N-myc amplification in multiple homogeneously staining regions in two human neuroblastomas.

Abstract

Molecular characterization of 2 human neuroblastoma cell lines has revealed that both contain multiple homogeneously staining regions (HSR), each representing a chromosome site of N-myc amplification. The newly established cell line CHP-382/JK had 2 cytogenetically distinct populations with several identical chromosomal abnormalities, indicating a common progenitor cell. Each population had 1 HSR, 1 on chromosome 5 at q31-34 and the other on chromosome 2 at q31-32. Chromosomal in situ hybridization with the N-myc probe pNb-1 demonstrated that both HSR contained amplified copies of N-myc. Southern blot analysis confirmed amplification of N-myc sequences in genomic DNA of CHP-382/JK. Chromosomal features of CHP-382/JK shared with other neuroblastoma cell lines were the deletion of 1p and the presence of extra 17q material. In addition, the cells were highly reactive to monoclonal antibody PI 153/3 used to identify human neuroblastoma. CHP-382/JK cells were further characterized as neuronal cells by the expression of neurotoxin-responsive Na+ channels. Another neuroblastoma cell line, CHP-134, contained a single cell population with 3 HSR, 1 in the short arm of each chromosome 7 and 1 in the long arm of a chromosome 6. All 3 HSR contained amplified copies of N-myc as shown by in situ hybridization with the N-myc probe pNb-1. One of the 7p HSR was acquired during culture of CHP-134 cells, whereas the 2q HSR of CHP-382/JK was lost. Such findings highlight the continued process of N-myc amplification and transposition in vitro. Amplification of N-myc in multiple HSR apparently has not been documented previously in neuroblastoma cell lines.