Despite intensive treatment regimens, high-risk and late-stage
neuroblastoma tends to have a poor survival outcome. Overexpression of the apoptotic regulator,
X-linked inhibitor of apoptosis protein (XIAP), has been associated with
chemotherapy resistance in several
cancers including
neuroblastoma. Here, we report preclinical evidence that XIAP offers an effective therapeutic target in
neuroblastoma. Human and murine
neuroblastoma cells were treated with the Smac mimetic
LBW242 alone or in combination with cytotoxic drugs used clinically to treat
neuroblastoma. Expression of
XIAP protein, but not
mRNA, was highly increased in
neuroblastoma cells compared to healthy adrenal gland tissue, consistent with a posttranscriptional regulation of XIAP expression. Treatment with
LBW242 sensitized human and murine
neuroblastoma cells to
chemotherapy-induced apoptosis, which was mediated by activation of both the intrinsic and extrinsic apoptosis pathways. Although Smac mimetics have been reported to stimulate TNF-α-induced apoptosis by degradation of cellular IAP (cIAP)-1/2, we found that LBW242-mediated sensitization in
neuroblastoma cells occurred in a TNF-α-independent manner, despite induction of cIAP-1/2 degradation and TNF-α expression. Together, our findings show that XIAP targeting sensitizes
neuroblastoma to
chemotherapy-induced apoptosis, suggesting a novel therapeutic approach to treat this childhood
malignancy.