Expression of N-<TOGGLE>myc</TOGGLE> and <TOGGLE>MRP</TOGGLE> genes and their relationship to N-<TOGGLE>myc</TOGGLE> gene dosage and tumor formation in a murine neuroblastoma model

Although the association between N-myc gene amplification and poor clinical outcome in neuroblastoma is well established, the mechanism by which amplification influences prognosis is not well defined. We used a human N-myc transgenic mouse model to investigate the role of N-myc in neuroblastoma, including its relationship to the multidrug-resistance-associated protein (MRP) gene. We developed a rapid real-time PCR method to distinguish homozygous and hemizygous N-myc mice that is comparable to Southern analysis. A highly significant correlation (P &lt; 0.0001) between N-myc and MRP expression was demonstrated in murine tumors. Amplification of the transgene was observed in the majority of tumors, highlighting the clinical relevance of this model. However, no correlation between N-myc expression and transgene dosage or tumor latency was observed. The data suggest that increased N-myc dosage contributes to increased tumor incidence and decreased latency by mechanisms independent of N-myc expression. Med. Pediatr. Oncol. 35:585–589, 2000. © 2000 Wiley-Liss, Inc.