Cardiac glycosides are natural compounds which have long been used to treat cardiac congestion and arrhythmia by selective inhibition of Na+/K+ ATPase.Recently cardiac glycosides have been shown to exert anticancer activity in various cancer cells.In the present study,we found that Proscillaridin A,a cardiac glycoside effectively inhibits growth and induces apoptosis in A549 non-small cell lung adenocarcinoma cells in a dose-dependent manner at nanomolar concentrations.