SMAD1 and hepatocellular carcinoma: Interestingly, overexpressing PPM1H still inhibited Transwell migration and invasion of Hep-G2 and Huh-7 cells after blocking phosphorylation of SMAD1 with LDN193189 (Figure S5F), pointing to the fact that there might be other substrates of PPM1H that regulate hepatoma cell growth and invasion.