Dysregulated mechanoimmunology of epigenetics-driven lymphomas

项目总结 弥漫性大B细胞淋巴瘤(DLBCL)和滤泡性淋巴瘤(FL)起源于生发中心(GC)B细胞 前体B细胞经历多轮增殖的阶段，体细胞编辑其免疫球蛋白 超突变和类切换重组，随后通过与T卵泡的相互作用进行亲和力选择 辅助性(TFH)细胞和滤泡树突状细胞(FDCs)。进入和退出GC反应需要 由转录因子控制的基因表达的广泛变化，这些转录因子招募辅助激活子或辅助激活因子. 驱动表观遗传和转录变化的抑制因子。这些分子程序的失调 干扰正常的B细胞分化，导致FL/DLBCLs。先前的研究表明：(A)EZH2 调节GC B细胞的过度增殖特性和(B)EZH2 Y641残基的功能获得突变 通过减少GC-B细胞对TFH细胞帮助的需求和改变对TFH细胞的依赖来“启动”淋巴瘤的发生 通过增加受体的表达，B细胞与这些基质细胞相互作用，从而导致FDCs的分化。 Ezh2Y641F GC B细胞逃避Tfh诱导的克隆选择和亲和成熟以逃避Tfh介导 消除，导致淋巴肿大。值得注意的是，与EZH2 WT相比，携带EZ2Y641F的GC B细胞显示 BAFFR和CD40的表达分别增加和降低，并逃避CD40L阻断的介导 GC反应障碍。目前尚不清楚TFH HELP的损害是否表现为TFH调节失调 TfH-B免疫突触的机械调控及其细胞间受体-配体的变化 FL/DLBCL的相互作用和信号转导。最重要的假设是，与GC B细胞 GCB DLBCL/FL中EZH2 Y641突变导致关键免疫受体调节失调 GC B细胞与TfH细胞和FDCs的相互作用表现为受体作用力、配体结合和 机械转导。受体机制生物学失调影响下游B细胞信号转导， 表观遗传学，以及对淋巴微环境线索的感知，这些线索负责扑灭 GC B细胞的“恶性”表型，从而驱动B细胞的癌变。我们的转录本 分析表明，参与B-FDC和B-Tfh相互作用的蛋白质水平发生了变化，这应该是 影响细胞功能。我们的目标是了解DLBCL/FL驾驶的动态表观遗传状态 EZH2 Y641突变导致B细胞机制生物学失调，导致肿瘤发生。

PROJECT SUMMARY Diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) arise from germinal center (GC) B cells; a stage at which precursor B cells undergo rounds of proliferation, edit their immunoglobulins by somatic hypermutation and class-switch recombination, followed by affinity selection via interactions with T follicular helper (Tfh) cells and follicular dendritic cells (FDCs). The entry to, and exit from, the GC reaction requires extensive changes in gene expression that are controlled by transcription factors that recruit co-activators or co- repressors that drive epigenetic and transcriptional changes. The dysregulation of these molecular programs perturbs the normal B cell differentiation and contributes to FL/DLBCLs. Prior studies indicate that (a) EZH2 regulates the hyperproliferative nature of GC B cells and (b) gain-of-function mutations of the EZH2 Y641 residue “initiate” lymphomagenesis by attenuating GC B cell requirement for Tfh cell help and shifting the dependency to FDCs through increased expression of receptors through which B-cells interface with these stromal cells. Ezh2Y641F GC B cells evade Tfh-directed clonal selection and affinity maturation to escape Tfh-mediated elimination, leading to lymphomagenesis. Notably, compared to EZH2WT, GC B cells carrying Ezh2Y641F show increased and decreased BAFFR and CD40 expressions, respectively, and escape CD40L blockade-mediated impairment of GC reaction. It is unclear whether the impairment of Tfh help manifests as dysregulation of the mechanical control of Tfh–B immunological synapse (IS) and alteration of their intercellular receptor-ligand interactions and signaling in FL/DLBCLs. The overarching hypothesis is that in contrast to GC B cells with EZH2WT, the EZH2Y641 mutation in GCB DLBCL/FL results in dysregulation of key immunoreceptors mediating the interactions of GC B cells with Tfh cells and FDCs manifesting as altered receptor forces, ligand binding, and mechanotransduction. The dysregulated receptor mechanobiology impacts downstream B cell signaling, epigenetics, and sensing of lymphoid microenvironmental cues responsible for extinguishing the “pseudo- malignant” phenotype of GC B cells, thereby driving the cancerous transformation of B cells. Our transcriptomic analysis suggests changes in the levels of proteins involved in B–FDC and B–Tfh interactions, which should affect cellular function. The goal is to understand how the dynamic epigenetic states of DLBCL/FL-driving EZH2Y641 mutations dysregulate B cell mechanobiology, leading to malignancy.