Ten-eleven translocation 1 dysfunction reduces 5-hydroxymethylcytosine expression levels in gastric cancer cells

Vitamin C enhances co-localization of novel TET1 nuclear bodies with both Cajal and PML bodies in colorectal cancer cells

Deregulation of ten-eleven Translocation protein 1 (TET1) is commonly reported to induce imbalances in gene expression and subsequently to colorectal cancer development (CRC). On the other hand, vitamin C (VitC) improves the prognosis of colorectal cancer by reprogramming the cancer epigenome and limiting chemotherapeutic drug resistance events. In this study, we aimed to characterize TET1-specific subcellular compartments and evaluate the effect of VitC on TET1 compartmentalization in colonic tumour cells. We demonstrated that TET1 is concentrated in coarse nuclear bodies (NB) and 5-hydroxymethylcytosine (5hmC) in foci in colorectal cancer cells (HCT116, Caco-2, and HT-29). To our knowledge, this is the first report of a novel intracellular localization profile of TET1 and its demethylation marker, 5hmC, in CRC cells. Interestingly, we found that TET1-NBs frequently interacted with Cajal bodies, but not with promyelocytic leukaemia (PML) bodies. In addition, we report that VitC treatment of HCT116 cells induces 5hmC foci biogenesis and triggers 5hmC marks to form active complexes with nuclear body components, including both Cajal and PML proteins. Our data highlight novel NB-concentrating TET1 in CRC cells and demonstrate that VitC modulates TET1-NBs' interactions with other nuclear structures. These findings reveal novel TET1-dependent cellular functions and potentially provide new insights for CRC management.

The level of active DNA demethylation compounds in leukocytes and urine samples as potential epigenetic biomarkers in breast cancer patients

The active DNA demethylation process, which involves TET proteins, can affect DNA methylation pattern. TET dependent demethylation results in DNA hypomethylation by oxidation 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) and its derivatives. Moreover, TETs' activity may be upregulated by ascorbate. Given that aberrant DNA methylation of genes implicated in breast carcinogenesis may be involved in tumor progression, we wanted to determine whether breast cancer patients exert changes in the active DNA demethylation process. The study included blood samples from breast cancer patients (n = 74) and healthy subjects (n = 71). We analyzed the expression of genes involved in the active demethylation process (qRT-PCR), and 5-mC and its derivatives level (2D-UPLC MS/MS). The ascorbate level was determined using UPLC-MS. Breast cancer patients had significantly higher TET3 expression level, lower 5-mC and 5-hmC DNA levels. TET3 was significantly increased in luminal B breast cancer patients with expression of hormone receptors. Moreover, the ascorbate level in the plasma of breast cancer patients was decreased with the accompanying increase of sodium-dependent vitamin C transporters (SLC23A1 and SLC23A2). The presented study indicates the role of TET3 in DNA demethylation in breast carcinogenesis.

Emerging role of interaction between m6A and main ncRNAs in gastrointestinal (GI) cancers

As a prevalent epigenetic modification, the role of m6A has been increasingly highlighted in the alteration of numerous RNAs implicated with multiple biological processes, such as formation, export, translation, and degradation. With further the understanding of m6A, accumulating evidence shows that m6A modification similarly affects metabolic process of non-coding genes. But the specifical interplay of m6A and ncRNAs (non-coding RNAs) in gastrointestinal cancers still lacks complete discussion. Thus, we analyzed and summarized how ncRNAs affect the regulators of m6A and by what means the expression of ncRNAs is altered via m6A in gastrointestinal cancers. We focused on the effect of the interaction of m6A and ncRNAs on the molecular mechanisms of malignant behavior in gastrointestinal cancers, revealing more possibilities of ncRNAs for diagnosis and treatment in term of epigenetic modification.

