PTEN and cancer: Moreover, researchers found that exosomal miRNA-21 and miR-155 from HCC cells could directly target PTEN, leading to the activation of PDK1/AKT signaling in hepatic stellate cells (HSCs), which promoted cancer progression by secreting angiogenic cytokines, including VEGF, MMP2, MMP9, bFGF and TGF-β (38).