RNA demethylase ALKBH5 in cancer: from mechanisms to therapeutic potential

Ferroptosis: a critical mechanism of N6-methyladenosine modification involved in carcinogenesis and tumor progression

Ferroptosis is an iron-dependent regulatory cell necrosis induced by iron overload and lipid peroxidation. It occurs when multiple redox-active enzymes are ectopically expressed or show abnormal function. Hence, the precise regulation of ferroptosis-related molecules is mediated across multiple levels, including transcriptional, posttranscriptional, translational, and epigenetic levels. N6-methyladenosine (m6A) is a highly evolutionarily conserved epigenetic modification in mammals. The m6A modification is commonly linked to tumor proliferation, progression, and therapy resistance because it is involved in RNA metabolic processes. Intriguingly, accumulating evidence suggests that dysregulated ferroptosis caused by the m6A modification drives tumor development. In this review, we summarized the roles of m6A regulators in ferroptosis-mediated malignant tumor progression and outlined the m6A regulatory mechanism involved in ferroptosis pathways. We also analyzed the potential value and application strategies of targeting m6A/ferroptosis pathway in the clinical diagnosis and therapy of tumors.

Small molecules that regulate the N6-methyladenosine RNA modification as potential anti-cancer agents

Epitranscriptomics, the field of post-translational RNA modifications, is a burgeoning domain of research that has recently received significant attention for its role in multiple diseases, including cancer. N6-methyladenosine (m6A) is the most prominent post-translational RNA modification and plays a critical role in RNA transcription, processing, translation, and metabolism. The m6A modification is controlled by three protein classes known as writers (methyltransferases), erasers (demethylases), and readers (m6A-binding proteins). Each class of m6A regulatory proteins has been implicated in cancer initiation and progression. As such, many of these proteins have been identified as potential targets for anti-cancer chemotherapeutics. In this work, we provide an overview of the role m6A-regulating proteins play in cancer and discuss the current state of small molecule therapeutics targeting these proteins.

ALKBH5 modulates bone cancer pain in a rat model by suppressing NR2B expression

Currently, the clinical treatment of bone cancer pain (BCP) is mainly related to its pathogenesis. The aim of the present study was to elucidate the potential role of N6-methyladenosine (m6A) in BCP in the spinal cord dorsal root ganglia (DRG) of BCP rats and its specific regulatory mechanism in N-methyl-d-aspartate receptor subunit 2B (NR2B). A rat model of BCP was constructed by tibial injection of Walker256 cells, and ALKBH5 and NR2B expression in the spinal cord DRG was detected. ALKBH5 was silenced or overexpressed in PC12 cells to verify the regulatory effect of ALKBH5 on NR2B. The specific mechanism underlying the interaction between ALKBH5 and NR2B was investigated using methylated RNA immunoprecipitation and dual-luciferase reporter gene assays. The results showed increased expression of m6A, decreased expression of ALKBH5, and increased expression of NR2B in the DRG of the BCP rat model. Overexpression of ALKBH5 inhibited NR2B expression, whereas interference with ALKBH5 caused an increase in NR2B expression. In NR2B, interference with ALKBH5 caused an increase in m6A modification, which caused an increase in NR2B. Taken together, ALKBH5 affected the expression of NR2B by influencing the stability of the m6A modification site of central NR2B, revealing that ALKBH5 is a therapeutic target for BCP.

ALKBH5-mediated m6A modification of circFOXP1 promotes gastric cancer progression by regulating SOX4 expression and sponging miR-338-3p

Circular RNAs (circRNAs) have recently been suggested as potential functional modulators of cellular physiology processes in gastric cancer (GC). In this study, we demonstrated that circFOXP1 was more highly expressed in GC tissues. High circFOXP1 expression was positively associated with tumor size, lymph node metastasis, TNM stage, and poor prognosis in patients with GC. Cox multivariate analysis revealed that higher circFOXP1 expression was an independent risk factor for disease-free survival (DFS) and overall survival (OS) in GC patients. Functional studies showed that increased circFOXP1 expression promoted cell proliferation, cell invasion, and cell cycle progression in GC in vitro. In vivo, the knockdown of circFOXP1 inhibited tumor growth. Mechanistically, we observed ALKBH5-mediated m6A modification of circFOXP1 and circFOXP1 promoted GC progression by regulating SOX4 expression and sponging miR-338-3p in GC cells. Thus, our findings highlight that circFOXP1 could serve as a novel diagnostic and prognostic biomarker and potential therapeutic target for GC.

Iron metabolism: backfire of cancer cell stemness and therapeutic modalities

Cancer stem cells (CSCs), with their ability of self-renewal, unlimited proliferation, and multi-directional differentiation, contribute to tumorigenesis, metastasis, recurrence, and resistance to conventional therapy and immunotherapy. Eliminating CSCs has long been thought to prevent tumorigenesis. Although known to negatively impact tumor prognosis, research revealed the unexpected role of iron metabolism as a key regulator of CSCs. This review explores recent advances in iron metabolism in CSCs, conventional cancer therapies targeting iron biochemistry, therapeutic resistance in these cells, and potential treatment options that could overcome them. These findings provide important insights into therapeutic modalities against intractable cancers.

Effects and mechanisms of N6-methyladenosine RNA methylation in environmental pollutant-induced carcinogenesis

Environmental pollution, including air pollution, plastic contamination, and heavy metal exposure, is a pressing global issue. This crisis contributes significantly to pollution-related diseases and is a critical risk factor for chronic health conditions, including cancer. Mounting evidence underscores the pivotal role of N6-methyladenosine (m6A) as a crucial regulatory mechanism in pathological processes and cancer progression. Governed by m6A writers, erasers, and readers, m6A orchestrates alterations in target gene expression, consequently playing a vital role in a spectrum of RNA processes, covering mRNA processing, translation, degradation, splicing, nuclear export, and folding. Thus, there is a growing need to pinpoint specific m6A-regulated targets in environmental pollutant-induced carcinogenesis, an emerging area of research in cancer prevention. This review consolidates the understanding of m6A modification in environmental pollutant-induced tumorigenesis, explicitly examining its implications in lung, skin, and bladder cancer. We also investigate the biological mechanisms that underlie carcinogenesis originating from pollution. Specific m6A methylation pathways, such as the HIF1A/METTL3/IGF2BP3/BIRC5 network, METTL3/YTHDF1-mediated m6A modification of IL 24, METTL3/YTHDF2 dynamically catalyzed m6A modification of AKT1, METTL3-mediated m6A-modified oxidative stress, METTL16-mediated m6A modification, site-specific ATG13 methylation-mediated autophagy, and the role of m6A in up-regulating ribosome biogenesis, all come into play in this intricate process. Furthermore, we discuss the direction regarding the interplay between pollutants and RNA metabolism, particularly in immune response, providing new information on RNA modifications for future exploration.

Geniposide reduced oxidative stress-induced apoptosis in HK-2 cell through PI3K/AKT3/FOXO1 by m6A modification

Exogenous hydrogen peroxide (H2O2) may generate excessive oxidative stress, inducing renal cell apoptosis related with kidney dysfunction. Geniposide (GP) belongs to the iridoid compound with anti-inflammatory, antioxidant and anti-apoptotic effects. This study aimed to observe the intervention effect of GP on H2O2-induced apoptosis in human kidney-2 (HK-2) cells and to explore its potential mechanism in relation to N6-methyladenosine (m6A) RNA methylation. Cell viability, apotosis rate and cell cycle were tested separately after different treatments. The mRNA and protein levels of m6A related enzymes and phosphoinositide 3-kinase (PI3K)/a serine/threonine-specific protein kinase 3 (AKT3)/forkhead boxo 1 (FOXO1) and superoxide dismutase 2 (SOD2) were detected by reverse transcription-quantitative real-time PCR (RT-qPCR) and Western blot. The whole m6A methyltransferase activity and the m6A content were measured by ELISA-like colorimetric methods. The changes of m6A methylation levels of PI3K/AKT3/FOXO1 and SOD2 were determined by methylated RNA immunoprecipitation (MeRIP)-qPCR. Multiple comparisons were performed by ANOVA with Turkey's post hoc test. Exposed to 400 μmol/L H2O2, cells were arrested in G1 phase and the apoptosis rate increased, which were significantly alleviated by GP. Compared with the H2O2 apoptosis group, both the whole m6A RNA methyltransferase activity and the m6A contents were increased due to GP intervention. Besides, the SOD2 protein was increased, while PI3K and FOXO1 decreased. The m6A methylation level of AKT3 was negatively correlated with its protein level. Taken together, GP affects the global m6A methylation microenvironment and regulates the expression of PI3K/AKT3/FOXO1 signaling pathway via m6A modification, alleviating cell cycle arrest and apoptosis caused by oxidative stress in HK-2 cells with a good application prospect.

