N 6-methyladenosine RNA methylation: From regulatory mechanisms to potential clinical applications

Unveiling the role of RNA methylation in glioma: Mechanisms, prognostic biomarkers, and therapeutic targets

Gliomas, the most prevalent malignant brain tumors in the central nervous system, are marked by rapid growth, high recurrence rates, and poor prognosis. Glioblastoma (GBM) stands out as the most aggressive subtype, characterized by significant heterogeneity. The etiology of gliomas remains elusive. RNA modifications, particularly reversible methylation, play a crucial role in regulating transcription and translation throughout the RNA lifecycle. Increasing evidence highlights the prevalence of RNA methylation in primary central nervous system malignancies, underscoring its pivotal role in glioma pathogenesis. This review focuses on recent findings regarding changes in RNA methylation expression and their effects on glioma development and progression, including N6-methyladenosine (m6A), 5-methylcytosine (m5C), N1-methyladenosine (m1A), and N7-methylguanosine (m7G). Given the extensive roles of RNA methylation in gliomas, the potential of RNA methylation-related regulators as prognostic markers and therapeutic targets was also explored, aiming to enhance clinical management and improve patient outcomes.

Causal pathways in lymphoid leukemia: the gut microbiota, immune cells, and serum metabolites

Background

We employed Mendelian randomization (MR) to investigate the causal relationship between the gut microbiota and lymphoid leukemia, further exploring the causal relationships among immune cells, lymphoid leukemia, and potential metabolic mediators.

Methods

We utilized data from the largest genome-wide association studies to date, encompassing 418 species of gut microbiota, 713 types of immune cells, and 1,400 serum metabolites as exposures. Summary statistics for lymphoid leukemia, acute lymphocytic leukemia (ALL), and chronic lymphocytic leukemia (CLL) were obtained from the FinnGen database. We performed bidirectional Mendelian analyses to explore the causal relationships among the gut microbiota, immune cells, serum metabolites, and lymphoid leukemia. Additionally, we conducted a two-step mediation analysis to identify potential intermediary metabolites between immune cells and lymphoid leukemia.

Results

Several gut microbiota were found to have causal relationships with lymphoid leukemia, ALL, and CLL, particularly within the Firmicutes and Bacteroidetes phyla. In the two-step MR analysis, various steroid hormone metabolites (such as DHEAS, pregnenolone sulfateprogestogen derivatives, and androstenediol-related compounds) were identified as potential intermediary metabolites between lymphoid leukemia and immune cells. In ALL, the causal relationship between 1-palmitoyl-2-docosahexaenoyl-GPE (16:0/22:6) and ALL was mediated by CD62L-plasmacytoid DC%DC (mediated proportion=-2.84%, P=0.020). In CLL, the causal relationship between N6,n6,n6-trimethyllysine and CLL was mediated by HLA DR+ CD8br AC (mediated proportion=4.07%, P=0.021).

Conclusion

This MR study provides evidence supporting specific causal relationships between the gut microbiota and lymphoid leukemia, as well as between certain immune cells and lymphoid leukemia with potential intermediary metabolites.

Influence of RNA Methylation on Cancerous Cells: A Prospective Approach for Alteration of In Vivo Cellular Composition

RNA methylation is a dynamic and ubiquitous post-transcriptional modification that plays a pivotal role in regulating gene expression in various conditions like cancer, neurological disorders, cardiovascular diseases, viral infections, metabolic disorders, and autoimmune diseases. RNA methylation manifests across diverse RNA species including messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA), exerting pivotal roles in gene expression regulation and various biological phenomena. Aberrant activity of writer, eraser, and reader proteins enables dysregulated methylation landscape across diverse malignancy transcriptomes, frequently promoting cancer pathogenesis. Numerous oncogenic drivers, tumour suppressors, invasion/metastasis factors, and signalling cascade components undergo methylation changes that modulate respective mRNA stability, translation, splicing, transport, and protein-RNA interactions accordingly. Functional studies confirm methylation-dependent alterations drive proliferation, survival, motility, angiogenesis, stemness, metabolism, and therapeutic evasion programs systemically. Methyltransferase overexpression typifies certain breast, liver, gastric, and other carcinomas correlating with adverse clinical outcomes like diminished overall survival. Mapping efforts uncover nodal transcripts for targeted drug development against hyperactivated regulators including METTL3. Some erasers and readers also suitable lead candidates based on apparent synthetic lethality. Proteomic screens additionally highlight relevant methylation-sensitive effector pathways amenable to combinatorial blockade, reversing compensatory signalling mechanisms that facilitate solid tumour progression. Quantifying global methylation burdens and responsible enzymes clinically predicts patient prognosis, risk stratification for adjuvant therapy, and overall therapeutic responsiveness.

