Global DNA 5-Hydroxymethylcytosine and 5-Formylcytosine Contents Are Decreased in the Early Stage of Hepatocellular Carcinoma

Epstein-Barr virus-driven metabolic alterations contribute to the viral lytic reactivation and tumor progression in nasopharyngeal carcinoma

Metabolic reprogramming induced by Epstein-Barr virus (EBV) often mirrors metabolic changes observed in cancer cells. Accumulating evidence suggests that lytic reactivation is crucial in EBV-associated oncogenesis. The aim of this study was to explore the role of metabolite changes in EBV-associated malignancies and viral life cycle control. We first revealed that EBV (LMP1) accelerates the secretion of the oncometabolite D-2HG, and serum D-2HG level is a potential diagnostic biomarker for NPC. EBV (LMP1)-driven metabolite changes disrupts the homeostasis of global DNA methylation and demethylation, which have a significantly inhibitory effect on active DNA demethylation and 5hmC content. We found that loss of 5hmC indicates a poor prognosis for NPC patients, and that 5hmC modification is a restriction factor of EBV reactivation. We confirmed a novel EBV reactivation inhibitor, α-KG, which inhibits the expression of EBV lytic genes with CpG-containing ZREs and the latent-lytic switch by enhancing 5hmC modification. Our results demonstrate a novel mechanism of which metabolite abnormality driven by EBV controls the viral lytic reactivation through epigenetic modification. This study presents a potential strategy for blocking EBV reactivation, and provides potential targets for the diagnosis and therapy of NPC.

TET2 Is Downregulated in Early Esophageal Squamous Cell Carcinoma and Promotes Esophageal Squamous Cell Malignant Behaviors

OBJECTIVE

To explore the expression of the ten eleven translocation (TET) 2 protein in early esophageal squamous cell carcinoma (EESCC), precancerous lesions, and cell lines and to evaluate the effect of TET2 on the functional behavior of EC109 esophageal cancer cells.

METHODS

Thirty-one samples of EESCC and precancerous lesions collected via endoscopic submucosal dissection at Taihe Hospital, Shiyan, from February 1, 2017, to February 1, 2019, were analyzed. The study involved evaluating TET2 expression levels in lesion tissue and adjacent normal epithelium, correlating these with clinical pathological features. Techniques including 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide, cell scratch assays, flow cytometry for propidium iodide (PI) staining, Hoechst 333258/PI double staining, and nude mouse tumorigenesis experiments were employed to assess the effect of TET2 on the proliferation, migration, cell cycle, apoptosis, and tumorigenic ability of esophageal cancer cells.

RESULTS

TET2 expression was notably reduced in early esophageal cancer tissue and correlated with tumor invasion depth (P < 0.05). Overexpression of TET2 enhanced the proliferation and migration of esophageal cancer cells, increased the cell population in the G0 phase, decreased it in the S phase, and intensified cell necrosis (P < 0.05). There was a partial increase in tumorigenic ability (P = 0.087).

CONCLUSION

TET2 downregulation in ESCC potentially influences the necrosis, cell cycle, and tumorigenic ability of esophageal cancer cells, suggesting a role in the onset and progression of esophageal cancer.

The Role of 5-Hydroxymethylcytosine as a Potential Epigenetic Biomarker in a Large Series of Thyroid Neoplasms

Cytosine modifications at the 5-carbon position play a critical role in gene expression regulation and have been implicated in cancer development. 5-Hydroxymethylcytosine (5hmC), arising from 5-methylcytosine (5-mC) oxidation, has shown promise as a potential malignancy marker due to its depletion in various human cancers. However, its significance in thyroid tumors remains underexplored, primarily due to limited data. In our study, we evaluated 5hmC expression levels by immunohistochemistry in a cohort of 318 thyroid tumors. Our analysis revealed significant correlations between 5hmC staining extension scores and nodule size, vascular invasion, and oncocytic morphology. Nuclear 5hmC staining intensity demonstrated associations with focality, capsule status, extrathyroidal extension, vascular invasion, and oncocytic morphology. Follicular/oncocytic adenomas exhibited higher 5hmC expression than uncertain malignant potential (UMP) or noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), as well as malignant neoplasms, including papillary thyroid carcinomas (PTCs), oncocytic carcinomas (OCAs), follicular thyroid carcinomas (FTCs), and invasive encapsulated follicular variants of PTC (IEFV-PTC). TERT promoter mutation cases showed notably lower values for the 5hmC expression, while RAS (H, N, or K) mutations, particularly HRAS mutations, were associated with higher 5hmC expression. Additionally, we identified, for the first time, a significant link between 5hmC expression and oncocytic morphology. However, despite the merits of these discoveries, we acknowledge that 5hmC currently cannot segregate minimally invasive from widely invasive tumors, although 5hmC levels were lower in wi-FPTCs. Further research is needed to explore the potential clinical implications of 5hmC in thyroid tumors.

Cell-Free DNA 5-Hydroxymethylcytosine Signatures for Lung Cancer Prognosis

Accurate prognostic markers are essential for guiding effective lung cancer treatment strategies. The level of 5-hydroxymethylcytosine (5hmC) in tissue is independently associated with overall survival (OS) in lung cancer patients. We explored the prognostic value of cell-free DNA (cfDNA) 5hmC through genome-wide analysis of 5hmC in plasma samples from 97 lung cancer patients. In both training and validation sets, we discovered a cfDNA 5hmC signature significantly associated with OS in lung cancer patients. We built a 5hmC prognostic model and calculated the weighted predictive scores (wp-score) for each sample. Low wp-scores were significantly associated with longer OS compared to high wp-scores in the training [median 22.9 versus 8.2 months; p = 1.30 × 10-10; hazard ratio (HR) 0.04; 95% confidence interval (CI), 0.00-0.16] and validation (median 18.8 versus 5.2 months; p = 0.00059; HR 0.22; 95% CI: 0.09-0.57) sets. The 5hmC signature independently predicted prognosis and outperformed age, sex, smoking, and TNM stage for predicting lung cancer outcomes. Our findings reveal critical genes and signaling pathways with aberrant 5hmC levels, enhancing our understanding of lung cancer pathophysiology. The study underscores the potential of cfDNA 5hmC as a superior prognostic tool for guiding more personalized therapeutic strategies for lung cancer patients.

Hypomethylation of glycine dehydrogenase promoter in peripheral blood mononuclear cells is a new diagnostic marker of hepatitis B virus-associated hepatocellular carcinoma

BACKGROUND

Glycine dehydrogenase (GLDC) plays an important role in the initiation and proliferation of several human cancers. In this study, we aimed to detect the methylation status of GLDC promoter and its diagnostic value for hepatitis B virus-associated hepatocellular carcinoma (HBV-HCC).

METHODS

We enrolled 197 patients, 111 with HBV-HCC, 51 with chronic hepatitis B (CHB), and 35 healthy controls (HCs). The methylation status of GLDC promoter in peripheral mononuclear cells (PBMCs) was identified by methylation specific polymerase chain reaction (MSP). The mRNA expression was examined using real-time quantitative polymerase chain reaction (qPCR).

RESULTS

The methylation frequency of the GLDC promoter was significantly lower in HBV-HCC patients (27.0%) compared to that in CHB patients (68.6%) and HCs (74.3%) (P < 0.001). The methylated group had lower alanine aminotransferase level (P = 0.035) and lower rates of tumor node metastasis (TNM) III/IV (P = 0.043) and T3/T4 (P = 0.026). TNM stage was identified to be an independent factor for GLDC promoter methylation. GLDC mRNA levels in CHB patients and HCs were significantly lower than those in HBV-HCC patients (P = 0.022 and P < 0.001, respectively). GLDC mRNA levels were significantly higher in HBV-HCC patients with unmethylated GLDC promoters than those with methylated GLDC promoters (P = 0.003). The diagnostic accuracy of alpha-fetoprotein (AFP) combined with GLDC promoter methylation for HBV-HCC was improved compared with that of AFP alone (AUC: 0.782 vs. 0.630, P < 0.001). In addition, GLDC promoter methylation was an independent predictor for overall survival of HBV-HCC patients (P = 0.038).

CONCLUSIONS

The methylation frequency of GLDC promoter was lower in PBMCs from HBV-HCC patients than that from patients with CHB and HCs. The combination of AFP and GLDC promoter hypomethylation significantly improved the diagnostic accuracy of HBV-HCC.

TET2-mediated tumor cGAS triggers endothelial STING activation to regulate vasculature remodeling and anti-tumor immunity in liver cancer

Induction of tumor vascular normalization is a crucial measure to enhance immunotherapy efficacy. cGAS-STING pathway is vital for anti-tumor immunity, but its role in tumor vasculature is unclear. Herein, using preclinical liver cancer models in Cgas/Sting-deficient male mice, we report that the interdependence between tumor cGAS and host STING mediates vascular normalization and anti-tumor immune response. Mechanistically, TET2 mediated IL-2/STAT5A signaling epigenetically upregulates tumor cGAS expression and produces cGAMP. Subsequently, cGAMP is transported via LRRC8C channels to activate STING in endothelial cells, enhancing recruitment and transendothelial migration of lymphocytes. In vivo studies in male mice also reveal that administration of vitamin C, a promising anti-cancer agent, stimulates TET2 activity, induces tumor vascular normalization and enhances the efficacy of anti-PD-L1 therapy alone or in combination with IL-2. Our findings elucidate a crosstalk between tumor and vascular endothelial cells in the tumor immune microenvironment, providing strategies to enhance the efficacy of combinational immunotherapy for liver cancer.

MDM2 Antagonist Nutlin-3 Stimulates Global DNA Hydroxymethylation by Enhancing p53-TET1 Signaling Axis

DNA hydroxymethylation is involved in many biological processes, including nuclear reprogramming, embryonic development, and tumor suppression. In this study, we report that an anticancer agent, nutlin-3, selectively stimulates global DNA hydroxymethylation in TP53 wild-type cancer cells as manifested by the elevation of 5-hydroxymethylcytosine (5hmC) in genomic DNA. In contrast, nutlin 3 fails to enhance DNA hydroxymethylation in TP53-mutated cancer cells. Consistently, nutlin-3 as a MDM2 antagonist only activates wild-type but not mutated TP53. Furthermore, nutlin-3 does not alter the expression of TET1 but slightly reduces the expression of TET2 and TET3 proteins. These TET family proteins are responsible for converting 5-methylcytosine (5mC) to 5hmC. Interestingly, TET1 knockdown could significantly block the nutlin-3-induced DNA hydroxymethylation as well as TP53 and P21 activation. Immunoprecipitation analysis supports that p53 strongly interacts with TET1 proteins. These results suggest that nutlin-3 activates TP53 and promotes p53-TET1 interaction. As positive feedback, the p53-TET1 interaction further enhances p53 activation and promotes apoptosis. Collectively, we demonstrate that nutlin-3 stimulates DNA hydroxymethylation and apoptosis via a positive feedback mechanism.

Advances in biomarker discovery using circulating cell-free DNA for early detection of hepatocellular carcinoma

The past several decades have witnessed unprecedented progress in basic and clinical cancer research, and our understanding of the molecular mechanisms and pathogenesis of cancers have been greatly improved. More recently, with the availability of high-throughput sequencing and profiling platforms as well as sophisticated analytical tools and high-performance computing capacity, there have been tremendous advances in the development of diagnostic approaches in clinical oncology, especially the discovery of novel biomarkers for cancer early detection. Although tissue biopsy-based pathology has been the "gold standard" for cancer diagnosis, notable limitations such as the risk due to invasiveness and the bias due to intra-tumoral heterogeneity have limited its broader applications in oncology (e.g., screening, regular disease monitoring). Liquid biopsy analysis that exploits the genetic and epigenetic information contained in DNA/RNA materials from body fluids, particularly circulating cell-free DNA (cfDNA) in the blood, has been an intriguing alternative approach because of advantageous features such as sampling convenience and minimal invasiveness. Taking advantage of innovative enabling technologies, cfDNA has been demonstrated for its clinical potential in cancer early detection, including hepatocellular carcinoma (HCC), the most common liver cancer that causes serious healthcare burden globally. Hereby, we reviewed the current advances in cfDNA-based approaches for cancer biomarker discovery, with a focus on recent findings of cfDNA-based early detection of HCC. Future clinical investigations and trials are warranted to further validate these approaches for early detection of HCC, which will contribute to more effective prevention, control, and intervention strategies with the ultimate goal of reducing HCC-associated mortality. This article is categorized under: Cancer > Genetics/Genomics/Epigenetics.

Progress on the molecular mechanism of portal vein tumor thrombosis formation in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors, with poor prognosis and high mortality. Early-stage HCC has no obvious clinical symptoms, and most patients are already at an advanced stage when they are diagnosed. Portal vein tumor thrombus (PVTT) is the most common complication and a poor prognostic factor for HCC, which frequently leads to portal vein hypertension, ascites, gastrointestinal bleeding, and tumor metastasis. The formation of PVTT is related to the complex structure and hemodynamic changes of the portal vein and is closely related to changes at the cellular and molecular levels. The differentially-expressed genes (DEGs) between PVTT and primary tumor (PT) suggest that the two tissues may have different clonal origins. Epigenetic and proteomic analyses also suggest complex and diverse mechanisms for the formation of PVTT. In addition, the tumor microenvironment and energy metabolism pathways are interrelated in regulating the invasion and progression of PVTT. Aerobic glycolysis and the tumor immune microenvironment have been the focus of recent studies on PVTT. In this review, we summarize the mechanism of PVTT formation at the cellular and molecular levels to provide information to guide better prevention and treatment of PVTT in the clinic.

Relevance of HBx for Hepatitis B Virus-Associated Pathogenesis

The hepatitis B virus (HBV) counts as a major global health problem, as it presents a significant causative factor for liver-related morbidity and mortality. The development of hepatocellular carcinomas (HCC) as a characteristic of a persistent, chronic infection could be caused, among others, by the pleiotropic function of the viral regulatory protein HBx. The latter is known to modulate an onset of cellular and viral signaling processes with emerging influence in liver pathogenesis. However, the flexible and multifunctional nature of HBx impedes the fundamental understanding of related mechanisms and the development of associated diseases, and has even led to partial controversial results in the past. Based on the cellular distribution of HBx-nuclear-, cytoplasmic- or mitochondria-associated-this review encompasses the current knowledge and previous investigations of HBx in context of cellular signaling pathways and HBV-associated pathogenesis. In addition, particular focus is set on the clinical relevance and potential novel therapeutic applications in the context of HBx.

Hydroxymethylation and Epigenetic Drugs: New Insights into the Diagnosis and Treatment in Epigenetics of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal and heterogeneous malignancy with multiple genetic alternations and complex signaling pathways. The complexity and multifactorial nature of HCC pose a tremendous challenge regarding its diagnosis and treatment. Emerging evidence has indicated an important regulatory role of epigenetic modifications in HCC initiation and progression. Epigenetic modifications are stably heritable gene expression traits caused by changing the accessibility of chromatin structure and genetic activity without alteration in the DNA sequence and have been gradually recognized as a hallmark of cancer. In addition, accumulating data suggest a potential value of altered hydroxymethylation in epigenetic modifications and therapeutics targeting the epigenetically mediated regulation. As such, probing the epigenetic field in the era of precision oncology is a valid avenue for promoting the accuracy of early diagnosis and improving the oncological prognosis of HCC patients. This review focuses on the diagnostic performance and clinical utility of 5-hydroxymethylated cytosine, the primary intermediate product of the demethylation process, for early HCC diagnosis and discusses the promising applications of epigenetic-based therapeutic regimens for HCC.

Loss of 5-hydroxymethylcytosine induces chemotherapy resistance in hepatocellular carcinoma via the 5-hmC/PCAF/AKT axis

Multidrug resistance is a major challenge in treating advanced hepatocellular carcinoma (HCC). Although recent studies have reported that the multidrug resistance phenotype is associated with abnormal DNA methylation in cancer cells, the epigenetic mechanism underlying multidrug resistance remains unknown. Here, we reported that the level of 5-hydroxymethylcytosine (5-hmC) in human HCC tissues was significantly lower than that in adjacent liver tissues, and reduced 5-hmC significantly correlated with malignant phenotypes, including poor differentiation and microvascular invasion; additionally, loss of 5-hmC was related to chemotherapy resistance in post-transplantation HCC patients. Further, the 5-hmC level was regulated by ten-eleven translocation 2 (TET2), and the reduction of TET2 in HCC contributes to chemotherapy resistance through histone acetyltransferase P300/CBP-associated factor (PCAF) inhibition and AKT signaling hyperactivation. In conclusion, loss of 5-hmC induces chemotherapy resistance through PCAF/AKT axis and is a promising chemosensitivity prediction biomarker and therapeutic target for HCC patients.

Epigenetically programmed resistance to chemo- and immuno-therapies

Resistance to cancer treatments remains a major barrier in developing cancer cures. While promising combination chemotherapy treatments and novel immunotherapies have improved patient outcomes, resistance to these treatments remains poorly understood. New insights into the dysregulation of the epigenome show how it promotes tumor growth and resistance to therapy. By altering control of gene expression, tumor cells can evade immune cell recognition, ignore apoptotic cues, and reverse DNA damage induced by chemotherapies. In this chapter, we summarize the data on epigenetic remodeling during cancer progression and treatment that enable cancer cell survival and describe how these epigenetic changes are being targeted clinically to overcome resistance.

Insights into the role of nucleotide methylation in metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is a chronic liver disease characterized by fatty infiltration of the liver. In recent years, the MAFLD incidence rate has risen and emerged as a serious public health concern. MAFLD typically progresses from the initial hepatocyte steatosis to steatohepatitis and then gradually advances to liver fibrosis, which may ultimately lead to cirrhosis and carcinogenesis. However, the potential evolutionary mechanisms still need to be clarified. Recent studies have shown that nucleotide methylation, which was directly associated with MAFLD's inflammatory grading, lipid synthesis, and oxidative stress, plays a crucial role in the occurrence and progression of MAFLD. In this review, we highlight the regulatory function and associated mechanisms of nucleotide methylation modification in the progress of MAFLD, with a particular emphasis on its regulatory role in the inflammation of MAFLD, including the regulation of inflammation-related immune and metabolic microenvironment. Additionally, we summarize the potential value of nucleotide methylation in the diagnosis and treatment of MAFLD, intending to provide references for the future investigation of MAFLD.

Metabolic regulation of cholestatic liver injury by D-2-hydroxyglutarate with the modulation of hepatic microenvironment and the mammalian target of rapamycin signaling

Biliary atresia (BA) is a cholestatic liver disease in neonates with devastating obstructive intrahepatic and extrahepatic biliary ducts. Owing to the lack of an early diagnostic marker and limited understanding of its pathogenesis, BA often leads to death within 2 years. Therefore, this study aimed to develop early diagnostic methods and investigate the underlying pathogenesis of liver injury in BA using metabolomics. Metabolomics and organoid combined energy metabolism analysis was used to obtain new insights into BA diagnosis and pathobiology using patient samples, mice liver organoids, and a zebrafish model. Metabolomics revealed that D-2-hydroxyglutarate (D-2-HG) levels were significantly elevated in the plasma and liver of patients with BA and closely correlated with liver injuries and impaired liver regeneration. D-2-HG suppressed the growth and expansion of liver organoids derived from the intrahepatic biliary ducts. The energy metabolism analysis demonstrated that D-2-HG inhibited mitochondrial respiration and ATP synthase; however, it increased aerobic glycolysis in organoids. In addition, D-2-HG exposure caused liver degeneration in zebrafish larvae. Mechanistically, D-2-HG inhibited the activation of protein kinase B and the mammalian target of rapamycin signaling. These findings reveal that D-2-HG may represent a novel noninvasive diagnostic biomarker and a potential therapeutic target for infants with BA.

Ultrasensitive Simultaneous Detection of Multiple Rare Modified Nucleosides as Promising Biomarkers in Low-Put Breast Cancer DNA Samples for Clinical Multi-Dimensional Diagnosis

Early cancer diagnosis is essential for successful treatment and prognosis, and modified nucleosides have attracted widespread attention as a promising group of cancer biomarkers. However, analyzing these modified nucleosides with an extremely low abundance is a great challenge, especially analyzing multiple modified nucleosides with a different abundance simultaneously. In this work, an ultrasensitive quantification method based on chemical labeling, coupled with LC-MS/MS analysis, was established for the simultaneous quantification of 5hmdC, 5fdC, 5hmdU and 5fdU. Additionally, the contents of 5mdC and canonical nucleosides could be obtained at the same time. Upon derivatization, the detection sensitivities of 5hmdC, 5fdC, 5hmdU and 5fdU were dramatically enhanced by several hundred times. The established method was further applied to the simultaneous detection of nine nucleosides with different abundances in about 2 μg genomic DNA of breast tissues from 20 breast cancer patients. The DNA consumption was less than other overall reported quantification methods, thereby providing an opportunity to monitor rare, modified nucleosides in precious samples and biology processes that could not be investigated before. The contents of 5hmdC, 5hmdU and 5fdU in tumor tissues and normal tissues adjacent to the tumor were significantly changed, indicating that these three modified nucleosides may play certain roles in the formation and development of tumors and be potential cancer biomarkers. While the detection rates of 5hmdC, 5hmdU and 5fdU alone as a biomarker for breast cancer samples were 95%, 75% and 85%, respectively, by detecting these three cancer biomarkers simultaneously, two of the three were 100% consistent with the overall trend. Therefore, simultaneous detection of multiple cancer biomarkers in clinical samples greatly improved the accuracy of cancer diagnosis, indicating that our method has great application potential in clinical multidimensional diagnosis.

5-Hydroxymethylation alterations in cell-free DNA reflect molecular distinctions of diffuse large B cell lymphoma at different primary sites

Background

5-Hydroxymethylcytosine (5hmC), an important DNA epigenetic modification, plays a vital role in tumorigenesis, progression and prognosis in many cancers. Diffuse large B cell lymphoma (DLBCL) can involve almost any organ, but the prognosis of patients with DLBCL at different primary sites varies greatly. Previous studies have shown that 5hmC displays a tissue-specific atlas, but its role in DLBCLs at different primary sites remains unknown.

Results

We found that primary gastric DLBCL (PG-DLBCL) and lymph node-involved DLBCL (LN-DLBCL) patients had a favorable prognosis, while primary central nervous system DLBCL (PCNS-DLBCL) patients faced the worst prognosis, followed by primary testicular DLBCL (PT-DLBCL) and primary intestinal DLBCL (PI-DLBCL) patients. Thus, we used hmC-CATCH, a bisulfite-free and cost-effective 5hmC detection technology, to first generate the 5hmC profiles from plasma cell-free DNA (cfDNA) of DLBCL patients at these five different primary sites. Specifically, we found robust cancer-associated features that could be used to distinguish healthy individuals from DLBCL patients and distinguish among different primary sites. Through functional enrichment analysis of the differentially 5hmC-enriched genes, almost all DLBCL patients were enriched in tumor-related pathways, and DLBCL patients at different primary sites had unique characteristics. Moreover, 5hmC-based biomarkers can also highly reflect clinical features.

Conclusions

Collectively, we revealed the primary site differential 5hmC regions of DLBCL at different primary sites. This new strategy may help develop minimally invasive and effective methods to diagnose and determine the primary sites of DLBCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01344-1.

Epigenetic tumor heterogeneity in the era of single-cell profiling with nanopore sequencing

Nanopore sequencing has brought the technology to the next generation in the science of sequencing. This is achieved through research advancing on: pore efficiency, creating mechanisms to control DNA translocation, enhancing signal-to-noise ratio, and expanding to long-read ranges. Heterogeneity regarding epigenetics would be broad as mutations in the epigenome are sensitive to cause new challenges in cancer research. Epigenetic enzymes which catalyze DNA methylation and histone modification are dysregulated in cancer cells and cause numerous heterogeneous clones to evolve. Detection of this heterogeneity in these clones plays an indispensable role in the treatment of various cancer types. With single-cell profiling, the nanopore sequencing technology could provide a simple sequence at long reads and is expected to be used soon at the bedside or doctor's office. Here, we review the advancements of nanopore sequencing and its use in the detection of epigenetic heterogeneity in cancer.

5mC and H3K9me3 of TRAF3IP2 promoter region accelerates the progression of translocation renal cell carcinoma

Background

In our previous study, we found that lncRNA TRAF3IP2 antisense RNA 1 (TRAF3IP2-AS1) could play a critical role in the progression of NONO-TFE3 translocation renal cell carcinoma (NONO-TFE3 tRCC). However, the function of TRAF3IP2 (TRAF3 interacting protein 2), encoded by the complementary strand of TRAF3IP2-AS1, remains poorly understood in NONO-TFE3 tRCC.

Methods

Immunohistochemistry, western blot, and qRT-PCR were undertaken to study the expression and clinical significance of TRAF3IP2 in Xp11.2 tRCC tissues and cells. The functions of TRAF3IP2 in tRCC were investigated by proliferation analysis, EdU staining, colony and sphere formation assay, Transwell assay, and apoptosis analysis. The regulatory mechanisms among TRAF3IP2, NOTCH1, and TRAF3IP2-AS1 were investigated by luciferase assay, RNA immunoprecipitation, western blot, methylated DNA Immunoprecipitation, and CRISPR/dCas9-based system.

Results

The results showed that TRAF3IP2 was highly expressed in NONO-TFE3 tRCC tissues and cells, and the silence of TRAF3IP2 inhibited the proliferation, migration, and invasion of UOK109 cells which were derived from cancer tissue of patient with NONO-TFE3 tRCC. Mechanistic studies revealed that TRAF3IP2 functioned as a co-activator of NOTCH1 to activate the NOTCH1 pathway. Meanwhile, HNRNPK, DNMT1 and SETDB1 could be recruited by TRAF3IP2-AS1 to the promoter region of TRAF3IP2, which mediated 5-hydroxymethylcytosine (5mC) on DNA and trimethylated lysine 9 of histone H3 (H3K9me3) at transcriptional level to repress the expression of TRAF3IP2.

Conclusions

TRAF3IP2 functions as an oncogene in NONO-TFE3 tRCC progression and might serve as a novel target for NONO-TFE3 tRCC therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40364-022-00402-3.

CircASPH Promotes Hepatocellular Carcinoma Progression Through Methylation and Expression of HAO2

CircRNAs have been reported to be related to hepatocellular carcinoma (HCC) development. Limited studies have revealed the expression profile of circRNAs in tumor and para-tumor normal samples in HCC patients. We found that circASPH was significantly increased in HCC tumor samples and that the level of circASPH was closely related to the overall survival of HCC patients. Mechanistically, circASPH could regulate the methylation of the promoter and expression of hydrocyanic oxidase 2 (HAO2) to promote HCC progression by acting as a sponge for miR-370-3p, and miR-370-3p could target DNMT3b and increase the 5mC level. In summary, our study determined that circASPH could regulate the methylation and expression of HAO2 and it could be considered an important epigenetic regulator in HCC progression.

Mechanisms that regulate the activities of TET proteins

The ten-eleven translocation (TET) family of dioxygenases consists of three members, TET1, TET2, and TET3. All three TET enzymes have Fe⁺² and α-ketoglutarate (α-KG)-dependent dioxygenase activities, catalyzing the 1st step of DNA demethylation by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), and further oxidize 5hmC to 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC). Gene knockout studies demonstrated that all three TET proteins are involved in the regulation of fetal organ generation during embryonic development and normal tissue generation postnatally. TET proteins play such roles by regulating the expression of key differentiation and fate-determining genes via (1) enzymatic activity-dependent DNA methylation of the promoters and enhancers of target genes; and (2) enzymatic activity-independent regulation of histone modification. Interacting partner proteins and post-translational regulatory mechanisms regulate the activities of TET proteins. Mutations and dysregulation of TET proteins are involved in the pathogenesis of human diseases, specifically cancers. Here, we summarize the research on the interaction partners and post-translational modifications of TET proteins. We also discuss the molecular mechanisms by which these partner proteins and modifications regulate TET functioning and target gene expression. Such information will help in the design of medications useful for targeted therapy of TET-mutant-related diseases.

TET2-BCLAF1 transcription repression complex epigenetically regulates the expression of colorectal cancer gene Ascl2 via methylation of its promoter

Ascl2 has been shown to be involved in tumorigenesis in colorectal cancer (CRC), although its epigenetic regulatory mechanism is largely unknown. Here, we found that methylation of the Ascl2 promoter (bp -1670 ∼ -1139) was significantly increased compared to the other regions of the Ascl2 locus in CRC cells and was associated with elevated Ascl2 mRNA expression. Furthermore, we found that promoter methylation was predictive of CRC patient survival after analyzing DNA methylation data, RNA-Seq data, and clinical data of 410 CRC patient samples from the MethHC database, the MEXPRESS database, and the Cbioportal website. Using the established TET methylcytosine dioxygenase 2 (TET2) knockdown and ectopic TET2 catalytic domain–expression cell models, we performed glucosylated hydroxymethyl–sensitive quatitative PCR (qPCR), real-time PCR, and Western blot assays to further confirm that hypermethylation of the Ascl2 promoter, and elevated Ascl2 expression in CRC cells was partly due to the decreased expression of TET2. Furthermore, BCLAF1 was identified as a TET2 interactor in CRC cells by LC-MS/MS, coimmunoprecipitation, immunofluorescence colocalization, and proximity ligation assays. Subsequently, we found the TET2–BCLAF1 complex bound to multiple elements around CCGG sites at the Ascl2 promoter and further restrained its hypermethylation by inducing its hydroxymethylation using chromatin immunoprecipitation-qPCR and glucosylated hydroxymethyl-qPCR assays. Finally, we demonstrate that TET2-modulated Ascl2-targeted stem gene expression in CRC cells was independent of Wnt signaling. Taken together, our data suggest an additional option for inhibiting Ascl2 expression in CRC cells through TET2–BCLAF1–mediated promoter methylation, Ascl2-dependent self-renewal of CRC progenitor cells, and TET2–BCLAF1–related CRC progression.

Value of 5-Hydroxymethylcytosine in HBV-Carrying High-Risk Hepatocellular Carcinoma Population: An Evaluation Based on Differential Analysis

Objective. To clarify the application value of 5-hydroxymethylcytosine (5hmC) in evaluating the progression of chronic hepatitis B (CHB) to hepatocellular carcinoma (HCC) based on difference analysis. Methods. A total of 180 patients were enrolled. Among them, 84 patients with chronic hepatitis B virus (HBV) infection while no progression to hepatocellular carcinoma (HCC) were included in the control group (CG), and 96 patients with HCC developed from HBV infection were included in the research group (RG). Two-thirds of the samples were used in the training set and 1/3 samples in the validation set to detect the level of 5hmC in both groups based on the modified nano-hmC-Seal technique. The expression levels of 5hmC-related genes TET2 and TET3 were quantified by qPCR, and the correlation between TET3 and 5hmC was analyzed by Pearson’s correlation coefficients. Receiver operating characteristic (ROC) curves were drawn to evaluate the application value of the TET3-based 5hmC prediction model in the early diagnosis of HCC. Results. (i) The expression of 5hmC in RG was lower than that in CG, no matter in the training set or the validation set. (ii) 5hmC was significantly enriched in the region between the transcription initiation site and the transcription end site but was depleted in the flanking region. (iii) 5hmC-related genes TET2 and TET3 were significantly downregulated in HCC patients, whether in the training set or the validation set. (iv) In both the training and validation sets, TET3 showed a positive association with 5hmC. (v) ROC analysis results showed that the 5hmC prediction model could be used to predict the progression of CHB to HCC (training set: $\text{AUC}=0.81$ , 0.729-0.893; validation set: $\text{AUC}=0.84$ , 0.739-0.936). Conclusions. TET3 expression based on 5hmC sequencing is a landmark molecule for evaluating the progression of HCC in CHB patients, which is worthy of further study and promotion.

Rare and misincorporated DNA N6-methyladenine is a hallmark of cytotoxic stresses for selectively stimulating the stemness and proliferation of glioblastoma cells

The entity of DNA N6-methyladenine (6mA) in mammals remains elusive and subsequently its roles in diseases are poorly understood. Here we exploited a bacterial DNA contamination-free and ultrasensitive UHPLC-MS/MS assay to reassess DNA 6mA in human glioblastomas and unveiled that DNA 6mA (~0.08 ppm) is extremely rare. By the use of two independent heavy stable isotope-labeling strategies, we further prove that the observed 6mA is solely generated by DNA polymerase-mediated misinocorporation. In vitro experiments point toward that the generation of misincorporated DNA 6mA is associated with the cellular stresses-caused release of RNA N6-methyladenine (m6A) nucleoside, which is profoundly inhibited by hypoxia milieu. Consistently, compared with normal brain tissues, DNA 6mA decreases in hypoxic human gliomas. Our data also strongly support that rare DNA 6mA rather than relatively abundant DNA 5-methylcytosine and 5-hydroxymethylcytosine is a hallmark of poor prognosis of IDH1/2 mutation-absent glioblastoma patients, reflecting the incidence of cytotoxic stresses and subsequent release of m6A nucleoside. The released m6A nucleoside may selectively preserve a subset of the glioblastoma cells and stimulate their stemness and proliferation. Noteworthily, demethylation-inhibiting IDH1 mutation increases the DNA 6mA content in human gliomas, but the depletion of the demethylase candidate ALKBH1 fails to do so, together suggesting the presence of other unknown 6mA demethylase for erasing misincorporated DNA 6mA. This is the first report on the identification of the misincorporated 6mA together with its origin and roles in diseases.

Metformin Regulates TET2 Expression to Inhibit Endometrial Carcinoma Proliferation: A New Mechanism

Objectives

To investigate the relationship between TET2 expression and endometrial cancer’s clinicopathological features and prognosis, and the effect of metformin on TET2 and 5hmC levels in endometrial cancer cells.

Methods

The clinical significance of TET2 expression in endometrial carcinoma was analyzed from TCGA public database. Eighty-eight patients with endometrial cancer and 20 patients with normal proliferative endometrium were enrolled in this study. TET2 and 5hmC were respectively detected by Immunohistochemistry and ELISA in endometrial tissues. Kaplan-Meier and Cox proportional hazard regression models were used to analyze relationships between TET2 and 5hmC and the overall survival of EC patients. Endometrial cell proliferation was assessed after TET2 gene knockdown. Western blotting and real-time PCR were used to detect the effect of metformin on TET2 expression and to explore whether AMPK is involved in metformin-mediated TET2 regulation.

Results

The clinical significance of expression of TET2 in endometrial cancer from TCGA public database confirmed that TET2 expression was significantly down-regulated in cancer samples and TET2 expression was also significantly different among different histopathological samples and TET2 is down-regulated in advanced, high-grade, and relapsed endometrial carcinoma tissues(P<0.05). Immunohistochemical analysis showed that TET2 and 5hmC levels were significantly lower in endometrial adenocarcinoma(P<0.05). TET2 expression was correlated with the degree of EC differentiation (P < 0.05). 5hmC levels were associated with clinical stage, differentiation, the depth of myometrial invasion, and lymph node metastasis (P < 0.05). The mean survival time of patients with negative staining for TET2 and 5hmC was shorter than that of patients with positive staining for both markers (P<0.05). Multivariate Cox regression analysis showed that TET2 expression was an independent risk factor for prognosis in patients with endometrial adenocarcinoma (HR = 14.520, 95% CI was 1.From 060 to 198.843, P = 0.045). siRNA-mediated TET2 knockdown increased the proliferation of EC cells. Metformin increased the levels of TET2 and 5hmC in EC cells. AMPK was involved in the regulation of TET2 by metformin.

Conclusions

TET2 may play an important role in EC development and may be a prognostic marker. Moreover, TET2 may be involved in a novel mechanism by which metformin inhibits EC cell proliferation.

A fast and label-free detection of hydroxymethylated DNA using a nozzle-jet printed AuNPs@Ti3C2 MXene-based electrochemical sensor

5-hydroxymethylcytosine (5hmC) is a key epigenetic mark in the mammalian genome that has been proposed as a promising cancer biomarker with diagnostic and prognostic potentials. A new type of two-dimensional (2D) material called MXene includes transition metal carbides and nitrides and possesses unique physico-chemical properties suitable for diverse applications, including electrochemical sensors. Here, we report a new nozzle-jet printed electrochemical sensor using gold nanoparticles (AuNPs)@Ti₃C₂ MXene nanocomposite for the real-time and label-free detection of 5hmC in the genome. We utilized Ti₃C₂ MXene as a platform to immobilize AuNPs, which have been shown to exhibit different affinity interactions toward 5-methylcytosine (5 mC) and 5hmC, and thus produce distinct electrochemical responses. To fabricate the electrode, a highly conductive and adhesive silver ink was prepared to generate a silver line onto polyethylene terephthalate (PET) substrate using nozzle-jet printing, followed by deposition of AuNPs@Ti₃C₂ MXene ink at one end via dropcasting. Analyses of morphology and chemical composition showed that all steps of the sensor fabrication were successful. The fabricated sensor coupled with cyclic voltammetry showed excellent performance in distinguishing 5 mC- or 5hmC-enriched cellular genomic DNAs. As a proof-of-concept investigation, we confirmed that our sensor readily and consistently detected 5hmC diminution in multiple tumors, compared to the paired normal tissues. Thus, our simple and cost-effective sensing strategy using printable AuNPs@Ti₃C₂ MXene ink holds promise for a wide range of practical applications in epigenetic studies as well as clinical settings.

Screening of key methylation-driven genes CDO1 in breast cancer based on WGCNA

BACKGROUND

With the rapid development of genomics and molecular biology, not only have biochemical indicators been used as tumour markers, but many new molecular markers have emerged. Epigenetic abnormalities are a new type of molecular marker, and DNA methylation is an important part of epigenetics.

OBJECTIVE

This study used weighted gene coexpression network analysis (WGCNA) to analyse key methylation-driven genes in breast cancer.

METHODS

The RNA-seq transcriptome data, DNA methylation data, and clinical information data of breast cancer patients were downloaded from The Cancer Genome Atlas (TCGA) database, and the MethylMix R package was used to screen methylation-driven genes in breast cancer. The ClusterProfiler package and enrichplot package in R software were used to further analyse the function and signalling pathway of methylation-driven genes. Through univariate and multivariate Cox regression analyses, methylation-driver genes related to prognostic were obtained, a prognostic model was constructed and prognostic characteristics were analysed.

RESULTS

The 17 methylation-driven genes related to prognosis were obtained by the WGCNA method in breast cancer, and the prognostic significance of these methylation-driven genes was determined by transcriptome and methylation combined survival analysis. Analysis of functions and signalling pathways showed that these genes were mainly enriched in biological processes and signalling pathway. Through univariate and multivariate Cox regression analyses, a prognostic model of 5 methylation-driven genes was constructed.

CONCLUSIONS

The AUC of the receiver operating characteristic (ROC) curve of this model was 0.784, showing that the model had a good prediction effect. Based on WGCNA screening, it was found that only CDO1 was the key methylation-driven gene for prognosis in breast cancer, indicating that CDO1 may be an important indicator of the prognosis of breast cancer patients.

