调控M2型肿瘤相关巨噬细胞（TAMs）向M1型转化是目前肿瘤免疫治疗研究的热点。但TAMs极化的可逆性使得现有药物维持M1型极化的效果不够理想。肿瘤酸性微环境不仅影响TAMs表型，还可抑制T细胞功能引发免疫耐受，与肿瘤进展密切相关。然而如何通过调控肿瘤微环境PH值促进TAMs M1型极化增强免疫应答的研究还很少。本项目前期发现骨肉瘤细胞高表达调节肿瘤微环境酸性的V-ATP酶，其抑制剂埃索美拉唑（ESOM）可调控胞外PH值抑制骨肉瘤生长。我们首次以V-ATP酶作为靶点，联合TAMs M1型诱导剂蕾西莫特（R848），设计合成一种双层多功能纳米粒子，通过外层MMP9响应以及内核M2型TAMs靶向，实现两种药物在肿瘤微环境的按需释放，调节抗肿瘤免疫反应，抑制骨肉瘤发生和转移。同时本项目将系统分析该纳米体系对肿瘤微环境PH值和TAMs极化的调控以及对整体免疫微环境的影响，为骨肉瘤免疫治疗提供新思路。

Regulating the polarization of M2-like phenotype to M1-like phenotype of tumor-associated macrophages (TAMs) is a promising therapeutic strategy for cancer immunotherapy. The effect of existing drugs for keeping M1 phenotype is limited because of the reversibility of TAMs polarization. Tumor acidic microenvironment not only affects TAMs phenotype, but also inhibits T cell function and induces immune tolerance, which is involved in tumor progression. However, few studies have focused on how to promote TAMs M1 polarization and enhance antitumor immune response by modulating acidic pH in the tumor microenvironment. Our recent study showed that osteosarcoma cells highly expressed V-ATPase, which regulates the acidity of tumor microenvironment. Esomeprazole (ESOM), an inhibitor of V-ATPase, can change the extracellular PH value and inhibit the growth of osteosarcoma. For the first time, we designed and synthesized bilayer multifunctional nanoparticles to realize the on-demand release of V-ATPase inhibitor ESOM and M1 TAMs inducer R848, through MMP9 response and M2 TAMs targeting, which promote the anti-tumor immune response and inhibit the occurrence and metastasis of osteosarcoma. Subsequently, we will systemically analyze the regulation of PH value and TAMs polarization in tumor microenvironment and the impact on the overall immune microenvironment by this nanosystem. The implementation of the project will provide a novel combined treatment strategy for cancer immunotherapy.