bims-rimeca Biomed News
on RNA methylation in cancer
Issue of 2021‒01‒31
fifteen papers selected by
Sk Ramiz Islam
Saha Institute of Nuclear Physics

  1. Mol Ther Nucleic Acids. 2021 Mar 05. 23 487-500
      N6-methyladenosine (m6A) is an epigenetic modification associated with various tumors, but its role in tumorigenesis remains unexplored. Here, as confirmed by methylated RNA immunoprecipitation sequencing (meRIP-seq) and RNA sequencing (RNA-seq) analyses, exposure of human bronchial epithelial (HBE) cells to cigarette smoke extract (CSE) caused an m6A modification in the 3' UTR of ZBTB4, a transcriptional repressor. For these cells, CSE also elevated methyltransferase-like 3 (METTL3) levels, which increased the m6A modification of ZBTB4. RIP-qPCR illustrated that ZBTB4 was the intent gene of YTHDF2 and that levels of ZBTB4 were decreased in an YTHDF2-dependent mechanism. The lower levels of ZBTB4 were associated with upregulation of EZH2, which enhanced H3K27me3 combining with E-cadherin promoter, causing lower E-cadherin levels and induction of the epithelial-mesenchymal transition (EMT). Further, in the lungs of mice, downregulation of METTL3 alleviated the cigarette smoke (CS)-induced EMT. Further, the expression of METTL3 was high in the lung tissues of smokers and inversely correlated with ZBTB4. Overall, our results show that the METTL3-mediated m6A modification of ZBTB4 via EZH2 is involved in the CS-induced EMT and in lung cancer. These results indicate that m6A modifications are a potential therapeutic target of lung damage induced by CS.
    Keywords:  N6-methyladenosine; cigarette smoke; epithelial-mesenchymal transition; lung cancer
  2. Onco Targets Ther. 2021 ;14 413-426
      Purpose: N6-methyladenosine (m6A) modifications represent one of the most common methylation modifications, and they are mediated by m6A RNA methylation regulators. However, their functions in renal cell carcinoma (RCC) are not completely understood. The aim of this study was to investigate the effects of the regulators in RCC.Materials and Methods: The expression levels of the 13 main m6A RNA methylation regulators in RCC were detected and consensus clustering was performed to explore their relationships with RCC. Thereafter, a risk signature based on the regulators was established. This risk model was fully verified by conducting prognostic analyses using two datasets (The Cancer Genome Atlas [TCGA] and Gene Expression Omnibus [GEO] datasets) and a ROC curve analysis.
    Results: Of the 13 main m6A regulators, six were significantly upregulated and four were significantly downregulated in 893 RCC cases compared to 128 normal controls in the TCGA database. Consensus clustering based on the regulators identified two clusters of RCC cases, which were significantly associated with a pathological characteristic (T status). Thus, these results indicated that m6A RNA methylation regulators were associated with RCC. Thereafter, a risk model involving two of the regulators (METTL14 and WTAP) was established. The alterations in the mRNA and protein expression levels of these two regulators were further confirmed based on Human Protein Atlas data and real-time PCR in RCC and normal cell lines. The results indicated that the risk model may serve as an independent prognostic marker of overall survival, and it was also associated with clinicopathological characteristics (T status, M status, pathological stage, and gender) in RCC.
    Conclusion: Collectively, the results of this study indicated that the risk model (based on two m6A RNA methylation regulators) may serve as an independent prognostic indicator of RCC, which may aid further investigation into m6A RNA modification in RCC.
    Keywords:  TCGA; m6A methylation; prognostic signature; renal cell carcinoma
  3. Mol Ther. 2021 Jan 20. pii: S1525-0016(21)00019-8. [Epub ahead of print]
      Growing evidence indicates that N6-methyladenosine (m6A) has emerged as the most pervasive RNA modification in eukaryotic cells. However, the specific role of METTL3 in papillary thyroid carcinoma (PTC) initiation and development remains elusive. Here, we found that downregulation of METTL3 was correlated with malignant progression and poor prognosis in PTC. A variety of gain- and loss-of-functional studies clarified the impact of METTL3 in regulating the growth and metastasis of PTC cells in vitro and in vivo. Specifically, combing RNA-sequencing (RNA-seq) and methylated RNA immunoprecipitation sequencing (MeRIP-seq) technologies, our mechanistic studies pinpointed c-Rel and RelA as downstream m6A targets of METTL3. Moreover, disruption of METTL3 elicited the secretion of interleukin-8 (IL-8), and elevated concentrations of IL-8 promoted the recruitment of tumor-associated neutrophils (TANs) in both chemotaxis assays and mouse models. Administration of IL-8 antagonist SB225002 substantially retarded the tumor growth and abolished the TANs accumulation in immunodeficient mice. Altogether, our findings unraveled that METTL3 played a pivotal tumor-suppressor role in PTC carcinogenesis through c-Rel and RelA-participated inactivation of NF-κB pathway via cooperating with YTHDF2, and altered the TANs infiltration to regulate tumor growth, which extends our understanding of the relationship between m6A modification and plasticity of the tumor microenvironment.