The two-faced role of RNA methyltransferase METTL3 on cellular response to cisplatin in head and neck squamous cell carcinoma in vitro model

Background

RNA methyltransferase-like 3 (METTL3) is responsible for methyl group transfer in the progression of N 6-methyladenosine (m6A) modification. This epigenetic feature contributes to the structural and functional regulation of RNA and consequently may promote tumorigenesis, tumor progression, and cellular response to anticancer treatment (chemo-, radio-, and immunotherapy). In head and neck squamous cell carcinoma (HNSCC), the commonly used chemotherapy is cisplatin. Unfortunately, cisplatin resistance is still a major cause of tumor relapse and patients' death. Thus, this study aimed to investigate the role of METTL3 on cellular response to cisplatin in HNSCC in vitro models.

Materials and methods

HNSCC cell lines (H103, FaDu, and Detroit-562) with stable METTL3 knockdown (sgMETTL3) established with CRISPR-Cas9 system were treated with 0.5 tolerable plasma level (TPL) and 1 TPL of cisplatin. Further, cell cycle distribution, apoptosis, CD44/CD133 surface marker expression, and cell's ability to colony formation were analyzed in comparison to controls (cells transduced with control sgRNA).

Results

The analyses of cell cycle distribution and apoptosis indicated a significantly higher percentage of cells with METTL3 knockdown 1) arrested in the G2/S phase and 2) characterized as a late apoptotic or death in comparison to control. The colony formation assay showed intensified inhibition of a single cell's ability to grow into a colony in FaDu and Detroit-562 METTL3-deficient cells, while a higher colony number was observed in H103 METTL3 knockdown cells after cisplatin treatment. Also, METTL3 deficiency significantly increased cancer stem cell markers' surface expression in all studied cell lines.

Conclusion

Our findings highlight the significant influence of METTL3 on the cellular response to cisplatin, suggesting its potential as a promising therapeutic target for addressing cisplatin resistance in certain cases of HNSCC.

Reduced DNMT1 levels induce cell apoptosis via upregulation of METTL3 in cardiac hypertrophy

DNA methylation is also involved in the development and progression of cardiac diseases. Although studies have shown that DNA methylation and RNA m6A methylation play an important role in the development of myocardial hypertrophy, whether DNA methylation and RNA m6A methylation have a coordinated role in the development of myocardial hypertrophy and influence each other is still unknown. Here, we found that DNMT1 expression was downregulated in TAC mice and Ang II-treated NRCMs. Moreover, DNMT1 overexpression inhibited Ang II-induced apoptosis of NRCMs. Furthermore, we found that the expression of METTL3 was up-regulated after inhibiting the expression of DNMT1 by a DNMT1 inhibitor or small interfering RNA. In addition, ectopic expression DNMT1 inhibited METTL3 expression in NRCMs. Furthermore, METTL3 expression was elevated in NRCMs treated with Ang II, and suppression of METTL3 inhibited cell apoptosis induced by Ang II in NRCMs.In addition, this study revealed that the DNMT1/METTL3 pathway affected Ang II-induced apoptosis in NRCMs. Finally, this study found that DNMT1, but not METTL3, might directly regulated the ANP and BNP expression. Collectively, our findings revealed the role of the DNMT1/METTL3 pathway in cardiac hypertrophy and provided a novel molecular mechanism describing the physiological and pathological processes.

Comprehensive landscape of RNA N6-methyladenosine modification in lens epithelial cells from normal and diabetic cataract

To gain more insight into the mechanism of cataract formation from the perspective of epigenetics in the diabetic population, lens epithelium from diabetic cataract patients and health individuals were collected separately and analyzed for N6-methyladenosine (m6A)-modified RNA using methylated RNA immunoprecipitation sequencing (MeRIP-Seq). Subsequently, differential expression analysis was performed on m6A-regulated messenger RNA (mRNA), circular RNA (circRNA), and long non-coding RNA (lncRNA), followed by functional annotation using the Gene Ontology (GO) database. Furthermore, analysis of single-cell data of lens complemented the intrinsic association and cellular heterogeneity of cataract and m6A regulators. In this study, both the global expression levels and peak intensity of m6A-tagged RNAs were increased in patients with diabetic cataract. And we noted multiple core enzymes were upregulated in the diabetic cataract (DC) samples. Besides, single-cell RNA sequencing analysis of the lens revealed the heterogeneous expression of RNA m6A regulators across different cell types, and we noted that the early fiber cell cluster was also closely associated with the onset of cataract and m6A modification. The results comprehensively revealed the dynamic modification landscape of m6A on mRNA, circRNA, and lncRNA, which might provide valuable resources for future studies of the pathogenesis of DCs.

