Apoptotic responsiveness of the Ewing's sarcoma family of tumours to tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)

We investigated the cytotoxic responsiveness of 40 cell lines derived from representatives of the Swing's sarcoma family of tumours (ESFT), i.e., Swin g's sarcoma (ES), peripheral primitive neuroectodermal tumour (pPNET) and A skin tumour (AT), to tumour necrosis factor-related apoptosis-inducing liga nd (TRAIL). Incubation with TRAIL at 100 ng/ml induced cell death at 24 hr in 19 of 26 ES, 11 of 12 pPNET and 2 of 2 AT cell lines. Half-maximal cell death concentrations (IC50 values) varied from 0.1 to 20 ng/ml. TRAIL displ ayed potent cytotoxic activity against freshly derived ESFT cell isolates. Cytotoxicity was associated with phosphatidylserine expression and internuc leosomal DNA fragmentation, features characteristic of apoptosis. The apopt otic programme in the sensitive ESFT VH-64 cell line revealed TRAIL-induced activation of FLICE/MACH1 (caspase-8) and CPP32/Yama/apopain (caspase-3) a nd processing of the prototype caspase substrate poly(ADP-ribose) polymeras e. In addition, TRAIL provoked a collapse of the mitochondrial transmembran e potential (Delta Psi(m)), parallelled by a reduction in ATP levels and re lease of cytochrome c from mitochondria into the cytosol. Inhibition of cas pase-8 and caspase-3 by zIETDfmk and zDEVDfmk, respectively, substantially prevented TRAIL-induced apoptosis. However, zIETDfmk, but not zDEVDfmk, red uced TRAIL-mediated Delta Psi(m) dissipation, indicating that TRAIL causes mitochondrial dysfunction through caspase-8 acting upstream of mitochondria . While macromolecule synthesis inhibitors (actinomycin D, cycloheximide) a ugmented susceptibility to TRAIL in TRAIL-responsive cell lines, these agen ts did not render TRAIL-resistant cell lines susceptible to TRAIL. However, the proteasome inhibitor MG132 sensitised to TRAIL in resistant cell lines . Collectively, these results show that TRAIL initiates effective death in the vast majority (80%) of cell lines derived from ESFT. Since TRAIL provok ed cell death in ESFT ex vivo, this cytokine may be a promising drug for th e treatment of ESFT in vivo. Int. J. Cancer 88:252-259, 2000. (C) 2000 Wile y-Liss, Inc.