    Keywords:  METTL3; N(6)-methyladenosine; Papillary thyroid cancer; YTHDF2; c-Rel; neutrophils
  4. Front Oncol. 2020 ;10 526866
      N6-methyladenosine (m6A) is a common transcriptomic modification in cancer. Recently, it has been found to be involved in the regulation of non-small cell lung cancer (NSCLC) formation and metastasis. Interleukin 37 (IL-37) plays a crucial protective role in lung cancer. In our previous studies, we found that IL-37 is a potential novel tumor suppressor by inhibiting IL-6 expression to suppress STAT3 activation and decreasing epithelial-to-mesenchymal transition. Moreover, we found that treatment of IL-37 in lung cancer cells induced widespread and dynamic RNA m6A methylation. The effects of RNA m6A methylation of IL-37 treatment require further study. However, the functions of RNA m6A methylation of IL-37 treatment still await elucidation. Using MeRIP-seq and RNA-seq, we uncovered a unique m6A methylation profile in the treatment of IL-37 on the A549 cell line. We also showed the expression of m6A writers METTL3, METTL14, and WTAP and erasers ALKBH5 and FTO in A549 cells and lung cancer tissues after the treatment of IL-37. This study showed that IL-37 could lead to changes in m6A methylation level and related molecule expression level in A546 cells and may downregulate the proliferation by inhibiting Wnt5a/5b pathway in A549 cells. We conclude that IL-37 suppresses tumor growth through regulation of RNA m6A methylation in lung cancer cells.
    Keywords:  A549 cells; N6-methyladenosine; RNA methylation; interleukin 37; lung cancer
  5. Front Cell Dev Biol. 2020 ;8 615071
      Accumulating evidence indicates that N6-methyladenosine (m6A), which directly regulates mRNA, is closely related to multiple biological processes and the progression of different malignancies, including breast cancer (BC). Studies of the aberrant expression of m6A mediators in BC revealed that they were associated with different BC subtypes and functions, such as proliferation, apoptosis, stemness, the cell cycle, migration, and metastasis, through several factors and signaling pathways, such as Bcl-2 and the PI3K/Akt pathway, among others. Several regulators that target m6A have been shown to have anticancer effects. Fat mass and obesity-associated protein (FTO) was identified as the first m6A demethylase, and a series of inhibitors that target FTO were reported to have potential for the treatment of BC by inhibiting cell proliferation and promoting apoptosis. However, the exact mechanism by which m6A modifications are regulated by FTO inhibitors remains unknown. m6A modifications in BC have only been preliminarily studied, and their mechanisms require further investigation.
    Keywords:  FTO inhibitor; N6-methyladenosine; breast cancer; m6A modification regulator; mechanism pathways
  6. Genome Biol. 2021 Jan 28. 22(1): 51
      BACKGROUND: N6-methyladenosine (m6A) and adenosine-to-inosine (A-to-I) RNA editing are two of the most abundant RNA modification events affecting adenosines in mammals. Both these RNA modifications determine mRNA fate and play a pivotal role in tumor development and progression.RESULTS: Here, we show that METTL3, upregulated in glioblastoma, methylates ADAR1 mRNA and increases its protein level leading to a pro-tumorigenic mechanism connecting METTL3, YTHDF1, and ADAR1. We show that ADAR1 plays a cancer-promoting role independently of its deaminase activity by binding CDK2 mRNA, underlining the importance of ADARs as essential RNA-binding proteins for cell homeostasis as well as cancer progression. Additionally, we show that ADAR1 knockdown is sufficient to strongly inhibit glioblastoma growth in vivo.
    CONCLUSIONS: Hence, our findings underscore METTL3/ADAR1 axis as a novel crucial pathway in cancer progression that connects m6A and A-to-I editing post-transcriptional events.
