DDX3 modulates cisplatin resistance in OSCC through ALKBH5-mediated m6A-demethylation of FOXM1 and NANOG

YTHDC1-dependent m6A modification modulated FOXM1 promotes glycolysis and tumor progression through CENPA in triple-negative breast cancer

Triple-negative breast cancer (TNBC) exhibits heightened aggressiveness compared with other breast cancer (BC) subtypes, with earlier relapse, a higher risk of distant metastasis, and a worse prognosis. Transcription factors play a pivotal role in various cancers. Here, we found that factor forkhead box M1 (FOXM1) expression was significantly higher in TNBC than in other BC subtypes and normal tissues. Combining the findings of Gene Ontology (GO) enrichment analysis and a series of experiments, we found that knockdown of the FOXM1 gene attenuated the ability of TNBC cells to proliferate and metastasize both in vivo and in vitro. In addition, Spearman's test showed that FOXM1 significantly correlated with glycolysis-related genes, especially centromere protein A (CENPA) in datasets (GSE76250, GSE76124, GSE206912, and GSE103091). The effect of silencing FOXM1 on the inhibition of CENPA expression, TNBC proliferation, migration, and glycolysis could be recovered by overexpression of CENPA. According to MeRIP, the level of m6A modification on FOMX1 decreased in cells treated with cycloleucine (a m6A inhibitor) compared with that in the control group. The increase in FOXM1 expression caused by YTHDC1 overexpression could be reversed by the m6A inhibitor, which indicated that YTHDC1 enhanced FOXM1 expression depending on m6A modification. Therefore, we concluded that the YTHDC1-m6A modification/FOXM1/CENPA axis plays an important role in TNBC progression and glycolysis.

Dynamic RNA methylation modifications and their regulatory role in mammalian development and diseases

Among over 170 different types of chemical modifications on RNA nucleobases identified so far, RNA methylation is the major type of epitranscriptomic modifications existing on almost all types of RNAs, and has been demonstrated to participate in the entire process of RNA metabolism, including transcription, pre-mRNA alternative splicing and maturation, mRNA nucleus export, mRNA degradation and stabilization, mRNA translation. Attributing to the development of high-throughput detection technologies and the identification of both dynamic regulators and recognition proteins, mechanisms of RNA methylation modification in regulating the normal development of the organism as well as various disease occurrence and developmental abnormalities upon RNA methylation dysregulation have become increasingly clear. Here, we particularly focus on three types of RNA methylations: N6-methylcytosine (m6A), 5-methylcytosine (m5C), and N7-methyladenosine (m7G). We summarize the elements related to their dynamic installment and removal, specific binding proteins, and the development of high-throughput detection technologies. Then, for a comprehensive understanding of their biological significance, we also overview the latest knowledge on the underlying mechanisms and key roles of these three mRNA methylation modifications in gametogenesis, embryonic development, immune system development, as well as disease and tumor progression.

Demethylases in tumors and the tumor microenvironment: Key modifiers of N6-methyladenosine methylation

RNA methylation modifications are widespread in eukaryotes and prokaryotes, with N6-methyladenosine (m6A) the most common among them. Demethylases, including Fat mass and obesity associated gene (FTO) and AlkB homolog 5 (ALKBH5), are important in maintaining the balance between RNA methylation and demethylation. Recent studies have clearly shown that demethylases affect the biological functions of tumors by regulating their m6A levels. However, their effects are complicated, and even opposite results have appeared in different articles. Here, we summarize the complex regulatory networks of demethylases, including the most important and common pathways, to clarify the role of demethylases in tumors. In addition, we describe the relationships between demethylases and the tumor microenvironment, and introduce their regulatory mechanisms. Finally, we discuss evaluation of demethylases for tumor diagnosis and prognosis, as well as the clinical application of demethylase inhibitors, providing a strong basis for their large-scale clinical application in the future.

Transcriptional regulation of cancer stem cell: regulatory factors elucidation and cancer treatment strategies

Cancer stem cells (CSCs) were first discovered in the 1990s, revealing the mysteries of cancer origin, migration, recurrence and drug-resistance from a new perspective. The expression of pluripotent genes and complex signal regulatory networks are significant features of CSC, also act as core factors to affect the characteristics of CSC. Transcription is a necessary link to regulate the phenotype and potential of CSC, involving chromatin environment, nucleosome occupancy, histone modification, transcription factor (TF) availability and cis-regulatory elements, which suffer from ambient pressure. Especially, the expression and activity of pluripotent TFs are deeply affected by both internal and external factors, which is the foundation of CSC transcriptional regulation in the current research framework. Growing evidence indicates that regulating epigenetic modifications to alter cancer stemness is effective, and some special promoters and enhancers can serve as targets to influence the properties of CSC. Clarifying the factors that regulate CSC transcription will assist us directly target key stem genes and TFs, or hinder CSC transcription through environmental and other related factors, in order to achieve the goal of inhibiting CSC and tumors. This paper comprehensively reviews the traditional aspects of transcriptional regulation, and explores the progress and insights of the impact on CSC transcription and status through tumor microenvironment (TME), hypoxia, metabolism and new meaningful regulatory factors in conjunction with the latest research. Finally, we present opinions on omnidirectional targeting CSCs transcription to eliminate CSCs and address tumor resistance.

DDX27 regulates oral squamous cell carcinoma development through targeting CSE1L

THE HEADINGS AIMS

DEAD-box helicase 27 (DDX27), a member of the DEAD-Box nucleic acid helicase family, holds an elusive role in oral squamous cell carcinoma (OSCC). This study aims to unravel the regulatory functions of DDX27 in OSCC and explore its downstream targets.

MATERIALS AND METHODS

A commercial oral squamous cell carcinoma (OSCC) tissue microarray (TMA) was utilized. We analyzed differentially expressed genes in OSCC through the GEO database. Target gene silencing was achieved using the shRNA-mediated lentivirus method. Coexpedia analysis identified co-expressed genes associated with DDX27. Additionally, a Co-Immunoprecipitation (Co-IP) experiment confirmed the protein interaction between DDX27 and CSE1L. Xenograft tumor models were employed to evaluate DDX27's role in OSCC tumor formation.

KEY FINDINGS

Elevated DDX27 expression in OSCC correlated with a higher pathological grade. DDX27 knockdown resulted in decreased cell proliferation, increased apoptosis, inhibited cell migration, and induced G2/M phase cell cycle arrest, as well as impaired tumor outgrowth. Coexpedia analysis identified STAU1, NELFCD, and CSE1L as top co-expressed genes. Lentiviral vectors targeting STAU1, NELFCD, and CSE1L revealed that silencing CSE1L significantly impaired cell growth, indicating it as a downstream target of DDX27. Cell rescue experiments demonstrated that increased DDX27 levels ameliorated cell proliferation, attenuated apoptosis, and CSE1L depletion blocked cell development induced by DDX27 overexpression.

SIGNIFICANCES

This study highlighted DDX27 as a potential therapeutic target for OSCC treatment, shedding light on its crucial role in OSCC development. Targeting DDX27 or its downstream effector, CSE1L, holds promise for innovative OSCC therapies.

ALKBH5 regulates paclitaxel resistance in NSCLC via inhibiting CEMIP-mediated EMT

N6-methyladenosine (m6A) is the most prevalent mRNA modification, and it is verified to be closely correlated with cancer occurrence and progression. The m6A demethylase ALKBH5 (alkB homolog 5) is dysregulated in various cancers. However, the role and underlying mechanism of ALKBH5 in the pathogenesis and especially the chemo-resistance of non-small cell lung cancer (NSCLC) is poorly elucidated. The current study shows that ALKBH5 expression is reduced in paclitaxel (PTX) resistant NSCLC cells and down-regulation of ALKBH5 usually implies poor prognosis of NSCLC patients. Over-expression of ALKBH5 in PTX-resistant cells can suppress cell proliferation and enhance chemo-sensitivity, while knockdown of ALKBH5 exerts the opposite effect, which further supports the tumor suppressive role of ALKBH5. Over-expression of ALKBH5 can also reverse the epithelial-mesenchymal transition (EMT) process in PTX-resistant cancer cells. Mechanistically, data from RNA-seq, real-time PCR and western blotting indicate that CEMIP (cell migration inducing hyaluronidase 1), also known as KIAA1199, may be the downstream target of ALKBH5. Furthermore, ALKBH5 negatively regulates the CEMIP level by reducing the stability of CEMIP mRNA. Collectively, the current data demonstrate that the ALKBH5/CEMIP axis modulates the EMT process in NSCLC, which in turn regulates the chemo-sensitivity of cancer cells to PTX.

