Role of hedgehog signaling in tumor-associated macrophage polarization

摘要 Hhedgehog(HH)途径是细胞分化、组织极性和细胞增殖的主要调节因子。 该通路在皮肤、脑、胃肠道、前列腺、肺、胰腺和 乳腺癌。过度表达HH配体的肿瘤也激活了邻近区域的这一信号通路 内皮细胞、成纤维细胞和免疫细胞随后都会产生生长和生存因子， 趋化因子和血管生成分子，创造一个有利于肿瘤形成的微环境。巨噬细胞 在大多数实体瘤中占肿瘤间质肿块的10%-50%，表现出很大的表型 局部肿瘤微环境(TME)影响下的异质性和功能多样性 刺激物。巨噬细胞不断地渗入TME，在那里它们被极化成为促癌细胞 肿瘤相关巨噬细胞(TAM)，表现为抗炎的M2巨噬细胞表型。这些 TAMs促进肿瘤生长、血管生成、基质重塑、转移和免疫逃避。然而，它 在很大程度上仍不清楚是什么促进了M2型免疫抑制TAMs的极化 TAMs在肿瘤微环境中抑制抗肿瘤免疫反应的机制。 利用小鼠肝癌模型，我们证明了髓系细胞中有缺陷的Hedgehog信号 导致TAM的M2极化受损，导致肿瘤生长显著减少，并增加了 CD8+细胞毒性T细胞在体内的渗透，提示HH信号在M2极化中起关键作用 巨噬细胞与抗肿瘤免疫的调节。我们进一步表明，Hepa1-6肝癌细胞 Sonic Hedgehog(Shh)配体和Shh在体外可直接驱动巨噬细胞M2极化。 综上所述，我们假设肿瘤来源的HH配体直接作用于肿瘤相关的巨噬细胞 通过调节T细胞功能，诱导M2极化，促进肿瘤生长。为了检验这一假设，我们 建议追求以下具体目标：1)研究肿瘤来源的HH配体是否直接调节 TAMs的M2极化；2)揭示HH诱导M2的分子信号机制 TAMS的极化；以及3)阐明TAMS的HH依赖的M2极化是否促进肿瘤生长 通过调节T细胞功能。该项目的长期目标是确定HH信号在 从机制上理解其对肿瘤中巨噬细胞极化的影响与肿瘤的发生 微环境及其在免疫细胞失调、癌症发生和发展中的作用 这可能导致针对旁分泌HH信号的新的治疗策略的开发。 肿瘤微环境。

Abstract The hedgehog (Hh) pathway is a major regulator of cell differentiation, tissue polarity and cell proliferation. Hyper-activation of this pathway has been found in skin, brain, gastrointestinal, prostate, lung, pancreatic and breast cancers. Tumors overexpressing Hh ligands also activate this signaling pathway in neighboring endothelial cells, fibroblasts and immune cells all of which subsequently produce growth and survival factors, chemokines and angiogenic molecules that create a pro-tumorigenic microenvironment. Macrophages representing 10-50% of the tumor stromal mass in most solid tumors, demonstrate great phenotypic heterogeneity and diverse functional capabilities under the influence of local tumor microenvironment (TME) stimuli. Macrophages continuously infiltrate into the TME, where they are polarized to become pro-tumorigenic tumor-associated macrophages (TAMs) that display an anti-inflammatory M2 macrophage phenotype. These TAMs facilitate tumor growth, angiogenesis, matrix remodeling, metastasis and immune evasion. However, it remains largely undefined what promotes the polarization of M2-type, immunosuppressive TAMs and the mechanisms through which TAMs suppress anti-tumor immune responses within the tumor microenvironment. Using a murine model of hepatoma, we demonstrated that defective hedgehog (Hh) signaling in myeloid cells resulted in impaired M2 polarization of TAMs, leading to a significant reduction of tumor growth and increase in CD8+ cytotoxic T cells infiltration in vivo, suggesting a critical role for Hh signaling in the polarization of M2 macrophages and the regulation of anti-tumor immunity. We further showed that Hepa1-6 hepatoma cells secret sonic hedgehog (Shh) ligands and Shh could directly drive M2 polarization of macrophages in vitro. Taken together, we hypothesized that tumor-derived Hh ligands directly act on tumor-associated macrophages to induce M2 polarization and promote tumor growth by regulating T cell function. To test this hypothesis, we propose to pursue the following specific aims: 1) Investigate whether tumor-derived Hh ligands directly regulate M2 polarization of TAMs; 2) Uncover the molecular signaling mechanisms underlying Hh-induced M2 polarization of TAMs; and 3) Elucidate whether Hh-dependent M2 polarization of TAMs promotes tumor growth by regulating T-cell functions. The long-term objective of this project is to define the role of Hh signaling in tumorigenesis by providing a mechanistic understanding of its effects on macrophage polarization in the tumor microenvironment and its contributions to immune cell dysregulations, cancer development and progression, which may lead to the development of novel therapeutic strategies targeting paracrine Hh signaling in the tumor microenvironment.