  7. Arch Toxicol. 2021 Jan 26.
      FB1 is a common contaminant of cereal grains that affects human and animal health. It has become increasingly evident that epigenetic changes are implicated in FB1 toxicity. N6-methyladenosine (m6A), the most abundant post-transcriptional RNA modification, is influenced by fluctuations in redox status. Since oxidative stress is a characteristic of FB1 exposure, we determined if there is cross-talk between oxidative stress and m6A in FB1-exposed HepG2 cells. Briefly, HepG2 cells were treated with FB1 (0, 5, 50, 100, 200 µM; 24 h) and ROS, LDH and m6A levels were quantified. qPCR was used to determine the expression of m6A modulators, Nrf2, Keap1 and miR-27b, while western blotting was used to quantify Keap1 and Nrf2 protein expression. Methylation status of Keap1 and Nrf2 promoters was assessed and RNA immunoprecipitation quantified m6A-Keap1 and m6A-Nrf2 levels. FB1 induced accumulation of intracellular ROS (p ≤ 0.001) and LDH leakage (p ≤ 0.001). Elevated m6A levels (p ≤ 0.05) were accompanied by an increase in m6A "writers" [METLL3 (p ≤ 0.01) and METLL14 (p ≤ 0.01)], and "readers" [YTHDF1 (p ≤ 0.01), YTHDF2 (p ≤ 0.01), YTHDF3 (p ≤ 0.001) and YTHDC2 (p ≤ 0.01)] and a decrease in m6A "erasers" [ALKBH5 (p ≤ 0.001) and FTO (p ≤ 0.001)]. Hypermethylation and hypomethylation occurred at Keap1 (p ≤ 0.001) and Nrf2 (p ≤ 0.001) promoters, respectively. MiR-27b was reduced (p ≤ 0.001); however, m6A-Keap1 (p ≤ 0.05) and m6A-Nrf2 (p ≤ 0.01) levels were upregulated. This resulted in the ultimate decrease in Keap1 (p ≤ 0.001) and increase in Nrf2 (p ≤ 0.001) expression. Our findings reveal that m6A RNA methylation can be modified by exposure to FB1, and a cross-talk between m6A and redox regulators does occur.
    Keywords:  Epigenetics; Fumonisin B1; Keap1; Nrf2; Oxidative stress; m6A RNA methylation
  8. Aging (Albany NY). 2021 Jan 20. 12
      The inflammatory microenvironment plays an important role in the onset and progression of lung adenocarcinoma (LUAD), and the liver is a suitable site of metastasis for LUAD cells. However, whether the inflammatory microenvironment of the liver is conducive to the proliferation, invasion, and metastasis of LUAD cells remains unclear. In this study, we confirmed that the hepatic inflammatory microenvironment stimulated by IL-6 promoted the proliferation, migration, invasion, and epithelial-mesenchymal transition of LUAD cells, increased the m6A methylation of total RNA, and transcriptionally activated METTL3 expression. Additionally, METTL3 activated the YAP1/TEAD signaling pathway by increasing the m6A modification and expression of YAP1 mRNA. These results indicate that the hepatic inflammatory microenvironment plays a role in regulating the biological functions of LUAD cells. Further, our study identifies a molecular mechanism that may provide a new strategy for the early diagnosis, treatment, and prognosis of liver metastasis in LUAD patients.
    Keywords:  METTL3; YAP1; adenocarcinoma; liver inflammatory microenvironment; m6A
  9. Biomed Res Int. 2021 ;2021 2769689
      Background: As the most aggressive type of skin cancer, cutaneous melanoma (CM) is experiencing a rapidly rising mortality in recent years. Exploring potential prognostic biomarkers or mechanisms of disease progression therefore has a great significance for CM. The purpose of this study was to identify genetic markers and prognostic performance of N6-methyladenosine (m6A) regulators in CM.Method: Gene expression profiles, copy number variation (CNV), and single nucleotide polymorphism (SNP) data of patients were obtained from The Cancer Genome Atlas (TCGA) database.
    Results: Genomic variation and association analysis of gene expressions revealed a high degree of genomic variation in the presence of m6A-regulated genes. m6A patients with high-frequency genomic variants in the regulatory gene tended to develop a worse prognosis (p < 0.01). Unsupervised cluster analysis of the expression profiles of m6A-regulated genes identified three clinically distinct molecular subtypes, including degradation-enhanced subgroup and immune-enhanced subgroup, with significant prognostic differences (p = 0.046). A novel prognostic signature, which was established according to m6A-related characteristic genes identified through genome-wide expression spectrum, could effectively identify samples with poor prognosis and enhanced immune infiltration, and the effectiveness was also verified in the dataset of the chip.
