IDH2 contributes to tumorigenesis and poor prognosis by regulating m6A RNA methylation in multiple myeloma

Systematical identification of key genes and regulatory genetic variants associated with prognosis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) stands as a highly lethal malignancy characterized by pronounced recurrence and metastasis, resulting in a bleak 5-year survival rate. Despite extensive investigations, encompassing genome-wide association studies, the identification of robust prognostic markers has remained elusive. In this study, leveraging four independent data sets comprising 404 ESCC patients, we conducted a systematic analysis to unveil pivotal genes influencing overall survival. our meta-analysis identified 278 genes significantly associated with ESCC prognosis. Further exploration of the prognostic landscape involved an examination of expression quantitative trait loci for these genes, leading to the identification of six tag single nucleotide polymorphisms predictive of overall survival in a cohort of 904 ESCC patients. Notably, functional annotation spotlighted rs11227223, residing in the enhancer region of nuclear paraspeckle assembly transcript 1 (NEAT1), as a crucial variant likely exerting a substantive biological role. Through a series of biochemistry experiments, we conclusively demonstrated that the rs11227223-T allele, indicative of a poorer prognosis, augmented NEAT1 expression. Our results underscore the substantive role of NEAT1 and its regulatory variant in prognostic predictions for ESCC. This comprehensive analysis not only advances our comprehension of ESCC prognosis but also unveils a potential avenue for targeted interventions, offering promise for enhanced clinical outcomes.

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.

N6-methyladenosine-modified circ_0000337 sustains bortezomib resistance in multiple myeloma by regulating DNA repair

Studies have shown that bortezomib resistance in multiple myeloma (MM) is mediated by the abnormalities of various molecules and microenvironments. Exploring these resistance mechanisms will improve the therapeutic efficacy of bortezomib. In this study, bone marrow tissues from three patients with MM, both sensitive and resistant to bortezomib, were collected for circRNA high-throughput sequencing analysis. The relationship between circ_0000337, miR-98-5p, and target gene DNA2 was analyzed by luciferase detection and verified by RT-qPCR. We first found that circ_0000337 was significantly upregulated in bortezomib-resistant MM tissues and cells, and overexpression of circ_0000337 could promote bortezomib resistance in MM cells. circ_0000337 may act as a miR-98-5p sponge to upregulate DNA2 expression, regulate DNA damage repair, and induce bortezomib resistance. Furthermore, it was determined that the increased circ_0000337 level in bortezomib-resistant cells was due to an increased N6-methyladenosine (m6A) level, resulting in enhanced RNA stability. In conclusion, the m6A level of circ_0000337 and its regulation may be a new and potential therapeutic target for overcoming bortezomib resistance in MM.

ALKHB5-demethylated lncRNA SNHG15 promotes myeloma tumorigenicity by increasing chromatin accessibility and recruiting H3K36me3 modifier SETD2

Chromatin instability plays a crucial role in multiple myeloma (MM) relapse and progression, but its mechanism remains obscure. Here, we uncovered that m6A-demethylase ALKBH5 upregulated and stabilized long noncoding RNA (lncRNA) small nucleolar RNA host gene 15 (SNHG15), which was elevated in MM and positively correlated with unfavorable clinical prognosis factors. ALKBH5-SNHG15 axis participated in viability and migration/invasion of myeloma cell lines and MM-xenografted SCID/NOD mice. Mechanically, ALKBH5 promoted the expression of trimethylated histone H3 at lysine 36 (H3K36me3) methyltransferase SETD2 through lncRNA SNHG15-mediated protein stability. ALKBH5-SNHG15 axis increased chromatin accessibility and altered the H3K36me3 enrichment at the gene body, which is responsible for transcription elongation. Our study suggested a novel epigenetically interaction of N6-methyladenosine (m6A) methylation, lncRNA SNHG15, and histone SETD2/H3K36me3 modifications in myeloma progression, indicating that ALKBH5 and lncRNA SNHG15 could serve as potential novel therapeutic targets for MM treatment.NEW & NOTEWORTHY To our knowledge, this study first demonstrated the prognostic significance and biological function of long noncoding RNA (lncRNA) small nucleolar RNA host gene 15 (SNHG15) in multiple myeloma (MM), and indicated a novel revelation on the effect of N6-methyladenosine (m6A)-regulated lncRNA on MM tumorigenicity. Moreover, the novel chromatin-regulatory mechanism of lncRNA by interacting with epigenetic modifiers including m6A demethylase ALKBH5 and H3K36me3 methyltransferase SETD2 in myeloma progression elucidated intricate mechanism of tumor pathogenesis.

