The m6A methyltransferase METTL16 inhibits the proliferation of pancreatic adenocarcinoma cancer cells via the p21 signaling pathway

Recent Findings in N6-Methyladenosine Modification and Significance in Pancreatic Cancer

BACKGROUND

RNA modifications are widely detected in cells and are involved in RNA structural stabilization and regulation of gene expression. In cancer cells, RNA modifications are altered, resulting in abnormal expression of numerous genes and promoting cancer growth. N1-methyladenosine (m1A), N6-methyladenosine (m6A), N3-methylcytosine (m3C), 5-methylcytosine (m5C), 7-methylguanosine (m7G), and N4-acetylcytidine (ac4C) have been reported as RNA modifications affecting gene expression.

AIM

In this review, the function of m6A in pancreatic cancer is mainly described, and the current status and prospects of RNA modifications are discussed.

METHODOLOGY

We summarize recent reports on m6A writers METTL3, METTL5, METTL14, and METTL16; m6A readers IGF2BP1, IGF2BP2, IGF2BP3, YTHDF1, YTHDF2, and YTHDF3; and m6A erasers ALKBH5 and FTO.

RESULTS

RNA modifications are written to the RNA by the writer, and the reader binds to the RNA modification, causing gene expression to increase or decrease. Gene expression is also regulated by the removal of RNA modifications by the eraser. Moreover, our recent investigation into m6A modifications in pancreatic cancer has led to the identification of several promising candidate biomarkers, highlighting the potential role of epitranscriptomic regulation in tumorigenesis.

CONCLUSION

These findings suggest that further exploration of RNA modification functions may facilitate the identification of novel biomarker and therapeutic target molecules for pancreatic cancer.

METTL16 suppresses ferroptosis in cholangiocarcinoma by promoting ATF4 via m6A modification

Background: N6-methyladenosine (m6A) modification is the most common post-transcriptional modifications, which is critical for the metabolism of ferroptosis-related RNAs. Yet, the impact of m6A modification on ferroptosis in cholangiocarcinoma (CC) is far from clear. Methods: Public databases and tissue arrays were applied to explore the clinical relevance of METTL16 in CC. Then, the effects of METTL16 on growth and ferroptosis were studied in vitro and in vivo. Mechanistically, RNA-sequencing, methylated RNA immunoprecipitation, dual-luciferase reporter assays and RNA stability assays were used to identify the METTL16/ATF4 axis in ferroptosis in CC. Results: Clinically, we find that METTL16 is overexpressed and associated with a poor prognosis in patients with CC. Functionally, METTL16 protects against ferroptosis by maintaining mitochondrial homeostasis, including mitochondrial structure, membrane potential and energy products. It also decreases cellular metabolism of Fe2+ and lipid peroxide, thereby promoting cell growth in vitro and in vivo. Mechanistically, ATF4 is a novel target of METTL16 and METTL16 enhances the m6A level and expression of ATF4 mRNA by inhibiting its decay, which further prevented ferroptosis in CC via m6A modification. Conclusions: Our findings highlighted the role of METTL16/ATF4 in ferroptosis, which sheds light on potential therapeutic strategies for CC.

METTL16 inhibits pancreatic cancer proliferation and metastasis by promoting MROH8 RNA stability and inhibiting CAPN2 expression - experimental studies

BACKGROUND

N6-methyladenosine (m6A) modification plays a crucial role in the progression of various cancers, including pancreatic cancer, by regulating gene expression. However, the specific mechanisms by which m6A affects pancreatic cancer metastasis remain unclear. This study aims to elucidate the role of METTL16, an m6A writer gene, in regulating core genes such as CAPN2 and MROH8, influencing tumor growth and metastasis.

MATERIALS AND METHODS

Transcriptomic data from pancreatic cancer patients in The Cancer Genome Atlas (TCGA) were analyzed to identify m6A-related genes. We performed correlation and survival analyses to uncover core genes influenced by m6A expression. Functional assays, including METTL16 knockdown and overexpression experiments, were conducted in pancreatic cancer cell lines, patient-derived organoids, and animal models. Immunofluorescence, co-immunoprecipitation (Co-IP), and m6A-specific quantitative PCR were used to validate protein interactions and m6A modifications. Chromatin immunoprecipitation (ChIP) analysis was utilized to investigate transcription factor binding at gene promoter regions.

