治疗药物透过性差、T细胞浸润有限以及三阴性乳腺癌（TNBC）强烈免疫抑制性肿瘤微环境是制约药物和免疫疗法（包括程序性细胞死亡配体-1抗体 [anti-PD-L1]）传递的显著障碍。由癌相关成纤维细胞（CAFs）和肿瘤细胞产生的重要细胞因子转化生长因子（TGF）β在病理性血管、致密肿瘤基质和强烈免疫抑制性肿瘤微环境中起到了贡献。在此，我们精心构建了一种纳米医学平台（HA-LSL/siTGF-β），采用双重靶向策略，以适应性水解酸和还原剂谷胱甘肽（GSH）的刺激释放，以有效传递TGF-β小干扰RNA（siTGF-β）。我们发现，该系统能够提高抗PD-L1治疗的疗效。在体外和体内，siTGF-β纳米系统能够高效静默哺乳动物成纤维细胞系NIH 3T3和4T1细胞中与TGF-β相关的信号通路。本系统首先通过CD44介导的摄取作用，随后通过内/溶酶体介导的HA酶快速逃逸和胞浆中由高GSH浓度介导的siRNA释放实现。通过同时抑制基质和肿瘤细胞中的TGF-β，HA-LSL/siTGF-β显著减少了基质沉积，促进了纳米医学深度重塑肿瘤微环境，改善了氧化、T细胞浸润和随后的抗PD-L1深度渗透。双重抑制TGF-β已被证明能够促进血管正常化、抑制上皮-间质转化（EMT）并进一步修饰免疫抑制性肿瘤微环境，这得到了树突状细胞和细胞毒性T细胞比例整体增加的支持。此外，TME中调节性T细胞和髓源性抑制性细胞等免疫抑制细胞比例也有所降低。基于这种纳米系统对肿瘤微环境的全面重塑，随后的抗PD-L1治疗引发了强大的抗肿瘤免疫。具体来说，该系统能够抑制初发肿瘤和远处肿瘤的生长，同时防止肿瘤转移到肺部。因此，双靶向siTGF-β纳米系统与抗PD-L1的组合可能成为增强基质丰富型TNBC抗肿瘤免疫治疗的新方法。版权所有 © 2023 Elsevier Ltd.

The poor permeability of therapeutic drugs, limited T-cell infiltration, and strong immunosuppressive tumor microenvironment of triple-negative breast cancer (TNBC) acts as a prominent barrier to the delivery of drugs and immunotherapy including programmed cell death ligand-1 antibody (anti-PD-L1). Transforming growth factor (TGF)-β, an important cytokine produced by cancer-associated fibroblasts (CAFs) and tumor cells contributes to the pathological vasculature, dense tumor stroma and strong immunosuppressive tumor microenvironment (TME). Herein, a nanomedicine platform (HA-LSL/siTGF-β) employing dual-targeting, alongside hyaluronidase (HAase) and glutathione (GSH) triggered release was elaborately constructed to efficiently deliver TGF-β small interference RNA (siTGF-β). It was determined that this system was able to improve the efficacy of anti-PD-L1. The siTGF-β nanosystem efficiently silenced TGF-β-related signaling pathways in both activated NIH 3T3 cells and 4T1 cells in vitro and in vivo. This occurred firstly, through CD44-mediated uptake, followed by rapid escape mediated by HAase in endo/lysosomes and release of siRNA mediated by high GSH concentrations in the cytoplasm. By simultaneous silencing of TGF-β in stromal and tumor cells, HA-LSL/siTGF-β dramatically reduced stroma deposition, promoted the penetration of nanomedicines for deep remodeling of the TME, improved oxygenation, T cells infiltration and subsequent anti-PD-L1 deep penetration. The double suppression of TGF-β has been demonstrated to promote blood vessel normalization, inhibit an epithelial-to-mesenchymal transition (EMT), and further modify the immunosuppressive TME, which was supported by an overall increase in the proportion of dendritic cells and cytotoxic T cells. Further, a reduction in the proportion of immunosuppression cells such as regulatory T cells and myeloid-derived suppressor cells was also observed in the TME. Based on the comprehensive remodeling of the tumor microenvironment by this nanosystem, subsequent anti-PD-L1 therapy elicited robust antitumor immunity. Specifically, this system was able to suppress the growth of both primary and distant tumor while preventing tumor metastasis to the lung. Therefore, the combination of the dual-targeted siTGF-β nanosystem, alongside anti-PD-L1 may serve as a novel method to enhance antitumor immunotherapy against stroma-rich TNBC.Copyright © 2023. Published by Elsevier Ltd.