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

Effects of RNA methylation on Tumor angiogenesis and cancer progression

Tumor angiogenesis plays vital roles in the growth and metastasis of cancer. RNA methylation is one of the most common modifications and is widely observed in eukaryotes and prokaryotes. Accumulating studies have revealed that RNA methylation affects the occurrence and development of various tumors. In recent years, RNA methylation has been shown to play an important role in regulating tumor angiogenesis. In this review, we mainly elucidate the mechanisms and functions of RNA methylation on angiogenesis and progression in several cancers. We then shed light on the role of RNA methylation-associated factors and pathways in tumor angiogenesis. Finally, we describe the role of RNA methylation as potential biomarker and novel therapeutic target.

WTAP regulates autophagy in colon cancer cells by inhibiting FLNA through N6-methyladenosine

Our study investigated the role of WTAP in colon cancer. We employed experiments including m6A dot blot hybridization, methylated RNA immunoprecipitation, dual-luciferase, and RNA immunoprecipitation to investigate the regulatory mechanism of WTAP. Western blot was performed to analyze the expression of WTAP, FLNA and autophagy-related proteins in cells. Our results confirmed the up-regulation of WTAP in colon cancer and its promoting effect on proliferation and inhibiting effect on apoptosis. FLNA was the downstream gene of WTAP and WTAP-regulated m6A modification led to post-transcriptional repression of FLNA. The rescue experiments showed that WTAP/FLNA could inhibit autophagy. WTAP-mediated m6A modification was confirmed to be crucial in colon cancer development, providing new insights into colon cancer therapy.

Cancer metastasis under the magnifying glass of epigenetics and epitranscriptomics

Most of the cancer-associated mortality and morbidity can be attributed to metastasis. The role of epigenetic and epitranscriptomic alterations in cancer origin and progression has been extensively demonstrated during the last years. Both regulations share similar mechanisms driven by DNA or RNA modifiers, namely writers, readers, and erasers; enzymes responsible of respectively introducing, recognizing, or removing the epigenetic or epitranscriptomic modifications. Epigenetic regulation is achieved by DNA methylation, histone modifications, non-coding RNAs, chromatin accessibility, and enhancer reprogramming. In parallel, regulation at RNA level, named epitranscriptomic, is driven by a wide diversity of chemical modifications in mostly all RNA molecules. These two-layer regulatory mechanisms are finely controlled in normal tissue, and dysregulations are associated with every hallmark of human cancer. In this review, we provide an overview of the current state of knowledge regarding epigenetic and epitranscriptomic alterations governing tumor metastasis, and compare pathways regulated at DNA or RNA levels to shed light on a possible epi-crosstalk in cancer metastasis. A deeper understanding on these mechanisms could have important clinical implications for the prevention of advanced malignancies and the management of the disseminated diseases. Additionally, as these epi-alterations can potentially be reversed by small molecules or inhibitors against epi-modifiers, novel therapeutic alternatives could be envisioned.

METTL3-mediated m6A modification of circRNF220 modulates miR-330-5p/survivin axis to promote osteosarcoma progression

BACKGROUND

Circular RNAs (circRNAs) play a crucial role in regulating various physiological processes. However, the precise regulatory mechanisms of circRNF220s in osteosarcoma (OS) are not well understood.

METHODS

The abundances of circRNF220, miR-330-5p, and survivin were determined using qRT-PCR. To assess the m6A accumulation in circRNF220, a methylated RNA immunoprecipitation (Me-RIP) assay was conducted. Cellular multiplication, motility, and invasion were examined using the cell Counting Kit-8 (CCK-8), EdU, colony formation, Transwell, and wound-healing assays. The binding relationships were measured through RNA immunoprecipitation (RIP) and luciferase reporter assays. In vivo functionality was assessed using xenograft models.

RESULTS

CircRNF220 was identified as being overexpressed in both OS cells and tissues. In vitro experiments demonstrated that silencing circRNF220 impeded the proliferation, invasion, and motility of OS cells. Similarly, in vivo studies confirmed that downregulating circRNF220 inhibited the growth of OS. Further mechanistic investigations unveiled that METTL3-modulated circRNF220 regulated the progression of OS by upregulating survivin expression through acting as a sponge for miR-330-5p.

CONCLUSION

The modulation of METTL3-regulated circRNF220 has been found to promote the progression of OS by modulating the miR-330-5p/survivin axis. This novel finding suggests a potentially unique approach to managing OS.

METTL3/YTHDC1-mediated upregulation of LINC00294 promotes hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is a highly prevalent malignancy and the third highest contributor to cancer-associated deaths globally. Research has increasingly demonstrated a strong correlation between long noncoding RNAs (lncRNAs) and the incidence and progression of HCC. Nonetheless, the exact mechanism whereby the function of lncRNAs in HCC has not been elucidated. This study explored the pathological role of LINC00294 in HCC, as well as the modulatory mechanism involved. Based on the "The Cancer Genome Atlas (TCGA)" database and validation in HCC cell lines and tissues, the expression of LINC00294 was discovered to be upregulated in HCC tissues and correlated with tumor grade and the prognosis of patients with HCC. Functionally, LINC00294 stimulated the proliferation of HCC cells as well as the Warburg effect (aerobic glycolysis) to enhance progression of tumor in vivo. Mechanistically, METTL3/YTHDC1-mediated N6-methyladenosine (m6A) modification underwent a significant enrichment within LINC00294 and was shown to enhance its RNA stability. Moreover, LINC00294 promoted the interaction between YTHDC1 and HK2 and GLUT1 mRNA. Overall, our study illustrates the m6A modification-mediated epigenetic mechanism of LINC00294 expression and regulatory role in HK2and GLUT1 mRNA expression and indicate LINC00294 as a potential biomarker panel for prognostic prediction and treatment in HCC.

Prognostic significance of N6-methyladenosine-modified related chemotransferase METTL3 in gastric carcinoma: Evidence from meta-analysis

BACKGROUND

N6-methyladenosine (m6A) methylation is known as the research hotspot for tumor epimodification, and its associated methyltransferase-like3 (METTL3) is significantly differentially expressed in gastric carcinoma, but its clinical value has not been summarized. This meta-analysis aimed to evaluate the prognostic significance of METTL3 in gastric carcinoma.

MATERIAL AND METHODS

Databases, including PubMed, EMBASE (Ovid platform), Science Direct, Scopus, MEDLINE, Google Scholar, Web of Science, and Cochrane Library, were used to identify relevant eligible studies. The endpoints included overall survival, progression-free survival, recurrence-free survival, post-progression survival, and disease-free survival. Hazard ratios (HR) with 95% confidence intervals (CI) were used to correlate METTL3 expression with prognosis. Subgroup and sensitivity analyses were performed.

RESULTS

Seven eligible studies involving 3034 gastric carcinoma patients were recruited for this meta-analysis. The analysis showed that high METTL3 expression was associated with significantly poorer overall survival (HR  =  2.37, 95% CI 1.66-3.39, P < 0.01) and unfavorable disease-free survival (HR  =  2.58, 95% CI 1.97-3.38, P  < 0.01), as did unfavorable progression-free survival (HR  =  1.48, 95% CI 1.19-1.84, P  < 0.01)/recurrence-free survival (HR  =  2.62, 95% CI 1.93-5.62, P  < 0.01)/post-progression survival (HR  =  1.53, 95% CI 1.22-1.91, P  < 0.01). Subgroup analysis found that high METTL3 expression was associated with worse overall survival in patients with Chinese (HR  =  2.21, 95% CI 1.48-3.29, P  < 0.01), in studies with sample source from formalin-fixed, paraffin-embedded tissues (HR  =  2.66, 95% CI 1.79-3.94, P  < 0.01), and the reported directly from articles group (HR  =  2.42, 95% CI 1.66-3.53, P  < 0.01). The subgroup analysis that was performed based on sample size, detected method, and follow-up showed the same results.

CONCLUSIONS

High expression of METTL3 predicts poor prognosis in gastric carcinoma, indicating promise for METTL3 as a prognostic biomarker.Systematic review registration: https://www.crd.york.ac.uk/prospero, ID = CRD42023408519.

