CD28-mediated Regulation of Multiple Myeloma Cell Proliferation and Survival

描述（由申请方提供）：多发性骨髓瘤（MM）的恶性浆细胞与骨髓基质之间的相互作用对于骨髓瘤细胞增殖和存活至关重要，并在介导化疗耐药性方面发挥核心作用。由于骨髓微环境的复杂性，很难确定这些相互作用中涉及的分子和细胞成分。我们的方法是鉴定骨髓瘤细胞上特征性表达的细胞表面受体，然后鉴定表达这些受体配体的细胞。我们重点关注共刺激受体CD 28，它主要在T细胞上表达，但也在正常浆细胞和骨髓瘤细胞上表达。对于T细胞，CD 28在与抗原呈递细胞（特别是树突状细胞（DC））上表达的CD 80（B7-1）和CD 86（B7-2）结合后被激活，并且与T细胞受体信号传导结合显著增强T细胞增殖、效应子功能和存活。与T细胞相反，关于CD 28在血浆/骨髓瘤细胞中的功能知之甚少。然而，临床研究已证明骨髓瘤疾病进展与骨髓瘤细胞CD 28表达之间存在高度显著相关性，MM CD 28表达是新诊断患者无病生存期缩短的重要预测因素。这些临床观察结果暗示了CD 28对骨髓瘤细胞存活的重要贡献，特别是在化疗治疗选择压力下。我们的初步研究表明，直接激活骨髓瘤细胞CD 28诱导NF？B下调MM细胞增殖并保护免受血清饥饿和地塞米松诱导的死亡。与表达CD 80/CD 86的树突状细胞（DC）共培养也增强了CD 28介导的对MM存活和增殖的影响。此外，我们发现CD 28 +/CD 86+骨髓瘤细胞系表达吲哚胺2，3双加氧酶（IDO），这是一种以前已显示由DC中的B7交联诱导以介导T细胞无反应性/无反应性的聚糖分解代谢酶。我们假设骨髓瘤CD 28通过下游NF？B，并且MM CD 28通过与位于骨髓中的DC（和/或其它CD 86+骨髓瘤细胞）的细胞-细胞相互作用而被激活。此外，通过B7（在骨髓瘤细胞或DC上）的“返回”信号传导诱导IDO，并有助于抑制MM患者中特有的细胞介导的免疫。本申请的目的是1）。定义骨髓瘤细胞中CD 28活化的分子组分，2）。表征对CD 28活化的细胞应答，3）。定义激活骨髓瘤CD 28的细胞伴侣，4）评估是否可以在治疗上利用针对骨髓瘤CD 28本身、其信号传导途径的组分或基质伴侣。这些研究可能为多发性骨髓瘤的治疗提供新的策略。

DESCRIPTION (provided by applicant): The interactions between the malignant plasma cells of multiple myeloma (MM) and the bone marrow stroma are essential for myeloma cell proliferation and survival, and play a central role in mediating resistance to chemotherapy. Defining the molecular and cellular elements involved in these interactions has been difficult due to the complexity of the bone marrow microenvironment. Our approach has been to identify cell surface receptors that are characteristically expressed on myeloma cells, and then identify cells that express the ligands for these receptors. We have focused on the costimulatory receptor CD28, which is expressed predominantly on T cells but also on normal plasma cells and myeloma cells. For T cells, CD28 is activated upon binding to CD80 (B7-1) and CD86 (B7-2) expressed on antigen presenting cells (especially dendritic cells (DC)), and in conjunction with T cell receptor signaling significantly augments T cell proliferation, effector function and survival. In contrast to T cells, little is known about the function of CD28 in plasma/myeloma cells. However, clinical studies have demonstrated a highly significant correlation between myeloma disease progression and myeloma cell CD28 expression, and MM CD28 expression as a significant predictor of shortened disease-free survival in newly diagnosed patients. These clinical observations implicate an important contribution of CD28 to myeloma cell survival, particularly under chemotherapy treatment selection pressure. Our preliminary studies demonstrate that direct activation of myeloma cell CD28 induces activation of NF?B, downregulates MM cell proliferation and protects against serum starvation and dexamethasone-induced death. Coculture with dendritic cells (DC) expressing CD80/CD86 also elicits CD28-mediated effects on MM survival and proliferation. Furthermore, we have found that CD28+/CD86+ myeloma cell lines express indoleamine 2, 3 dioxygenase (IDO), a tryptophan-catabolizing enzyme that has been previously shown to be induced by B7 crosslinking in DC to mediate T cell anergy/unresponsiveness. We hypothesize that myeloma CD28 transduces survival signals through downstream activation of NF?B, and that MM CD28 is activated by a cell-cell interaction with DC (and/or other CD86+ myeloma cells) located in the bone marrow. Furthermore, "back" signaling through B7 (on the myeloma cell or DC) induces IDO and contributes to the suppression of cell-mediated immunity characteristically seen in MM patients. The Aims of this application are 1). Define the molecular components of CD28 activation in myeloma cells, 2). Characterize the cellular responses to CD28 activation, 3). Define the cellular partners that activate myeloma CD28, 4).Assess if targeting myeloma CD28 itself, components of its signaling pathway or stromal partners can be exploited therapeutically. These studies may provide novel strategies for the treatment of multiple myeloma.