PIGT promotes cell growth, glycolysis, and metastasis in bladder cancer by modulating GLUT1 glycosylation and membrane trafficking

BACKGROUND

Bladder cancer is very common worldwide. PIGT is a subunit of the glycosylphosphatidylinositol transamidase which involves in tumorigenesis and invasiveness. m6A modification of mRNA has been linked to cell proliferation, tumor progression and other biological events. However, how PIGT is regulated and what is the function of PIGT in bladder cancer remains to be elucidated.

METHODS

PIGT was silenced or overexpressed to study its role in regulating bladder cancer. Cell proliferation and invasion were examined with the Cell Counting Kit-8, colony formation and Transwell assay, respectively. Cellular oxygen consumption rates or extracellular acidification rates were detected by a XF24 Analyzer. Quantitative RT-PCR and immunoblots were performed to detect mRNA and protein levels.

RESULTS

PIGT was overexpressed in bladder cancer. Silencing PIGT inhibited cell proliferation, oxidative phosphorylation, and glycolysis. Overexpressing PIGT promoted cell proliferation, oxidative phosphorylation, glycolysis in vitro and tumor metastasis in vivo by activating glucose transporter 1 (GLUT1). PIGT also promoted GLUT1 glycosylation and membrane trafficking. Wilms' tumor 1-associated protein (WTAP) mediated PIGT m6A modification, and m6A reader, insulin-like growth factor 2 mRNA-binding protein (IGF2BP2), binds to the methylated PIGT to promote the stability of PIGT, leading to up-regulation of PIGT.

CONCLUSION

WTAP mediates PIGT m6A modification to increase the stability of PIGT via the IGF2BP2, which enhances cell proliferation, glycolysis, and metastasis in bladder cancer by modulating GLUT1 glycosylation and membrane trafficking.

The role of m6A epigenetic modifications in tumor coding and non-coding RNA processing

BACKGROUND

Epigenetic modifications of RNA significantly contribute to the regulatory processes in tumors and have, thus, received considerable attention. The m6A modification, known as N6-methyladenosine, is the predominant epigenetic alteration found in both eukaryotic mRNAs and ncRNAs.

MAIN BODY

m6A methylation modifications are dynamically reversible and are catalyzed, removed, and recognized by the complex of m6A methyltransferase (MTases), m6A demethylase, and m6A methyl recognition proteins (MRPs). Published evidence suggests that dysregulated m6A modification results in abnormal biological behavior of mature mRNA, leading to a variety of abnormal physiological processes, with profound implications for tumor development in particular.

CONCLUSION

Abnormal RNA processing due to dysregulation of m6A modification plays an important role in tumor pathogenesis and potential mechanisms of action. In this review, we comprehensively explored the mechanisms by which m6A modification regulates mRNA and ncRNA processing, focusing on their roles in tumors, and aiming to understand the important regulatory function of m6A modification, a key RNA epigenetic modification, in tumor cells, with a view to providing theoretical support for tumor diagnosis and treatment. Video Abstract.

The role of N6-methyladenosine RNA modification in platinum resistance

N6-methyladenosine (m6A) RNA methylation, a dynamic regulator of transcript expression, plays a pivotal role in cancer by influencing diverse mRNA processes, including nuclear export, splicing, translation and decay. It intersects with cancer biology, impacting progression, treatment sensitivity and prognosis. Platinum-based compounds are essential in cancer treatment, while intrinsic or acquired resistance poses a formidable challenge, limiting therapeutic efficacy. Recent breakthroughs have established a direct association between m6A RNA methylation and platinum resistance in various cancer types. This review summarized related studies, aiming to provide profound insights into the interplay between m6A-associated regulation and platinum-resistance mechanisms in cancer. It explores therapeutic approaches, including personalized treatments based on m6A profiles, guiding future research to enhance clinical strategies for oncological prognostic outcomes.

Forkhead box proteins as the critical regulators of cisplatin response in tumor cells

Cisplatin (CDDP) is one of the most common chemotherapy drugs used in a wide range of cancer patients; however, there is a high rate of CDDP resistance among cancer patients. Considering the side effects of cisplatin in normal tissues, it is necessary to predict the CDDP response in cancer patients. Therefore, identifying the molecular mechanisms involved in CDDP resistance can help to introduce the prognostic markers. Several molecular mechanisms such as apoptosis inhibition, drug efflux, drug detoxification, and increased DNA repair are involved in CDDP resistance. Regarding the key role of transcription factors in regulation of many cellular processes related to drug resistance, in the present review, we discussed the role of Forkhead box (FOX) protein family in CDDP response. It has been reported that FOX proteins mainly promote CDDP resistance through the regulation of DNA repair, autophagy, epithelial-mesenchymal transition (EMT), and signaling pathways. Therefore, FOX proteins can be introduced as the prognostic markers to predict CDDP response in cancer patients. In addition, considering that oncogenic role of FOX proteins, the CDDP treatment along with FOX inhibition can be used as a therapeutic strategy in cancer patients.

Nuciferine Inhibits Oral Squamous Cell Carcinoma Partially through Suppressing the STAT3 Signaling Pathway

Oral squamous cell carcinoma (OSCC) poses a significant obstacle to the worldwide healthcare system. Discovering efficient and non-toxic medications is crucial for managing OSCC. Nuciferine, an alkaloid with an aromatic ring, is present in the leaves of Nelumbo nucifera. It has been proven to play a role in multiple biological processes, including the inhibition of inflammation, regulation of the immune system, formation of osteoclasts, and suppression of tumors. Despite the demonstrated inhibitory effects of nuciferine on different types of cancer, there is still a need for further investigation into the therapeutic effects and potential mechanisms of nuciferine in OSCC. Through a series of in vitro experiments, it was confirmed that nuciferine hindered the growth, movement, and infiltration, while enhancing the programmed cell death of OSCC cells. Furthermore, the administration of nuciferine significantly suppressed the signal transducer and activator of transcription 3 (STAT3) signaling pathway in comparison to other signaling pathways. Moreover, the activation of the STAT3 signaling pathway by colivelin resulted in the reversal of nuciferine-suppressed OSCC behaviors. In vivo, we also showed the anti-OSCC impact of nuciferine using the cell-based xenograft (CDX) model in nude mice. Nonetheless, colivelin diminished the tumor-inhibiting impact of nuciferine, suggesting that nuciferine might partially impede the advancement of OSCC by suppressing the STAT3 signaling pathway. Overall, this research could offer a fresh alternative for the pharmaceutical management of OSCC.

HPV E7-drived ALKBH5 promotes cervical cancer progression by modulating m6A modification of PAK5

Human papillomavirus (HPV) infection is a causative agent of cervical cancer (CC). N6-methyladenosine (m6A) modification is implicated in carcinogenesis and tumor progression. However, the involvement of m6A modification in HPV-involved CC remains unclear. Here we showed that HPV E6/7 oncoproteins affected the global m6A modification and E7 specifically promoted the expression of ALKBH5. We found that ALKBH5 was significantly upregulated in CC and might serve as a valuable prognostic marker. Forced expression of ALKBH5 enhanced the malignant phenotypes of CC cells. Mechanistically, we discovered that E7 increased ALKBH5 expression through E2F1-mediated activation of the H3K27Ac and H3K4Me3 histone modifications, as well as post-translational modification mediated by DDX3. ALKBH5-mediated m6A demethylation enhanced the expression of PAK5. The m6A reader YTHDF2 bound to PAK5 mRNA and regulated its stability in an m6A-dependent manner. Moreover, ALKBH5 promoted tumorigenesis and metastasis of CC by regulating PAK5. Overall, our findings herein demonstrate a significant role of ALKBH5 in CC progression in HPV-positive cells. Thus, we propose that ALKBH5 may serve as a prognostic biomarker and therapeutic target for CC patients.

