PDGFRα

引言 胶质瘤是中枢神经系统中最常见的恶性肿瘤，预后极差，其转化机制涉及多种基因突变。PRC2是一个组蛋白甲基化酶复合物，其催化亚基EZH2在肿瘤抑制基因的沉默中起关键作用。PRC2通过在组蛋白H3的第27个赖氨酸上添加甲基标记（H3K27Me3）来沉默基因【1】。EZH2可以与多种RNA结合，包括富含鸟嘌呤的序列和RNA四重氢键 (rG4)【2】。尽管 EZH2-RNA结合的选择性存在争议，但一些lncRNA的功能与其PRC2结合能力相关。HOXDeRNA是一种增强子相关的lncRNA，在正常脑组织中沉默，但在胶质瘤中普遍激活【3】。高水平的HOXDeRNA与胶质瘤进展和GBM患者生存期缩短相关。之前的研究表明，在胶质瘤细胞中靶向激活HOXDeRNA会促进其转化为胶质瘤样细胞。但是，HOXDeRNA是如何通过其RNA四重氢键结构与EZH2相互作用，从而在整体范围内激活癌症转录程序和超级增强子的，目前尚不清楚。 近日，来自美国波士顿布莱根妇女医院哈佛医学院神经病学系的Anna M. Krichevsky研究团队在在Molecular Cell杂志上发表题为HOXDeRNA activates a cancerous transcription program and super enhancers via genome-wide binding的研究论文，该研究发现了lncRNA HOXDeRNA通过与EZH2结合并消除其抑制作用，在胶质瘤中激活了广泛的癌症转录程序和超级增强子，从而将星形胶质细胞转化为类似于胶质瘤干细胞的细胞。 研究人员通过CRISPR系统激活HOXDeRNA后，观察到星形胶质细胞从贴壁生长转变为形成球形，形态发生显著变化。转录组分析揭示了HOXDeRNA激活后，大量基因表达发生改变，包括细胞粘附、生长因子和酪氨酸激酶相关基因，以及35个关键的胶质瘤转录因子(TFs)。这些TFs不仅包括SOX2和OLIG2等干细胞相关TFs，还包括EGFR、PDGFRA、BRAF和TERT 等已知的癌症驱动基因。这些基因的激活定义了转化后星形胶质细胞的转录组和胶质瘤样身份，表明HOXDeRNA在驱动星形胶质细胞向胶质瘤转化中发挥重要作用。 研究人员利用ChIRP-seq和iMARGI技术揭示了HOXDeRNA在星形胶质细胞和胶质瘤干细胞中与基因组广泛的结合，主要位于基因启动子和外显子区域。HOXDeRNA结合的基因在正常脑组织和胶质瘤细胞中通常被PRC2标记沉默，但在转化后失去PRC2标记并表达上调。这表明HOXDeRNA通过与PRC2结合并去除其抑制作用来激活这些基因，从而在胶质瘤发生发展中发挥关键作用。 iMARGI和ChIRP-seq分析发现，HOXDeRNA主要与表达上调的基因的CpG岛结合，而CpG 岛通常位于基因启动子区域。这些超级增强子（super enhancers，SEs）与SOX2和OLIG2等TFs的结合位点高度富集，表明这些TFs可能调节这些SEs。通过敲低SOX2和OLIG2，可以显著降低胶质瘤SEs的活性，并减少球形形成，表明这些TFs对SEs的激活和星形胶质细胞的转化至关重要。此外，SOX2和OLIG2敲低还导致SEs相关基因表达下调，表明SEs激活可能介导了HOXDeRNA对基因表达的影响。 研究人员通过CLIP实验发现EZH2与未剪接的HOXDeRNA结合，而不是成熟型HOXDeRNA。通过CRISPR基因编辑，敲除HOXDeRNA中的rG4结构会降低其与EZH2的结合并减少PRC2 标记的基因的激活。这些结果表明，EZH2可能招募核内的HOXDeRNA到染色质上，而rG4 结构介导了这种结合。此外，敲除 rG4-1 结构会降低星形胶质细胞的转化能力，表明rG4-1 结构在HOXDeRNA的转化功能中发挥重要作用。 图1 HOXDeRNA 通过与基因组广泛结合激活癌症转录程序和超级增强子（Credit: Molecular Cell） 总之，该研究揭示了长链非编码RNA HOXDeRNA在胶质瘤发生发展中的关键作用机制。发现了HOXDeRNA通过rG4结构结合EZH2并招募到PRC2标记的基因组区域，从而去除PRC2对关键胶质瘤转录因子和超级增强子的抑制，最终激活多个癌症驱动基因，驱动星形胶质细胞向胶质瘤转化。这项研究为胶质瘤的发病机制提供了新的见解，并为开发新的治疗策略提供了潜在的靶点。 参考文献 1. Cao, R., and Zhang, Y. (2004). The functions of E(Z)/EZH2-mediated methylation of lysine 27 in histone H3. Curr. Opin. Genet. Dev. 14, 155-164. 2. Wang, X., Goodrich, K.J., Gooding, A.R., Naeem, H., Archer, S., Paucek, R.D., Youmans, D.T., Cech, T.R., and Davidovich, C. (2017). Targeting of polycomb repressive complex 2 to RNA by short repeats of consecutive guanines. Mol. Cell 65, 1056-1067.e5. 3. Deforzh, E., Uhlmann, E.J., Das, E., Galitsyna, A., Arora, R., Saravanan, H., Rabinovsky, R., Wirawan, A.D., Teplyuk, N.M., El Fatimy, R., et al. (2022). Promoter and enhancer RNAs regulate chromatin reorganization and activation of miR-10b/HOXD locus, and neoplastic transformation in glioma. Mol. Cell 82, 1894–1908.e5. https://doi.org/10.1016/j.molcel.2024.09.018 责编|探索君 排版|探索君 来源|BioArt End 往期精选 围观 一文读透细胞死亡(Cell Death) | 24年Cell重磅综述（长文收藏版） 热文 Cell | 是什么决定了细胞的大小？ 热文 Nature | 2024年值得关注的七项技术 热文 Nature | 自身免疫性疾病能被治愈吗？科学家们终于看到了希望 热文 CRISPR技术进化史 | 24年Cell综述

