The interplay between m6A modification and non-coding RNA in cancer stemness modulation: mechanisms,signaling pathways,and clinical implications

Cancer stemness, mainly consisting of chemo-resistance, radio-resistance, tumorigenesis, metastasis, tumor self-renewal, cancer metabolism reprogramming, and tumor immuno-microenvironment remodeling, play crucial roles in the cancer progression process and has become the hotspot of cancer research field in recent years. Nowadays, the exact molecular mechanisms of cancer stemness have not been fully understood. Extensive studies have recently implicated that non-coding RNA (ncRNA) plays vital roles in modulating cancer stemness. Notably, N6-methyladenosine (m6A) modification is of crucial importance for RNAs to exert their biological functions, including RNA splicing, stability, translation, degradation, and export. Emerging evidence has revealed that m6A modification can govern the expressions and functions of ncRNAs, consequently controlling cancer stemness properties. However, the interaction mechanisms between ncRNAs and m6A modification in cancer stemness modulation are rarely investigated. In this review, we elucidate the recent findings on the relationships of m6A modification, ncRNAs, and cancer stemness. We also focus on some key signaling pathways such as Wnt/β-catenin signaling, MAPK signaling, Hippo signaling, and JAK/STAT3 signaling to illustrate the underlying interplay mechanisms between m6A modification and ncRNAs in cancer stemness. In particular, we briefly highlight the clinical potential of ncRNAs and m6A modifiers as promising biomarkers and therapeutic targets for indicating cancer stemness properties and improving the diagnostic precision for a wide variety of cancers.     

环状RNA的m6A修饰在肿瘤中的作用

环状RNA(circular RNA,circRNA)是一种具有新型环状结构的RNA分子,广泛存在于多种生物体中,具有结构稳定、进化保守、高度丰富和组织特异性等特征。同时,它可通过充当微小RNA(microRNA,miRNA)分子海绵、调控基因转录、结合蛋白质和参与蛋白质翻译等方式发挥生物学功能。且随着高通量测序技术和生物信息学的迅速发展,越来越多的circRNA被发现与肿瘤的发生有关。N6-甲基腺嘌呤(N6-methyladenosine,m6A)修饰是真核生物最常见的一种RNA修饰,它是由m6A甲基转移酶、去甲基化酶和m6A识别蛋白质共同参与的动态可逆的调节过程,广泛参与RNA的核输出、剪接、稳定性、翻译和降解等过程的调控。m6A修饰在多种人类疾病中发挥关键作用,例如癌症和心血管疾病等。近年来,在一些circRNA中也发现了m6A修饰,并报道了其在宫颈癌、结直肠癌、肝细胞癌、非小细胞肺癌和胃低分化腺癌等多种恶性肿瘤发生发展中的作用。本文总结了RNA m6A修饰机制、m6A修饰对circRNA的调控作用,以及circRNA的m6A修饰在肿瘤中的作用,也讨论了m6A修饰的circRNA的潜在临床应用价值,以期为肿瘤的早期诊断、临床治疗和预后判断提供新的思路与途径。     

Trophinin is a potent prognostic marker of ovarian cancer involved in platinum sensitivity

Ovarian cancer is the leading cause of death in women with gynecological malignancies, with prognosis of advanced stage tumors determined by chemotherapeutic response and the success of tumor resection. Since aberrant RAS pathway activation is frequent in ovarian cancer, study of in vitro RAS-induced transformation and accompanying genomic expression changes in ovarian surface epithelial cells is imperative for development of new therapeutic modalities and for understanding tumorigenesis. cDNA microarray analysis revealed TROPHONIN (TRO), a homophilic adhesion molecule involved in blastocyst implantation, was among the genes most downregulated by RAS induction. TRO expression is higher in cisplatin-sensitive cancer cell lines and positively correlates with prognoses in ovarian cancers. TRO knockdown by RNA interference conferred cisplatin resistance and led to increased invasiveness of cultured ovarian cancer cells. These findings underscore the importance of TRO in tumorigenesis, and suggest that TRO may be a useful biomarker for cisplatin sensitivity and invasive potential.     

