CD28-mediated Regulation of Multiple Myeloma Cell Proliferation and Survival

描述(申请人提供)：多发性骨髓瘤(MM)恶性浆细胞与骨髓基质之间的相互作用对骨髓瘤细胞的增殖和生存至关重要，并在介导化疗耐药中发挥核心作用。由于骨髓微环境的复杂性，确定参与这些相互作用的分子和细胞元素一直很困难。我们的方法是识别骨髓瘤细胞上特有表达的细胞表面受体，然后识别表达这些受体配体的细胞。我们专注于共刺激受体CD28，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，CD28在与抗原提呈细胞(尤其是树突状细胞)上表达的CD80(B7-1)和CD86(B7-2)结合后被激活，并与T细胞受体信号一起显著增强T细胞的增殖、效应功能和生存。与T细胞相比，CD28在血浆/骨髓瘤细胞中的功能知之甚少。然而，临床研究已经证明骨髓瘤疾病进展与骨髓瘤细胞CD28的表达高度相关，而MM CD28的表达是新诊断患者无病生存期缩短的显著预测因素。这些临床观察表明，CD28对骨髓瘤细胞的存活有重要贡献，特别是在化疗选择压力下。我们的初步研究表明，骨髓瘤细胞CD28的直接激活可诱导核因子B的激活，下调MM细胞的增殖，并对血清饥饿和地塞米松诱导的死亡具有保护作用。与表达CD80/CD86的树突状细胞(DC)共培养也可诱导CD28介导的MM存活和增殖效应。此外，我们还发现CD28+/CD86+骨髓瘤细胞株表达吲哚胺2，3双加氧酶(IDO)，这是一种色氨酸分解酶，先前已被证明在DC中由B7交联物诱导，以介导T细胞无能/无应答。我们假设骨髓瘤CD28通过下游的核因子？B激活来传递生存信号，而MM CD28是通过与位于骨髓中的DC(和/或其他CD86+骨髓瘤细胞)的细胞-细胞相互作用来激活的。此外，通过B7(在骨髓瘤细胞或DC上)的“返回”信号诱导IDO，并有助于抑制MM患者特有的细胞介导的免疫。本申请的目的是1)。确定骨髓瘤细胞中CD28激活的分子组成，2)。描述细胞对CD28激活的反应，3)。定义激活骨髓瘤CD28的细胞伙伴，评估是否针对骨髓瘤CD28本身，其信号通路的组件或间质伙伴可以用于治疗。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.