YTHDF1 promotes the viability and self‑renewal of glioma stem cells by enhancing LINC00900 stability

YTHDF1, an N6‑methyladenosine (m6A)‑binding protein, is significantly upregulated in glioma tissues. The present study investigated the molecular mechanism underlying the regulatory effects of YTHDF1 on the viability, invasion and self‑renewal of glioma stem cells (GSCs). Glioma and normal brain tissues were collected, and reverse transcription‑quantitative PCR and western blotting were used to measure the gene and protein expression levels, respectively. Methylated RNA immunoprecipitation‑PCR was used to assess the m6A modification level of the target gene. Subsequently GSCs were induced, and YTHDF1 and LINC00900 gene regulation was carried out using lentiviral infection. The viability, invasion and self‑renewal of GSCs were assessed by Cell Counting Kit‑8, Transwell and sphere formation assays, respectively. Binding between YTHDF1 and LINC00900 was verified by RNA immunoprecipitation and RNA pull‑down assays. The targeted binding of microRNA (miR)‑1205 to the LINC00900/STAT3 3'‑UTR was verified using a luciferase reporter assay. The results revealed that YTHDF1 and LINC00900 expression levels were significantly upregulated in glioma tissues, and a high m6A modification level in LINC00900 transcripts was detected in glioma tissues. Overexpression of YTHDF1 promoted GSC viability, invasion and self‑renewal, whereas knockdown of YTHDF1 had the opposite effects. In addition, YTHDF1 maintained the stability of LINC00900 and upregulated its expression through binding to it, thereby promoting GSC viability, invasion and self‑renewal. Furthermore, LINC00900 promoted GSC viability, invasion, self‑renewal and tumor growth by regulating the miR‑1205/STAT3 axis. In conclusion, YTHDF1 promotes GSC viability and self‑renewal by regulating the LINC00900/miR‑1205/STAT3 axis.

RNA m6A methylation and regulatory proteins in pulmonary arterial hypertension

m6A (N6‑methyladenosine) is the most common and abundant apparent modification in mRNA of eukaryotes. The modification of m6A is regulated dynamically and reversibly by methyltransferase (writer), demethylase (eraser), and binding protein (reader). It plays a significant role in various processes of mRNA metabolism, including regulation of transcription, maturation, translation, degradation, and stability. Pulmonary arterial hypertension (PAH) is a malignant cardiopulmonary vascular disease characterized by abnormal proliferation of pulmonary artery smooth muscle cells. Despite the existence of several effective and targeted therapies, there is currently no cure for PAH and the prognosis remains poor. Recent studies have highlighted the crucial role of m6A modification in cardiovascular diseases. Investigating the role of RNA m6A methylation in PAH could provide valuable insights for drug development. This review aims to explore the mechanism and function of m6A in the pathogenesis of PAH and discuss the potential targeting of RNA m6A methylation modification as a treatment for PAH.

m6A‑modified HOXC10 promotes HNSCC progression via co‑activation of ADAM17/EGFR and Wnt/β‑catenin signaling

