High‐resolution mapping of amplicons of the short arm of chromosome 1 in two neuroblastoma tumors by microarray‐based comparative genomic hybridization

Deletion of chromosome arm 1p is one of the most frequent genetic alterations in neuroblastoma. However, using conventional comparative genomic hybridization, we have observed amplifications on 1p in 2 neuroblastoma tumors at bands 1p34.2 and 1p36.3, respectively. Using a medium-resolution genomic array containing 178 PACs/BACs from 1p and then 2 high-resolution arrays containing contigs of overlapping PACs/BACs from the amplified regions, we could precisely map and delineate both amplicons. The 1p34.2 amplicon appeared as a homogeneous amplification unit, whereas the 1p36.3 amplicon had a more complex structure, with 2 noncontiguous, highly amplified regions and several moderate amplification units. In this case, fluorescence in situ hybridization analysis confirmed the amplification of several clones and indicated that the 2 highest amplification units corresponded to 2 populations of double minute chromosomes, one of which also contained the MYCN locus. This is the first report of 1p amplifications in primary neuroblastomas.