The m6A methyltransferase METTL3 promotes bladder cancer progression via AFF4/NF-κB/MYC signaling network

The contribution of YTHDF2 gene rs3738067 A>G to the Wilms tumor susceptibility

YTHDF2 is responsible for maintaining the dynamic N⁶-methyladenosine (m⁶A) modification balance and influences a variety of cancers. We tested whether YTHDF2 gene rs3738067 A>G polymorphism is related to Wilms tumor by genotyping samples of Chinese children (450 cases and 1317 controls). However, the rs3738067 A>G polymorphism showed no statistical significance with Wilms tumor susceptibility. Stratification analysis also revealed that there was no remarkable association of rs3738067 variant AG/GG genotype with Wilms tumor risk in every subgroup (age, gender, and clinical stages). In all, the results indicated YTHDF2 gene rs3738067 A>G polymorphism could not alter Wilms tumor risk significantly.

Stabilization of ERK-Phosphorylated METTL3 by USP5 Increases m6A Methylation

N⁶-methyladenosine (m⁶A) is the most abundant mRNA modification and is installed by the METTL3-METTL14-WTAP methyltransferase complex. Although the importance of m⁶A methylation in mRNA metabolism has been well documented recently, regulation of the m⁶A machinery remains obscure. Through a genome-wide CRISPR screen, we identify the ERK pathway and USP5 as positive regulators of the m⁶A deposition. We find that ERK phosphorylates METTL3 at S43/S50/S525 and WTAP at S306/S341, followed by deubiquitination by USP5, resulting in stabilization of the m⁶A methyltransferase complex. Lack of METTL3/WTAP phosphorylation reduces decay of m⁶A-labeled pluripotent factor transcripts and traps mouse embryonic stem cells in the pluripotent state. The same phosphorylation can also be found in ERK-activated human cancer cells and contribute to tumorigenesis. Our study reveals an unrecognized function of ERK in regulating m⁶A methylation.

Programmable N6-methyladenosine modification of CDCP1 mRNA by RCas9-methyltransferase like 3 conjugates promotes bladder cancer development

Accumulating evidence has revealed significant roles for N6-methyladenosine (m 6 A) modification in the development of various cancers. We previously demonstrated an oncogenic role of m 6 A-modified CUB domain containing protein 1 (CDCP1) in bladder cancer (BC) progression. However, the biological functions and underlying molecular mechanisms of engineered programmable m 6 A modification of CDCP1 mRNA in BC remain obscure. Here, we established a targeted m 6 A RNA methylation system by fusing the catalytic domain of methyltransferase like 3 (METTL3CD) to RCas9 as the RNA-targeting module. The constructed RCas9- METTL3 retained methylation activity and mediated efficient site-specific m 6 A installation in the presence of a cognate single guide RNA and short protospacer adjacent motif-containing ssDNA molecule . Subsequently, targeting m 6 A installation onto the 3′ untranslated region of CDCP1 promoted CDCP1 mRNA translation and facilitated BC development in vitro and in vivo. Our findings demonstrate that the RCas9-METTL3 system mediates efficient sitespecific m 6 A installation on CDCP1 mRNA and promotes BC development. Thus, the RCas9-METTL3 system provides a new tool for studying m 6 A function and a potential strategy for BC epitranscriptome-modulating therapies.

Epigenetic modifications of c-MYC: Role in cancer cell reprogramming, progression and chemoresistance

Both genetic and epigenetic mechanisms intimately regulate cancer development and chemoresistance. Different genetic alterations are observed in multiple genes, and most are irreversible. Aside from genetic alterations, epigenetic alterations play a crucial role in cancer. The reversible nature of epigenetic modifications makes them an attractive target for cancer prevention and therapy. Specific epigenetic alteration is also being investigated as a potential biomarker in multiple cancers. c-MYC is one of the most important transcription factors that are centrally implicated in multiple types of cancer cells reprogramming, proliferation, and chemoresistance. c-MYC shows not only genetic alterations but epigenetic changes in multiple cancers. It has been observed that epigenome aberrations can reversibly alter the expression of c-MYC, both transcriptional and translational levels. Understanding the underlying mechanism of the epigenetic alterations of c-MYC, that has its role in multiple levels of cancer pathogenesis, can give a better understanding of various unresolved questions regarding cancer. Recently, some researchers reported that targeting the epigenetic modifiers of c-MYC can successfully inhibit cancer cell proliferation, sensitize the chemoresistant cells, and increase the patient survival rate. As c-MYC is an important transcription factor, epigenetic therapy might be one of the best alternatives for the conventional therapies that assumes the "one-size-fits-all" role. It can also increase the precision of targeting and enhance the effectiveness of treatments among various cancer subtypes. In this review, we highlighted the role of epigenetically modified c-MYC in cancer cell reprogramming, progression, and chemoresistance. We also summarize the potential therapeutic approaches to target these modifications for the prevention of cancer development and chemoresistant phenotypes.

m6 A methyltransferase METTL3 promotes retinoblastoma progression via PI3K/AKT/mTOR pathway

Retinoblastoma (RB) is a common intraocular malignancy in children. Due to the poor prognosis of RB, it is crucial to search for efficient diagnostic and therapeutic strategies. Studies have shown that methyltransferase-like 3 (METTL3), a major RNA N (6)-adenosine methyltransferase, is closely related to the initiation and development of cancers. Nevertheless, whether METTL3 is associated with RB remains unexplored. Therefore, we investigated the function and mechanisms of METTL3 in the regulation of RB progression. We manipulated METTL3 expression in RB cells. Then, cell proliferation, apoptosis, migration and invasion were analysed. We also analysed the expression of PI3K/AKT/mTOR pathway members. Finally, we incorporated subcutaneous xenograft mouse models into our studies. The results showed that METTL3 is highly expressed in RB patients and RB cells. We found that METTL3 knockdown decreases cell proliferation, migration and invasion of RB cells, while METTL3 overexpression promotes RB progression in vitro and in vivo. Moreover, two downstream members of the PI3K/AKT/mTOR pathway, P70S6K and 4EBP1, were affected by METTL3. Our study revealed that METTL3 promotes the progression of RB through PI3K/AKT/mTOR pathways in vitro and in vivo. Targeting the METTL3/PI3K/AKT/mTOR signalling axis could be a promising therapeutic strategy for the treatment of RB.

METTL3 polymorphisms and Wilms tumor susceptibility in Chinese children: A five-center case-control study

BACKGROUND

Wilms tumor is a common pediatric tumor worldwide. Methyltransferase like 3 (METTL3) is a core gene of the N⁶ -methyladenosine (m⁶ A) modification that widely affects the transcription of tumor-related genes in eukaryotes. METTL3 has been extensively investigated in various tumors but not Wilms tumor.

METHODS

We describe a five-center case-control study with 414 patients and 1199 controls aiming to explore the associations between METTL3 polymorphisms (rs1061026 T>G, rs1061027 C>A, rs1139130 A>G and rs1263801 G>C) and Wilms tumor susceptibility. A TaqMan real-time polymerase chain reaction was performed for genotyping. Odds ratios (ORs) and 95% confidence intervals (CIs) were reported as evaluation indicators to determine any associations.

RESULTS

Referring to the preliminary analysis results, protective genotypes were identified as rs1061026 TG/GG, rs1061027 CA/AA, rs1139130 GG and rs1263801 GC/CC. The children with three protective genotypes were less likely to develop Wilms tumor than children without protective genotypes (adjusted OR = 0.68, 95% CI = 0.46-0.999, p = 0.0496). Similarly, stratified analysis of the subgroup aged > 18 months, carrying 3 or 4 protective genotypes, was a protective factor for Wilms tumor compared to carrying 0-2 protective genotypes (adjusted OR = 0.59 95% CI = 0.39-0.91, p = 0.016). However, we did not observe any other significant results.

CONCLUSIONS

The combined effect of METTL3 polymorphisms reduce Wilms tumor susceptibility in Chinese children. This conclusion requires further verification.

N6-methyladenosine METTL3 promotes cervical cancer tumorigenesis and Warburg effect through YTHDF1/HK2 modification

N6-methyladenosine (m6A) serves as the most common and conserved internal transcriptional modification. However, the roles of m6A on cervical cancer (CC) tumorigenesis are still unclear. Here, results indicated that METTL3 was significantly upregulated in CC tissue and cells, which was closely correlated with the lymph node metastasis and poor prognosis of CC patients. MeRIP-Seq analysis revealed the m6A profiles in CC cells. Functionally, METTL3 promoted the proliferation and Warburg effect (aerobic glycolysis) of CC cells. Mechanistically, METTL3 targeted the 3'-Untranslated Region (3'-UTR) of hexokinase 2 (HK2) mRNA. Moreover, METTL3 recruited YTHDF1, a m6A reader, to enhance HK2 stability. These findings demonstrated that METTL3 enhanced the HK2 stability through YTHDF1-mediated m6A modification, thereby promoting the Warburg effect of CC, which might promote a novel insight for the CC treatment.

ALKBH5 Inhibited Cell Proliferation and Sensitized Bladder Cancer Cells to Cisplatin by m6A-CK2α-Mediated Glycolysis

N6-methyladenosine (m6A) is the most commonly occurring internal RNA modification to be found in eukaryotic mRNA and serves an important role in various physiological events. AlkB homolog 5 RNA demethylase (ALKBH5), an m6A demethylase, belongs to the AlkB family of dioxygenases and has been shown to specifically demethylate m6A in RNA, which is associated with a variety of tumors. However, its function in bladder cancer remains largely unclear. In the present study, we found that the expression of ALKBH5 was downregulated in bladder cancer tissues and cell lines. Low expression of ALKBH5 was correlated with the worse prognosis of bladder cancer patients. Furthermore, functional assays revealed that knockdown of ALKBH5 promoted bladder cancer cell proliferation, migration, invasion, and decreased cisplatin chemosensitivity in the 5637 and T24 bladder cancer cell lines in vivo and in vitro, whereas ALKBH5 overexpression led to the opposite results. Finally, ALKBH5 inhibited the progression and sensitized bladder cancer cells to cisplatin through a casein kinase 2 (CK2)α-mediated glycolysis pathway in an m6A-dependent manner. Taken together, these findings might provide fresh insights into bladder cancer therapy.

Connecting METTL3 and intratumoural CD33+ MDSCs in predicting clinical outcome in cervical cancer

Background

Methyltransferase-like 3 (METTL3) is a member of the m⁶A methyltransferase family and acts as an oncogene in cancers. Recent studies suggest that host innate immunity is regulated by the enzymes controlling m⁶A epitranscriptomic changes. Here, we aim to explore the associations between the levels of METTL3 and CD33⁺ myeloid-derived suppressor cells (MDSCs) in tumour tissues and the survival of patients with cervical cancer (CC).

Methods

Specimens of paraffin embedded tumour from 197 CC patients were collected. The expression levels of METTL3 and CD33 were measured by immunohistochemical (IHC) staining. The clinical associations of the IHC variants were analysed by Pearson’s or Spearman’s chi-square tests. Overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan–Meier method and log-rank test. Hazard ratios (HRs) and independent significance were obtained via Cox proportional hazards models for multivariate analyses. METTL3 in CD33⁺ cells or CC-derived cells was knocked down by METTL3-specific siRNA, and MDSC induction in vitro was performed in a co-culture system in the presence of METTL3-siRNA and METTL3-knockdown-CC-derived cells compared with that of the corresponding controls.

Results

We found that tumour tissues displayed increased levels of METTL3 and CD33⁺ MDSCs compared with tumour-adjacent tissues from the same CC patients. Importantly, METTL3 expression was positively related to the density of CD33⁺ cells in tumour tissues (P = 0.011). We further found that the direct CD33⁺CD11b⁺HLA-DR⁻ MDSC induction and tumour-derived MDSC induction in vitro were decreased in the absence of METTL3. The level of METTL3 in tumour microenvironments was significantly related to advanced tumour stage. The levels of METTL3 and CD33⁺ MDSCs in tumour tissues were notably associated with reduced DFS or OS. Cox model analysis revealed that the level of METTL3 in tumour cells was an independent factor for patient survival, specifically for DFS (HR = 3.157, P = 0.022) and OS (HR = 3.271, P = 0.012), while the CD33⁺ MDSC number was an independent predictor for DFS (HR: 3.958, P = 0.031). Interestingly, in patients with advanced-disease stages (II–IV), METTL3 in tumour cells was an independent factor for DFS (HR = 6.725, P = 0.010) and OS (HR = 5.140, P = 0.021), while CD33⁺ MDSC density was an independent factor for OS (HR = 8.802, P = 0.037).

Conclusion

Our findings suggest that CD33⁺ MDSC expansion is linked to high levels of METTL3 and that METTL3 and CD33⁺ MDSCs are independent prognostic factors in CC.

HBXIP promotes gastric cancer via METTL3-mediated MYC mRNA m6A modification

Gastric cancer (GC) is one of the most common malignancies worldwide with limited treatment options and distinct geographical distribution even in countries such as China. Genetic alterations during its carcinogenesis need urgent elucidation. In this study, we propose an intriguing hypothesis that the hepatitis B X-interacting protein (HBXIP) may function as an oncogene in GC. We harvested 45 GC tissues and matched the paracancerous tissues. The c-myc proto-oncogene (MYC) N6-methyladenosine (m6A) mRNA methylation was detected by m6A RNA immunoprecipitation and dot-blot assays. Expressions of HBXIP, methyltransferase like 3 (METTL3) and MYC were all determined to be upregulated in both GC tissues and cells. Silencing HBXIP led to a decreased expression of METTL3, which inhibited GC cell proliferation, migration and invasion while promoting their apoptosis. Furthermore, METTL3 enhanced MYC m6A methylation and increased MYC translation, which could potentiate the proliferation, migration and invasion of GC cells. Finally, the HBXIP knockdown impeded the tumorigenicity of GC cells in vivo. Based on the findings of this study, we conclude that HBXIP plays an oncogenic role in GC via METTL3-mediated MYC mRNA m6A modification. The study offers a comprehensive understanding of HBXIP as a potential therapeutic target to limit GC progression.

Advances in the role of m6A RNA modification in cancer metabolic reprogramming

N6-methyladenosine (m6A) modification is the most common internal modification of eukaryotic mRNA and is widely involved in many cellular processes, such as RNA transcription, splicing, nuclear transport, degradation, and translation. m6A has been shown to plays important roles in the initiation and progression of various cancers. The altered metabolic programming of cancer cells promotes their cell-autonomous proliferation and survival, leading to an indispensable hallmark of cancers. Accumulating evidence has demonstrated that this epigenetic modification exerts extensive effects on the cancer metabolic network by either directly regulating the expression of metabolic genes or modulating metabolism-associated signaling pathways. In this review, we summarized the regulatory mechanisms and biological functions of m6A and its role in cancer metabolic reprogramming.