Spatial Multiomics Analysis Reveals Only Minor Genetic and Epigenetic Changes in Human Liver Cancer Stem-Like Cells Compared With Other Tumor Parenchymal Cells

Cancer stem cells (CSCs) usually account for a very small tumor cell population but play pivotal roles in human cancer development and recurrence. A fundamental question in cancer biology is what genetic and epigenetic changes occur in CSCs. Here we show that the in-situ global levels of DNA cytosine modifications, including 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC), are similar between liver cancer stem-like (LCSL) cells and paratumor liver cells of liver cancer patients. We then developed a robust method combining immunohistochemistry, laser capture microdissection and genome sequencing with ultra-low-input cells (CIL-seq) to study the detailed genetic and DNA methylation changes in human LCSL cells. We first used clinical samples of mixed hepatocellular carcinoma-cholangiocarcinoma (HCC-CCA) with stem cell features to investigate human LCSL cells. The CIL-seq analysis of HCC-CCA and HCC patients showed that LCSL cells had strong spatial genetic and epigenetic heterogeneity. More interestingly, although the LCSL cells had some potential key changes in their genome, they had substantially fewer somatic single nucleotide variants (SNVs), copy number alterations (CNAs) and differentially methylated regions than other tumor parenchymal cells. The cluster analysis of SNVs, CNAs, DNA methylation patterns and spatial transcriptomes all clearly showed that the LCSL cells were clustered with the paratumor liver cells. Thus, spatial multiomics analysis showed that LCSL cells had only minor genetic and epigenetic changes compared with other tumor parenchymal cells. Targeting key changes in CSCs, not just changes in bulk tumor cells, should be more effective for human cancer therapy.

Evaluation of Epigenetic Age Based on DNA Methylation Analysis of Several CpG Sites in Ukrainian Population

Epigenetic clocks are the models, which use CpG methylation levels for the age prediction of an organism. Although there were several epigenetic clocks developed there is a demand for development and evaluation of the relatively accurate and sensitive epigenetic clocks that can be used for routine research purposes. In this study, we evaluated two epigenetic clock models based on the 4 CpG sites and 2 CpG sites in the human genome using the pyrosequencing method for their methylation level estimation. The study sample included 153 people from the Ukrainian population with the age from 0 to 101. Both models showed a high correlation with the chronological age in our study sample (R² = 0.85 for the 2 CpG model and R² = 0.92 for the 4 CpG model). We also estimated the accuracy metrics of the age prediction in our study sample. For the age group from 18 to 80 MAD was 5.1 years for the 2 CpG model and 4.1 years for the 4 CpG model. In this regard, we can conclude, that the models evaluated in the study have good age predictive accuracy, and can be used for the epigenetic age evaluation due to the relative simplicity and time-effectiveness.

Deoxyribonucleic Acid 5-Hydroxymethylation in Cell-Free Deoxyribonucleic Acid, a Novel Cancer Biomarker in the Era of Precision Medicine

Aberrant methylation has been regarded as a hallmark of cancer. 5-hydroxymethylcytosine (5hmC) is recently identified as the ten-eleven translocase (ten-eleven translocase)-mediated oxidized form of 5-methylcytosine, which plays a substantial role in DNA demethylation. Cell-free DNA has been introduced as a promising tool in the liquid biopsy of cancer. There are increasing evidence indicating that 5hmC in cell-free DNA play an active role during carcinogenesis. However, it remains unclear whether 5hmC could surpass classical markers in cancer detection, treatment, and prognosis. Here, we systematically reviewed the recent advances in the clinic and basic research of DNA 5-hydroxymethylation in cancer, especially in cell-free DNA. We further discuss the mechanisms underlying aberrant 5hmC patterns and carcinogenesis. Synergistically, 5-hydroxymethylation may act as a promising biomarker, unleashing great potential in early cancer detection, prognosis, and therapeutic strategies in precision oncology.

IL-1β-Induced Elevation of Solute Carrier Family 7 Member 11 Promotes Hepatocellular Carcinoma Metastasis Through Up-regulating Programmed Death Ligand 1 and Colony-Stimulating Factor 1

BACKGROUND AND AIMS

Because of a paucity of effective treatment options, metastasis is still a major cause for HCC-associated mortality. The molecular mechanism of inflammation-induced HCC metastasis is open for study. Here, we characterized the function of solute carrier family 7 member 11 (SLC7A11) in inflammation-related HCC metastasis and probed therapy strategies for this subpopulation of patients.

APPROACH AND RESULTS

Elevated expression of SLC7A11 was positively correlated with poor tumor differentiation, and higher tumor-nodule-metastasis stage, and indicated poor prognosis in human HCC. SLC7A11 increased HIF1α expression through reducing α-ketoglutarate (αKG) level by exporting glutamate. SLC7A11 up-regulated programmed death ligand 1 (PD-L1) and colony-stimulating factor 1 (CSF1) expression through αKG-HIF1α cascade. SLC7A11 overexpression in HCC cells promoted intratumoral tumor-associated macrophage (TAM) and myeloid-derived suppressor cell (MDSC) infiltration through the CSF1/colony-stimulating factor 1 receptor (CSF1R) axis, whereas knockdown of CSF1 attenuated SLC7A11-mediated intratumoral TAM and MDSC infiltration and HCC metastasis. Depletion of either TAMs or MDSCs decreased SLC7A11-mediated HCC metastasis. Furthermore, the combination of CSF1R inhibitor BZL945 and anti-PD-L1 antibody blocked SLC7A11-induced HCC metastasis. In addition, IL-1β up-regulated SLC7A11 expression through the interleukin-1 receptor type 1 (IL-1R1)/extracellular signal-regulated kinase/specificity protein 1 pathway. SLC7A11 knockdown impaired IL-1β-promoted HCC metastasis. Anakinra, an IL-1R1 antagonist, reversed IL-1β-promoted HCC metastasis. In human HCC tissues, SLC7A11 expression was positively associated with HIF1α, PD-L1, and CSF1 expression and intratumoral TAM and MDSC infiltration.

CONCLUSIONS

IL-1β-induced SLC7A11 overexpression up-regulated PD-L1 and CSF1 through the αKG/HIF1α axis, which promoted TAM and MDSC infiltration. Interruption of this oncogenic loop may provide a promising therapy strategy for the inhibition of SLC7A11-mediated HCC metastasis.

Quantification of Epigenetic DNA Modifications in the Subchromatin Structure Matrix Attachment Regions by Stable Isotope Dilution UHPLC-MS/MS Analysis

To date, subchromatin structure-based quantification of epigenetic DNA modifications is limited. Matrix attachment regions (MARs), an important subchromatin structure, contain DNA elements that specifically bind chromatin to the nuclear matrix in eukaryotes and are involved in a number of diseases. Here, we exploited a high-salt extraction-based subchromatin fractionation approach for the isolation of MAR DNA and other fractions and further developed heavy stable isotope-diluted ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the specific quantification of epigenetic DNA modifications in the subchromatin structures. By this approach, we showed for the first time that the content of a DNA demethylation intermediate, 5-hydroxymethylcytosine (5hmdC), in MARs decreased significantly in four tested cell lines compared to the contents in genomic DNA. In particular, the content of DNA 5hmdC in the MARs of 293T cell lines decreased the most at approximately 41.09%. Together, our findings implicate that MAR DNA is less sensitive than genomic DNA to DNA demethylation.

Rapid and Label-Free Detection of 5-Hydroxymethylcytosine in Genomic DNA Using an Au/ZnO Nanorods Hybrid Nanostructure-Based Electrochemical Sensor

Ten-eleven-translocation (TET) proteins modify DNA methylation by oxidizing 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). Loss of 5hmC, a widely accepted epigenetic hallmark of cancers, is proposed as a biomarker for early cancer diagnosis and prognosis. Thus, precise quantification of 5hmC holds great potential for diverse clinical applications. DNAs containing 5mC or 5hmC display different adsorption affinity toward the gold surface, thus producing different electrochemical responses. Here a novel, label-free electrochemical sensor based on gold nanoparticles (Au NPs)/zinc oxide nanorods (ZnO NRs) nanostructure for the facile and real-time detection of 5hmC-enriched DNAs is reported. The hybrid structure is fabricated by the vertical hydrothermal growth of ZnO NRs onto indium tin oxide glass substrate, followed by the decoration of ZnO NRs with Au NPs via sputtering. Successful fabrication is confirmed by analyzing the morphology and chemical composition of the sensor. By coupling the fabricated sensor with cyclic voltammetry, its functionality in distinguishing genomic DNAs containing different levels of 5hmC is validated. Notably, the sensor device successfully and consistently detects 5hmC loss in primary hepatocellular carcinoma, compared to the normal tissues. Thus, the novel sensing strategy to assess DNA hydroxymethylation will likely find broad applications in early cancer diagnosis and prognosis evaluation.