m^6 A RNA甲基化修饰异常在肿瘤中的作用

N6-甲基腺嘌呤(N6-methyladenosine,m6A)是真核生物信使RNA(messenger RNA,mRNA)含量最多的化学修饰之一。m6A修饰主要由m6A甲基转移酶(methyltransferase)催化,m6A去甲基酶(demethylase)去除,并由m6A结合蛋白(binding protein)识别。它广泛参与调控mRNA剪接、加工、翻译和降解等生命周期的各个阶段,且与肥胖和肿瘤等多种疾病及异常的生理功能相关。近年的研究发现,肿瘤中m6A相关蛋白质(METTL3/14、WTAP、FTO、ALKBH5、YTHDFs)的异常表达,引发m6A甲基化的失调,调控致癌基因和抑癌基因的表达参与肿瘤的发生与发展,并与患者预后不良密切相关。随着RNA免疫沉淀测序技术与高通量测序技术和液相色谱等检测技术的快速发展,有关m6A在肿瘤发生发展中的作用机制研究的进展迅猛,靶向m6A也成为肿瘤临床治疗的新方向。本文重点对m6A RNA甲基化相关因子在癌症发生发展中的作用及机制进行综述,总结m6A RNA甲基化检测技术的最新进展,梳理现有文献报道的脱甲基酶抑制剂大黄酸、甲氯芬那酸2(meclofenamic acid2,MA2)和右旋羟戊二酸(R-2-hydroxyglutarate,R-2HG)等在肿瘤靶向治疗中的运用,为以m6A RNA甲基化为切入点的肿瘤防治研究提供思路与理论参考。     

Linking the YTH domain to cancer: the importance of YTH family proteins in epigenetics

N6-methyladenosine (m6A), the most prevalent and reversible modification of mRNA in mammalian cells, has recently been extensively studied in epigenetic regulation. YTH family proteins, whose YTH domain can recognize and bind m6A-containing RNA, are the main “readers” of m6A modification. YTH family proteins perform different functions to determine the metabolic fate of m6A-modified RNA. The crystal structure of the YTH domain has been completely resolved, highlighting the important roles of several conserved residues of the YTH domain in the specific recognition of m6A-modified RNAs. Upstream and downstream targets have been successively revealed in different cancer types and the role of YTH family proteins has been emphasized in m6A research. This review describes the regulation of RNAs by YTH family proteins, the structural features of the YTH domain, and the connections of YTH family proteins with human cancers.Subject terms: Cancer, Epigenetics     

Integrative Analyses of m6A Regulators Identify that METTL3 is Associated with HPV Status and Immunosuppressive Microenvironment in HPV-related Cancers

Although m6A modifications are associated with tumor progression, and anti-tumor immune responses, the role of m6A regulators in HPV-related carcinogenesis has not been well resolved. To provide evidence for the role of m6A regulators in HPV-related carcinogenesis and identify potential therapeutic targets for HPV-related cancers, integrative analyses of m6A regulators in 1,485 head and neck squamous cell carcinoma (HNSC) patients and 507 cervical squamous cell carcinoma (CESC) patients was performed and identified that an m6A regulator, METTL3, was highly expressed in tumors and was related to the poor prognosis in HNSC and CESC. In HPV-positive tumors, METTL3 was positively associated with tumor HPV status, such as HPV integration status, E6 and unspliced-E6 expression, and p16 expression. Further analysis demonstrated that METTL3 ^high status was negatively correlated with tumor immune cell infiltrations and facilitated the expression of immunosuppressive immune checkpoint molecules (i.e., PD-L1). Cell-derived xenograft models demonstrated that METTL3 inhibitor combined with anti-PD1 therapy promoted immunotherapy of CESC in vivo. Overall, this study identified that METTL3 ^high status, is associated with poor prognosis and HPV status, and serves as a mediator of the immunosuppressive tumor microenvironment in HPV-associated cancer, which provides a promising therapeutic target for anti-cancer immunotherapy.     

RNA methylation-mediated LINC01559 suppresses colorectal cancer progression by regulating the miR-106b-5p/PTEN axis

Long noncoding RNAs (lncRNAs) regulate multiple biological effects in cancers. Recently, RNA methylation has been found to modify not only coding RNAs but also some noncoding RNAs. How RNA methylation affects lncRNAs to affect colorectal cancer (CRC) progression remains elusive. The expression of LINC01559 was explored through RNA sequencing, quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). The preliminary exploration of its function was performed using Western blotting (WB) and immunohistochemistry (IHC). Functional experiments in vitro and in vivo were conducted to explore the biological functions of LINC01559 in CRC. The LINC01559/miR-106-5p/PTEN axis was verified through fluorescence in situ hybridization (FISH), luciferase assays, and rescue experiments. RIP-sequencing, m6A RNA immunoprecipitation (MeRIP) assays and bioinformatic analysis were conducted to determine the upstream mechanism of LINC01559. The results showed that LINC01559 was downregulated in CRC compared with normal controls. Lower expression of LINC01559 in CRC patients predicted a poor prognosis. In addition, PTEN was found to be positively correlated with LINC01559, and miR-106b-5p could be the link between LINC01559 and PTEN. Then, silencing LINC01559 restored the malignant phenotype of CRC cells, while cotransfection of miR-106b-5p inhibitor neutralized this effect. Mechanistically, we found abundant m6A modification sites on LINC01559. Then, we uncovered these sites as potential targets of METTL3 through experiments in vivo. The results revealed a negative functional regulation of the LINC01559/miR-106b-5p/PTEN axis in CRC progression and explored a new mechanism of METTL3-mediated m6A modification on LINC01559. These results elucidate a novel potential therapeutic target for CRC treatment.     

Induction of cytotoxic T cell responses and tumor immunity against unrelated tumors using telomerase reverse transcriptase RNA transfected dendritic cells

The polypeptide component of telomerase (TERT) is an attractive candidate for a broadly expressed tumor rejection antigen because telomerase is silent in normal tissues but is reactivated in more than 85% of cancers. Here we show that immunization against TERT induces immunity against tumors of unrelated origin. Immunization of mice with TERT RNA-transfected dendritic cells (DC) stimulated cytotoxic T lymphocytes (CTL), which lysed melanoma and thymoma tumor cells and inhibited the growth of three unrelated tumors in mice of distinct genetic backgrounds. TERT RNA-transfected human DC stimulated TERT-specific CTL in vitro that lysed human tumor cells, including Epstein Barr virus (EBV)-transformed B cells as well as autologous tumor targets from patients with renal and prostate cancer. Tumor RNA-transfected DC were used as surrogate targets in the CTL assays, obviating the difficulties in obtaining tumor cells from cancer patients. In one instance, where a tumor cell line was successfully established in culture from a patient with renal cancer, the patient's tumor cells were efficiently lysed by the CTL. Immunization with tumor RNA was generally more effective than immunization with TERT RNA, suggesting that an optimal immunization protocol may have to include TERT as well as additional tumor antigens.     

表观遗传学修饰在血液肿瘤中的研究进展

血液肿瘤作为一类常见恶性肿瘤疾病主要包括各类白血病、多发性骨髓瘤以及恶性淋巴瘤.随着现代社会高速发展,人群发病率呈逐年升高趋势,且发病年龄逐渐低龄化,发病原因与环境因素以及遗传因素密不可分.近年来研究发现,表观遗传学修饰在血液肿瘤发生发展的过程中扮演了重要角色,一些相关修饰基因作为血液肿瘤的治疗靶点在临床应用上取得了重要进展.针对近年来表观遗传学修饰在血液肿瘤中的研究新进展,本文将系统综述DNA甲基化、组蛋白修饰、非编码RNA及RNA修饰等在血液肿瘤发病机制方面的研究进展.     

Angiogenesis in gynecological cancers and the options for anti-angiogenesis therapy

Angiogenesis is required in cancer, including gynecological cancers, for the growth of primary tumors and secondary metastases. Development of anti-angiogenesis therapy in gynecological cancers and improvement of its efficacy have been a major focus of fundamental and clinical research. However, survival benefits of current anti-angiogenic agents, such as bevacizumab, in patients with gynecological cancer, are modest. Therefore, a better understanding of angiogenesis and the tumor microenvironment in gynecological cancers is urgently needed to develop more effective anti-angiogenic therapies, either or not in combination with other therapeutic approaches. We describe the molecular aspects of (tumor) blood vessel formation and the tumor microenvironment and provide an extensive clinical overview of current anti-angiogenic therapies for gynecological cancers. We discuss the different phenotypes of angiogenic endothelial cells as potential therapeutic targets, strategies aimed at intervention in their metabolism, and approaches targeting their (inflammatory) tumor microenvironment.     

环状RNA翻译蛋白在癌症中的研究进展北大核心CSCD

环状RNA(circular RNA,circRNA)是一种单链环状闭合RNA分子,由线性RNA通过反向剪接形成,具有稳定、高度保守、组织特异性等特点。circRNA能够通过形成竞争性内源性RNA、结合蛋白等多种方式参与机体的生理、病理过程。最近发现,circRNA分子可以通过翻译形成多肽或蛋白参与癌症的发生和发展。circRNA是人类癌症中有前途的诊断和预后标志物,也是癌症治疗的潜在药物靶点。本文重点介绍了circRNAs编码的多肽和蛋白质在多种癌症中的相关研究进展。这些多肽和蛋白质分别依赖内部核糖体进入位点和m6A两种不同的机制进行翻译。我们还总结了circRNA编码的多肽和蛋白质在各种癌症的诊断、治疗、预后和机制研究中的潜在用途。     

长链脂酰辅酶A合成酶家族与恶性肿瘤

脂肪酸代谢紊乱容易导致癌症的发生。长链脂酰辅酶A合成酶家族(long chain acyl-coenzyme A synthetase family,ACSLs)负责激活长链脂肪酸,在脂肪酸代谢中发挥重要作用。但在癌细胞中,其调控作用经常被解除,细胞内脂肪酸的分布、种类和数量发生改变,进而导致癌症和其他代谢性疾病的发生。ACSLs 在哺乳动物中包括5种亚型,分别为ACSL1、3、4、5和6。ACSL1在甘油三脂的合成和分配中发挥重要作用;ACSL3有助于脂滴的形成,脂滴对维持脂质稳态具有重要作用;ACSL4的表达与类固醇激素相关,在铁死亡途径中发挥重要作用;ACSL5可以催化外源性脂肪酸的代谢,但不能催化从头合成脂肪酸的代谢;ACSL6在脑内的脂肪酸代谢及生殖器官中精子发生和卵巢功能维持等方面发挥重要作用。ACSLs的调控因子包括转录因子、共激活因子、激素受体、蛋白激酶和小的非编码RNA等。它们通过介导脂肪酸代谢,广泛参与线粒体介导的能量代谢,内质网应激和肿瘤炎性微环境等。此外,ACSLs还作为独立预后因素,成为各种癌症临床诊断和治疗的生物标志物和治疗靶点。近年来,越来越多的研究表明,ACSL家族在癌症的发生发展进程中发挥重要作用。本文从ACSL基因家族,ACSLs与恶性肿瘤及基于ACSLs脂代谢的肿瘤治疗方面进行阐述,为后续ACSL基因家族的研究及肿瘤的靶向治疗提供理论依据和候选分子靶标。     

Abnormal alternative splicing promotes tumor resistance in targeted therapy and immunotherapy

Abnormally alternative splicing events are common hallmark of diverse types of cancers. Splicing variants with aberrant functions play an important role in cancer development. Most importantly, a growing body of evidence has supported that alternative splicing might play a significant role in the therapeutic resistance of tumors. Targeted therapy and immunotherapy are the future directions of tumor therapy; however, the loss of antigen targets on the tumor cells surface and alterations in drug efficacy have resulted in the failure of targeted therapy and immunotherapy. Interestingly, abnormal alternative splicing, as a strategy to regulate gene expression, is reportedly involved in the reprogramming of cell signaling pathways and epitopes on the tumor cell surface by changing splicing patterns of genes, thus rendering tumors resisted to targeted therapy and immunotherapy. Accordingly, increased knowledge regarding abnormal alternative splicing in tumors may help predict therapeutic resistance during targeted therapy and immunotherapy and lead to novel therapeutic approaches in cancer. Herein, we provide a brief synopsis of abnormal alternative splicing events in cancer progression and therapeutic resistance.