SFRP1

导读：胆管癌(CCA)是指与预后不良相关的一系列恶性肿瘤。目前，手术切除是治疗CCA的唯一方法。可用的全身治疗仅限于吉西他滨加顺铂;然而，这种治疗本质上是治标不治本的。因此，仍然需要探索新的有效的治疗靶点来干预CCA。近日，华中科技大学研究人员在权威期刊《Clinical And Translational Medicine》上发表了题为“Targeting polycomb repressor complex 2-mediated bivalent promoter epigenetic silencing of secreted frizzled-related protein 1 inhibits cholangiocarcinoma progression”的研究论文，本研究中，研究人员分析了EZH2在CCA中的表达和患者预后。通过异种移植模型和原发性CCA小鼠模型，检测并验证了基因敲低和过表达后CCA细胞的增殖、迁移和侵袭能力。针对DNA甲基化，在EZH2和SUZ12敲除的CCA细胞中进行了基于RNA测序的转录组学分析。数据强烈表明，靶向PRC2可促进SFRP1的表达，从而抑制CCA的进展。https://onlinelibrary.wiley.com/doi/full/10.1002/ctm2.1502研究背景 01 胆管癌(CCA)是指与预后不良相关的一系列恶性肿瘤。在全球许多国家，CCA的发病率呈上升趋势。目前，手术切除是唯一有效的治疗选择。然而，不幸的是，在诊断时，几乎三分之二的CCA患者已经患有晚期疾病。此外，即使在切除后，仍有相当比例的患者(68%至86%)经历局部或远处肿瘤复发。目前，CCA患者可用的全身治疗仅限于吉西他滨+顺铂，这仍然是标准的化疗选择。然而，这种治疗是治标不治本的，收效甚微。因此，仍然需要探索新的药物靶点来进行CCA治疗干预。多梳抑制复合物2 (PRC2)由EZH2、SUZ12和EED三个核心因子组成，作为染色质相关的甲基转移酶，催化组蛋白H3上赖氨酸27的单、二和三甲基化(H3K27)。PRC2是唯一在H3K27上具有活性的甲基转移酶，EZH2作为PRC2的催化亚基，但需要EED和SUZ12的物理存在才能产生催化活性。多项研究证明，PRC2在血液学和实体肿瘤中都具有致癌特性。此外，其亚基在前列腺癌、乳腺癌、肺癌、膀胱癌和胰腺癌等多种癌症中均存在显著失调。PRC2的作用包括通过多种机制促进癌症进展。首先，PRC2催化赖氨酸27处组蛋白H3的甲基化，即H3K27me3，它与癌症转移和生长有关。此外，EZH2具有非组蛋白甲基化酶催化活性，这也有助于癌症的进展。目前还没有足够的证据来确定PRC2是否有助于CCA的进展并在CCA中发挥作用。研究进展 02 大量研究揭示了PRC2在癌症进展中的重要作用，并表明它可能是一个有用的治疗靶点。从PRC2的分子功能来看，它在肿瘤细胞的起源和肿瘤的发展过程中建立了一些基因的抑制状态。EZH2是PRC2复合体的一个酶亚基，通过其催化和非催化活性在肿瘤发展中发挥重要作用。靶向EZH2治疗肿瘤是当前涉及肿瘤免疫、肿瘤代谢和肿瘤耐药的研究课题。在本研究中，研究人员从临床数据、CCA细胞、异种移植小鼠和原代CCA模型中证实了PRC2的核心催化亚基EZH2的致癌作用。研究人员发现，敲除PRC2的三个核心亚基(EZH2、SUZ12和EED)以及EZH2抑制剂GSK126、GSK343，会损害PRC2特异性H3K27me3的催化功能，并进一步导致SFRP1启动子的DNA低甲基化和SFRP1的转录激活。研究人员之前证实了SFRP1是CCA中DNA甲基化转录的高度调控基因。研究表明PRC2和DNA甲基化共同保护癌症中的肿瘤细胞。事实上，EZH2作为募集DNA甲基转移酶的平台，是某些基因启动子中DNA甲基化所必需的。在一些肿瘤中，EZH2可以募集DNA甲基转移酶到相关基因的启动子区域，促进DNA甲基化。研究人员也证实了组蛋白修饰的沉积不足以抑制靶基因的转录。其原因是靶基因的表达受到H3K27me3和DNA甲基化的二价表观遗传调控。从本研究结果来看，敲除CCA中PRC2的三个亚基之一会导致其他两个亚基的蛋白水平降低，这两个亚基也会损害PRC2的H3K27me3催化功能。相反，SUZ12的转录后修饰通过增强PRC2功能促进催化和抑制靶基因。针对EZH2，目前出现了多种抑制剂，包括针对EZH2特异性H3K27me3催化活性的抑制剂和降低EZH2或EED蛋白水平的抑制剂。包括地西他滨在内的DNA甲基转移酶抑制剂对DNMT3a、DNMT3b和DNMT1具有显著的抑制作用，已被批准用于治疗血液肿瘤和向实体肿瘤扩展。然而，它非特异性地降低全基因组甲基化并导致基因组不稳定，这反过来增加了肿瘤增殖和侵袭的风险。因此，一种新的抗癌思路是通过EZH2抑制剂靶向prc2介导的DNA超甲基化引起的肿瘤进展。在体外和体内，抑制EZH2可破坏胆管癌(CCA)的进展研究结论 03 本研究为PRC2在CCA中的作用和潜在机制提供了深入的见解。它主要针对PRC2介导的H3K27me3和DNA超甲基化，导致SFPR1的二价启动子表观遗传沉默，抑制CCA的进展。这些发现表明，靶向PRC2，例如使用EZH2抑制剂，可能是开发CCA抗癌药物的一种有希望的方法。参考资料：https://onlinelibrary.wiley.com/doi/full/10.1002/ctm2.1502识别微信二维码，添加生物制品圈小编，符合条件者即可加入生物制品微信群！请注明：姓名+研究方向！版权声明本公众号所有转载文章系出于传递更多信息之目的，且明确注明来源和作者，不希望被转载的媒体或个人可与我们联系(cbplib@163.com)，我们将立即进行删除处理。所有文章仅代表作者观点，不代表本站立场。

A team of researchers reconstructed long-extinct proteins of a UV protection system of cyanobacteria. The surprising result: the proteins were already compatible with each other when they first met. This discovery expands the knowledge horizon on the rules of evolution. Proteins are the key players for virtually all molecular processes within the cell. To fulfil their diverse functions, they have to interact with other proteins. Such protein-protein interactions are mediated by highly complementary surfaces, which typically involve many amino acids that are positioned precisely to produce a tight, specific fit between two proteins. However, comparatively little is known about how such interactions are created during evolution. Classical evolutionary theory suggests that any new biological feature involving many components (like the amino acids that enable an interaction between proteins) evolves in a stepwise manner. According to this concept, each tiny functional improvement is driven by the power of natural selection because there is some benefit associated with the feature. However, whether protein-protein interactions also always follow this trajectory was not entirely known. Using a highly interdisciplinary approach, an international team led by Max Planck researcher Georg Hochberg from the Terrestrial Microbiology in Marburg have now shed new light on this question. Their study provides definitive evidence that highly complementary and biologically relevant protein-protein interactions can evolve entirely by