METTL3‑mediated m6A modification of Bcl‑2 mRNA promotes non‑small cell lung cancer progression

COL1A1, mediated by m6A methylation of METTL3, facilitates oral squamous cell carcinoma cell growth and metastasis

Collagen type I alpha1 (COL1A1) has been found to be abnormal expressed in oral squamous cell carcinoma (OSCC) tissues, but its role and mechanism in OSCC need to be further elucidated. The expression levels of COL1A1 and methyltransferase-like 3 (METTL3) were measured by quantitative real-time PCR and western blot. Cell growth and metastasis were determined by CCK8, colony formation, EdU, flow cytometry and transwell assays. MeRIP, Co-IP and dual-luciferase reporter assays were performed to explore the interplay of COL1A1 and METTL3. COL1A1 mRNA stability was confirmed by Actinomycin D assay. Mice xenograft models were constructed to perform in vivo experiments. COL1A1 and METTL3 were upregulated in OSCC. COL1A1 knockdown suppressed OSCC cell growth and metastasis, while its overexpression had an opposite effect. The stability of COL1A1 mRNA was regulated by the m6A methylation of METTL3. METTL3 overexpression promoted OSCC cell growth and metastasis, and its knockdown-mediated OSCC cell function inhibition could be abolished by COL1A1 overexpression. Besides, silencing of METTL3 reduced OSCC tumor growth by reducing COL1A1 expression. METTL3-stabilized COL1A1 promoted OSCC progression, providing an exact molecular target for the treatment of OSCC.

METTL3's role in cervical cancer development through m6A modification

N6-methylated adenosine (m6A) is a crucial RNA modification in eukaryotes, particularly in cancer. However, its role in cervical cancer (CC) is unclear. We aimed to elucidate the part of m6A in CC by analyzing methyltransferase-like 3 (METTL3) expression, identifying downstream targets, and exploring the underlying mechanism. We assessed METTL3 expression in CC using western blotting, quantitative polymerase chain reaction (qPCR), and immunohistochemistry. In vitro and in vivo experiments examined METTL3's role in CC. We employed RNA sequencing, methylated RNA immunoprecipitation sequencing, qPCR, and RNA immunoprecipitation qPCR to explore METTL3's mechanism in CC. METTL3 expression was upregulated in CC, promoting cell proliferation and metastasis. METTL3 knockdown inhibited human cervical cancer by inactivating AKT/mTOR signaling pathway. METTL3-mediated m6A modification was observed in CC cells, targeting phosphodiesterase 3A (PDE3A). METTL3 catalyzed m6A modification on PDE3A mRNA through YTH domain family protein 3 (YTHDF3). Our study indicated the mechanism of m6A modification in CC and suggested the METTL3/YTHDF3/PDE3A axis as a potential clinical target for CC treatment.

Association between methyltransferase-like 3 and non-small cell lung cancer: pathogenesis, therapeutic resistance, and clinical applications

Non-small cell lung cancer (NSCLC) is a malignant cancer that with high incidence, recurrence, and mortality rates in human beings, posing significant threats to human health. Moreover, effective early diagnosis of NSCLC remains limited primarily by the lack of accurate biomarkers. Therefore, there is an urgent need to understand the mechanisms underlying NSCLC pathogenesis and treatment failure. Methyltransferase-like 3 (METTL3) is a prototypical member of a family of which its members transfer methyl groups. It has been implicated in modulating the pathogenesis of NSCLC, as well as conferring resistance to NSCLC therapeutics. The targeting of METTL3 for NSCLC treatment has been reported. However, the relationship between METTL3 and NSCLC remains to be demonstrated. In this review, we discuss relevant interrelationships by summarising the studies on METTL3 in NSCLC pathogenesis, therapeutic resistance, and clinical applications. Current research suggests that the upregulation of METTL3 expression propels the tumorigenesis, progression, and treatment resistance of NSCLC. Therefore, we propose that METTL3 is an excellent candidate biomarker for NSCLC diagnosis and prognosis. Therapeutic targeting of METTL3 has significant potential for NSCLC treatment. This review provides a summary of the association between METTL3 and NSCLC, which would be a valuable reference for both basic and clinical research.

METTL3 inhibits BMSC apoptosis and facilitates osteonecrosis repair via an m6A-IGF2BP2-dependent mechanism

Hypoxia-induced apoptosis of bone marrow mesenchymal stem cells (BMSCs) limits the efficacy of their transplantation for steroid-induced osteonecrosis of the femoral head (SONFH). As apoptosis and RNA methylation are closely related, exploring the role and mechanism of RNA methylation in hypoxic apoptosis of BMSCs is expected to identify new targets for transplantation of BMSCs for SONFH and enhance transplantation efficacy. We performed methylated RNA immunoprecipitation sequencing (MeRIP-seq) combined with RNA-seq on a hypoxia-induced apoptosis BMSC model and found that the RNA methyltransferase-like 3 (METTL3) is involved in hypoxia-induced BMSC apoptosis. The expression of METTL3 was downregulated in BMSCs after hypoxia and in BMSCs implanted in osteonecrosis areas. Knockdown of METLL3 under normoxic conditions promoted apoptosis of BMSCs. In contrast, overexpression of METTL3 promoted the survival of BMSCs under hypoxic conditions, and overexpression of METTL3 promoted the survival of BMSCs in the osteonecrosis area and the repair of the osteonecrosis area. Regarding the mechanism, the m6A levels of the mRNAs of anti-apoptotic genes Bcl-2, Mcl-1, and BIRC5 were significantly increased upon the overexpression of METTL3 under hypoxic conditions, which promoted the binding of Bcl-2, Mcl-1, and BIRC5 mRNAs to IGF2BP2, enhanced the mRNA stability, and increased the protein expression of the three anti-apoptotic genes. In conclusion, overexpression of METTL3 promoted m6A modification of mRNAs of Bcl-2, Mcl-1, and BIRC5, promoted the binding of IGF2BP2 to the above-mentioned mRNAs, enhanced mRNA stability, inhibited hypoxia-induced BMSC apoptosis, and promoted repair of SONFH, thereby providing novel targets for transplantation of BMSCs for SONFH.

