In addition to tumor sources, exosomes secreted by macrophages express specific CD11b/CD18 proteins to promote MMP-9 expression, thereby promoting HCC migration (69).Furthermore, exosomes alter the stromal environment surrounding the tumor by regulating the synthesis and degradation of matrix components and matrix adhesion factors, thereby creating a suitable tumor microenvironment and enhancing the metastatic ability of hepatocellular carcinoma (70). Here, MMP9 is linked to hepatocellular carcinoma.