MMP9 and hepatocellular carcinoma: At the same time, Zhou et al. showed that exosomal miR-21 directly targeted PTEN, activating PDK1/AKT signaling in HSCs and promoting HCC progression by secreting a complex repertoire of angiogenic cytokines, including VEGF, MMP2, MMP9, bFGF, and TGF-β [159].