TLR7 and colorectal cancer: MicroRNA-21-5p (miR-21) is highly expressed in colorectal cancer-derived sEVs, polarizes hepatic macrophages to an interleukin 6 (IL-6) producing phenotype via toll-like receptor 7 (TLR7), induces the formation of an inflammatory microenvironment, and promotes CRC liver-specific metastasis [38].