To confirm this observation, we examined the levels of phosphorylated cAMP response element-binding protein (p-CREB, an indicator of PKA activation) in 217 HCC tissue samples, and found a significant positive correlation between the IHC scores of H1HR and p-CREB (r = 0.417, P < 0.001) (Fig. 6c). The gene discussed is CREB1; the disease is hepatocellular carcinoma.