N6 -methyladenosine (m6 A) RNA modification in human cancer

N⁶ -methyladenosine (m⁶ A) RNA modification, first discovered in 1974, is the most prevalent, abundant and penetrating messenger RNA (mRNA) modification in eukaryotes. This governs the fate of modified transcripts, regulates RNA metabolism and biological processes, and participates in pathogenesis of numerous human diseases, especially in cancer through the reciprocal regulation of m⁶ A methyltransferases ("writers") and demethylases ("erasers") and the binding proteins decoding m⁶ A methylation ("readers"). Accumulating evidence indicates a complicated regulation network of m⁶ A modification involving multiple m⁶ A-associated regulatory proteins whose biological functions have been further analysed. This review aimed to summarize the current knowledge on the potential significance and molecular mechanisms of m⁶ A RNA modification in the initiation and progression of cancer.

Silencing of methyltransferase-like 3 inhibits oesophageal squamous cell carcinoma

Methyltransferase-like 3 (METTL3) is a methyltransferase responsible for N6-methyladenosine mRNA modifications, which has been demonstrated to serve oncogenic roles in various types of cancer; however, the exact function of METTL3 in oesophageal squamous cell carcinoma (ESCC) has not been determined. The present study aimed to explore the regulatory role of METTL3 in ESCC. In the present study, reverse transcription-quantitative PCR and western blotting were used to examine mRNA and protein expression, CCK-8 assays and flow cytometry were used to determine cellular viability and apoptosis, and wound healing and Transwell assays were conducted to study cellular migration and invasion. The expression levels of METTL3 were significantly higher in ESCC tissues and cell lines compared with adjacent non-tumour tissues and the normal oesophageal epithelial cell line HET-1A, respectively. Increased METTL3 expression was associated with an advanced clinical stage of ESCC and poorer prognosis. Furthermore, the genetic knockdown of METTL3 using small interfering RNA significantly suppressed ESCC growth, invasion and migration in vitro, and induced cellular apoptosis, in addition to reducing the phosphorylation levels of PI3K and AKT. In conclusion, the present study demonstrated that the upregulation of METTL3 promoted ESCC progression, and that inhibition of METTL3 significantly suppressed the malignant phenotypes of ESCC cells, at least in part, by downregulating PI3K/AKT signalling activity. Thus, it is suggested that METTL3 may be a promising therapeutic target for ESCC.

N6-methyladenosine (m6A) RNA modification in cancer stem cells

Cancer stem cells (CSCs), a unique subset of undifferentiated cells with stem cell-like properties, have emerged as driving forces in mediating tumor growth, metastasis, and therapeutic resistance. Recent advances have highlighted that N6-methyladenosine (m6A) RNA modification plays an important role in cancer biology and CSCs. Dynamic m6A decoration has been demonstrated to be involved in CSC generation and maintenance, governing cancer progression and therapeutic resistance. In this review, we provide the first overview of the current knowledge of m6A modification implicated in CSCs and their impact on CSC properties, tumor progression, and responses to treatment. Finally, we also highlight the potential of m6A machinery as novel targets for cancer therapeutics. The involvement of m6A modification in CSCs provides a new direction for exploring cancer pathogenesis and inspires the development of effective strategies to fully eliminate both cancer cells and CSCs.

WTAP Gene Variants Confer Hepatoblastoma Susceptibility: A Seven-Center Case-Control Study

Hepatoblastoma is a rare disease, and its etiology remains to be revealed. Wilms tumor suppressor-1-associated protein (WTAP) plays a critical role in tumorigenesis. However, whether single nucleotide polymorphisms (SNPs) of the WTAP gene predispose to hepatoblastoma risk awaits to be investigated. With the use of the TaqMan assay, we evaluated the genotype frequencies of three WTAP SNPs (rs7766006 G > T, rs9457712 G > A, and rs1853259 A > G) in Chinese children with 313 hepatoblastoma patients and 1,446 controls. Among these three SNPs, only the rs7766006 T allele exhibited a significant association with hepatoblastoma risk (GT versus GG: adjusted odds ratio [OR] = 0.70, 95% confidence interval [CI] = 0.53-0.92, p = 0.009; GT/TT versus GG: adjusted OR = 0.73, 95% CI = 0.57-0.95, p = 0.017). Combined analysis indicated that subjects with two risk genotypes showed significantly higher hepatoblastoma risk, compared to individuals without a risk genotype (adjusted OR = 1.38, 95% CI = 1.02-1.88, p = 0.037). The stratified analysis revealed that the rs1853259 GG genotype, the rs7766006 GT/TT genotype, and two risk genotypes modified hepatoblastoma risk in certain subgroups. The significant results were validated by haplotype analyses and false-positive report probability analyses. Furthermore, the expression quantitative trait locus analysis indicated that rs7766006 T was associated with decreased expression of WTAP mRNA. Collectively, our results suggest that WTAP SNPs may be genetic modifiers for the development of hepatoblastoma.

m6A RNA methylation regulators can contribute to malignant progression and impact the prognosis of bladder cancer

N6-methyladenosine (m6A) is the most common form of messenger RNA (mRNA) modification. An increasing number of studies have proven that m6A RNA methylation regulators are overexpressed in many cancers and participate in the development of cancer through the dynamic regulation of m6A RNA methylation regulators. However, the prognostic role of m6A RNA methylation regulators in bladder cancer (BC) is poorly understood. In the present study, we downloaded the mRNA expression data from The Cancer Genome Atlas (TCGA) database and the corresponding clinical and prognostic information. The relationship between m6A RNA methylation regulators and clinicopathological variables of BC patients was assessed by the Kolmogorov–Smirnov test. The expression of the m6A RNA methylation regulators was differentially associated with different clinicopathological variables of BC patients. The least absolute shrinkage and selection operator (LASSO) Cox regression model was then applied to identify three m6A RNA methylation regulators. The risk signature was constructed as follows: 0.164FTO − (0.081YTHDC1+0.032WTAP). Based on the risk signature, the risk score of each patient was calculated, and the patients were divided into a high-risk group and a low-risk group. The overall survival (OS) rate of the high-risk group was significantly lower than that of the low-risk group. The risk signature was not only an independent prognostic marker for BC patients but also a predictor of clinicopathological variables. In conclusion, m6A RNA methylation regulators can participate in the malignant progression of BC, and a risk signature with three selected m6A RNA methylation regulators may be a promising prognostic biomarker to guide personalized treatment for BC patients.

Genetic variants in N6-methyladenosine are associated with bladder cancer risk in the Chinese population

Recently N⁶-Methyladenosine (m⁶A) has been identified to guide the interaction of RNA-binding protein hnRNP C and their target RNAs, which is termed as m⁶A-switches. We systematically investigated the association between genetic variants in m⁶A-switches and bladder cancer risk. A two-stage case-control study was performed to systematically calculate the association of single nucleotide polymorphisms (SNPs) in 2798 m⁶A-switches with bladder cancer risk in 3,997 subjects. A logistic regression model was used to assess the effects of SNPs on bladder cancer risk. A series of experiments were adopted to explore the role of genetic variants of m⁶A-switches. We identified that rs5746136 (G > A) of SOD2 in m⁶A-switches was significantly associated with the reduced risk of bladder cancer (additive model in discovery stage: OR = 0.80, 95% CI 0.69-0.93, P = 3.6 × 10^-3; validation stage: adjusted OR = 0.88, 95% CI 0.79-0.99, P = 3.0 × 10^-2; combined analysis: adjusted OR = 0.85, 95% CI 0.78-0.93, P = 4.0 × 10^-4). The mRNA level of SOD2 was remarkably lower in bladder cancer tissues than the paired adjacent samples. SNP rs5746136 may affect m⁶A modification and regulate SOD2 expression by guiding the binding of hnRNP C to SOD2, which played a critical tumor suppressor role in bladder cancer cells by promoting cell apoptosis and inhibiting proliferation, migration and invasion. In conclusion, our findings suggest the important role of genetic variants in m⁶A modification. SOD2 polymorphisms may influence the expression of SOD2 via an m⁶A-hnRNP C-dependent mechanism and be promising predictors of bladder cancer risk.

