METTL16 promotes hepatocellular carcinoma progression through downregulating RAB11B-AS1 in an m6A-dependent manner

Roles of RNA Methylations in Cancer Progression, Autophagy, and Anticancer Drug Resistance

RNA methylations play critical roles in RNA processes, including RNA splicing, nuclear export, nonsense-mediated RNA decay, and translation. Regulators of RNA methylations have been shown to be differentially expressed between tumor tissues/cancer cells and adjacent tissues/normal cells. N6-methyladenosine (m6A) is the most prevalent internal modification of RNAs in eukaryotes. m6A regulators include m6A writers, m6A demethylases, and m6A binding proteins. Since m6A regulators play important roles in regulating the expression of oncogenes and tumor suppressor genes, targeting m6A regulators can be a strategy for developing anticancer drugs. Anticancer drugs targeting m6A regulators are in clinical trials. m6A regulator-targeting drugs could enhance the anticancer effects of current chemotherapy drugs. This review summarizes the roles of m6A regulators in cancer initiation and progression, autophagy, and anticancer drug resistance. The review also discusses the relationship between autophagy and anticancer drug resistance, the effect of high levels of m6A on autophagy and the potential values of m6A regulators as diagnostic markers and anticancer therapeutic targets.

F-Box Protein 43, Stabilized by N6-Methyladenosine Methylation, Enhances Hepatocellular Carcinoma Cell Growth and Invasion via Promoting p53 Degradation in a Ubiquitin Conjugating Enzyme E2 C-Dependent Manner

The roles of F-box protein 43 (FBXO43) in carcinogenesis have been rarely revealed. The present study investigates the expression, function, and underlying mechanism of FBXO43 in hepatocellular carcinoma (HCC). Firstly, the expression and clinical significance of FBXO43 in HCC were investigated bioinformatically and experimentally using online omics data and local tissue samples. The role of N6-methyladenosine modification (m6A) of mRNA in regulating FBXO43 expression and the effects of m6A/FBXO43 axis alteration on cell proliferation and invasion were investigated further. Moreover, the underlying mechanism of the oncogenic FBXO43 was also explored. The results demonstrated that FBXO43 was significantly upregulated in HCC and was positively correlated with advanced progression and poor prognosis in patients. METTL3 and IGF2BP2 expressions were positively correlated with FBXO43 expression and served as the writer and reader of FBXO43 m6A, respectively, which stabilized and upregulated FBXO43 mRNA in HCC. FBXO43 silencing significantly reduced cell proliferation and invasion, and ectopic expression of FBXO43 could significantly restore the inhibitory effects caused by METTL3 and IGF2BP2 depletion in HCC cells. Mechanistically, FBXO43 depletion reduced the expression of UBE2C, a p53 ubiquitin-conjugating enzyme, suppressed proteasomal degradation of p53, and thus inhibited cell proliferation and invasion in HCC. In summary, the present study revealed that METTL3/IGF2BP2 mediated m6A contributed to the upregulation of FBXO43 that promoted the malignant progression of HCC by stimulating p53 degradation in a UBE2C-dependent manner, highlighting the promising application of FBXO43 as a target in HCC treatment.

A review of literature: role of long noncoding RNA TPT1-AS1 in human diseases

Human diseases are multifactorial processes mainly driven by the intricate interactions of genetic and environmental factors. Long noncoding RNAs (lncRNAs) represent a type of non-coding RNAs with more than 200 nucleotides. Multiple studies have demonstrated that the dysregulation of lncRNAs is associated with complex biological as well as pathological processes through various mechanism, especially the regulation of gene transcription and related signal transduction pathways. Moreover, an increasing number of studies have explored lncRNA-based clinical applications in different diseases. For instance, the lncRNA Tumor Protein Translationally Controlled 1 (TPT1) Antisense RNA 1 (TPT1-AS1) was found to be dysregulated in several types of disease and strongly associated with patient prognosis and diverse clinical features. Recent studies have also documented that TPT1-AS1 modulates numerous biological processes through multiple mechanisms, including cell proliferation, apoptosis, autophagy, invasion, migration, radiosensitivity, chemosensitivity, stemness, and extracellular matrix (ECM) synthesis. Furthermore, TPT1-AS1 was regarded as a promising biomarker for the diagnosis, prognosis and treatment of several human diseases. In this review, we summarize the role of TPT1-AS1 in human diseases with the aspects of its expression, relevant clinical characteristics, molecular mechanisms, biological functions, and subsequent clinical applications.

