TARGETING ANTIGEN-INDUCED ER STRESS RESPONSE IN B-CELL CHRONIC LYMPHOCYTIC LEUKEM

描述(申请人提供)：慢性淋巴细胞白血病(CLL)是成人最常见的白血病。根据美国国家癌症研究所的数据，2012年美国将有大约16,060名患者被诊断为慢性淋巴细胞性白血病，大约4,580名患者将死于慢性淋巴细胞性白血病。在佛罗里达州坦帕市的莫菲特癌症中心，我们每年看到大约200名新的CLL患者。虽然CLL最初对化疗有反应，但复发的CLL发生率很高，并获得化疗耐药。因此，慢性淋巴细胞性白血病仍然是无法治愈的。我们建议确定CLL细胞赖以生存的关键机制，并针对其中一种机制来阻止或减缓CLL的侵袭性进展。强健的B细胞受体(BCR)信号转导被认为与CLL细胞的快速增殖有关，从而导致疾病的侵袭性进展。虽然蛋白质抗原已被认为可以触发CLL细胞的生长和增殖，但这种抗原可以推动CLL恶性进展的概念还没有在动物模型中重复。因此，我们创建了一种新的抗原特异性CLL小鼠模型，在该模型中，我们使用所需的抗原来激活BCR并推动CLL的恶性进展。当B细胞被其同源抗原刺激时，内质网(ER)应激反应被激活，以支持B细胞的生长和增殖。我们假设BCR与蛋白质抗原的结合可以激活CLL细胞的ER应激反应，从而促进CLL在体内的恶性进展。我们已经证明，内质网应激反应中的肌醇需要酶-1(IRE-1)/X-盒结合蛋白-1(XBP-1)通路对CLL细胞的生存至关重要。一种新的小分子化学抑制剂阻断XBP-1的表达可诱导体外培养的CLL细胞凋亡。为了更好地了解IRE-1/XBP-1通路在CLL进展中的作用，我们从我们的新型抗原特异性CLL小鼠模型中从基因上删除了XBP-1基因。利用这一创新的小鼠模型和我们的新型小分子抑制剂，我们将研究阻断IRE-1/XBP-1途径可以减缓体内抗原诱导的CLL侵袭性进展的机制。在XBP-1基因缺失或化学敲除的细胞中，我们观察到IRE-1表达水平升高，并获得独特的磷酸化模式。IRE-1在促进细胞存活和诱导细胞凋亡方面的作用已为人所知，但目前仍不清楚IRE-1如何完成这两个看似相反的任务。我们推测，不同的磷酸化模式可能允许IRE-1与不同的相互作用伙伴结合，在促进CLL存活或诱导凋亡方面发挥其功能。我们在这个建议中的目标概括为两个目标：1)靶向在抗原诱导的体内CLL侵袭进展中的IRE-1/XBP-1通路；2)识别和研究与IRE-1相互作用的蛋白质，以进一步了解靶向IRE-1/XBP-1通路如何导致CLL进展停滞。我们的目标是将内质网应激反应作为治疗慢性淋巴细胞性白血病的有效靶点。

DESCRIPTION (provided by applicant): Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. According to the National Cancer Institute, approximately 16,060 patients will be diagnosed with CLL and approximately 4,580 patients will die of CLL in the US in 2012. At the Moffitt Cancer Center in Tampa, Florida, we see about 200 new CLL patients each year. Although CLL initially responds to chemotherapy, the relapsed CLL occurs at a high rate and acquires chemoresistance. Therefore, CLL is still incurable. We propose to identify the critical mechanisms that CLL cells rely on for their survival and target one such mechanism to block or decelerate aggressive progression of CLL. Robust B cell receptor (BCR) signal transduction was suggested to be responsible for the rapid proliferation of CLL cells, leading to aggressive progression of disease. Although protein antigen has been suggested to trigger the growth and proliferation of CLL cells, this concept that antigen can drive malignant progression of CLL has not been recapitulated in an animal model. Therefore, we have created a novel antigen-specific CLL mouse model, in which we use a desired antigen to activate the BCR and drive malignant progression of CLL. When a B cell is stimulated by its cognate antigen, activation of the endoplasmic reticulum (ER) stress response occurs to support B cell growth and proliferation. We hypothesize that engagement of the BCR by protein antigen can activate the ER stress response in CLL cells to promote malignant progression of CLL in vivo. We have shown that the inositol-requiring enzyme-1 (IRE-1)/X-box- binding protein-1 (XBP-1) pathway of the ER stress response is critical for the survival of CLL cells. Blocking the expression of XBP-1 by a novel small-molecule chemical inhibitor induces apoptosis in CLL cells in culture. To better understand the role of the IRE-1/XBP-1 pathway in the progression of CLL, we have genetically deleted the XBP-1 gene from our novel antigen-specific CLL mouse model. Using this innovative mouse model together with our novel small-molecule inhibitors, we will investigate the mechanisms by which blocking the IRE-1/XBP-1 pathway can decelerate antigen-induced aggressive progression of CLL in vivo. In cells with genetic deletion or chemical knockdown of XBP-1, we observed that IRE-1 is expressed at an elevated level and acquires a unique phosphorylation pattern. IRE-1 has been known for its roles in promoting cell survival and inducing apoptosis, but it is still unclear how IRE-1 accomplishes these two seemingly opposing tasks. We hypothesize that differential phosphorylation patterns may allow IRE-1 to associate with different interacting partners to carry out its functions in promoting survival or inducing apoptosis in CLL. Our goals in this proposal are summarized by two aims: 1) Target the IRE-1/XBP-1 pathway in antigen-induced aggressive progression of CLL in vivo; 2) Identify and investigate proteins that interact with IRE-1 to further understand how targeting the IRE-1/XBP-1 pathway can lead to stalled progression of CLL. Our goal is to establish the ER stress response as a useful target for the treatment of CLL.