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.

Mechanisms of DNA Methylation in Virus-Host Interaction in Hepatitis B Infection: Pathogenesis and Oncogenetic Properties

Hepatitis B virus (HBV), the well-studied oncovirus that contributes to the majority of hepatocellular carcinomas (HCC) worldwide, can cause a severe inflammatory microenvironment leading to genetic and epigenetic changes in hepatocyte clones. HBV replication contributes to the regulation of DNA methyltransferase gene expression, particularly by X protein (HBx), and subsequent methylation changes may lead to abnormal transcription activation of adjacent genes and genomic instability. Undoubtedly, the altered expression of these genes has been known to cause diverse aspects of infected hepatocytes, including apoptosis, proliferation, reactive oxygen species (ROS) accumulation, and immune responses. Additionally, pollutant-induced DNA methylation changes and aberrant methylation of imprinted genes in hepatocytes also complicate the process of tumorigenesis. Meanwhile, hepatocytes also contribute to epigenetic modification of the viral genome to affect HBV replication or viral protein production. Meanwhile, methylation levels of HBV integrants and surrounding host regions also play crucial roles in their ability to produce viral proteins in affected hepatocytes. Both host and viral changes can provide novel insights into tumorigenesis, individualized responses to therapeutic intervention, disease progress, and early diagnosis. As such, DNA methylation-mediated epigenetic silencing of cancer-related genes and viral replication is a compelling therapeutic goal to reduce morbidity and mortality from liver cancer caused by chronic HBV infection. In this review, we summarize the most recent research on aberrant DNA methylation associated with HBV infection, which is involved in HCC development, and provide an outlook on the future direction of the research.

RNA N 6-Methyladenosine in Cancer Metastasis: Roles, Mechanisms, and Applications

Cancer metastasis is a symptom of adverse prognosis, a prime origin of therapy failure, and a lethal challenge for cancer patients. N⁶-methyladenosine (m⁶A), the most prevailing modification in messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs) of higher eukaryotes, has attracted increasing attention. Growing studies have verified the pivotal roles of m⁶A methylation in controlling mRNAs and ncRNAs in diverse physiological processes. Remarkably, recent findings have showed that aberrant methylation of m⁶A-related RNAs could influence cancer metastasis. In this review, we illuminate how m⁶A modifiers act on mRNAs and ncRNAs and modulate metastasis in several cancers, and put forward the clinical application prospects of m⁶A methylation.

Loss of Thymine DNA Glycosylase Causes Dysregulation of Bile Acid Homeostasis and Hepatocellular Carcinoma

Thymine DNA glycosylase (TDG) is a nuclear receptor coactivator that plays an essential role in the maintenance of epigenetic stability in cells. Here, we demonstrate that the conditional deletion of TDG in adult mice results in a male-predominant onset of hepatocellular carcinoma (HCC). TDG loss leads to a prediabetic state, as well as bile acid (BA) accumulation in the liver and serum of male mice. Consistent with these data, TDG deletion led to dysregulation of the farnesoid X receptor (FXR) and small heterodimer partner (SHP) regulatory cascade in the liver. FXR and SHP are tumor suppressors of HCC and play an essential role in BA and glucose homeostasis. These results indicate that TDG functions as a tumor suppressor of HCC by regulating a transcriptional program that protects against the development of glucose intolerance and BA accumulation in the liver.

Host Epigenetic Alterations and Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most frequent primary malignancy of the liver and a leading cause of cancer-related deaths worldwide. Although much progress has been made in HCC drug development in recent years, treatment options remain limited. The major cause of HCC is chronic hepatitis B virus (HBV) infection. Despite the existence of a vaccine, more than 250 million individuals are chronically infected by HBV. Current antiviral therapies can repress viral replication but to date there is no cure for chronic hepatitis B. Of note, inhibition of viral replication reduces but does not eliminate the risk of HCC development. HBV contributes to liver carcinogenesis by direct and indirect effects. This review summarizes the current knowledge of HBV-induced host epigenetic alterations and their association with HCC, with an emphasis on the interactions between HBV proteins and the host cell epigenetic machinery leading to modulation of gene expression.

NAD+ Metabolism Maintains Inducible PD-L1 Expression to Drive Tumor Immune Evasion

NAD⁺ metabolism is implicated in aging and cancer. However, its role in immune checkpoint regulation and immune evasion remains unclear. Here, we find nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD⁺ biogenesis, drives interferon γ (IFNγ)-induced PD-L1 expression in multiple types of tumors and governs tumor immune evasion in a CD8⁺ T cell-dependent manner. Mechanistically, NAD⁺ metabolism maintains activity and expression of methylcytosine dioxygenase Tet1 via α-ketoglutarate (α-KG). IFNγ-activated Stat1 facilitates Tet1 binding to Irf1 to regulate Irf1 demethylation, leading to downstream PD-L1 expression on tumors. Importantly, high NAMPT-expressing tumors are more sensitive to anti-PD-L1 treatment and NAD⁺ augmentation enhances the efficacy of anti-PD-L1 antibody in immunotherapy-resistant tumors. Collectively, these data delineate an NAD⁺ metabolism-dependent epigenetic mechanism contributing to tumor immune evasion, and NAD⁺ replenishment combined with PD-(L)1 antibody provides a promising therapeutic strategy for immunotherapy-resistant tumors.

Detection of N6-Methyladenine in Eukaryotes

DNA N⁶-methyladenine (6mA) is a chemical modification at the N⁶-positon of adenine. In the last decades, 6mA had been found in genome from numerous prokaryotic species, but only existed in a few lower eukaryotes. In prokaryotes, 6mA plays an important role in restriction-modification, DNA replication, and DNA mismatch repair. Because of the too low abundance of 6mA, it was long-stalled whether 6mA existed in multicellular eukaryotes and playing any functions, particularly in mammals. In recent years, partially benefitting from the advances in analytical methods, 6mA was found in the genomes from Drosophila melanogaster, Chlamydomonas algae, Caenorhabditis elegans, zebrafish, Xenopus laevis and mouse embryonic stem cells and even in the human genome. The 6mA was dynamic changed in early embryonic development of fly and zebrafish and much more enriched in gene body of transposons in fly, repetitive regions in zebrafish, around the transcription start sites in Chlamydomonas, and widespread distribution in C. elegans, indicating 6mA probably playing different functions in different species. Meanwhile, 6mA methylases and demethylases were found in fly, worm, and Chlamydomonas. In this chapter, we will briefly review the distribution, regulation, and function of 6mA in eukaryotes and focus on the advances of 6mA analysis methods, especially LC-MS/MS, immunoprecipitation, next-generation sequencing, and single-molecule real-time sequencing technology.

Epigenetics in hepatocellular carcinoma development and therapy: The tip of the iceberg

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.