RNA modifications in pulmonary diseases

Threatening public health, pulmonary disease (PD) encompasses diverse lung injuries like chronic obstructive PD, pulmonary fibrosis, asthma, pulmonary infections due to pathogen invasion, and fatal lung cancer. The crucial involvement of RNA epigenetic modifications in PD pathogenesis is underscored by robust evidence. These modifications not only shape cell fates but also finely modulate the expression of genes linked to disease progression, suggesting their utility as biomarkers and targets for therapeutic strategies. The critical RNA modifications implicated in PDs are summarized in this review, including N6-methylation of adenosine, N1-methylation of adenosine, 5-methylcytosine, pseudouridine (5-ribosyl uracil), 7-methylguanosine, and adenosine to inosine editing, along with relevant regulatory mechanisms. By shedding light on the pathology of PDs, these summaries could spur the identification of new biomarkers and therapeutic strategies, ultimately paving the way for early PD diagnosis and treatment innovation.

Targeting METTL3 reprograms the tumor microenvironment to improve cancer immunotherapy

The tumor microenvironment (TME) is a heterogeneous ecosystem containing cancer cells, immune cells, stromal cells, cytokines, and chemokines which together govern tumor progression and response to immunotherapies. Methyltransferase-like 3 (METTL3), a core catalytic subunit for RNA N6-methyladenosine (m6A) modification, plays a crucial role in regulating various physiological and pathological processes. Whether and how METTL3 regulates the TME and anti-tumor immunity in non-small-cell lung cancer (NSCLC) remain poorly understood. Here, we report that METTL3 elevates expression of pro-tumorigenic chemokines including CXCL1, CXCL5, and CCL20, and destabilizes PD-L1 mRNA in an m6A-dependent manner, thereby shaping a non-inflamed TME. Thus, inhibiting METTL3 reprograms a more inflamed TME that renders anti-PD-1 therapy more effective in several murine lung tumor models. Clinically, NSCLC patients who exhibit low-METTL3 expression have a better prognosis when receiving anti-PD-1 therapy. Collectively, our study highlights targeting METTL3 as a promising strategy to improve immunotherapy in NSCLC patients.

METTL3-mediated m6A methylation of DNMT1 promotes the progression of non-small cell lung cancer by regulating the DNA methylation of FOXO3a

Background

The aim of this study was to investigate the effect of DNA methylation of Fork Head Box O3 (FOXO3a) on the process of epithelial-mesenchymal transition (EMT) in non-small cell lung cancer (NSCLC).

Methods

The expressions of FOXO3a, DNA methyltransferase 1 (DNMT1), METTL3, and EMT-related proteins (E-cadherin and N-cadherin) were measured. The influence of 5-Aza-dC and DNMT1 on the methylation level in the promoter region of FOXO3a was examined through the application of methylation-specific PCR (MSP). Chromatin immunoprecipitation (ChIP) was employed to detect binding between DNMT1 and the FOXO3a promoter. Methylated RNA immunoprecipitation (MeRIP) was utilized to evaluate the level of DNMT1 N6-methyladenosine (m6A) methylation. The assessment of cell viability and invasion abilities of A549 cells was performed using Cell Counting Kit-8 (CCK-8) and Transwell assays, respectively. NSCLC xenograft mouse models were established by subcutaneously injected treated A549 cells into nude mice.

Results

The expression levels of DNMT1 and DNA methylation level FOXO3a were found to be significantly increased, whereas FOXO3a expression was considerably decreased in NSCLC cell lines and NSCLC tumor tissues. Both 5-Aza-dC treatment and DNMT1 knockdown resulted in the down-regulation of DNA methylation levels of FOXO3a while simultaneously up-regulating the expression of FOXO3a. A ChIP assay demonstrated that DNMT1 has the ability to bind to the promoter region of FOXO3a. Furthermore, the knockdown of DNMT1 promoted E-cadherin expression, but inhibited expression of N-cadherin, cell viability, and invasion ability. However, the knockdown of FOXO3a hindered the effect of DNMT1 knockdown on EMT, cell viability, and invasion ability of A549 cells. This was evidenced by decreased E-cadherin expression and increased N-cadherin expression, as well as increased cell viability and invasion ability. Increased expression of DNMT1 resulted from m6A methylation of DNMT1, which was mediated by METTL3. Overexpression of DNMT1 decreased of E-cadherin expression while increased N-cadherin expression, cell viability, and invasion ability in METTL3-shRNA treated A549 cells. In xenograft mouse models, DNMT1 knockdown significantly reduced tumor volumes and tumor weight. DNMT1 knockdown upregulated the expression of FOXO3a and E-cadherin, while downregulated N-cadherin expression in vivo.

Conclusion

METTL3-mediated m6A methylation of DNMT1 up-regulates FOXO3a promoter methylation, thereby promoting the progression of NSCLC.

METTL3-mediated the m6A modification of SF3B4 facilitates the development of non-small cell lung cancer by enhancing LSM4 expression

BACKGROUND

Splicing factor B subunit 4 (SF3B4) has been confirmed to participate in the progression of many cancers and is considered to be a potential target for non-small cell lung cancer (NSCLC). Thus, the role and molecular mechanism of SF3B4 in NSCLC progression deserves further study.

METHODS

Quantitative real-time PCR and western blot were employed to detect the mRNA and protein levels of SF3B4, Sm-like protein 4 (LSM4) and methyltransferase-like 3 (METTL3). Cell proliferation, apoptosis, invasion, migration and stemness were tested by cell counting kit-8, colony formation, flow cytometry, transwell, wound healing, and sphere formation assays. The interaction between SF3B4 and METTL3 or LSM4 was confirmed by MeRIP, RIP and Co-IP assays. Mice xenograft models were constructed to assess the effects of METTL3 and SF3B4 on NSCLC tumorigenesis.