The homeobox (HOX) gene family plays a fundamental role in carcinogenesis. However, the oncogenic mechanism of HOXC10 in head and neck squamous cell carcinoma (HNSCC) remains unclear. In the present study, it was revealed that HOXC10 expression was significantly higher in HNSCC tissues than in adjacent tissues, and a high level of HOXC10 was closely associated with worse clinical outcomes. HOXC10 overexpression promoted HNSCC cell proliferation, migration, and invasion, both in vitro and in vivo. Mechanistically, chromatin immunoprecipitation sequencing revealed that HOXC10 drove the transcriptional activation of a disintegrin and metalloproteinase 17 (ADAM17), and the ADAM17/epidermal growth factor receptor (EGFR)/ERK1/2 signaling pathway facilitating the proliferation of HNSCC. Furthermore, mass spectrometric analysis indicated that HOXC10 interacted with ribosomal protein S15A (RPS15A) and enhanced RPS15A protein expression, activating the Wnt/β‑catenin pathway and contributing to invasion and metastasis of HNSCC. Additionally, the methylated RNA immune precipitation and RNA antisense purification assays showed that N6‑methyladenosine (m6A) writer, methyltransferase‑like 3, catalyzed m6A modification of the HOXC10 transcript, m6A reader insulin like growth factor 2 mRNA binding protein (IGF2BP)1 and IGF2BP3 involved in recognizing and stabilizing m6A‑tagged HOXC10 mRNA. In summary, the present study identified HOXC10 as a promising candidate oncogene in HNSCC. The m6A modification‑mediated HOXC10 promoted proliferation, migration, and invasion of HNSCC through co‑activation of ADAM17/EGFR and Wnt/β‑catenin signaling, providing a novel diagnostic and prognostic biomarker and a potential therapeutic target for HNSCC.

METTL3 promotes proliferation and migration of colorectal cancer cells by increasing SNHG1 stability

N6‑methyladenosine (m6A) serves an essential role in RNA modulation and is implicated in multiple malignancies, including colorectal cancer (CRC). Methyltransferase‑like 3 (METTL3) is an important writer in m6A modification, however its role in CRC in modifying small nucleolar RNA host gene 1 (SNHG1), an oncogenic long noncoding RNA, remains unclear. In the present study, METTL3 expression in CRC was assessed using online bioinformatics analysis, immunohistochemistry staining, western blotting, reverse transcription (RT)‑quantitative PCR (qPCR) and cell transfections. Cell proliferation, migration and invasion were determined using functional Cell Counting Kit‑8 (CCK‑8) and Transwell assays. SNHG1 expression in CRC was evaluated using online bioinformatics analysis and RT‑qPCR. Methylated RNA immunoprecipitation qPCR was performed to assess m6A modification changes of SNHG1 mRNA. The present study demonstrated that METTL3 is upregulated in CRC tissues and cell lines. Moreover, METTL3 expression was associated with several unfavourable clinical features in patients with CRC, including the stage of lymph node metastases and overall survival. Functional Transwell and CCK‑8 assays demonstrated that knockdown of METTL3 suppressed CRC cell proliferation and migration. Furthermore, METTL3 was positively correlated with SNHG1 in CRC tissue, as indicated by analysis of data from The Cancer Genome Atlas. Mechanistically, SNHG1 contains 18 m6A modification sites. Through cell transfections and actinomycin D assays, the present study found that METTL3‑mediated m6A modification at these sites enhances the stability of SNHG1 in CRC cells. Finally, it was demonstrated that SNHG1 knockdown partially diminished the facilitative effect of METTL3 on CRC cell migration and proliferation. The present study concluded that METTL3, a potential biomarker for assessing overall survival and metastasis in CRC, may serve as an oncogene, promote SNHG1 m6A modification, improve the stability of SNHG1 and enhance SNHG1‑mediated oncogenic function in CRC.

RBM15‑mediating MDR1 mRNA m6A methylation regulated by the TGF‑β signaling pathway in paclitaxel‑resistant ovarian cancer