LINC00571 drives tricarboxylic acid cycle metabolism in triple-negative breast cancer through HNRNPK/ILF2/IDH2 axis

BACKGROUND

Triple-negative breast cancer is a complex breast malignancy subtype characterized by poor prognosis. The pursuit of effective therapeutic approaches for this subtype is considerably challenging. Notably, recent research has illuminated the key role of the tricarboxylic acid cycle in cancer metabolism and the complex landscape of tumor development. Concurrently, an emerging body of evidence underscores the noteworthy role that long non-coding RNAs play in the trajectory of breast cancer development. Despite this growing recognition, the exploration of whether long non-coding RNAs can influence breast cancer progression by modulating the tricarboxylic acid cycle has been limited. Moreover, the underlying mechanisms orchestrating these interactions have not been identified.

METHODS

The expression levels of LINC00571 and IDH2 were determined through the analysis of the public TCGA dataset, transcriptome sequencing, qRT‒PCR, and Western blotting. The distribution of LINC00571 was assessed using RNA fluorescence in situ hybridization. Alterations in biological effects were evaluated using CCK-8, colony formation, EdU, cell cycle, and apoptosis assays and a tumor xenograft model. To elucidate the interaction between LINC00571, HNRNPK, and ILF2, RNA pull-down, mass spectrometry, coimmunoprecipitation, and RNA immunoprecipitation assays were performed. The impacts of LINC00571 and IDH2 on tricarboxylic acid cycle metabolites were investigated through measurements of the oxygen consumption rate and metabolite levels.

RESULTS

This study revealed the complex interactions between a novel long non-coding RNA (LINC00571) and tricarboxylic acid cycle metabolism. We validated the tumor-promoting role of LINC00571. Mechanistically, LINC00571 facilitated the interaction between HNRNPK and ILF2, leading to reduced ubiquitination and degradation of ILF2, thereby stabilizing its expression. Furthermore, ILF2 acted as a transcription factor to enhance the expression of its downstream target gene IDH2.

CONCLUSIONS

Our study revealed that the LINC00571/HNRNPK/ILF2/IDH2 axis promoted the progression of triple-negative breast cancer by regulating tricarboxylic acid cycle metabolites. This discovery provides a novel theoretical foundation and new potential targets for the clinical treatment of triple-negative breast cancer.

N6-methyladenosine methylation in ophthalmic diseases: From mechanisms to potential applications

N6-methyladenosine (m6A) modification, as the most common modification method in eukaryotes, is widely involved in numerous physiological and pathological processes, such as embryonic development, malignancy, immune regulation, and premature aging. Under pathological conditions of ocular diseases, changes in m6A modification and its metabolism can be detected in aqueous and vitreous humor. At the same time, an increasing number of studies showed that m6A modification is involved in the normal development of eye structures and the occurrence and progress of many ophthalmic diseases, especially ocular neovascular diseases, such as diabetic retinopathy, age-related macular degeneration, and melanoma. In this review, we summarized the latest progress regarding m6A modification in ophthalmic diseases, changes in m6A modification-related enzymes in various pathological states and their upstream and downstream regulatory networks, provided new prospects for m6A modification in ophthalmic diseases and new ideas for clinical diagnosis and treatment.

