First, activation of H3R by exogenous histamine suppressed the proliferation of hepatoma McA-RH7777 cells [31], while H3R blockade promoted proliferation due to an unrespected release of cytochrome P450 enzymes within the McA-RH7777 cells, which regulated cell proliferation by controlling the levels of growth regulatory factors [12]. The gene discussed is HRH3; the disease is hepatocellular carcinoma.