METTL3 suppresses anlotinib sensitivity by regulating m6A modification of FGFR3 in oral squamous cell carcinoma

The emerging significance of the METTL family as m6A-modified RNA methyltransferases in head and neck cancer

RNA epigenetic modifications are crucial in tumor development, with N6-methyladenosine (m6A) being the most prevalent epigenetic modification found in all eukaryotic messenger RNAs. Accumulating evidence indicates that m6A modifications significantly influence the progression of various malignancies, including head and neck cancer (HNC). The Methyltransferase-like (METTL) family proteins, a group of methyltransferases identified in recent years, function as the "writers" of m6A modifications. These proteins affect RNA stability, translation efficiency, splicing, and localization, thereby regulating diverse cellular functions and promoting tumorigenesis in multiple cancers through their methylation domains. This review aims to summarize existing literature on the METTL family of m6A-modified RNA to elucidate their roles in HNC, providing a theoretical foundation for their potential use as therapeutic targets.

RNA epigenetic modifications as dynamic biomarkers in cancer: from mechanisms to clinical translation

RNA modifications are crucial for post-transcriptional gene regulation. Research on RNA modifications has become a novel frontier of epitranscriptomics. Up to now, over 170 kinds of modifications have been identified on mRNA and diverse non-coding RNA. Three classes of proteins (writers, erasers, and readers) regulate the addition, removal, and identification of epigenetic marks, thus affecting RNA biological functions. Increasing evidence identifies the dysregulation of RNA modifications in different cancer types and the therapeutic potential of targeting RNA-modifying enzymes. The ability of RNA modifications to improve mRNA stability and translation efficacy and decrease immunogenicity has been exploited for the clinical use of mRNA cancer vaccines. This review aims to shed light on several vital cap, tail, and internal modifications of RNA with a focus on the connection between RNA epigenetic pathways and cancer pathogenesis. We further explore the clinical potential of RNA modifications as dynamic biomarkers for cancer diagnosis, prognosis, and therapeutic response prediction, addressing both technological challenges and translational opportunities. Finally, we analyze the limitations of current studies and discuss the research focus in the future.

METTL3 promotes oral squamous cell carcinoma by regulating miR-146a-5p/SMAD4 axis

N6-methyladenosine (m6A), one of the most prominent and reversible internal modifications of eukaryotic RNAs, has emerged as a critical regulator of gene expression in various cancers including oral squamous cell carcinoma (OSCC), wherein it shapes the tumor-specific epitranscriptomic gene-regulatory networks. METTL3, the primary m6A RNA methyltransferase, is significantly upregulated in OSCC cells leading to increased global m6A levels. Interestingly, METTL3 positively regulates miRNA biogenesis by modulating the processing of primary miRNAs in a m6A-dependent manner. We identified miR-146a-5p, an oncogenic miRNA as one of the METTL3-regulated miRNAs in OSCC. METTL3-depletion or inhibition of its catalytic activity leads to a reduction of miR-146a-5p and an appreciable accumulation of primary miR-146a in OSCC cells. Functional assays examining the effects of miR-146a-5p inhibition or overexpression confirm its oncogenic role in OSCC pathophysiology. Further, SMAD4, a central transducer in TGF-β signaling, was identified as a miR-146a-5p target. In OSCC cells, SMAD4-depletion exacerbates the oncogenic traits, whereas its overexpression exerts the opposite effect. Additionally, METTL3-depletion dysregulates SMAD4-regulated genes suggesting its potential involvement in SMAD4-dependent TGF-β signaling. Taken together, we report that METTL3, an oncogene regulates the expression of SMAD4, a tumor-suppressor via miR-146a-5p, thus unveiling a novel regulatory axis of METTL3/miR-146a-5p/SMAD4 in OSCC, which can potentially have therapeutic implications.

STM2457 impairs the proliferation of esophageal squamous cell carcinoma by activating DNA damage response through ATM-Chk2 axis

METTL3 has been proven to play an important role in the proliferation of Esophageal squamous cell carcinoma (ESCC). In this study, we focused on investigating the therapeutic role and molecular mechanism of STM2457 in ESCC, which is a novel small-molecule inhibitor of METTL3. The effect of STM2457 on ESCC was evaluated using ESCC cell lines by the cell viability measurement, cloning formation assay, scratching assay, transwell assay, and flow cytometry techniques. Furthermore, the molecular mechanism study was employed to evaluate by RT-qPCR, Western blotting, proteomics analysis, comet assay, etc. Additionally, the anticancer effect of STM2457 was carried out by nude mice tumor xenograft in vivo. This study showed STM2457 could significantly inhibit the proliferation and migration of Eca109 and KYSE150 cells, which promoted G0/G1 phase arrest and apoptosis in a dose-dependent manners in vitro. Moreover, proteomics analysis suggested the important role of ATM in action mechanism of STM2457. Further studies showed that STM2457 may activate DNA damage response and the expression of ATM, p-ATM, p-Chk2, and γ-H2AX protein in ATM-Chk2 pathway. Intriguingly, ATM inhibitor CGK-733 and knocking down ATM significantly reduced the expression of ATM in Eca109 and KYSE150 cells treated with STM2457. Importantly, STM2457 significantly upregulated the expression of ATM and γ-H2AX protein and inhibited the growth of ESCC in vivo. Finally, STM2457 combined with PTX could also significantly inhibit the proliferation and migration ability of Eca109 and KYSE150 cells by targeting the ATM-mediated DDR pathway. In tumor-bearing nude mice model, STM2457 combined with Paclitaxel can inhibit the growth of ESCC and increased the expression of ATM and γ-H2AX protein. These findings revealed ATM-Chk2 pathway is a promising therapeutic target for STM2457 to effectively inhibit the proliferation of ESCC.

