalyzing 5-methylcytosine(5mC) to 5-hydroxymethylcytosine(5hmC), and play important roles during mammalian development. In mouse, Tet1 and Tet2 are not expressed in pronucleus-staged embryos and are not involved in the genomic demethylation of early zygotes. Here, we investigated the influence of Tet1 and Tet2 on methylation of parental genomes by ectopically expressing Tet1 and Tet2 in zygotes. Immunofluorescence staining showed a marked 5hmC increase in the maternal pronucleus after injection of Tet1 or Tet2 mRNA into zygotes. Whole-genome bisulfite sequencing further revealed that Tet2 greatly enhanced the global demethylation of both parental genomes, while Tet1 only promoted the paternal demethylation. Tet1 and Tet2 overexpression altered the DNA methylation across genomes, including various genic elements and germline-specific differently methylated regions. Tet2 exhibited overall stronger demethylation activity than Tet1. Either Tet1 or Tet2 overexpression impaired preimplantation embryonic development. These results demonstrated that early expression of Tet1 and Tet2 could substantially alter the zygotic methylation landscape and damage embryonic development. These findings provide new insights into understanding the function of Tet dioxygenases and the mechanism of DNA methylation in relation to embryogenesis.

The HDAC7-TET2 epigenetic axis is essential during early B lymphocyte development.

Correct B cell identity at each stage of cellular differentiation during B lymphocyte development is critically dependent on a tightly controlled epigenomic landscape. We previously identified HDAC7 as an essential regulator of early B cell development and its absence leads to a drastic block at the pro-B to pre-B cell transition. More recently, we demonstrated that HDAC7 loss in pro-B-ALL in infants associates with a worse prognosis. Here we delineate the molecular mechanisms by which HDAC7 modulates early B cell development. We find that HDAC7 deficiency drives global chromatin de-condensation, histone marks deposition and deregulates other epigenetic regulators and mobile elements. Specifically, the absence of HDAC7 induces TET2 expression, which promotes DNA 5-hydroxymethylation and chromatin de-condensation. HDAC7 deficiency also results in the aberrant expression of microRNAs and LINE-1 transposable elements. These findings shed light on the mechanisms by which HDAC7 loss or misregulation may lead to B cell–based hematological malignancies.