    Conclusion: We identified genetic changes in the m6A regulatory gene in CM and related survival outcomes. The findings of this study provide new insights into the epigenetic understanding of m6A in CM.
  10. Theranostics. 2021 ;11(5): 2201-2217
      Recent studies have highlighted the biological significance of RNA N6-methyladenosine (m6A) modification in tumorigenicity and progression. However, it remains unclear whether m6A modifications also have potential roles in immune regulation and tumor microenvironment (TME) formation. Methods: In this study, we curated 23 m6A regulators and performed consensus molecular subtyping with NMF algorithm to determine m6A modification patterns and the m6A-related gene signature in colon cancer (CC). The ssGSEA and CIBERSORT algorithms were employed to quantify the relative infiltration levels of various immune cell subsets. An PCA algorithm based m6Sig scoring scheme was used to evaluate the m6A modification patterns of individual tumors with an immune response. Results: Three distinct m6A modification patterns were identified among 1307 CC samples, which were also associated with different clinical outcomes and biological pathways. The TME characterization revealed that the identified m6A patterns were highly consistent with three known immune profiles: immune-inflamed, immune-excluded, and immune-desert, respectively. Based on the m6Sig score, which was extracted from the m6A-related signature genes, CC patients can be divided into high and low score subgroups. Patients with lower m6Sig score was characterized by prolonged survival time and enhanced immune infiltration. Further analysis indicated that lower m6Sig score also correlated with greater tumor mutation loads, PD-L1 expression, and higher mutation rates in SMGs (e.g., PIK3CA and SMAD4). In addition, patients with lower m6Sig scores showed a better immune responses and durable clinical benefits in three independent immunotherapy cohorts. Conclusions: This study highlights that m6A modification is significantly associated with TME diversity and complexity. Quantitatively evaluating the m6A modification patterns of individual tumors will strengthen our understanding of TME characteristics and promote more effective immunotherapy strategies.
    Keywords:  Colon cancer; Immune profiles; Immunotherapy; Tumor microenvironment; m6A modification
  11. RNA Biol. 2021 Jan 27.
      RNA modifications are dynamic chemical entities that expand the RNA lexicon and regulate RNA fate. The most abundant modification present in mRNAs, N6-methyladenosine (m6A), has been implicated in neurogenesis and memory formation. However, whether additional RNA modifications may be playing a role in neuronal functions and in response to environmental queues is largely unknown. Here we characterize the biochemical function and cellular dynamics of two human RNA methyltransferases previously associated with neurological dysfunction, TRMT1 and its homolog, TRMT1-like (TRMT1L). Using a combination of next-generation sequencing, LC-MS/MS, patient-derived cell lines and knockout mouse models, we confirm the previously reported dimethylguanosine (m2,2G) activity of TRMT1 in tRNAs, as well as reveal that TRMT1L, whose activity was unknown, is responsible for methylating a subset of cytosolic tRNAAla(AGC) isodecoders at position 26. Using a cellular in vitro model that mimics neuronal activation and long term potentiation, we find that both TRMT1 and TRMT1L change their subcellular localization upon neuronal activation. Specifically, we observe a major subcellular relocalization from mitochondria and other cytoplasmic domains (TRMT1) and nucleoli (TRMT1L) to different small punctate compartments in the nucleus, which are as yet uncharacterized. This phenomenon does not occur upon heat shock, suggesting that the relocalization of TRMT1 and TRMT1L is not a general reaction to stress, but rather a specific response to neuronal activation. Our results suggest that subcellular relocalization of RNA modification enzymes may play a role in neuronal plasticity and transmission of information, presumably by addressing new targets.
    Keywords:  RNA modifications; RNA-seq; dimethylguanosine; intellectual disability; mismatch signature; neuroblastoma; neuronal activation; transfer RNA
  12. Aging (Albany NY). 2021 Jan 20. 12
      BACKGROUND: Long non-coding RNAs (lncRNAs) and their N6-methyladenosine (M6A) modifications are involved in cancer occurrence and development.METHODS: lncRNA M6A modification in colorectal cancer (CRC) was comprehensively analyzed for the first time.