RESULTS

SF3B4 had high expression in NSCLC tissues and was associated with the shorter overall survival of NSCLC patients. Knockdown of SF3B4 suppressed NSCLC cell proliferation, invasion, migration and stemness, while inducing apoptosis. METTL3 promoted SF3B4 mRNA stability by m6A modification, and its knockdown inhibited NSCLC cell growth, metastasis and stemness by downregulating SF3B4. SF3B4 could interact with LSM4, and sh-SF3B4-mediated the inhibition on NSCLC cell functions could be reversed by LSM4 overexpression. In addition, reduced METTL3 expression restrained NSCLC tumor growth, and this effect was reversed by SF3B4 overexpression.

CONCLUSION

METTL3-stablized SF3B4 promoted NSCLC cell growth, metastasis and stemness via positively regulating LSM4.

METTL3 promotes non-small-cell lung cancer growth and metastasis by inhibiting FDX1 through copper death-associated pri-miR-21-5p maturation

Objective: We probed into the significance of METTL3 in the maturation process of pri-miR-21-5p. We specifically investigated its impact on the regulation of FDX1 and its involvement in the progression of non-small-cell lung cancer (NSCLC). Methods: The Cancer Genome Atlas (TCGA) identified NSCLC factors. Methylation-specific PCR (MSP), clonogenic tests and flow cytometry analyzed cells. Methylated RNA immunoprecipitation (Me-RIP) and dual-luciferase studied miR-21-5p/FDX1. Mice xenografts showed METTL3's tumorigenic effect. Results: METTL3, with high expression but low methylation in NSCLC, influenced cell behaviors. Its suppression reduced oncogenic properties. METTL3 enhanced miR-21-5p maturation, targeting FDX1 and boosting NSCLC tumorigenicity in mice. Conclusion: METTL3 may promote NSCLC development by facilitating pri-miR-21-5p maturation, upregulating miR-21-5p and targeting inhibition of FDX1.

Sulforaphene suppressed cell proliferation and promoted apoptosis of COV362 cells in endometrioid ovarian cancer

Aim

N6-methyladenosine (m6A) RNA methylation exerts a regulatory effect on endometrioid ovarian cancer (EOC), but the specific m6A regulator genes in EOC remain to be explored. This study investigated that sulforaphene (Sul) is implicated in EOC development by regulating methyltransferase-like 3 (METTL3).

Methods

The dysregulated m6A RNA methylation genes in EOC were determined by methylated RNA immunoprecipitation (MeRIP-seq) and RNA sequencing. The roles of METTL3 and/or Sul on viability, proliferative ability, cell cycle, and apoptosis of EOC cells were determined by MTT, colony formation, flow cytometry, and TUNEL staining assay, respectively. The expression of METTL3 and apoptosis-related proteins in EOC cells was detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot assays.

Results

Five m6A RNA methylation regulators (METTL3, ELF3, IGF2BP2, FTO, and METTL14) were differentially expressed in EOC, among which METTL3 had the highest expression level. Silencing METTL3 reduced the clonal expansion and viability of EOC cells, and caused the cells to arrest in the G0/G1 phase. This also promoted apoptosis in the EOC cells and activated the FAS/FADD and mitochondrial apoptosis pathways. In contrast, overexpressing METTL3 had the opposite effect. Sul, in a dose-dependent manner, reduced the viability of EOC cells but promoted their apoptosis. Sul also increased the levels of IGF2BP2 and FAS, while decreasing the levels of KRT8 and METTL3. Furthermore, Sul was able to reverse the effects of METTL3 overexpression on EOC cells.

Conclusions

Sul could suppress cell proliferation and promote apoptosis of EOC cells by inhibiting the METTL3 to activate the FAS/FADD and apoptosis-associated pathways.

METTL3 promotes the malignancy of non-small cell lung cancer by N6-methyladenosine modifying SFRP2

This study aimed to investigate the roles of METTL3, a regulator of m6A, in NSCLC. RT-qPCR was applied to determine mRNA of m6A-associated genes and SFRP2, and western blot were used for ZEB1 and MMP9 protein expression. Total m6A level was measured using methylated RNA immunoprecipitation (MeRIP) assay, and RIP was used to access m6A level of SFRP2. Cellular behaviors were detected using CCK-8 and tranwell assays. Xenograft assays were conducted to further verify the roles of METTL3 and SFRP2 in NSCLC. The expression level of METTL3 was higher in NSCLC than normal controls. However, downregulation of METTL3 restrained the proliferation, migration and invasion of NSCLC cells. Enhanced expression of METTL3 caused the inverse consequences. Moreover, SFRP2 was found to be negatively regulated by METTL3. Intriguingly, the anti-tumor functions of METTL3 knockdown in the phenotype of NSCLC cells and xenograft mice were overturned by inhibition of SFRP2. Silencing METTL3 resulted in the enhanced stability of SFRP2. Finally, downregulation of SFRP2 induced by METTL3 activated the Wnt/β-catenin signaling pathway in NSCLC. METTL3 acted as an oncogene in the pathogenesis of NSCLC via suppressing SFRP2 to activate Wnt/β-catenin signaling pathway, indicating that METTL3 might be a promising predictor in NSCLC.