ALKBH5 promotes hypopharyngeal squamous cell carcinoma apoptosis by targeting TLR2 in a YTHDF1/IGF2BP2-mediated manner

Hypopharyngeal squamous cell carcinoma (HPSCC) is one of the most aggressive cancers and is notorious for its extremely poor prognosis. However, very few molecular biological studies have been performed. As a novel method of epigenetic gene modulation, N6-methyladenosine (m6A) RNA modification occurs in HPSCC. The expression of the m6A demethylase AlkB homolog 5 (ALKBH5) is frequently downregulated in human HPSCC. Furthermore, we found that ALKBH5 impaired cell proliferation by regulating human Toll-like receptor 2 (TLR2) in an m6A-dependent manner in HPSCC cells. ALKBH5 decreased TLR2 m6A modification, which could be recognized by the m6A readers IGF2BP2 and YTHDF1. IGF2BP2 facilitates TLR2 mRNA stability, whereas YTHDF1 promotes TLR2 mRNA translation. The current work uncovered a critical function of ALKBH5 in TLR2 regulation and provides a novel role for m6A demethylation of mRNA in HPSCC. The inhibition of m6A modification of ALKBH5 in HPSCC deserves further clinical investigation.

The role of m6A methylation in therapy resistance in cancer

Cancer therapy resistance is the main cause of cancer treatment failure. The mechanism of therapy resistance is a hot topic in epigenetics. As one of the most common RNA modifications, N6-methyladenosine (m6A) is involved in various processes of RNA metabolism, such as stability, splicing, transcription, translation, and degradation. A large number of studies have shown that m6A RNA methylation regulates the proliferation and invasion of cancer cells, but the role of m6A in cancer therapy resistance is unclear. In this review, we summarized the research progress related to the role of m6A in regulating therapy resistance in cancers.

New advances into cisplatin resistance in head and neck squamous carcinoma: Mechanisms and therapeutic aspects

Head and neck squamous cell carcinoma (HNSCC) arises from the interplay of multiple factors, such as smoking, alcohol consumption, and viral infections. Cisplatin-based concurrent radiotherapy regimens represent the first-line treatment for advanced HNSCC cases. However, cisplatin resistance significantly contributes to poor prognoses in HNSCC patients, making it crucial to unravel the underlying mechanisms to overcome this resistance. The complexity of cisplatin resistance in HNSCC involves cancer stem cells, autophagy, epithelial-mesenchymal transition, drug efflux, and metabolic reprogramming. Recent advances in nanodrug delivery systems, combined with existing small-molecule inhibitors and innovative genetic technologies, have opened new therapeutic avenues for addressing cisplatin resistance in HNSCC. This review systematically summarizes research progress from the past five years on cisplatin resistance in HNSCC, with a particular focus on the roles of cancer stem cells and autophagy. Additionally, potential future treatment strategies to overcome cisplatin resistance are discussed, including the targeting of cancer stem cells or autophagy through nanoparticle-based drug delivery systems. Furthermore, the review highlights the prospects and challenges associated with nanodelivery platforms in addressing cisplatin resistance in HNSCC.

Characterization of the m6A regulator-mediated methylation modification patterns in oral squamous cell carcinoma

N⁶-methyladenosine (m⁶A) is a form of posttranscriptional modification that plays important roles in cancer including oral squamous cell carcinoma (OSCC). Most studies to date have focused on a limited number of regulators and oncogenic pathways, thus failing to provide comprehensive insight into the dynamic effects of m⁶A modification. In addition, the role of m⁶A modification in shaping immune cell infiltration in OSCC has yet to be clarified. This study was designed to assess m⁶A modification dynamics in OSCC and to understand how such modifications influence clinical immunotherapeutic treatment outcomes. m⁶A modification patterns linked with 23 m⁶A regulators were analyzed in 437 OSCC patients from TCGA and GEO cohorts. These patterns were then quantified through m⁶A score based on algorithms derived from a principal component analysis (PCA) approach. The m⁶A modification patterns of OSCC samples were grouped into two clusters based on the m⁶A regulators expression, and immune cell infiltration was linked with the 5-year survival outcomes of patients in these clusters. 1575 genes associated with OSCC patient prognosis were identified and used to re-cluster these samples into two groups. Patients in clusters exhibiting higher levels of m⁶A regulator expression exhibited poorer overall survival (OS), whereas patients with high m⁶A scores survived for longer (p < 0.001). The overall mortality rates in the groups of patients with low and high m⁶A scores were 55% and 40%, respectively, and the m⁶A score distributions in clusters of patients grouped by m⁶A modification patterns and gene expression further supported the link between a high m⁶A score and better prognostic outcomes. Immunophenoscore (IPS) values for patients in different m⁶A score groups suggested that the use of PD-1-specific antibodies or CTLA-4 inhibitors alone or in combination would yield superior treatment outcomes in patients in the high-m⁶A score group relative to the low-m⁶A score group. m⁶A modification patterns are relevant to heterogeneity in OSCC. Detailed analyses of m⁶A modification patterns may thus offer novel insight regarding immune cell infiltration within the OSCC tumor microenvironment, guiding novel efforts to provide patients with more effective immunotherapeutic interventions.

Cancer chemo-preventive role of grape seed oil and cisplatin as a combination adjuvant therapy in the treatment of tongue squamous cell carcinoma: A biological in-vitro study

OBJECTIVES

Grape seed oil (GSO) has recently gained popularity due to its anticancer properties. This study aimed to investigate the efficacy of combining cisplatin (CP) and GSO in tongue squamous cell carcinoma (TSCC) treatment.

METHODS

In this study, human tongue carcinoma cell line (HNO-97) was treated with CP and GSO alone or in combination. The effects of CP and GSO on cytotoxicity and cell cycle arrest were studied using the MTT assay and flowcytometry, respectively. The apoptotic markers, including p53 and caspase 8, were assessed using reverse-transcription polymerase chain reaction (RT-PCR), caspase 3 using immunohistochemistry, and the angiogenic marker vascular endothelial growth factor (VEGF) using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The IC50 drug concentrations were found to be 16.4 ug/mL of GSO and 2.18 ug/mL of CP. When compared to the untreated control group, the percentage of S phase cells and apoptotic cells was significantly higher in the GSO, CP, and GSO/CP combination therapy groups. Furthermore, p53, caspase 8, caspase 3 expression were significantly upregulated in the GSO-and CP-treated groups, with evident upregulation with GSO/CP combination therapy. However, VEGF levels were significantly lower in the GSO-, CP-, and combined GSO/CP-treated groups.

CONCLUSIONS

GSO has both an apoptotic and antiangiogenic effect in the treatment of TSCC, suggesting a new strategy for phytochemical-based combination therapy.

Tumour microenvironment and aberrant signaling pathways in cisplatin resistance and strategies to overcome in oral cancer

OBJECTIVE

Oral cancer is the sixteenth most prevalent cancer in the world and the third-most in India. Despite of several treatment modalities, the cure rate of oral cancer is still low due to drug resistance mechanisms, which are caused by many reasons. It is necessary to improve the existing treatment strategies and discover neoteric therapy to kill cancer cells, which will give oral cancer's cure rate more success. So this review aims to delineate the molecular mechanisms behind cisplatin resistance, specifically the role of the tumor microenvironment, extracellular vesicles, and altered signaling pathways and its overcoming strategies in oral cancer.

DESIGN

This review was designed by searching words like cancer, oral cancer, cisplatin-resistance, tumor microenvironment, aberrant signalings, and extracellular vesicles, overcoming strategies for cisplatin resistance in databases like PubMed, Google Scholar, web science, and Scopus. Data available in this review is from 2017 to 2021.

RESULTS

After searching too much data, we found these 98 data appropriate for our review. From these data, we found that tumor microenvironment, extracellular vesicles, and altered signaling pathways like PI3K/AKT, EGFR, NOTCH, Ras, PTEN, Nf-κβ, and Wnt signaling have a crucial role in resistance development towards cisplatin in oral cancer.

CONCLUSIONS

Lastly, this review explores the alternative strategies to overcome cisplatin resistance likely, the combination therapy and targeted therapy by combining more than one chemotherapeutic drug or inhibitors of signaling pathways and also by using nanoparticle loaded drugs that will reduce the drug efflux, which gives new treatment strategies.

RNA N6-methyladenosine modification in regulating cancer stem cells and tumor immune microenvironment and its implication for cancer therapy

Therapy resistance is a well-known phenomenon in cancer treatment. It can be intrinsic or acquired, accountable for frequent tumor relapse and death worldwide. The interplay between cancer cells and their neighboring environment can activate complex signaling mechanisms influencing epigenetic changes and maintain cancer cell survival leading to the malignant phenotype. Cancer stem cells (CSCs) are tumor-initiating cells (TICs) and constitute the primary source of drug resistance and tumor recurrence. Studies have shown that cancer cells exhibit dysregulated RNA N6-methyladenosine (m6A) "writers," "erasers," and "readers" levels after acquiring drug resistance. The present review provides novel insight into the role of m6A modifiers involved in CSC generation, cancer cell proliferation, and therapy resistance. m6A RNA modifications in the cross-talk between CSC and the tumor immune microenvironment (TIME) have also been highlighted. Further, we have discussed the therapeutic potential of targeting m6A machinery for cancer diagnosis and the development of new therapies for cancer treatment.

