Liriodenine inhibits human lung adenocarcinoma A549 cell proliferation and blocks the cell cycle progression at the G2/M phase, accompanied by a reduction of G1 cyclin D1 and accumulation of G2 cyclin B1, and the enzymatic activity of the cyclin B1/cyclin-dependent kinase 1 complex was reduced in liriodenine-treated cells. The gene discussed is CDK1; the disease is lung adenocarcinoma.