Gambogic acid is a plant-derived natural product that acts as a caspase activator and apoptosis inducer, which causes an irreversible arrest in the G2/M phase of the cell cycle. It causes a decrease of Bcl-2 gene and an increase in Bax gene expression, which may result in apoptosis. Gambogic also acts as an inhibitor of A1 and Bcl-2 family proteins, including Bcl-xl, Bcl-2, Bcl-w, Bcl-B, Bfl-1, and Mcl-1.