XIAP and cancer: The decreased expression of death receptors TRAIL-R1 and TRAIL-R2 and antiapoptotic proteins (Bid, Bax, Bak, Smac/DIABLO) or increased expression of antiapoptotic proteins (FLIP, Bcl-2, Bcl-xL, Mcl-1, Akt, IAP-1, IAP-2, XIAP, survivin) in cancer cells were involved in TRAIL-resistance [4, 5].