A newly defined risk signature, consisting of three m6A RNA methylation regulators, predicts the prognosis of ovarian cancer

N6-methyladenosine (m⁶A) RNA methylation, involved in cancer initiation and progression, is dynamically regulated by the m⁶A RNA methylation regulators. However, the expression of m⁶A RNA methylation regulators in ovarian cancer and their correlation with prognosis remain elusive. Here, we demonstrated that the 18 central m⁶A RNA methylation regulators were expressed differently between ovarian cancer (OC) and normal tissues. By applying consensus clustering, all ovarian cancer patient cases can be divided into three subgroups (cluster1/2/3) based on overall expression levels of all 18 m⁶A RNA methylation regulators. We systematically analyzed the prognostic value of transcription levels of 18 m⁶A RNA methylation regulators in ovarian cancer and found that insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), vir like m⁶A methyltransferase associated (VIRMA), and zinc finger CCCH-type containing 13 (ZC3H13) yield the highest scores for predicting the prognosis of ovarian cancer. Accordingly, we derived a risk signature consisting of transcription levels of these three selected m⁶A RNA methylation regulators as an independent prognostic marker for OC and validated our findings with data derived from a different ovarian cancer cohort. Moreover, by the Gene Set Enrichment Analysis (GSEA), we demonstrated that the three selected regulators were all correlated with pathways in cancer and WNT signaling pathways. In conclusion, m⁶A RNA methylation regulators are vital participants in ovarian cancer pathology; and IGF2BP1, VIRMA, and ZC3H13 mRNA levels are valuable factors for prognosis prediction and treatment strategy development.

Expression Pattern and Prognostic Value of Key Regulators for m6A RNA Modification in Hepatocellular Carcinoma

As the most prevalent type of mRNA modification in mammals, N6-methyladenosine (m6A) is involved in various biological processes. Accumulating studies have indicated that the deregulation of m6A RNA modification is linked to cancer and other diseases. However, its implications in hepatocellular carcinoma (HCC) remain poorly characterized. Herein, we sought to investigate the expression pattern of 13 key regulators for m6A RNA modification and to evaluate their prognostic value in HCC. First, we systematically analyzed data from The Cancer Genome Atlas (TCGA) database pertaining to patient clinical information and mRNA gene expression data. We found that 11 out of 13 key regulators for m6A RNA modification showed significantly higher expression levels in HCC. Subsequently, we identified two subgroups (clusters 1 and 2) via consensus clustering based on the expression of 13 m6A RNA methylation regulators. Cluster 2 had a worse prognosis and was also significantly correlated with higher histological grade and pathological stage when compared with cluster 1. Moreover, cluster 2 was remarkedly enriched for cancer-related pathways. We further constructed a robust risk signature of five regulators for m6A RNA modification. Further analysis indicated that this risk signature could be an independent prognostic factor for HCC, and the prognostic relevance of this five-gene risk signature was successfully validated using the Gene Expression Omnibus (GEO) dataset. Finally, we established a novel prognostic nomogram on the basis of age, gender, histological grade, pathological stage, and risk score to precisely predict the prognosis of patients with HCC. In summary, we herein uncovered the vital role of regulators for m6A RNA modification in HCC and developed a risk signature as a promising prognostic marker in HCC patients.

Principles of RNA methylation and their implications for biology and medicine

RNA methylation is a post-transcriptional level of regulation. At present, more than 150 kinds of RNA modifications have been identified. They are widely distributed in messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), noncoding small RNA (sncRNA) and long-chain non-coding RNA (lncRNA). In recent years, with the discovery of RNA methylation related proteins and the development of high-throughput sequencing technology, the mystery of RNA methylation has been gradually revealed, and its biological function and application value have gradually emerged. In this review, a large number of research results of RNA methylation in recent years are collected. Through systematic summary and refinement, this review introduced RNA methylation modification-related proteins and RNA methylation sequencing technologies, as well as the biological functions of RNA methylation, expressions and applications of RNA methylation-related genes in physiological or pathological states such as cancer, immunity and virus infection, and discussed the potential therapeutic strategies.

The Potential Roles of RNA N6-Methyladenosine in Urological Tumors

N6-methyladenosine (m⁶A) is regarded as the most abundant, prevalent and conserved internal mRNA modification in mammalian cells. M⁶A can be catalyzed by m⁶A methyltransferases METTL3, METTL14 and WTAP (writers), reverted by demethylases ALKBH5 and FTO (erasers), and recognized by m⁶A -binding proteins such as YTHDF1/2/3, IGF2BP1/2/3 and HNRNPA2B1 (readers). Emerging evidence suggests that m⁶A modification is significant for regulating many biological and cellular processes and participates in the pathological development of various diseases, including tumors. This article reviews recent studies on the biological function of m⁶A modification and the methylation modification of m⁶A in urological tumors.

The contribution of WTAP gene variants to Wilms tumor susceptibility

Wilms tumor is the most frequently occurring pediatric renal malignancy. Wilms tumor suppressor-1-associated protein (WTAP) is a vital component of N6-methyltransferase complex involved in tumorigenesis. However, the roles of WTAP gene single nucleotide polymorphisms (SNPs) in Wilms tumor risk have not been clarified to date. We successfully genotyped three WTAP gene SNPs using TaqMan assay in 405 Wilms tumor patients and 1197 cancer-free controls of Chinese children. Odds ratios (ORs) and 95% confidence intervals (CIs) were applied to determine the effects of WTAP gene SNPs on Wilms tumor risk. Carriers of the rs1853259 G variant are less susceptible to developing Wilms tumor, with an adjusted OR of 0.78 (AG vs. AA: 95% CI = 0.61-0.995, P = 0.046). Single locus analysis of rs9457712 G > A and rs7766006 G > T, as well as the combined analysis of risk genotypes, failed to unveil an association with Wilms tumor risk, respectively. Stratified analysis of the three SNPs and their combined risk effects showed more significant relationships with Wilms tumor risk under certain subgroups. In all, we found weak evidence of the association between WTAP gene SNPs and the risk of Wilms tumor. Further replication studies with greater sample size and different ethnicities are necessary to verify our findings.

Fusarium infection alters the m6A-modified transcript landscape in the cornea

N6-methyladenosine (m⁶A) is the most common post-transcriptional modification of RNA in eukaryotes that regulates the post-transcriptional expression level of genes without changing the base sequence. The role of m⁶A in fungal keratitis has not yet been elucidated. Here, we aimed to identify m⁶A modification changes and their potential roles in fungal keratitis. The murine model of fungal keratitis was established by inoculating mice with Fusarium solani (F. solani). The overall m⁶A level was detected via an m⁶A RNA methylation assay kit. The expression levels of key m⁶A modification-related genes were estimated by quantitative real-time polymerase chain reaction (PCR). The expression and localization of METTL (methyltransferase like)3, the key component of the m⁶A methyltransferase complex, was determined by immunostaining and Western blotting (WB). Immunoprecipitation methylation microarray was used to describe the changes in m⁶A modification in F. solani-infected corneal tissue. The overall m⁶A level in corneal tissue on the 5th day in the F. solani-treated group was upregulated compared with that in the control group. The demethylase levels were unaltered, but the level of the methylase METTL3 was increased significantly after fungal infection. Additionally, differences were found in m⁶A modifications in 1137 mRNAs, of which 780 were hypermethylated and 357 were hypomethylated. To the best of our knowledge, the present work is the first investigation on the m⁶A modification profiles in experimental fungal keratitis, and it may provide a potential therapeutic target.