Glucose transporter 3 (GLUT3) promotes lactylation modifications by regulating lactate dehydrogenase A (LDHA) in gastric cancer

OBJECTIVES

Glucose transporter 3 (GLUT3) plays a major role in glycolysis and glucose metabolism in cancer cells. We aimed to investigate the correlation between GLUT3 and histone lactylation modification in the occurrence and progression of gastric cancer.

MATERIALS AND METHODS

We initially used single-cell sequencing data to determine the expression levels of GLUT3 and lactate dehydrogenase A (LDHA) in primary tumor, tumor-adjacent normal, and metastasis tumor tissues. Immunohistochemistry analysis was conducted to measure GLUT3, LDHA, and L-lactyl levels in gastric normal and cancer tissues. Transwell and scratch assays were performed to evaluate the metastatic and invasive capacity of gastric cancer cell lines. Western blotting was used to measure L-lactyl and histone lactylation levels in gastric cancer cell lines.

RESULTS

Single-cell sequencing data showed that GLUT3 expression was significantly increased in primary tumor and metastasis tumor tissues. In addition, GLUT3 expression was positively correlated with that of LDHA expression and lactylation-related pathways. Western blotting and immunohistochemistry analyses revealed that GLUT3 was highly expressed in gastric cancer tissues and cell lines. GLUT3 knockdown in gastric cancer cell lines inhibited their metastatic and invasive capacity to various degrees. Additionally, the levels of LDHA, L-lactyl, H3K9, H3K18, and H3K56 significantly decreased after GLUT3 knockdown, indicating that GLUT3 affects lactylation in gastric cancer cells. Moreover, LDHA overexpression in a GLUT3 knockdown cell line reversed the levels of lactylation and EMT-related markers, and the EMT functional phenotype induced by GLUT3 knockdown. The in vivo results were consistent with the in vitro results.

CONCLUSIONS

This study suggests the important role of histone lactylation in the occurrence and progression of gastric cancer, and GLUT3 may be a new diagnostic marker and therapeutic target for gastric cancer.

AGAP2-AS1 promotes the assembly of m6A methyltransferases and activation of the IL6/STAT3 pathway by binding with WTAP in the carcinogenesis of gastric cancer

Owing to the lack of biomarkers for early diagnosis, gastric cancer (GC) is often associated with a poor prognosis. Thus, there is an urgent need to identify early molecular targets in GC. Dysregulated long noncoding RNAs (lncRNAs) have been evaluated by integrated bioinformatics analysis; and we investigate their specific role and potential mechanism via N6-methyladenosine (m6A) methylation modification in the carcinogenesis and progression of GC. In this study, we report upregulation of lncRNA AGAP2-AS1, activated by a gain of H3K4Me3, in GC tissues and cells. AGAP2-AS1 was linked to adverse prognosis in patients with GC. Functionally, AGAP2-AS1 knockdown inhibited cell proliferation and migration of GC cells. Mechanistically, AGAP2-AS1 bound WT1-associated protein (WTAP) to promote the formation of the WTAP/methyltransferase-like 3 (METTL3)/METTL14 m6A methyltransferase complex. AGAP2-AS1 stabilized signal transducer and activator of transcription 3 (STAT3) mRNA in an m6A-dependent manner and, thus, activated the interleukin 6 (IL6)/STAT3 pathway. Importantly, activation of the AGAP2-AS1/WTAP/STAT3 pathways promoted cell proliferation and migration in GC. Collectively, the present findings revealed a novel regulatory relationship between lncRNA and m6A modification. Furthermore, targeting the AGAP2-AS1/WTAP/STAT3 axis may be a promising strategy for the inhibition of inflammation-mediated carcinogenesis and progression in GC.

METTL9-SLC7A11 axis promotes hepatocellular carcinoma progression through ferroptosis inhibition

Methytransferase-like proteins 9 (METTL9) has been characterized as an oncogene in several cancers, however, its role in hepatocellular carcinoma (HCC) remains unknown. Here, we investigated the function and molecular mechanism of METTL9 in HCC. We showed that METTL9 expression was elevated in HCC, and its high expression was associated with poor survival outcomes. Knockdown of METTL9 observed a significant inhibition of HCC cell viability, migration, and invasion both in vitro and in vivo. By contrast, METTL9 overexpression HCC cells obtained stronger abilities in cell proliferation and migration. Mechanistically, we discovered that METTL9 knockdown led to a reduction in the expression level of SLC7A11, a key suppressor of ferroptosis, in turn, promoted ferroptosis in HCC cells, impeding the progression of HCC. Moreover, we have proved that targeting METTL9 could significantly restrain the growth of HCC patient-derived xenograft (PDX). Our study established METTL9 as a critical role in promoting HCC development and provides a foundation for further investigation and potential therapeutic interventions targeting ferroptosis in HCC.

ALKBH5-mediated CHAC1 depletion promotes malignant progression and decreases cisplatin-induced oxidative stress in gastric cancer

The m6a demethyltransferase ALKBH5 dynamically modulates gene expression and intracellular metabolic molecules by modifying RNA m6a in cancer cells. However, ALKBH5's function in gastric cancer (GC) has remained controversial. This study demonstrates that ALKBH5 is highly expressed in GC. Silencing ALKBH5 hampers proliferation, and metastatic potential, and induces cell death in GC cells. Through a comprehensive analysis of the transcriptome and m6A sequencing, alterations in certain ALKBH5 target genes, including CHAC1, were identified. ALKBH5's demethylation effect regulates CHAC1 RNA stability, leading to reduced CHAC1 expression. Moreover, CHAC1 modulates intracellular ROS levels, influencing the chemotherapy sensitivity of gastric cancer. In summary, our study unveils the pivotal role of the ALKBH5-CHAC1-ROS axis and highlights the significance of m6A methylation in gastric cancer.

METTL3 promotes colorectal cancer progression through activating JAK1/STAT3 signaling pathway

The role of METTL3-mediated N6-methyladenosine (m6A) modification has been elucidated in several cancers, but the concrete mechanism underlying its function in colorectal cancer is still obscure. Here, we revealed that upregulated methyltransferase-like 3 (METTL3) in colorectal cancer exerted both methyltransferase activity-dependent and -independent functions in gene regulation. METTL3 deposited m6A on the 3' untranslated region of the JAK1 transcript to promote JAK1 translation relying on YTHDF1 recognition. Besides, METTL3 was redistributed to the STAT3 promoter and worked in concert with NF-κB to facilitate STAT3 transcription, which was achieved independently on METTL3 methyltransferase activity. The increased JAK1 and STAT3 corporately contributed to the activation of the p-STAT3 signaling pathway and further upregulated downstream effectors expressions, including VEGFA and CCND1, which finally resulted in enhanced cancer cell proliferation and metastasis in vitro and in vivo. Collectively, our study revealed the unappreciated dual role of METTL3 as an m6A writer and a transcription regulator, which worked together in the same signaling pathway to drive colorectal cancer malignancy.

New insights into the regulation of METTL3 and its role in tumors

As one of the most abundant epigenetic modifications in RNA, N6-methyladenosine (m6A) affects RNA transcription, splicing, stability, and posttranscriptional translation. Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, dynamically regulates target genes expression through m6A modification. METTL3 has been found to play a critical role in tumorigenesis, tumor growth, metastasis, metabolic reprogramming, immune cell infiltration, and tumor drug resistance. As a result, the development of targeted drugs against METTL3 is becoming increasingly popular. This review systematically summarizes the factors that regulate METTL3 expression and explores the specific mechanisms by which METTL3 affects multiple tumor biological behaviors. We aim to provide fundamental support for tumor diagnosis and treatment, at the same time, to offer new ideas for the development of tumor-targeting drugs.