METTL3/14 and IL-17 signaling contribute to CEBPA-DT enhanced oral cancer cisplatin resistance

OBJECTIVES

Oral squamous cell carcinoma (OSCC) is the most common head and neck cancer. Chemotherapy has been recognized as an optional combination treatment, which enhance the overall survival of OSCC patients. However, the majority of patients would suffer therapeutic resistance, which led to the treatment failure and poor prognosis.

MATERIALS AND METHODS

To explore the mechanism of chemoresistance in OSCC, we first constructed two chemoresistant cell lines using Cal27 and HSC4. Then MeRIP sequencing together with bioinformatics analysis and a series of in vitro experiments were used to assess the possible regulation manner of RNA methylation on OSCC chemoresistance. Finally, xenograft models were constructed to confirm the relationship among OSCC chemoresistance.

RESULTS

METTL3/METTL14 upregulation could enhance OSCC chemoresistance. CEBPA-DT overexpression could regulate METTL3/METTL14 expression and further activate downstream BHLHB9. CEBPA-DT overexpression could inhibit the activity of IL-17 signaling, resulting in the homeostasis breakdown of immune infiltration and cytokine release. CEBPA-DT overexpression could significantly enhance chemoresistance through METTL3/METTL14/BHLHB9 in vivo, which accelerated the tumor growth.

CONCLUSIONS

Our results suggest that CEBPA-DT might regulate OSCC chemoresistance through BHLHB9 gene manipulated by METTL3/METTL14 as well as through IL-17 signaling inhibition, which may contribute to the assessment of potential therapeutic targets in OSCC chemoresistance.

RNA methylation and cellular response to oxidative stress-promoting anticancer agents

Disruption of the complex network that regulates redox homeostasis often underlies resistant phenotypes, which hinder effective and long-lasting cancer eradication. In addition, the RNA methylome-dependent control of gene expression also critically affects traits of cellular resistance to anti-cancer agents. However, few investigations aimed at establishing whether the epitranscriptome-directed adaptations underlying acquired and/or innate resistance traits in cancer could be implemented through the involvement of redox-dependent or -responsive signaling pathways. This is unexpected mainly because: i) the effectiveness of many anti-cancer approaches relies on their capacity to promote oxidative stress (OS); ii) altered redox milieu and reprogramming of mitochondrial function have been acknowledged as critical mediators of the RNA methylome-mediated response to OS. Here we summarize the current state of understanding on this topic, as well as we offer new perspectives that might lead to original approaches and strategies to delay or prevent the problem of refractory cancer and tumor recurrence.

Epitranscriptomics in the development, functions, and disorders of cancer stem cells

Biomolecular modifications play an important role in the development of life, and previous studies have investigated the role of DNA and proteins. In the last decade, with the development of sequencing technology, the veil of epitranscriptomics has been gradually lifted. Transcriptomics focuses on RNA modifications that affect gene expression at the transcriptional level. With further research, scientists have found that changes in RNA modification proteins are closely linked to cancer tumorigenesis, progression, metastasis, and drug resistance. Cancer stem cells (CSCs) are considered powerful drivers of tumorigenesis and key factors for therapeutic resistance. In this article, we focus on describing RNA modifications associated with CSCs and summarize the associated research progress. The aim of this review is to identify new directions for cancer diagnosis and targeted therapy.

The role of demethylase AlkB homologs in cancer

The AlkB family (ALKBH1-8 and FTO), a member of the Fe (II)- and α-ketoglutarate-dependent dioxygenase superfamily, has shown the ability to catalyze the demethylation of a variety of substrates, including DNA, RNA, and histones. Methylation is one of the natural organisms’ most prevalent forms of epigenetic modifications. Methylation and demethylation processes on genetic material regulate gene transcription and expression. A wide variety of enzymes are involved in these processes. The methylation levels of DNA, RNA, and histones are highly conserved. Stable methylation levels at different stages can coordinate the regulation of gene expression, DNA repair, and DNA replication. Dynamic methylation changes are essential for the abilities of cell growth, differentiation, and division. In some malignancies, the methylation of DNA, RNA, and histones is frequently altered. To date, nine AlkB homologs as demethylases have been identified in numerous cancers’ biological processes. In this review, we summarize the latest advances in the research of the structures, enzymatic activities, and substrates of the AlkB homologs and the role of these nine homologs as demethylases in cancer genesis, progression, metastasis, and invasion. We provide some new directions for the AlkB homologs in cancer research. In addition, the AlkB family is expected to be a new target for tumor diagnosis and treatment.

N6-methyladenosine (m6A) as a regulator of carcinogenesis and drug resistance by targeting epithelial-mesenchymal transition and cancer stem cells

Emergence of drug resistance to chemotherapeutic agents is the principal obstacle towards curative cancer treatment in human cancer patients. It is in an urgent to explore the underlying molecular mechanisms to overcome the drug resistance. N6-Methyladenosine (m6A) RNA modification is the most abundant reversible RNA modification and has emerged in recent years to regulate gene expression in eukaryotes. Recent evidence has identified m6A is associated with cancer pathogenesis and drug resistance, contributing to the self-renewal and differentiation of cancer stem cell, tumor epithelial-mesenchymal transition (EMT) and tumor metastasis. Here we reviewed up-to-date knowledge of the relationship between m6A modulation and drug resistance. Furthermore, we illustrated the underlying mechanisms of m6A modulation in drug resistance. Lastly, we discussed the regulation of m6A modulation in EMT and cancer stem cells. Hence, it will help to provide significant therapeutic strategies to overcome drug resistance for cancer patients by changing m6A-related proteins via targeting cancer stem cells and EMT-phenotypic cells.

Emerging roles of m6A RNA modification in cancer therapeutic resistance

Marvelous advancements have been made in cancer therapies to improve clinical outcomes over the years. However, therapeutic resistance has always been a major difficulty in cancer therapy, with extremely complicated mechanisms remain elusive. N6-methyladenosine (m6A) RNA modification, a hotspot in epigenetics, has gained growing attention as a potential determinant of therapeutic resistance. As the most prevalent RNA modification, m6A is involved in every links of RNA metabolism, including RNA splicing, nuclear export, translation and stability. Three kinds of regulators, "writer" (methyltransferase), "eraser" (demethylase) and "reader" (m6A binding proteins), together orchestrate the dynamic and reversible process of m6A modification. Herein, we primarily reviewed the regulatory mechanisms of m6A in therapeutic resistance, including chemotherapy, targeted therapy, radiotherapy and immunotherapy. Then we discussed the clinical potential of m6A modification to overcome resistance and optimize cancer therapy. Additionally, we proposed existing problems in current research and prospects for future research.

N6-methyladenosine demethylase FTO enhances chemo-resistance in colorectal cancer through SIVA1-mediated apoptosis

N6-methyladenosine (m6A) is the most pervasive RNA modification and is recognized as a novel epigenetic regulation in RNA metabolism. Although the m6A modification involves various physiological processes, its roles in drug resistance in colorectal cancer (CRC) still remain unknown. We analyzed the RNA expression profile of m6A/A (%) with MRM mass spectrometry in human 5-fluorouracil (5-FU)-resistant CRC tissues, and used the m6A RNA immunoprecipitation assay to validate the m6A-regulated target. Our results have shown that the m6A demethylase FTO was up-regulated in human primary and 5-FU-resistant CRC. Depletion of FTO decreased cell growth, colony formation and metastasis in 5-FU-resistant CRC cells in vitro and in vivo. Mechanistically, we identified SIVA1, a critical apoptotic gene, as a key downstream target of the FTO-mediated m6A demethylation. The m6A demethylation of SIVA1 at the CDS region induced its mRNA degradation via a YTHDF2-dependent mechanism. The SIVA1 levels were negatively correlated with the FTO levels in clinical CRC tissues. Notably, inhibition of FTO significantly reduced the tolerance of 5-FU in 5-FU-resistant CRC cells via the FTO-SIVA1 axis, whereas SIVA1-depletion could restore the m6A-dependent 5-FU sensitivity in CRC cells. In summary, our findings demonstrate a critical role of FTO as an m6A demethylase enhancing chemo-resistance in CRC cells, and suggest that FTO inhibition may restore the sensitivity of chemo-resistant CRC cells to 5-FU.

