生物响应型微环境重塑制剂增效Meso-CAR-T治疗晚期三阴性乳腺癌的研究

高纤维间质增生及强免疫抑制的肿瘤微环境是限制CAR-T细胞治疗晚期三阴性乳腺癌（TNBC）的关键因素，而TGF-β是其形成的重要调控因子。本项目首次提出“微坏境重塑-免疫增效”的联合治疗策略，即利用微环境过度表达的基质金属蛋白酶2（MMP2），设计MMP2生物响应型微环境重塑制剂，将TGF-β受体抑制剂高效靶向递送至微环境并响应释药，从而有效下调间质增生并逆转免疫抑制；在重塑微环境基础上序贯联用以间皮素（Meso）为靶点的CAR-T，可显著提高晚期TNBC治疗效果。本项目将系统考察微环境重塑制剂理化性质，通过二维细胞、3D瘤球和原位荷瘤动物模型系统评价其对微环境重塑能力，并建立该制剂和Meso-CAR-T序贯治疗方案，考察抗肿瘤活性，并在微环境表征基础上阐明免疫增效机制，为建立安全、高效的晚期TNBC免疫治疗方案提供实验基础和理论依据，对提高实体瘤免疫治疗水平具有重要理论意义和应用价值。

High interstitial proliferation and strong immunosuppression are the key factors to resist CAR-T cell immunotherapy in advanced triple negative breast cancer (TNBC). Transforming growth factor-β (TGF-β), an important cytokine in tumors, is thought to play a crucial role in the formation of enriched stroma microenvironment with immunosuppression. In this study, a novel sequential combination therapy strategy was put forward to increase the treatment of advanced TNBC, i.e., “remodeling the tumor microenvironment by a matrix metalloproteinase 2 (MMP2) responsive nanopreparation, followed by CAR-T cell therapy with higher sensitivity”. MMP2, a member of MMPs family, is overexpressed in TNBC environment and able to cleave special peptide segments. Therefore, a MMP2-responsive nanopreparation will be constructed using a MMP2-senseive peptide linker. The obtained naopareparation can efficiently deliver TGF-β receptor inhibitor, galunisertib (Gal), to tumor and fast disassembled in the presence of MMP2 in the microenvironment, resulting in rapid release of drug. The released Gal can efficiently inhibit TGF-β mediated signal pathway and down-regulate the interstitial fibrosis in the stroma and reverse immunosuppression. On the base of the remodeled tumor microenvironment induced by the MMP2-responsive nanopreparation, CAR-T cell therapy is sequentially performed and an increased immunotherapeutic effect will be achieved. In this study, MMP2-responsive nanopreparation will be prepared and the physicochemical properties are studied in detail. Moreover, the tumor targeting abilities and the capacity of remodeling the microenvironment are studied using two-dimensional cell model, three-dimensional cell ball model and orthotopic tumor models. The sequential combination of MMP2-responsive nanopreparation and CAR-T cell therapy will be performed on orthotopic tumor models, and the anti-tumor efficiency and safety are observed. Moreover, the mechanism of increased sensitivity of advanced TNBC to CAR-T cell therapy is explored by charactering the tumor microenvironment. This sequential combination therapy strategy will provide an efficient and promising mean for the advanced TNBC treatment, which also has important significance for the effective immunotherapy of solid tumors.