A comprehensive review of m6A research in cervical cancer

Cervical cancer (CC) remains one of the most common malignancies among women worldwide, posing a serious threat to women's health. N6-methyladenosine (m6A) modification, as the most abundant type of RNA methylation modification, and has been found to play a crucial role in various cancers. Current research suggests a close association between RNA m6A modification and the occurrence and progression of CC, encompassing disruptions in m6A levels and its regulatory machinery. This review summarizes the current status of m6A modification research in CC, explores the mechanisms underlying m6A levels and regulators (methyltransferases, demethylases, reader proteins) in CC and examines the application of small-molecule inhibitors of m6A regulators in disease treatment. The findings provide new insights into the future treatment of CC.

Overexpression of YTHDF3 increases the specific productivity of the recombinant protein in CHO cells by promoting the translation process

Due to their high-quality characteristics, Chinese hamster ovary (CHO) cells have become the most widely used and reliable host cells for the production of recombinant therapeutic proteins in the biomedical field. Previous studies have shown that the m6A reader YTHDF3, which contains the YTH domain, can affect a variety of biological processes by regulating the translation and stability of target mRNAs. This study investigates the effect of YTHDF3 on transgenic CHO cells. The results indicate that stable overexpression of YTHDF3 significantly enhances recombinant protein expression without affecting host cell growth. Transcriptome sequencing indicated that several genes, including translation initiation factor, translation extension factor, and ribosome assembly factor, were upregulated in CHO cells overexpressing YTHDF3. In addition, cycloheximide experiments confirmed that YTHDF3 enhanced transgene expression by promoting translation in CHO cells. In conclusion, the findings in this study provide a novel approach for mammalian cell engineering to increase protein productivity by regulating m6A.

Arginine methylation of ALKBH5 by PRMT6 promotes breast tumorigenesis via LDHA-mediated glycolysis

ALKBH5 is a master regulator of N6-methyladenosine (m6A) modification, which plays a crucial role in many biological processes. Here, we show that ALKBH5 is required for breast tumor growth. Interestingly, PRMT6 directly methylates ALKBH5 at R283, which subsequently promotes breast tumor growth. Furthermore, arginine methylation of ALKBH5 by PRMT6 increases LDHA RNA stability via m6A demethylation, leading to increased aerobic glycolysis. Moreover, PRMT6-mediated ALKBH5 arginine methylation is confirmed in PRMT6-knockout mice. Collectively, these findings identify a PRMT6-ALKBH5-LDHA signaling axis as a novel target for the treatment of breast cancer.

ALKBH5 suppresses autophagic flux via N6-methyladenosine demethylation of ZKSCAN3 mRNA in acute pancreatitis

BACKGROUND

Increasing evidence has demonstrated that N6-methyladenosine (m6A) RNA modification plays an essential role in a wide range of pathological conditions. Impaired autophagy is a critical hallmark of acute pancreatitis (AP).

AIM

To explore the role of the m6A modification of ZKSCAN3 in the regulation of autophagy in AP.

METHODS

The AP mouse cell model was established by cerulein-treated mouse pancreatic acinar cells (MPC-83), and the results were confirmed by the levels of amylase and inflammatory factors. Autophagy activity was evaluated by specific identification of the autophagy-related microstructure and the expression of autophagy-related genes. ZKSCAN3 and ALKBH5 were knocked down to study the function in AP. A m6A RNA binding protein immunoprecipitation assay was used to study how the m6A modification of ZKSCAN3 mRNA is regulated by ALKBH.

RESULTS

The increased expression of amylase and inflammatory factors in the supernatant and the accumulation of autophagic vacuoles verified that the AP mouse cell model was established. The downregulation of LAMP2 and upregulation of LC3-II/I and SQSTM1 demonstrated that autophagy was impaired in AP. The expression of ZKSCAN3 was upregulated in AP. Inhibition of ZKSCAN3 increased the expression of LAMP2 and decreased the expression of the inflammatory factors, LC3-II/I and SQSTM1. Furthermore, ALKBH5 was upregulated in AP. Knockdown of ALKBH5 downregulated ZKSCAN3 expression and restored decreased autophagic flux in AP. Notably, the bioinformatic analysis revealed 23 potential m6A modification sites on ZKSCAN3 mRNA. The m6A modification of ZKSCAN3 mRNA was significantly decreased in AP. Knockdown of ALKBH5 increased the modification of ZKSCAN3 mRNA, which confirmed that ALKBH5 upregulated ZKSCAN3 expression in a m6A-dependent manner.

CONCLUSION

ALKBH5 inhibits autophagic flux through m6A demethylation of ZKSCAN3 mRNA in AP, thereby aggravating the severity of the disease.

N6-methyladenosine-induced METTL1 promotes tumor proliferation via CDK4

N6-methyladenosine (m6A) and N7-methylguanosine (m7G) modification of RNA represent two major intracellular post-transcriptional regulation modes of gene expression. However, the crosstalk of these two epigenetic modifications in tumorigenesis remain poorly understood. Here, we show that m6A methyltransferase METTL3-mediated METTL1 promotes cell proliferation of head and neck squamous cell carcinoma (HNSC) through m7G modification of the cell-cycle regulator CDK4. By mining the database GEPIA, METTL1 was shown to be up-regulated in a broad spectrum of human cancers and correlated with patient clinical outcomes, particularly in HNSC. Mechanistically, METTL3 methylates METTL1 mRNA and mediates its elevation in HNSC via m6A. Functionally, over-expression of METTL1 enhances HNSC cell growth and facilitates cell-cycle progress, while METTL1 knockdown represses these biological behaviors. Moreover, METTL1 physically binds to CDK4 transcript and regulates its m7G modification level to stabilize CDK4. Importantly, the inhibitory effects of METTL1 knockdown on the proliferation of HNSC, esophageal cancer (ESCA), stomach adenocarcinoma (STAD), and colon adenocarcinoma (COAD) were significantly mitigated by over-expression of CDK4. Taken together, this study expands the understanding of epigenetic mechanisms involved in tumorigenesis and identifies the METTL1/CDK4 axis as a potential therapeutic target for digestive system tumors.

FSH induces EMT in ovarian cancer via ALKBH5-regulated Snail m6A demethylation

Background: The therapeutic benefits of targeting follicle-stimulating hormone (FSH) receptor in treatment of ovarian cancer are significant, whereas the role of FSH in ovarian cancer progresses and the underlying mechanism remains to be developed. Methods: Tissue microarray of human ovarian cancer, tumor xenograft mouse model, and in vitro cell culture were used to investigate the role of FSH in ovarian carcinogenesis. siRNA, lentivirus and inhibitors were used to trigger the inactivation of genes, and plasmids were used to increase transcription of genes. Specifically, pathological characteristic was assessed by histology and immunohistochemistry (IHC), while signaling pathway was studied using western blot, quantitative RT-PCR, and immunofluorescence. Results: Histology and IHC of human normal ovarian and tumor tissue confirmed the association between FSH and Snail in ovarian cancer metastasis. Moreover, in epithelial ovarian cancer cells and xenograft mice, FSH was showed to promote epithelial mesenchymal transition (EMT) progress and metastasis of ovarian cancer via prolonging the half-life of Snail mRNA in a N6-methyladenine methylation (m6A) dependent manner, which was mechanistically through the CREB/ALKBH5 signaling pathway. Conclusions: These findings indicated that FSH induces EMT progression and ovarian cancer metastasis via CREB/ALKBH5/Snail pathway. Thus, this study provided new insight into the therapeutic strategy of ovarian cancer patients with high level of FSH.

