High Frequency of p53/MDM2/p14ARF Pathway Abnormalities in Relapsed Neuroblastoma.

PURPOSE Most neuroblastomas initially respond to therapy but many relapse with chemoresistant disease. p53 mutations are rare in diagnostic neuroblastomas, but we have previously reported inactivation of the p53/MDM2/p14(ARF) pathway in 9 of 17 (53%) neuroblastoma cell lines established at relapse. HYPOTHESIS Inactivation of the p53/MDM2/p14(ARF) pathway develops during treatment and contributes to neuroblastoma relapse. METHODS Eighty-four neuroblastomas were studied from 41 patients with relapsed neuroblastoma including 38 paired neuroblastomas at different stages of therapy. p53 mutations were detected by automated sequencing, p14(ARF) methylation and deletion by methylation-specific PCR and duplex PCR, respectively, and MDM2 amplification by fluorescent in situ hybridization. RESULTS Abnormalities in the p53 pathway were identified in 20 of 41 (49%) cases. Downstream defects due to inactivating missense p53 mutations were identified in 6 of 41 (15%) cases, 5 following chemotherapy and/or at relapse and 1 at diagnosis, postchemotherapy, and relapse. The presence of a p53 mutation was independently prognostic for overall survival (hazard ratio, 3.4; 95% confidence interval, 1.2-9.9; P = 0.02). Upstream defects were present in 35% of cases: MDM2 amplification in 3 cases, all at diagnosis and relapse and p14(ARF) inactivation in 12 of 41 (29%) cases: 3 had p14(ARF) methylation, 2 after chemotherapy, and 9 had homozygous deletions, 8 at diagnosis and relapse. CONCLUSIONS These results show that a high proportion of neuroblastomas which relapse have an abnormality in the p53 pathway. The majority have upstream defects suggesting that agents which reactivate wild-type p53 would be beneficial, in contrast to those with downstream defects in which p53-independent therapies are indicated.