The novel triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO) potently enhances apoptosis induced by tumor necrosis factor in human leukemia cells - Stadheim,T.A.; Suh,N.; Ganju,N.; Sporn,M.B.; Eastman,A. (Journal of Biological Chemistry, 2002)