Novel monocyte effector function in CLL immune therapy

描述（由申请人提供）：慢性淋巴细胞白血病（CLL）是成人白血病中最常见的一种，目前可用的治疗方法无法治愈。一种有前景的治疗形式是抗体疗法，其中CLL细胞被抗CD 20抗体如利妥昔单抗和奥法木单抗靶向。这导致了生存率的显着改善，特别是与其他疗法相结合，但完全缓解仍然相对罕见。单核细胞和巨噬细胞是抗体治疗的关键介质，这取决于Fc？受体（Fc？R）活动。我们已经发现，激活这些Fc？R导致sFlt-1的产生，sFlt-1是VEGF受体的可溶性抑制形式。sFlt-1可抑制VEGF信号传导，其已显示在CLL细胞存活中起主要作用。这些结果使我们假设，Fc？R-介导的sFlt-1产生可以抑制CLL细胞中的抗凋亡信号，并且这是抗体介导的抗肿瘤作用的重要部分。因此，在抗体治疗的背景下加强单核细胞/巨噬细胞sFlt-1的产生可能是增强其有效性的有力手段。为了检验这一假设的预测，我们提出：目的1：分析sFlt-1的生产和功能，以响应抗CD 20。在这里，我们将a）鉴定在结合抗CD 20抗体后主要负责sFlt-1产生的细胞，检查sFlt-1对CLL细胞存活的影响，并研究肿瘤细胞中VEGF介导的存活被抑制的机制。我们还将B）检查单核细胞的sFlt-1产生是否使CLL细胞对临床前和临床上用于治疗CLL的试剂的直接凋亡更敏感。目的2：分析sFlt-1的产生和在体内抗体治疗中的功能。我们将使用已建立的CLL鼠模型来a）使用鼠CD 20抗体测试sFlt-1是否在抗体介导的B细胞耗竭期间产生，B）鉴定相关Fc？c）测试中和sFlt-1是否减少了负责sFlt-1产生的携带R的效应细胞， 抗CD 20抗体在鼠CLL模型中的功效，和d）接受奥法木单抗单一疗法的CLL患者中的sFlt-1水平是否与应答和无进展存活相关。目的3：阐明Fc？R聚类。在这里，我们将确定a）哪个激活Fc？R负责sFlt-1的诱导，这种诱导是否受Fc负调控？RIIb和SHIP，B）是否为Fc？R诱导的sFlt-1产生是直接或间接的作用，以及c）参与sFlt-1诱导的信号传导途径。总结：本研究完成后，我们将充分探索抗CD 20介导的单核细胞和巨噬细胞杀伤肿瘤细胞的全新机制。这些机制研究将提供信息，以进一步增强抗CD 20抗体（如奥法木单抗）在CLL中的疗效，但可能用于使用类似抗体治疗的各种其他肿瘤。

DESCRIPTION (provided by applicant): Chronic Lymphocytic Leukemia (CLL) is the most common form of adult leukemia and is incurable with currently available therapies. One promising form of treatment has been antibody therapy, where CLL cells are targeted by anti-CD20 antibodies such as rituximab and ofatumumab. This has led to significant improvements in survival, especially in combination with other therapies, but complete remissions are still relatively rare. Monocytes and macrophages are critical mediators of antibody therapy, and this depends upon Fc? receptor (Fc?R) activity. We have found that activation of these Fc?R leads to production of sFlt-1, a soluble, inhibitory form of the VEGF receptor. sFlt-1 can inhibit VEGF signaling, which has been shown to play a major role in CLL cell survival. These results led us to hypothesize that Fc?R-mediated sFlt-1 production can dampen anti- apoptotic signals in CLL cells, and that this accounts for a significant portion of antibody-mediated antitumor effects. Hence, strengthening monocyte / macrophage sFlt-1 production within the context of antibody therapy may be a powerful means of enhancing its effectiveness. To test the predictions of this hypothesis we propose: Aim 1: Analysis of sFlt-1 production and function in response to anti-CD20. Here, we will a) identify the cells primarily responsible for sFlt-1 production upon binding anti-CD20 antibodies, examine the effect of sFlt-1 on CLL cell survival, and study the mechanism(s) by which VEGF-mediated survival in tumor cells is inhibited. We will also b) examine whether sFlt-1 production by monocytes makes CLL cells more susceptible to direct apoptosis in response to agents in use preclinically and clinically for the treatment of CLL. Aim 2: Analysis of sFlt-1 production and function in antibody treatment in vivo. We will use established murine models of CLL to a) test whether sFlt-1 is produced during antibody-mediated B cell depletion using a murine CD20 antibody, b) identify relevant Fc?R-bearing effector cell(s) responsible for sFlt-1 production, c) test whether neutralizing sFlt-1 reduces the efficacy of anti-CD20 antibody in a murine CLL model, and d) Whether sFlt-1 levels in CLL patients receiving monotherapy with ofatumumab correlate with response and progression free survival. Aim 3: Elucidation of mechanism of sFlt-1 induction by Fc?R clustering. Here, we will determine a) which activating Fc?R is responsible for sFlt-1 induction and whether this induction is negatively regulated by Fc?RIIb and SHIP, b) whether Fc?R-induced sFlt-1 production is a direct or indirect effect, and c) the signaling pathway(s) involved in sFlt-1 induction. Summary: At completion of this study we will have fully explored an entire new mechanism of anti-CD20 mediated killing of tumor cells by monocytes and macrophages. These mechanistic studies will provide information to further enhance the efficacy of both anti-CD20 antibodies such as ofatumumab in CLL but potentially a wide variety of other tumors where similar antibody based treatments are utilized.