Epitranscriptomics in liver disease: Basic concepts and therapeutic potential

The development of next-generation sequencing technology and the discovery of specific antibodies targeting chemically modified nucleotides have paved the way for a new era of epitranscriptomics. Cellular RNA is known to dynamically and reversibly undergo different chemical modifications after transcription, such as N⁶-methyladenosine (m⁶A), N¹-methyladenosine, N⁶,2'-O-dimethyladenosine, 5-methylcytosine, and 5-hydroxymethylcytidine, whose identity and location comprise the field of epitranscriptomics. Dynamic post-transcriptional modifications determine the fate of target RNAs by regulating various aspects of their processing, including RNA export, transcript processing, splicing, and degradation. The most abundant internal mRNA modification in eukaryotic cells is m⁶A, which exhibits essential roles in physiological processes, such as embryogenesis, carcinogenesis, and neurogenesis. m⁶A is deposited by the m⁶A methyltransferase complex (composed of METTL3/14/16, WTAP, KIAA1429, and RBM15/15B), erased by demethylases (FTO and ALKBH5), and recognised by binding proteins (e.g., YTHDF1/2/3, YTHDC1/2, IGF2BP1/2/3). The liver is the largest digestive and metabolic organ, and m⁶A modifications play unique roles in critical physiological hepatic functions and various liver diseases. This review focuses on the biological roles of m⁶A RNA methylation in lipid metabolism, viral hepatitis, non-alcoholic fatty liver disease, liver cancer, and tumour metastasis. In addition, we summarise the existing inhibitors targeting m⁶A regulators and discuss the potential of modulating m⁶A modifications as a therapeutic strategy.

Development and validation of a m6A-related gene signature for predicting the prognosis of hepatocellular carcinoma

Background: This study aimed to investigate the prognostic role of m⁶A methylation regulators in hepatocellular carcinoma (HCC). Materials & methods: Gene expression matrices were downloaded from The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium, and Gene Expression Omnibus databases. Univariate and multivariate regression analysis were utilized to determine the m⁶A risk genes. Results: Two m⁶A-related risk genes (YTHDF1, YTHDF2) were identified in the TCGA HCC cohort. The m⁶A-correlated risk score is an independent risk factor for the overall survival of the TCGA HCC cohort. Finally, we verified the reliability of our results using three external datasets. Conclusion: The m⁶A-correlated gene signature has prognostic value in HCC patients and thus provides guidance for the treatment of HCC.

Roles of METTL3 in cancer: mechanisms and therapeutic targeting

N⁶-methyladenosine (m⁶A) is the most abundant mRNA modification and is catalyzed by the methyltransferase complex, in which methyltransferase-like 3 (METTL3) is the sole catalytic subunit. Accumulating evidence in recent years reveals that METTL3 plays key roles in a variety of cancer types, either dependent or independent on its m⁶A RNA methyltransferase activity. While the roles of m⁶A modifications in cancer have been extensively reviewed elsewhere, the critical functions of METTL3 in various types of cancer, as well as the potential targeting of METTL3 as cancer treatment, have not yet been highlighted. Here we summarize our current understanding both on the oncogenic and tumor-suppressive functions of METTL3, as well as the underlying molecular mechanisms. The well-documented protein structure of the METTL3/METTL14 heterodimer provides the basis for potential therapeutic targeting, which is also discussed in this review.

m6A RNA Methylation: Ramifications for Gene Expression and Human Health

Cellular transcriptomes are frequently adorned by a variety of chemical modification marks, which in turn have a profound influence on its functioning. Of these modifications, the one which has invited a lot of attention in the recent years is m6A RNA methylation, leading to the development of RNA epigenetics or epitranscriptomics as a frontier research area. m6A RNA methylation is one of the most abundant reversible internal modification seen in cellular RNAs. Studies in the last few years have not only shed light on the molecular machinery involved in m6A RNA methylation but also on the impact of this modification in regulating gene expression and hence biological processes. In this review, we will emphasize the biological impact of this modification in normal organismal development and diseases.

WTAP promotes osteosarcoma tumorigenesis by repressing HMBOX1 expression in an m6A-dependent manner

N⁶-methyladenosine (m⁶A) regulators are involved in the progression of various cancers via regulating m⁶A modification. However, the potential role and mechanism of the m⁶A modification in osteosarcoma remains obscure. In this study, WTAP was found to be highly expressed in osteosarcoma tissue and it was an independent prognostic factor for overall survival in osteosarcoma. Functionally, WTAP, as an oncogene, was involved in the proliferation and metastasis of osteosarcoma in vitro and vivo. Mechanistically, M⁶A dot blot, RNA-seq and MeRIP-seq, MeRIP-qRT-PCR and luciferase reporter assays showed that HMBOX1 was identified as the target gene of WTAP, which regulated HMBOX1 stability depending on m⁶A modification at the 3′UTR of HMBOX1 mRNA. In addition, HMBOX1 expression was downregulated in osteosarcoma and was an independent prognostic factor for overall survival in osteosarcoma patients. Silenced HMBOX1 evidently attenuated shWTAP-mediated suppression on osteosarcoma growth and metastasis in vivo and vitro. Finally, WTAP/HMBOX1 regulated osteosarcoma growth and metastasis via PI3K/AKT pathway. In conclusion, this study demonstrated the critical role of the WTAP-mediated m⁶A modification in the progression of osteosarcoma, which could provide novel insights into osteosarcoma treatment.

Roles of N6 -methyladenosine (m6 A) RNA modifications in urological cancers

Epigenetics has long been a hot topic in the field of scientific research. The scope of epigenetics usually includes chromatin remodelling, DNA methylation, histone modifications, non-coding RNAs and RNA modifications. In recent years, RNA modifications have emerged as important regulators in a variety of physiological processes and in disease progression, especially in human cancers. Among the various RNA modifications, m⁶ A is the most common. The function of m⁶ A modifications is mainly regulated by 3 types of proteins: m⁶ A methyltransferases (writers), m⁶ A demethylases (erasers) and m⁶ A-binding proteins (readers). In this review, we focus on RNA m⁶ A modification and its relationship with urological cancers, particularly focusing on its roles and potential clinical applications.

Role of methyltransferase-like enzyme 3 and methyltransferase-like enzyme 14 in urological cancers

N6-methyladenosine (m6A) modifications can be found in eukaryotic messenger RNA (mRNA), long non-coding RNA (lncRNA), and microRNA (miRNA). Several studies have demonstrated a close relationship between m6A modifications and cancer cells. Methyltransferase-like enzyme 3 (METTL3) and methyltransferase-like enzyme 14 (METTL14) are two major enzymes involved in m6A modifications that play vital roles in various cancers. However, the roles and regulatory mechanisms of METTL3 and METTL14 in urological cancers are largely unknown. In this review, we summarize the current research results for METTL3 and METTL14 and identify potential pathways involving these enzymes in kidney, bladder, prostate, and testicular cancer. We found that METTL3 and METTL14 have different expression patterns in four types of urological cancers. METTL3 is highly expressed in bladder and prostate cancer and plays an oncogenic role on cancer cells; however, its expression and role are opposite in kidney cancer. METTL14 is expressed at low levels in kidney and bladder cancer, where it has a tumor suppressive role. Low METTL3 or METTL14 expression in cancer cells negatively regulates cell growth-related pathways (e.g., mTOR, EMT, and P2XR6) but positively regulates cell death-related pathways (e.g., P53, PTEN, and Notch1). When METTL3 is highly expressed, it positively regulates the NF-kB and SHH-GL1pathways but negatively regulates PTEN. These results suggest that although METTL3 and METTL14 have different expression levels and regulatory mechanisms in urological cancers, they control cancer cell fate via cell growth- and cell death-related pathways. These findings suggest that m6A modification may be a potential new therapeutic target in urological cancer.