PRESS RELEASE AB SCIENCE PROVIDES AN UPDATE ON THE APPLICATION FOR CONDITIONAL MARKETING AUTHORISATION OF MASITINIB IN THE TREATMENT OF AMYOTROPHIC LATERAL SCLEROSIS Paris, 17 October, 2024, 7.30pm CET AB Science SA (Euronext - FR0010557264 - AB) today announces that the European Medicines Agency (EMA) confirmed a negative opinion for the conditional marketing authorization of masitinib in the treatment of amyotrophic lateral sclerosis (ALS), following a vote adopted during the Committee for Medicinal Products for Human Use (CHMP) meeting on 14-17 October 2024. The Conditional Marketing Authorization of masitinib had been under review by the CHMP in response to the company’s request for a re-examination of the negative opinion issued in June 2024. Despite the difficulty of a conditional marketing authorization in ALS, AB Science had asked for a re-examination first and foremost considering the urgent need for patients to have early access to a promising treatment and the clinical data obtained from the first study AB10015, showing an increase in median overall survival of + 6 months (p= 0.0761) in the primary analysis population of Normal progressors, and a significant + 12 months survival benefit (p=0.0192) in a subgroup defined as patients prior to any complete loss of function (i.e. excluding patient with an ALSFRS-R score of 0 in any of the 12 items of the scale). A Scientific Advisory Group – Neurology (SAG-N) was conveyed for the first time, as part of the re-examination procedure. Importantly, the SAG-N experts agreed with the categorization approach to distinguish between Normal and Fast Progressors (and with the 1.1 points per month ALSFRS decline from onset as cut-off), if properly pre-specified. This opinion supports the design of the confirmatory study of masitinib in ALS, as the same dichotomization and the same cut-off have been pre-specified for the confirmatory study. The phase 2B/3 study AB10015 is considered hypothesis generating but not sufficient as a single pivotal study to support a marketing authorization. Separately, Health Canada recently informed AB Science that key analyses presented for the reconsideration submitted in May 2024 [1], have been considered as new data, rather than re-analyses of existing data. Considering that Health Canada guideline prevent the use of new data as part of the re-examination procedure, AB Science has decided to notify Health Canada it will not pursue the reconsideration. Health Canada has offered the possibility to submit a new application to resolve this issue. Alain