Plenty of immune cells infiltrate into the tumor microenvironment (TME) during tumor progression, in which myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells with immunosuppressive activity. Tumor cells and stromal cells facilitate the activation and expansion of MDSCs in TME via intercellular communication, and expanded MDSCs suppress anti-tumor immune responses through direct and indirect mechanisms. Currently, exosomes, which are a kind of extracellular vesicles (EVs) that can convey functional components, are demonstrated to participate in the local and distal intercellular communication between cells. Numerous studies have supposed that tumor-derived exosomes (TEXs), whose assembly and release can be modulated by TME, are capable of modulating the cell biology of MDSCs, including facilitating their activation, promoting the expansion, and enhancing the immunosuppressive function. Therefore, in this review, we mainly focus on the role of TEXs in the cell-cell communication between tumor cells and MDSCs, and discuss their clinical applications.

中文翻译：

---

肿瘤源性外泌体、骨髓源性抑制细胞和肿瘤微环境。

在肿瘤进展过程中，大量免疫细胞浸润到肿瘤微环境（TME）中，其中骨髓源性抑制细胞（MDSC）代表具有免疫抑制活性的异质未成熟骨髓细胞群体。肿瘤细胞和基质细胞通过细胞间通讯促进 TME 中 MDSC 的激活和扩增，而扩增的 MDSC 通过直接和间接机制抑制抗肿瘤免疫反应。目前，外泌体是一种可以传递功能成分的细胞外囊泡（EV），被证明参与细胞间的局部和远端细胞间通讯。大量研究认为，肿瘤源性外泌体（TEX）的组装和释放可以通过 TME 调节，能够调节 MDSC 的细胞生物学，包括促进其激活、促进扩增和增强免疫抑制功能。因此，在这篇综述中，我们主要关注TEXs在肿瘤细胞和MDSCs之间的细胞间通讯中的作用，并讨论其临床应用。