Mouse 2nH1 (ES) cells were examined for polyploidization using
K-252a and
staurosporine. Though 2nH1 cells were polyploidized by both
K-252a and
staurosporine,
tetraploid cells, 4nH1K cells, were obtained only from cell populations exposed to
K-252a. The probability of successful establishment of
tetraploid cells was 2/9, suggesting that the highly polyploidized-
tetraploid transition might occur infrequently. Cell cycle parameters of 4nH1K cells were almost the same as those of 2nH1 cells, suggesting that the rate of
DNA synthesis was about twice that of the diploid cells. The cell volume of 4nH1K cells was about twice of that of diploid cells, indicating that 4nH1K cells contained about twice as much total intracellular material as 2nH1 cells. The morphology of the 4nH1K cells was flagstone-like, thus differing from that of the spindle-shaped 2nH1 cells, suggesting that morphological transformation occurred during the diploid-
tetraploid transition. 4nH1K cells exhibited
alkaline phosphatase activity and formed
teratocarcinomas, implying that they were pluripotent. These characteristics of 4nH1K cells were similar to those of
tetraploid 4nH1 cells that have been established through polyploidization by
demecolcine, suggesting that 4nH1K and 4nH1 cells are similar irrespective of the different mechanisms of polyploidization.