The critical roles of m6A RNA methylation in lung cancer: from mechanism to prognosis and therapy

Lung cancer, a highly malignant disease, greatly affects patients' quality of life. N6-methyladenosine (m6A) is one of the most common posttranscriptional modifications of various RNAs, including mRNAs and ncRNAs. Emerging studies have demonstrated that m6A participates in normal physiological processes and that its dysregulation is involved in many diseases, especially pulmonary tumorigenesis and progression. Among these, regulators including m6A writers, readers and erasers mediate m6A modification of lung cancer-related molecular RNAs to regulate their expression. Furthermore, the imbalance of this regulatory effect adversely affects signalling pathways related to lung cancer cell proliferation, invasion, metastasis and other biological behaviours. Based on the close association between m6A and lung cancer, various prognostic risk models have been established and novel drugs have been developed. Overall, this review comprehensively elaborates the mechanism of m6A regulation in the development of lung cancer, suggesting its potential for clinical application in the therapy and prognostic assessment of lung cancer.

METTL3 Affects Spinal Cord Neuronal Apoptosis by Regulating Bcl-2 m6A Modifications After Spinal Cord Injury

OBJECTIVE

Spinal cord injury (SCI) is a severe type of neurological trauma. N6-methyladenosine (m6A) modification is one of the most common internal modifications of RNA. The role of METTL3, the predominant methylation enzyme of m6A modification, in SCI remains unclear. This study aimed to investigate the role of methyltransferase METTL3 in SCI.

METHODS

After establishing the oxygen-glucose deprivation (OGD) model of PC12 cells and rat spinal cord hemisection model, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. The m6A modification was identified on B-cell lymphoma 2 (Bcl-2) messenger RNA (mRNA) by bioinformatics analysis, and m6A-RNA immunoprecipitation and RNA immunoprecipitation. In addition, METTL3 was blocked by the specific inhibitor STM2457 and gene knockdown, and then apoptosis levels were measured.

RESULTS

In different models, we found that the expression of METTL3 and the overall m6A modification level were significantly increased in neurons. After inducing OGD, inhibition of METTL3 activity or expression increased the mRNA and protein levels of Bcl-2, inhibited neuronal apoptosis, and improved neuronal viability in the spinal cord.

CONCLUSION

Inhibition of METTL3 activity or expression can inhibit the apoptosis of spinal cord neurons after SCI through the m6A/Bcl-2 signaling pathway.

Current and potential roles of RNA modification-mediated autophagy dysregulation in cancer

Autophagy, a cellular lysosomal degradation and survival pathway, supports nutrient recycling and adaptation to metabolic stress and participates in various stages of tumor development, including tumorigenesis, metastasis, and malignant state maintenance. Among the various factors contributing to the dysregulation of autophagy in cancer, RNA modification can regulate autophagy by directly affecting the expression of core autophagy proteins. We propose that autophagy disorder mediated by RNA modification is an important mechanism for cancer development. Therefore, this review mainly discusses the role of RNA modification-mediated autophagy regulation in tumorigenesis. We summarize the molecular basis of autophagy and the core proteins and complexes at different stages of autophagy, especially those involved in cancer development. Moreover, we describe the crosstalk of RNA modification and autophagy and review the recent advances and potential role of the RNA modification/autophagy axis in the development of multiple cancers. Furthermore, the dual role of the RNA modification/autophagy axis in cancer drug resistance is discussed. A comprehensive understanding and extensive exploration of the molecular crosstalk of RNA modifications with autophagy will provide important insights into tumor pathophysiology and provide more options for cancer therapeutic strategies.

Effect of Polyphenols and Zinc Co-Supplementation on the Development of Neoplasms in Rats with Breast Cancer

The aim of the study was to evaluate the effect of selected polyphenolic compounds: epicatechin, apigenin, and naringenin, administered separately or in combination with zinc (Zn), on the growth and development of the neoplastic process induced by 7,12-dimethylbenz[a]anthracene (DMBA) in rats. The impact of supplementation with the above-mentioned compounds on the content of modified derivatives: 1-methyladenosine, N6-methyl-2'-deoxyadenosine, O-methylguanosine, 7-methylguanine, 3-methyladenine, 1-methylguanine, 2-amino-6,8-dihydroxypurine, and 8-hydroxy-2'-deoxyguanosine in the urine of rats with mammary cancer was also assessed. Female Sprague-Dawley rats divided into 7 groups were used in the study: animals without supplementation and animals supplemented with apigenin, epicatechin, and naringenin separately or in combination with zinc. To induce mammary cancer, rats were treated with DMBA. Modified derivatives were determined by a validated high-performance liquid chromatography coupled to mass spectrometry method. Based on the obtained results, it can be said that supplementation of the animals with naringenin inhibits the development and progression of the neoplastic process in rats treated with 7,12-dimethylbenzanthracene. Neoplastic tumors were found in only 2 of 8 rats (incidence: 25%) and were considered to be at most grade 1 malignancy. The first palpable tumors in the group of animals receiving naringenin appeared two-three weeks later when compared to other groups. The combination of zinc with flavonoids (apigenin, epicatechin, and naringenin) seems to stimulate the process of carcinogenesis. The level of N6-methyl-2'-deoxyadenosine and 3-methyladenine in the urine of rats was statistically significantly higher in the groups supplemented with apigenin, epicatechin, and naringenin administered in combination with Zn than in the groups receiving only polyphenolic compounds. In conclusion, supplementation of rats with selected flavonoids administered separately or in combination with Zn has an impact on the development of neoplasms and the level of modified nucleosides in the urine of rats with breast cancer. Our results raise the question of whether simultaneous diet supplementation with more than one anti-cancer agent may reduce/stimulate the risk of carcinogenesis.

Research Progress on N6-adenosylate Methylation RNA Modification in Heart Failure Remodeling

Cardiovascular disease (CVD) is the major cause of disability-adjusted life years (DALY) and death globally. The most common internal modification of mRNA is N⁶-adenosylate methylation (m⁶A). Recently, a growing number of studies have been devoted to researching cardiac remodeling mechanisms, especially m⁶A RNA methylation, revealing a connection between m⁶A and cardiovascular diseases. This review summarized the current understanding regarding m⁶A and elucidated the dynamic modifications of writers, erasers, and readers. Furthermore, we highlighted m⁶A RNA methylation related to cardiac remodeling and summarized its potential mechanisms. Finally, we discussed the potential of m⁶A RNA methylation in the treatment of cardiac remodeling.