Depicting the Profile of METTL3-Mediated lncRNA m6A Modification Variants and Identified SNHG7 as a Prognostic Indicator of MNNG-Induced Gastric Cancer

As a representative example of an environmental chemical carcinogen, MNNG exposure is closely associated with the onset of gastric cancer (GC) where N6-methyladenosine (m6A) RNA methylation tends to be the critical epigenetic event. However, the effect of m6A modification on long non-coding RNAs (lncRNAs) in MNNG-induced GC onset is still unclear. To address the above issue, based on the Methylated RNA immunoprecipitation sequencing (MeRIP-seq) data of MNNG-induced malignant cells (MCs) and GC cells, we comprehensively analyzed the MNNG exposure-associated vital lncRNAs. MeRIP-seq analysis identified 1432 lncRNA transcripts in the MC cell, and 3520 lncRNA transcripts were found to be m6A modified in the GC cell, respectively. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that MNNG exposure could spark cellular localization change, which might be the critical cellular note variation for malignant transformation. We demonstrated that METTL3 is responsible for N6 methylation of lncRNAs and identified SNHG7 as a downstream target of METTL3. More importantly, we observed that SNHG7 was progressively up-regulated during gastric carcinogenesis by MNNG exposure. Finally, we investigated SNHG7 expression in different stages of GC malignancies and found that elevated SNHG7 expression correlated with advanced clinical features and poor prognosis in GC. In conclusion, our study found for the first time that METTL3 regulates the m6A methylation level of lncRNA SNHG7 and its expression in MNNG exposure-induced GC, suggesting that SNHG7 as a predictive biomarker or therapeutic target for GC.

RNA methylation-driven assembly of fluorescence-encoded nanostructures for sensitive detection of m6A modification writer METTL3/14 complex in human breast tissues

N6-methyladenosine (m6A) is an ubiquitous post-transcriptional modification catalyzed by METTL3/14 complex in eukaryotic mRNAs. The abnormal METTL3/14 complex activity affects multiple steps of RNA metabolism and may induce various diseases. Herein, we demonstrate the RNA methylation-driven assembly of fluorescence-encoded nanostructures for sensitive detection of m6A modification writer METTL3/14 complex in human breast tissues. METTL3/14 complex can catalyze the methylation of RNA probe to prevent it from being cleaved by MazF. The intact RNA probe is recognized by the magnetic bead (MB)-capture probe conjugates to induce duplex-specific nuclease (DSN)-assisted cyclic digestion, exposing numerous shorter ssDNAs with 3'-OH end. The shorter ssDNAs on the MB surface can act as the primers to initiate terminal deoxynucleotidyl transferase (TdT)-enhanced tyramide signal amplification (TSA), forming the Cy5 fluorescence-encoded nanostructures. After magnetic separation, the Cy5 fluorescence-encoded nanostructures are digested by DNase I to release abundant Cy5 fluorophores that can be simply quantified by fluorescence measurement. This assay achieves good specificity and high sensitivity with a detection limit of 58.8 aM, and it can screen METTL3/14 complex inhibitors and quantify METTL3/14 complex activity at the single-cell level. Furthermore, this assay can differentiate the METTL3/14 complex level in breast cancer patient tissues and healthy volunteer tissues.

The roles of m6A methylation in cervical cancer: functions, molecular mechanisms, and clinical applications

Cervical cancer (CC) is a gynecological neoplasm with the highest incidence rate, primarily attributed to the persistent infection of high-risk Human papillomavirus (HPV). Despite extensive research, the pathogenesis of CC remains unclear. N6-methyladenosine (m6A) methylation, the most prevalent form of epigenetic modification in RNA, is intricately linked to cell proliferation, metastasis, metabolism, and therapeutic resistance within the tumor microenvironment (TME) of CC. The involvement of the writer, reader, and eraser in m6A modification impacts the advancement of tumors through the regulation of RNA stability, nuclear export, translation efficiency, and RNA degradation. Here, we discuss the biogenesis of m6A, the atypical expressions of m6A regulators, the mechanisms of molecular interactions, and their functions in CC. Furthermore, we elucidate m6A modification of non-coding RNA. In the context of precision medicine, and with the advancements of genomics, proteomics, and high-throughput sequencing technologies, we summarize the application of m6A in the clinical diagnosis and treatment of CC. Additionally, new perspectives on detection methods, immune regulation, and nano-drug development are presented, which lay the foundation for further research of m6A and provide new ideas for the clinical treatment of CC.

DCLRE1B promotes tumor progression and predicts immunotherapy response through METTL3-mediated m6A modification in pancreatic cancer

BACKGROUND

DCLRE1B is a 5'-to-3' exonuclease, which is involved in repairing ICL-related DNA damage. DCLRE1B has been reported to cause poor prognosis in a variety of cancers. Nonetheless, there is no research on DCLRE1B's biological role in pan-cancer datasets. Thus, ascertaining the processes via which DCLRE1B modulates tumorigenesis was the goal of the extensive bioinformatics investigation of pan-cancer datasets in the present research.

METHODS

In our research, employing internet websites and databases including TIMER, GEPIA, TISIDB, Kaplan-Meier Plotter, SangerBox, cBioPortal, and LinkedOmics, DCLRE1B-related data in numerous tumors were extracted. To ascertain the association among DCLRE1B expression, prognosis, genetic changes, and tumor immunity, the pan-cancer datasets were examined. The DCLRE1B's biological roles in pancreatic cancer cells were ascertained by employing wound healing, in vitro CCK-8, and MeRIP-qPCR assays.

RESULT

According to the pan-cancer analysis, in numerous solid tumors, DCLRE1B upregulation was observed. Expression of DCLRE1B was found to be substantially related to the cancer patients' prognoses. Similarly, expression of DCLRE1B exhibited substantial association with immune cells in several cancer types. DCLRE1B expression correlated with immune checkpoint (ICP) gene expression and impacted immunotherapy sensitivity. According to in vitro trials, DCLRE1B promoted PC cells' proliferation and migration capacities. Also, according to GSEA enrichment analysis, DCLRE1B might participate in the JAK-STAT signaling pathway, which was confirmed by western blotting. In addition, we also found that the downregulation of DCLRE1B may be regulated by METTL3-mediated m6A modification.

CONCLUSIONS

In human cancer, the overexpression of DCLRE1B was generally observed, which aided cancer onset and advancement via a variety of processes comprising control of the immune cells' tumor infiltration. According to this study's findings, in a few malignant tumors, DCLRE1B is a candidate immunotherapeutic and prognostic biomarker.

N4-acetylcytidine-dependent GLMP mRNA stabilization by NAT10 promotes head and neck squamous cell carcinoma metastasis and remodels tumor microenvironment through MAPK/ERK signaling pathway

N4-acetylcytidine (ac4C) is a post-transcriptional RNA modification that regulates in various important biological processes. However, its role in human cancer, especially lymph node metastasis, remains largely unknown. Here, we demonstrated N-Acetyltransferase 10 (NAT10), as the only known "writer" of ac4C mRNA modification, was highly expressed in head and neck squamous cell carcinoma (HNSCC) patients with lymph node metastasis. High NAT10 levels in the lymph nodes of patients with HNSCC patients are a predictor of poor overall survival. Moreover, we found that high expression of NAT10 was positively upregulated by Nuclear Respiratory Factor 1 (NRF1) transcription factor. Gain- and loss-of-function experiments displayed that NAT10 promoted cell metastasis in mice. Mechanistically, NAT10 induced ac4C modification of Glycosylated Lysosomal Membrane Protein (GLMP) and stabilized its mRNA, which triggered the activation of the MAPK/ERK signaling pathway. Finally, the NAT10-specific inhibitor, remodelin, could inhibit HNSCC tumorigenesis in a 4-Nitroquinoline 1-oxide (4NQO)-induced murine tumor model and remodel the tumor microenvironment, including angiogenesis, CD8+ T cells and Treg recruitment. These results demonstrate that NAT10 promotes lymph node metastasis in HNSCC via ac4C-dependent stabilization of the GLMP transcript, providing a potential epitranscriptomic-targeted therapeutic strategy for HNSCC.

m6A-modified circNFIX promotes ovarian cancer progression and immune escape via activating IL-6R/JAK1/STAT3 signaling by sponging miR-647

BACKGROUND

Ovarian cancer (OC) is one of the most common gynecological malignant cancers. Our previous work confirmed that circNFIX acted as an oncogene in OC, which could promote malignant proliferation, metastasis and angiogenesis. However, the role and mechanism of circNFIX in OC immune escape remain unclear.

METHODS

The RNA and protein levels were determined by qRT-PCR and western blot assays. The malignant phenotypes were tested by cell count kit-8, EdU staining, flow cytometry and transwell assays. The immune cytokines levels were measured by ELISA analysis. Molecular interactions were verified employing RNA immunoprecipitation, meRIP and dual luciferase methods. In vivo validation was performed by xenograft tumor and lung metastasis model. Hematoxylin & eosin and immunohistochemistry staining were used to observe the pathological changes.