TET1 Isoforms Have Distinct Expression Pattern, Localization and Regulation in Breast Cancer

TET1 regulates gene expression by demethylating their regulatory sequences through the conversion of 5-methylcytosine to 5-hyroxymethylcytosine. TET1 plays important roles in tissue homeostasis. In breast cancer, TET1 was shown to play controversial roles. Moreover, TET1 has at least two isoforms (long and short) that have distinct expression pattern and apparently different functions in tissue development and disease including breast cancer. We hypothesized that TET1 isoforms have different expression patterns, localization and regulation in different types of breast cancer. To prove our hypothesis, we studied the expression of TET1 isoforms in basal and luminal breast cancer cell lines, as well as in basal and luminal breast cancer animal models. We also studied the effect of different hormones on the expression of the two isoforms. Moreover, we assessed the distribution of the isoforms between the cytoplasm and nucleus. Finally, we overexpressed the full length in a breast cancer cell line and tested its effect on cancer cell behavior. In this study, we demonstrate that while Estrogen and GnRH downregulate the expression of long TET1, they lead to upregulation of short TET1 expression. In addition, we uncovered that luminal cells show higher expression level of the long isoform. We also show that while all TET1 isoforms are almost depleted in a basal breast cancer animal model, the expression of the short isoform is induced in luminal breast cancer model. The short form is expressed mainly in the cytoplasm while the long isoform is expressed mainly in the nucleus. Finally, we show that long TET1 overexpression suppresses cell oncogenic phenotypes. In conclusion, our data suggest that TET1 isoforms have distinct expression pattern, localization and regulation in breast cancer and that long TET1 suppresses oncogenic phenotypes, and that further studies are necessary to elucidate the functional roles of different TET1 isoforms in breast cancer.

Tracing TET1 expression in prostate cancer: discovery of malignant cells with a distinct oncogenic signature

Background

Ten–eleven translocation methylcytosine dioxygenase 1 (TET1) is involved in DNA demethylation and transcriptional regulation, plays a key role in the maintenance of stem cell pluripotency, and is dysregulated in malignant cells. The identification of cancer stem cells (CSCs) driving tumor growth and metastasis is the primary objective of biomarker discovery in aggressive prostate cancer (PCa). In this context, we analyzed TET1 expression in PCa.

Methods

A large-scale immunohistochemical analysis of TET1 was performed in normal prostate (NOR) and PCa using conventional slides (50 PCa specimens) and tissue microarrays (669 NOR and 1371 PCa tissue cores from 371 PCa specimens). Western blotting, RT-qPCR, and 450 K methylation array analyses were performed on PCa cell lines. Genome-wide correlation, gene regulatory network, and functional genomics studies were performed using publicly available data sources and bioinformatics tools.

Results

In NOR, TET1 was exclusively expressed in normal cytokeratin 903 (CK903)–positive basal cells. In PCa, TET1 was frequently detected in alpha-methylacyl-CoA racemase (AMACR)–positive tumor cell clusters and was detectable at all tumor stages and Gleason scores. Pearson’s correlation analyses of PCa revealed 626 TET1-coactivated genes (r > 0.5) primarily encoding chromatin remodeling and mitotic factors. Moreover, signaling pathways regulating antiviral processes (62 zinc finger, ZNF, antiviral proteins) and the pluripotency of stem cells were activated. A significant proportion of detected genes exhibited TET1-correlated promoter hypomethylation. There were 161 genes encoding transcription factors (TFs), of which 133 were ZNF-TFs with promoter binding sites in TET1 and in the vast majority of TET1-coactivated genes.

Conclusions

TET1-expressing cells are an integral part of PCa and may represent CSCs with oncogenic potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01201-7.

Global DNA 5hmC and CK195hmC+ Contents: A Promising Biomarker for Predicting Prognosis in Small Hepatocellular Carcinoma