FTO-mediated demethylation of MTUS1/ATIP1 promotes tumor progression in head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) has been recognized as the seventh most prevalent malignant tumor globally. It is a malignant neoplasm that arises from the mucosal epithelium of head and neck region. In our previous research, we have demonstrated that MTUS1/ATIP1 exhibits anti-cancer properties in HNSCC. Nevertheless, the underlying mechanism responsible for the reduction of MTUS1/ATIP1 expression has not been investigated.

METHODS

HNSCC and adjacent normal tissues were collected and examined using m6A MeRIP-seq, qRT-PCR, and IHC to investigate the relationship between MTUS1/ATIP1 and FTO. MeRIP-qPCR, m6A dot blot, RNA and protein stability assays, and RNC-qRT-PCR were employed to elucidate the mechanism by which FTO mediates demethylation of MTUS1/ATIP1 in HNSCC. Functional assays, subcutaneous tumorigenesis, and in situ tongue cancer models were conducted to assess the impact of the FTO-MTUS1/ATIP1 pathway on proliferative capacity of HNSCC tumors.

RESULTS

FTO was observed to be markedly upregulated and showed a negative correlation with MTUS1/ATIP1 expression in HNSCC. FTO was responsible for mediating m6A demethylation in the 3'UTR of MTUS1/ATIP1, leading to its degradation. Additionally, silencing MTUS1/ATIP1 successfully reversed the tumor-promoting effects on HNSCC triggered by FTO in in vitro and in vivo.

CONCLUSIONS

Our research elucidated the functional importance of FTO-mediated m6A demethylation of MTUS1/ATIP1, suggesting that targeting the FTO-MTUS1/ATIP1 axis could be a prospective novel approach for treating HNSCC.

Expression and role of methyltransferase 3 in oral malignant transformation

OBJECTIVE

To investigate the expression and role of methyltransferase 3 (METTL3) in oral malignant transformation.

MATERIALS AND METHODS

Immunohistochemical method was used to investigate the expression of METTL3 in the human oral malignant transformation. Bioinformatics analysis was used to explore the role of METTL3 in oral malignant transformation. Oral cancer animal model was used to verify the expression trend of METTL3 in oral malignant transformation. Knockdown of METTL3 expression in human oral mucosal precancerous lesion cells was performed to explore the METTL3 effect on proliferation, migration, apoptosis, and cell cycle.

RESULTS

METTL3 expression was significantly up-regulated in the human oral malignant transformation. Moreover, METTL3 was related to the pathway of "Neuroactive ligand-receptor interaction." In addition, METTL3 expression was also significantly up-regulated in the hamster oral malignant transformation. Finally, the proliferation and migration abilities of human oral mucosal precancerous lesion cells were inhibited after METTL3 knockdown.

CONCLUSIONS

In conclusion, we found that METTL3 was up-regulated in oral malignant transformation, and the role may relate to the pathway of "Neuroactive ligand-receptor interaction."

N6-methyladenosine RNA modification in head and neck squamous cell carcinoma (HNSCC): current status and future insights

N6-methyladenosine (m6A) plays a pivotal role in regulating epitranscriptomic mechanisms and is closely linked to the normal functioning of diverse classes of RNAs, both coding as well as noncoding. Recent research highlights the role of m6A RNA methylation in the onset and progression of several cancers, including head and neck squamous cell carcinoma (HNSCC). HNSCC ranks as the seventh most common cancer globally, with a five-year patient survival rate of just 50%. Elevated m6A RNA methylation levels and deregulated expression of various m6A modifiers, i.e. writers, readers, and erasers, have been reported across nearly all HNSCC subtypes. Numerous studies have demonstrated that m6A modifications significantly impact key hallmarks of HNSCC, such as proliferation, apoptosis, migration, and invasion. Furthermore, m6A impacts epithelial-mesenchymal transition (EMT), drug resistance, and aerobic glycolysis, and disrupts the tumor microenvironment. Additionally, transcripts regulated by m6A in HNSCC present themselves as potential diagnostic and prognostic biomarkers. This review attempts to comprehensively summarize the role of m6A RNA methylation and its modifiers in regulating various facets of HNSCC pathogenesis.

LAMA3 Promotes Tumorigenesis of Oral Squamous Cell Carcinoma by METTL3-Mediated N6-Methyladenosine Modification

Laminin subunit alpha 3 (LAMA3) is a cancer regulator. However, its effects and regulatory pathways in oral squamous cell carcinoma (OSCC) progression remain unknown. This research aimed to determine the influence of LAMA3 regulation via methyltransferase-like 3 (METTL3) on OSCC progression. Using quantitative real-time polymerase chain reaction and bioinformatics analysis, the expression levels of LAMA3 and METTL3 in OSCC tissues were examined. The functional roles of LAMA3 and METTL3 were analyzed using cell functional experiments. Using methylated RNA immunoprecipitation and mRNA stability assays, LAMA3 and METTL3 regulation was investigated. In OSCC tissues, LAMA3 was upregulated. LAMA3 inhibition hampered OSCC cell proliferation, invasion, and migration while its overexpression facilitated OSCC cell progression. METTL3 serves as a crucial upstream regulator of LAMA3 in OSCC and upregulates LAMA3 expression via an m6A-dependent mechanism. The low METTL3 expression partially restored the enhanced malignant phenotype induced by LAMA3 overexpression. Our findings indicate that METTL3 and LAMA3 act as pro-oncogenic factors in OSCC, with METTL3 promoting OSCC malignancy via m6A modification-dependent stabilization of LAMA3 transcripts, representing a novel regulatory mechanism in OSCC.