Synchrony of Burkitt Lymphoma Cells Induced by Hydroxyurea

Synchronization of Burkitt lymphoma cells grown in suspen-sion was attempted taking advantage of the dual action of hydroxyurea (HU) of blocking the entry G1 cells into S phase and the selective inactivation of S phase cells. The drug at 0.85 mM concentration prevented the incorporation of 3H-thymidine into DNA by more than 95 % and killed a certain fraction of cells which was comparable to a fraction of S phase cells except for the late S phase cells. This drug, however, allowed cells in other phases to progress through the cycle. The exposure time needed to synchronize the cell population was 15 h which was about 6 h longer than G1+ G2 + M periods. The extra-time of 6 h was due to the delayed progression of late S and G2 cells through the cell cycle. The synchronized growth curve determined by either soft agar colony assay or electronic counting was composed of two fractions showing different rates of division. It seemed that rapidly and slowly dividing fractions were derived from fractions of ce ls at G1 phase and at G2 + late S phase, respectively, when HU was introduced. The delaying effect of HU on the progression of G2 and late S cells appeared to be a limiting factor of the induced synchrony. Miyamoto, Tadaaki;Watanabe, Michinori;Takabe, Yosinobu;Terasima, Toyozo