Reactive oxygen species reprogram macrophages to suppress antitumor immune response through the exosomal miR-155-5p/PD-L1 pathway

Abstract

Background Cancer cells have an imbalance in oxidation-reduction (redox) homeostasis. Understanding the precise mechanisms and the impact of the altered redox microenvironment on the immunologic reaction to tumors is limited. Methods We isolated exosomes from ovarian cancer cells through ultracentrifuge and characterized by Western-blots and Nanoparticle Tracking Analysis. 2D, 3D-coculture tumor model, and 3D live cell imaging were used to study the interactions between tumor cells, macrophages and CD3 T cells in vitro. The role of exosomal miR-155-5p in tumor growth was evaluated in xenograft nude mice models and immune-competent mice models. Flow cytometry and flow sorting were used to determine the expression levels of miR-155-5p and PD-L1 in ascites and splenic macrophages, and the percentages of CD3 T cells subpopulations. Results The elevation of reactive oxygen species (ROS) greatly downregulated exosomal miR-155-5p expression in tumor cells. Neutralization of ROS with N-acetyl-L-cysteine (NAC) increased the levels of miR-155-5p in tumor exosomes that were taken up by macrophages, leading to reduction of macrophage migration and tumor spheroid infiltration. We further found that programmed death ligand 1 (PD-L1) is a functional target of miR-155-5p. Co-culture of macrophages pre-treated with NAC-derived tumor exosomes or exosomal miR-155-5p with T-lymphocytes leading to an increased percentage of CD8+ T-lymphocyte and a decreased CD3+ T cell apoptosis through PD-L1 downregulation. Tumor growth in nude mice was delayed by treatment with NAC-derived tumor exosomes. Delivery of tumor exo-miR-155-5p in immune-intact mice suppressed ovarian cancer progression and macrophage infiltration, and activated CD8+ T cell function. It is of note that exo-miR-155-5p inhibited tumor growth more potently than the PD-L1 antibody, suggesting that in addition to PD-L1, other pathways may also be targeted by this approach. Conclusions Our findings demonstrate a novel mechanism, ROS-induced down-regulation of miR-155-5p, by which tumors modulate the microenvironment that favors tumor growth. Understanding of the negative impact of ROS on the tumor immune response will improve current therapeutic strategies. Targeting miR-155-5p can be an alternative approach to prevent formation of an immunosuppressive TME through downregulation of PD-L1 and other immunosuppressive factors. Graphical Abstract

A four-microRNA panel in serum may serve as potential biomarker for renal cell carcinoma diagnosis

“…In addition, in ovarian cancer cells, Xiang Li et al. indicated that exo-miR-155-5p release could be promoted by ROS inhibition, resulting in the elevation of miR-155-5p, which means that miR-155-5p downregulated expression could create the tumor growth favoring microenvironment ( 32 ). Therefore, RCC patients with higher miR-155-5p expression level tended to have worse prognosis.…”

Establishment and validation of a redox-related long non-coding RNAs prognostic signature in head and neck squamous cell carcinoma

“…Roberta Vené revealed the vital function of redox remodeling in B-cell activation and differentiation 46 . Xiang Li found that ROS decreased the amount of tumor exo-miR-155 that was taken up by macrophages, resulting in enhanced macrophage infiltration and T cell inactivation characterized by upregulation of PD-L1 in ovarian cancer 47 . According to these results, we speculated that the rrlncRNAs signature might have a promising impact on the tumor immune milieu in HNSCC.…”

Immune Modulation Using Extracellular Vesicles Encapsulated with MicroRNAs as Novel Drug Delivery Systems

“…When naïve CD3+ T cells were stimulated with CD3 and CD28 and cultured in an IL-2 medium, they were found to be rich in CD8+ T cells and contained exosomes in the culture supernatant [ 89 ]. miR-155 is essential for memory maintenance and the effector function of CD8+ T cells [ 90 ]. miR-155 is also known to release a variety of exosomes with different protein masses by activating CD4+ T cells.…”