Recent Advances in RNA m6A Modification in Solid Tumors and Tumor Immunity

An analogous field to epigenetics is referred to as epitranscriptomics, which focuses on the study of post-transcriptional chemical modifications in RNA. RNA molecules, including mRNA, tRNA, rRNA, and other non-coding RNA molecules, can be edited with numerous modifications. The most prevalent modification in eukaryotic mRNA is N6-methyladenosine (m6A), which is a reversible modification found in over 7000 human genes. Recent technological advances have accelerated the characterization of these modifications, and they have been shown to play important roles in many biological processes, including pathogenic processes such as cancer. In this chapter, we discuss the role of m6A mRNA modification in cancer with a focus on solid tumor biology and immunity. m6A RNA methylation and its regulatory proteins can play context-dependent roles in solid tumor development and progression by modulating RNA metabolism to drive oncogenic or tumor-suppressive cellular pathways. m6A RNA methylation also plays dynamic roles within both immune cells and tumor cells to mediate the anti-tumor immune response. Finally, an emerging area of research within epitranscriptomics studies the role of m6A RNA methylation in promoting sensitivity or resistance to cancer therapies, including chemotherapy, targeted therapy, and immunotherapy. Overall, our understanding of m6A RNA methylation in solid tumors has advanced significantly, and continued research is needed both to fill gaps in knowledge and to identify potential areas of focus for therapeutic development.

M2-TAMs promote immunoresistance in lung adenocarcinoma by enhancing METTL3-mediated m6A methylation

Background

Immunotherapy has become the first-line treatment for advanced non-small-cell lung cancer (NSCLC), but most patients still fail to benefit or have disease progression following treatment. M2 phenotype tumor-associated macrophages (M2-TAMs) are important cellular components in the immunosuppressive microenvironment of NSCLC, but how they contribute to immunoresistance remains unclear. This study was conducted to investigate the role and mechanism of M2-TAMs in NSCLC immunoresistance.

Methods

We collected postoperative tumor samples for detection of M2-TAMs and other immune cells infiltration by immunofluorescence detection and flow cytometry. We then constructed a non-contact cell co-culture system using Transwell chambers. CCK-8, colony formation, wound healing and invasion assays were performed to evaluated the effect of M2-TAMs on the proliferation, migration and invasion abilities of lung adenocarcinoma (LUAD) cells in vitro. Xenograft model were performed to analysis the effect of M2-TAMs on the tumorigenesis and metastasis of LUAD cells in vivo.

Results

M2-TAMs were greatly increased in the tumor tissue of patients with immunoresistant LUAD. They could significantly promote the proliferation, invasion, and migration of LUAD cells, and improve their resistance to cytotoxic T lymphocytes (CTL) cytotoxicity. Further research showed M2-TAMs could considerably enhance the expression of METTL3 and total m6A RNA level in LUAD cells and interfering with METTL3 could significantly reverse the impairment of M2-TAMs on the efficacy of CTL in killing tumor cells.

Conclusions

In conclusion, M2-TAMs could promote LUAD immunoresistance by enhancing METTL3-mediated m6A methylation. Our results suggest METTL3 could be a potential therapeutic target for reversing immunoresistance and shed new light on the mechanism of M2-TAMs promoting LUAD immunoresistance.

N6-Methyladenosine Modification of CIRCKRT17 Initiated by METTL3 Promotes Osimertinib Resistance of Lung Adenocarcinoma by EIF4A3 to Enhance YAP1 Stability

BACKGROUND

Circular RNAs (circRNAs) play a key role in regulating the drug resistance of numerous human tumors. However, whether circKRT17 involves in the osimertinib resistance of lung adenocarcinoma (LUAD) remains undetermined.

METHODS

Relative mRNA/circRNA and protein levels were detected by qRT-PCR and western blotting. Localization of circKRT17 and YAP1 was determined by FISH and immunofluorescence staining. Cell growth and apoptosis were evaluated using colony formation, EdU assays, and flow cytometry. The N6-methyladenosine (m6A) modification was analyzed by MeRIP. The interplay between EIF4A3 and circKRT17 or YAP1 was verified by RNA pull-down or/and RIP assays. Subcutaneous tumor growth was monitored in nude mice, and Ki-67 and TUNEL staining were carried out to evaluate cell proliferation and apoptosis, respectively.

RESULTS

CircKRT17 and METTL3 were elevated in osimertinib-insensitive LUAD tissues and cells. Knockdown of circKRT 17 and METTL3 increased the sensitivity of LUAD cells to osimertinib. Knockdown of METTL3 decreased the expression of circKRT17 by inhibiting m6A modification. CircKRT17 promoted the stability and nuclear transportation of YAP1 by recruiting EIF4A3 in LUAD cells. Overexpression of YAP1 abolished the impacts of circKRT17 knockdown on the osimertinib sensitivity of LUAD cells. CircKRT17 knockdown increased the repressive effects of osimertinib on tumor growth in vivo by inhibiting YAP1 signaling.

CONCLUSION

METTL3 initiated the m6A modification of circKRT17, thus promoting osimertinib resistance of LUAD by enhancing YAP1 stability through EIF4A4 recruitment.

