Extracellular Vesicles miR-28-5p Derived from Colorectal Cancer Cells Stimulate Liver Metastasis through the Activation of M2-Subtype TAM Polarization

Abstract

Objectives: Previous studies have demonstrated that tumor-associated macrophages (TAMs) have a significant impact on the initiation and progression of cancer. Interactions between cells within the tumor microenvironment (TME) are mediated by extracellular vesicles (EVs), which transport various functional molecules such as mRNA, miRNA, proteins, and lipids. However, the specific molecular mechanisms that regulate the interaction between EVs derived from tumors and TAMs in the context of liver metastasis of colorectal cancer liver metastasis (CRLM) remain unclear. Our goal is to show that EVs originating from colorectal cancer cells stimulate the M2 polarization of macrophages. Methods: We examined the relationship between macrophages and the potential impact of EVs derived from colorectal cancer cells in this study. Transmission electron microscopy (TEM) and differential ultracentrifugation were utilized to validate the presence of EVs. Several methods, including dual-luciferase reporter assay, quantitative polymerase chain reaction (qPCR), and western blotting, were employed to elucidate the mechanism by which EVs miR-28-5p regulate the interaction between colorectal cancer (CRC) cells and macrophages. Results: Initially, we observed an increased expression of miR-28-5p in CRC patients, specifically in CRLM patients. Analysis of data from The Cancer Genome Atlas (TCGA) and The Encyclopedia of RNA Interactomes (ENCORI) databases revealed its association with poor prognosis in CRC patients. Subsequently, we verified that miR-28-5p, derived from EVs of colorectal cancer cells, induced the polarization of macrophages by inhibiting phosphatase and tensin homolog deleted on chromosome ten (PTEN) and activating phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT). Additionally, we identified that M2 macrophages polarized by CRC cell-derived EV-miR-28-5p promoted epithelial-mesenchymal transition (EMT) and facilitated CRLM. Conclusions: In summary, our findings show that miR-28-5p in EVs derived from CRC can promote CRLM by regulating TAM polarization. Furthermore, we have uncovered another mechanism, mediated by tumor-derived EVs, that influences CRLM.