Double minutes in mouse neuroblastoma cells and their hybrids.

Cytogenetic studies were carried out on three clones of mouse neuroblastoma cells and six interspecific hybrid cells derived from the mouse neuroblastoma cells with either rat glioma cells and liver cells or Chinese hamster brain cells. The hybrid cells possessed characteristic karyotypes with marker chromosomes originating from the neuroblastoma cells. The parental chromosome constitution in the hybrid cells was clone-specific, even in the clones derived from the same parental cells. Double minutes (DMs) were demonstrated in the neuroblastoma cells and in all the hybrid cells studied. In addition other chromosome aberrations, such as microchromosomes and chromosome pulverization, were also observed in these cells. DMs varied in number and morphology among the cells. The number of DMs per cell correlated positively with the level of ploidy and with the karyological constitution contributed by the parental neuroblastoma cells. The results indicate that DMs have a chromosome nature and that the DMs of neuroblastoma chromosomes were transferred into the hybrid cells.