MiR-21-5p in hepatocellular carcinoma cell (HCC)-derived exosomes promotes the polarization of TAM towards M2 phenotype by regulating the SP1/XBP1 signaling pathway, which leads to immunosuppressive state in the TME, enabling tumor cells to escape the attack of the immune system, and thus promoting the development and deterioration of HCC [131]. The gene discussed is SP1; the disease is hepatocellular carcinoma.