Regulation of Tumor Associated Macrophages by TGF-beta

描述(申请人提供)：肿瘤相关巨噬细胞()是几乎所有类型恶性肿瘤的肿瘤微环境(TME)中观察到的免疫细胞浸润的主要成分之一。新的数据表明，巨噬细胞是肿瘤细胞增殖、血管生成、转移和生存的关键调节细胞。TME中存在许多因子，包括转化生长因子β，使肿瘤常规地绕过宿主介导的免疫反应，并重定向的活动，从而使肿瘤成功进展。然而，这种过程背后的分子机制(S)尚不清楚。在癌变的早期阶段，转化生长因子β作为肿瘤抑制因子，而在晚期则作为肿瘤促进剂。与肿瘤促进功能一致，已知转化生长因子β对免疫系统有更广泛的影响，部分是通过转化生长因子β信号中间产物与细胞因子和抗原受体成分(包括Toll样受体)之间的相互作用。Toll样受体(TLRs)家族是免疫细胞先天免疫反应的重要介体，这些受体的激活触发了包括IFN在内的多种抗肿瘤反应分子的产生。在TME中，究竟是什么触发了巨噬细胞中的TLR信号尚不清楚。然而，TME富含宿主衍生的分子，包括热休克蛋白、来自坏死肿瘤细胞的双链DNA和透明质酸，透明质酸可以潜在地激活巨噬细胞TLR信号来触发抗肿瘤反应。IRAK-M是一种不活跃的丝氨酸/苏氨酸激酶，是TLR信号的有效负调节因子，主要表达于巨噬细胞。我们的研究表明，当共培养时，人肺癌细胞诱导人单核/巨噬细胞表达IRAK-M。转化生长因子β以时间和剂量依赖的方式诱导人单核/巨噬细胞表达IRAK-M。在IRAK-M-/-小鼠体内的研究表明，皮下移植的同基因Lewis-肺癌细胞对肿瘤生长有明显的抑制作用。对从野生型小鼠提纯的TAMs的分析表明，与来自相同小鼠的腹膜巨噬细胞相比，IRAK-M的表达增强。来自IRAK-M-/-小鼠的TAM显示促炎症和抗肿瘤细胞因子的表达增强。假设：基于上述观察，我们推测肿瘤细胞产生的转化生长因子-β导致TAMS表达IRAK-M，从而发挥拮抗TLR信号的作用。这使得肿瘤能够避开潜在的TLR介导的巨噬细胞的抗肿瘤反应，并有助于获得独特的表型。相反，阻断IRAK-M的表达可能会促进TAMs的抗肿瘤反应，抑制肿瘤的生长和转移。具体目的：1)建立IRAK-M-/-小鼠Lewis肺癌同种异位和原位移植模型，探讨IRAK-M在肺癌生长和转移中的作用。2)确定IRAK-M在TAMs免疫抑制表型中的作用。3)通过骨髓移植确定对抑制IRAK-M-/-小鼠肿瘤生长至关重要的主要效应细胞是否为髓系细胞；4)确定转化生长因子β诱导巨噬细胞表达IRAK-M的机制。

DESCRIPTION (provided by applicant): Tumor associated macrophages (TAM) constitute one of the major components of the immune cell infiltrate observed in the tumor microenvironment (TME) of virtually all types of malignancies. Emerging data implicates macrophages as key regulators of tumor cell proliferation, angiogenesis metastasis and survival. Many factors present within the TME including TGF-¿, allow tumors to routinely circumvent host mediated immune responses and redirect TAM activities for successful tumor progression. However, the molecular mechanism(s) underlying such a process are not known. In early stages of carcinogenesis TGF-¿ acts as tumor suppressor and in late stages as tumor promoter. Consistent with the tumor promoting function, TGF-¿ is known to have a broader influence on the immune system partly through cross-talk between TGF-¿ signaling intermediates and the components of both cytokine and antigen receptors including Toll-like receptors. The family of Toll-Like Receptors (TLRs) is an important mediator of the innate immune responses by immune cells and activation of these receptors trigger the production of several molecules involved in antitumoral responses including IFNs. In TME, what exactly triggers TLR signaling in macrophages is not known. However, The TME is rich in host derived molecules, including heat shock proteins, double stranded DNA from necrotic tumor cells and Hyaluronic acid that can potentially activate macrophage TLR signaling to trigger anti-tumoral responses. IRAK-M is an inactive ser/thr kinase, potent negative regulator of TLR signaling and predominantly expressed in macrophages. Our studies show that when co-cultured, human lung cancer cells induce IRAK-M expression in human monocytes/macrophages. TGF-¿ induces IRAK-M expression in human monocytes/macrophages in time and dose dependent manner. In-vivo studies in IRAK-M-/- mice showed a significant inhibition in tumor growth of subcutaneously implanted syngeneic Lewis-lung carcinoma cells. Analysis of TAMs purified from wild type mice demonstrated enhanced IRAK-M expression compared to peritoneal macrophages from same mice. TAMs from IRAK-M-/- mice demonstrated enhanced expression of proinflammatory and anti-tumor cytokines. Hypothesis: Based on above observations, we propose that tumor cell production of TGF-¿ results in IRAK-M expression by TAMs which functions to antagonize TLR signaling. This allows tumors to circumvent potential TLR mediated anti-tumor responses of macrophages and contribute to acquisition of distinct TAM phenotype. Conversely, disruption of IRAK-M expression may promote anti-tumor responses in TAMs and inhibit tumor growth and metastasis. Specific aims: 1) to determine the role of IRAK-M in lung tumor growth and metastasis using syngeneic heterotopic and orthotopic models of lewis lung carcinoma in IRAK-M-/- mice. 2) to determine the contribution of IRAK-M to the immunosuppressive phenotype of TAMs. 3) to determine whether the primary effector cell critical for tumor growth inhibition in IRAK-M-/- mice is of myeloid origin, by bone marrow transplantation 4) determine the mechanism of TGF-¿-induced IRAK-M expression in macrophages.