Rewiring of RNA methylation by the oncometabolite fumarate in renal cell carcinoma

Metabolic reprogramming is a hallmark of cancer that facilitates changes in many adaptive biological processes. Mutations in the tricarboxylic acid cycle enzyme fumarate hydratase (FH) lead to fumarate accumulation and cause hereditary leiomyomatosis and renal cell cancer (HLRCC). HLRCC is a rare, inherited disease characterized by the development of non-cancerous smooth muscle tumors of the uterus and skin, and an increased risk of an aggressive form of kidney cancer. Fumarate has been shown to inhibit 2-oxoglutarate-dependent dioxygenases (2OGDDs) involved in the hydroxylation of HIF1α, as well as in DNA and histone demethylation. However, the link between fumarate accumulation and changes in RNA post-transcriptional modifications has not been defined. Here, we determine the consequences of fumarate accumulation on the activity of different members of the 2OGDD family targeting RNA modifications. By evaluating multiple RNA modifications in patient-derived HLRCC cell lines, we show that mutation of FH selectively affects the levels of N6-methyladenosine (m6A), while the levels of 5-formylcytosine (f5C) in mitochondrial tRNA are unaffected. This supports the hypothesis of a differential impact of fumarate accumulation on distinct RNA demethylases. The observation that metabolites modulate specific subsets of RNA-modifying enzymes offers new insights into the intersection between metabolism and the epitranscriptome.

Role of m6A RNA Methylation in Ischemic Stroke

Ischemic stroke is a prominent contributor to global morbidity and mortality rates. The intricate and diverse mechanisms underlying ischemia-reperfusion injury remain poorly comprehended. RNA methylation, an emerging epigenetic modification, plays a crucial role in regulating numerous biological processes, including immunity, DNA damage response, tumorigenesis, metastasis, stem cell renewal, adipocyte differentiation, circadian rhythms, cellular development and differentiation, and cell division. Among the various RNA modifications, N6-methyladenosine (m6A) modification stands as the most prevalent in mammalian mRNA. Recent studies have demonstrated the crucial involvement of m6A modification in the pathophysiological progression of ischemic stroke. This review aims to elucidate the advancements in ischemic stroke-specific investigations pertaining to m6A modification, consolidate the underlying mechanisms implicated in the participation of m6A modification during the onset of ischemic stroke, and deliberate on the potential of m6A modification as a viable therapeutic target for ischemic stroke.

Significance of N6-methyladenosine RNA methylation regulators in diagnosis and subtype classification of primary Sjögren's syndrome

The importance of N6-methyladenine (m6A) in mRNA metabolism, physiology, pathology and other life processes is well recognized. However, the exact role of m6A regulators in primary Sjögren's syndrome (PSS) remains unclear. In this study, we used bioinformatics and machine learning random forest approach to screen eight key m6A regulators from the Gene Expression Omnibus GSE7451, GSE40611 and GSE84844 datasets. An accurate nomogram model for predicting PSS risk was established based on these regulators. And using consensus clustering, patients diagnosed with PSS were classified into two different m6A patterns. We found that patients in group B had higher m6A scores compared to those in group A: furthermore, both groups were closely related to immunity and possibly to other diseases. These results emphasise the important role of m6A regulators in the pathogenesis of PSS. Our study of m6A patterns may inform future immunotherapy strategies for PSS.

ALKBH5 promotes the development of lung adenocarcinoma by regulating the polarization of M2 macrophages through CDCA4

OBJECTIVE

Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer, with high morbidity and mortality. N6-methyladenosine (m6A) is an important regulator of LUAD progression. Here, we investigated the potential biological functions of ALKBH5 (a m6A demethylated enzyme) and cell division cycle associated protein 4 (CDCA4) in the progression of LUAD.

METHODS

The expressions of CDCA4, METTL3, ALKBH5, FTO, YTHDC2 and YTHDC1 mRNA and proteins in LUAD and adjacent tissues, as well as NCI-H1299 and NCI-H157 cells were detected by RT-qPCR and western blot. Meanwhile, the role of ALKBH5 and CDCA4 in macrophage polarization was explored through tumor formation in Lewis lung carcinoma (LLC) mice and the co-culture system of NCI-H1299 and NCI-H157/THP-1 cells. Cell characterization was further analyzed. The expression of Ki-67 in tumor tissue was tested by immunohistochemistry. The scale of M1 and M2 macrophages was determined by flow cytometry.

RESULTS

CDCA4 was significantly overexpressed in NCI-H1299 and NCI-H157 cell lines compared with BEAS-2B cells. The fold enrichment of CDCA4 m6A level in the overexpression (oe)-METTL3 or short hairpin (sh)-ALKBH5 cells was enhanced. Overexpression of CDCA4 promoted the cell viability, proliferation and migration, and inhibited apoptosis, which was reversed by sh-ALKBH5 intervention. Overexpression of YTHDC2 (not YTHDC1) inhibited the effect of CDCA4 on sh-ALKBH5 cells. sh-CDCA4 inhibited tumor growth and weight of LLC cells in mice, and promoted M1/M2 ratio in LLC mice and NCI-H1299/THP-1 and NCI-H157/THP-1 co-culture systems. Oe-CDCA4 promoted the volume and weight of tumor and inhibited the M1/M2 ratio of tumor tissue in LLC mice, but was reversed by sh-ALKBH5 intervention.

CONCLUSION

m6A demethylase ALKBH5 promotes the development of LUAD through CDCA4 regulation of malignant characterization and M1/M2 macrophage polarization.

Emerging role of RNA modification and long noncoding RNA interaction in cancer

RNA modification, especially N6-methyladenosine, 5-methylcytosine, and N7-methylguanosine methylation, participates in the occurrence and progression of cancer through multiple pathways. The function and expression of these epigenetic regulators have gradually become a hot topic in cancer research. Mutation and regulation of noncoding RNA, especially lncRNA, play a major role in cancer. Generally, lncRNAs exert tumor-suppressive or oncogenic functions and its dysregulation can promote tumor occurrence and metastasis. In this review, we summarize N6-methyladenosine, 5-methylcytosine, and N7-methylguanosine modifications in lncRNAs. Furthermore, we discuss the relationship between epigenetic RNA modification and lncRNA interaction and cancer progression in various cancers. Therefore, this review gives a comprehensive understanding of the mechanisms by which RNA modification affects the progression of various cancers by regulating lncRNAs, which may shed new light on cancer research and provide new insights into cancer therapy.

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.

The promotive role of lncRNA MIR205HG in proliferation, invasion, and migration of melanoma cells via the JMJD2C/ALKBH5 axis

Melanoma is a highly malignant skin cancer. This study aimed to investigate the role of long non-coding RNA MIR205 host gene (lncRNA MIR205HG) in proliferation, invasion, and migration of melanoma cells via jumonji domain containing 2C (JMJD2C) and ALKB homolog 5 (ALKBH5). Real-time quantitative polymerase chain reaction or Western blot assay showed that MIR205HG, JMJD2C, and ALKBH5 were increased in melanoma cell lines. Cell counting kit-8, colony formation, and Transwell assays showed that silencing MIR205HG inhibited proliferation, invasion, and migration of melanoma cells. RNA immunoprecipitation, actinomycin D treatment, and chromatin immunoprecipitation showed that MIR205HG may bind to human antigen R (HuR, ELAVL1) and stabilized JMJD2C expression, and JMJD2C may increase the enrichment of H3K9me3 in the ALKBH5 promotor region to promote ALKBH5 transcription. The tumor xenograft assay based on subcutaneous injection of sh-MIR205HG-treated melanoma cells showed that silencing MIR205HG suppressed tumor growth and reduced Ki67 positive rate by inactivating the JMJD2C/ALKBH5 axis. Generally, MIR205HG facilitated proliferation, invasion, and migration of melanoma cells through HuR-mediated stabilization of JMJD2C and increasing ALKBH5 transcription by erasing H3K9me3.

