Besides, HRH3 in HCC inactivates the cAMP/PKA/CREB pathway by down-regulating the expression of cyclin-dependent kinase inhibitor P21 (CDKN1A), promoting the G1-S phase transition, and ultimately promotes the malignant growth of HCC (Zhang et al., 2020). The gene discussed is HRH3; the disease is hepatocellular carcinoma.