N6-Methyladenosine RNA Methylation Regulator-Related Alternative Splicing (AS) Gene Signature Predicts Non-Small Cell Lung Cancer Prognosis

RBM15 drives the progression of lung adenocarcinoma by regulating N6-methyladenosine-mediated LDHA mRNA stability

Abnormal N6-methyladenosine (m6A) methylation in RNA plays a pivotal role in the pathogenesis of many types of tumors by influencing mRNA metabolism, alternative splicing, translocation, stability and translation. However, the specific regulators and underlying mechanisms of m6A modification in the progression of lung adenocarcinoma are not well understood. In this study, we analyzed the RNA-seq transcriptome data downloaded from The Cancer Genome Atlas (TCGA) database, and identified "m6A writer" RNA binding motif protein 15 (RBM15) expression was significantly elevated in lung adenocarcinoma (LUAD) biopsies, and the higher RBM15 levels were correlated with the poorer overall survival (OS) of LUAD patients. Further study confirmed RBM15 was prominently expressed in LUAD tissues and cell lines. Moreover, silencing RBM15 in PC9 and H1299 cells reduced cell proliferation both in vitro and in vivo, while overexpression of RBM15 in A549 cells promoted cell growth. Mechanistically, lactate dehydrogenase A (LDHA) acted as a downstream target of RBM15. RBM15-mediated m6A modification of LDHA mRNA enhanced its stability to exert an oncogenic role in LUAD. Taken together, our findings suggest that the RBM15/LDHA axis might be a novel and promising therapeutic target for LUAD.

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.

Crosstalk between m6A modification and alternative splicing during cancer progression

Background N6-methyladenosine (m6A), the most prevalent internal mRNA modification in eukaryotes, is added by m6A methyltransferases, removed by m6A demethylases and recognised by m6A-binding proteins. This modification significantly influences carious facets of RNA metabolism and plays a pivotal role in cellular and physiological processes. Main body Pre-mRNA alternative splicing, a process that generates multiple splice isoforms from multi-exon genes, contributes significantly to the protein diversity in mammals. Moreover, the presence of crosstalk between m6A modification and alternative splicing, with m6A modifications on pre-mRNAs exerting regulatory control, has been established. The m6A modification modulates alternative splicing patterns by recruiting specific RNA-binding proteins (RBPs) that regulate alternative splicing or by directly influencing the interaction between RBPs and their target RNAs. Conversely, alternative splicing can impact the deposition or recognition of m6A modification on mRNAs. The integration of m6A modifications has expanded the scope of therapeutic strategies for cancer treatment, while alternative splicing offers novel insights into the mechanistic role of m6A methylation in cancer initiation and progression. Conclusion This review aims to highlight the biological functions of alternative splicing of m6A modification machinery and its implications in tumourigenesis. Furthermore, we discuss the clinical relevance of understanding m6A-dependent alternative splicing in tumour therapies.

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.

Multi-omics data analysis reveals the biological implications of alternative splicing events in lung adenocarcinoma

Cancer is characterized by the dysregulation of alternative splicing (AS). However, the comprehensive regulatory mechanisms of AS in lung adenocarcinoma (LUAD) are poorly understood. Here, we displayed the AS landscape in LUAD based on the integrated analyses of LUAD's multi-omics data. We identified 13,995 AS events in 6309 genes as differentially expressed alternative splicing events (DEASEs) mainly covering protein-coding genes. These DEASEs were strongly linked to "cancer hallmarks", such as apoptosis, DNA repair, cell cycle, cell proliferation, angiogenesis, immune response, generation of precursor metabolites and energy, p53 signaling pathway and PI3K-AKT signaling pathway. We further built a regulatory network connecting splicing factors (SFs) and DEASEs. In addition, RNA-binding protein (RBP) mutations that can affect DEASEs were investigated to find some potential cancer drivers. Further association analysis demonstrated that DNA methylation levels were highly correlated with DEASEs. In summary, our results can bring new insight into understanding the mechanism of AS and provide novel biomarkers for personalized medicine of LUAD.

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.