Cancer-Associated Fibroblasts Hinder Lung Squamous Cell Carcinoma Oxidative Stress-Induced Apoptosis via METTL3 Mediated m6A Methylation of COL10A1

Background. Cancer-associated fibroblasts (CAFs) within the tumor microenvironment are key players in tumorigenesis and tumor development. Nevertheless, the regulatory mechanisms of CAFs on lung squamous cell carcinoma- (LUSC-) associated remain poorly elucidated. Methods. The microarray dataset GSE22874, containing 30 specimens of primary culture of normal fibroblasts (NFs) and 8 specimens of cancer-associated fibroblasts (CAFs) samples derived from LUSC, was retrieved from the Gene Expression Omnibus (GEO) database and then calculated by using the R language (limma package) to identify differentially expressed genes (DEGs). CAF-conditioned medium (CAF-CM) was collected and used to culture LUSC cells, followed by assessment of cell proliferation, apoptosis, and oxidative stress levels by using CCK-8, annexin V-FITC/PI double staining and ELISA assays. Subsequently, COL10A1 was knocked down in CAFs to assess the role of COL10A1 in CAF regulation of LUSC behavior. Bioinformatics online analysis and MeRIP were applied to predict and test the m6A modification of COL10A1 mRNA and the regulatory relationship with METTL3. Rescue experiments were next performed to explore the effects of METTL3 and COL10A1 in CAFs on LUSC cell proliferation, apoptosis, and oxidative stress. LUSC tumor cells with or without (COL10A1-silenced) CAFs were subcutaneously inoculated in nude mice to evaluate the effect of COL10A1 in CAFs on LUSC tumor growth. Results. Elevated expression of COL10A1 was found in LUSC-derived CAFs by GSE22874 dataset analysis. We discovered that COL10A1 and METTL3 was expressed in both LUSC cells and matched CAFs, while COL10A1 expression was prominently higher in CAFs than in LUSC cells. CAF-CM memorably encouraged LUSC cell proliferation and suppressed apoptosis-induced oxidative stress, which was reversed by interfering with COL10A1 expression in CAFs, suggesting that COL10A1 might be secreted by CAFs into the culture medium to exert its effects inside LUSC cells. Global m6A modification was decreased in METTL3 knocked down CAFs. M6A modification, expression levels, and stability of COL10A1 mRNA were impaired upon METTL3 knockdown in CAFs. Overexpression of COL10A1 in CAFs partially reversed the effect of METTL3 knockdown on the malignant behavior of LUSC cells. In vivo studies confirmed that CAFs accelerated LUSC tumor growth, and this effect was counteracted by COL10A1 silencing. Conclusions. COL10A1 secreted by CAFs could facilitate LUSC cell proliferation and repress apoptosis-induced oxidative stress, and the mechanism was due to elevated expression mediated by METTL3 promoting its mRNA m6A modification, thereby accelerating tumor growth.

Implications of m6A methylation and microbiota interaction in non-small cell lung cancer: From basics to therapeutics

N6-methyladenine (m6A) is one of the most common RNA epigenetic modifications in all higher eukaryotes. Increasing evidence demonstrated that m6A-related proteins, acted as oncogenes or tumor suppressors, are abnormally expressed in the cell lines and tissues of non-small cell lung cancer (NSCLC). In addition, lung as the special immune organ contacts with the outer environments and thereby inevitably suffers from different types of microbial pathogen attack. Those microbial pathogens affect the development, progression, and clinical outcomes of NSCLC via altering host m6A modification to disrupt pulmonary immune homeostasis and increase the susceptibility; conversely, host cells modulate m6A modification to repress bacterial colonization. Therefore, m6A harbors the potential to be the novel biomarkers and targets for predicting poor prognosis and chemotherapy sensitivity of patients with lung cancer. In this paper, we provided an overview of the biological properties of m6A-modifying enzymes, and the mechanistic links among lung microbiota, m6A modification and NSCLC. Although the flood of novel m6A-related inhibitors represents many dramatic improvements in NSCLC therapy, their efficacy and toxicity in NSCLC are explored to address these pivotal gaps in the field.

The Epitranscriptome in miRNAs: Crosstalk, Detection, and Function in Cancer

The epitranscriptome encompasses all post-transcriptional modifications that occur on RNAs. These modifications can alter the function and regulation of their RNA targets, which, if dysregulated, result in various diseases and cancers. As with other RNAs, miRNAs are highly modified by epitranscriptomic modifications such as m⁶A methylation, 2′-O-methylation, m⁵C methylation, m⁷G methylation, polyuridine, and A-to-I editing. miRNAs are a class of small non-coding RNAs that regulates gene expression at the post-transcriptional level. miRNAs have gathered high clinical interest due to their role in disease, development, and cancer progression. Epitranscriptomic modifications alter the targeting, regulation, and biogenesis of miRNAs, increasing the complexity of miRNA regulation. In addition, emerging studies have revealed crosstalk between these modifications. In this review, we will summarize the epitranscriptomic modifications—focusing on those relevant to miRNAs—examine the recent crosstalk between these modifications, and give a perspective on how this crosstalk expands the complexity of miRNA biology.

The Role of m6A RNA Methylation in Cancer: Implication for Nature Products Anti-Cancer Research

N6-methyladenosine (m6A) RNA methylation is identified as the most common, abundant and reversible RNA epigenetic modification in messenger RNA (mRNA) and non-coding RNA, especially within eukaryotic messenger RNAs (mRNAs), which post-transcriptionally directs many important processes of RNA. It has also been demonstrated that m6A modification plays a pivotal role in the occurrence and development of tumors by regulating RNA splicing, localization, translation, stabilization and decay. Growing number of studies have indicated that natural products have outstanding anti-cancer effects of their unique advantages of high efficiency and minimal side effects. However, at present, there are very few research articles to study and explore the relationship between natural products and m6A RNA modification in tumorigenesis. m6A is dynamically deposited, removed, and recognized by m6A methyltransferases (METTL3/14, METTL16, WTAP, RBM15/15B, VIRMA, CBLL1, and ZC3H13, called as “writers”), demethylases (FTO and ALKBH5, called as “erasers”), and m6A-specific binding proteins (YTHDF1/2/3, YTHDC1/2, IGH2BP1/2/3, hnRNPs, eIF3, and FMR1, called as “readers”), respectively. In this review, we summarize the biological function of m6A modification, the role of m6A and the related signaling pathway in cancer, such as AKT, NF-kB, MAPK, ERK, Wnt/β-catenin, STAT, p53, Notch signaling pathway, and so on. Furthermore, we reviewed the current research on nature products in anti-tumor, and further to get a better understanding of the anti-tumor mechanism, thus provide an implication for nature products with anti-cancer research by regulating m6A modification in the future.