RESULTS

The levels of circNFIX, PD-L1, and IL-6R were upregulated in OC tissues and cell lines, while miR-647 was downregulated. Functional assays showed that loss of circNFIX suppressed the growth, metastasis and immune escape of OC cells both in vitro and in vivo. On the molecular level, the m6A modification of circNFIX was elevated in OC cells, and its expression was positively correlated to m6A modification and depended on IGF2BP1 ∼ 3 recognition. Moreover, circNFIX acted as a competing endogenous RNA for miR-647 to upregulate IL-6R expression, thereby activating JAK/STAT3 signaling and elevating PD-L1 expression. Rescue assays revealed that co-silencing of miR-647 reversed the antitumor effects of circNFIX knockdown on cell proliferation, metastasis and immune escape of OC cells.

CONCLUSION

This study provided a comprehensive understanding of the molecular mechanism about circNFIX in OC, demonstrating m6A activated-circNFIX accelerated OC development and immune escape via regulating miR-647/IL-6R/PD-L1 pathway.

M2 macrophage exosomal LINC01001 promotes non-small cell lung cancer development by affecting METTL3 and glycolysis pathway

There have been data showing that LINC01001 is highly expressed in lung cancer, but the effect of M2 macrophage exosomal LINC01001 to METTL3, glycolysis and immunity in non-small cell lung cancer (NSCLC) has not been reported. In this study, we aimed to explore the regulatory effect and mechanism of M2 macrophage exosomal LINC01001 in NSCLC. The results of our study show that the verification of macrophage exosomes, it was confirmed that exosomes regulated proliferation, glucose intake, lactate production and ATP levels of NSCLC cells. Exosomes also promoted the expression of METTL3. Bioinformatics screening showed that LINC01001 regulated METTL3. Subsequent experiments revealed exosomal LINC01001 influenced the glycolysis processes of NSCLC cells. Through RIP, it was proved that LINC01001 functioned in combination with METTL3. Bioinformatics predicted that NASP was a METTL3-targeted gene. LINC01001 could also regulate NASP methylation. Tumorigenesis in mice also indicated that LINC01001 mediated METTL3 to stimulate the development of tumors. In this study, LINC01001 was successfully verified in the exosomes-derived from M2 macrophages. It was confirmed that LINC01001 could interact with METTL3 and regulate glycolysis process in NSCLC cells. LINC01001 also inhibited T cell proliferation.

The emerging role of m6A modification of non-coding RNA in gastrointestinal cancers: a comprehensive review

Gastrointestinal (GI) cancer is a series of malignant tumors with a high incidence globally. Although approaches for tumor diagnosis and therapy have advanced substantially, the mechanisms underlying the occurrence and progression of GI cancer are still unclear. Increasing evidence supports an important role for N6-methyladenosine (m6A) modification in many biological processes, including cancer-related processes via splicing, export, degradation, and translation of mRNAs. Under distinct cancer contexts, m6A regulators have different expression patterns and can regulate or be regulated by mRNAs and non-coding RNAs, especially long non-coding RNAs. The roles of m6A in cancer development have attracted increasing attention in epigenetics research. In this review, we synthesize progress in our understanding of m6A and its roles in GI cancer, especially esophageal, gastric, and colorectal cancers. Furthermore, we clarify the mechanism by which m6A contributes to GI cancer, providing a basis for the development of diagnostic, prognostic, and therapeutic targets.

IGF2BP2-meidated m6A modification of CSF2 reprograms MSC to promote gastric cancer progression

The interaction between tumor cells and stromal cells within the tumor microenvironment plays a critical role in cancer progression. Mesenchymal stem cells (MSCs) are important tumor stromal cells that exhibit pro-oncogenic activities when reprogrammed by the tumor. However, the precise mechanisms underlying MSC reprogramming in gastric cancer remain not well understood. QRT-PCR, western blot, and immunohistochemistry were used to examine gene and protein expression levels. In vitro and in vivo experiments were conducted to assess the biological functions of gastric cancer cells. RNA-sequencing, RNA immunoprecipitation (RIP), and meRIP assays were performed to investigate underlying molecular mechanisms. We found a significant increase in the expression and N6-methyladenosine (m6A) modification levels of colony-stimulating factor 2 (CSF2) in gastric cancer MSCs. CSF2 gene overexpression induced the reprogramming of normal MSCs into cancer-promoting MSCs, thereby enhancing the proliferation, migration, and drug resistance of gastric cancer cells through the secretion of various pro-inflammatory factors. Additionally, we demonstrated that the m6A reader IGF2BP2 bound to and stabilized CSF2 mRNA in gastric cancer MSCs. Notably, overexpression of IGF2BP2 mimicked the effect of CSF2 on MSCs, promoting gastric cancer progression. Finally, we unveiled that CSF2 induced the ubiquitination of Notch1 to reprogram MSCs. Our study highlights a critical role of IGF2BP2-mediated m6A modification of CSF2 in reprogramming MSCs, which presents a promising therapeutic target for gastric cancer.

A deregulated m6A writer complex axis driven by BRD4 confers an epitranscriptomic vulnerability in combined DNA repair-targeted therapy

Aberrant transcripts expression of the m6A methyltransferase complex (MTC) is widely found across human cancers, suggesting a dysregulated signaling cascade which integrates m6A epitranscriptome to drive tumorigenesis. However, the responsible transcriptional machinery directing the expression of distinct MTC subunits remains unclear. Here, we identified an unappreciated interplay between the histone acetyl-lysine reader BRD4 and the m6A writer complex across human cancers. BRD4 directly stimulates transcripts expression of seven MTC subunits, allowing the maintenance of the nuclear writer complex integrity. Upon BET inhibition, this BRD4-MTC signaling cascade accounts for global m6A reduction and the subsequent dynamic alteration of BRD4-dependent transcriptome, resulting in impaired DNA damage response that involves activation of homologous recombination (HR) repair and repression of apoptosis. We further demonstrated that the combined synergy upon BET/PARP inhibition largely relies on disrupted m6A modification of HR and apoptotic genes, counteracting PARP inhibitor (PARPi) resistance in patient-derived xenograft models. Our study revealed a widespread active cross-talk between BRD4-dependent epigenetic and MTC-mediated epitranscriptomic networks, which provides a unique therapeutic vulnerability that can be leveraged in combined DNA repair-targeted therapy.

IGF2BP2 acts as a m6A modification regulator in laryngeal squamous cell carcinoma through facilitating CDK6 mRNA stabilization

Laryngeal squamous cell carcinoma (LSCC) is one of the most commonly seen cancers in the head and neck region with increasing morbidity and mortality globally. N6-methyladenosine (m6A) modification plays a critical role in the carcinogenesis of LSCC. In this study, two datasets from online database were analyzed for differentially expressed genes (DEGs) between LSCC and normal samples. Furthermore, we carried out a series of experiments, including hematoxylin & eosin staining, immunohistochemical (IHC) staining, CCK-8, colony formation, transwell, flow cytometry, xenograft tumor model assays, actinomycin D assay, cycloheximide (CHX) assay, methylated m6A RNA immunoprecipitation (Me-RIP), RNA immunoprecipitation (RIP) assay, to verify the relevant findings in vivo and in vitro. Insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2) was identified as an up-regulated m6A regulator in LSCC samples. Lower IGF2BP2 expression was linked to higher survival probability in LSCC and other head and neck squamous cell carcinoma patients. In LSCC cells, IGF2BP2 knockdown attenuated cancer cell aggressiveness, possibly through modulating cell cycle arrest. In the xenograft tumor model derived from IGF2BP2 knocked-down LSCC cells, IGF2BP2 knockdown inhibited tumor growth. IGF2BP2 up-regulated CDK6 expression through facilitating the stability of CDK6 mRNA and protein. CDK6 knockdown caused no changes in IGF2BP2 expression, but partially eliminated the promotive effects of IGF2BP2 overexpression on LSCC cells' aggressiveness. Overexpressed IGF2BP2 in LSCC serves as an oncogenic factor, promoting LSCC cell proliferation and invasion in vitro and tumor growth in a xenograft tumor model in vivo through facilitating CDK6 mRNA stabilization.