RNA m6A methylation regulators in liver cancer

Liver cancer is one of the most common cancers in the world and a primary cause of cancer-related death. In recent years, despite the great development of diagnostic methods and targeted therapies for liver cancer, the incidence and mortality of liver cancer are still on the rise. As a universal post-transcriptional modification, N6-methyladenosine (m6A) modification accomplishes a dynamic and reversible m6A modification process, which is executed by three types of regulators, methyltransferases (called writers), demethylases (called erasers) and m6A-binding proteins (called readers). Many studies have shown that m6A RNA methylation has an important impact on RNA metabolism, whereas its regulation exception is bound up with the occurrence of human malignant tumors. Aberrant methylation of m6A RNA and the expression of related regulatory factors may be of the essence in the pathogenesis and progression of liver cancer, yet the precise molecular mechanism remains unclear. In this paper, we review the current research situations of m6A methylation in liver cancer. Among the rest, we detail the mechanism by which methyltransferases, demethylases and m6A binding proteins regulate the occurrence and development of liver cancer by modifying mRNA. As well as the potential effect of m6A regulators in hepatocarcinogenesis and progression. New ideas and approaches will be given to the prevention and treatment of liver cancer through the following relevant research results.

Emerging role of N6-methyladenosine in the homeostasis of glucose metabolism

N6-methyladenosine (m6A) is the most prevalent post-transcriptional internal RNA modification, which is involved in the regulation of diverse physiological processes. Dynamic and reversible m6A modification has been shown to regulate glucose metabolism, and dysregulation of m6A modification contributes to glucose metabolic disorders in multiple organs and tissues including the pancreas, liver, adipose tissue, skeletal muscle, kidney, blood vessels, and so forth. In this review, the role and molecular mechanism of m6A modification in the regulation of glucose metabolism were summarized, the potential therapeutic strategies that improve glucose metabolism by targeting m6A modifiers were outlined, and feasible directions of future research in this field were discussed as well, providing clues for translational research on combating metabolic diseases based on m6A modification in the future.

Discovery of Pyrazolo[1,5-a]pyrimidine Derivative as a Novel and Selective ALKBH5 Inhibitor for the Treatment of AML

M6A (N6-methyladenosine) plays a significant role in regulating RNA processing, splicing, nucleation, translation, and stability. AlkB homologue 5 (ALKBH5) is an Fe(II)/2-oxoglutarate (2-OG)-dependent dioxygenase that demethylates mono- or dimethylated adenosines. ALKBH5 can be regarded as an oncogenic factor for various human cancers. However, the discovery of potent and selective ALKBH5 inhibitors remains a challenge. We identified DDO-2728 as a novel and selective inhibitor of ALKBH5 by structure-based virtual screening and optimization. DDO-2728 was not a 2-oxoglutarate analogue and could selectively inhibit the demethylase activity of ALKBH5 over FTO. DDO-2728 increased the abundance of m6A modifications in AML cells, reduced the mRNA stability of TACC3, and inhibited cell cycle progression. Furthermore, DDO-2728 significantly suppressed tumor growth in the MV4-11 xenograft mouse model and showed a favorable safety profile. Collectively, our results highlight the development of a selective probe for ALKBH5 that will pave the way for the further study of ALKBH5 targeting therapies.

Captive ERVWE1 triggers impairment of 5-HT neuronal plasticity in the first-episode schizophrenia by post-transcriptional activation of HTR1B in ALKBH5-m6A dependent epigenetic mechanisms

BACKGROUND

Abnormalities in the 5-HT system and synaptic plasticity are hallmark features of schizophrenia. Previous studies suggest that the human endogenous retrovirus W family envelope (ERVWE1) is an influential risk factor for schizophrenia and inversely correlates with 5-HT4 receptor in schizophrenia. To our knowledge, no data describes the effect of ERVWE1 on 5-HT neuronal plasticity. N6-methyladenosine (m6A) regulates gene expression and impacts synaptic plasticity. Our research aims to systematically investigate the effects of ERVWE1 on 5-HT neuronal plasticity through m6A modification in schizophrenia.

RESULTS

HTR1B, ALKBH5, and Arc exhibited higher levels in individuals with first-episode schizophrenia compared to the controls and showed a strong positive correlation with ERVWE1. Interestingly, HTR1B was also correlated with ALKBH5 and Arc. Further analyses confirmed that ALKBH5 may be an independent risk factor for schizophrenia. In vitro studies, we discovered that ERVWE1 enhanced HTR1B expression, thereby activating the ERK-ELK1-Arc pathway and reducing the complexity and spine density of 5-HT neurons. Furthermore, ERVWE1 reduced m6A levels through ALKBH5 demethylation. ERVWE1 induced HTR1B upregulation by improving its mRNA stability in ALKBH5-m6A-dependent epigenetic mechanisms. Importantly, ALKBH5 mediated the observed alterations in 5-HT neuronal plasticity induced by ERVWE1.

CONCLUSIONS

Overall, HTR1B, Arc, and ALKBH5 levels were increased in schizophrenia and positively associated with ERVWE1. Moreover, ALKBH5 was a novel risk gene for schizophrenia. ERVWE1 impaired 5-HT neuronal plasticity in ALKBH5-m6A dependent mechanism by the HTR1B-ERK-ELK1-Arc pathway, which may be an important contributor to aberrant synaptic plasticity in schizophrenia.

Chemical Inhibitors Targeting the Oncogenic m6A Modifying Proteins

Epigenetics is brought to RNA, introducing a new dimension to gene expression regulation. Among numerous RNA modifications, N6-methyladenosine (m6A) is an abundant internal modification on eukaryote mRNA first identified in the 1970s. However, the significance of m6A modification in mRNA had been long neglected until the fat mass and obesity-associated (FTO) enzyme was identified as the first m6A demethylase almost 40 years later. The m6A modification influences nearly every step of RNA metabolism and thus broadly affects gene expression at multiple levels, playing a critical role in many biological processes, including cancer progression, metastasis, and immune evasion. The m6A level is dynamically regulated by RNA epigenetic machinery comprising methyltransferases such as methyltransferase-like protein 3 (METTL3), demethylases FTO and AlkB human homologue 5 (ALKBH5), and multiple reader proteins. The understanding of the biology of RNA epigenetics and its translational drug discovery is still in its infancy. It is essential to further develop chemical probes and lead compounds for an in-depth investigation into m6A biology and the translational discovery of anticancer drugs targeting m6A modifying oncogenic proteins.In this Account, we present our work on the development of chemical inhibitors to regulate m6A in mRNA by targeting the FTO demethylase, and the elucidation of their mode of action. We reported rhein to be the first substrate competitive FTO inhibitor. Due to rhein's poor selectivity, we identified meclofenamic acid (MA) that selectively inhibits FTO compared with ALKBH5. Based on the structural complex of MA bound with FTO, we designed MA analogs FB23-2 and Dac51, which exhibit significantly improved activities compared with MA. For example, FB23-2 is specific to FTO inhibition in vitro among over 400 other oncogenic proteins, including kinases, proteases, and DNA and histone epigenetic proteins. Mimicking FTO depletion, FB23-2 promotes the differentiation/apoptosis of human acute myeloid leukemia (AML) cells and inhibits the progression of primary cells in xenotransplanted mice. Dac51 treatment impairs the glycolytic activity of tumor cells and restores the function of CD8+ T cells, thereby inhibiting the growth of solid tumors in vivo. These FTO inhibitors were and will continue to be used as probes to promote biological studies of m6A modification and as lead compounds to target FTO in anticancer drug discovery.Toward the end, we also include a brief review of ALKBH5 demethylase inhibitors and METTL3 methyltransferase modulators. Collectively, these small-molecule modulators that selectively target RNA epigenetic proteins will promote in-depth studies on the regulation of gene expression and potentially accelerate anticancer target discovery.

FTO facilitates cancer metastasis by modifying the m6A level of FAP to induce integrin/FAK signaling in non-small cell lung cancer

BACKGROUND

Emerging evidence suggests the critical roles of N6-methyladenosine (m6A) RNA modification in tumorigenesis and tumor progression. However, the role of m6A in non-small cell lung cancer (NSCLC) is still unclear. This study aimed to explore the role of the m6A demethylase fat mass and obesity-associated protein (FTO) in the tumor metastasis of NSCLC.

METHODS

A human m6A epitranscriptomic microarray analysis was used to identify downstream targets of FTO. Quantitative real-time PCR (qRT‒PCR) and western blotting were employed to evaluate the expression levels of FTO and FAP in NSCLC cell lines and tissues. Gain-of-function and loss-of-function assays were conducted in vivo and in vitro to assess the effects of FTO and FAP on NSCLC metastasis. M6A-RNA immunoprecipitation (MeRIP), RNA immunoprecipitation (RIP), luciferase reporter assays, and RNA stability assays were used to explore the mechanism of FTO action. Co-immunoprecipitation (co-IP) assays were used to determine the mechanism of FAP in NSCLC metastasis.

