Vesículas extracelulares de macrófagos M1 e nanopartículas agonistas de TLR3 regulam negativamente a imunossupressão e a metástase no câncer de mama triplo negativo

Abstract

Triple-negative breast cancer (TNBC) is an aggressive form of the disease, with limited therapeutic options and a poor prognosis for patients. Tumor immune escape–induced metastasis has been implicated as one of the main factors contributing to this aggressiveness. Therefore, new therapies must be developed, particularly those involving nanoparticles and extracellular vesicles, which have emerged as promising platforms for delivering immune system components. In this context, extracellular vesicles derived from M1 macrophages (M1EVs) were isolated and subsequently combined with PLGA nanoparticles loaded with the TLR3 agonist poly(I:C) (NPIC), as a promising therapeutic strategy. The aim was to investigate their antitumor activity by negatively regulating immune escape within the tumor microenvironment (TME), in a murine orthotopic tumor growth model. Tumors were evaluated by qRT-PCR and immunohistochemistry, while cellular uptake and macrophage polarization of murine RAW 264.7 cells were analyzed in vitro by immunofluorescence and flow cytometry, respectively. Additionally, mouse survival, lymph node involvement, and metastatic spread were thoroughly assessed. In the animal model, the combined therapy significantly inhibited tumor progression, mainly through immunomodulation of the TME, resulting in reduced primary tumor volume (p < 0.0001) and metastasis, as well as an extension of survival by 11 days. Notably, both innate and adaptive immune responses were enhanced, as evidenced by increased CD8 expression (p < 0.0001), reduced PD-L1 levels in the TME, and increased CD11c expression in lymph nodes (p < 0.0001). Similarly, the combined therapy suppressed tumor progression by reducing AKT1 expression (p < 0.001) and increasing E-cadherin expression (p < 0.01). Altogether, these findings indicate that the combination of M1-EVs and NPIC functions as a "vaccine-like immunomodulatory strategy," promoting TME reprogramming and inhibiting metastasis in the murine model of TNBC.