LncRNA BCAN-AS1 stabilizes c-Myc via N6-methyladenosine-mediated binding with SNIP1 to promote pancreatic cancer

C-Myc overexpression contributes to multiple hallmarks of human cancer but directly targeting c-Myc is challenging. Identification of key factors involved in c-Myc dysregulation is of great significance to develop potential indirect targets for c-Myc. Herein, a collection of long non-coding RNAs (lncRNAs) interacted with c-Myc is detected in pancreatic ductal adenocarcinoma (PDAC) cells. Among them, lncRNA BCAN-AS1 is identified as the one with highest c-Myc binding enrichment. BCAN-AS1 was abnormally elevated in PDAC tumors and high BCAN-AS1 level was significantly associated with poor prognosis. Mechanistically, Smad nuclear-interacting protein 1 (SNIP1) was characterized as a new N6-methyladenosine (m6A) mediator binding to BCAN-AS1 via recognizing its m6A modification. m6A-modified BCAN-AS1 acts as a scaffold to facilitate the formation of a ternary complex together with c-Myc and SNIP1, thereby blocking S phase kinase-associated protein 2 (SKP2)-mediated c-Myc ubiquitination and degradation. Biologically, BCAN-AS1 promotes malignant phenotypes of PDAC in vitro and in vivo. Treatment of metastasis xenograft and patient-derived xenograft mouse models with in vivo-optimized antisense oligonucleotide of BCAN-AS1 effectively represses tumor growth and metastasis. These findings shed light on the pro-tumorigenic role of BCAN-AS1 and provide an innovant insight into c-Myc-interacted lncRNA in PDAC.

RNA methylation, homologous recombination repair and therapeutic resistance

Homologous recombination (HR) repair of DNA double-strand breaks (DSBs) is critical for maintaining genomic integrity and stability. Defects in HR increase the risk of tumorigenesis. However, many human tumors exhibit enhanced HR repair capabilities, consequently endowing tumor cells with resistance to DNA-damaging chemotherapy and radiotherapy. This review summarizes the role of RNA methylation in HR repair and therapeutic resistance in human tumors. We also analyzed the interactions between RNA methylation and other HR-modulating modifications including histone acetylation, histone deacetylation, ubiquitination, deubiquitination, protein arginine methylation, and gene transcription. This review proposes that targeting RNA methylation is a promising approach to overcoming HR-mediated therapeutic resistance.

IGF2BP2 promotes ovarian cancer growth and metastasis by upregulating CKAP2L protein expression in an m6 A-dependent manner

Ovarian cancer (OC) is the second leading cause of gynecological cancer-related death in women worldwide. N6-methyladenosine (m6 A) is the most abundant internal modification in eukaryotic RNA. Human insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), an m6 A reader, can enhance mRNA stability and promote translation by recognizing m6 A modifications. Its tumor-promoting effects have been demonstrated in several cancers. However, the roles of m6 A modification and IGF2BP2 in OC remain unclear. Here, by using methylated RNA immunoprecipitation sequencing, we demonstrated that there is widespread dysregulation of m6 A modification in OC tissues. The m6 A modification and the mRNA and protein levels of IGF2BP2 were significantly elevated in OC. Overexpression of IGF2BP2 facilitated OC cell proliferation, migration, and invasion in vitro and accelerated tumor growth and metastasis in vivo. While IGF2BP2-knockdown showed the opposite effect. Mechanistically, we identified cytoskeleton-associated protein 2-like (CKAP2L) as a target of IGF2BP2. IGF2BP2 promoted CKAP2L translation dependent on m6 A modification, rather than affecting mRNA and protein stability. Overexpression of CKAP2L rescued the tumor-suppressive effect of IGF2BP2 knockdown in OC cells. In conclusion, this study revealed the potential role of IGF2BP2 in tumor progression, at least partially via promoting the translation of CKAP2L in an m6 A-dependent manner.

METTL3 promotes drug resistance to oxaliplatin in gastric cancer cells through DNA repair pathway

Gastric cancer (GC) poses a significant threat to human health and remains a prevalent form of cancer. Despite clinical treatments, the prognosis for Gastric cancer patients is still unsatisfactory, largely due to the development of multidrug resistance. Oxaliplatin (OXA), a second-generation platinum drug, is commonly recommended for adjuvant and palliative chemotherapy in Gastric cancer; however, the underlying mechanisms of acquired resistance to Oxaliplatin in Gastric cancer patients are not yet fully understood. In this study, we aimed to explore the potential mechanisms of Oxaliplatin resistance in Gastric cancer by employing bioinformatics analysis and conducting in vitro experiments. Specifically, we focused on investigating the role of methyltransferase-like 3 (METTL3). Our findings revealed that the knockdown of METTL3 significantly impeded the proliferation and migration of Gastric cancer cells. METTL3 knockdown induced apoptosis in OXA-resistant Gastric cancer cells and enhanced their sensitivity to Oxaliplatin. Furthermore, we found that DNA repair pathways were significantly activated in OXA-resistant Gastric cancer cells, and METTL3 knockdown significantly inhibited DNA repair pathways. Another important finding is that METTL3 knockdown and OXA-induced Gastric cancer cell death are additive, and the targeted METTL3 can assist Oxaliplatin treatment. Collectively, our findings suggest that METTL3 knockdown can augment the sensitivity of Gastric cancer cells to Oxaliplatin by impeding DNA repair processes. Consequently, targeting METTL3 holds great promise as a viable adjuvant strategy in the treatment of Gastric cancer patients.

LncRNA CCAT1 facilitates the progression of gastric cancer via PTBP1-mediated glycolysis enhancement

BACKGROUND

Gastric cancer (GC) is one of the most prevalent malignant tumors of the digestive system. As a hallmark of cancer, energy-related metabolic reprogramming is manipulated by multiple factors, including long non-coding RNAs (lncRNAs). Notably, lncRNA CCAT1 has been identified as a crucial regulator in tumor progression. Nevertheless, the precise molecular mechanisms underlying the involvement of CCAT1 in metabolic reprogramming of GC remain unclear.

METHODS

Gain- and loss-of-function experiments were performed to evaluate the roles of CCAT1 in tumorigenesis and glycolysis of GC. Bioinformatics analyses and mechanistic experiments, such as mass spectrometry (MS), RNA-pulldown, and RNA immunoprecipitation (RIP), were employed to reveal the potential interacting protein of CCAT1 and elucidate the regulatory mechanism of CCAT1 in GC glycolysis. Moreover, the nude mice xenograft assay was used to evaluate the effect of CCAT1 on GC cells in vivo.

RESULTS

In this study, we identified that CCAT1 expression was significantly elevated in the tissues and plasma exosomes of GC patients, as well as GC cell lines. Functional experiments showed that the knockdown of CCAT1 resulted in a substantial decrease in the proliferation, migration and invasion of GC cells both in vitro and in vivo through decreasing the expression of glycolytic enzymes and glycolytic rate. Conversely, overexpression of CCAT1 exhibited contrasting effects. Mechanistically, CCAT1 interacted with PTBP1 and effectively maintained its stability by inhibiting the ubiquitin-mediated degradation process. As a critical splicing factor, PTBP1 facilitated the transition from PKM1 to PKM2, thereby augmenting the glycolytic activity of GC cells and ultimately fostering the progression of GC.

CONCLUSIONS

Our findings demonstrate that CCAT1 plays a significant role in promoting the proliferation, migration, and invasion of GC cells through the PTBP1/PKM2/glycolysis pathway, thus suggesting CCAT1's potential as a biomarker and therapeutic target for GC.

Interaction between N6-methyladenosine modification and the tumor microenvironment in colorectal cancer

The incidence and mortality of colorectal cancer (CRC) are rapidly increasing worldwide. Recently, there has been significant attention given to N6-methyladenosine (m6A), the most common mRNA modification, especially for its effects on CRC development. It is important to note that the progression of CRC would be greatly hindered without the tumor microenvironment (TME). The interaction between CRC cells and their surroundings can activate and influence complex signaling mechanisms of epigenetic changes to affect the survival of tumor cells with a malignant phenotype. Additionally, the TME is influenced by m6A regulatory factors, impacting the progression and prognosis of CRC. In this review, we describe the interactions and specific mechanisms between m6A modification and the metabolic, hypoxia, inflammatory, and immune microenvironments of CRC. Furthermore, we summarize the therapeutic role that m6A modification can play in the CRC microenvironment, and discuss the current status, limitations, and potential future directions in this field. This review aims to provide new insights into the molecular targets and theoretical foundations for the treatment of CRC.

N6-Methyladenosine Modifications in Pulmonary Hypertension

BACKGROUND

The most prevalent kind of RNA methylation modification existing in eukaryotes is N6-methyladenosine (m6A), which is a reversible type of posttranscriptional modification.

SUMMARY

Many studies have reported that m6A participates in cell differentiation, self-renewal, invasion, and apoptosis by modifying protein synthesis. Furthermore, m6A modification is also involved in disease progression and pulmonary vascular remodeling in pulmonary hypertension. However, very few researchers have investigated the effect of m6A modifications on pulmonary hypertension.

KEY MESSAGES

Here, we have reviewed the latest research advances in the field of m6A RNA methylation in pulmonary hypertension and explored its regulatory role in pulmonary hypertension development and progression.

Alternative polyadenylation reprogramming of MORC2 induced by NUDT21 loss promotes KIRC carcinogenesis

Alternative polyadenylation (APA), a posttranscriptional mechanism of gene expression via determination of 3'UTR length, has an emerging role in carcinogenesis. Although abundant APA reprogramming is found in kidney renal clear cell carcinoma (KIRC), which is one of the major malignancies, whether APA functions in KIRC remains unknown. Herein, we found that chromatin modifier MORC2 gained oncogenic potential in KIRC among the genes with APA reprogramming, and moreover, its oncogenic potential was enhanced by 3'UTR shortening through stabilization of MORC2 mRNA. MORC2 was found to function in KIRC by downregulating tumor suppressor DAPK1 via DNA methylation. Mechanistically, MORC2 recruited DNMT3A to facilitate hypermethylation of the DAPK1 promoter, which was strengthened by 3'UTR shortening of MORC2. Furthermore, loss of APA regulator NUDT21, which was induced by DNMT3B-mediated promoter methylation, was identified as responsible for 3'UTR shortening of MORC2 in KIRC. Additionally, NUDT21 was confirmed to act as a tumor suppressor mainly depending on downregulation of MORC2. Finally, we designed an antisense oligonucleotide (ASO) to enhance NUDT21 expression and validated its antitumor effect in vivo and in vitro. This study uncovers the DNMT3B/NUDT21/APA/MORC2/DAPK1 regulatory axis in KIRC, disclosing the role of APA in KIRC and the crosstalk between DNA methylation and APA.

Regulation of m6A modification on ferroptosis and its potential significance in radiosensitization

Radiotherapy is often used to treat various types of cancers, but radioresistance greatly limits the clinical efficiency. Recent studies have shown that radiotherapy can lead to ferroptotic cancer cell deaths. Ferroptosis is a new type of programmed cell death caused by excessive lipid peroxidation. The induction of ferroptosis provides a potential therapeutic strategy for radioresistance. As the most common post-transcriptional modification of mRNA, m6A methylation is widely involved in the regulation of various physiopathological processes by regulating RNA function. Dynamic m6A modification controlled by m6A regulatory factors also affects the susceptibility of cells to ferroptosis, thereby determining the radiosensitivity of tumor cells to radiotherapy. In this review, we summarize the mechanism and significance of radiotherapy induced ferroptosis, analyze the regulatory characteristics of m6A modification on ferroptosis, and discuss the possibility of radiosensitization by enhancing m6A-mediated ferroptosis. Clarifying the regulation of m6A modification on ferroptosis and its significance in the response of tumor cells to radiotherapy will help us identify novel targets to improve the efficacy of radiotherapy and reduce or overcome radioresistance.

Circular RNA circ_KIAA1429 accelerates hepatocellular carcinoma progression via the miR-133a-3p/high mobility group AT-hook 2 (HMGA2) axis in an m6A-dependent manner

Hepatocellular carcinoma (HCC) is the most common primary liver cancer worldwide with high mortality rate, and the N6-methyladenosine (m6A) epigenetic modifications have been reported to be closely associated with the pathogenesis of HCC, but the detailed molecular mechanisms by which m6A regulates HCC progression have not been fully delineated. In this study, we evidenced that the m6A methyltransferase-like 3 (METTL3)-mediated m6A modification contributed to HCC aggressiveness through modulating a novel circ_KIAA1429/miR-133a-3p/HMGA2 axis. Specifically, circ_KIAA1429 was aberrantly overexpressed in HCC tissues and cells, and the expression levels of circ_KIAA1429 was positively regulated by METTL3 in HCC cells in a m6A-dependent manner. Then, functional experiments confirmed that deletion of both circ_KIAA1429 and METTL3 suppressed HCC cell proliferation, migration and cell mitosis in vitro and in vivo, and conversely, circ_KIAA1429 overexpression had opposite effects to accelerate HCC development. Furthermore, the downstream mechanisms by which circ_KIAA1429 regulated HCC progression were uncovered, and we validated that silencing of circ_KIAA1429 restrained the malignant phenotypes in HCC cells through modulating the miR-133a-3p/high mobility group AT-hook 2 (HMGA2) axis. To summarize, our study firstly investigated the involvement of a novel METTL3/m6A/circ_KIAA1429/miR-133a-3p/HMGA2 axis in regulating HCC development, which provided novel indicators for HCC diagnosis, therapy and prognosis.

Decreased acetylation of HDGF improves oviduct production in Rana dybowskii, Rana amurensis, and Rana huanrenensis

The oviduct of female Rana dybowskii is a functional food and can be used as a component of Traditional Chinese medicine. The differentially expressed genes enriched was screened in cell growth of three Rana species. We quantitatively analyzed 4549 proteins using proteomic techniques, enriching the differentially expressed proteins of Rana for growth and signal transduction. The results showed that log2 expression of hepatoma-derived growth factor (HDGF) was increased. We further verified 5 specific differential genes (EIF4a, EIF4g, HDGF1, HDGF2 and SF1) and found that HDGF expression was increased in Rana dybowskii. Through acetylation modification analysis, we identified 1534 acetylation modification sites in 603 proteins, including HDGF, and found that HDGF acetylation expression was significantly reduced in Rana dybowskii. Our results suggest that HDGF is involved in the development of oviductus ranae, which is regulated by acetylation modification.

METTL14‑mediated RNA methylation in digestive system tumors

N6‑methyladenosine (m6A) RNA methylation is one of the most common post‑transcriptional modification mechanism in eukaryotes. m6A is involved in almost all stages of the mRNA life cycle, specifically regulating its stability, splicing, export and translation. Methyltransferase‑like 14 (METTL14) is a particularly important m6A methylation 'writer' that can recognize RNA substrates. METTL14 has been documented to improve the activity and catalytic efficiency of METTL3. However, as individual proteins they can also regulate different biological processes. Malignancies in the digestive system are some of the most common malignancies found in humans, which are typically associated with poor prognoses with limited clinical solutions. METTL14‑mediated methylation has been implicated in both the potentiation and inhibition of digestive system tumor growth, cell invasion and metastasis, in addition to drug resistance. In the present review, the research progress and regulatory mechanisms of METTL14‑mediated methylation in digestive system malignancies were summarized. In addition, future research directions and the potential for its clinical application were examined.

Insights into the role of N6-methyladenosine in ferroptosis

N6-methyladenosine (m6A) methylation modification is one of the most prevalent epigenetic modifications of eukaryotic RNA. m6A methylation is widely associated with many biological processes through the modification of RNA metabolism and is associated with multiple disease states. As a newly discovered regulatory cell death in recent years, ferroptosis is an iron-dependent cell death characterized by excessive lipid peroxidation. Emerging evidence supports that ferroptosis has a significant role in the progression of diverse diseases. Besides, the key regulators of ferroptosis exhibit aberrant m6A levels under different pathological conditions. However, the correlation between m6A-modified ferroptosis and multiple diseases has not been well elucidated. In this review, we summarized the functions of m6A in ferroptosis, which are associated with the initiation and progression of multiple diseases. Investigating the role of m6A in ferroptosis might both facilitate a better understanding of the pathogenesis of these diseases and provide new opportunities for targeted treatment.