Ovarian cancer (OC) lacks effective biomarkers for diagnosis at an early stage and often develops chemoresistance after the initial treatment at an advanced stage. RNA‑binding motif protein 15 (RBM15) is an RNA m6A methylation mediator that serves an oncogenic role in some cancers. However, the function and molecular mechanisms of RBM15 in ovarian tumorigenesis and chemoresistance remain to be elucidated. The present study identified the overexpression of RBM15 in OC tissues and paclitaxel (PTX)‑resistant cells using reverse transcription‑quantitative (q)PCR, western blotting and immunohistochemistry. Clinical data analyses showed that high expression of RBM15 was associated with poor prognosis in patients with OC. Overexpression of RBM15 led to an increase in cell viability and colony formation and a decrease in cell sensitivity to PTX and apoptosis, whereas the knockdown of RBM15 resulted in the inhibition of cell viability and colony formation in vitro and tumor formation in vivo and increased cell apoptosis and sensitivity to PTX in a time‑ and dose‑dependent manner. Furthermore, RBM15 knockdown reduced the spheroid formation of PTX‑resistant OC cells. Silencing of RBM15 decreased multidrug resistance 1 (MDR1) mRNA m6A methylation detected by the methylated RNA immunoprecipitation‑qPCR assay and downregulated the expression of a chemo‑drug efflux pump MDR1 at the mRNA and protein levels. Finally, RBM15 expression was suppressed by the activation of the TGF‑β signaling pathway. Thus, the findings revealed a TGF‑β/RBM15/MDR1 regulatory mechanism. Targeting RBM15 may provide a novel therapeutic strategy for the treatment of PTX‑resistant OC.

m6A‑mediated LINC02038 inhibits colorectal cancer progression via regulation of the FAM172A/PI3K/AKT pathway via competitive binding with miR‑552‑5p

Long noncoding RNAs (lncRNAs) are a type of regulatory molecule with potential roles in the development of several different malignancies. However, the underlying mechanisms of lncRNAs in colorectal cancer (CRC) are incompletely understood. The present study investigated the molecular mechanism of LINC02038 in CRC. LINC02038 expression was decreased in CRC tissues compared to the para‑cancerous tissues and LINC02038 overexpression markedly reduced the proliferation, vitality, migration and invasive ability and greatly accelerated apoptosis of colorectal cancer cells. Bioinformatics examination indicated that LINC02038 may have targeted microRNA (miR)‑552‑5p. RNA immunoprecipitation and luciferase reporter assays showed that LINC02038 served as a sponge for miR‑552‑5p, hindering target gene FAM172A of miR‑552‑5p degradation. Moreover, methylated RNA immunoprecipitation (MeRIP)‑qualitative PCR assays revealed that YTHDF2 could identify and regulate the METTL3‑mediated LINC02038 N6‑methyladenosine (m6A) modification and increase its degradation, thereby promoting CRC progression via the PI3K/AKT pathway. Based on the CRC clinical specimens, it was shown that LINC02038 was negatively associated with lymphatic metastasis and distant metastasis. These results revealed that m6A/LINC02038/miR‑552‑5p/FAM172A may be a novel anti‑tumor axis and LINC02038 may serve as a biomarker and treatment option for colorectal cancer.

Mechanisms of N6‑methyladenosine modification in tumor development and potential therapeutic strategies (Review)

N6‑methyladenosine (m6A) modification, as the most common and abundant type of RNA modification in mammalian cells, participates in the processes of mRNA transcription, translation, splicing and degradation, serving to regulate RNA stability. In recent years, a large number of studies have indicated that m6A modification is able to affect tumor progression, participate in tumor metabolism, regulate tumor cell ferroptosis and change the tumor immune microenvironment, thereby affecting tumor immunotherapy. In the current review, the main features of m6A‑associated proteins are presented with a focus on the mechanisms underpinning their roles in tumor progression, metabolism, ferroptosis and immunotherapy, also emphasizing the potential of targeting m6A‑associated proteins as a promising strategy for the treatment of cancer.

METTL3/YTHDF2 m6A axis promotes the malignant progression of bladder cancer by epigenetically suppressing RRAS