Moussy, CEO and co-founder of AB Science said “ We are thankful to the patients and physicians that supported the re-examination process as part of the EMA review. We did all these efforts for the patients. We are convinced that masitinib is a promising drug when we see patients from the study surviving with the drugs for more than 10 years in our compassionate use program. Now AB Science objective is to focus on the confirmatory phase 3 program of masitinib in ALS to reach full approval ”. References [1] AB Science press release dated 3 April 2024 About AB Science Founded in 2001, AB Science is a pharmaceutical company specializing in the research, development and commercialization of protein kinase inhibitors (PKIs), a class of targeted proteins whose action are key in signaling pathways within cells. Our programs target only diseases with high unmet medical needs, often lethal with short term survival or rare or refractory to previous line of treatment. AB Science has developed a proprietary portfolio of molecules and the Company’s lead compound, masitinib, has already been registered for veterinary medicine and is developed in human medicine in oncology, neurological diseases, inflammatory diseases and viral diseases. The company is headquartered in Paris, France, and listed on Euronext Paris (ticker: AB). Further information is available on AB Science’s website: . Forward-looking Statements - AB Science This press release contains forward-looking statements. These statements are not historical facts. These statements include projections and estimates as well as the assumptions on which they are based, statements based on projects, objectives, intentions and expectations regarding financial results, events, operations, future services, product development and their potential or future performance. These forward-looking statements can often be identified by the words “expect”, “anticipate”, “believe”, “intend”, “estimate” or “plan” as well as other similar terms. While AB Science believes these forward-looking statements are reasonable, investors are cautioned that these forward-looking statements are subject to numerous risks and uncertainties that are difficult to predict and generally beyond the control of AB Science and which may imply that results and actual events significantly differ from those expressed, induced or anticipated in the forward-looking information and statements. These risks and uncertainties include the uncertainties related to product development of the Company which may not be successful or to the marketing authorizations granted by competent authorities or, more generally, any factors that may affect marketing capacity