We then knocked down SMAD3 in PDSS2-Del2 overexpressed HCC cells (Fig. 4I), and the results revealed that the expression levels of MST1 were also reduced in SMAD3 knockdown cells (Fig. 4J), which indicates that SMAD3 regulates the expression of MST1. This evidence concerns the gene SMAD3 and hepatocellular carcinoma.