METTL3-Mediated N6-Methyladenosine Modification of Trim59 mRNA Protects Against Sepsis-Induced Acute Respiratory Distress Syndrome

N6-methyladenosine (m⁶A) RNA modification is a fundamental determinant of mRNA metabolism in eukaryotic cells and is involved in numerous physiological and pathological processes. However, the specific role of m⁶A modification in sepsis-induced acute respiratory distress syndrome(ARDS) remains unknown. Here, we show that the levels of m⁶A RNA were significantly decreased in septic lungs and that METTL3 was the main regulator involved in the absence of m⁶A RNA modification. Pulmonary endothelial barrier damage is a critical process in the pathogenesis of acute lung injury during sepsis. METTL3 regulated endothelial barrier dysfunction and inflammatory responses in sepsis-induced ARDS in vivo and in vitro. Furthermore, we identified tripartite motif-containing (Trim)59 as a key m⁶A effector and Trim59 deficiency exacerbated lung injury. Mechanistically, METTL3 inhibited endothelial injury in sepsis-induced ARDS through Trim59-associated NF-κB inactivation. Our findings revealed novel insights into epitranscriptional mechanisms in sepsis-induced ARDS via m⁶A modifications, which has important application value in the diagnosis, prognosis, and molecular-targeted therapy of sepsis-associated lung injury.

The Emerging Role of N6-Methyladenosine RNA Methylation as Regulators in Cancer Therapy and Drug Resistance

N6-methyladenosine (m⁶A) RNA methylation has been considered the most prevalent, abundant, and conserved internal transcriptional modification throughout the eukaryotic mRNAs. Typically, m⁶A RNA methylation is catalyzed by the RNA methyltransferases (writers), is removed by its demethylases (erasers), and interacts with m⁶A-binding proteins (readers). Accumulating evidence shows that abnormal changes in the m⁶A levels of these regulators are increasingly associated with human tumorigenesis and drug resistance. However, the molecular mechanisms underlying m⁶A RNA methylation in tumor occurrence and development have not been comprehensively clarified. We reviewed the recent findings on biological regulation of m⁶A RNA methylation and summarized its potential therapeutic strategies in various human cancers.

The molecular mechanism of METTL3 promoting the malignant progression of lung cancer

Lung cancer remains one of the major causes of cancer-related death globally. Recent studies have shown that aberrant m⁶A levels caused by METTL3 are involved in the malignant progression of various tumors, including lung cancer. The m⁶A modification, the most abundant RNA chemical modification, regulates RNA stabilization, splicing, translation, decay, and nuclear export. The methyltransferase complex plays a key role in the occurrence and development of many tumors by installing m⁶A modification. In this complex, METTL3 is the first identified methyltransferase, which is also the major catalytic enzyme. Recent findings have revealed that METTL3 is remarkably associated with different aspects of lung cancer progression, influencing the prognosis of patients. In this review, we will focus on the underlying mechanism of METT3 in lung cancer and predict the future work and potential clinical application of targeting METTL3 for lung cancer therapy.

Targeting the RNA m6A modification for cancer immunotherapy

N⁶-methyladenosine (m⁶A) is the most abundant epigenetic modification of RNA, and its dysregulation drives aberrant transcription and translation programs that promote cancer occurrence and progression. Although defective gene regulation resulting from m⁶A often affects oncogenic and tumor-suppressing networks, m⁶A can also modulate tumor immunogenicity and immune cells involved in anti-tumor responses. Understanding this counterintuitive concept can aid the design of new drugs that target m⁶A to potentially improve the outcomes of cancer immunotherapies. Here, we provide an up-to-date and comprehensive overview of how m⁶A modifications intrinsically affect immune cells and how alterations in tumor cell m⁶A modifications extrinsically affect immune cell responses in the tumor microenvironment (TME). We also review strategies for modulating endogenous anti-tumor immunity and discuss the challenge of reshaping the TME. Strategies include: combining specific and efficient inhibitors against m⁶A regulators with immune checkpoint blockers; generating an effective programmable m⁶A gene-editing system that enables efficient manipulation of individual m⁶A sites; establishing an effective m⁶A modification system to enhance anti-tumor immune responses in T cells or natural killer cells; and using nanoparticles that specifically target tumor-associated macrophages (TAMs) to deliver messenger RNA or small interfering RNA of m⁶A-related molecules that repolarize TAMs, enabling them to remodel the TME. The goal of this review is to help the field understand how m⁶A modifications intrinsically and extrinsically shape immune responses in the TME so that better cancer immunotherapy can be designed and developed.

The essential roles of m6A RNA modification to stimulate ENO1-dependent glycolysis and tumorigenesis in lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD)  is the most common subtype of lung cancer. Patient prognosis is poor, and the existing therapeutic strategies for LUAD are far from satisfactory. Recently, targeting N6-methyladenosine (m⁶A) modification of RNA has been suggested as a potential strategy to impede tumor progression. However, the roles of m⁶A modification in LUAD tumorigenesis is unknown.

Methods

Global m⁶A levels and expressions of m⁶A writers, erasers and readers were evaluated by RNA methylation assay, dot blot, immunoblotting, immunohistochemistry and ELISA in human LUAD, mouse models and cell lines. Cell viability, 3D-spheroid generation, in vivo LUAD formation, experiments in cell- and patient-derived xenograft mice and survival analysis were conducted to explore the impact of m⁶A on LUAD. The RNA-protein interactions, translation, putative m⁶A sites and glycolysis were explored in the investigation of the mechanism underlying how m⁶A stimulates tumorigenesis.