Background: 5-Hydroxymethylcytosine (5hmC) with dynamic existence possesses multiple regulatory functions. Whereas, 5hmC’s impact on small hepatocellular carcinoma (SHCC) remains unclear. The present work focused on characterizing 5hmC content within SHCC and assessing the possibility of using global genomic 5hmC level as the predicative factor of clinical outcome. Methods: This study applied ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) in measuring 5mC, 5fC and 5hmC contents. In addition, immunohistochemistry (IHC) was adopted to measure CK19 and 5hmC contents. Results: Research showed 5mC, 5hmC, and 5fC contents from global genomics of SHCC reduced extensively compared with healthy samples (p < 0.001). Moreover, SHCC was associated with lymph node metastasis (LNM). Greater 5mC and 5hmC levels were observed in non-metastasis group compared with the metastasis group (p < 0.001). Correlation analysis between the HBV DNA level and 5mC, 5fC and 5hmC levels exhibited that HBV DNA was associated with 5mC, 5hmC, and 5fC content reduction, which was verified in the cytological experiments. Moreover, 5hmC content had a negative correlation with the expression level of CK19 in SHCC. The decrease in 5hmC and CK19 containing 5hmC positive cell (called CK19^5hmC+) should be ascribed to the bad prognosis among SHCC patients. Conclusions: The contents of 5hmC and CK19^5hmC+ of genomic DNA might be adopted for predicting SHCC survival as an important biomarker.

Ten-eleven translocase: key regulator of the methylation landscape in cancer

PURPOSE

Methylation of 5th residue of cytosine in CpG island forms 5-methylcytosine which is stable, heritable epigenetic mark. Methylation levels are broadly governed by methyltransferases and demethylases. An aberration in the demethylation process contributes to the silencing of gene expression. Ten eleven translocation (TET) dioxygenase (1-3) the de novo demethylase is responsible for conversion of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC), 5-formylcytosisne (5-fC) and 5-carboxycytosine (5-caC) during demethylation process. Mutations and abnormal expression of TET proteins contribute to carcinogenesis. Discovery of TET proteins has offered various pathways for the reversal of methylation levels thus, enhancing our knowledge as to how methylation effects cancer progression.

METHODS

We searched "PubMed" and "Google scholar" databases and selected studies with the following keywords "TET enzyme", "cancer", "5-hmC", and "DNA demethylation". In this review, we have discussed combinatorial use of vitamin C in inhibiting tumour growth by enhancing the catalytic activity of TET enzymes and consequently, increasing the 5-hmC levels. 5-Hydroxymethylcytosine holds promise as a prognostic biomarker in solid cancers. The contribution of induction and suppression of TET enzymes and 5-hmC carcinogenesis are discussed in haematological and solid cancers.

RESULTS

We found that TET enzymes play central role in maintaining the methylation balance. Any anomaly in their expression may dip the balance towards cancer progression. Low levels of TET enzymes and 5-hmC correlate with tumour invasion, progression and metastasis. Also, use of vitamin C enhances TET activity.

CONCLUSION

TET enzymes play vital role in shaping the methylation landscape in body. 5-hmC can be used as prognostic marker in solid cancers.

Multi-Omics Characterization of Inflammatory Bowel Disease-Induced Hyperplasia/Dysplasia in the Rag2-/-/Il10-/- Mouse Model

Epigenetic dysregulation is hypothesized to play a role in the observed association between inflammatory bowel disease (IBD) and colon tumor development. In the present work, DNA methylome, hydroxymethylome, and transcriptome analyses were conducted in proximal colon tissues harvested from the Helicobacter hepaticus (H. hepaticus)-infected murine model of IBD. Reduced representation bisulfite sequencing (RRBS) and oxidative RRBS (oxRRBS) analyses identified 1606 differentially methylated regions (DMR) and 3011 differentially hydroxymethylated regions (DhMR). These DMR/DhMR overlapped with genes that are associated with gastrointestinal disease, inflammatory disease, and cancer. RNA-seq revealed pronounced expression changes of a number of genes associated with inflammation and cancer. Several genes including Duox2, Tgm2, Cdhr5, and Hk2 exhibited changes in both DNA methylation/hydroxymethylation and gene expression levels. Overall, our results suggest that chronic inflammation triggers changes in methylation and hydroxymethylation patterns in the genome, altering the expression of key tumorigenesis genes and potentially contributing to the initiation of colorectal cancer.

