APOPTOTIC DAMAGE OF DNA IN HUMAN LEUKEMIC HL-60 CELLS TREATED WITH C2-CERAMIDE WAS DETECTED AFTER G1 BLOCKADE OF THE CELL-CYCLE

Apoptosis was induced by treatment of HL-6O cells with C2-ceramide. Ap optotic damage of DNA was detected according to the sub-G1 peak on a f low cytometer, according to the typical morphology and according to th e DNA fragmentation ''ladder'' after gel electrophoresis. It was shown that the apoptotic cleavage followed after G1 blockade of the cell cy cle. A high correlation coefficient (r(s)=0.957) was found between the percentages of G1 blocked cells and apoptotic cells. This high correl ation together with the appearance of the sub-G1 peak suggests that th e G1 blocked HL-60 cells were subject to apoptotic death. It is deduce d that the mechanisms leading to G1 blockade of the cell cycle and act ivation of apoptosis in HL-60 cells are interconnected.