RESULTS

FTO was upregulated and predicted poor prognosis in patients with NSCLC. FTO promoted cell migration and invasion in NSCLC, and the FAK inhibitor defactinib (VS6063) suppressed NSCLC metastasis induced by overexpression of FTO. Mechanistically, FTO facilitated NSCLC metastasis by modifying the m6A level of FAP in a YTHDF2-dependent manner. Moreover, FTO-mediated metastasis formation depended on the interactions between FAP and integrin family members, which further activated the FAK signaling.

CONCLUSION

Our current findings provided valuable insights into the role of FTO-mediated m6A demethylation modification in NSCLC metastasis. FTO was identified as a contributor to NSCLC metastasis through the activation of the FAP/integrin/FAK signaling, which may be a potential therapeutic target for NSCLC. Video Abstract.

The emerging roles of N6-methyladenosine RNA modifications in thyroid cancer

Thyroid cancer (TC) is the most predominant malignancy of the endocrine system, with steadily growing occurrence and morbidity worldwide. Although diagnostic and therapeutic methods have been rapidly developed in recent years, the underlying molecular mechanisms in the pathogenesis of TC remain enigmatic. The N6-methyladenosine(m6A) RNA modification is designed to impact RNA metabolism and further gene regulation. This process is intricately regulated by a variety of regulators, such as methylases and demethylases. Aberrant m6A regulators expression is related to the occurrence and development of TC and play an important role in drug resistance. This review comprehensively analyzes the effect of m6A methylation on TC progression and the potential clinical value of m6A regulators as prognostic markers and therapeutic targets in this disease.

N6-methyladenosine (m6A) in cancer therapeutic resistance: Potential mechanisms and clinical implications

Cancer therapy resistance (CTR) is the development of cancer resistance to multiple therapeutic strategies, which severely affects clinical response and leads to cancer progression, recurrence, and metastasis. N6-methyladenosine (m6A) has been identified as the most common, abundant, and conserved internal transcriptional alterations of RNA modifications, regulating RNA splicing, translation, stabilization, degradation, and gene expression, and is involved in the development and progression of a variety of diseases, including cancer. Recent studies have shown that m6A modifications play a critical role in both cancer development and progression, especially in reversing CTR. Although m6A modifications have great potential in CTR, the specific molecular mechanisms are not fully elucidated. In this review, we summarize the potential molecular mechanisms of m6A modification in CTR. In addition, we update recent advances in natural products from Traditional Chinese Medicines (TCM) and small-molecule lead compounds targeting m6A modifications, and discuss the great potential and clinical implications of these inhibitors targeting m6A regulators and combinations with other therapies to improve clinical efficacy and overcome CTR.

ALKBH5 modulates hematopoietic stem and progenitor cell energy metabolism through m6A modification-mediated RNA stability control

N6-methyladenosine (m6A) RNA modification controls numerous cellular processes. To what extent these post-transcriptional regulatory mechanisms play a role in hematopoiesis has not been fully elucidated. We here show that the m6A demethylase alkB homolog 5 (ALKBH5) controls mitochondrial ATP production and modulates hematopoietic stem and progenitor cell (HSPC) fitness in an m6A-dependent manner. Loss of ALKBH5 results in increased RNA methylation and instability of oxoglutarate-dehydrogenase (Ogdh) messenger RNA and reduction of OGDH protein levels. Limited OGDH availability slows the tricarboxylic acid (TCA) cycle with accumulation of α-ketoglutarate (α-KG) and conversion of α-KG into L-2-hydroxyglutarate (L-2-HG). L-2-HG inhibits energy production in both murine and human hematopoietic cells in vitro. Impaired mitochondrial energy production confers competitive disadvantage to HSPCs and limits clonogenicity of Mll-AF9-induced leukemia. Our study uncovers a mechanism whereby the RNA m6A demethylase ALKBH5 regulates the stability of metabolic enzyme transcripts, thereby controlling energy metabolism in hematopoiesis and leukemia.

Low m6A modification-mediated upregulation of PLAC8 promotes trophoblast cell invasion and migration in preeclampsia

BACKGROUND

The main symptoms of preeclampsia (PE), a specific ailment that develops during pregnancy, are proteinuria and hypertension. The pathological root of the onset and progression of PE is widely regarded as abnormal placental trophoblast cell function. This study aimed to look into the character and mechanism of Placenta-specific 8 (PLAC8) in trophoblast cell invasion and migration.

METHODS

Expressions of PLAC8 and AlkB homologue 5 (ALKBH5) were examined by western blot and quantitative real-time PCR. The m6A level of PLAC8 mRNA was detected by methylated RNA Immunoprecipitation. Using Transwell experiments, cell invasion and migration were examined. The enzyme-linked immunosorbent assay was utilized to analyze the MMP-2 and MMP-9 secretion levels. RNA pull-down and RNA immunoprecipitation were conducted to detect the binding between ALKBH5 and PLAC8.

RESULTS

In PE tissue and hypoxia-treated HTR-8/SVneo cells, levels of ALKBH5 and PLAC8 were increased, and PLAC8 m6A methylation levels were decreased. There was a positive correlation between PLAC8 and ALKBH5 expression in clinical tissues. In addition, overexpressing PLAC8 promoted HTR-8/SVneo cell migration and invasion, and so as the levels of MMP-2 and MMP-9; while interference with PLAC8 reduced the migration and invasion of hypoxia-treated HTR-8/SVneo cells, and so as the levels of MMP-2 and MMP-9. Moreover, the PLAC8 mRNA's m6A modification site was GAACU (Position 1449, Site 2). Increased levels of MMP-2 and MMP-9, as well as migration and invasion of HTR-8/SVneo cells exposed to hypoxia, were all facilitated by the m6A Site2 mutation. Furthermore, ALKBH5 could bind to PLAC8, reduce its m6A modification, and promote its expression.

CONCLUSION

High-expressed ALKBH5 inhibits the m6A level of PLAC8 mRNA and promotes PLAC8 expression, while PLAC8 overexpression can promote hypoxia-induced invasion and migration of HTR-8/Svneo cells, indicating its potential protective function in PE.

ALKBH5 enhances lipid metabolism reprogramming by increasing stability of FABP5 to promote pancreatic neuroendocrine neoplasms progression in an m6A-IGF2BP2-dependent manner

The process of post-transcriptional regulation has been recognized to be significantly impacted by the presence of N6-methyladenosine (m6A) modification. As an m6A demethylase, ALKBH5 has been shown to contribute to the progression of different cancers by increasing expression of several oncogenes. Hence, a better understanding of the key targets of ALKBH5 in cancer cells could potentially lead to the development of new therapeutic targets. However, the specific role of ALKBH5 in pancreatic neuroendocrine neoplasms (pNENs) remains largely unknown. Here, we demonstrated that ALKBH5 was up-regulated in pNENs and played a critical role in tumor growth and lipid metabolism. Mechanistically, ALKBH5 over-expression was found to increase the expression of FABP5 in an m6A-IGF2BP2 dependent manner, leading to disorders in lipid metabolism. Additionally, ALKBH5 was found to activate PI3K/Akt/mTOR signaling pathway, resulting in enhanced lipid metabolism and proliferation abilities. In conclusion, our study uncovers the ALKBH5/IGF2BP2/FABP5/mTOR axis as a mechanism for aberrant m6A modification in lipid metabolism and highlights a new molecular basis for the development of therapeutic strategies for pNENs treatment.

ALKBH5 controls the meiosis-coupled mRNA clearance in oocytes by removing the N 6-methyladenosine methylation

N6-methyladenosine (m6A) maintains maternal RNA stability in oocytes. One regulator of m6A, ALKBH5, reverses m6A deposition and is essential in RNA metabolism. However, the specific role of ALKBH5 in oocyte maturation remains elusive. Here, we show that Alkbh5 depletion causes a wide range of defects in oocyte meiosis and results in female infertility. Temporal profiling of the maternal transcriptomes revealed striking RNA accumulation in Alkbh5-/- oocytes during meiotic maturation. Analysis of m6A dynamics demonstrated that ALKBH5-mediated m6A demethylation ensures the timely degradation of maternal RNAs, which is severely disrupted following Alkbh5-/- depletion. A distinct subset of transcripts with persistent m6A peaks are recognized by the m6A reader IGF2BP2 and thus remain stabilized, resulting in impaired RNA clearance. Additionally, reducing IGF2BP2 in Alkbh5-depleted oocytes partially rescued these defects. Overall, this work identifies ALKBH5 as a key determinant of oocyte quality and unveil the facilitating role of ALKBH5-mediated m6A removal in maternal RNA decay.