Integrated investigation of the clinical implications and targeted landscape for RNA methylation modifications in hepatocellular carcinoma

BACKGROUND

RNA methylation (RM) is a crucial post-translational modification (PTM) that directs epigenetic regulation. It mostly consists of N¹-methyladenosine (m¹A), 5-methylcytosine (m⁵C), N³-methylcytidine (m³C), N⁶-methyladenosine (m⁶A), and 2'-O-methylation (Nm). The "writers" mainly act as intermediaries between these modifications and associated biological processes. However, little is known about the interactions and potential functions of these RM writers in hepatocellular carcinoma (HCC).

METHODS

The expression properties and genetic alterations of 38 RM writers were assessed in HCC samples from five bioinformatic datasets. Two patterns associated with RM writers were identified using consensus clustering. Then, utilizing differentially expressed genes (DEGs) from different RM subtypes, we built a risk model called RM_Score. Additionally, we investigated the correlation of RM_Score with clinical characteristics, tumor microenvironment (TME) infiltration, molecular subtypes, therapeutic response, immunotherapy effectiveness, and competing endogenous RNA (ceRNA) network.

RESULTS

RM writers were correlated with TME cell infiltration and prognosis. Cluster_1/2 and gene.cluster_A/B were shown to be capable of distinguishing the HCC patients with poor prognosis after consensus and unsupervised clustering of RNA methylation writers. Additionally, we constructed RNA modification pattern-specific risk model and subdivided the cases into RM_Score high and RM_Score low subgroups. In individual cohorts or merged datasets, the high RM_Score was related to a worse overall survival of HCC patients. RM_Score also exhibited correlations with immune and proliferation related pathways. In response to anti-cancer treatments, the RM_Score had a negative correlation (drug sensitive) with drugs that focused on the MAPK/ERK and metabolism signaling, and a positive correlation (drug resistant) with compounds targeting RKT and PI3K/mTOR signaling pathway. Notably, the RM_Score was connected to the therapeutic effectiveness of PD-L1 blockage, implying that RM writers may be the target of immunotherapy to optimize clinical outcomes. Additionally, a ceRNA network was generated including 2 lncRNAs, 4 miRNAs, and 7 mRNAs that was connected to RM writers.

CONCLUSIONS

We thoroughly investigated the potential functions of RNA methylation writers and established an RM_patterns-based risk model for HCC patients. This study emphasized the critical functions of RM modification in TME infiltration, targeted therapy, and immunotherapy, providing potential targets for HCC.

METTL16 epigenetically enhances GPX4 expression via m6A modification to promote breast cancer progression by inhibiting ferroptosis

Breast cancer is malignant cancer that severely threatens the life quality of female patients. N6-methyladenosine (m6A) is a prevalent modification of RNA. METTL16 is an important methyltransferase. This work aims to study the role of METTL16 in breast cancer cell death. The expression of METTL16 in clinical breast cancer specimens was analyzed by qPCR assay. The in vitro and in vivo breast cancer cell proliferation was measured by CCK8, colony formation, and xenograft mouse model. Cell ferroptosis was assessed by measuring the accumulation of iron, Fe²⁺, and lipid ROS. The mechanistic study was performed by RNA degradation, qPCR, and Western blotting assay. METTL16 was overexpressed in tumor tissues from breast cancer patients compared with the para-tumor tissues. Knockdown of METTL16 suppressed in vitro cell proliferation and in vivo tumor growth of breast cancer cells. Meanwhile, METTL16 silencing led to elevated intracellular levels of iron, Fe²⁺, and lipid ROS, indicating the incidence of ferroptosis. Furthermore, siMETTL16 decreased m6A methylation and enhanced the degradation of GPX4 RNA. METTL16-regulated m6A methylation of GPX4 stimulates proliferation and suppresses ferroptosis of breast cancer cells. Therefore, we concluded that METTL16 epigenetically enhanced GPX4 expression via m6A modification to promote breast cancer progression by inhibiting ferroptosis.