chance. Proteins cooperate in a photoprotection system The research team made their discovery in a biochemical system that microbes use to adapt to stressful light conditions. Cyanobacteria use sunlight to produce their own food through photosynthesis. Since much light damages the cell, cyanobacteria have evolved a mechanism known as photoprotection: if light intensities become dangerously high, a light intensity sensor named Orange Carotenoid Protein (OCP) changes its shape. In this activated form, OCP protects the cell by converting excess light energy into harmless heat. In order to return into its original state, some OCPs depend on a second protein: The Fluorescence Recovery Protein (FRP) binds to activated OCP1 and strongly accelerates its recovery. 'Our question was: Is it possible that the surfaces that allow these two proteins to form a complex evolved entirely by accident, rather than through direct natural selection?' says Georg Hochberg. 'The difficulty is that the end result of both processes looks the same, so we usually cannot tell why the amino acids required for some interaction evolved -- through natural selection for the interaction or by chance. To tell them apart, we would need a time machine to witness the exact moment in history these mutations occurred, 'Georg Hochberg explains. Luckily, recent breakthroughs in molecular and computational biology has equipped Georg Hochberg and his team with a laboratory kind of time machine: ancestral sequence reconstruction. In addition, the light protection system of cyanobacteria, which is under study in the group of Thomas Friedrich from Technische Universität Berlin since many years, is ideal for studying the evolutionary encounter of two protein components. Early cyanobacteria acquired the FRP proteins from a proteobacterium by horizontal gene transfer. The latter had no photosynthetic capacity itself and did not possess the OCP protein. To work out how the interaction between OCP1 and FRP evolved, graduate student Niklas Steube inferred the sequences of ancient OCPs and FRPs that existed billions of years ago in the past, and then resurrected these in the laboratory. After translation of the amino acid sequences into DNA he produced them using E. coli bacterial cells in order to be able to study their molecular properties. A fortunate coincidence The Berlin team then tested whether ancient molecules could form an interaction. This way the scientists could retrace how both protein partners got to know each other. 'Surprisingly, the FRP from the proteobacteria already matched the ancestral OCP of the cyanobacteria, before gene transfer had even taken place. The mutual compatibility of FRP and OCP has thus evolved completely independently of each other in different species, says Thomas Friedrich. This allowed the team to prove that their ability to interact must have been a happy accident: selection could not plausibly have shaped the two proteins' surfaces to enable an interaction if they had never met each other. This finally proved that such interactions can evolve entirely without direct selective pressure. 'This may seem like an extraordinary coincidence,' Niklas Steube says. 'Imagine an alien spaceship landed on earth and we found that it contained plug-shaped objects that perfectly fit into human-made sockets. But despite the perceived improbability, such coincidences could be relatively common. But in fact, proteins often encounter a large number of new potential interaction partners when localisation or expression patterns change within the cell, or when new proteins enter the cell through horizontal gene transfer.' Georg Hochberg adds, 'Even if only a small fraction of such encounters ends up being productive, fortuitous compatibility may be the basis of a significant fraction of all interactions we see inside cells today. Thus, as in human partnerships, a good evolutionary match could be the result of a chance meeting of two already compatible partners.'

