Extensive genetic heterogeneity in the neuroblastoma cell line NB(TU)1

A neuroblastoma cell line displaying genetically unique features was established from a stage III case of a 20-month-old girl. Southern blotting by the probe pTNB6, which contains exon 1 of the N-myc gene, showed that the primary tumor had in total 4 aberrant bands beside the normal amplified band. The established cell line NB(TU)1 had an aberrant N-myc band (9.0 kb) in addition to the normal band (2.9 kb). Cytogenetic analysis revealed that NB(TU)1 has a composite karyotype composed of at least 7 related karyotypes, which are pseudo-diploid and contain complex chromosomal abnormalities, including translocations, deletions and homogeneously staining regions (HSRs). Such extensive abnormalities were considered to be prominent among known neuroblastoma cell lines, and it was suggested that NB(TU)1 had acquired a certain type of genetic instability. Analysis of N-myc bands in 11 clones of NB(TU)1 showed that the intensity ratio of the normal-sized band (2.9 kb) and the aberrant one (9.0 kb) markedly varied among clones. Moreover, 3 clones showed an additional band with the size of 3.7 kb, which was detectable neither in the parent NB(TU)1 nor in the primary tumor. Thus, NB(TU)1 was shown to be composed of heterogeneous cell components. To further detect such ongoing chromosomal instability, we examined micronuclei formation. NB(TU)1 yielded a larger number of micronuclei than 5 other neuroblastoma cell lines. We conclude that NB(TU)1 has acquired genetic instability detectable by both Southern blotting and cytogenetic analysis.