Positional gene expression analysis identifies 12q overexpression and amplification in a subset of neuroblastomas

Neuroblastoma is a heterogeneous disease with variable clinical behaviors. Unique molecular features are associated with clinically relevant subgroups. We performed a comprehensive microarray gene expression analysis of 95 neuroblastomas in an effort to define clinically important molecular subtypes. A subset of tumors overexpressed several contiguous genes located at 12q13 approximately q15 and were studied further. By microarray, 5 of 95 neuroblastomas had overexpression of genes mapped to 12q13.1 approximately q15, suggesting an amplification event in this region. Positional expression mapping identified the narrowest region of overlap containing 21 genes, with 11 genes overexpressed in all five cases. Fluorescence in situ hybridization demonstrated 3 neuroblastomas with more than a 10-fold increase in 12q gene copies and 9 with 3- to 5-fold increases. Amplification and overexpression of genes at 12q13 approximately q15 were observed in a small subset of neuroblastomas. Although amplification of 12q has been previously reported in neuroblastoma cell lines, this is the first demonstration in tumor samples, and it defines a distinct subset that has not been described previously. The expressed genes mapped closely to the complex amplicon reported in sarcomas, and they identify critical genes and pathways affected by 12q gene amplification.