XIAP and neoplasm: Intracellular levels of pro- and antiapoptotic factors such as cFLIP (Kim et al, 2000; Sayers et al, 2003), XIAP (Zhang et al, 2001; Chawla-Sarkar et al, 2002), BCL-2 family members (Burns and El-Deiry, 2001; LeBlanc et al, 2002), and DISC formation and caspase 8 activity (Trauzold et al, 2003) have been reported to regulate cell sensitivity to TRAIL-induced programmed cell death in both tumour and normal cells.