Epigenome-wide DNA methylation profiling of portal vein tumor thrombosis (PVTT) tissues in hepatocellular carcinoma patients

Aberrant methylation is a hallmark of hepatocellular carcinoma and plays an important role in tumor initiation and progression. However, the epigenome-wide methylation patterns of portal vein tumor thrombosis (PVTTs) have not been fully explored. Here, we performed epigenome-wide DNA methylation of adjacent normal tissues (ANTs), paired tumor tissues and paired PVTTs using an Infinium HumanMethylation450 array (n = 11) and conducted the Sequenom EpiTYPER assays to confirm the aberrantly methylated genes. MTS and apoptosis assay were used to assess the synergistic effect of two drugs on the HCC cell lines. We found the mean global methylation levels of HCC tissues and PVTTs were significantly lower than ANTs (P < 0.01). A total of 864 differentially methylated CpG sites annotated in 532 genes were identified between HCC tissues and paired PVTTs (|mean methylation difference|>10%, P < 0.005). The pathway analysis based on hypermethylated genes in PVTT tissues was interestingly enriched in regulation of actin cytoskeleton pathway (P = 4.48E−5). We found 23 genes whose methylation levels were gradually alternated in HCC tissues and PVTTs. Aberrant methylation status of TNFRSF10A, ZC3H3 and SLC9A3R2 were confirmed in a validation cohort (n = 48). The functional experiments demonstrated the combination of decitabine (DAC) and tumor necrosis factor-related apoptosis-inducing ligand (rh-TRAIL) could synergistically suppress the proliferation and induce apoptosis in SK-Hep-1 and Huh7 cell lines. Together, our findings indicated that DNA methylation plays an important role in the PVTT formation through regulating the metastasis-related pathways. The combination of DAC and rh-TRAIL might be a promising treatment strategy for HCC.

Selective Chemical Labeling and Sequencing of 5-Carboxylcytosine in DNA at Single-Base Resolution

5-Carboxylcytosine (5caC) plays a vital role in the dynamics of DNA demethylation, and sequencing of its sites will help us dig out more biological functions of 5caC. Herein, we present a novel chemical method to efficiently label 5caC distinguished from other bases in DNA. Combined with bisulfite sequencing, 5caC sites can be located at single-base resolution, and the efficiency of 5caC labeling is 92% based on the Sanger sequencing data. Furthermore, dot blot assays have confirmed that 5caC-containing DNA isolated from HeLa cells was successfully labeled using our method. We expect that our strategy can be further applied to selectively tagging other carboxyl-modified bases and mapping their sites in RNA.

DNA methylation in Hepatoblastoma-a literature review

Hepatoblastoma (HB) is the most common malignant liver tumor in children. Abnormal activation of the Wnt/β-catenin signaling pathway plays an important role in the formation and development of HB. Genes in HB show a global hypomethylation change, accompanied by hypermethylation of specific tumor suppressor genes (TSGs). This article reviews the hypermethylation changes in several TSGs, such as RASSF1A, SOCS1, APC, HHIP, and P16, and analyzes the pathways and mechanisms of TSGs regulating gene expression. The role of the methylation-regulating enzymes DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) family members enzymes in the methylation changes of HB was analyzed, and it was speculated that the occurrence of HB is partly due to the obstruction of liver differentiation in the early stage of differentiation. The origin cells may be incompletely differentiated hepatocytes remaining in the liver of children after birth. Therefore, further studying the role of methylation regulating enzymes in methylation changes in HB is a promising future research direction.

Integrated epigenetic biomarkers in circulating cell-free DNA as a robust classifier for pancreatic cancer

BACKGROUND

The high lethal rate of pancreatic cancer is partly due to a lack of efficient biomarkers for screening and early diagnosis. We attempted to develop effective and noninvasive methods using 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) markers from circulating cell-free DNA (cfDNA) for the detection of pancreatic ductal adenocarcinoma (PDAC).

RESULTS

A 24-feature 5mC model that can accurately discriminate PDAC from healthy controls (area under the curve (AUC) = 0.977, sensitivity = 0.824, specificity = 1) and a 5hmC prediction model with 27 features demonstrated excellent detection power in two distinct validation sets (AUC = 0.992 and 0.960, sensitivity = 0.786 and 0.857, specificity = 1 and 0.993). The 51-feature model combining 5mC and 5hmC markers outperformed both of the individual models, with an AUC of 0.997 (sensitivity = 0.938, specificity = 0.955) and particularly an improvement in the prediction sensitivity of PDAC. In addition, the weighted diagnosis score (wd-score) calculated with the 5hmC model can distinguish stage I patients from stage II-IV patients.

CONCLUSIONS

Both 5mC and 5hmC biomarkers in cfDNA are effective in PDAC detection, and the 5mC-5hmC integrated model significantly improve the detection sensitivity.

A novel strategy for the diagnosis, prognosis, treatment, and chemoresistance of hepatocellular carcinoma: DNA methylation

The cancer mortality rate of hepatocellular carcinoma (HCC) is the second highest in the world and the therapeutic options are limited. The incidence of this deadly cancer is rising at an alarming rate because of the high degree of resistance to chemo- and radiotherapy, lack of proper, and adequate vaccination to hepatitis B, and lack of consciousness and knowledge about the disease itself and the lifestyle of the people. DNA methylation and DNA methylation-induced epigenetic alterations, due to their potential reversibility, open the access to develop novel biomarkers and therapeutics for HCC. The contribution to these epigenetic changes in HCC development still has not been thoroughly summarized. Thus, it is necessary to better understand the new molecular targets of HCC epigenetics in HCC diagnosis, prevention, and treatment. This review elaborates on recent key findings regarding molecular biomarkers for HCC early diagnosis, prognosis, and treatment. Currently emerging epigenetic drugs for the treatment of HCC are summarized. In addition, combining epigenetic drugs with nonepigenetic drugs for HCC treatment is also mentioned. The molecular mechanisms of DNA methylation-mediated HCC resistance are reviewed, providing some insights into the difficulty of treating liver cancer and anticancer drug development.

Protonation-Suppression-Free LC-MS/MS Analysis for Profiling of DNA Cytosine Modifications in Adult Mice

DNA cytosine modifications are important epigenetic marks. To elucidate their roles by a large scale of comparative studies, it is important to quantify the abundance of DNA cytosine modifications accurately. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a golden option. The performance of LC-MS/MS is heavily dependent on the ionization or protonation of target analytes. Initially, we found that two factors, DNA hydrolysate buffer and residual coeluted nucleosides, might greatly suppress the protonation of 5-(hydroxymethyl)-2'-deoxycytidine (5hmdC). Surprisingly, ammonium bicarbonate can eliminate the suppression caused by both factors. Mechanistically, ammonium bicarbonate increases the protonation capacity in the gas phase and facilitates proton transfer to the target nucleosides. Benefiting from these findings, we developed a suppression-free, sensitive, and robust ultrahigh-performance LC-MS/MS assay for massive detection of three DNA cytosine modifications, including 5-methyl-2'-deoxycytidine (5mdC), 5hmdC, and 5-formyl-2'-deoxycytidine (5fdC). In 30 consecutive analyses, the relative standard deviation (RSD) of the 5hmdC and 5fdC peak areas is 2.0% and 3.2%, respectively. In this case, no stable isotope-labeled standard is required for internal calibration. We further performed a comprehensive profiling of DNA cytosine modifications in 26 tissues of age-different C57BL/6N mice. Interestingly, we found that only liver 5hmdC abundance increases with the increasing age of adult mice, suggesting that liver 5hmdC might be a potential indicator of age in adulthood.

Genome-wide 5-hydroxymethylcytosine (5hmC) emerges at early stage of in vitro differentiation of a putative hepatocyte progenitor

A basic question linked to differential patterns of gene expression is how cells reach different fates despite using the same DNA template. Since 5-hydroxymethylcytosine (5hmC) emerged as an intermediate metabolite in active DNA demethylation, there have been increasing efforts to elucidate its function as a stable modification of the genome, including a role in establishing such tissue-specific patterns of expression. Recently we described TET1-mediated enrichment of 5hmC on the promoter region of the master regulator of hepatocyte identity, HNF4A, which precedes differentiation of liver adult progenitor cells in vitro. Here, we studied the genome-wide distribution of 5hmC at early in vitro differentiation of human hepatocyte-like cells. We found a global increase in 5hmC as well as a drop in 5-methylcytosine after one week of in vitro differentiation from bipotent progenitors, at a time when the liver transcript program is already established. 5hmC was overall higher at the bodies of overexpressed genes. Furthermore, by modifying the metabolic environment, an adenosine derivative prevents 5hmC enrichment and impairs the acquisition of hepatic identity markers. These results suggest that 5hmC could be a marker of cell identity, as well as a useful biomarker in conditions associated with cell de-differentiation such as liver malignancies.