The present study aimed to explore the potential roles of the methyltransferase‑like 3 (METTL3)‑mediated methylation of RAS related (RRAS) mRNA in the tumorigenesis and development of bladder cancer (BCa). For this purpose, the relative expression levels of METTL3 in BCa specimens and cell lines were measured using reverse transcription‑quantitative PCR (RT‑qPCR) and western blot analysis. The association between the METTL3 expression level and the clinical characteristics of patients with BCa was analyzed using The Cancer Genome Atlas (TCGA) and Gene Expression Profiling Interactive Analysis databases. Cellular experiments were performed to confirm the effects of METTL3 on the proliferative, migratory and invasive capacities of BCa cells. RT‑qPCR, western blot analysis, methylated RNA immunoprecipitation (MeRIP)‑qPCR and dual‑luciferase report assays were utilized to verify the METTL3/RRAS/YTH N⁶‑methyladenosine (m6A) RNA binding protein 2 (YTHDF2) regulatory axis in BCa. The results revealed that METTL3 expression was markedly increased in BCa specimens and cell lines, and was associated with poor clinical characteristics of patients with BCa. In vitro and in vivo assays demonstrated that the silencing of METTL3 markedly suppressed the proliferative, migratory and invasive capacities of BCa cells. MeRIP‑PCR and dual‑luciferase report assays indicated that METTL3 could bind to the m6A sites of RRAS mRNA and suppress the transcriptional activity of RRAS. YTHDF2 could recognize the m6A sites of RRAS and mediate RRAS degradation. On the whole, the findings of the present study reveal the pivotal role of METTL3‑catalyzed m6A modification in BCa tumorigenesis and development. The change could facilitate BCa tumor growth and metastasis by suppressing RRAS expression in an m6A YTHDF2‑dependent manner. Targeting the METTL3/RRAS/YTHDF2 regulatory axis may thus prove to be a promising strategy for the diagnosis and therapy of BCa.

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

Subsequently to the publication of the above paper, the authors have realized, upon reorganizing all their original data, that errors were made during the assembly of the images in Fig. 5 on p. 8. Specifically, in Fig. 5E, the images intended to represent the 'METTL3 sh‑METTL3' and 'Bcl‑2 sg‑METTL3' immuno-histochemistry staining experiments were selected incorrectly. The revised version of Fig. 5, showing the correctly assembled data panels for the 'METTL3 sh‑METTL3' and 'Bcl‑2 sg‑METTL3' experiments in Fig. 5E, is shown on the next page. The authors sincerely apologize for the errors that were inadvertently introduced during the preparation of this Figure, thank the Editor of Oncology Reports for allowing them the opportunity to publish this Corrigendum, and regret any inconvenience that these errors may have caused to the readership. [Oncology Reports 46: 163, 2021; DOI: 10.3892/or.2021.8114].

Systematic pan‑cancer analysis identifies CDC45 as having an oncogenic role in human cancers

Cell division cycle 45 (CDC45) is an essential protein required for the initiation of DNA replication. In the present study, the role of CDC45 across 33 cancers was systematically investigated. It was observed that the expression of CDC45 was significantly upregulated in most cancers, exhibiting a marked negative correlation with the overall survival. Next, there was no significant difference in prognosis between the genomically altered and unaltered groups with respect to clinical outcomes. A decreased level of CDC45 at the DNA promoter region was also identified in several cancers. Furthermore, CDC45 expression was associated with the levels of tumor-infiltrating immune cells in some specific cancer types. In addition, CDC45 was associated with m⁶A methylation, and CDC45 expression was primarily positively correlated with ‘writers’ and ‘readers’ in various cancers, particularly HNRNPC, RBM15 and YTHDC1. Gene enrichment analysis was also performed. In addition, the AUC of each cancer with respect to its 1-, 3-, and 5-year survival rates were explored. Finally, CCK-8 assays, EdU assays and cell cycle analysis were conducted. In conclusion, the present study demonstrated that CDC45 may be a potential biomarker and target for cancer treatment.

