Tumor-mediated impairment of IL-12 gene expression

描述(申请人提供)：肿瘤通过诱导细胞因子表达的改变而在宿主中引起免疫抑制。关键的调节细胞因子IL-12起着先天免疫和获得性免疫之间的桥梁作用。它由巨噬细胞和树突状细胞产生，作用于NK和T细胞，诱导其产生干扰素-γ，驱动T细胞产生Th1反应。IL-12也被认为具有很强的抗肿瘤作用。因此，通过阻断IL-12的表达，肿瘤可能会保证自己的生存。肿瘤诱导的IL-12基因表达下调作为肿瘤生存策略的可能性几乎没有被探索过。我研究的长期目标是阐明巨噬细胞在乳腺肿瘤发展中的作用。我们已经证明，小鼠乳腺肿瘤D1-DMBA-3直接产生因子，并诱导宿主B细胞和巨噬细胞产生抑制荷瘤动物腹膜巨噬细胞产生IL-12的因子。我推测，这些肿瘤相关因子，特别是肿瘤产生的磷脂磷脂酰丝氨酸(PS)和肿瘤诱导的促炎细胞因子IL-6，至少部分通过在转录水平下调IL-12基因在巨噬细胞中的表达而发挥其免疫抑制作用，从而逃避宿主的免疫防御，促进肿瘤生长。本研究旨在揭示D1-DMBA-3肿瘤抑制荷瘤动物巨噬细胞IL-12基因表达的分子机制。我计划通过追求以下特定目标来验证我的假设：1)阐明D1-DMBA-3肿瘤的存在，特别是肿瘤衍生因子磷脂酰丝氨酸(PS)和肿瘤诱导细胞因子IL-6的存在，分别下调荷瘤动物巨噬细胞和经这些肿瘤相关因子处理的正常小鼠巨噬细胞产生IL-12的机制；2)研究调控IL-12诱导转录因子NFkB和C/EBP的表达对正常和荷瘤动物巨噬细胞IL-12表达的影响，以及PS和IL-6对正常小鼠巨噬细胞IL-12表达的影响；3)体内调节PS和IL-6对IL-12产生和乳腺肿瘤进展的影响。这些研究是朝着控制肿瘤宿主中IL-12水平的目标迈出的第一步，从而导致适当的免疫激活。

DESCRIPTION (provided by applicant): Tumors invoke immunosuppression in the host by inducing an altered profile of cytokine expression. The crucial regulatory cytokine IL-12 operates as a bridge between innate and adaptive immunities. It is produced by macrophages and dendritic cells, and acts upon NK and T cells to induce their production of IFN-gamma, driving T cells to develop Th1 responses. IL-12 has also been recognized to exhibit strong anti-tumor properties. Therefore, by blocking IL-12 expression, the tumor might guarantee its own survival. The possibility of a tumor-induced downregulation of IL-12 gene expression as a tumor survival strategy has been scarcely explored. The long-term goal of my research is to clarify the role of macrophages in mammary tumor development. We have shown that the mouse mammary tumor D1-DMBA-3 directly produces factors, and induces B cells and macrophages from the host to produce factors that inhibit the production of IL-12 by peritoneal elicited macrophages from tumor-bearing animals. I hypothesize that these tumor-associated factors, in particular the tumor-produced phospholipids phosphatidylserine (PS) and the tumor-induced pro-inflammatory cytokine IL-6, exert their immunosuppressive effects at least in part by downregulating IL-12 gene expression at the transcriptional level in macrophages, resulting in evasion of the host's immune defenses and enhanced tumor growth. The objective of the present application is to reveal the molecular mechanisms of the D1-DMBA-3 tumor-mediated inhibition of IL-12 gene expression in macrophages from tumor-bearing animals. I plan to test my hypothesis by pursuing the following specific aims: 1) To elucidate the mechanisms by which the presence of the D1-DMBA-3 tumor, and specifically the tumor-derived factor phosphatidylserine (PS) and the tumor-induced cytokine IL-6, downregulate the production of IL-12 in macrophages from tumor-bearing animals as well as in macrophages from normal mice pretreated with these tumor-associated factors, respectively; 2) To investigate the consequences of manipulating the expression of the critical IL-12-inducing transcription factors NFkB and C/EBP on IL-12 expression in macrophages from normal and tumor-bearing animals, as well as in macrophages from normal mice pretreated with PS and IL-6; 3) To determine the effects of modulating PS and IL-6 in vivo on IL-12 production and mammary tumor progression. These studies constitute a first step towards the goal of manipulating the levels of IL-12 in tumor hosts, leading to appropriate immune activation.