PDE4D and hepatocellular carcinoma: In order to evaluate if pharmacological inhibition of PDE4D may affect HCC oncogenic properties, the effect of different concentrations (1 μM, 5 μM, 10 μM, 50 μM, 100 μM) of a specific PDE4D inhibitor, Gebr-7b, was evaluated in HepG2 and Huh7 cells.