Expression of TRAIL and its receptors in human brain tumors

Recently, TRAIL has been demonstrated to selectively induce apoptosis in tr ansformed cell lines, and subsequently four receptors (TRAIL-R1-TRAIL-R4) h ave been identified. The ability to transduce death signals is restricted t o TRAIL-R1/TRAIL-R2. In contrast, TRAIL-R3/TRAIL-R4 are unable to activate apoptotic pathways and have therefore been suggested to act as "decoys" pro tecting normal tissues from cell death, However, the biological role of the TRAIL system remains incompletely understood. We analyzed the expression o f TRAIL and its receptors in a panel of human brain tumors (n = 34) and in four glioma cell lines in comparison to normal brain tissue. Constant co-ex pression of TRAIL and of receptors TRAIL-R1, TRAIL-R2, and TRAIL-R3 in diff erent tumor entities as well as in normal brain indicates that additional m echanisms might modulate the previously proposed "decoy" model. Furthermore , in contrast to previous reports, we demonstrate TRAIL and TRAIL-R2 to be present on a transcriptional level in normal brain tissue. Exceptional expr ession of TRAIL-R4 transcripts does not suggest a significant regulatory ro le of this receptor in the human brain and its tumors. (C) 1999 Academic Pr ess.