METTL3 regulates N6-methyladenosine modification of ANGPTL3 mRNA and potentiates malignant progression of stomach adenocarcinoma

BACKGROUND

N6-methyladenosine (m6A) is associated with mammalian mRNA biogenesis, decay, translation and metabolism, and also contributes greatly to gastrointestinal tumor formation and development. Therefore, the specific mechanisms and signaling pathways mediated by methyltransferase-like 3 (METTL3), which catalyzes the formation of m6A chemical labeling in stomach adenocarcinoma (STAD), are still worth exploring.

METHODS

Quantitative real-time PCR (qRT-PCR) was constructed to detect the expression of METTL3 in gastric cancer cell lines and patient tissues. The biological function of METTL3 was investigated in vitro/in vivo by Cell Counting Kit-8, colony formation assay, Transwell assay and nude mouse tumorigenesis assay. Based on the LinkedOmics database, the genes co-expressed with METTL3 in the TCGA STAD cohort were analyzed to clarify the downstream targets of METTL3. Methylated RNA immunoprecipitation-qPCR (MeRIP-qPCR) and RNA stability analysis were employed to explore the mechanism of METTL3 in gastric cancer progression.

RESULTS

We analyzed TCGA data and found that METTL3 was frequently elevated in STAD, and demonstrated that METTL3 was present at high levels in clinical STAD tissues and cells. High METTL3 expression was more likely to have advanced TNM tumors and distant metastasis. On the other hand, METTL3 silencing effectively impeded the higher oncogenic capacity of AGS and HGC27 cells in vivo and in vitro, as reflected by slowed cell growth and diminished migration and invasion capacities. Continued mining of the TCGA dataset identified the co-expression of angiopoietin-like 3 (ANGPTL3) and METTL3 in STAD. Lower level of ANGPTL3 was related to increased level of METTL3 in STAD samples and shorter survival times in STAD patients. ANGPTL3 enrichment limited the growth and metastasis of STAD cells. Besides, ANGPTL3 mRNA levels could be decreased by METTL3-dominated m6A modifications, a result derived from a combination of MeRIP-qPCR and RNA half-life experiments. Importantly, the inhibitory effect of METTL3 silencing on cancer could be reversed to some extent by ANGPTL3 inhibition.

CONCLUSIONS

Overall, our findings suggested that METTL3 functioned an oncogenic role in STAD by reducing ANGPTL3 expression in an m6A-dependent manner. The discovery of the METTL3-ANGPTL3 axis and its effect on STAD tumor growth will contribute to further studies on the mechanisms of gastric adenocarcinoma development.

Comprehensive analysis of differences in N6-methyladenosine RNA methylomes in Helicobacter pylori infection

Background: Helicobacter pylori (H.pylori) infection is an important factor in the occurrence of human gastric diseases, but its pathogenic mechanism is not clear. N6-methyladenosine (m6A) is the most prevalent reversible methylation modification in mammalian RNA and it plays a crucial role in controlling many biological processes. However, there are no studies reported that whether H. pylori infection impacts the m6A methylation of stomach. In this study, we measured the overall level changes of m6A methylation of RNA under H. pylori infection through in vitro and in vivo experiment. Methods: The total quantity of m6A was quantified in gastric tissues of clinical patients and C57 mice with H. pylori infection, as well as acute infection model [H. pylori and GES-1 cells were cocultured for 48 h at a multiplicity of infection (MOI) from of 10:1 to 50:1]. Furthermore, we performed m6A methylation sequencing and RNA-sequencing on the cell model and RNA-sequencing on animal model. Results: Quantitative detection of RNA methylation showed that H. pylori infection group had higher m6A modification level. M6A methylation sequencing identified 2,107 significantly changed m6A methylation peaks, including 1,565 upregulated peaks and 542 downregulated peaks. A total of 2,487 mRNA was upregulated and 1,029 mRNA was downregulated. According to the comprehensive analysis of MeRIP-seq and RNA-seq, we identified 200 hypermethylation and upregulation, 129 hypermethylation but downregulation, 19 hypomethylation and downregulation and 106 hypomethylation but upregulation genes. The GO and KEGG pathway analysis of these differential methylation and regulatory genes revealed a wide range of biological functions. Moreover, combining with mice RNA-seq results, qRT- PCR showed that m6A regulators, METTL3, WTAP, FTO and ALKBH5, has significant difference; Two key genes, PTPN14 and ADAMTS1, had significant difference by qRT- PCR. Conclusion: These findings provide a basis for further investigation of the role of m6A methylation modification in H. pylori-associated gastritis.