Construction and validation of an angiogenesis-related lncRNA prognostic model in lung adenocarcinoma

Background: There is increasing evidence that long non-coding RNAs (lncRNAs) can be used as potential prognostic factors for cancer. This study aimed to develop a prognostic model for lung adenocarcinoma (LUAD) using angiogenesis-related long non-coding RNAs (lncRNAs) as potential prognostic factors.

Methods: Transcriptome data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were analyzed to identify aberrantly expressed angiogenesis-related lncRNAs in LUAD. A prognostic signature was constructed using differential expression analysis, overlap analysis, Pearson correlation analysis, and Cox regression analysis. The model’s validity was assessed using K-M and ROC curves, and independent external validation was performed in the GSE30219 dataset. Prognostic lncRNA-microRNA (miRNA)-messenger RNA (mRNA) competing endogenous RNA (ceRNA) networks were identified. Immune cell infiltration and mutational characteristics were also analyzed. The expression of four human angiogenesis-associated lncRNAs was quantified using quantitative real-time PCR (qRT-PCR) gene arrays.

Results: A total of 26 aberrantly expressed angiogenesis-related lncRNAs in LUAD were identified, and a Cox risk model based on LINC00857, RBPMS-AS1, SYNPR-AS1, and LINC00460 was constructed, which may be an independent prognostic predictor for LUAD. The low-risk group had a significant better prognosis and was associated with a higher abundance of resting immune cells and a lower expression of immune checkpoint molecules. Moreover, 105 ceRNA mechanisms were predicted based on the four prognostic lncRNAs. qRT-PCR results showed that LINC00857, SYNPR-AS1, and LINC00460 were significantly highly expressed in tumor tissues, while RBPMS-AS1 was highly expressed in paracancerous tissues.

Conclusion: The four angiogenesis-related lncRNAs identified in this study could serve as a promising prognostic biomarker for LUAD patients.

METTL3 regulates breast cancer-associated alternative splicing switches

Alternative splicing (AS) enables differential inclusion of exons from a given transcript, thereby contributing to the transcriptome and proteome diversity. Aberrant AS patterns play major roles in the development of different pathologies, including breast cancer. N⁶-methyladenosine (m⁶A), the most abundant internal modification of eukaryotic mRNA, influences tumor progression and metastasis of breast cancer, and it has been recently linked to AS regulation. Here, we identify a specific AS signature associated with breast tumorigenesis in vitro. We characterize for the first time the role of METTL3 in modulating breast cancer-associated AS programs, expanding the role of the m⁶A-methyltransferase in tumorigenesis. Specifically, we find that both m⁶A deposition in splice site boundaries and in splicing and transcription factor transcripts, such as MYC, direct AS switches of specific breast cancer-associated transcripts. Finally, we show that five of the AS events validated in vitro are associated with a poor overall survival rate for patients with breast cancer, suggesting the use of these AS events as a novel potential prognostic biomarker.

N6-Methyladenosine-related alternative splicing events play a role in bladder cancer

This study investigated the role of N6-methyladenosine (m6A) and alternative splicing (AS) in bladder cancer (BLCA). The BLCA-related RNA expression profiles and AS events were downloaded from the UCSC Xena and SpliceSeq databases, respectively. Differentially expressed AS (DEAS) was screened, and prognostic-related DEAS events were used to construct prognostic risk models based on Cox proportional hazards regression analysis. Receiver operating characteristic curves and multivariate Cox analysis were used to evaluate the predictive efficiency and independence of these models. We also constructed a protein-to-protein interaction (PPI) network and a regulation network of splicing factors (SFs) and DEAS events. In total, 225 m6A-related prognostic-related DEAS events were identified. The predictive ability of each prognostic model was good, and the alternate terminator model showed the best performance when the area under the curve was 0.793. The risk score of the model was an independent prognostic factor for BLCA. The PPI network revealed that AKT serine/threonine kinase 1, serine- and arginine-rich SF6, and serine- and arginine-rich SF2 had higher-node degrees. A complex regulator correlation was shown in the SF and DEAS networks. This study provides insights for the subsequent understanding of the role of AS events in BLCA.

