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

描述（由申请人提供）：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年美国将有约16,060名患者被诊断为CLL，约有4,580名患者将死于CLL。在佛罗里达州坦帕市的莫菲特癌症中心，我们每年会看到大约200名新的慢性淋巴细胞白血病患者。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，CLL仍然是无法治愈的。我们建议确定CLL细胞生存所依赖的关键机制，并针对其中一种机制来阻止或减缓CLL的侵袭性进展。强大的B细胞受体（BCR）信号转导被认为是CLL细胞快速增殖的原因，导致疾病的侵袭性进展。虽然蛋白质抗原被认为可以触发CLL细胞的生长和增殖，但抗原可以驱动CLL恶性进展的概念尚未在动物模型中得到概括。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激活BCR并驱动CLL的恶性进展。当B细胞受到同源抗原刺激时，内质网应激反应激活，支持B细胞生长和增殖。我们假设蛋白质抗原参与BCR可以激活CLL细胞内质网应激反应，从而促进体内CLL的恶性进展。我们已经证明内质网应激反应的肌醇要求酶-1 (IRE-1)/X-box结合蛋白-1 （XBP-1）途径对CLL细胞的存活至关重要。一种新型小分子化学抑制剂阻断XBP-1的表达可诱导培养的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小鼠模型中基因删除了XBP-1基因。利用这种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途径在体内减缓抗原诱导的CLL侵袭性进展的机制。在基因缺失或化学敲低XBP-1的细胞中，我们观察到IRE-1的表达水平升高，并获得独特的磷酸化模式。众所周知，IRE-1具有促进细胞存活和诱导细胞凋亡的作用，但目前尚不清楚IRE-1如何完成这两个看似相反的任务。我们假设不同的磷酸化模式可能允许IRE-1与不同的相互作用伙伴关联，以执行其促进CLL存活或诱导细胞凋亡的功能。我们的目标可以概括为两个方面：1)靶向IRE-1/XBP-1途径在体内抗原诱导的CLL侵袭性进展中；2)鉴定和研究与IRE-1相互作用的蛋白，以进一步了解靶向IRE-1/XBP-1通路如何导致CLL进展停滞。我们的目标是建立内质网应激反应作为治疗CLL的有用靶点。

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.