Morphogens are the secreted molecules that pattern embryonic tissues. These molecules are important not only for the embryo during development, but also for the adult during tissue repair. However, the way these morphogens are distributed to ensure patterning occurs is still not fully understood. Using a combination of experiments and mathematical modeling, researchers learned more about the role morphogens play in tissue patterning. Their results are relevant to medical applications, such as drug design. Morphogens are molecules that travel from biological cell to cell to pattern tissues in the embryo. These molecules are important not only for the embryo during development, but also for the adult during tissue repair. However, the way these morphogens are distributed to ensure patterning occurs is still not fully understood. Using a combination of experiments and mathematical modeling, a research team from the University of Tokyo and their international collaborators has learned more about the role morphogens play in tissue patterning. The results are relevant to medical applications, such as drug design. The team's findings are published in the journal eLife. The Wnt morphogen has emerged as a key regulator of heart development in vertebrates. These Wnt proteins are molecules that play an important role in cell development. However, it is still generally unclear to scientists exactly how Wnt regulates heart development. There are differences among the vertebrate classes, as well as redundancy in some species. However, scientists can study how Wnt regulates heart development in the Xenopus, an aquatic frog that is native to sub-Saharan Africa. The Xenopus, with its lungs and three-chamber heart, is cost-effective and useful to scientists in their study of human diseases. In Xenopus heart development, scientists have already established that the Wnt6 morphogen is sent out by the epidermis, those outer layers of cells that make up the skin, to pattern the cardiogenic mesoderm, which is the group of cells in the embryo that will form the heart. From this patterning, a relatively thin pericardium (the membrane around the heart) and a broad myocardium (the heart's muscular tissue) develop. Scientists are still working to better understand how the Wnt6 morphogen distribution is regulated to ensure reproducible positioning of the pericardium and myocardium in the cardiogenic mesoderm. "It is still unclear how reproducible patterning can be achieved with diffusing molecules, especially when that patterning concerns differentiation of thin tissues." said Takayoshi Yamamoto, an assistant professor at the University of Tokyo and the first author and corresponding on the paper. Scientists do know that in early embryo development, the range of Wnt8 morphogen signaling is precisely regulated heparan sulfate and secreted Wnt binding proteins, including Frzb (which is also known as sFRP3). Heparan sulfate is a carbohydrate that is important is embryo development. Wnt signaling is one of the main processes by which tissue takes shape during the development of the embryo. The research team wondered whether mechanisms similar to those that operate in early embryos also regulate distribution of Wnt6 morphogen in the cardiogenic mesoderm. The Wnt receptor, Frizzled7, is essential for heart development. The expression of Frizzled7 is increased by Wnt signaling in the development of the nervous system in the Xenopus and in the development of human embryonic carcinoma cells, but there are no such reports in heart development. So the research team focused their study to analyze the way Wnt signaling occurs in the development of the heart, focusing on the extracellular components -- the Frizzled7 cell-surface receptor, sFRP1 (an inhibitor of Wnt6 that can also travel from cell to cell) and heparan sulfate. "With a combination of experiments and mathematical modeling, this receptor-feedback appears essential to shape a steep gradient of Wnt signaling. In addition, computer simulation revealed that this feedback imparts robustness against variations of Wnt ligand production and allows the system to reach a steady state quickly," said Yamamoto. Wnt6 and sFRP1 molecules not only regulate normal heart development in the embryo, but also regulate repair and regeneration after heart muscle injury, such as in the case of a myocardial infarction, or heart attack. "Our findings will be relevant to medical applications, for example, for drug design, since cell-surface molecules such as Frizzled or a specific modification of heparan sulfate or even the secreted molecule sFRP1, generally provide better drug targets than molecules inside cells. To reveal the precise regulation of morphogens and to consider medical applications, regulatory mechanisms of these components must be investigated further," said Yamamoto. The research was conducted in collaboration with researchers at the University of Aberdeen in the U.K.