STAT2 and hepatocellular carcinoma: Forskolin (FSK), a well-known adenylate cyclase agonist for stimulating intracellular cAMP production, significantly attenuated IFN-α/β–induced phosphorylation of STAT1, STAT2, and STAT3 in Huh-7 and HCCLM3 HCC cells (Fig. 1A and Fig. S1A).