of the products developed by AB Science, as well as those developed or identified in the public documents published by AB Science. AB Science disclaims any obligation or undertaking to update the forward-looking information and statements, subject to the applicable regulations, in particular articles 223-1 et seq. of the AMF General Regulations. For additional information, please contact: AB Science Financial Communication & Media Relations investors@ab-science.com Attachment CP ALS REGUL EMA VENG VF

*仅供医学专业人士阅读参考 1961年，科学家首次描述了细胞衰老（senescence）的概念，这一机制在癌症、衰老和多种年龄相关疾病中起着至关重要的作用。此前的一些研究发现，通过遗传学或者药理学方法，消除以p16Ink4a（细胞周期蛋白依赖性激酶抑制蛋白）为标志物的衰老细胞，可以延长早衰小鼠的寿命，减轻衰老小鼠的年龄相关表型，改善多种年龄相关疾病。 然而，也有研究显示，完全清除衰老细胞并不是最佳策略，这些衰老细胞中可能仍有部分具有正常的生理功能性。因此，了解不同衰老细胞的病理生理作用，靶向性清除特定类型的衰老细胞，可能是更好的策略。 为此，中国科学院分子细胞科学卓越创新中心的周斌研究员带领研究团队在《细胞》杂志上发表了最新研究成果[1]，他们开发了一个包含三种p16Ink4a相关交叉遗传系统的体内遗传学工具集，可以追踪、消融和调控p16Ink4a+细胞。 以肝损伤和修复为例，研究人员发现，巨噬细胞和内皮细胞代表了不同的衰老细胞类型，清除p16Ink4a+巨噬细胞能够减轻肝细胞损伤，而清除p16Ink4a+内皮细胞则加重了肝损伤，另外，重编程p16Ink4a+内皮细胞显著减少了肝纤维化。这表明了p16Ink4a+衰老细胞的功能多样性，为未来开发细胞类型特异性的衰老细胞清除疗法提供了基础。 为了在单细胞水平上鉴定表达p16Ink4a的细胞类型，研究人员首先创建了一种新的荧光报告基因系p16-tdT，并分离小鼠胚胎成纤维细胞进行重复传代，诱导细胞衰老。随着细胞传代次数增加，表达tdT的细胞比例显著增加。与第二代相比，第六代和第七代细胞的p16蛋白水平也显著增加，这些细胞同样表达tdT，意味着p16-tdT能够反映p16的表达情况。 在老年小鼠中，p16Ink4a+细胞在不同器官中的身份是多样化的，例如大脑中的p16Ink4a+细胞主要是皮层神经元，而胰腺中是各种胰岛内分泌细胞，这些细胞有明显更强的衰老相关β半乳糖苷酶（SA-β-Gal）活性、更弱的增殖能力和更高的衰老相关分泌表型（SASP）因子表达，证实了它们的衰老细胞性质。 不同器官中主要的衰老细胞类型 肝纤维化是肌成纤维细胞活化的结果，细胞衰老与肝纤维化具有因果关联。在诱导肝纤维化的小鼠中，研究人员也观察到了部分位置的tdT富集，与SA-β-Gal相一致。在肝脏不同类型的细胞中，成纤维细胞、内皮细胞和巨噬细胞的一组呈p16Ink4a+，由于衰老成纤维细胞与肝损伤和疾病的研究已经相当深入，研究人员决定把目光放在内皮细胞与巨噬细胞上。 为了检测不同类型的p16Ink4a+细胞在肝损伤和修复中的最终命运，研究人员开发了一个名为衰老细胞脉冲追踪示踪器（Sn-pTracer）的遗传系统。 对巨噬细胞和内皮细胞的追踪显示，肝损伤后，p16Ink4a+巨噬细胞显著增加，但在修复后大量凋亡，而p16Ink4a+内皮细胞在损伤后增加的同时，在修复阶段也有大量存活，表明细胞衰老可能是一种细胞周期停滞的暂时形式，根据细胞类型决定是否可逆。 在接下来的实验中，由于Sn-pTracer需要对小鼠进行频繁的处理，并且可能对小鼠有害，研究人员进行了优化，开发了衰老细胞Cre诱导示踪器（Sn-cTracer），使用白喉毒素处理小鼠，相比对照组的磷酸缓冲液，显著减少了p16Ink4a+巨噬细胞，同时，小鼠的肝纤维化面积显著缩小，纤维化标志物PDGFRα、PDGFRβ和肌间线蛋白水平也显著下降。 纤维化标志物水平下降（M）和肝纤维化减轻（N） 研究人员使用同样的方法对p16Ink4a+内皮细胞进行了检测，内皮细胞减少后，小鼠的肝纤维化恶化，PDGFRα、PDGFRβ和肌间线蛋白水平也有相应的增加。也就是说，p16Ink4a+内皮细胞在功能上是限制肝损伤和纤维化的，p16Ink4a+巨噬细胞则刚好相反。 消除p16Ink4a+巨噬细胞后，小鼠肝纤维化的免疫微环境发生变化，包括T细胞活化、增殖、分化和参与免疫反应的淋巴细胞活化增强，流式细胞术也观察到T细胞和NK细胞的比例显著增加，它们在肝纤维化的限制和消退中起重要作用，因此，特异性消除p16Ink4a+巨噬细胞可能通过促进T细胞的生长和活化限制了肝纤维化。 肝纤维化免疫微环境中T细胞和淋巴细胞变化 相反，消除p16Ink4a+内皮细胞后，小鼠肝纤维化的免疫微环境向促纤维化的方向发生了转变。 通过RNA测序，研究人员还发现，p16Ink4a+内皮细胞中Kdr的表达显著下降，Kdr是血管再生和肝脏修复过程中VEGF信号通路的关键受体。鉴于VEGF信号的激活可以改善内皮细胞功能和肝脏的年龄相关变化，研究人员又设计了可以特异性地调控p16Ink4a+细胞中基因表达的衰老细胞基因操作示踪器（Sn-gTracer）。 利用Sn-gTracer过表达Kdr使得p16Ink4a+内皮细胞重编程后，小鼠的肝纤维化得到了显著改善。 综上所述，不同类型的衰老细胞在器官和组织中具有不同的功能，基于细胞类型的特异性衰老细胞清除可能才是改善年龄相关疾病的关键所在，为衰老细胞清除疗法提供了新的研究工具和研究方向。 参考文献： [1] https://www.cell.com/cell/fulltext/S0092-8674(24)01069-9 本文作者 | 应雨妍