Identification of a Novel N7-Methylguanosine-Related LncRNA Signature Predicts the Prognosis of Hepatocellular Carcinoma and Experiment Verification

(1) Background: It is well-known that long non-coding RNAs (lncRNAs) and N7-methylguanosine (m7G) contribute to hepatocellular carcinoma (HCC) progression. However, it remains unclear whether lncRNAs regulating m7G modification could predict HCC prognosis. Thus, we sought to explore the prognostic implications of m7G-related lncRNAs in HCC patients. (2) Methods: Prognostic M7G-related lncRNAs obtained from The Cancer Genome Atlas (TCGA) database were screened by co-expression analysis and univariate Cox regression analysis. Next, the m7G-related lncRNA signature (m7GRLSig) was conducted by Least absolute shrinkage and selection operator (LASSO) Cox regression and multivariate Cox regression analysis. Kaplan-Meier analysis and time-dependent receiver operating characteristics (ROC) assessed the prognostic abilities of our signature. Univariate and multivariate Cox regression, nomogram, and principal component analysis (PCA) were conducted to evaluate our signature. Subsequently, we investigated the role of m7GRLSig on the immune landscape and sensitivity to drugs in HCC patients. The potential function of lncRNAs obtained from the prognostic signature was explored by in vitro experiments. (3) Results: A novel m7GRLSig was identified using seven meaningful lncRNA (ZFPM2-AS1, AC092171.2, PIK3CD-AS2, NRAV, CASC19, HPN-AS1, AC022613.1). The m7GLPSig exhibited worse survival in the high-risk group and served as an independent prognostic factor. The m7GRLSig stratification was sensitive in assessing the immune landscape and sensitivity to drugs between the high-risk and low-risk groups. Finally, in vitro experiments confirmed that the knockdown of NRAV was accompanied by the downregulation of METTL1 during HCC progression. (4) Conclusions: The m7G-related signature is a potential predictor of HCC prognosis and contributes to individualize the effective drug treatment of HCC.

m6A-related long noncoding RNAs predict prognosis and indicate therapeutic response in endometrial carcinoma

BACKGROUND

N6-methyladenosine (m6A) has been identified as the most common, abundant, and conserved internal transcriptional modification. Long noncoding RNAs (lncRNAs) are noncoding RNAs consisting of more than 200 nucleotides, and the expression of various lncRNAs may affect cancer prognosis. The impact of m6A-associated lncRNAs on uterine corpus endometrial carcinoma (UCEC) prognosis is unknown.

METHODS

In this study, UCEC prognosis-related m6A lncRNAs were screened, bioinformatics analysis was performed, and experimental validation was conducted. Endometrial carcinoma (EC) and normal tissue samples were obtained from The Cancer Genome Atlas. The prognosis-related m6A lncRNAs screened by the least absolute shrinkage and selection operator method were used for multivariate Cox proportional risk regression modeling. Principal component analysis and Gene Ontology, immune function difference, and drug sensitivity analyses of the prognostic models were performed. Prognostic analysis was conducted for m6A-associated lncRNAs. The immune infiltration relationship of m6A-associated lncRNAs in EC was identified using the ssGSEA immune infiltration algorithm. A competing endogenouse RNA network was constructed using the LncACTdb database. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) assays were used to validate the differences in m6A-related lncRNA expression in normal and EC cells.

RESULTS

CDKN2B-AS1 and MIR924HG were found to be risk factors for EC. RAB11B-AS1 was a protective factor in EC patients. MIR924HG expression was upregulated in KLE and RL95-2 endometrial cancer cell lines. Prognostic models involved RAB11B-AS1, LINC01812, HM13-IT1, TPM1-AS, SLC16A1-AS1, LINC01936, and CDKN2B-AS1. The high-risk group was more sensitive to five compounds (ABT.263, ABT.888, AP.24534, ATRA, and AZD.0530) than the low-risk group.

CONCLUSION

These findings contribute to understanding of the function of m6A-related lncRNAs in UCEC and provide promising therapeutic strategies for UCEC.

