Abstract：OBJECTIVE: Tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces cell death in a variety of tumors but not in normal cells. TRAIL- resistance of most neuroblastoma (NB) cell lines is related to the loss of caspase-8 expression and the expression and distribution of membrane TRAIL-receptors. This study investigated the role of caspase-8 and DR5 in TRAIL-induced apoptosis of NB cell line SKNDZ. METHODS: The expression of caspase-8 mRNA was detected by RT-PCR. The expression of DR5 protein was detected by Western Blot analysis. The effects of TRAIL, IFNγ+TRAIL, chemotherapeutic agent (adriamycin or etoposide) + TRAIL, and chemotherapeutic agent +TRAIL+ IFNγ on the growth and apoptosis of SKNDZ cells were detected by MTT assay and flow cytometry. RESULTS: caspase-8 was not expressed in SKNDZ cells but IFNγ treatment resulted in an increase of caspase-8 expression. Expression of DR5 protein was not detected in SKNDZ cells but an increased DR5 protein expression was found after treatment with adriamycin or etoposide. The SKNDZ cells expressing caspase-8 were not sensitive to TRAIL but those SKNDZ cells expressing both caspase-8 and DR5 were sensitive. The early apoptosis rates of the adriamycin /etoposide + IFNγ+TRAIL groups [( 17.9±3.6)%, (14.8±3.3)%] were higher than that of the IFNγ+TRAIL group [(3.9± 1.2)% ](F=26.233, P< 0.01). CONCLUSIONS: SKNDZ cells expressing both caspase-8 and DR5 restored the TRAIL sensitivity. caspase-8 and DR5 play a key role in TRAIL-induced apoptosis of NB cells.