LncRNA NUTM2A-AS1 positively modulates TET1 and HIF-1A to enhance gastric cancer tumorigenesis and drug resistance by sponging miR-376a

Long noncoding RNA NUTM2A‐AS1 has been shown to be dysregulated in non‐small cell lung carcinoma. To date, it is unclear whether NUTM2A‐AS1 plays a role in gastric cancer progression. The purpose of this study is to elucidate the molecular mechanism of the role of NUTM2A‐AS1 in gastric cancer. mRNA and protein levels were measured by RT‐qPCR and western blot methods. Invasion ability was examined by transwell assay. Cell viability was determined by MTT assay. Dual‐luciferase assay, RNA pull down, and RNA immunoprecipitation were used to confirm direct binding of between miR‐376a and NUTM2A‐AS1 or TET1. Xenografting tumor assay and TCGA analysis showed the contributory role of NUTM2A‐AS1 in vivo and human clinical setting. Our results suggested that NUTM2A‐AS1 promoted cell viability, invasion, and drug resistance of gastric cancer cells, which was largely rescued by miR‐376a. More interestingly, TET1 and HIF‐1A were negatively regulated by miR‐376a. TET1 could interact with HIF‐1A to modulate PD‐L1. Finally, we revealed that PD‐L1 was key to NUTM2A‐AS1‐ and miR‐376a‐mediated tumorigenesis and drug resistance. In summary, our conclusions facilitate us understand the underlying mechanism and develop novel treatment strategy for gastric cancer.

LINC01089 is a tumor-suppressive lncRNA in gastric cancer and it regulates miR-27a-3p/TET1 axis

Background

Gastric cancer (GC) is one of the most common malignancies around the world. Recently, the role of long non-coding RNA (lncRNA) in cancer biology has become a hot research topic. This work aimed to explore the biological function and underlying mechanism of LINC01089 in GC.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to investigate the expression of LINC01089 in GC tissues and cells. The relationship between the expression level of LINC01089 and the clinicopathological parameters of GC was assessed. Cell models of LINC01089 overexpression, LINC01089 knockdown, miR-27a-3p overexpression, and miR-27a-3p inhibition were established by transfection. CCK-8 assay, BrdU assay, and Transwell assay were utilized to investigate the malignant biological behaviors of GC cell lines after transfection. Dual luciferase activity reporter assay, Pearson’s correlation analysis, and Western blot were utilized to the regulatory relationships among LINC01089, miR-27a-3p and tet methylcytosine dioxygenase 1 (TET1).

Result

LINC01089 down-regulation was observed in GC tissues and cell lines. Low expression level of LINC01089 in GC tissues was markedly linked to larger tumor size, higher T stage, as well as lymphatic metastasis of the patients. Functional experiments implied that LINC01089 overexpression impeded the proliferation, migration, as well as invasion of GC cells, whereas LINC01089 knockdown promoted the above malignant phenotypes. Additionally, up-regulation of miR-27a-3p was also observed in GC tissues. Functional experiments also showed that, miR-27a-3p overexpression boosted the malignant biological behaviors of GC cells; on the contrast, these phenotypes were impeded by miR-27a-3p inhibition. Moreover, LINC01089 interacted with and repressed miR-27a-3p, and miR-27a-3p antagonized the impact of LINC01089 on GC cells. Additionally, TET1 was verified as a target gene of miR-27a-3p, and could be positively regulated by LINC01089.

Conclusion

LINC01089 impedes the proliferation, migration, and invasion of GC cells by adsorbing miR-27a-3p and up-regulating the expression of TET1.

Neuroprotective Effect of Piracetam against Cocaine-Induced Neuro Epigenetic Modification of DNA Methylation in Astrocytes

Cocaine abuse is known to alter mitochondrial biogenesis and induce epigenetic modification linked with neuronal dysfunction. Cocaine-induced epigenetic modification of DNA methylation and the mitochondrial genome may affect mitochondrial DNA (mtDNA) and nuclear DNA (nDNA), as epigenetic DNA methylation is key to maintaining genomic integrity in the central nervous system (CNS). However, the impact of cocaine-mediated epigenetic changes in astrocytes has not yet been elucidated. In this study, we explored the neuroprotective effect of piracetam against cocaine-induced epigenetic changes in DNA methylation in astrocytes. To study our hypothesis, we exposed human astrocytes to cocaine alone or in combination with the nootropic drug piracetam. We examined the expression of the DNA methyltransferases (DNMTs) DNMT-1, DNMT-3A, and DNMT-3B; global DNA methylation levels of 5-methycytosine (5-mC); and induction of ten-eleven translocation (TET) enzymes in astrocytes. In addition, we analyzed mtDNA methylation by targeted next-generation bisulfite sequencing. Our data provide evidence that cocaine impairs DNMT activity and thereby has impacts on mtDNA, which might contribute to the neurodegeneration observed in cocaine users. These effects might be at least partially prevented by piracetam, allowing neuronal function to be maintained.

