Abstract：
Tumor-associated macrophages (TAMs) are among the most abundant infiltrating leukocytes in the tumor microenvironment (TME). Reprogramming TAMs from protumor M2 to antitumor M1 phenotype is a promising strategy for remodeling the TME and promoting antitumor immunity; however, the development of an efficient strategy remains challenging. Here, a genetically modified bacterial biomimetic vesicle (BBV) with IFN-γ exposed on the surface in a nanoassembling membrane pore structure was constructed. The engineered IFN-γ BBV featured a nanoscale structure of protein and lipid vesicle, the existence of rich pattern-associated molecular patterns (PAMPs), and the costimulation of introduced IFN-γ molecules. In vitro, IFN-γ BBV reprogrammed M2 macrophages to M1, possibly through NF-κB and JAK-STAT signaling pathways, releasing nitric oxide (NO) and inflammatory cytokines IL-1β, IL-6, and TNF-α and increasing the expression of IL-12 and iNOS. In tumor-bearing mice, IFN-γ BBV demonstrated a targeted enrichment in tumors and successfully reprogrammed TAMs into the M1 phenotype; notably, the response of antigen-specific cytotoxic T lymphocyte (CTL) in TME was promoted while the immunosuppressive myeloid-derived suppressor cell (MDSC) was suppressed. The tumor growth was found to be significantly inhibited in both a TC-1 tumor and a CT26 tumor. It was indicated that the antitumor effects of IFN-γ BBV were macrophage-dependent. Further, the modulation of TME by IFN-γ BBV produced synergistic effects against tumor growth and metastasis with an immune checkpoint inhibitor in an orthotopic 4T1 breast cancer model which was insensitive to anti-PD-1 mAb alone. In conclusion, IFN-γ-modified BBV demonstrated a strong capability of efficiently targeting tumor and tuning a cold tumor hot through reprogramming TAMs, providing a potent approach for tumor immunotherapy.
摘要：
肿瘤相关巨噬细胞（TAM）是肿瘤微环境（TME）中最丰富的浸润白细胞之一。将TAM从原瘤M2重编程为抗肿瘤M1表型是重塑TME和促进抗肿瘤免疫的有希望的策略；然而，制定有效的战略仍然具有挑战性。这里,构建了一种基因修饰的细菌仿生囊泡（BBV），其表面暴露于纳米组装膜孔结构中的IFN-γ。工程化的IFN-γBBV具有蛋白质和脂质囊泡的纳米级结构，存在丰富的模式相关分子模式(PAMPs)，和引入的IFN-γ分子的共刺激。体外，IFN-γBBV将M2巨噬细胞重编程为M1，可能通过NF-κB和JAK-STAT信号通路，释放一氧化氮（NO）和炎症细胞因子IL-1β，IL-6和TNF-α以及增加IL-12和iNOS的表达。在荷瘤小鼠中，IFN-γBBV在肿瘤中表现出靶向富集，并成功地将TAM重编程为M1表型；TME中抗原特异性细胞毒性T淋巴细胞（CTL）的反应得到促进，而免疫抑制性髓源性抑制细胞（MDSC）受到抑制。发现肿瘤生长在TC-1肿瘤和CT26肿瘤中均被显著抑制。结果表明，IFN-γBBV的抗肿瘤作用是巨噬细胞依赖性的。Further,在对单独抗PD-1mAb不敏感的原位4T1乳腺癌模型中,IFN-γBBV对TME的调节与免疫检查点抑制剂对肿瘤生长和转移产生协同作用.总之,IFN-γ修饰的BBV显示出通过重编程TAM有效靶向肿瘤和调节冷肿瘤热的强大能力，为肿瘤免疫治疗提供了有效的方法。