Crosstalk Between m6A RNA Methylation and miRNA Biogenesis in Cancer: An Unholy Nexus

N6-methyladenosine (m6A) is one of the most prevalent internal reversible chemical modification of RNAs in eukaryotes, which has attracted widespread attention recently owing to its regulatory roles in a plethora of normal developmental processes and human diseases like cancer. Deposition of the m6A mark on RNAs is mediated by the dynamic interplay between m6A regulatory proteins such as m6A RNA methyltransferases (m6A writers), m6A RNA demethylases (m6A erasers) and m6A RNA binding proteins (m6A readers). m6A regulators are ectopically expressed in various cancer types, often leading to aberrant expression of tumor-suppressor and oncogenic mRNAs either directly or indirectly via regulating the biogenesis of non-coding RNAs like miRNAs. miRNAs are tiny regulators of gene expression, which often impact various hallmarks of cancer and thus influence tumorigenesis. It is becoming increasingly clear that m6A RNA modification impacts biogenesis and function of miRNAs, and recent studies have interestingly, uncovered many miRNAs whose biogenesis and function are regulated by m6A writers, erasers and readers. In this review, we discuss various mechanisms by which m6A RNA methylation regulates miRNA biogenesis, the functional crosstalk between m6A RNA methylation and miRNAs and how it modulates various aspects of tumorigenesis. The potential of m6A RNA methylation regulated miRNAs as biomarkers and novel therapeutic targets to treat various cancers is also addressed.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

The role of N6-methyladenosine (m6A) in kidney diseases

Chemical modifications are a specific and efficient way to regulate the function of biological macromolecules. Among them, RNA molecules exhibit a variety of modifications that play important regulatory roles in various biological processes. More than 170 modifications have been identified in RNA molecules, among which the most common internal modifications include N6-methyladenine (m6A), n1-methyladenosine (m1A), 5-methylcytosine (m5C), and 7-methylguanine nucleotide (m7G). The most widely affected RNA modification is m6A, whose writers, readers, and erasers all have regulatory effects on RNA localization, splicing, translation, and degradation. These functions, in turn, affect RNA functionality and disease development. RNA modifications, especially m6A, play a unique role in renal cell carcinoma disease. In this manuscript, we will focus on the biological roles of m6A in renal diseases such as acute kidney injury, chronic kidney disease, lupus nephritis, diabetic kidney disease, and renal cancer.

METTL14‑mediated RNA methylation in digestive system tumors

N6‑methyladenosine (m6A) RNA methylation is one of the most common post‑transcriptional modification mechanism in eukaryotes. m6A is involved in almost all stages of the mRNA life cycle, specifically regulating its stability, splicing, export and translation. Methyltransferase‑like 14 (METTL14) is a particularly important m6A methylation 'writer' that can recognize RNA substrates. METTL14 has been documented to improve the activity and catalytic efficiency of METTL3. However, as individual proteins they can also regulate different biological processes. Malignancies in the digestive system are some of the most common malignancies found in humans, which are typically associated with poor prognoses with limited clinical solutions. METTL14‑mediated methylation has been implicated in both the potentiation and inhibition of digestive system tumor growth, cell invasion and metastasis, in addition to drug resistance. In the present review, the research progress and regulatory mechanisms of METTL14‑mediated methylation in digestive system malignancies were summarized. In addition, future research directions and the potential for its clinical application were examined.

RNA methylations in depression, from pathological mechanism to therapeutic potential

Depression is caused by a variety of factors such as genetic factors, biological factors, and psychosocial factors, and the pathogenesis is complex. RNA methylations and related downstream signaling pathways influence a variety of biological mechanisms, including cell differentiation, tumorigenesis, sex determination, and stress response. In this work, we searched the PubMed, Web of Science, National Library of Science and Technology (NSTL), and ScienceDirect Online (SDOL) databases to summarize the biological roles of RNA methylations and their impact on the pathological mechanisms of depression. RNA methylations play a key role in the development of many diseases, and current research shows that RNA methylations are also closely linked to depression. RNA methylations in depression mainly involve "writers" (mediating the methylation modification process of RNAs), "erasers" (mediating the demethylation modification process of RNA methylation). Fat Mass and Obesity Associated (FTO) influences the development of depression by increasing body mass index (BMI), decreases the dopamine level, inhibits the adrenoceptor beta 2 (ADRB2)-c-Myc-sirt1 pathway, results in the m6A/m6Am dysregulation in brain, and may be involved in the pathogenesis of depression. The study of RNA methylations in depression has further deepened our understanding of the pathogenesis and development process of depression, provides new perspectives for the study of the pathological mechanism of depression, and provides new targets for the prevention and treatment of this disease.

Chinese Ecliptae herba (Eclipta prostrata (L.) L.) extract and its component wedelolactone enhances osteoblastogenesis of bone marrow mesenchymal stem cells via targeting METTL3-mediated m6A RNA methylation

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese Ecliptae herba (Eclipta prostrata (L.) L.) is an ethnomedicinal herb, which is used mainly to nourish kidney and thus strengthen bones according to traditional Chinese medicine theory. Pharmacological studies have supported the ethnomedicine use, showing that Ecliptae herba extract has an anti-osteoporotic effect in vivo and promoted osteoblast proliferation and activity in vitro. However, the molecular mechanism of Ecliptae herba on osteoblast differentiation from bone marrow mesenchymal stem cells (BMSC), the progenitors of osteoblasts, is still unclear.

AIM OF THE STUDY

N6-methyladenosine (m6A) mRNA epigenetic modification may play a key role in promoting osteoblastic differentiation, and thus treating osteoporosis. This study sought to assess the mechanism through which Eclipate herba and its component wedelolactone influence m6A modification during the process of osteoblastogenesis from BMSC.

MATERIAL AND METHODS

The alkaline phosphatase (ALP) and Alizarin red S (ARS) staining were applied to determine osteoblastogenesis from BMSC. Western blot and quantitative real-time PCR were performed. RNA sequencing analysis was used to determine the characteristics of m6A methylation. Stable knocking down of METTL3 using lentiviral-based shRNA was performed.

RESULTS

Upon 9 d treatment of BMSC with ethyl acetate extract of Ecliptae herba (MHL), ALP activity and ossification level increased in comparison with osteogenic medium (OS)-treated control. The expression of methyltransferase METTL3 and METTL14 was significantly increased, but WTAP expression had no change in response to MHL treatment. Knocking down of METTL3 resulted in a decrease in MHL-induced ALP activity, ossification level as well as mRNA expression of Osterix and Osteocalcin, two bone formation-related markers. The level of m6A increased when BMSC was treated with MHL for 9 d. RNA sequencing analysis indicated that MHL treatment altered mRNA m6A modification of genes associated with osteoblastogenesis. By kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, HIF-1α, PI3K/Akt, and Hippo signaling pathways were enriched and associated with m6A modification. The expression of m6A-modified genes including HIF-1α, VEGF-A, and RASSF1, was upregulated by MHL, but the upregulation was reversed after METTL3 knockdown. Additionally, the enhanced expression of METTL3 was also observed after treatment with wedelolactone, a component from MHL.

CONCLUSIONS

These results suggested a previously uncharacterized mechanism of MHL and wedelolactone on osteoblastogenesis, by which METTL3-mediated m6A methylation is involved and thus contributes to the enhancement of osteoblastogenesis.