The m6A methylation regulator-based signature for predicting the prognosis of prostate cancer

Aim: To construct a survival prediction signature for prostate cancer (PC) based on the RNA N6-methyladenosine (m6A) methylation regulator. Materials & methods: This paper explores the interaction network of differentially expressed m6A RNA methylation regulators in PC by Pearson correlation analysis. Univariate Cox risk regression and LASSO regression analysis were used to construct a predictive signature of PC. Kaplan-Meier survival analysis compared the overall survival of the high- and low-risk groups. Results & Conclusion: We first constructed a prognostic two gene signature for PC based on the m6A RNA methylation regulators MRTTL14 and YTHDF2. The interaction network of m6A RNA methylation regulators in PC was also established.

Critical Roles of N6-Methyladenosine (m6A) in Cancer and Virus Infection

Studies have shown that epigenetic abnormalities are involved in various diseases, including cancer. In particular, in order to realize precision medicine, the integrated analysis of genetics and epigenetics is considered to be important; detailed epigenetic analysis in the medical field has been becoming increasingly important. In the epigenetics analysis, DNA methylation and histone modification analyses have been actively studied for a long time, and many important findings were accumulated. On the other hand, recently, attention has also been focused on RNA modification in the field of epigenetics; now it is known that RNA modification is associated with various biological functions, such as regulation of gene expression. Among RNA modifications, functional analysis of N⁶-methyladenosine (m⁶A), the most abundant RNA modification found from humans to plants is actively progressing, and it has also been known that m⁶A abnormality is involved in cancer and other diseases. Importantly, recent studies have shown that m⁶A is related to viral infections. Considering the current world situation under threat of viral infections, it is important to deepen knowledge of RNA modification from the viewpoint of viral diseases. Hence, in this review, we have summarized the recent findings regarding the roles of RNA modifications in biological functions, cancer biology, and virus infection, particularly focusing on m⁶A in mRNA.

Prognostic values of m6A RNA methylation regulators in differentiated Thyroid Carcinoma

N6-methyladenosine (m6A) is the most prevalent modification of RNA in mammals. m6A RNA methylation levels are dynamically regulated by m6A RNA methylation regulators. While increasing evidence has suggested that m6A RNA methylation is vital in the initiation and progression of human carcinoma, little is known about the expression and effect of m6A RNA methylation regulators in differentiated thyroid carcinoma (DTC). Herein, we demonstrate that most of the thirteen main m6A RNA methylation regulators are differentially expressed in DTC tissues and normal thyroid tissues. Based on consensus clustering of m6A RNA methylation regulators, DTC cases were divided into two subgroups (TC1 and TC2). Compared with the TC1 subgroup, the TC2 subgroup was associated with a poorer prognosis, older age, higher T grade, higher N grade and higher TNM stage. The results indicated that alteration of m6A RNA methylation regulators was closely related to DTC. We further established a risk signature of four m6A RNA methylation regulators that could evaluate prognosis and clinicopathological features in DTC. Finally, the results of the TCGA analysis were verified by other cohorts from Gene Expression Omnibus (GEO) database. In conclusion, m6A RNA methylation regulators play a crucial part in the progression of DTC and are potentially useful for evaluating the prognosis and providing potential novel insights into treatment strategies.

The m6A reader YTHDF1 promotes ovarian cancer progression via augmenting EIF3C translation

N⁶-Methyladenosine (m⁶A) is the most abundant RNA modification in mammal mRNAs and increasing evidence suggests the key roles of m⁶A in human tumorigenesis. However, whether m⁶A, especially its ‘reader’ YTHDF1, targets a gene involving in protein translation and thus affects overall protein production in cancer cells is largely unexplored. Here, using multi-omics analysis for ovarian cancer, we identified a novel mechanism involving EIF3C, a subunit of the protein translation initiation factor EIF3, as the direct target of the YTHDF1. YTHDF1 augments the translation of EIF3C in an m⁶A-dependent manner by binding to m⁶A-modified EIF3C mRNA and concomitantly promotes the overall translational output, thereby facilitating tumorigenesis and metastasis of ovarian cancer. YTHDF1 is frequently amplified in ovarian cancer and up-regulation of YTHDF1 is associated with the adverse prognosis of ovarian cancer patients. Furthermore, the protein but not the RNA abundance of EIF3C is increased in ovarian cancer and positively correlates with the protein expression of YTHDF1 in ovarian cancer patients, suggesting modification of EIF3C mRNA is more relevant to its role in cancer. Collectively, we identify the novel YTHDF1-EIF3C axis critical for ovarian cancer progression which can serve as a target to develop therapeutics for cancer treatment.

The m6A Methylation-Regulated AFF4 Promotes Self-Renewal of Bladder Cancer Stem Cells

The dynamic N⁶-methyladenosine (m⁶A) modification of mRNA plays a role in regulating gene expression and determining cell fate. However, the functions of m⁶A mRNA modification in bladder cancer stem cells (BCSCs) have not been described. Here, we show that global RNA m⁶A abundance and the expression of m⁶A-forming enzyme METTL3 are higher in BCSCs than those in non-CSCs of bladder cancer (BCa) cells. The depletion of the METTL3 inhibited the self-renewal of BCSCs, as evidenced by decreased ALDH activity and sphere-forming ability. Mechanistically, METTL3 regulates the m⁶A modification and thereby the expression of AF4/FMR2 family member 4 (AFF4), knockdown of which phenocopies the METTL3 ablation and diminishes the tumor-initiating capability of BCSCs in vivo. AFF4 binds to the promoter regions and sustains the transcription of SOX2 and MYC which have critical biological functions in BCSCs. Collectively, our results demonstrate the critical roles of m⁶A modification in self-renewal and tumorigenicity of BCSCs through a novel signaling axis of METTL3-AFF4-SOX2/MYC.

METTL3 and N6-Methyladenosine Promote Homologous Recombination-Mediated Repair of DSBs by Modulating DNA-RNA Hybrid Accumulation

Double-strand breaks (DSBs) are the most deleterious DNA lesions, which, if left unrepaired, may lead to genome instability or cell death. Here, we report that, in response to DSBs, the RNA methyltransferase METTL3 is activated by ATM-mediated phosphorylation at S43. Phosphorylated METTL3 is then localized to DNA damage sites, where it methylates the N6 position of adenosine (m6A) in DNA damage-associated RNAs, which recruits the m6A reader protein YTHDC1 for protection. In this way, the METTL3-m6A-YTHDC1 axis modulates accumulation of DNA-RNA hybrids at DSBs sites, which then recruit RAD51 and BRCA1 for homologous recombination (HR)-mediated repair. METTL3-deficient cells display defective HR, accumulation of unrepaired DSBs, and genome instability. Accordingly, depletion of METTL3 significantly enhances the sensitivity of cancer cells and murine xenografts to DNA damage-based therapy. These findings uncover the function of METTL3 and YTHDC1 in HR-mediated DSB repair, which may have implications for cancer therapy.

METTL3-mediated m6A modification of HDGF mRNA promotes gastric cancer progression and has prognostic significance

OBJECTIVE

N⁶-methyladenosine (m⁶A) RNA methylation and its associated methyltransferase METTL3 are involved in tumour initiation and progression via the regulation of RNA function. This study explored the biological function and clinical significance of METTL3 in gastric cancer (GC).

DESIGN

The prognostic value of METTL3 expression was evaluated using tissue microarray and immunohistochemical staining analyses in a human GC cohort. The biological role and mechanism of METTL3 in GC tumour growth and liver metastasis were determined in vitro and in vivo.