Serum-derived extracellular vesicles promote the growth and metastasis of non-small cell lung cancer by delivering the m6A methylation regulator HNRNPC through the regulation of DLGAP5

PURPOSE

Serum-derived extracellular vesicles (EVs) have been reported to play an important role in non-small cell lung cancer (NSCLC). The current study sought to explore the effect of serum-EVs delivering m6A methylation regulator heterogeneous nuclear ribonucleoprotein C (HNRNPC) on the development of NSCLC through the regulation of discs large-associated protein 5 (DLGAP5).

METHODS

NSCLC-related RNA-Seq and clinical data were first obtained from the TCGA database to screen differentially expressed m6A-related regulators, which were intersected with the differential genes in NSCLC-related microarray GSE43458 obtained from the GEO database for survival analysis and clinical correlation analysis. Correlation between HNRNPC and DLGAP5 expression was evaluated. Serum-EVs were isolated and identified, and the uptake of EVs by A549 cells was visualized using fluorescence microscopy. In vivo xenograft tumor models and tumor metastasis models were constructed in nude mice to observe growth and metastasis of NSCLC cells.

RESULTS

HNRNPC was associated with poor prognosis and metastasis of NSCLC, and further implicated in the regulation of DNA replication and cell cycle-related pathways. HNRNPC might promote the growth and metastasis of NSCLC by identifying m6A modification of DLGAP5 mRNA. Serum-EVs delivered HNRNPC to NSCLC cells in vitro. In vivo experimentation further confirmed that serum-EVs could deliver HNRNPC to promote the growth and metastasis of NSCLC cells in nude mice.

CONCLUSIONS

Our findings highlight that serum-EVs can deliver HNRNPC to NSCLC cells, wherein HNRNPC recognizes the m6A modification of DLGAP5 mRNA, thus ultimately promoting NSCLC growth and metastasis.

Identification of RNA Modification-Associated Alternative Splicing Signature as an Independent Factor in Head and Neck Squamous Cell Carcinoma

Objective

Head and neck squamous cell carcinoma (HNSCC) is a highly heterotopic malignant tumor. Alternative splicing (AS) and RNA modification have been reported to be involved in tumorigenesis. Therefore, we constructed RNA modification-associated AS (RMA-AS) signature model to predict the prognosis of HNSCC.

Methods

AS events and RNA-modified gene expression information were downloaded from TCGA-HNSCC database. Univariate Cox regression analysis was employed for analyzing prognosis-related AS events. RMA-AS events were obtained by constructing a coexpression network between RNA modification-associated genes and AS events using WGCNA package. The prognostic signatures were analyzed by LASSO, univariate Cox, and multivariate Cox regression. Kaplan-Meier survival analysis, proportional hazard model, and ROC curve were performed to verify the prognostic value. “ESTIMATE” R package, ssGSEA algorithm, and CIBERSORT method were used to detect immune microenvironment in HNSCC. Cytoscape was utilized to build a regulatory network of splicing factor-regulated RMA-AS.

Results

There were 16,574 prognostic AS events and 4 differentially expressed RNA modification-associated genes in HNSCC. Based on RMA-AS events, we obtained a risk model consisting of 14 AS events, named RMA-AS_Score. The samples were divided into RMA-AS_Score high- and RMA-AS_Score low-risk groups, according to the risk score. The RMA-AS_Score high group was related to poor prognosis. Moreover, the RMA-AS_Score signature was an independent prognostic predictor and was related to tumor grade. Meanwhile, the AUC value of RMA-AS_Score was 0.652, which is better than other clinical characteristics. Besides, a nomogram prediction model of quantitative prognosis has also been developed, which has robust effectiveness in predicting prognosis. In addition, the prognostic signature was observably related to immune microenvironment and immune checkpoint. Finally, 14 splicing factors were identified and constructed into a network of splicing factor-regulated RMA-AS.

Conclusion

We identified the RMA-AS signature of HNSCC. This signature could be treated as an independent prognostic predictor.