N6-methyladenosine-induced miR-182-5p promotes multiple myeloma tumorigenesis by regulating CAMK2N1

Methyltransferase like 3 (METTL3) has been reported to promote tumorigenesis of multiple myeloma (MM), however, the molecular mechanism still needs further research. The N6-methyladenosine (m6A) level in tissues or cells was measured by m6A kit and dot blot assay. The mRNA and protein expression were detected by quantitative real-time PCR (RT-qPCR) and Western blot, respectively. The cell counting kit-8 and colony formation assay were used to detect the cell proliferation. Coimmunoprecipitation (Co-IP) experiment verified the binding of two proteins. The luciferase reporter experiment demonstrated the targeted binding of miR-182-5p and CaMKII inhibitor 1 (CAMK2N1). More importantly, tumor growth was measured in xenograft mice. Our data showed that the expression of METTL3 was significantly increased in MM patients' samples and MM cells. METTL3 overexpression promoted MM cells proliferation, and METTL3 knockdown inhibited MM cells proliferation. Mechanically, METTL3-dependent m6A participated in DiGeorge syndrome critical region 8 (DGCR8)-mediated maturation of pri-miR-182. Upregulation of miR-182-5p further enhanced the promoting proliferation effect of METTL3 overexpression on MM cells. Moreover, the luciferase reporter gene experiment proved that miR-182-5p targetedly regulated CAMK2N1 expression. Xenograft tumor in nude mice further verified that METTL3 promoted MM tumor growth through miR-182/CAMK2N1 signal axis. In summary, the METTL3/miR-182-5p/CAMK2N1 axis plays an important role in MM tumorigenesis, which may provide a new target for MM therapy.

Carbon metabolism in the regulation of macrophage functions

Carbon metabolism, including one-carbon (1C) metabolism and central carbon metabolism (CCM), provides energy for the cell and generates metabolites with signaling activities. The regulation of macrophage polarization involves complex signals and includes an epigenetic level. Epigenetic modifications through changes in carbon metabolism allow macrophages to respond in a timely manner to their environment and adapt to metabolic demands during macrophage polarization. Here we summarize the current understanding of the crosstalk between carbon metabolism and epigenetic modifications in macrophages under physiological conditions and in the tumor microenvironment (TME) and provide targets and further directions for macrophage-associated diseases.

CSTF2 mediated mRNA N6-methyladenosine modification drives pancreatic ductal adenocarcinoma m6A subtypes

N6-methyladenosine (m6A) modification of gene transcripts plays critical roles in cancer. Here we report transcriptomic m6A profiling in 98 tissue samples from 65 individuals with pancreatic ductal adenocarcinoma (PDAC). We identify 17,996 m6A peaks with 195 hyper-methylated and 93 hypo-methylated in PDAC compared with adjacent normal tissues. The differential m6A modifications distinguish two PDAC subtypes with different prognosis outcomes. The formation of the two subtypes is driven by a newly identified m6A regulator CSTF2 that co-transcriptionally regulates m6A installation through slowing the RNA Pol II elongation rate during gene transcription. We find that most of the CSTF2-regulated m6As have positive effects on the RNA level of host genes, and CSTF2-regulated m6As are mainly recognized by IGF2BP2, an m6A reader that stabilizes mRNAs. These results provide a promising PDAC subtyping strategy and potential therapeutic targets for precision medicine of PDAC.