Long noncoding RNA RFPL1S-202 inhibits ovarian cancer progression by downregulating the IFN-β/STAT1 signaling

BACKGROUND

RFPL1S was first identified as one of the pseudogenes located in the intrachromosomal duplications within 22q12-13. Our previous study found that one of the predicted transcripts of lncRNA RFPL1S, ENST00000419368.1 (GRCh37/hg19), also named as RFPL1S-202 in Ensembl website, is significantly downregulated in the chemoresistant ovarian cancer cells. However, its function and underlying mechanism have not been studied.

METHODS

Quantitative Real-time PCR was used to analyze the expression. Cell Counting Kit-8, transwell, flow cytometry analysis and tail vein injected mouse model were used to test the function. RNA-sequencing, RNA pull down, western blot, ELISA and RNA-Binding Protein Immunoprecipitation were performed for studying the mechanism. 5' and 3' rapid amplification of complementary DNA ends were performed to analyze the full length of RFPL1S-202.

RESULTS

RFPL1S-202 is significantly downregulated in epithelial ovarian cancer tissues and cell lines. Gain- and loss-of-function study indicated that RFPL1S-202 could enhance cisplatin or paclitaxel in cytotoxicity, inhibit cell proliferation, invasion and migration of ovarian cancer cells in vitro, and inhibit the liver metastasis of ovarian cancer cells in vivo. Mechanistically, RFPL1S-202 could physically interact with DEAD-Box Helicase 3 X-linked (DDX3X) protein, and decrease the expression of p-STAT1 and the IFN inducible genes by increasing the m6A modification of IFNB1. RFPL1S-202 is a spliced and polyadenylated non-coding RNA with a full length of 1071 bp.

CONCLUSIONS

Our study suggested that the predicted lncRNA RFPL1S-202 exerts a tumor- suppressive function in oarian cancer chemoresistance and progression by interacting with DDX3X and down-regulating the IFN-β-STAT1 signaling pathway.

Classification and diagnostic prediction of breast cancer metastasis on clinical data using machine learning algorithms

Metastatic Breast Cancer (MBC) is one of the primary causes of cancer-related deaths in women. Despite several limitations, histopathological information about the malignancy is used for the classification of cancer. The objective of our study is to develop a non-invasive breast cancer classification system for the diagnosis of cancer metastases. The anaconda-Jupyter notebook is used to develop various python programming modules for text mining, data processing, and Machine Learning (ML) methods. Utilizing classification model cross-validation criteria, including accuracy, AUC, and ROC, the prediction performance of the ML models is assessed. Welch Unpaired t-test was used to ascertain the statistical significance of the datasets. Text mining framework from the Electronic Medical Records (EMR) made it easier to separate the blood profile data and identify MBC patients. Monocytes revealed a noticeable mean difference between MBC patients as compared to healthy individuals. The accuracy of ML models was dramatically improved by removing outliers from the blood profile data. A Decision Tree (DT) classifier displayed an accuracy of 83% with an AUC of 0.87. Next, we deployed DT classifiers using Flask to create a web application for robust diagnosis of MBC patients. Taken together, we conclude that ML models based on blood profile data may assist physicians in selecting intensive-care MBC patients to enhance the overall survival outcome.

A study of RNA m6A demethylases in oral epithelial dysplasia and oral squamous cell carcinoma

Purpose

N6-Methyladenosine (m6A) modification is involved in the tumorigenesis of various cancers. However, the roles of RNA m6A demethylases, fat mass and obesity-associated protein (FTO), and AlkB homolog 5 (ALKBH5) in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC) remain unclear. This study focuses on FTO and ALKBH5 expression by using immunohistochemistry.

Material and methods

Twenty specimens each of OED, OSCC, and normal oral mucosa (NOM) were included. The expression pattern, the number of positive cells, the cell-staining intensity, and the histochemical scoring (H-score) were examined and analyzed.

Results

In all the OED and OSCC specimens, FTO and ALKBH5 were mainly expressed with moderate to strong staining intensity in the nuclei of the abnormal epithelial cells, respectively. Regarding the NOM, both RNA demethylases showed mild cell staining intensity and was present in 50-60% of the specimens. Interestingly, the percentage of cell positivity, the cell-staining intensity, and the H-score of the FTO and ALKBH5 in NOM, OED, and OSCC were increased, respectively (p < 0.001). There was also a positive correlation between the FTO and ALKBH5 expressions in OSCC (r = 0.62, p = 0.003), but not in the NOM and OED.

Conclusion

These results suggest a possible prognostic role of FTO and ALKBH5 expression in the malignant transformation of OED and tumor progression. Further studies are needed to elucidate the mechanisms underlying the roles of FTO and ALKBH5 in carcinogenesis.

Emerging role of interaction between m6A and main ncRNAs in gastrointestinal (GI) cancers

As a prevalent epigenetic modification, the role of m6A has been increasingly highlighted in the alteration of numerous RNAs implicated with multiple biological processes, such as formation, export, translation, and degradation. With further the understanding of m6A, accumulating evidence shows that m6A modification similarly affects metabolic process of non-coding genes. But the specifical interplay of m6A and ncRNAs (non-coding RNAs) in gastrointestinal cancers still lacks complete discussion. Thus, we analyzed and summarized how ncRNAs affect the regulators of m6A and by what means the expression of ncRNAs is altered via m6A in gastrointestinal cancers. We focused on the effect of the interaction of m6A and ncRNAs on the molecular mechanisms of malignant behavior in gastrointestinal cancers, revealing more possibilities of ncRNAs for diagnosis and treatment in term of epigenetic modification.

Biological and pharmacological roles of m6A modifications in cancer drug resistance

Cancer drug resistance represents the main obstacle in cancer treatment. Drug-resistant cancers exhibit complex molecular mechanisms to hit back therapy under pharmacological pressure. As a reversible epigenetic modification, N⁶-methyladenosine (m⁶A) RNA modification was regarded to be the most common epigenetic RNA modification. RNA methyltransferases (writers), demethylases (erasers), and m⁶A-binding proteins (readers) are frequently disordered in several tumors, thus regulating the expression of oncoproteins, enhancing tumorigenesis, cancer proliferation, development, and metastasis. The review elucidated the underlying role of m⁶A in therapy resistance. Alteration of the m⁶A modification affected drug efficacy by restructuring multidrug efflux transporters, drug-metabolizing enzymes, and anticancer drug targets. Furthermore, the variation resulted in resistance by regulating DNA damage repair, downstream adaptive response (apoptosis, autophagy, and oncogenic bypass signaling), cell stemness, tumor immune microenvironment, and exosomal non-coding RNA. It is highlighted that several small molecules targeting m⁶A regulators have shown significant potential for overcoming drug resistance in different cancer categories. Further inhibitors and activators of RNA m⁶A-modified proteins are expected to provide novel anticancer drugs, delivering the therapeutic potential for addressing the challenge of resistance in clinical resistance.

Genomewide m6A Mapping Uncovers Dynamic Changes in the m6A Epitranscriptome of Cisplatin-Treated Apoptotic HeLa Cells

Cisplatin (CP), which is a conventional cancer chemotherapeutic drug, induces apoptosis by modulating a diverse array of gene regulatory mechanisms. However, cisplatin-mediated changes in the m⁶A methylome are unknown. We employed an m⁶A miCLIP-seq approach to investigate the effect of m⁶A methylation marks under cisplatin-mediated apoptotic conditions on HeLa cells. Our high-resolution approach revealed numerous m⁶A marks on 972 target mRNAs with an enrichment on 132 apoptotic mRNAs. We tracked the fate of differentially methylated candidate mRNAs under METTL3 knockdown and cisplatin treatment conditions. Polysome profile analyses revealed perturbations in the translational efficiency of PMAIP1 and PHLDA1 transcripts. Congruently, PMAIP1 amounts were dependent on METTL3. Additionally, cisplatin-mediated apoptosis was sensitized by METTL3 knockdown. These results suggest that apoptotic pathways are modulated by m⁶A methylation events and that the METTL3-PMAIP1 axis modulates cisplatin-mediated apoptosis in HeLa cells.

