Colorectal cancer cell-derived exosomal miRNA-372-5p induces immune escape from colorectal cancer via PTEN/AKT/NF-κB/PD-L1 pathway.

Tumor cells can escape immune surveillance by changing their own escape or expressing abnormal genes and proteins, resulting in unlimited proliferation and invasive growth of cells. These changes are related to microRNAs (miRNAs), which reduce the killing effect of immune cells, devastate the immune response, and interfere with apoptosis through the aberrant expression of relevant miRNAs. In the preliminary phase of this study, miRNAs in clinical plasma exosomes of colorectal cancer patients were differentially analyzed by RNA sequencing technology, and miR-372-5p derived from extracellular vesicles (sEVs) was found to be a key signaling molecule mediating the regulation of macrophages by colorectal cancer (CRC). miRNA-372-5p is upregulated in colorectal cancer patient tissues and serum, as well as colorectal cancer cell lines and their exosomes. Subsequently, we found that macrophages could take up sEV secreted by colorectal cancer cells HCT116, affecting the expression of the immune checkpoint PD-L1, resulting in the generation of a tumor-immunosuppressive microenvironment and suppression of T cell activation in CRC. Gene enrichment mapping and database revealed that miR-372-5p regulates PD-L1 expression in colorectal cancer through the homologous phosphatase-tensin (PTEN)-phosphatidylinositol 3-kinase-protein kinase B (AKT)-nuclear factor-κB (NF-κB) pathway. Further studies confirmed that miRNA-372-5p-treated macrophages co-cultured with T cells affected the regulation of PD-L1 expression through the PTEN/AKT/NF-κB signaling pathway, resulting in decreased CD3CD8 T cell activity, decreased cytokine IL-2 and increased IFN-γ. And miRNA-372-5p could down-regulate the expression of PD-L1 in HCT116 through the PTEN/AKT/NF-κB pathway, inhibit tumor cell proliferation and promote apoptosis. Conclusion: Colorectal cancer cell-derived exosome miR-372-5p can be phagocytosed by colorectal cancer and macrophage cells, regulate the expression of PD-L1 in colorectal cancer cells and macrophages by targeting the PTEN/AKT/NF-κB pathway, and induce the immunosuppressive microenvironment of CRC to promote CRC development. This suggests that inhibiting the secretion of HCT116-specific sEV-miR-372-5p or targeting PD-L1 in tumor-associated macrophages could be a novel approach for CRC treatment and possibly a sensitizing approach for CRC anti-PD-L1 therapy.