Molecular characterization, clinical relevance and immune feature of m7G regulator genes across 33 cancer types

Over 170 RNA modifications have been identified after transcriptions, involving in regulation of RNA splicing, processing, translation and decay. Growing evidence has unmasked the crucial role of N6-methyladenosine (m6A) in cancer development and progression, while, as a relative newly found RNA modification, N7-methylguanosine (m7G) is also certified to participate in tumorigenesis via different catalytic machinery from that of m6A. However, system analysis on m7G RNA modification-related regulator genes is lack. In this study, we first investigated the genetic alteration of m7G related regulator genes in 33 cancers, and found mRNA expression levels of most regulator genes were positively correlated with copy number variation (CNV) and negatively correlated with methylation in most cancers. We built a m7G RNA modification model based on the enrichment of the regulator gene scores to evaluate the m7G modification levels in 33 cancers, and investigated the connections of m7G scores to clinical outcomes. Furthermore, we paid close attention to the role of m7G in immunology due to the widely used immune checkpoint blockade therapy. Our results showed the higher m7G scores related to immunosuppression of tumor cells. Further confirmation with phase 3 clinical data with application of anti-PDL1/PDL indicated the impact of m7G modification level on immunotherapy effect. Relevance of m7G regulator genes and drug sensitivity was also evaluated to provide a better treatment choice when treating cancers. In summary, our study uncovered the profile of m7G RNA modification through various cancers, and figured out the connection of m7G modification levels with therapeutical outcomes, providing potential better options of cancer treatment.

LRTCLS: low-rank tensor completion with Laplacian smoothing regularization for unveiling the post-transcriptional machinery of N6-methylation (m6A)-mediated diseases

Recently, N6-methylation (m6A) has recently become a hot topic due to its key role in disease pathogenesis. Identifying disease-related m6A sites aids in the understanding of the molecular mechanisms and biosynthetic pathways underlying m6A-mediated diseases. Existing methods treat it primarily as a binary classification issue, focusing solely on whether an m6A–disease association exists or not. Although they achieved good results, they all shared one common flaw: they ignored the post-transcriptional regulation events during disease pathogenesis, which makes biological interpretation unsatisfactory. Thus, accurate and explainable computational models are required to unveil the post-transcriptional regulation mechanisms of disease pathogenesis mediated by m6A modification, rather than simply inferring whether the m6A sites cause disease or not. Emerging laboratory experiments have revealed the interactions between m6A and other post-transcriptional regulation events, such as circular RNA (circRNA) targeting, microRNA (miRNA) targeting, RNA-binding protein binding and alternative splicing events, etc., present a diverse landscape during tumorigenesis. Based on these findings, we proposed a low-rank tensor completion-based method to infer disease-related m6A sites from a biological standpoint, which can further aid in specifying the post-transcriptional machinery of disease pathogenesis. It is so exciting that our biological analysis results show that Coronavirus disease 2019 may play a role in an m6A- and miRNA-dependent manner in inducing non-small cell lung cancer.

miR-212-5p inhibits nasopharyngeal carcinoma progression by targeting METTL3

This study was conducted to investigate the effect of microRNA-212-5p (miR-212-5p) on the proliferation and apoptosis of nasopharyngeal carcinoma (NPC) cells. Microarray datasets (EXP00394 and EXP00660) were downloaded from the dbDEMC database, and the differentially expressed microRNAs between high-grade and low-grade NPC were analyzed. miR-212-5p and methyltransferase like 3 (METTL3) expression levels in NPC tissues and cells were determined by the quantitative real-time polymerase chain reaction and Western blot. Besides, the relationship between miR-212-5p expression and clinicopathological characteristics of patients was analyzed by the Chi-square test. Cell counting kit-8 assay, 5-ethynyl-2-deoxyuridine (EdU) assay, and flow cytometry were adopted to detect the effect of miR-212-5p on the cell proliferation and apoptosis. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analysis were performed to explore the potential biological functions and the signal pathways related to the target genes of miR-212-5p. Bioinformatics prediction and dual luciferase reporter gene assay were used to verify the relationship between miR-212-5p and METTL3 3' untranslated region. Besides, western blot was adopted to detect the expression of METTL3. Gene set enrichment analysis was performed to analyze the downstream pathways in which METTL3 was enriched. It was found that miR-212-5p was downregulated in NPC tissues, and the low miR-212-5p expression was associated with lymph node metastasis and poor differentiation. miR-212-5p overexpression inhibited the growth and promoted apoptosis of NPC cells; miR-212-5p inhibition functioned oppositely. Mechanistically, miR-212-5p inhibited the proliferation and promoted apoptosis of NPC cells via suppressing METTL3 expression. miR-212-5p/METTL3 was associated with processes of RNA transport and cell cycle. In conclusion, miR-212-5p inhibits the progression of NPC by targeting METTL3.