Ignored role of polyphenol in boosting reactive oxygen species generation for polyphenol/chemodynamic combination therapy

Chemodynamic therapy (CDT) is a promising tumor-specific treatment, but still suffering insufficient reactive oxygen species (ROS) levels due to its limited efficacy of Fenton/Fenton-like reaction. Polyphenol, as a natural reductant, has been applied to promote the efficacy of Fenton/Fenton-like reactions; however, its intrinsic pro-apoptosis effects was ignored. Herein, a novel CDT/polyphenol-combined strategy was designed, based on Avenanthramide C-loaded dendritic mesoporous silica (DMSN)-Au/Fe₃O₄ nanoplatforms with folic acid modification for tumor-site targeting. For the first time, we showed that the nanocomplex (DMSNAF-AVC-FA) induced ROS production in the cytoplasm via Au/Fe₃O₄-mediated Fenton reactions and externally damaged the mitochondrial membrane; simultaneously, the resultant increased mitochondrial membrane permeability can facilitate the migration of AVC into mitochondrial, targeting the DDX3 pathway and impairing the electron transport chain (ETC) complexes, which significantly boosted the endogenous ROS levels inside the mitochondrial. Under the elevated oxidative stress level via both intra- and extra-mitochondrial ROS production, the maximum mitochondrial membrane permeability was achieved by up-regulation of Bax/Bcl-2, and thereby led to massive release of Cytochrome C and maximum tumor cell apoptosis via Caspase-3 pathway. As a result, the as-designed strategy achieved synergistic cytotoxicity to 4T1 tumor cells with the cell apoptosis rate of 99.12% in vitro and the tumor growth inhibition rate of 63.3% in vivo, while very minor cytotoxicity to normal cells with cell viability of 95.4%. This work evidenced that natural bioactive compounds are powerful for synergistically boosting ROS level, providing new insight for accelerating the clinical conversion progress of CDT with minimal side effects.

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A novel CDT/polyphenol-combined nanoplatform, DMSNAF-AVC-FA was designed.

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DMSNAF-AVC-FA induced ROS production and externally damaged mitochondrial membrane.

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DMSNAF-AVC-FA facilitated AVC targeting the DDX3 pathway and impairing ETC complexes.

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DMSNAF-AVC-FA achieved synergistic antitumor efficacy both in vitro and in vivo.

RNA-binding proteins in regulating mRNA stability and translation: roles and mechanisms in cancer

RNA-binding proteins (RBPs) are key players in cellular physiology through posttranscriptional regulation of the expression of target RNA transcripts. By modulating the processing, stability and translation of cancer-related messenger RNA (mRNA) transcripts, a large set of RBPs play essential roles in various types of cancers. Perturbations in RBP activity have been causally associated with cancer development, tumor metabolism, drug resistance, cancer stem cell self-renewal, and tumor immune evasion. Here, we summarize the recent advances in cancer pathological roles and mechanisms of RBPs in regulating mRNA stability and translation with an emphasis on the emerging category of RNA modification-associated RBPs. The functional diversity of RBPs in different types of cancers and the therapeutic potential of targeting dysregulated RBPs for cancer treatment are also discussed.

METTL3/LINC00662/miR-186-5p feedback loop regulates docetaxel resistance in triple negative breast cancer

Insight into the mechanism of docetaxel resistance in breast cancer may help to improve prognosis. We aimed to investigate the role of N6-methyladenosine (m6A) and the METTL3/LINC00662/miR-186-5p pathway in regulating docetaxel resistance in triple negative breast cancer (TNBC). We have recruited 193 pathologically diagnosed TNBC patients from 2016 to 2017 in our hospital. Quantitative real-time PCR was used to evaluate the expression of LINC00662 and miR-186-5p both in vivo and in vitro. CCK8 tests were used to assess cell viability. ELISA was used for protein expression evaluation. Dual luciferase reporter gene assay and RNA pull-down were used to evaluate the interaction between LINC00662 and miR-186-5p. m6A levels were enhanced in breast cancer tissues and cells. LINC00662, miR-186-5p and METTL3 were differentially expressed in vivo, and METTL3 expression was associated with LINC00662 and miR-186-5p expression. LINC00662 and miR-186-5p were differentially expressed in vitro; LINC00662 promoted cell viability and decreased the apoptosis rate, whereas miR-186-5p inhibited cell viability and increased the apoptosis rate. Furthermore, we found that METTL3 regulated m6A levels in docetaxel-resistant breast cancer cells by regulating the expression of LINC00662. Moreover, LINC00662 and miR-186-5p regulated the cell viability rate of docetaxel-resistant breast cancer cells. Further experiments showed that LINC00662 directly interacted with miR-186-5p to exert biological functions; besides miR-186-5p could regulate the expression of METTL3. METTL3 promotes m6A levels and docetaxel resistance in breast cancer by regulating the expression of LINC00662 and miR-186-5p; more experiments are needed to clarify the role of m6A regulation in drug resistance.

CMTM6 attenuates cisplatin-induced cell death in OSCC by regulating AKT/c-Myc-driven ribosome biogenesis

CMTM6, a type 3 transmembrane protein, is known to stabilize the expression of programmed cell death ligand 1 (PD-L1) and hence facilitates the immune evasion of tumor cells. Recently, we demonstrated that CMTM6 is a major driver of cisplatin resistance in oral squamous cell carcinomas (OSCC). However, the detailed mechanism of how CMTM6 rewires cisplatin resistance in OSCC is yet to be explored. RNA sequencing analysis of cisplatin-resistant OSCC lines stably expressing Nt shRNA and CMTM6 shRNA revealed that CMTM6 might be a potential regulator of the ribosome biogenesis network. Knocking down CMTM6 significantly inhibited transcription of 47S precursor rRNA and hindered the nucleolar structure, indicating reduced ribosome biogenesis. When CMTM6 was ectopically over-expressed in CMTM6KD cells, almost all ribosomal machinery components were rescued. Mechanistically, CMTM6 induced the expression of C-Myc, which promotes RNA polymerase I mediated rDNA transcription. In addition to this, CMTM6 was also found to regulate the AKT-mTORC1-dependent ribosome biogenesis and protein synthesis in cisplatin-resistant lines. The nude mice and zebrafish xenograft experiments indicate that blocking ribosome synthesis either by genetic inhibitor (CMTM6KD) or pharmacological inhibitor (CX-5461) significantly restores cisplatin-mediated cell death in chemoresistant OSCC. Overall, our study suggests that CMTM6 is a major regulator of the ribosome biogenesis network and targeting the ribosome biogenesis network is a viable target to overcome chemoresistance in OSCC. The novel combination of CX-5461 and cisplatin deserves further clinical investigation in advanced OSCC.

Transcriptome-wide m6A methylome analysis uncovered the changes of m6A modification in oral pre-malignant cells compared with normal oral epithelial cells

As the most common post-transcriptional RNA modification, m⁶A methylation extensively regulates the structure and function of RNA. The dynamic and reversible modification of m⁶A is coordinated by m⁶A writers and erasers. m⁶A reader proteins recognize m⁶A modification on RNA, mediating different downstream biological functions. mRNA m⁶A modification and its corresponding regulators play an important role in cancers, but its characteristics in the precancerous stage are still unclear. In this study, we used oral precancerous DOK cells as a model to explore the characteristics of transcriptome-wide m⁶A modification and major m⁶A regulator expression in the precancerous stage compared with normal oral epithelial cell HOEC and oral cancer cell SCC-9 through MeRIP-seq and RT-PCR. Compared with HOEC cells, we found 1180 hyper-methylated and 1606 hypo-methylated m⁶A peaks and 354 differentially expressed mRNAs with differential m⁶A peaks in DOK cells. Although the change of m⁶A modification in DOK cells was less than that in SCC-9 cells, mRNAs with differential m⁶A in both cell lines were enriched into many identical GO terms and KEGG pathways. Among the 20 known m⁶A regulatory genes, FTO, ALKBH5, METTL3 and VIRMA were upregulated or downregulated in DOK cells, and the expression levels of 10 genes such as METTL14/16, FTO and IGF2BP2/3 were significantly changed in SCC-9 cells. Our data suggest that precancerous cells showed, to some extent, changes of m⁶A modification. Identifying some key m⁶A targets and corresponding regulators in precancerous stage may provide potential intervention targets for the prevention of cancer development through epigenetic modification in the future.