The Role of the m6A RNA Methyltransferase METTL16 in Gene Expression and SAM Homeostasis

The RNA methylation of adenosine at the N6-position (m⁶A) has attracted significant attention because of its abundance and dynamic nature. It accounts for more than 80% of all RNA modifications present in bacteria and eukaryotes and regulates crucial aspects of RNA biology and gene expression in numerous biological processes. The majority of m⁶A found in mammals is deposited by a multicomponent complex formed between methyltransferase-like (METTL) proteins METTL3 and METTL14. In the last few years, the list of m⁶A writers has grown, resulting in an expansion of our understanding of the importance of m⁶A and the methylation machinery. The characterization of the less familiar family member METTL16 has uncovered a new function of the m⁶A methylation apparatus, namely the fine-tuning of the cellular levels of the major methyl donor S-adenosylmethionine (SAM). METTL16 achieves this by adjusting the levels of the enzyme that synthesizes SAM in direct response to fluctuations in the SAM availability. This review summarizes recent progress made in understanding how METTL16 can sense and relay metabolic information and considers the wider implications. A brief survey highlights similarities and differences between METTL16 and the better-known METTL3/14 complex, followed by a discussion of the target specificity, modes of action and potential roles of METTL16.

Circadian gene CSNK1D promoted the progression of hepatocellular carcinoma by activating Wnt/β-catenin pathway via stabilizing Dishevelled Segment Polarity Protein 3

PURPOSE

A variety of studies have connected circadian rhythm to the initiation and progression of hepatocellular carcinoma (HCC). The purpose of this study was to figure out about the circadian genes' profile characteristics, prognostic significance, and targeted values in HCC.

METHODS

The expression profiles and prognostic significance of circadian genes in the cancer genome atlas liver hepatocellular carcinoma (TCGA-LIHC) database were investigated using bioinformatics analysis. The expression features of Casein Kinase 1 Delta (CSNK1D), a robust signature gene, was further detected by immunohistochemistry, western blotting and Real-time quantitative PCR (RT-qPCR) in a local HCC cohort. The effect of CSNK1D on corresponding phenotypes of HCC cells was evaluated using Cell Counting Kit-8 (CCK8), flowcytometry, clone assay, Transwell assay, and xenograft assay. In addition, the underlying mechanisms of CSNK1D in the Wnt/β-catenin signaling were validated by multiple molecular experiments.

RESULTS

Abnormal expression of the Circadian genome was associated with the malignant clinicopathological characteristics of HCC patients. A 10 circadian gene-based signature with substantial prognostic significance was developed using Cox regression and least absolute shrinkage and selection operator (LASSO) analysis. Of them, CSNK1D, significantly elevated in a local HCC cohort, was chosen for further investigation. Silencing or overexpression of CSNK1D significantly reduced or increased proliferation, invasion, sorafenib resistance, xenograft development, and epithelial-mesenchymal transformation (EMT) of HCC cells, respectively. Mechanically, CSNK1D exacerbated the aggressiveness of HCC cells by activating Wnt/β-catenin signaling through interacting with Dishevelled Segment Polarity Protein 3 (DVL3).

CONCLUSIONS

The Circadian gene CSNK1D was found to contribute to HCC progression by boosting the Wnt/β-catenin pathway, hinting that it could be a prospective therapeutic target for HCC.

LARRPM restricts lung adenocarcinoma progression and M2 macrophage polarization through epigenetically regulating LINC00240 and CSF1

BACKGROUND

Long non-coding RNAs (lncRNAs) are critical regulators in lung adenocarcinoma (LUAD). M2-type tumor-associated macrophages (TAMs) also play oncogenic roles in LUAD. However, the involvement of lncRNAs in TAM activation is still largely unknown.

METHODS

The expressions of LARRPM, LINC00240 and CSF1 were determined by RT-qPCR. The regulation of LINC00240 and CSF1 by LARRPM was investigated by RNA-protein pull-down, RNA immunoprecipitation, chromatin immunoprecipitation and bisulfite DNA sequencing. In vitro and in vivo gain- and loss-of-function assays were performed to investigate the roles of LARRPM.