Transcription of WNT Genes in Hematopoietic Niche's Mesenchymal Stem Cells in Multiple Myeloma Patients with Different Responses to Treatment

Mesenchymal stromal cells (MSCs) are involved in bone tissue remodeling due to their ability to differentiate into osteoblasts and to influence osteoclasts' activity. Multiple myeloma (MM) is associated with bone resorption. During disease progression, MSCs acquire a tumor-associated phenotype, losing their osteogenic potential. The process is associated with impaired osteoblasts/osteoclasts balance. The WNT signaling pathway plays a major role in maintaining the balance. In MM, it functions in an aberrant way. It is not known yet whether the WNT pathway is restored in patients' bone narrow after treatment. The aim of the study was to compare the level of WNT family gene transcription in the bone marrow MSCs of healthy donors and MM patients before and after therapy. The study included healthy donors (n = 3), primary patients (n = 3) and patients with different response status to therapy (bortezomib-containing induction regimens) (n = 12). The transcription of the WNT and CTNNB1 (encoding β-catenin) genes was accessed using qPCR. The mRNA quantity of ten WNT genes, as well as CTNNB1 mRNA encoding β-catenin, a key mediator in canonical signaling, was evaluated. The observed differences between the groups of patients indicated that aberrant functioning of the WNT pathway was retained after treatment. The differences that we detected for WNT2B, WNT9B and CTNNB1 suggested their possible application as prognostic molecular markers.

Epigenetic regulation in hematopoiesis and its implications in the targeted therapy of hematologic malignancies

Hematologic malignancies are one of the most common cancers, and the incidence has been rising in recent decades. The clinical and molecular features of hematologic malignancies are highly heterogenous, and some hematologic malignancies are incurable, challenging the treatment, and prognosis of the patients. However, hematopoiesis and oncogenesis of hematologic malignancies are profoundly affected by epigenetic regulation. Studies have found that methylation-related mutations, abnormal methylation profiles of DNA, and abnormal histone deacetylase expression are recurrent in leukemia and lymphoma. Furthermore, the hypomethylating agents and histone deacetylase inhibitors are effective to treat acute myeloid leukemia and T-cell lymphomas, indicating that epigenetic regulation is indispensable to hematologic oncogenesis. Epigenetic regulation mainly includes DNA modifications, histone modifications, and noncoding RNA-mediated targeting, and regulates various DNA-based processes. This review presents the role of writers, readers, and erasers of DNA methylation and histone methylation, and acetylation in hematologic malignancies. In addition, this review provides the influence of microRNAs and long noncoding RNAs on hematologic malignancies. Furthermore, the implication of epigenetic regulation in targeted treatment is discussed. This review comprehensively presents the change and function of each epigenetic regulator in normal and oncogenic hematopoiesis and provides innovative epigenetic-targeted treatment in clinical practice.

Non-coding RNAs and exosomal ncRNAs in multiple myeloma: An emphasis on molecular pathways

One of the most common hematological malignancies is multiple myeloma (MM) that its mortality and morbidity have increased. The incidence rate of MM is suggested to be higher in Europe and various kinds of therapeutic strategies including stem cell transplantation. However, MM treatment is still challenging and gene therapy has been shown to be promising. The non-coding RNAs (ncRNAs) including miRNAs, lncRNAs and circRNAs are considered as key players in initiation, development and progression of MM. In the present review, the role of ncRNAs in MM progression and drug resistance is highlighted to provide new insights for future experiments for their targeting and treatment of MM. The miRNAs affect proliferation and invasion of MM cells, and targeting tumor-promoting miRNAs can induce apoptosis and cell cycle arrest, and reduces proliferation of MM cells. Furthermore, miRNA regulation is of importance for modulating metastasis and chemotherapy response of tumor cells. The lncRNAs exert the same function and determine proliferation, migration and therapy response of MM cells. Notably, lncRNAs mainly target miRNAs in regulating MM progression. The circRNAs also target different molecular pathways in regulating MM malignancy that miRNAs are the most well-known ones. Furthermore, clinical application of ncRNAs in MM is discussed.

