ING1 has been identified as a novel candidate tumor suppressor gene using a genetic suppressor element (GSE) strategy. Ectopic expression of ING1 in mammalian cultured cells causes cell cycle arrest and apoptosis through a p53-dependent and/or p53-independent pathway. However, there has been no report on the prognostic significance of the ING1 expression level in human cancers, though the expression of the wild-type ING1 gene is significantly decreased in breast, lymphoid and gastric cancers as compared with their corresponding normal tissues. In order to explore the possible involvement of ING1 in tumorigenesis of neuroblastoma, we examined the expression levels of ING1 mRNA in 32 primary neuroblastomas by using a quantitative real-time PCR. ING1 mRNA was expressed independently of the disease stages. however, low levels of ING1 mRNA were significantly associated with a poor prognosis (log-rank test, p=0.017). Multivariate analysis showed that the expression level of ING1 was closely related to survival (p=0.020), even after controlling with age (p=0.008) or stage (p=0.025), while it was only marginally significant after controlling with TrkA expression (p=0.063). Mutation analysis revealed that there was no mutation or deletion of the ING1 gene except 1 silent mutation at codon 188 in primary neuroblastomas examined. Taken together, our results suggest for the first time that a decreased level of ING1 expression is a novel indicator of poor prognosis in advanced stages of neuroblastoma, and that ING1 may play a crucial role in genesis and progression of neuroblastoma.

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