mRNA expression of Fas receptor (CD95)‐associated proteins (Fas‐associated phosphatase‐1/FAP‐1, Fas‐associating protein with death domain/FADD, and receptor‐interacting protein/RIP) in human leukaemia/lymphoma cell lines

mRNA expression of Fas (CD95)-associated proteins [Fas-associating protein with death domain (FADD), receptor-interacting protein (RIP), and Fas-associated phosphatase-1 (FAP-1)] has been investigated in 26 Fas-positive human leukaemia/lymphoma cell lines. Reverse transcriptase-polymerase chain reaction analysis revealed that FADD and RIP mRNA were invariably expressed in both Fas-sensitive and Fas-insensitive cell lines. However, FAP-1 mRNA was detected in only 11 of 26 cell lines. Interestingly 7/14 cell lines in the Fas-sensitive group were positive for FAP-1 mRNA expression. 8/12 cell lines in the Fas-refractory group did not express FAP-1 mRNA, but half of these cell lines were susceptible to tumour necrosis factor alpha-induced growth inhibition. These findings suggest that the presence or absence of FAP-1 mRNA expression did not always correlate with relative sensitivity of Fas-mediated growth inhibition. Furthermore, it is assumed that leukaemia/lymphoma cells could possess structural or functional defects of Fas or Fas-associated proteins resulting in the failure to trigger apoptotic cell death.