Abstract：OBJECTIVE: The loss of casepase-8 expression correlates with unfavorable survival outcomes in neuroblastoma (NB). Casepase-8 gene inactivation is caused by methylation. This study aimed to explore the effect of the demethylation agent 5-azacytidine on casepase-8 expression and whether 5-azacytidine can increase the sensitivity of chemotherapy drug doxorubicin to NB cells. METHODS: Caspase-8 mRNA expression in NB cell lines (SH-SY5Y cells) was examined by RT-PCR before and after 5-azacytidine treatment. Survival rates of SH-SY5Y cells were detected using MTT analysis and compared among the doxorubicin alone treatment, 5-azacytidine along with doxorubicin treatment, and caspase-8 inhibitor+5-azacytidine+doxorubicin treatment groups. RESULTS: Caspase-8 mRNA was not expressed in untreated SH-SY5Y cell lines. Caspase-8 mRNA expression in SH-SY5Y cells was detectable 3 days after 5-azacytidine treatment, and increased significantly 5 days after 5-azacytidine treatment (P<0.05). Survival rates of SH-SY5Y cells treated with 5-azacytidine along with different concentrations of doxorubicin (0.05, 0.1,0.25, 0.5 μg/mL) were (77.61±7.30)%, (57.35±6.64)%, (46.25±4.46)% and (35.59±5.12)%, respectively, which were significantly lower than those treated with doxorubicin alone (94.89±4.15%, 80.60±8.50%, 64.48±4.92% and 52.32±6.71%) (P<0.01). Caspase-8 inhibitor pretreatment resulted in an increased survival rate of SH-SY5Y cells (92.95±3.48%, 78.39±4.28 %, 62.31±6.50% and 49.92±5.77%)compared with the 5-azacytidine+doxorubicin treatment group. CONCLUSIONS: 5-azacytidine may enhance anti-tumor efficacy of doxorubicin to NB cell lines, possibly through an up-regulation of caspase-8 mRNA expression.［Chin J Contemp Pediatr, 2007, 9 (6):577-579］