RESULTS

The level of m⁶A RNA was significantly increased in GC, and METTL3 was the main regulator involved in the abundant m⁶A RNA modification. METTL3 expression was significantly elevated in GC tissues and associated with poor prognosis. Multivariate Cox regression analysis revealed that METTL3 expression was an independent prognostic factor and effective predictor in human patients with GC. Moreover, METTL3 overexpression promoted GC proliferation and liver metastasis in vitro and in vivo. Mechanistically, P300-mediated H3K27 acetylation activation in the promoter of METTL3 induced METTL3 transcription, which stimulated m⁶A modification of HDGF mRNA, and the m⁶A reader IGF2BP3 then directly recognised and bound to the m⁶A site on HDGF mRNA and enhanced HDGF mRNA stability. Secreted HDGF promoted tumour angiogenesis, while nuclear HDGF activated GLUT4 and ENO2 expression, followed by an increase in glycolysis in GC cells, which was correlated with subsequent tumour growth and liver metastasis.

CONCLUSIONS

Elevated METTL3 expression promotes tumour angiogenesis and glycolysis in GC, indicating that METTL3 expression is a potential prognostic biomarker and therapeutic target for human GC.

m6A RNA methylation regulators have prognostic value in papillary thyroid carcinoma

BACKGROUND

N⁶-Methyladenosine (m⁶A) is a ubiquitous RNA modification with vital roles in various cancers, but little is known about its role in papillary thyroid carcinoma (PTC), a common endocrine malignancy.

METHODS

In this study, an m⁶A RNA methylation regulator-based biomarker signature was developed for the effective prediction of prognosis in patients with PTC. The gene expression profiles of m⁶A RNA methylation regulators and the corresponding clinical information was downloaded from The Cancer Genome Atlas (TCGA). Differentially expressed m⁶A RNA methylation regulators between tumor and normal control samples, and correlation expression levels, clinical parameters, and outcomes were evaluated. And a prognostic signature was built using a PTC cohort from TCGA.

RESULTS

The expression level of HNRNPC was remarkably upregulated in tumor samples, while WTAP, RBM15, YTHDC2, YTHDC1, FTO, METTL14, METTL3, ALKBH5, KIAA1429, YTHDF1, and ZC3H13 were significantly downregulated in the cancer specimens compared with those in control samples. A three-gene prognostic signature comprising RBM15, KIAA1429, and FTO could predict overall survival in patients with PTC. In addition, the prognostic signature-based risk score was identified as an independent prognostic indicator for PTC.

CONCLUSIONS

We established a robust m⁶A RNA methylation regulator-based molecular signature for predicting prognosis in patients with PTC with high accuracy; this signature might provide important guidance for therapeutic strategies.

The m6A-Related mRNA Signature Predicts the Prognosis of Pancreatic Cancer Patients

N6-methyladenosine (m6A) has an important epitranscriptomic modification that controls cancer self-renewal and cell fate. The addition of m6A to mRNA is a reversible modification. The deposition of m6A is encoded by a methyltransferase complex involving three homologous factors, jargonized as "writers," "erasers," and "readers." However, their roles in pancreatic adenocarcinoma (PAAD) are underexploited. With the use of The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases, we provided an mRNA signature that may improve the prognostic prediction of PAAD patients based on the genetic status of m6A regulators. PAAD patients with genetic alteration of m6A regulators had worse disease-free and overall survival. After comparing PAAD groups with/without genetic alteration of m6A regulators, we identified 196 differentially expressed genes (DEGs). Then, we generated a 16-mRNA signature score system through least absolute shrinkage and selection operator (LASSO) Cox regression analysis. Multivariate cox regression analysis demonstrated that a high-risk score significantly correlates with poor prognosis. Moreover, time-dependent receiver operating characteristic (ROC) curves revealed it was effective in predicting the overall survival in both training and validation sets. PAH, ZPLD1, PPFIA3, and TNNT1 from our signature also exhibited an independent prognostic value. Collectively, these findings can improve the understanding of m6A modifications in PAAD and potentially guide therapies in PAAD patients.

N6-methyladenine RNA modification and cancer

N6-methyladenosine (m6A) in messenger RNA (mRNA) is regulated by m6A methyltransferases and demethylases. Modifications of m6A are dynamic and reversible, may regulate gene expression levels and serve vital roles in numerous life processes, such as cell cycle regulation, cell fate decision and cell differentiation. In recent years, m6A modifications have been reported to exhibit functions in human cancers via regulation of RNA stability, microRNA processing, mRNA splicing and mRNA translation, including lung cancer, breast tumor and acute myeloid leukemia. In the present review, the roles of m6A modifications in the onset and progression of cancer were summarized. These modifications display an oncogenic role in certain types of cancer, whereas in other types of cancer they exhibit a tumor suppressor role. Therefore, understanding the biological functions performed by m6A in different types of tumors and identifying pivotal m6A target genes to deduce the potential mechanisms underlying the progression of cancer may assist in the development of novel therapeutics.

The role of N6-methyladenosine (m6A) modification in the regulation of circRNAs

N⁶-methyladenosine (m⁶A), the most abundant modification in eukaryotic cells, regulates RNA transcription, processing, splicing, degradation, and translation. Circular RNA (circRNA) is a class of covalently closed RNA molecules characterized by universality, diversity, stability and conservatism of evolution. Accumulating evidence shows that both m⁶A modification and circRNAs participate in the pathogenesis of multiple diseases, such as cancers, neurological diseases, autoimmune diseases, and infertility. Recently, m⁶A modification has been identified for its enrichment and vital biological functions in regulating circRNAs. In this review, we summarize the role of m⁶A modification in the regulation and function of circRNAs. Moreover, we discuss the potential applications and possible future directions in the field.

METTL3 Induces AAA Development and Progression by Modulating N6-Methyladenosine-Dependent Primary miR34a Processing

Identifying effective drugs to delay the progression of aortic aneurysms is a formidable challenge in vascular medicine. Methyltransferase-like 3 (METTL3) plays a key role in catalyzing the formation of N6-methyladenosine (m⁶A), but despite the functional importance of METTL3 and m⁶A in various fundamental biological processes, their roles in abdominal aortic aneurysm (AAA) are unknown. Here, we found that METTL3 knockdown in apolipoprotein E-deficient (ApoE^−/−) mice treated with angiotensin II suppressed the formation of AAAs, while METTL3 overexpression exerted the opposite effects. Similar results were obtained in a calcium chloride (CaCl₂)-induced mouse AAA model. Mechanistically, METTL3-dependent m⁶A methylation promoted primary microRNA-34a (miR-34a, pri-miR34a) maturation through DGCR8. Moreover, miR-34a overexpression significantly decreased SIRT1 expression and aggravated AAA formation, while miR-34a deficiency produced the opposite effects. In a rescue experiment, miR-34a knockdown or forced expression of SIRT1 partially attenuated the protective effects of METTL3 deficiency against AAA formation. Our studies reveal an important role for METTL3/m⁶A-mediated miR-34a maturation in AAA formation and provide a novel therapeutic target and diagnostic biomarker for AAA treatment.

Mechanism of RNA modification N6-methyladenosine in human cancer

Since the breakthrough discoveries of DNA and histone modifications, the field of RNA modifications has gained increasing interest in the scientific community. The discovery of N6-methyladenosine (m6A), a predominantly internal epigenetic modification in eukaryotes mRNA, heralded the creation of the field of epi-transcriptomics. This post-transcriptional RNA modification is dynamic and reversible, and is regulated by methylases, demethylases and proteins that preferentially recognize m6A modifications. Altered m6A levels affect RNA processing, degradation and translation, thereby disrupting gene expression and key cellular processes, ultimately resulting in tumor initiation and progression. Furthermore, inhibitors and regulators of m6A-related factors have been explored as therapeutic approaches for treating cancer. In the present review, the mechanisms of m6A RNA modification, the clinicopathological relevance of m6A alterations, the type and frequency of alterations and the multiple functions it regulates in different types of cancer are discussed.

