Maintenance of near-diploid karyotype of PA-1 human ovarian teratocarcinoma cells due to death of polyploid cells by chromosome fragmentation/pulverization.

Abstract

Chromosome instability (polyploidy or aneuploidy) is one of the characteristics of malignant tumors. Human teratocarcinoma cell line PA-1, which was established more than 10 years ago, consists of a majority of near-diploid cells and a minority of polyploid cells, indicating that it is karyologically very stable. In the present study we investigated this genomic stability from the view point of cytogenetics. Cleavages and breaks in the chromosome were found in the metaphase of PA-1 polyploid cells, accompanied by the formation of polynucleosomal DNA fragments. These findings were absent in the near-diploid cells. In addition, polyploid cells did not show colony-formation ability by in situ analysis of cytogenetics in each colony. Thus, the maintenance of the near-diploid karyotype in PA-1 cells may be due to a blockage in the M-phase of the polyploid cells by functional mitotic checkpoints, if any, leading to cell death due to inability to enter the next cell cycle.