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）是成人白血病最常见的形式，目前的治疗方法无法治愈。一种有希望的治疗形式是抗体治疗，其中CLL细胞被抗cd20抗体如利妥昔单抗和ofatumumab靶向。这导致了生存率的显著提高，特别是与其他疗法联合使用时，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。我们发现这些Fc？R导致sFlt-1的产生，sFlt-1是一种可溶性的VEGF受体抑制形式。sFlt-1可以抑制VEGF信号传导，在CLL细胞存活中发挥重要作用。这些结果使我们假设Fc？r介导的sFlt-1的产生可以抑制CLL细胞的抗凋亡信号，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。为了验证这一假设的预测，我们提出：目的1：分析sFlt-1在抗cd20反应中的产生和功能。在这里，我们将a)确定结合抗cd20抗体产生sFlt-1的主要细胞，检查sFlt-1对CLL细胞存活的影响，并研究vegf介导的肿瘤细胞存活被抑制的机制。我们还将b)研究单核细胞产生的sFlt-1是否会使CLL细胞在临床前和临床治疗CLL的药物作用下更容易发生直接凋亡。目的2：体内抗体治疗中sFlt-1的产生和功能分析。我们将使用已建立的小鼠CLL模型a)测试sFlt-1是否在使用小鼠CD20抗体介导的B细胞消耗过程中产生，B)鉴定相关的Fc？负责产生sFlt-1的含r效应池，c)测试中和sFlt-1是否会降低

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.