Overexpression of METTL3 associated with the metabolic status on 18F-FDG PET/CT in patients with Esophageal Carcinoma

Background: To investigate the expression of methyltransferase 3 (METTL3) and its relationship with ¹⁸F-FDG uptake in patients with esophageal carcinoma (ESCA). Materials and methods: This study analyzed the expression of METTL3 in ESCA and its relationship with clinicopathological features by The Cancer Genome Atlas (TCGA) database. Immunohistochemical staining was performed on 57 tumor tissues of ESCA patients who underwent PET/CT scan before surgery to evaluate the expression of METTL3, glucose transporter 1 (GLUT1), and hexokinase 2 (HK2) in tumor tissues and peritumoral tissues. Analyze the relationship between SUVmax with METTL3, HK2, and GLUT1 expression. Results: The expression of METTL3, GLUT1, and HK2 was significantly increased in ESCA tissues compared with normal tissues (p < 0.001). The expression of METTL3 was correlated with tumor size and histological differentiation (p < 0.05), and there was no significant difference between age, sex, pathological types, tumor staging, or lymph node metastasis (p > 0.05). The SUVmax was significantly higher in tumors with high METTL3 expression (17.822±6.249) compared to low METTL3 expression (9.573±5.082) (p < 0.001). There was a positive correlation between the SUVmax and METTL3 expression in ESCA (r² = 0.647, p < 0.001). Multivariate analysis confirmed the association between SUVmax and METTL3 expression (p < 0.05). GLUT1 and HK2 expression in ESCA was positively correlated with ¹⁸F-FDG uptake and METTL3 status (p < 0.001). Conclusions: The high expression of METTL3 is related to the high SUVmax in ESCA, and METTL3 may increase ¹⁸F-FDG uptake by regulating GLUT1 and HK2.

Gambogenic acid suppresses bladder cancer cells growth and metastasis by regulating NF-κB signaling

BACKGROUND

Gambogenic acid (GNA) is one of the main active components of Gamboge, and its anticancer role has been reported in some cancers. The study was to investigate the inhibitory effects of GNA on the proliferation and metastasis of bladder cancer (BC) cells and its potential regulatory mechanisms.

MATERIALS AND METHODS

BC cell lines (BIU-87 cells, T24 cells, and J82 cells) were treated with different doses of GNA for different time, and then the effects of GNA on BC cell were examined in vitro using CCK-8 assay, apoptosis assays, and Transwell tests. NF-κB signaling activity was detected by the NF-κB p65 luciferase reporter assay. Western blot was used to detect the expressions of cIAP2, XIAP, Survivin, and p65.

RESULTS

GNA inhibited the viability of BC cells in vitro in a dose- and time-dependent manner and facilitated apoptosis of BC cells. Moreover, GNA could remarkably impede the migration and invasion abilities of BC cells. In terms of mechanism, GNA administration reduced the activity of NF-κB signaling and down-regulated the expressions of p65, survivin, XIAP, and cIAP2.

CONCLUSION

GNA blocks the growth and metastasis of BC cells via inhibiting the NF-κB signal transduction pathway.

Diverse molecular functions of m6A mRNA modification in cancer

N⁶-methyladenosine (m⁶A), the most prevalent chemical modification found on eukaryotic mRNA, is associated with almost all stages of mRNA metabolism and influences various human diseases. Recent research has implicated the aberrant regulation of m⁶A mRNA modification in many human cancers. An increasing number of studies have revealed that dysregulation of m⁶A-containing gene expression via the abnormal expression of m⁶A methyltransferases, demethylases, or reader proteins is closely associated with tumorigenicity. Notably, the molecular functions and cellular consequences of m⁶A mRNA modification often show opposite results depending on the degree of m⁶A modification in specific mRNA. In this review, we highlight the current progress on the underlying mechanisms of m⁶A modification in mRNA metabolism, particularly the functions of m⁶A writers, erasers, and readers in the context of tumorigenesis.

A thorough investigation into the role and function of RNA modifications in cancers could yield novel therapies. The chemical modification of messenger RNA (mRNA), the molecule that carries code from DNA to synthesize proteins, is thought to play a role in influencing genetically inherited traits and diseases. A common modification found in mRNA is N⁶-methyladenosine (m⁶A). Disruption to the regulation of m⁶A modification has been linked with human cancers. Junho Choe and Seung Hun Han at Hanyang University in Seoul, South Korea, reviewed current understanding of the molecular mechanisms behind m⁶A modification, with particular reference to tumor formation. The researchers point out that abnormal expression of proteins associated with m⁶A may lead to heightened expression of cancer-related genes. More extensive m⁶A modification levels are also linked to tumor formation.

The potential role of RNA N6-methyladenosine in Cancer progression

N6-methyladenosine (m6A) is considered the most common, abundant, and conserved internal transcript modification, especially in eukaryotic messenger RNA (mRNA). m6A is installed by m6A methyltransferases (METTL3/14, WTAP, RBM15/15B, VIRMA and ZC3H13, termed “writers”), removed by demethylases (FTO, ALKBH5, and ALKBH3, termed “erasers”), and recognized by m6A-binding proteins (YTHDC1/2, YTHDF1/2/3, IGF2BP1/2/3, HNRNP, and eIF3, termed “readers”). Accumulating evidence suggests that m6A RNA methylation greatly impacts RNA metabolism and is involved in the pathogenesis of many kinds of diseases, including cancers. In this review, we focus on the physiological functions of m6A modification and its related regulators, as well as on the potential biological roles of these elements in human tumors.

Identification of a m6A RNA methylation regulators-based signature for predicting the prognosis of clear cell renal carcinoma

Background

The mortality rate of clear cell renal cell carcinoma (ccRCC) remains high. The aim of this study was to identify novel prognostic biomarkers by using m⁶A RNA methylation regulators capable of improving the risk-stratification criteria of survival for ccRCC patients.

Methods

The gene expression data of 16 m⁶A methylation regulators and its relevant clinical information were extracted from The Cancer Genome Atlas (TCGA) database. The expression pattern of these m⁶A methylation regulators were evaluated. Consensus clustering analysis was conducted to identify clusters of ccRCC patients with different prognosis. Univariate, least absolute shrinkage and selection operator (LASSO), and multivariate Cox regression analysis were performed to construct multiple-gene risk signature. A survival analysis was carried out to determine the independent prognostic significance of the signature.

Results

Five m⁶A-related genes (ZC3H13, METTL14, YTHDF2, YTHDF3 and HNRNPA2B1) showed significantly downregulated in tumor tissue, while seven regulators (YTHDC2, FTO, WTAP, METTL3, ALKBH5, RBM15 and KIAA1429) was remarkably upregulated in ccRCC. Consensus clustering analysis identified two clusters of ccRCC with significant differences in overall survival (OS) and tumor stage between them. We also constructed a two-gene signature, METTL3 and METTL14, serving as an independent prognostic indicator for distinguishing ccRCC patients with different prognosis both in training, validation and our own clinical datasets. The receiver operator characteristic (ROC) curve indicated the area under the curve (AUC) in these three datasets were 0.721, 0.684 and 0.828, respectively, demonstrated that the prognostic signature had a good prediction efficiency.

Conclusions

m⁶A methylation regulators exert as potential biomarkers for prognostic stratification of ccRCC patients and may assist clinicians achieving individualized treatment for this patient population.