Targeting ER stress response in B-cell chronic lymphocytic leukemia

项目总结/摘要 慢性淋巴细胞白血病（CLL）是一种无法治愈的B细胞恶性肿瘤，占所有成人白血病的30 白血病虽然起始事件尚不清楚，但暴露于细菌多糖， 脂蛋白和DNA已经被提出通过与B细胞受体（BCR）结合来驱动CLL中的增殖。 这些因子还充当Toll样受体（TLR）的配体，Toll样受体是一类对先天性免疫缺陷至关重要的受体。 在B细胞分化和活化中发挥多种作用。然而，TLR配体 参与CLL的机制尚不清楚，因为一些研究观察到用TLR处理CLL细胞后细胞凋亡 配体和其它研究观察到增殖。了解哪些配体具有哪些作用， 目前，TLR配体被提议作为免疫调节剂来指导我们的免疫系统， 战斗CLL。作为一个恰当的临床案例，伊鲁替尼用于抑制BCR信号传导，该信号传导驱动细胞增殖。 CLL;但在莫菲特癌症中心接受伊鲁替尼治疗的CLL患者中，约60%退出了研究。 治疗由于毒性。此外，CLL经历了Richter转变为快速生长的弥漫性大B 在越来越多的接受伊鲁替尼治疗的患者中，因此，阻止B细胞增殖 CLL仍然是一个挑战。我们小组利用我们对内质网（ER）的深入了解， 信号从不同的角度考虑这个问题，发现CLL细胞要存活， ER应激反应的激活。我们还发现，ER应激反应的IRE-1/XBP-1途径， 被TLR配体激活，以促进体外CLL细胞的增殖。这些结果让我们假设 在CLL细胞中，特异性TLR配体通过TLR和BCR信号传导激活IRE-1/XBP-1通路， 促进CLL的恶性进展。我们已经建立了一种新的小鼠模型，其中XBP-1基因是 在Eµ-TCL 1（CLL）小鼠的B细胞中特异性敲除，并显示BCR信号转导在小鼠中下调。 XBP-1缺陷型Eµ-TCL 1 B细胞。此外，我们还开发了一种特异性和有效的IRE抑制剂， 1/XBP-1途径，B-I 09，其在体内诱导CLL的凋亡并且在小鼠中不表现出明显的毒性。 用B-I 09处理也减少Eµ-TCL 1 B细胞中的BCR信号传导。使用这些新工具，我们将 确切地确定哪些TLR配体通过激活IRE-1在体内促进CLL的恶性进展。 1/XBP-1通路和BCR信号传导，以及靶向IRE-1/XBP-1通路是否可以阻碍这两个信号传导。 TLR配体的交叉效应。基于我们的新数据，我们还建议测试缺乏XBP的CLL细胞是否- 1 s可激活调节性IRE-1依赖性衰变（RIDD）以对抗细胞凋亡。这些目标被概括为 以下具体目标。目的1：建立TLR配体诱导的ER应激反应的激活 支持CLL在体内的恶性进展以及人CLL细胞的增殖和存活。目标二： 研究靶向XBP-1是否通过抑制BCR来减缓TLR配体诱导的CLL进展 发信号。目的3：研究RIDD如何促进XBP-1 KO/Eµ-TCL 1小鼠中CLL的进展。

Project Summary/Abstract Chronic lymphocytic leukemia (CLL) is an incurable B cell malignancy that represents 30% of all adult leukemia. Although the initiating events are unclear, exposure to factors such as bacterial polysaccharides, lipoproteins, and DNA has been proposed to drive proliferation in CLL, via binding to the B cell receptor (BCR). These factors also serve as ligands for Toll-like receptors (TLRs), a class of receptors critical for innate immunity and that play multiple roles in B cell differentiation and activation. However, exactly how TLR ligands are involved in CLL is unclear, as some studies observe apoptosis after treatment of CLL cells with TLR ligands and other studies observe proliferation. Understanding which ligands have which effects is particularly crucial at present, as TLR ligands are proposed as immunomodulatory agents to coach our immune system to combat CLL. As a clinical case in point, ibrutinib is used to inhibit the BCR signaling that drives proliferation of CLL; but approximately 60% of CLL patients treated with ibrutinib at the Moffitt Cancer Center dropped out of the therapy due to toxicity. In addition, CLL undergoes Richter's transformation into fast-growing diffuse large B cell lymphoma in increasing numbers of patients receiving ibrutinib therapy. Hence, halting B cell proliferation in CLL remains a challenge. Our group used our in-depth understanding of the endoplasmic reticulum (ER) signaling to consider this problem from a different angle, finding that for CLL cells to survive they require activation of the ER stress response. We also found that the IRE-1/XBP-1 pathway of the ER stress response is activated by TLR ligands, to promote proliferation of CLL cells in vitro. These results led us to hypothesize that in CLL cells, specific TLR ligands activate the IRE-1/XBP-1 pathway through TLR and BCR signaling, to promote malignant progression of CLL. We have generated a novel mouse model in which the XBP-1 gene is knocked out specifically in B cells in Eµ-TCL1 (CLL) mice, and showed that BCR signaling is downregulated in XBP-1-deficient Eµ-TCL1 B cells. In addition, we have developed a specific and potent inhibitor of the IRE- 1/XBP-1 pathway, B-I09, which induces apoptosis of CLL in vivo and does not exhibit overt toxicity in mice. Treatment with B-I09 also reduced BCR signaling in Eµ-TCL1 B cells. Using these novel tools, we will determine exactly which TLR ligands promote malignant progression of CLL in vivo via activation of the IRE- 1/XBP-1 pathway and BCR signaling, and whether targeting the IRE-1/XBP-1 pathway can thwart the two- pronged effect of TLR ligands. Based on our new data, we also propose to test whether CLL cells lacking XBP- 1s may activate regulated IRE-1-dependent decay (RIDD) to counter apoptosis. These goals are summarized in the following specific aims. Aim 1: Establish that TLR ligand-induced activation of the ER stress response supports malignant progression of CLL in vivo, and proliferation and survival of human CLL cells. Aim 2: Investigate whether targeting XBP-1 decelerates TLR ligand-induced progression of CLL by suppressing BCR signaling. Aim 3: Investigate how RIDD contributes to the progression of CLL in XBP-1KO/Eµ-TCL1 mice.