Results

The elevation of global m⁶A level in most human LUAD specimens resulted from the combined upregulation of m⁶A writer methyltransferase 3 (METTL3) and downregulation of eraser alkB homolog 5 (ALKBH5). Elevated global m⁶A level was associated with a poor overall survival in LUAD patients. Reducing m⁶A levels by knocking out METTL3 and overexpressing ALKBH5 suppressed 3D-spheroid generation in LUAD cells and intra-pulmonary tumor formation in mice. Mechanistically, m⁶A-dependent stimulation of glycolysis and tumorigenesis occurred via enolase 1 (ENO1). ENO1 mRNA was m⁶A methylated at 359 A, which facilitated it’s binding with the m⁶A reader YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) and resulted in enhanced translation of ENO1. ENO1 positively correlated with METTL3 and global m⁶A levels, and negatively correlated with ALKBH5 in human LUAD. In addition, m⁶A-dependent elevation of ENO1 was associated with LUAD progression. In preclinical models, tumors with a higher global m⁶A level showed a more sensitive response to the inhibition of pan-methylation, glycolysis and ENO activity in LUAD.

Conclusions

The m⁶A-dependent stimulation of glycolysis and tumorigenesis in LUAD is at least partially orchestrated by the upregulation of METTL3, downregulation of ALKBH5, and stimulation of YTHDF1-mediated ENO1 translation. Blocking this mechanism may represent a potential treatment strategy for m⁶A-dependent LUAD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02200-5.

Knockdown of METTL14 suppresses the malignant progression of non-small cell lung cancer by reducing Twist expression

Non-small cell lung cancer (NSCLC) is one of the most malignant cancer types. N6-methyladenosine (m6A), an abundant eukaryotic mRNA modification, has been observed in multiple diseases, particularly cancer. Methyltransferase-like 14 (METTL14) is a central component of the m6A methyltransferase complex and has been reported to promote tumor development in several cancer types. The present study aimed to investigate the role of METTL14 in NSCLC. Relevant clinical and mRNA sequencing data for m6A-related genes were downloaded from The Cancer Genome Atlas database. R software was used to evaluate the expression of m6A regulators in NSCLC. The biological functions of METTL14 were evaluated using Cell Counting Kit-8, colony formation, Transwell migration and western blot analyses. The results demonstrated that METTL14 expression was upregulated in NSCLC tissues and cell lines, and its expression was high in cancer tissues from patients with NSCLC with all four stages (I, II, III and IV) of disease. METTL14 downregulation inhibited cell proliferation and migration in A549 and SK-MES-1 lung cancer cell lines. Knockdown of METTL14 in lung cancer cell lines increased E-cadherin expression and suppressed N-cadherin expression. Furthermore, METTL14 downregulation reduced the expression levels of the transcription factor Twist and the p-AKT/AKT ratio. In conclusion, the present findings revealed that silencing of METTL14 suppressed NSCLC malignancy by inhibiting Twist-mediated activation of AKT signaling. These data suggest that METTL14 may be a potential therapeutic target for NSCLC.

RNA Modifications and Epigenetics in Modulation of Lung Cancer and Pulmonary Diseases

Lung cancer is the leading cause of cancer-related mortality worldwide, and its tumorigenesis involves the accumulation of genetic and epigenetic events in the respiratory epithelium. Epigenetic modifications, such as DNA methylation, RNA modification, and histone modifications, have been widely reported to play an important role in lung cancer development and in other pulmonary diseases. Whereas the functionality of DNA and chromatin modifications referred to as epigenetics is widely characterized, various modifications of RNA nucleotides have recently come into prominence as functionally important. N6-methyladosine (m6A) is the most prevalent internal modification in mRNAs, and its machinery of writers, erasers, and readers is well-characterized. However, several other nucleotide modifications of mRNAs and various noncoding RNAs have also been shown to play an important role in the regulation of biological processes and pathology. Such epitranscriptomic modifications play an important role in regulating various aspects of RNA metabolism, including transcription, translation, splicing, and stability. The dysregulation of epitranscriptomic machinery has been implicated in the pathological processes associated with carcinogenesis including uncontrolled cell proliferation, migration, invasion, and epithelial-mesenchymal transition. In recent years, with the advancement of RNA sequencing technology, high-resolution maps of different modifications in various tissues, organs, or disease models are being constantly reported at a dramatic speed. This facilitates further understanding of the relationship between disease development and epitranscriptomics, shedding light on new therapeutic possibilities. In this review, we summarize the basic information on RNA modifications, including m6A, m1A, m5C, m7G, pseudouridine, and A-to-I editing. We then demonstrate their relation to different kinds of lung diseases, especially lung cancer. By comparing the different roles RNA modifications play in the development processes of different diseases, this review may provide some new insights and offer a better understanding of RNA epigenetics and its involvement in pulmonary diseases.

Cross-Talk between Oxidative Stress and m6A RNA Methylation in Cancer

Oxidative stress is a state of imbalance between oxidation and antioxidation. Excessive ROS levels are an important factor in tumor development. Damage stimulation and excessive activation of oncogenes cause elevated ROS production in cancer, accompanied by an increase in the antioxidant capacity to retain redox homeostasis in tumor cells at an increased level. Although moderate concentrations of ROS produced in cancer cells contribute to maintaining cell survival and cancer progression, massive ROS accumulation can exert toxicity, leading to cancer cell death. RNA modification is a posttranscriptional control mechanism that regulates gene expression and RNA metabolism, and m⁶A RNA methylation is the most common type of RNA modification in eukaryotes. m⁶A modifications can modulate cellular ROS levels through different mechanisms. It is worth noting that ROS signaling also plays a regulatory role in m⁶A modifications. In this review, we concluded the effects of m⁶A modification and oxidative stress on tumor biological functions. In particular, we discuss the interplay between oxidative stress and m⁶A modifications.