Ferroptosis-Related Hub Genes in Hepatocellular Carcinoma: Prognostic Signature, Immune-Related, and Drug Resistance Analysis

Background: Hepatocellular carcinoma (HCC) is the most prevalent type of primary liver cancer with a high fatality rate and dismal prognosis because of frequent recurrence and lack of efficient therapies. Ferroptosis is a recently recognized iron-dependent cell death distinct from necroptosis and apoptosis. The relationship between ferroptosis-related hub gene expression and prognosis in HCC remains to be further elucidated.

Methods: Ferroptosis-related genes from the FerrDb database and the mRNA sequencing data and clinical information of HCC patients were obtained from The Cancer Genome Atlas (TCGA) database. The least absolute shrinkage and selection operator (LASSO) Cox regression was applied to identify a prognostic signature consisting of five ferroptosis-related hub genes in the TCGA cohort. The International Cancer Genome Consortium (ICGC) database was utilized to validate the reliability of the signature. Functional enrichment and immune-related analysis, including single-sample gene set enrichment analysis (ssGSEA), immune checkpoints, TIP-related genes, tumor stemness, and m6A-related genes, were performed to analyze the underlying mechanism. Additionally, the correlations between ferroptosis and drug resistance were evaluated using the NCI-60 database.

Results: A 5–hub-gene signature associated with ferroptosis was constructed by multivariate Cox regression analysis to stratify patients into two risk groups. Patients with high risk had worse prognosis than those with low risk. Multivariate Cox regression analysis uncovered that the risk score was an independent prognostic indicator. We also proved the signature’s predictive capacity using the Kaplan–Meier method and receiver operating characteristic (ROC) curve analysis. Functional analysis showed that nuclear division and the cell cycle were enriched. Immune-related analysis revealed that the signature was enriched in immune-related pathways. Moreover, the risk signature was significantly associated with immune cell infiltration, immune checkpoints, TIP-related genes, tumor stem cells, as well as m6A-related genes. Furthermore, these genes were crucial regulators of drug resistance.

Conclusion: We identified and validated a novel hub gene signature that is closely associated with ferroptosis as a new and efficient biomarker with favorable potential for predicting the prognosis of HCC patients. In addition, it also offers new insights into the molecular mechanisms of HCC and provides an effective approach for the treatment of HCC. Further studies are necessary to validate the results of our study.

LncRNA AC098934 promotes proliferation and invasion in lung adenocarcinoma cells by combining METTL3 and m6A modifications