Role of m6A modification in dysregulation of Wnt/β-catenin pathway in cancer

N6-methyladenosine (m⁶A) modification is the most abundant post-transcriptional regulation of RNAs in eukaryotes. Dysregulation of m⁶A readers, writers, and erasers can significantly promote tumorigenesis by altering the expression of various genes. Wnt/β-catenin is an evolutionarily conserved signaling pathway that has recently been linked to the pathogenesis of many cancers. Given the significance of this pathway in regulating normal tissue homeostasis and stem cell differentiation, a subtle understanding of the molecular mechanism underlying its dysregulation is required for effective targeting. There is mounting evidence that m⁶A regulators are highly implicated in the dysregulation of the Wnt/β-catenin signaling pathway. Since m⁶A regulators can affect Wnt pathway components and dysregulation of either leads to carcinogenesis, this study aims to clarify the relationship between m⁶A regulators and the Wnt/β-catenin signaling pathway to investigate their combined impact on tumorigenesis.

N6-Methyladenosine RNA Modification in Normal and Malignant Hematopoiesis

Over 170 nucleotide variants have been discovered in messenger RNAs (mRNAs) and non-coding RNAs so far. However, only a few of them, including N6-methyladenosine (m6A), 5-methylcytidine (m5C), and N1-methyladenosine (m1A), could be mapped in the transcriptome. These RNA modifications appear to be dynamically regulated, with writer, eraser, and reader proteins being identified for each modification. As a result, there is a growing interest in studying their biological impacts on normal bioprocesses and tumorigenesis over the past few years. As the most abundant internal modification in eukaryotic mRNAs, m6A plays a vital role in the post-transcriptional regulation of mRNA fate via regulating almost all aspects of mRNA metabolism, including RNA splicing, nuclear export, RNA stability, and translation. Studies on mRNA m6A modification serve as a great example for exploring other modifications on mRNA. In this chapter, we will review recent advances in the study of biological functions and regulation of mRNA modifications, specifically m6A, in both normal hematopoiesis and malignant hematopoiesis. We will also discuss the potential of targeting mRNA modifications as a treatment for hematopoietic disorders.

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.

Down-regulated m6A reader FTO destabilizes PHF1 that triggers enhanced stemness capacity and tumor progression in lung adenocarcinoma

Aberrant epigenetic drivers or suppressors contribute to LUAD progression and drug resistance, including KRAS, PTEN, Keap1. Human Plant Homeodomain (PHD) finger protein 1 (PHF1) coordinates with H3K36me3 to increase nucleosomal DNA accessibility. Previous studies revealed that PHF1 is markedly upregulated in various tumors and enhances cell proliferation, migration and tumorigenesis. However, its roles in LUAD are still unknown. We aimed to depict the biological roles of PHF1 and identify useful targets for clinical treatment of LUAD. Based on the bioinformatic analysis, we found that PHF1 was down-regulated in LUAD samples and low PHF1 expressions correlated with unfavorable clinical characteristics. Patients with low PHF1 had poorer survival outcomes relative to those with high PHF1. Targeting PHF1 potentiated cell growth, migration and in vivo proliferation. Mechanistically, FTO mediated the stabilization of PHF1 mRNA by demethylating m6A, which particularly prevented YTHDF2 from degrading PHF1 transcripts. Of note, FTO also expressed lowly in LUAD that predicts poor prognosis of patients. FTO inhibition promoted LUAD progression, and PHF1 overexpression could reverse the effect. Lastly, down-regulated FTO/PHF1 axis could mainly elevate FOXM1 expression to potentiate the self-renewal capacity. Targeting FOXM1 was effective to suppress PHF1^low/− LUAD growth. Collectively, our findings revealed that FTO positively regulates PHF1 expression and determined the tumor-suppressive role of FTO/PHF1 axis, thereby highlighting insights into its epigenetic remodeling mechanisms in LUAD progression and treatment.

