title: Preferential occurrence of chromosome breakpoints within early replicating regions in neuroblastoma.
abstract: Neuroblastoma (NB) is a frequent paediatric extra cranial solid tumor characterized by the occurrence of unbalanced chromosome translocations, frequently, but not exclusively, involving chromosomes 1 and 17. We have used a 1 Mb resolution BAC array to further refine the mapping of breakpoints in NB cell lines. Replication timing profiles were evaluated in 7 NB cell lines, using DNAs from G1 and S phases flow sorted nuclei hybridised on the same array. Strikingly, these replication timing profiles were highly similar between the different NB cell lines. Furthermore, a significant level of similarity was also observed between NB cell lines and lymphoblastoid cells. A segmentation analysis using the Adaptative Weights Smoothing procedure was performed to determine regions of coordinate replication. More than 50% of the breakpoints mapped to early replicating regions, which account for 23.7% of the total genome. The breakpoints frequency per 10(8) bases was therefore 10.84 for early replicating regions, whereas it was only 2.94 for late replicating regions, these difference being highly significant (p < 10(-4)). This strong association was also observed when chromosomes 1 and 17, the two most frequent translocation partners in NB were excluded from the statistical analysis. These results unambiguously establish a link between unbalanced translocations, whose most likely mechanism of occurrence relies on break-induced replication, and early replication of the genome.
authors.affiliation: Laboratoire de Pathologie Moléculaire des Cancers, Institut Curie, Paris, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Janoueix-Lerosey
authors.forename: Philippe
authors.initials: P
authors.lastname: Hupé
authors.forename: Zofia
authors.initials: Z
authors.lastname: Maciorowski
authors.forename: Philippe
authors.initials: P
authors.lastname: La Rosa
authors.forename: Gudrun
authors.initials: G
authors.lastname: Schleiermacher
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Pierron
authors.forename: Stéphane
authors.initials: S
authors.lastname: Liva
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Barillot
authors.forename: Olivier
authors.initials: O
authors.lastname: Delattre
mesh_terms: D045744:Cell Line, Tumor; D019457:Chromosome Breakage / Q000235:genetics*; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics; D042522:DNA Replication Timing / Q000235:genetics*; D015894:Genome, Human / Q000235:genetics; D006801:Humans; D009447:Neuroblastoma / Q000235:genetics* / Q000473:pathology; D016196:S Phase / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured