In addition, some studies have demonstrated that the degradation of PDE4A can activate the cAMP/PKA/CREB signaling pathway and lead to the upregulation of transforming growth factor(TGF)-β expression, which may induce epithelial-mesenchymal transition and promote the invasion of hepatocellular carcinoma [55]. The gene discussed is CREB1; the disease is hepatocellular carcinoma.