RNA N6-Methyladenine Modification, Cellular Reprogramming, and Cancer Stemness

N⁶-Methyladenosine (m⁶A) is the most abundant modification on eukaryote messenger RNA and plays a key role in posttranscriptional regulation of RNA metabolism including splicing, intracellular transport, degradation, and translation. m⁶A is dynamically regulated by methyltransferases (writers), RNA-binding proteins (readers), and demethylases (erasers). Recent studies demonstrate that perturbation of m⁶A regulators remarkably influences cell fate transitions through rewiring various biological processes, such as growth, differentiation, and survival. Moreover, aberrant m⁶A modification is implicated in a variety of diseases, in particular cancer. In this review, we describe the functional linkage of m⁶A modifications to cellular reprogramming and cancer stemness properties.

YTHDF2 promotes multiple myeloma cell proliferation via STAT5A/MAP2K2/p-ERK axis

Multiple myeloma (MM) is still incurable partially due to lacking effective therapeutic targets. Aberrant N6-methyladenosine (m6A) RNA modification plays a vital role in many cancers, however few researches are executed in MM. We first screened the m6A-related genes in MM patient cohorts and correlated these genes with patient outcomes. We found that YTHDF2, a well-recognized m6A reader, was increased in MM patients and associated with poor outcomes. Decreased YTHDF2 expression hampered MM cell proliferation in vitro and in vivo, while enforced YTHDF2 expression reversed those effects. The analyses of m6A-RIP-seq and RIP-PCR indicated that STAT5A was the downstream target of YTHDF2, which was binding to the m6A modification site of STAT5A to promote its mRNA degradation. ChIP-seq and PCR assays revealed that STAT5A suppressed MM cell proliferation by occupying the transcription site of MAP2K2 to decrease ERK phosphorylation. In addition, we confirmed that YTHDF2 mediated the unphosphorylated form of STAT5A to inhibit the expression of MAP2K2/p-ERK. In conclusion, our study highlights that YTHDF2/STAT5A/MAP2K2/p-ERK axis plays a key role in MM proliferation and targeting YTHDF2 may be a promising therapeutic strategy.

The Role of N6-Methyladenosine (m6A) Methylation Modifications in Hematological Malignancies

Simple Summary

Recently, despite the common application of various novel therapies (e.g., immunotherapy and stem cell transplantation) in hematologic tumors, hematologic malignancies remain suboptimal and have a worse prognosis due to the lack of donors and their high heterogeneity. Among them, epigenetic alterations (e.g., the abnormal modification of m⁶A) are essential to facilitate the progression of tumors and drug resistance. Our purpose in this study is to pinpoint the molecular targets of pathogenesis, as well as to analyze the oncogenic characteristics of m⁶A modifications. In this article, we, therefore, elaborate on the mechanisms of m⁶A modification and its role in normal hematopoietic regulation and malignant tumorigenesis, thus contributing to the refinement of molecularly targeted therapies.

Abstract

Epigenetics is identified as the study of heritable modifications in gene expression and regulation that do not involve DNA sequence alterations, such as DNA methylation, histone modifications, etc. Importantly, N⁶-methyladenosine (m⁶A) methylation modification is one of the most common epigenetic modifications of eukaryotic messenger RNA (mRNA), which plays a key role in various cellular processes. It can not only mediate various RNA metabolic processes such as RNA splicing, translation, and decay under the catalytic regulation of related enzymes but can also affect the normal development of bone marrow hematopoiesis by regulating the self-renewal, proliferation, and differentiation of pluripotent stem cells in the hematopoietic microenvironment of bone marrow. In recent years, numerous studies have demonstrated that m⁶A methylation modifications play an important role in the development and progression of hematologic malignancies (e.g., leukemia, lymphoma, myelodysplastic syndromes [MDS], multiple myeloma [MM], etc.). Targeting the inhibition of m⁶A-associated factors can contribute to increased susceptibility of patients with hematologic malignancies to therapeutic agents. Therefore, this review elaborates on the biological characteristics and normal hematopoietic regulatory functions of m⁶A methylation modifications and their role in the pathogenesis of hematologic malignancies.