Chrysin Induced Cell Apoptosis and Inhibited Invasion Through Regulation of TET1 Expression in Gastric Cancer Cells

Objective

Ten-eleven translocation (TET) enzymes that oxidize a 5-methylcytosine (5mC) to yield 5-hydroxymethylcytosine (5hmC) have been responsible for fine-tuning methylation patterns and exhibit role in epigenetic modifications. Chrysin, a natural flavone frequently present in honey, has been recognized to exhibit anti-tumor properties. In this study, we investigated the effects of Chrysin in the expression pattern of TET proteins in gastric cancer (GC) cells.

Materials and Methods

Using qRT-PCR and Western blot analysis, we analyzed the expression of TET1 in GC cells in vitro following treatment with Chrysin. Immunofluorescence staining detected the expression levels of 5mC and 5hmC. Flow cytometry, wound healing, and Matrigel invasion assays were performed to determine cell proliferation, cell cycle, apoptosis, and migration and invasion of GC cells following treatment with Chrysin, si-TET1, and TET1-KO. Furthermore, a xenograft model was developed to analyze the expression pattern of TET1 on tumor development in vivo.

Results

qRT-PCR and Western blot assays indicated that treatment with Chrysin significantly promoted the expression of TET1 in GC cells. Immunofluorescence study further confirmed that TET1 and 5hmC levels were significantly enhanced following treatment with Chrysin in MKN45 cells. Moreover, our results suggested that Chrysin could noticeably induce cell apoptosis and inhibit cell migration and invasion. Further, knockdown and overexpression of TET1 were conducted to investigate whether TET1 expression affected cell apoptosis, and cell migration and invasion in MKN45 cells. The results indicated that overexpression of TET1 markedly promoted cell apoptosis and inhibited cell migration and invasion. Furthermore, the TET1 gene knocked out was generated using the CRISPR/Cas9 system. Our data suggested that TET1 expression was associated with GC tumor growth in vivo.

Conclusion

This study indicated that Chrysin exerted anti-tumor effects through the regulation of TET1 expression in GC and presented TET1 as a novel promising therapeutic target for GC therapy.

Methylation Dynamics of RASSF1A and Its Impact on Cancer

5-methyl cytosine (5mC) is a key epigenetic mark entwined with gene expression and the specification of cellular phenotypes. Its distribution around gene promoters sets a barrier for transcriptional enhancers or inhibitor proteins binding to their target sequences. As a result, an additional level of regulation is added to the signals that organize the access to the chromatin and its structural components. The tumor suppressor gene RASSF1A is a microtubule-associated and multitasking scaffold protein communicating with the RAS pathway, estrogen receptor signaling, and Hippo pathway. RASSF1A action stimulates mitotic arrest, DNA repair and apoptosis, and controls the cell cycle and cell migration. De novo methylation of the RASSF1A promoter has received much attention due to its increased frequency in most cancer types. RASSF1A methylation is preceded by histones modifications and could represent an early molecular event in cell transformation. Accordingly, RASSF1A methylation is proposed as an epigenetic candidate marker in many cancer types, even though an inverse correlation of methylation and expression remains to be fully ascertained. Some findings indicate that the epigenetic abrogation of RASSF1A can promote the alternative expression of the putative oncogenic isoform RASSF1C. Understanding the complexity and significance of RASSF1A methylation is instrumental for a more accurate determination of its biological and clinical role. The review covers the molecular events implicated in RASSF1A methylation and gene silencing and provides a deeper view into the significance of the RASSF1A methylation patterns in a number of gastrointestinal cancer types.