The tumor development and metastasis are closely related to the structure and function of the tumor microenvironment (TME). Recently, TME modulation strategies have attracted much attention in cancer immunotherapy. Despite the preliminary success of immunotherapeutic agents, their therapeutic effects have been restricted by the limited retention time of drugs in TME. Compared with traditional delivery systems, nanoparticles with unique physical properties and elaborate design can efficiently penetrate TME and specifically deliver to the major components in TME. In this review, we briefly introduce the substitutes of TME including dendritic cells, macrophages, fibroblasts, tumor vasculature, tumor-draining lymph nodes and hypoxic state, then review various nanoparticles targeting these components and their applications in tumor therapy. In addition, nanoparticles could be combined with other therapies, including chemotherapy, radiotherapy, and photodynamic therapy, however, the nanoplatform delivery system may not be effective in all types of tumors due to the heterogeneity of different tumors and individuals. The changes of TME at various stages during tumor development are required to be further elucidated so that more individualized nanoplatforms could be designed.

中文翻译：

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纳米粒子在癌症免疫治疗中的应用：靶向肿瘤微环境

肿瘤的发展和转移与肿瘤微环境（TME）的结构和功能密切相关。最近，TME调节策略已在癌症免疫治疗中引起了广泛关注。尽管免疫治疗剂取得了初步的成功，但是它们的治疗效果已受到TME中药物保留时间有限的限制。与传统的输送系统相比，具有独特物理性能和精心设计的纳米颗粒可以有效地渗透TME，并专门输送到TME中的主要成分。在这篇综述中，我们简要介绍了TME的替代物，包括树突状细胞，巨噬细胞，成纤维细胞，肿瘤脉管系统，引流肿瘤的淋巴结和低氧状态，然后综述了针对这些成分的各种纳米颗粒及其在肿瘤治疗中的应用。此外，纳米粒子可以与其他疗法相结合，包括化学疗法，放射疗法和光动力疗法，但是，由于不同肿瘤和个体的异质性，纳米平台递送系统可能不适用于所有类型的肿瘤。需要进一步阐明肿瘤发展过程中各个阶段TME的变化，以便可以设计更多个性化的纳米平台。