Background: Long non-coding RNA (lncRNA) regulates the tumorigenesis as well as the development of lung adenocarcinoma (LUAD), which is one of the high-mortality cancers. We explored the influence of lncRNA AC098934 on the malignant biological behavior of LUAD and potential underlying molecular mechanisms. Methods: The expression level of AC098934 in either the LUAD or the normal tissues was identified in the TCGA database. Two AC098934 knockdown siRNAs were infected into cells of LUAD, including A549 as well as H1299 cells, using the lentivirus. Real-time Quantitative polymerase chain reaction (QPCR) helped to determine the knockdown efficiency of AC098934. CCK-8, cell cloning, wound healing combined with transwell assays tested the role of AC098934 in the cell proliferation, migration as well as the invasion. Tumor formation experiment in nude mice subcutaneously confirmed the promoting effect of AC098934 in vivo. In addition, combinations of METTL3 and AC098934, as well as m6A and AC098934 were identified through the RIP assay. Results: Compared to the normal tissues, AC098934 was more highly expressed in LUAD tissues. After AC098934 was knocked down by siRNA, the proliferation, invasion, migration as well as tumorigenesis abilities of both A549 and H1299 cells were reduced. Mechanistically, AC098934 could bind to the m6A antibody and METTL3 protein. METTL3 overexpression promoted the m6A modification on AC098934, thereby increasing the interaction of m6A modification. Conclusion: The highly expressed lncRNA AC098934 in LUAD facilitates the cell proliferation as well as invasion either in vitro or in vivo. METTL3 binds, furthermore, modulates the m6A modification of AC098934. Our research revealed a new molecular mechanism, through which AC098934 promoted the malignant behavior of LUAD tumors under the m6A modification induced by METTL3. This indicates that AC098934 is possible to be a promising biomarker as well as a therapeutic target for the patients with LUAD.

5-Methylcytosine-Related Long Noncoding RNAs Are Potential Biomarkers to Predict Overall Survival and Regulate Tumor-Immune Environment in Patients with Bladder Cancer

The role of 5-methylcytosine-related long noncoding RNAs (m5C-lncRNAs) in bladder cancer (BLCA) remains unclear. Here, we aim to study the prognostic value, gene expression characteristics, and correlation between the m5C-lncRNA risk model and the tumor microenvironment, immune infiltration, and tumor mutations in BLCA. After collecting BLCA patient RNA sequence transcriptome data, clinical information and mutation data from the Cancer Genome Atlas (TCGA) database, 17 m5C-related lncRNAs independently correlated with OS were obtained by Lasso and multivariate Cox regression analysis, and a risk model was constructed. Univariate Cox, multivariate Cox regression analysis, and the C-index curve proved that the risk model was a significant independent prognostic indicator for patients with BLCA. ESTIMATE and CIBERSORT indicated that the higher the number of immune cells and stromal cells in TME, the higher the prognostic risk. We found that in the low-risk group, the expression levels of immune cells that predicted a good prognosis were higher, including plasma cells, regulatory T cells, and CD 8 T cells. There is a negative correlation between TMB and risk score. The TMB of the low-risk group is significantly higher than that of the high-risk group. In conclusion, the m5C-related risk model is crucial to predict the prognosis of patients with BLCA.

CircMET promotes tumor proliferation by enhancing CDKN2A mRNA decay and upregulating SMAD3

BACKGROUND

Functions of CircMET (hsa_circ_0082002) which is a circular RNA and derived from MET gene remain understood incompletely. In the present study, Xp11.2 translocation/NONO-TFE3 fusion renal cell carcinoma (NONO-TFE3 tRCC) with up-regulated CircMET was employed to investigate its mechanism in cancer progression and post-transcriptional regulation.

METHODS

FISH and real-time PCR were performed to explore the expression and localization circMET in NONO-TFE3 tRCC tissues and cells. The functions of circMET in tRCC were investigated by proliferation analysis, EdU staining, colony and sphere formation assay. The regulatory mechanisms among circMET, CDKN2A and SMAD3 were investigated by luciferase assay, RNA immunoprecipitation, RNA pulldown and targeted RNA demethylation system.

RESULTS

The expression of circMET was upregulated by NONO-TFE3 fusion in NONO-TFE3 tRCC tissues and cells, and overexpression of circMET significantly promoted the growth of NONO-TFE3 tRCC. Mechanistic studies revealed that circMET was delivered to cytosol by YTHDC1 in N⁶-methyladenosine (m⁶A)-depend manner. CircMET enhances mRNA decay of CDKN2A by direct interaction and recruitment of YTHDF2. Meanwhile, circMET competitively absorbed miR-1197 and prevented those from SMAD3 mRNA.

CONCLUSIONS

CircMET promotes the development of NONO-TFE3 tRCC, and the regulation to both CDKN2A and SMAD3 of circMET was revealed. CircMET has the potential to serve as a novel target for the molecular therapy of NONO-TFE3 tRCC as well as the other cancer with high-expressing circMET.