Characterization of m6A modifiers and RNA modifications in uterine fibroids

Uterine leiomyoma or fibroids are the most common prevalent noncancerous tumors of the uterine muscle layer. Common symptoms associated with fibroids include pelvic pain, heavy menstrual bleeding, anemia, and pelvic pressure. These tumors are a leading cause of gynecological care but lack long-term therapy as the origin and development of fibroids are not well understood. Several next-generation sequencing technologies have been performed to identify the underlying genetic and epigenetic basis of fibroids. However, there remains a systemic gap in our understanding of molecular and biological process that define uterine fibroids. Recent epitranscriptomics studies have unraveled RNA modifications that are associated with all forms of RNA and are thought to influence both normal physiological functions and the progression of diseases. We quantified RNA expression profiles by analyzing publicly available RNA-seq data for 15 known epigenetic mediators to identify their expression profile in uterine fibroids compared to myometrium. To validate our findings, we performed RT-qPCR on a separate cohort of uterine fibroids targeting these modifiers confirming our RNA-seq data. We then examined protein profiles of key m6A modifiers in fibroids and their matched myometrium. In concordance with our RNA expression profiles, no significant differences were observed in these proteins in uterine fibroids compared to myometrium. To determine abundance of RNA modifications, mRNA and small RNA from fibroids and matched myometrium were analyzed by UHPLC MS/MS. In addition to the prevalent N6-methyladenosine (m6A), we identified 11 other known modifiers but did not identify any aberrant expression in fibroids. We then mined a previously published dataset and identified differential expression of m6A modifiers that were specific to fibroid genetic sub-type. Our analysis also identified m6A consensus motifs on genes previously identified to be dysregulated in uterine fibroids. Overall, using state-of-the-art mass spectrometry, RNA expression and protein profiles, we characterized and identified differentially expressed m6A modifiers in relation to driver mutations. Despite the use of several different approaches, we identified limited differential expression of RNA modifiers and associated modifications in uterine fibroids. However, considering the highly heterogenous genomic and cellular nature of fibroids, and the possible contribution of single molecule m6A modifications to fibroid pathology, there is a need for greater in-depth characterization of m6A marks and modifiers in a larger and varied patient cohort.

ALKB homolog 5 (ALKBH5)-induced circPUM1 upregulation facilitated the progression of neuroblastoma via miR-423-5p/PA2G4 axis

BACKGROUND

The oncogenic role of circPUM1 has been revealed in multiple cancers. Nevertheless, the specific role and molecular mechanism of circPUM1 in neuroblastoma (NB) have never been reported.

METHODS

The expression of genes was detected using RT-qPCR and Western Blot assay. The proliferation, migration, and invasion of NB cells were evaluated by CCK-8 and Transwell assays. Besides, mouse model was established to evaluate the effect of circPUM1 on the progression of NB. The interaction among genes was verified through RIP, MeRIP, or Luciferase reporter assay.

RESULTS

Through our investigation, it was discovered that circPUM1 expression was abnormally elevated in NB tissues and the abundance of circPUM1 was correlated with unfavorable clinical outcomes in NB patients. Besides, the viability and mobility of NB cells as well as NB tumor growth were suppressed by silencing circPUM1. Moreover, bioinformatics prediction and experimental verification demonstrated that circPUM1 was a sponge for miR-423-5p which further targeted proliferation-associated protein 2G4 (PA2G4). The oncogenic effect of circPUM1 on NB was exerted through suppressing miR-423-5p to elevate PA2G4 expression. Finally, we investigated the transcriptional factor causing the upregulation of circPUM1 in NB. The result was that ALKB homolog 5 (ALKBH5), an m6A demethylase, suppressed the m6A modification of circPUM1 and caused the elevation of circPUM1 expression in NB.

CONCLUSION

ALKBH5 induced the upregulation of circPUM1 to accelerate the development of NB through regulating miR-423-5p/PA2G4 axis.

ALKBH5 causes retinal pigment epithelium anomalies and choroidal neovascularization in age-related macular degeneration via the AKT/mTOR pathway

Retinal pigment epithelium (RPE) dysfunction and choroidal neovascularization (CNV) are predominant features of age-related macular degeneration (AMD), with an unclear mechanism. Herein, we show that RNA demethylase α-ketoglutarate-dependent dioxygenase alkB homolog 5 (ALKBH5) is up-regulated in AMD. In RPE cells, ALKBH5 overexpression associates with depolarization, oxidative stress, disturbed autophagy, irregular lipid homeostasis, and elevated VEGF-A secretion, which subsequently promotes proliferation, migration, and tube formation of vascular endothelial cells. Consistently, ALKBH5 overexpression in mice RPE correlates with various pathological phenotypes, including visual impairments, RPE anomalies, choroidal neovascularization (CNV), and interrupted retinal homeostasis. Mechanistically, ALKBH5 regulates retinal features through its demethylation activity. It targets PIK3C2B and regulates the AKT/mTOR signaling pathway with YTHDF2 as the N⁶-methyladenosine reader. IOX1, an ALKBH5 inhibitor, suppresses hypoxia-induced RPE dysfunction and CNV progression. Collectively, we demonstrate that ALKBH5 induces RPE dysfunction and CNV progression in AMD via PIK3C2B-mediated activation of the AKT/mTOR pathway. Pharmacological inhibitors of ALKBH5, like IOX1, are promising therapeutic options for AMD.

Effects of DNA, RNA, and Protein Methylation on the Regulation of Ferroptosis

Ferroptosis is a form of programmed cell death characterized by elevated intracellular ferrous ion levels and increased lipid peroxidation. Since its discovery and characterization in 2012, considerable progress has been made in understanding the regulatory mechanisms and pathophysiological functions of ferroptosis. Recent findings suggest that numerous organ injuries (e.g., ischemia/reperfusion injury) and degenerative pathologies (e.g., aortic dissection and neurodegenerative disease) are driven by ferroptosis. Conversely, insufficient ferroptosis has been linked to tumorigenesis. Furthermore, a recent study revealed the effect of ferroptosis on hematopoietic stem cells under physiological conditions. The regulatory mechanisms of ferroptosis identified to date include mainly iron metabolism, such as iron transport and ferritinophagy, and redox systems, such as glutathione peroxidase 4 (GPX4)-glutathione (GSH), ferroptosis-suppressor-protein 1 (FSP1)-CoQ10, FSP1-vitamin K (VK), dihydroorotate dehydrogenase (DHODH)-CoQ, and GTP cyclohydrolase 1 (GCH1)-tetrahydrobiopterin (BH4). Recently, an increasing number of studies have demonstrated the important regulatory role played by epigenetic mechanisms, especially DNA, RNA, and protein methylation, in ferroptosis. In this review, we provide a critical analysis of the molecular mechanisms and regulatory networks of ferroptosis identified to date, with a focus on the regulatory role of DNA, RNA, and protein methylation. Furthermore, we discuss some debated findings and unanswered questions that should be the foci of future research in this field.

N6-methyladenosine RNA modification: an emerging molecule in type 2 diabetes metabolism

Type 2 diabetes (T2D) is a metabolic disease with an increasing rate of incidence worldwide. Despite the considerable progress in the prevention and intervention, T2D and its complications cannot be reversed easily after diagnosis, thereby necessitating an in-depth investigation of the pathophysiology. In recent years, the role of epigenetics has been increasingly demonstrated in the disease, of which N6-methyladenosine (m6A) is one of the most common post-transcriptional modifications. Interestingly, patients with T2D show a low m6A abundance. Thus, a comprehensive analysis and understanding of this phenomenon would improve our understanding of the pathophysiology, as well as the search for new biomarkers and therapeutic approaches for T2D. In this review, we systematically introduced the metabolic roles of m6A modification in organs, the metabolic signaling pathways involved, and the effects of clinical drugs on T2D.

Small RNA modifications: regulatory molecules and potential applications

Small RNAs (also referred to as small noncoding RNAs, sncRNA) are defined as polymeric ribonucleic acid molecules that are less than 200 nucleotides in length and serve a variety of essential functions within cells. Small RNA species include microRNA (miRNA), PIWI-interacting RNA (piRNA), small interfering RNA (siRNA), tRNA-derived small RNA (tsRNA), etc. Current evidence suggest that small RNAs can also have diverse modifications to their nucleotide composition that affect their stability as well as their capacity for nuclear export, and these modifications are relevant to their capacity to drive molecular signaling processes relevant to biogenesis, cell proliferation and differentiation. In this review, we highlight the molecular characteristics and cellular functions of small RNA and their modifications, as well as current techniques for their reliable detection. We also discuss how small RNA modifications may be relevant to the clinical applications for the diagnosis and treatment of human health conditions such as cancer.

