The crosstalk between lung adenocarcinoma cells and M2 macrophages promotes cancer cell development via the SFRS1/miR-708-5p/PD-L1 axis

This study aimed to elucidate the underlying mechanisms regarding microRNA-708-5p (miR-708-5p) in lung adenocarcinoma (LUAD). Here, the co-culture system of LUAD cells and macrophages, as well as a xenograft mouse model, were established. High levels of miR-708-5p were observed in LUAD. Exosomal miR-708-5p facilitated M2-like phenotype polarization, whereas miR-708-5p inhibition blocked the polarization. Exosomal miR-708-5p was identified as a pivotal signaling molecule for macrophages to mediate tumor cell proliferation, invasion, migration and IFN-γ production in T cells. In addition, miR708-5p was observed to induce PD-L1 expression, and PD-L1 silencing inhibited macrophage-induced tumor cell growth behavior and regulated CD8 T cell activity. In xenograft models, miR-708-5p inhibition and PD-L1 silencing attenuated macrophage-induced tumor growth, induced IFN-γ secretion and CD8 expression, and modulated the PTEN/AKT/mTOR pathway. In LUAD patients, there was an upregulation of both miR-708-5p and PD-L1 expression, accompanied by the activation of PTEN/AKT/mTOR. In conclusion, this study demonstrated the induction of M2 macrophage polarization and PD-L1 expression by exosomal miR-708-5p. We observed that exosomal miR-708-5p mediated the PTEN/AKT/mTOR pathway, diminished CD8 T cell activity and accelerated LUAD progression. The inhibition of specific exosomal miRNA secretion and anti-PD-L1 in the LUAD microenvironment may represent a promising avenue for LUAD immunotherapy.