CXCR4 and hepatocellular carcinoma: This is the first study to show that UC-MSCs-derived exosomes exerted anti-proliferative apoptotic, and anti-angiogenic effects against HCC due to the suppression of SIRT-1 protein expression, the upregulation of TNF-α and caspase-3 expressions as well as the downregulation of VEGF, SDF-1 and CXCR-4 expressions.