Targeting m6A binding protein YTHDFs for cancer therapy

N⁶-methyladenosine (m⁶A) is the most common mRNA modification in mammalians. The function and dynamic regulation of m⁶A depends on the "writer", "readers" and "erasers". YT521-B homology domain family (YTHDF) is a class of m⁶A binding proteins, including YTHDF1, YTHDF2 and YTHDF3. In recent years, the modification of m⁶A and the molecular mechanism of YTHDFs have been further understood. Growing evidence has shown that YTHDFs participate in multifarious bioprocesses, particularly tumorigenesis. In this review, we summarized the structural characteristics of YTHDFs, the regulation of mRNA by YTHDFs, the role of YTHDF proteins in human cancers and inhibition of YTHDFs.

Bone Lesion-Derived Extracellular Vesicles Fuel Prometastatic Cascades in Hepatocellular Carcinoma by Transferring ALKBH5-Targeting miR-3190-5p

Bone is the second leading metastatic site for hepatocellular carcinoma (HCC). Patients with HCC and bone metastasis suffer poor quality of life and reduced survival time. Extracellular vesicles (EVs) are widely involved in HCC formation and metastasis. However, the communication between primary HCC and bone lesions mediated by EVs remains unclear and the possible effect of bone metastasis on the progression of HCC remains largely unknown. Here, bone-metastasized HCC-derived EVs (BM-EVs) are found to localize to orthotropic HCC cells and promote HCC progression. Mechanistically, miR-3190-5p (miR-3190) is upregulated in intracellular HCC cells isolated from bone lesions as well as in their derived EVs. miR-3190 in BM-EVs is transferred into orthotopic tumor cells and enhances their metastatic capacity by downregulating AlkB homolog 5 (ALKBH5) expression. Decreased level of ALKBH5 exacerbates the prometastatic characteristics of HCC by modulating gene expression in N6-methyladenosine-dependent and -independent ways. Finally, antagomir-miR-3190-loaded liposomes with HCC affinity successfully suppress HCC progression in mice treated with BM-EVs. These findings reveal that BM-EVs initiate prometastatic cascades in orthotopic HCC by transferring ALKBH5-targeting miR-3190 and miR-3190 is serving as a promising therapeutic target for inhibiting the progression of HCC in patients with bone metastasis.

Role of m6A modification in immune microenvironment of digestive system tumors

Digestive system tumors are huge health problem worldwide, largely attributable to poor dietary choices. The role of RNA modifications in cancer development is an emerging field of research. RNA modifications are associated with the growth and development of various immune cells, which, in turn, regulate the immune response. The majority of RNA modifications are methylation modifications, and the most common type is the N6-methyladenosine (m6A) modification. Here, we reviewed the molecular mechanism of m6A in the immune cells and the role of m6A in the digestive system tumors. However, further studies are required to better understand the role of RNA methylation in human cancers for designing diagnostic and treatment strategies and predicting the prognosis of patients.

ALKBH5-PYCR2 Positive Feedback Loop Promotes Proneural-Mesenchymal Transition Via Proline Synthesis In GBM

AlkB homolog 5, RNA demethylase (ALKBH5) is abnormally highly expressed in glioblastoma multiforme (GBM) and is negatively correlated with overall survival in GBM patients. In this study, we found a new mechanism that ALKBH5 and pyrroline-5-carboxylate reductase 2 (PYCR2) formed a positive feedback loop involved in proline synthesis in GBM. ALKBH5 promoted PYCR2 expression and PYCR2-mediated proline synthesis; while PYCR2 promoted ALKBH5 expression through the AMPK/mTOR pathway in GBM cells. In addition, ALKBH5 and PYCR2 promoted GBM cell proliferation, migration, and invasion, as well as proneural-mesenchymal transition (PMT). Furthermore, proline rescued AMPK/mTOR activation and PMT after silencing PYCR2 expression. Our findings reveal an ALKBH5-PYCR2 axis linked to proline metabolism, which plays an important role in promoting PMT in GBM cells and may be a promising therapeutic pathway for GBM.

Smoking-Induced M2-TAMs, via circEML4 in EVs, Promote the Progression of NSCLC through ALKBH5-Regulated m6A Modification of SOCS2 in NSCLC Cells

Lung cancer is a commonly diagnosed disease worldwide, with non-small cell lung cancers (NSCLCs) accounting for ≈ 85% of cases. Cigarette smoke is an environmental exposure promoting progression of NSCLC, but its role is poorly understood. This study reports that smoking-induced accumulation of M2-type tumor-associated macrophages (M2-TAMs) surrounding NSCLC tissues promotes malignancy. Specifically, extracellular vesicles (EVs) from cigarette smoke extract (CSE)-induced M2 macrophages promoted malignancy of NSCLC cells in vitro and in vivo. circEML4 in EVs from CSE-induced M2 macrophages is transported to NSCLC cells, where it reduced the distribution of ALKBH5 in the nucleus by interacting with Human AlkB homolog H5 (ALKBH5), resulting in elevated N6-methyladenosine (m6A) modifications. m6A-seq and RNA-seq revealed suppressor of cytokine signaling 2 (SOCS2)-mediated activation of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway by regulating m6A modification of SOCS2 via ALKBH5. Down-regulation of circEML4 in EVs from CSE-induced M2 macrophages reversed EVs-enhanced tumorigenicity and metastasis in NSCLC cells. Furthermore, this study found that smoking patients showed an increase in circEML4-positive M2-TAMs. These results indicate that smoking-induced M2-TAMs via circEML4 in EVs promote the NSCLC progression through ALKBH5-regulated m6A modification of SOCS2. This study also reveals that circEML4 in EVs from TAMs acts as a diagnostic biomarker for NSCLC, especially for patients with smoking history.

RNA demethylase ALKBH5 suppresses tumorigenesis via inhibiting proliferation and invasion and promoting CD8+ T cell infiltration in colorectal cancer

BACKGROUND

ALKBH5 belongs to the ALKB family consists of a Fe (II) and a-ketoglutarate-dependent dioxygenase. ALKBH5 directly catalyzes the oxidative demethylation of m6A-methylated adenosine. ALKBH5 involves in tumorigenesis and tumor progression, and is often dysregulated in a wide range of cancers, including colorectal cancer. Emerging evidence indicates that the expression of ALKBH5 is associated with the abundance of infiltrating immune cells in the microenvironment. However, how ALKBH5 affects immune cell infiltration in the microenvironment in colorectal cancer (CRC) has not been reported. The aim of this study was to identify how the expression of ALKBH5 affects the biological behaviors of CRC cell lines and regulates the effects on infiltrating CD8⁺ T cells in CRC microenvironment with its specific mechanism.

METHODS

Firstly, the transcriptional expression profiles of CRC were downloaded from TCGA database and integrated via R software (4.1.2). Between CRC and normal colorectal tissues, ALKBH5 mRNA expressions were compared (Wilcoxon rank-sum). We further identified the expression levels of ALKBH5 in CRC tissues and cell lines through quantitative PCR, western blot, and immunohistochemistry. Then, how ALKBH5 affects the biological behaviors of CRC cells were confirmed by gain- and loss-of-function analysis. Furthermore, the relationship between ALKBH5 level and 22 tumor-infiltrating immune cells was examined through CIBERSORT in R software. Furthermore, we explored the correlation between ALKBH5 expression and tumor-infiltrated CD8⁺, CD4⁺ and regulatory T cells by utilizing the TIMER database. Finally, the association between chemokines and CD8⁺ T cells infiltration in CRC was analyzed using GEPIA online database. qRT-PCR, WB and IHC were used to further determine the effect of ALKBH5 on NF-κB-CCL5 signaling axis and CD8⁺ T cells infiltration.

RESULTS

Clinically, ALKBH5 expression was downregulated in CRC and low levels of ALKBH5 expression were correlated with poor overall survival (OS). Functionally, overexpression of ALKBH5 reduced the proliferation, migration and invasion of CRC cells, and vice versa. Overexpression of ALKBH5 suppresses NF-κB pathway, thus reduces CCL5 expression and promotes CD8⁺ T cells infiltration in CRC microenvironment.

CONCLUSIONS

ALKBH5 is poorly expressed in CRC, and overexpression of ALKBH5 attenuates CRC malignant progression by inhibiting CRC cell proliferation, migration, invasion and promoting CD8⁺ T cells infiltration in the tumor microenvironment through NF-κB-CCL5 axis.