Role of Siglec-10/G as a tumor suppressor in B-cells

项目摘要/摘要 大约80%的B细胞性非霍奇金淋巴瘤来源于生发中心(GC)B细胞。 GC B细胞内的体细胞高突变是抗体亲和力成熟所必需的，但体细胞突变 也可以驱动表观遗传损伤，提高存活率，维持GC B细胞的过度增殖状态， 并促进淋巴肿大。考虑到GC B细胞对恶性转化的敏感性，它不是 令人惊讶的是，GC内部的自然选择过程被认为有助于防止 恶性克隆人。因此，需要更深入地了解制约GC的因素。签约- 10/G(人/鼠同源基因)是识别唾液酸的抑制性受体Siglec家族的成员 含酸的葡聚糖配体。Siglec-10/G通过B细胞受体抑制B细胞的激活。在小鼠身上， Siglec-G在抑制B细胞激活的初始事件中的作用已被描述，但尚不清楚 Siglec-G在后期阶段发挥作用，例如在GC中。有趣的是，扩展的GC间隔是 在Siglec-G-/-小鼠中观察到，Siglec-G-/-小鼠患上B细胞淋巴瘤，Siglec-10表达缺失 GC衍生的B细胞淋巴瘤。综上所述，我们假设Siglec-G在 健康状况和Sigelc-10/G表达缺失促进GC来源的B细胞的发展 由于GC反应控制不佳而导致的淋巴瘤。初步结果支持Siglec-G在 抑制混合骨髓嵌合体中GC-B细胞作为B细胞的反应揭示Siglec-G-/-GC B细胞 逐渐胜过WT GC B细胞。更多的初步证据表明了一种独特的表型 (在Siglec-G-/-小鼠体内GC-Tfh细胞中ICOS表达增加)，支持其他 Siglec-G在调节B-T细胞相互作用中的作用的证据。该项目旨在调查一个 Siglec-G基因缺失与GC源性B细胞淋巴瘤发生、发展的因果关系 评估Siglec-G在调节B-T细胞相互作用中的潜在作用。两个独立的方法将是 用来检验Siglec-G-/-的缺失，一种调节失调的GC与GC衍生的B-G-的发展之间的因果关系 细胞性淋巴瘤。在第一种方法中，Tfh细胞将在Siglec-G-/-小鼠身上被消融。在第二种方法中， 在发展成GC-G的独立小鼠模型中，Siglec-G的表达将以转基因方式保持。 衍生的B细胞淋巴瘤和松散的Siglec-G表达。考察Siglec-G的负面作用 作为B-T细胞相互作用的调节因子，Siglec-G的配基特异性将以糖链为参照进行剖析。 天真的GC-Tfh CD4+细胞，以及CD4+T细胞上的葡聚糖配体将被操纵，以检查这将产生什么影响 对B-T细胞的相互作用有影响。该项目的总体目标是测试Siglec-G作为肿瘤的作用 并研究Siglec-G抑制GC的一种可能机制。这 知识将导致对GC来源的B细胞淋巴瘤病因的新见解，并有可能提供 为新的治疗策略提供线索，这对于不治之症的FL尤其需要。

PROJECT SUMMARY/ABSTRACT Approximately 80% of B-cell non-Hodgkin's lymphomas are derived from germinal center (GC) B-cells. Somatic hypermutation within GC B-cells is necessary for antibody affinity maturation, but somatic mutations can also drive epigenetic lesions that enhance survival, maintain the hyperproliferative state of GC B-cells, and promote lymphomagenesis. Given the susceptibility of GC B-cells to malignant transformation, it is not surprising that the natural process of selection within the GC is thought to help protect against the selection of malignant clones. Accordingly, a deeper understanding of factors that restrain the GC are needed. Siglec- 10/G (human/mouse ortholog) are members of the Siglec family of inhibitory receptors that recognize sialic acid-containing glycan ligands. Siglec-10/G dampen B-cell activation through the B-cell receptor. In mice, the role of Siglec-G in inhibiting the initial events of B-cell activation have been described, but it is unknown if Siglec-G plays a role at later stages, such as in the GC. Interestingly, an expanded GC compartment is observed in Siglec-G-/- mice, Siglec-G-/- mice develop B-cell lymphomas, and Siglec-10 expression is lost on GC-derived B-cell lymphomas. Taken together, we hypothesize that Siglec-G restrains the GC reaction under healthy conditions and that loss of Sigelc-10/G expression promotes the development of GC-derived B-cell lymphomas due to a poorly controlled GC reaction. Preliminary results support a role for Siglec-G in restraining GC B-cells, as B-cell responses in mixed bone marrow chimeras reveal that Siglec-G-/- GC B-cells gradually outcompete WT GC B-cells. Additional preliminary evidence demonstrates a unique phenotype (increased ICOS expression) in GC T-follicular helper (GC-Tfh) cells within Siglec-G-/- mice, supporting other lines of evidence for a role for Siglec-G in modulating B-T cell interactions. This project aims to investigate a causal relationship between loss of Siglec-G and the development of GC-derived B-cell lymphomas and assess a potential role for Siglec-G in regulating B-T cell interactions. Two independent approaches will be used to test causality between loss of Siglec-G-/-, a dysregulated GC, and the development of GC-derived B- cell lymphomas. In the first approach, Tfh cells will be ablated in Siglec-G-/- mice. In the second approach, Siglec-G expression will be maintained transgenically in an independent mouse model that develops GC- derived B-cell lymphomas and loose Siglec-G expression. To examine a role for Siglec-G as a negative regulator of B-T cell interactions, the ligand specificity of Siglec-G will be dissected in reference to glycans on naïve GC-Tfh CD4+ cells, and glycan ligands on CD4+ T-cells will be manipulated to examine what impact this has on B-T cell interactions. The overall objective of this project is to test the role of Siglec-G as a tumor suppressor in GC B-cells and examine one potential mechanism by which Siglec-G restrains the GC. This knowledge will lead to new insights into the etiology of GC-derived B-cell lymphomas, and potentially offer clues for new treatment strategies, which are especially needed for the incurable FL.