Multilevel regulation of N6-methyladenosine RNA modifications: Implications in tumorigenesis and therapeutic opportunities

N⁶-methyladenosine (m⁶A) RNA modification is widely perceived as the most abundant and common modification in transcripts. This modification is dynamically regulated by specific m⁶A "writers", "erasers" and "readers" and is reportedly involved in the occurrence and development of many diseases. Since m⁶A RNA modification was discovered in the 1970s, with the progress of relevant research technologies, an increasing number of functions of m⁶A have been reported, and a preliminary understanding of m⁶A has been obtained. In this review, we summarize the mechanisms through which m⁶A RNA modification is regulated from the perspectives of expression, posttranslational modification and protein interaction. In addition, we also summarize how external and internal environmental factors affect m⁶A RNA modification and its functions in tumors. The mechanisms through which m⁶A methylases, m⁶A demethylases and m⁶A-binding proteins are regulated are complicated and have not been fully elucidated. Therefore, we hope to promote further research in this field by summarizing these mechanisms and look forward to the future application of m⁶A in tumors.

Role of m6A writers, erasers and readers in cancer

The N(6)-methyladenosine (m6A) modification is the most pervasive modification of human RNAs. In recent years, an increasing number of studies have suggested that m6A likely plays important roles in cancers. Many studies have demonstrated that m6A is involved in the biological functions of cancer cells, such as proliferation, invasion, metastasis, and drug resistance. In addition, m6A is closely related to the prognosis of cancer patients. In this review, we highlight recent advances in understanding the function of m6A in various cancers. We emphasize the importance of m6A to cancer progression and look forward to describe future research directions.

TAB2 Promotes the Biological Functions of Head and Neck Squamous Cell Carcinoma Cells via EMT and PI3K Pathway

Background

Transforming growth factor β₁-activated kinase 1 binding protein 2 (TAB2) mediates a variety of biological processes through activated nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB) signaling pathways. TAB2 has been reported to be upregulated in a variety of tumors. However, little is known about its potential role in oral squamous cell carcinoma (OSCC). Material and Methods. Patients' clinicopathological and transcription data were obtained from The Cancer Genome Atlas (TCGA) database. Immunohistochemistry staining was used to determine TAB2 expression in OSCC tissues (IHC). The expression of TAB2 in OSCC cell lines was detected by western blotting. The CCK-8 test and flow cytometry assay were utilized to evaluate cell proliferation, apoptosis, and cell cycle in OSCC cell lines. Enrichment analysis and identification of predicted signaling pathways were performed by Gene Ontology and KEGG analysis. Finally, the expression of downstream signal molecules was performed using western blotting to validate the mechanism investigations.

Results

TAB2 expression level was aberrantly upregulated in OSCC patients. TAB2 expression was shown to be inversely associated to prognosis. The phenotypic of OSCC cells was considerably impacted by TAB2. OSCC cells with deleted TAB2 exhibit decreased proliferation and increased apoptosis. Additionally, OSCC progression is aided by TAB2 overexpression. Further mechanism studies showed that TAB2 could regulate the progression of OSCC by mediating the upregulation of EMT and PI3K-AKT signaling pathways.

Conclusion

This study sheds light on the carcinogenic role of TAB2 in OSCC and provides a potential therapeutic strategy.

Melatonin: Regulation of Viral Phase Separation and Epitranscriptomics in Post-Acute Sequelae of COVID-19

The relentless, protracted evolution of the SARS-CoV-2 virus imposes tremendous pressure on herd immunity and demands versatile adaptations by the human host genome to counter transcriptomic and epitranscriptomic alterations associated with a wide range of short- and long-term manifestations during acute infection and post-acute recovery, respectively. To promote viral replication during active infection and viral persistence, the SARS-CoV-2 envelope protein regulates host cell microenvironment including pH and ion concentrations to maintain a high oxidative environment that supports template switching, causing extensive mitochondrial damage and activation of pro-inflammatory cytokine signaling cascades. Oxidative stress and mitochondrial distress induce dynamic changes to both the host and viral RNA m6A methylome, and can trigger the derepression of long interspersed nuclear element 1 (LINE1), resulting in global hypomethylation, epigenetic changes, and genomic instability. The timely application of melatonin during early infection enhances host innate antiviral immune responses by preventing the formation of "viral factories" by nucleocapsid liquid-liquid phase separation that effectively blockades viral genome transcription and packaging, the disassembly of stress granules, and the sequestration of DEAD-box RNA helicases, including DDX3X, vital to immune signaling. Melatonin prevents membrane depolarization and protects cristae morphology to suppress glycolysis via antioxidant-dependent and -independent mechanisms. By restraining the derepression of LINE1 via multifaceted strategies, and maintaining the balance in m6A RNA modifications, melatonin could be the quintessential ancient molecule that significantly influences the outcome of the constant struggle between virus and host to gain transcriptomic and epitranscriptomic dominance over the host genome during acute infection and PASC.

Epitranscriptomics Changes the Play: m6A RNA Modifications in Apoptosis

Apoptosis is a form of programmed cell death that is essential for cellular and organismal homeostasis. Any irregularities that disturb the balance between apoptosis and cell survival have severe implications, such as improper development or life-threatening diseases. Thus, it is highly critical to maintain a proper rate of apoptosis throughout development. In fact, several complex transcriptional and posttranscriptional mechanisms exist in eukaryotes to critically regulate the rate of apoptotic processes. Recent studies suggest that not only RNA sequences but also their modifications, such as m⁶A methylation, play a fundamental role in these transcriptional and posttranscriptional processes. A specific set of proteins, called writer, eraser, and reader of m⁶A marks, modulate the rate of apoptosis by determining the m⁶A repertoire and the fate of certain transcripts associated with apoptosis. In this Review, we will cover the dynamic m⁶A RNA modifications and their impact on modulation of apoptosis.

RNA demethylase ALKBH5 regulates hypopharyngeal squamous cell carcinoma ferroptosis by posttranscriptionally activating NFE2L2/NRF2 in an m6 A-IGF2BP2-dependent manner

Background

Having emerged as the most abundant posttranscriptional internal mRNA modification in eukaryotes, N6‐methyladenosine (m⁶A) has attracted tremendous scientific interest in recent years. However, the functional importance of the m⁶A methylation machinery in ferroptosis regulation in hypopharyngeal squamous cell carcinoma (HPSCC) remains unclear.

Methods

We herein performed bioinformatic analysis, cell biological analyses, transcriptome‐wide m⁶A sequencing (m⁶A‐seq, MeRIP‐seq), RNA sequencing (RNA‐seq), and RNA immunoprecipitation sequencing (RIP‐seq), followed by m⁶A dot blot, MeRIP‐qPCR, RIP‐qPCR, and dual‐luciferase reporter assays.

Results

The results revealed that ALKBH5‐mediated m⁶A demethylation led to the posttranscriptional inhibition of NFE2L2/NRF2, which is crucial for the regulation of antioxidant molecules in cells, at two m⁶A residues in the 3′‐UTR. Knocking down ALKBH5 subsequently increased the expression of NFE2L2/NRF2 and increased the resistance of HPSCC cells to ferroptosis. In addition, m⁶A‐mediated NFE2L2/NRF2 stabilization was dependent on the m⁶A reader IGF2BP2. We suggest that ALKBH5 dysregulates NFE2L2/NRF2 expression in HPSCC through an m⁶A‐IGF2BP2‐dependent mechanism.

Conclusion

Together, these results have revealed an association between the ALKBH5‐NFE2L2/NRF2 axis and ferroptosis, providing insight into the functional importance of reversible mRNA m⁶A methylation and its modulators in HPSCC.

