Abstract:
Objective This study aims to evaluate the role of Caspase 8 and death receptor (DR) in TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis of neuroblastoma (NB) cell lines.
Methods Caspase 8 mRNA expression in NB cells before and after treatment with IFNγ was monitored through reverse transcriptase-polymerase chain reaction. Caspase 8, DR5, and DR4 protein expression was monitored through Western blot analysis. The effects of IFNγ, TRAIL, IFNγ + TRAIL, Caspase 8 inhibitor + TRAIL, and IFNγ + etoposide/doxombicin + TRAIL on the growth and apoptosis of NB cells were detected through MTT and flow cytometry.
Results The expression of Caspase 8 mRNA and protein was induced by IFN7 in the NB cell line SKNDZ. SY5Y cells were resistant to TRAIL. However, the combination treatment of IFN7 + TRAIL and IFNy + etoposide/doxorubicin + TRAIL significantly induced cell apoptosis in SY5Y cells. The early stage apoptosis rate of SY5Y cells in the IFN7 + TRAIL group (23.09 ± 2.35) % was significantly higher than that in the TRAIL group (6.15 ±0.54) % (P< 0.01), but was significantly lower than that in the IFN7 + dox/eto + TRAIL group (43.41 ± 6.46) %/ (38.86±7.29) % (P< 0.01). Moreover, etoposide or doxorubicin induced DR5 but not DR4 in NB cell lines. SKNDZ cells expressing Caspase 8 after treatment with IFNγ were still resistant to TRAIL but subsequently became sensitive to TRAIL after the induction of DR5 through the treatment of etoposide or doxombicin. The early stage apoptosis rate of the IFNγ + dox/eto + TRAIL group (11.54 ± 2.49) %/ (13.38± 1.65) % was significantly higher than that of the IFNy + TRAIL group (P< 0.01).
Conclusion Sensitization of NB cells to TRAIL may be mediated by the upregulation of Caspase 8 with IFNγ and DR5 with etoposide or doxombicin. The results suggest that Caspase 8 and DR5 play key roles in TRAIL-induced apoptosis of NB cells.