BACKGROUND: The p53 tumor suppressor gene has been reported to be rarely mutated in neuroblastoma tumors at diagnosis, while mutations have been found in cell lines established from relapsed or progressive tumors. Here, we undertook a systematic study of the p53 mutational status in neuroblastoma cells, combined with assessment of MDM2 amplification, p14ARF deletion, and functional analysis of the p53 pathway.
METHODS: The entire coding region of the p53 gene from 34 human neuroblastoma cell lines was analyzed by direct sequencing. Alterations in gene copy number of MDM2 and p14ARF were investigated using quantitative real-time PCR. Functional integrity of the p53 pathway was probed by the decrease in cell viability after treatment with the selective MDM2 antagonist nutlin-3.
RESULTS: We identified 9 cell lines (26.5%) with a mutation in the p53 gene, including 6 missense mutations, 1 nonsense mutation, 1 in-frame deletion, and 1 homozygous deletion of the 3’ end of the p53 gene. Additionally, MDM2 amplification and homozygous deletion of the p14ARF locus were each found in two cell lines. Sensitivity to nutlin-3 was highly predictive of absence of p53 mutation. Cell lines with wild-type p53 were subject to extensive nutlin-3 induced cytotoxicity in 21 out of 25 cases, indicating that p53 downstream signaling pathways are not a major target for escape of p53 surveillance in neuroblastoma cells.
CONCLUSIONS: Mutation of the p53 gene is not a rare event in neuroblastoma cell lines. Deregulation of the p14ARF-MDM2-p53 axis appears to be a common theme, while p53 signaling pathways are usually not affected by inactivating lesions. Our results support existing evidence that selective MDM2 antagonists might be beneficial for treatment of neuroblastoma tumors without p53 mutation.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA