FAS and acute lymphoblastic leukemia: Fas downregulation is recognised as one of the mechanisms for evading the Fas–FasL system in other types of tumours, and a similar loss of Fas was shown to be a negative prognostic factor in acute lymphoblast leukaemia (Suminoe et al, 2004), lung cancer (Koomagi and Volm, 1999) and pancreatic cancer (Bernstorff et al, 2002).