Intron retention decreases METTL3 expression by inhibiting mRNA export to the cytoplasm

Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, regulates the splicing, nuclear transport, stability, and translation of its target genes. However, the mechanism underlying the regulation of METTL3 expression by alternative splicing (AS) remains unknown. We analyzed the expression pattern of METTL3 after AS in human tissues and confirmed the expression of an isoform retaining introns 8 and 9 (METTL3-IR). We confirmed the different intracellular localizations of METTL3-IR and METTL3 proteins using immunofluorescence microscopy. Furthermore, the endogenous expression of METTL3-IR at the protein level was different from that at the mRNA level. We found that 3'-UTR generation by intron retention (IR) inhibited the export of METTL3-IR mRNA to the cytoplasm, which in turn suppressed protein expression. To the best of our knowledge, this is the first study to confirm the regulation of METTL3 gene expression by AS, providing evidence that the suppression of METTL3 protein expression by IR is an integral part of the mechanism by which 3'-UTR generation regulates protein expression via inhibition of RNA export to the cytoplasm. [BMB Reports 2023; 56(9): 514-519].

Intron retention decreases METTL3 expression by inhibiting mRNA export to the cytoplasm

Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, regulates the splicing, nuclear transport, stability, and translation of its target genes. However, the mechanism underlying the regulation of METTL3 expression by alternative splicing (AS) remains unknown. We analyzed the expression pattern of METTL3 after AS in human tissues and confirmed the expression of an isoform retaining introns 8 and 9 (METTL3-IR). We confirmed the different intracellular localizations of METTL3-IR and METTL3 proteins using immunofluorescence microscopy. Furthermore, the endogenous expression of METTL3-IR at the protein level was different from that at the mRNA level. We found that 3'-UTR generation by intron retention (IR) inhibited the export of METTL3-IR mRNA to the cytoplasm, which in turn suppressed protein expression. To the best of our knowledge, this is the first study to confirm the regulation of METTL3 gene expression by AS, providing evidence that the suppression of METTL3 protein expression by IR is an integral part of the mechanism by which 3'-UTR generation regulates protein expression via inhibition of RNA export to the cytoplasm. [BMB Reports 2023; 56(9): 514-519].

miR-33a-3p regulates METTL3-mediated AREG stability and alters EMT to inhibit pancreatic cancer invasion and metastasis

Recent studies have shown that amphoteric regulatory protein (AREG), a member of the epidermal growth factor (EGF) family, is expressed in many cancers and is an independent prognostic indicator for patients with pancreatic cancer, but whether AREG is regulated at the epigenetic level to promote the development of pancreatic cancer (PC) has not been elucidated. Our results support the notion that AREG is overexpressed in pancreatic cancer tissues and cell lines. Functionally, the deletion of AREG impedes pancreatic cancer (PC) cell proliferation, migration, and invasion. In addition, we identified and validated that methyltransferase-like 3 (METTL3) induced the m6A modification on AREG and facilitated the stability of AREG mRNA after sequencing. Additionally, we obtained experimental evidence that miR-33a-3p targets and inhibits METTL3 from taking action, as predicted by using the miRDB and RNAinter. Remediation experiments showed that miR-33a-3p inhibits PC progression through METTL3. In summary, this research reveals that miR-33a-3p inhibits m6A-induced stabilization of AREG by targeting METTL3, which plays a key role in the aggressive progression of PC. AREG could be a potential target for PC treatment.

m6A-regulated tumor glycolysis: new advances in epigenetics and metabolism

Glycolytic reprogramming is one of the most important features of cancer and plays an integral role in the progression of cancer. In cancer cells, changes in glucose metabolism meet the needs of self-proliferation, angiogenesis and lymphangiogenesis, metastasis, and also affect the immune escape, prognosis evaluation and therapeutic effect of cancer. The n6-methyladenosine (m6A) modification of RNA is widespread in eukaryotic cells. Dynamic and reversible m6A modifications are widely involved in the regulation of cancer stem cell renewal and differentiation, tumor therapy resistance, tumor microenvironment, tumor immune escape, and tumor metabolism. Lately, more and more evidences show that m6A modification can affect the glycolysis process of tumors in a variety of ways to regulate the biological behavior of tumors. In this review, we discussed the role of glycolysis in tumor genesis and development, and elaborated in detail the profound impact of m6A modification on different tumor by regulating glycolysis. We believe that m6A modified glycolysis has great significance and potential for tumor treatment.

Methyltransferase-like proteins in cancer biology and potential therapeutic targeting

RNA modification has recently become a significant process of gene regulation, and the methyltransferase-like (METTL) family of proteins plays a critical role in RNA modification, methylating various types of RNAs, including mRNA, tRNA, microRNA, rRNA, and mitochondrial RNAs. METTL proteins consist of a unique seven-beta-strand domain, which binds to the methyl donor SAM to catalyze methyl transfer. The most typical family member METTL3/METTL14 forms a methyltransferase complex involved in N6-methyladenosine (m6A) modification of RNA, regulating tumor proliferation, metastasis and invasion, immunotherapy resistance, and metabolic reprogramming of tumor cells. METTL1, METTL4, METTL5, and METTL16 have also been recently identified to have some regulatory ability in tumorigenesis, and the rest of the METTL family members rely on their methyltransferase activity for methylation of different nucleotides, proteins, and small molecules, which regulate translation and affect processes such as cell differentiation and development. Herein, we summarize the literature on METTLs in the last three years to elucidate their roles in human cancers and provide a theoretical basis for their future use as potential therapeutic targets.

The roles and implications of RNA m6A modification in cancer

N6-Methyladenosine (m6A), the most prevalent internal modification in eukaryotic mRNA, has been extensively and increasingly studied over the past decade. Dysregulation of RNA m6A modification and its associated machinery, including writers, erasers and readers, is frequently observed in various cancer types, and the dysregulation profiles might serve as diagnostic, prognostic and/or predictive biomarkers. Dysregulated m6A modifiers have been shown to function as oncoproteins or tumour suppressors with essential roles in cancer initiation, progression, metastasis, metabolism, therapy resistance and immune evasion as well as in cancer stem cell self-renewal and the tumour microenvironment, highlighting the therapeutic potential of targeting the dysregulated m6A machinery for cancer treatment. In this Review, we discuss the mechanisms by which m6A modifiers determine the fate of target RNAs and thereby influence protein expression, molecular pathways and cell phenotypes. We also describe the state-of-the-art methodologies for mapping global m6A epitranscriptomes in cancer. We further summarize discoveries regarding the dysregulation of m6A modifiers and modifications in cancer, their pathological roles, and the underlying molecular mechanisms. Finally, we discuss m6A-related prognostic and predictive molecular biomarkers in cancer as well as the development of small-molecule inhibitors targeting oncogenic m6A modifiers and their activity in preclinical models.

WTAP activates MAPK signaling through m6A methylation in VEGFA mRNA-mediated by YTHDC1 to promote colorectal cancer development

N6-methyladenosine modification, especially Wilms tumor 1-associated protein (WTAP), is reportedly associated with a variety of cancers, including colorectal cancer (CRC). Angiogenesis also plays an important role in the occurrence and development of CRC. However, only a few studies have reported the biological mechanisms underlying this connection. Therefore, tissue microarray and public database were used to explore WTAP levels in CRC. Then, WTAP was down-regulated and over-expressed, respectively. CCK8, EdU, colony formation, and transwell experiments were performed to study the role of WTAP in CRC. Combined RNA sequencing and m6A RNA immunoprecipitation (MeRIP) sequencing, we found downstream molecules VEGFA. Moreover, a tube formation assay was executed for tumor angiogenesis. Finally, a subcutaneous tumorigenesis assay in nude mice was used to examine the tumor-promoting effect of WTAP in vivo. In the present study, WTAP was significantly upregulated in CRC cells and patients with CRC. Moreover, higher WTAP expression was observed in the TCGA and CPATC databases in CRC tissues. WTAP over-expression exacerbates cell proliferation, migration, invasion, and angiogenesis. Conversely, WTAP knockdown inhibited the malignant biological behavior of CRC cells. Mechanistically, WTAP positively regulated VEGFA, as identified using RNA sequencing and MeRIP sequencing. Moreover, we identified YTHDC1 as a downstream effector of the YTHDC1-VEGFA axis in CRC. Furthermore, increased WTAP expression activated the MAPK signaling pathway, which led to enhanced angiogenesis. In conclusion, our study revealed that the WTAP/YTHDC1/VEGFA axis promotes CRC development, especially angiogenesis, suggesting that it may act as a potential biomarker of CRC.