Recent Advances of m6A Demethylases Inhibitors and Their Biological Functions in Human Diseases

N6-methyladenosine (m6A) is a post-transcriptional RNA modification and one of the most abundant types of RNA chemical modifications. m6A functions as a molecular switch and is involved in a range of biomedical aspects, including cardiovascular diseases, the central nervous system, and cancers. Conceptually, m6A methylation can be dynamically and reversibly modulated by RNA methylation regulatory proteins, resulting in diverse fates of mRNAs. This review focuses on m6A demethylases fat-mass- and obesity-associated protein (FTO) and alkB homolog 5 (ALKBH5), which especially erase m6A modification from target mRNAs. Recent advances have highlighted that FTO and ALKBH5 play an oncogenic role in various cancers, such as acute myeloid leukemias (AML), glioblastoma, and breast cancer. Moreover, studies in vitro and in mouse models confirmed that FTO-specific inhibitors exhibited anti-tumor effects in several cancers. Accumulating evidence has suggested the possibility of FTO and ALKBH5 as therapeutic targets for specific diseases. In this review, we aim to illustrate the structural properties of these two m6A demethylases and the development of their specific inhibitors. Additionally, this review will summarize the biological functions of these two m6A demethylases in various types of cancers and other human diseases.

siRNA-mediated silencing of Nanog reduces stemness properties and increases the sensitivity of HepG2 cells to cisplatin

Liver cancer is one of the most lethal cancers having worldwide prevalence. Despite significant progress in cancer therapy, liver cancer-induced mortality is very high. Nanog, as an essential transcription factor modulating cellular multipotency, causes tumor progression, drug resistance, and preserves stemness properties in various tumors such as liver cancer. Thus, this research was conducted to evaluate the impact of combination therapy of Nanog siRNA/cisplatin on the sensitivity of liver cancer cells to this drug. HepG2 cells were transfected with Nanog siRNA and treated with cisplatin, individually and in combination. Then, it was observed that in transfected HepG2 cells, Nanog expression was significantly reduced at mRNA level and also these cells were sensitized to cisplatin. In addition, to assess the impact of Nanog siRNA and cisplatin individually and in combination on cells' viability, migration capacity, apoptosis, and cell cycle progression, the MTT, wound healing, colony formation assay, Annexin V/PI staining, and flow cytometry assays were applied on HepG2 cells, respectively. Also, the quantitive Real-Time PCR was used to check the expression of stemness-associated genes (CD44, CD133, and Sox2), and apoptosis-related genes (caspase-3, 8, 9, BAX and Bcl2) after combination therapy. It is indicated that the combination of Nanog siRNA and cisplatin significantly reduced proliferation, migration, and colony formation ability, as well as increased apoptosis rate, and cell cycle arrest. Also, it is found that the combination of Nanog siRNA and cisplatin down-regulated the expression of stemness-associated genes and up-regulated apoptosis-related genes in HepG2 cells. Hence, it can be suggested that Nanog inhibition in combination with cisplatin is a potential therapeutic strategy for developing new therapeutic approaches for liver cancer.

Detailed resume of RNA m6A demethylases

N6-Methyladenosine (m⁶A) is the most abundant internal modification in eukaryotic mRNA, playing critical role in various bioprocesses. Like other epigenetic modifications, m⁶A modification can be catalyzed by the methyltransferase complex and erased dynamically to maintain cells homeostasis. Up to now, only two m⁶A demethylases have been reported, fat mass and obesity-associated protein (FTO) and alkylation protein AlkB homolog 5 (ALKBH5), involving in a wide range of mRNA biological progress, including mRNA shearing, export, metabolism and stability. Furthermore, they participate in many significantly biological signaling pathway, and contribute to the progress and development of cancer along with other diseases. In this review, we focus on the studies about structure, inhibitors development and biological function of FTO and ALKBH5.

Role of main RNA modifications in cancer: N6-methyladenosine, 5-methylcytosine, and pseudouridine

Cancer is one of the major diseases threatening human life and health worldwide. Epigenetic modification refers to heritable changes in the genetic material without any changes in the nucleic acid sequence and results in heritable phenotypic changes. Epigenetic modifications regulate many biological processes, such as growth, aging, and various diseases, including cancer. With the advancement of next-generation sequencing technology, the role of RNA modifications in cancer progression has become increasingly prominent and is a hot spot in scientific research. This review studied several common RNA modifications, such as N⁶-methyladenosine, 5-methylcytosine, and pseudouridine. The deposition and roles of these modifications in coding and noncoding RNAs are summarized in detail. Based on the RNA modification background, this review summarized the expression, function, and underlying molecular mechanism of these modifications and their regulators in cancer and further discussed the role of some existing small-molecule inhibitors. More in-depth studies on RNA modification and cancer are needed to broaden the understanding of epigenetics and cancer diagnosis, treatment, and prognosis.

ALKBH5 promotes lung fibroblast activation and silica-induced pulmonary fibrosis through miR-320a-3p and FOXM1

Background

N⁶-methyladenosine (m⁶A) is the most common and abundant internal modification of RNA. Its critical functions in multiple physiological and pathological processes have been reported. However, the role of m⁶A in silica-induced pulmonary fibrosis has not been fully elucidated. AlkB homolog 5 (ALKBH5), a well-known m⁶A demethylase, is upregulated in the silica-induced mouse pulmonary fibrosis model. Here, we sought to investigate the function of ALKBH5 in pulmonary fibrosis triggered by silica inhalation.

Methods

We performed studies with fibroblast cell lines and silica-induced mouse pulmonary fibrosis models. The expression of ALKBH5, miR-320a-3p, and forkhead box protein M1 (FOXM1) was determined by quantitative real-time polymerase chain reaction (qRT-PCR) analysis. RNA immunoprecipitation (RIP) assays and m⁶A RNA immunoprecipitation assays (MeRIP), western bolt, immunofluorescence assays, and 5-ethynyl-2'-deoxyuridine (EdU) fluorescence staining were performed to explore the roles of ALKBH5, miR-320a-3p, and FOXM1 in fibroblast activation.

Results

ALKBH5 expression was increased in silica-inhaled mouse lung tissues and transforming growth factor (TGF)-β1-stimulated fibroblasts. Moreover, ALKBH5 knockdown exerted antifibrotic effects in vitro. Simultaneously, downregulation of ALKBH5 elevated miR-320a-3p but decreased pri-miR-320a-3p. Mechanically, ALKBH5 demethylated pri-miR-320a-3p, thus blocking the microprocessor protein DGCR8 from interacting with pri-miR-320a-3p and leading to mature process blockage of pri-miR-320a-3p. We further demonstrated that miR-320a-3p could regulate fibrosis by targeting FOXM1 messenger RNA (mRNA) 3′-untranslated region (UTR). Notably, our study also verified that ALKBH5 could also directly regulate FOXM1 in an m⁶A-dependent manner.

Conclusions

Our findings suggest that ALKBH5 promotes silica-induced lung fibrosis via the miR-320a-3p/FOXM1 axis or targeting FOXM1 directly. Approaches aimed at ALKBH5 may be efficacious in treating lung fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00329-5.

GSDME Is Related to Prognosis and Response to Chemotherapy in Oral Cancer

Gasdermin E (GSDME), as the major executive protein of pyroptosis, has been considered to be linked to antitumor immunity in recent years. However, the role of GSDME in oral squamous cell carcinoma (OSCC) remains to be elucidated. Here, by using a human OSCC tissue microarray, human OSCC tissue, and Tgfbr1/Pten conditional knockout mice, we found that GSDME was strongly expressed in OSCC and that GSDME expression in primary tumors was higher than that in metastatic lymph nodes. In addition, GSDME expression in OSCC was positively related to better prognosis. Moreover, GSDME-mediated pyroptosis occurred upon stimulation with chemotherapy drugs, and functional knockdown of GSDME attenuated the cisplatin-induced antitumor effect. Consistent with these results, bioinformatic analysis indicated that GSDME expression was positively correlated with the sensitivity of a number of antitumor drugs approved by the US Food and Drug Administration. Inhibition of GSDME expression by small interfering RNA in SCC7 cells significantly increased the expression of the cancer stem cell markers, CD44 and ALDH1. Furthermore, multiplexed immunohistochemistry and flow cytometry indicated that the expression of GSDME positively correlated with tumor-infiltrating CD8⁺ T cells, granzyme B, and M1 phenotype macrophages. Collectively, these findings demonstrated that GSDME is a potential positive prognostic factor of OSCC, and GSDME-mediated pyroptosis induced by chemotherapy plays a role in antitumor response.

FTO promotes Bortezomib resistance via m6A-dependent destabilization of SOD2 expression in multiple myeloma

Drug resistance is the main reason for the failure of Bortezomib (Bort) in the treatment of multiple myeloma (MM), which seriously affects the efficacy of Bort. Therefore, the exploration of Bort resistance to treat MM will be very beneficial. Thus, this study aims to study the function and mechanism of Fat mass and obesity associated (FTO) on the Bort resistance of MM. In the present study, we demonstrated that FTO promotes Bort resistance via m6A-dependent destabilization of SOD2 expression in MM. These findings may provide a substantial evidence for the Bort resistance in MM.