RESULTS

The lncRNA LARRPM was expressed at low levels in LUAD tissues and cells. The low expression of LARRPM was correlated with advanced stage and poor survival of patients with LUAD. Functional experiments revealed that LARRPM suppressed LUAD cell proliferation, migration and invasion, and promoted apoptosis. LARRPM also repressed macrophage M2 polarization and infiltration. Taken together, LARRPM significantly restricted LUAD progression in vivo. Mechanistically, LARRPM bound and recruited DNA demethylase TET1 to the promoter of its anti-sense strand gene LINC00240, leading to a decrease in DNA methylation level of the LINC00240 promoter and transcriptional activation of LINC00240. Functional rescue assays suggested that the lncRNA LINC00240 was responsible for the roles of LARRPM in the malignant behavior of LUAD cells. LARRPM decreased the binding of TET1 to the CSF1 promoter, resulting in increased DNA methylation of the CSF1 promoter and transcriptional repression of CSF1, which is responsible for the roles of LARRPM in macrophage M2 polarization and infiltration. The TAMs educated by LUAD cells exerted oncogenic roles, which was negatively regulated by LARRPM expressed in LUAD cells.

CONCLUSIONS

LARRPM restricts LUAD progression through repressing both LUAD cell and macrophages. These data shed new insights into the regulation of LUAD progression by lncRNAs and provide data on the potential utility of LARRPM as a target for LUAD treatment.

Interaction between N6-methyladenosine and autophagy in the regulation of bone and tissue degeneration

Bone and tissue degeneration are the most common skeletal disorders that seriously affect people’s quality of life. N6-methyladenosine (m6A) is one of the most common RNA modifications in eukaryotic cells, affecting the alternative splicing, translation, stability and degradation of mRNA. Interestingly, increasing number of evidences have indicated that m6A modification could modulate the expression of autophagy-related (ATG) genes and promote autophagy in the cells. Autophagy is an important process regulating intracellular turnover and is evolutionarily conserved in eukaryotes. Abnormal autophagy results in a variety of diseases, including cardiomyopathy, degenerative disorders, and inflammation. Thus, the interaction between m6A modification and autophagy plays a prominent role in the onset and progression of bone and tissue degeneration. In this review, we summarize the current knowledge related to the effect of m6A modification on autophagy, and introduce the role of the crosstalk between m6A modification and autophagy in bone and tissue degeneration. An in-depth knowledge of the above crosstalk may help to improve our understanding of their effects on bone and tissue degeneration and provide novel insights for the future therapeutics.

A novel cuproptosis-related lncRNA prognostic signature for predicting treatment and immune environment of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is an urgent public health issue due to its poor prognosis and resistance to anti-cancer agents. However, the role of cuproptosis, a newly identified form cell death, in applications of HNSCC is still not a known. In this study, single-cell RNA sequencing data was used to explore cuproptosis-related gene expression in the tumour microenvironment. A prognostic model was constructed based on the cuproptosis-related lncRNA. Various methods were performed to predict the overall survival (OS) of different risk score patients and explore difference in enrichment function and pathways between the risk score patients. Finally, a series of immunogenomic landscape analyses were performed and evaluated the immune function, immune infiltration and sensitivity to chemotherapeutic agents. Cancer cell cluster expressed the essential cuproptosis-related gene. As the risk score increased of HNSCC patients, a significant decrease in survival status and time occurred for patients in the high-risk score patient. The AUC for predicting 1-, 3-, and 5-years OS were 0.679, 0.713 and 0.656, indicating that the model regarded as an independent prognostic signature in comparison with the clinical-pathological characteristics. As a results of GO, the immune function and immune infiltration of different risk score patients were assessed, revealing significant differences in T cell function and abundance of different types of T cells. Low-risk score patients are relatively insensitive to chemotherapy agents such as docetaxel and cisplatin, and easily resistant to immunotherapy. A cuproptosis-related lncRNA prognostic model was constructed to predict OS of HNSCC patients and provided the newly therapeutic strategies.

Progress and application of epitranscriptomic m6A modification in gastric cancer

The relationship between epitranscriptomics and malignant tumours has become a popular research topic in recent years. N6-methyladenosine (m⁶A), the most common post-transcriptional modification in mammals, is involved in various physiological processes in different cancer types, including gastric cancer (GC). The incidence and mortality of GC have been increasing annually, especially in developing countries. Insights into the epitranscriptomic mechanisms of gastric carcinogenesis could provide potential strategies for the prevention, diagnosis, and treatment of GC. In this review, we describe the mechanisms of RNA m6A modification; the functions of m6A regulators in GC; the functional crosstalk among m6A, messenger RNA, and noncoding RNA; and the promising application of m⁶A in the diagnosis and treatment of GC.