Different manner of DNA synthesis in polyploidizations of meth-A and B16F10 cell lines.

Polyploidization of Meth-A and B16-F10 cells by demecolcine was examined using flow cytometry (FCM). In the presence of demecolcine, both cell lines were polyploidized to more than 16c DNA content. A marked difference was observed in the durations of S phase of polyploidy. The S-phase duration of Meth-A cells was doubly increased with ploidy, but that of B16F10 cells remained constant. When the rate of DNA synthesis in the polyploidizing cells was examined through the BrdU-uptake experiments, it was confirmed that the level of DNA-synthesis rate was constant in Meth-A cells but increased in B16F10 cells. The cellular content of c-Myc protein in polyploidized cells was also examined using anti-c-Myc monoclonal antibody. The c-Myc level of Meth-A cells was constant regardless of the ploidy but that of B16F10 cells increased with ploidy. Thus, the c-Myc content seems to be related to the duration of S phase in polyploidy.