Targeting ER stress response in B-cell chronic lymphocytic leukemia

项目摘要/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，占所有成人的30% 白血病。虽然引发事件尚不清楚，但接触细菌多糖等因素， 脂蛋白和DNA被认为通过与B细胞受体(BCR)结合来驱动CLL的增殖。 这些因子也是Toll样受体(TLRs)的配体，Toll样受体是一类对先天性疾病至关重要的受体 免疫和在B细胞分化和激活中发挥多种作用。然而，TLR配体到底是如何 参与CLL的机制尚不清楚，因为一些研究观察到TLR处理CLL细胞后的细胞凋亡 配体和其他研究观察到了增殖。了解哪些配体有哪些作用尤其重要 目前至关重要的是，由于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。作为临床应用的一个例子，伊布鲁替尼被用来抑制bcr信号通路，而bcr信号通路促进了肿瘤细胞的增殖。 但在莫菲特癌症中心接受伊布鲁替尼治疗的CLL患者中，大约60%的人退出了 由于毒性而导致的治疗。此外，CLL经历了里希特向快速增长的弥漫大B的转变 细胞淋巴瘤中接受伊布鲁替尼治疗的患者越来越多。因此，阻止B细胞增殖 在CLL方面仍然是一个挑战。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细胞生存需要 激活内质网应激反应。我们还发现ER应激反应的IRE-1/XBP-1通路 被TLR配体激活，在体外促进CLL细胞的增殖。这些结果让我们提出了假设 在CLL细胞中，特定的TLR配体通过TLR和BCR信号激活IRE-1/XBP-1通路，从而 促进慢性淋巴细胞性白血病恶性进展。我们已经建立了一种新的小鼠模型，在该模型中XBP-1基因是 在Eµ-TCL1(CLL)小鼠的B细胞中特异性敲除，并显示BCR信号在 XBP-1缺失的Eµ-TCL1B细胞。此外，我们还开发了一种特定而有效的IRE抑制剂- 1/XBP-1途径，B-I09，在体内诱导CLL凋亡，对小鼠无明显毒性。 B-i09处理也减少了E-TCL1B细胞中的BCR信号。使用这些新工具，我们将 准确地确定哪些TLR配体通过激活IRE而促进体内CLL的恶性进展 1/XBP-1通路和BCR信号通路，以及靶向IRE-1/XBP-1通路是否能阻断这两种信号转导途径。 TLR配体的叉状效应。基于我们的新数据，我们还建议测试CLL细胞是否缺乏XBP- 1S可能激活调节的IRE-1依赖的衰变(RIDD)来对抗细胞凋亡。总结了这些目标 在以下具体目标中。目的1：建立TLR配体诱导内质网应激反应的激活机制 支持CLL在体内的恶性进展，以及人类CLL细胞的增殖和存活。目标2： 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：探讨RIDD在XBP-1KO/Eµ-TCL1小鼠慢性淋巴细胞性白血病发生发展中的作用。

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.