Functions and mechanisms of N6‑methyladenosine in prostate cancer (Review)

Prostate cancer (PCa) has long been a major public health problem affecting men worldwide. Even with treatment, it can develop into castration-resistant PCa. With the continuous advancement in epigenetics, researchers have explored N6-methyladenosine (m⁶A) in search of a more effective and lasting treatment for PCa. m⁶A is widely distributed in mammalian cells and influences various aspects of mRNA metabolism. Recently, it has been associated with the development or suppression of various types of cancer, including PCa. This review summarizes the recent findings on m⁶A regulation and its functions and mechanisms in cells, focusing on the various functional proteins operating within m⁶A in PCa cells. Moreover, the potential clinical value of exploiting m⁶A modification as an early diagnostic marker in PCa diagnosis and therapeutics was discussed. m⁶A may also be used as an indicator to evaluate treatment outcome and prognosis.

Epigenetic modifications in acute myeloid leukemia: The emerging role of circular RNAs (Review)

Canonical epigenetic modifications, which include histone modification, chromatin remodeling and DNA methylation, play key roles in numerous cellular processes. Epigenetics underlies how cells that posses DNA with similar sequences develop into different cell types with different functions in an organism. Earlier epigenetic research has primarily been focused at the chromatin level. However, the number of studies on epigenetic modifications of RNA, such as N1‑methyladenosine, 2'‑O‑ribosemethylation, inosine, 5‑methylcytidine, N6‑methyladenosine (m6A) and pseudouridine, has seen an increase. Circular RNAs (circRNAs), a type of RNA species that lacks a 5' cap or 3' poly(A) tail, are abundantly expressed in acute myeloid leukemia (AML) and may regulate disease progression. circRNAs possess various functions, including microRNA sponging, gene transcription regulation and RNA‑binding protein interaction. Furthermore, circRNAs are m6A methylated in other types of cancer, such as colorectal and hypopharyngeal squamous cell cancers. Therefore, the critical roles of circRNA epigenetic modifications, particularly m6A, and their possible involvement in AML are discussed in the present review. Epigenetic modification of circRNAs may become a diagnostic and therapeutic target for AML in the future.

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

Methyltransferase‑like 3 (METTL3) is an RNA methyltransferase that mediates modification of N6‑methyladenosine (m6A), which serves as an oncogene in various types of cancer. The role of m6A modification in the onset and progression of cancer has attracted growing attention. However, the functional and regulatory mechanisms of METTL3 in non‑small cell lung cancer (NSCLC) progression are still poorly understood. In the present study, METTL3 expression in NSCLC tissue was analyzed using the Gene Expression Profiling Interactive Analysis database. Western blotting and reverse transcription‑quantitative PCR were performed to evaluate the expression of METTL3 in NSCLC tissue and cell lines. Here, knockdown and overexpression of METTL3 notably decreased NSCLC cell viability, apoptosis and migration in vitro and, as well as tumorigenicity in vivo. Expression of METTL3 was upregulated in NSCLC tissue. METTL3 overexpression promoted cell viability and migration in NSCLC, while knockdown of METTL3 yielded the opposite result in vivo and in vitro. METTL3 increased Bcl‑2 translation via m6A modification, which increased viability and enhanced migration of NSCLC cells. METTL3 served as an oncogene in NSCLC via METTL3‑mediated Bcl‑2 mRNA m6A modification, which indicated that targeting METTL3 may be an effective therapeutic strategy for clinical management of NSCLC.

Effects of m6A modifications on signaling pathways in human cancer (Review)

N6‑methyladenosine (m6A) is one of the most prevalent post‑transcriptional RNA modifications. The enzymes involved in the regulation of m6A include methyltransferase (writers), demethylase (erasers) and m6A recognition proteins (readers). Accumulating studies have demonstrated that m6A modifications have a distinct effect on various biological processes, including tumorigenesis, cell differentiation, embryonic development and neurogenic diseases, while our knowledge of the specific mechanism underlying m6A methylation in various cancer types is still limited. Various signaling pathways have an effect on tumorigenesis, invasion and apoptosis of malignant tumors. The present review summarizes the recent progress in research regarding the role of m6A in human cancer and discusses the influence of m6A on classic signaling pathways in malignant tumors.