    RESULTS: M6A levels of lnRNAs in CRC tissues were higher than those in tumor-adjacent normal tissues. A total of 8,332 M6A peaks were detected in 6,690 lncRNAs in CRC tissues. Approximately 91% of the modified lncRNAs had unique M6A modification peaks. A total of 383 lncRNAs were differentially methylated in CRC, of which 48.24% had a length of 1-1,000 bp. Most of these were located on chromosomes 1, 2, 7, 11, 16 and 19; 42.3% were within a sense-overlapping exon. RNA sequencing identified 163 differentially expressed lncRNAs in CRC. GO and KEGG analyses revealed that genes near differentially-methylated or -expressed lncRNAs were associated with CRC occurrence and development. Methylation was positively correlated with lncRNA expression levels in CRC and tumor-adjacent normal tissues. More unmethylated than M6A methylated lncRNA molecules were detected. A competing endogenous RNA (ceRNA) and lncRNA-mRNA expression-regulation network revealed a regulatory relationship between lncRNAs, microRNAs (miRNAs), and mRNAs.
    CONCLUSIONS: The findings may help improve our understanding of lncRNA function in colorectal cancer.
    Keywords:  colorectal cancer; lncRNAs; m6A
  13. J Cell Mol Med. 2021 Jan 24.
      Clinical research data show that gefitinib greatly improves the progression-free survival of patients, so it is used in advanced non-small cell lung cancer patients with EGFR mutation. However, some patients with EGFR sensitive mutations do not have good effects on initial gefitinib treatment, and this mechanism is rarely studied. METTL3, a part of N6-adenosine-methyltransferase, has been reported to play an important role in a variety of tumours. In this study, we found that METTL3 is up-regulated in gefitinib-resistant tissues compared to gefitinib-sensitive tissues. Cell function experiments have proved that under the treatment of gefitinib, METTL3 knockdown promotes apoptosis and inhibits proliferation of lung cancer cells. Mechanistic studies have shown that METTL3 combines with MET and causes the PI3K/AKT signalling pathway to be manipulated, which affects the sensitivity of lung cancer cells to gefitinib. Therefore, our research shows that METTL3 can be used as a molecular marker to predict the efficacy of EGFR-TKI therapy in patients, and METTL3 may be a potential therapeutic target.
    Keywords:  METTL3; RNA methyltransferase; gefitinib resistance; lung adenocarcinoma
  14. Front Genet. 2020 ;11 592042
      Background: Gastric cancer (GC) is one of the most common malignancies in the world, and the fourth most frequent malignancy worldwide. YTHDF2 (YTH domain family 2, YTHDF2) binds to mRNA containing m6A, thereby regulating the localization and stability of the bound mRNA. YTHDF2 was shown to be associated with some cancer patient prognosis. However, the effect of YTHDF2 on gastric cancer and the molecular mechanism of this effect have not been documented.Methods: To conduct this research, YTHDF2 expression levels in public databases and gastric cancer patient samples were analyzed. The effects of YTHDF2 on the growth of gastric cancer cells were detected in vivo and in vitro. RNA-seq was used to analyze the signal pathways regulated by YTHDF2, and experiments were carried out for verification.
    Results: In our study, we found that YTHDF2 has lower expression in GC tissues and GC cells, and inhibits the growth of GC cells. In addition, the analysis of clinical data found that the expression level of YTHDF2 is closely related to the stage of GC and the survival of patients with GC. RNA sequencing results showed that overexpression of YTHDF2 significantly reduced protein expression in the FOXC2 (Forkhead box protein C2, FOXC2) signaling pathway. Finally, we found that knockout of FOXC2 reversed the inhibitory effect of YTHDF2 on GC cells.
    Conclusion: In summary, YTHDF2 inhibits the growth of GC cells by negatively regulating FOXC2 and may serve as a prognostic marker in GC.
    Keywords:  FOXC2; M6A; YTHDF2; cell growth; gastric cancer
  15. Cell Res. 2021 Jan 28.
      The newly identified Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has resulted in a global health emergency because of its rapid spread and high mortality. The molecular mechanism of interaction between host and viral genomic RNA is yet unclear. We demonstrate herein that SARS-CoV-2 genomic RNA, as well as the negative-sense RNA, is dynamically N6-methyladenosine (m6A)-modified in human and monkey cells. Combined RIP-seq and miCLIP analyses identified a total of 8 m6A sites at single-base resolution in the genome. Especially, epidemic strains with mutations at these identified m6A sites have emerged worldwide, and formed a unique cluster in the US as indicated by phylogenetic analysis. Further functional experiments showed that m6A methylation negatively regulates SARS-CoV-2 infection. SARS-CoV-2 infection also triggered a global increase in host m6A methylome, exhibiting altered localization and motifs of m6A methylation in mRNAs. Altogether, our results identify m6A as a dynamic epitranscriptomic mark mediating the virus-host interaction.