RESULTS

METTL16 and METTL3 were identified as key m6A regulators associated with improved prognosis in pancreatic cancer patients ( P <0.05). CAPN2, CHMP2B, ITGA3, ITGA6, ITPR1, and RAC1 were identified as core genes linked to m6A expression, all significantly correlated with patient prognosis ( P <0.05). METTL16 overexpression significantly inhibited tumor growth and metastasis ( P <0.001) by downregulating CAPN2 through an indirect mechanism involving the transcription factor TBP and the gene MROH8. MROH8 negatively regulated CAPN2 by promoting TBP degradation, with METTL16 enhancing MROH8 mRNA stability through m6A modifications ( P <0.01). Functional assays demonstrated that METTL16 and YTHDC2 (an m6A reader) collaboratively enhanced MROH8 mRNA stability, thereby inhibiting CAPN2 expression and reducing tumor proliferation and metastasis ( P <0.001).

CONCLUSION

This study reveals a novel regulatory axis involving METTL16, MROH8, and TBP that modulates CAPN2 expression, contributing to the suppression of pancreatic cancer progression. The METTL16-MROH8-TBP-CAPN2 pathway offers potential therapeutic targets for pancreatic cancer treatment, highlighting the significance of m6A modifications in tumor regulation. Further clinical validation is needed to confirm these findings in human patients.

The m6A-independent role of epitranscriptomic factors in cancer

Protein function alteration and protein mislocalization are cancer hallmarks that drive oncogenesis. N6-methyladenosine (m6A) deposition mediated by METTL3, METTL16, and METTL5 together with the contribution of additional subunits of the m6A system, has shown a dramatic impact on cancer development. However, the cellular localization of m6A proteins inside tumor cells has been little studied so far. Interestingly, recent evidence indicates that m6A methyltransferases are not always confined to the nucleus, suggesting that epitranscriptomic factors may also have multiple oncogenic roles beyond m6A that still represent an unexplored field. To date novel epigenetic drugs targeting m6A modifiers, such as METTL3 inhibitors, are entering into clinical trials, therefore, the study of the potential onco-properties of m6A effectors beyond m6A is required. Here we will provide an overview of methylation-independent functions of the m6A players in cancer, describing the molecular mechanisms involved and the future implications for therapeutics.

METTL protein family: focusing on the occurrence, progression and treatment of cancer

Methyltransferase-like protein is a ubiquitous enzyme-like protein in the human body, with binding domains for nucleic acids, proteins and other small molecules, and plays an important role in a variety of biological behaviours in normal organisms and diseases, characterised by the presence of a methyltransferase-like structural domain and a structurally conserved SAM-binding domain formed by the seven-stranded β-fold structure in the center of the protein. With the deepening of research, the METTL protein family has been found to be abnormally expressed in a variety of tumor diseases, and the clarification of its relationship with tumor diseases can be used as a molecular therapeutic target and has an important role in the prognosis of tumors. In this paper, we review the structure, biological process, immunotherapy, drug-targeted therapy, and markers of the METTL protein family to provide new ideas for the diagnosis and treatment of tumors.

Gene polymorphisms of METTL5 and METTL16 are related to epithelial ovarian cancer risk in South China: A three-center case-control study

Background: The potential relation of methyltransferase-like gene polymorphisms and epithelial ovarian cancer (EOC) remains unclear. Methods: Five SNPs (METTL5 rs3769767 A>G, METTL16 rs1056321 T>C, METTL5 rs10190853 G>A, METTL5 rs3769768 G>A and METTL16 rs11869256 A>G) of methyltransferase-like genes was selected trough NCBI dbSNP database. Two hundred and eighty-eight cases and 361 controls were enrolled from three hospitals in South China to conduct the case-control study. Genomic DNA was abstracted from peripheral blood and genotyped through a TapMan assay. Stratified analysis was conducted to explore the association of rs10190853, rs3769768, rs11869256 genotype and EOC susceptibility. The combination analysis was adopted to evaluate the relation between inferred haplotypes of the METTL5, METTL16 genes and EOC risk. Multifactor dimensionality reduction (MDR) analysis was performed to verify the interaction of SNPs. Results: Among the five analyzed SNPs, METTL5 rs3769768 AA exhibited a significant association with increased EOC risk, while METTL5 rs10190853 GA, METTL16 rs11869256 GA was certified to decrease the susceptibility of EOC. The stratified analysis further revealed the harmful effect of METTL5 rs3769768 AA in EOC patients. On the contrary, METTL16 rs11869256 AG/GG and METTL5 rs10190853 AA showed the reduced risk of EOC in patients of specific subgroups. Combination analysis identified that haplotypes AAA highly connected with reduced risk of EOC. MDR analysis revealed that these SNPs existed no specific interactions. Conclusion: METTL5 rs3769768 was related to increased risk of EOC. METTL5 rs10190853 and METTL16 rs11869256 decreased the susceptibility in EOC. METTL5 and METTL16 could be potential target of molecular therapy and prognosis markers.