Tackling FGFR3-driven bladder cancer with a promising synergistic FGFR/HDAC targeted therapy

Bladder cancer (BC) is one of the most prevalent malignancies worldwide and FGFR3 alterations are particularly common in BC. Despite approval of erdafitinib, durable responses for FGFR inhibitors are still uncommon and most patients relapse to metastatic disease. Given the necessity to discover more efficient therapies for BC, herein, we sought to explore promising synergistic combinations for BC with FGFR3 fusions. Our studies confirmed the synergy between FGFR and HDAC inhibitors in vitro and demonstrated its benefits in vivo. Mechanistic studies revealed that quisinostat can downregulate FGFR3 expression by suppressing FGFR3 translation. Additionally, quisinostat can also sensitize BC cells to erdafitinib by downregulating HDGF. Furthermore, the synergy was also confirmed in BC cells with FGFR3 S249C. This study discovers a new avenue for treatment of FGFR3-driven BC and uncovers new mechanistic insights. These preclinical studies pave the way for a direct translation of this combination to early phase clinical trials.

BICC1 drives pancreatic cancer progression by inducing VEGF-independent angiogenesis

VEGF inhibitors are one of the most successful antiangiogenic drugs in the treatment of many solid tumors. Nevertheless, pancreatic adenocarcinoma (PAAD) cells can reinstate tumor angiogenesis via activation of VEGF-independent pathways, thereby conferring resistance to VEGF inhibitors. Bioinformatic analysis showed that BICC1 was one of the top genes involved in the specific angiogenesis process of PAAD. The analysis of our own cohort confirmed that BICC1 was overexpressed in human PAAD tissues and was correlated to increased microvessel density and tumor growth, and worse prognosis. In cells and mice with xenograft tumors, BICC1 facilitated angiogenesis in pancreatic cancer in a VEGF-independent manner. Mechanistically, as an RNA binding protein, BICC1 bounds to the 3'UTR of Lipocalin-2 (LCN2) mRNA and post-transcriptionally up-regulated LCN2 expression in PAAD cells. When its level is elevated, LCN2 binds to its receptor 24p3R, which directly phosphorylates JAK2 and activates JAK2/STAT3 signal, leading to increased production of an angiogenic factor CXCL1. Blocking of the BICC1/LCN2 signalling reduced the microvessel density and tumor volume of PAAD cell grafts in mice, and increased the tumor suppressive effect of gemcitabine. In conclusion, BICC1 plays a pivotal role in the process of VEGF-independent angiogenesis in pancreatic cancer, leading to resistance to VEGF inhibitors. BICC1/LCN2 signaling may serve as a promising anti-angiogenic therapeutic target for pancreatic cancer patients.

Role of N6-methyladenosine RNA modification in gastric cancer

N6-methyladenosine (m6A) RNA methylation is the most prevalent internal modification of mammalian messenger RNA. The m6A modification affects multiple aspects of RNA metabolism, including processing, splicing, export, stability, and translation through the reversible regulation of methyltransferases (Writers), demethylases (Erasers), and recognition binding proteins (Readers). Accumulating evidence indicates that altered m6A levels are associated with a variety of human cancers. Recently, dysregulation of m6A methylation was shown to be involved in the occurrence and development of gastric cancer (GC) through various pathways. Thus, elucidating the relationship between m6A and the pathogenesis of GC has important clinical implications for the diagnosis, treatment, and prognosis of GC patients. In this review, we evaluate the potential role and clinical significance of m6A-related proteins which function in GC in an m6A-dependent manner. We discuss current issues regarding m6A-targeted inhibition of GC, explore new methods for GC diagnosis and prognosis, consider new targets for GC treatment, and provide a reasonable outlook for the future of GC research.

Crosstalk between m6A and coding/non-coding RNA in cancer and detection methods of m6A modification residues

N6-methyladenosine (m6A) is one of the most common and well-known internal RNA modifications that occur on mRNAs or ncRNAs. It affects various aspects of RNA metabolism, including splicing, stability, translocation, and translation. An abundance of evidence demonstrates that m6A plays a crucial role in various pathological and biological processes, especially in tumorigenesis and tumor progression. In this article, we introduce the potential functions of m6A regulators, including "writers" that install m6A marks, "erasers" that demethylate m6A, and "readers" that determine the fate of m6A-modified targets. We have conducted a review on the molecular functions of m6A, focusing on both coding and noncoding RNAs. Additionally, we have compiled an overview of the effects noncoding RNAs have on m6A regulators and explored the dual roles of m6A in the development and advancement of cancer. Our review also includes a detailed summary of the most advanced databases for m6A, state-of-the-art experimental and sequencing detection methods, and machine learning-based computational predictors for identifying m6A sites.

Novel insight into RNA modifications in tumor immunity: Promising targets to prevent tumor immune escape

An immunosuppressive state is a typical feature of the tumor microenvironment. Despite the dramatic success of immune checkpoint inhibitor (ICI) therapy in preventing tumor cell escape from immune surveillance, primary and acquired resistance have limited its clinical use. Notably, recent clinical trials have shown that epigenetic drugs can significantly improve the outcome of ICI therapy in various cancers, indicating the importance of epigenetic modifications in immune regulation of tumors. Recently, RNA modifications (N⁶-methyladenosine [m⁶A], N¹-methyladenosine [m¹A], 5-methylcytosine [m⁵C], etc.), novel hotspot areas of epigenetic research, have been shown to play crucial roles in protumor and antitumor immunity. In this review, we provide a comprehensive understanding of how m⁶A, m¹A, and m⁵C function in tumor immunity by directly regulating different immune cells as well as indirectly regulating tumor cells through different mechanisms, including modulating the expression of immune checkpoints, inducing metabolic reprogramming, and affecting the secretion of immune-related factors. Finally, we discuss the current status of strategies targeting RNA modifications to prevent tumor immune escape, highlighting their potential.

Advances in targeting RNA modifications for anticancer therapy

Numerous strategies are employed by cancer cells to control gene expression and facilitate tumorigenesis. In the study of epitranscriptomics, a diverse set of modifications to RNA represent a new player of gene regulation in disease and in development. N6-methyladenosine (m6A) is the most common modification on mammalian messenger RNA and tends to be aberrantly placed in cancer. Recognized by a series of reader proteins that dictate the fate of the RNA, m6A-modified RNA could promote tumorigenesis by driving protumor gene expression signatures and altering the immunologic response to tumors. Preclinical evidence suggests m6A writer, reader, and eraser proteins are attractive therapeutic targets. First-in-human studies are currently testing small molecule inhibition against the methyltransferase-like 3 (METTL3)/methyltransferase-like 14 (METTL14) methyltransferase complex. Additional modifications to RNA are adopted by cancers to drive tumor development and are under investigation.

METTL3 promotes colorectal cancer metastasis by promoting the maturation of pri-microRNA-196b

PURPOSE

Methyltransferase-like 3 (METTL3), a key member of the m6A methyltransferase complex, is upregulated in multiple human malignancies and plays a role in regulating tumor migration. This study aimed to reveal the underlying mechanism by which METTL3 in regulates the metastasis of colorectal cancer (CRC).

METHODS

We compared METTL3 expression levels in CRC tumor tissues and adjacent nontumor tissues by immunohistochemistry (IHC). The functional roles of METTL3 in CRC were assessed by real-time cell migration assays, wound-healing assays and Transwell assays. miRNA sequencing (miRNA-seq), RNA-binding protein immunoprecipitation (RIP) assays and N6-methyladenosine immunoprecipitation (MeRIP) assays were performed to confirm the molecular mechanism underlying the involvement of METTL3 in CRC cell metastasis.

RESULTS

We found that METTL3 was overexpressed in CRC tissues. METTL3 knockdown significantly inhibited CRC cell migration and invasion, while METTL3 overexpression had the opposite effects. Furthermore, we demonstrated that METTL3 regulates miR-196b expression via an N6-methyladenosine (m6A)-pri-miR-196b-dependent mechanism and thereby promotes CRC metastasis.

CONCLUSION

This study shows the important role of METTL3 in CRC metastasis and provides novel insight into m6A modification in CRC metastasis.