FLOW CYTOMETRIC ANALYSIS OF THE CELL-CYCLE OF THE LEUKEMIC-CELL LINESTREATED WITH ETOPOSIDE AND CYTOSINE-ARABINOSIDE

Effects of etoposide (VP-16) and cytosine arabinoside (Ara-C) on the c ell cycle of HL-60 and THP-1 cells mere studied by flow cytometry usin g the bromodeoxyuridine (BrdU)/DNA assay technique to investigate the efficacy of VP-16 for monocytic leukemia cells. VP-16 inhibited the pr oliferation of THP-1 cells more strongly than that of HL-60 cells at a ny concentrations used at 24 and 48 hr. VP-16 arrested HL-60 and THP-1 cells in the G(2)/M phase and reduced them in the G(0)/G(1) and early S phase at higher concentrations. There was no significant difference in the percentage of G(2)/M phase cells at the same concentration bet ween both cells. However, reduction in the G(0)/G(1) and early S phase cells was more marked in THP-1 than HL-60 cells significantly. On the other hand, Ara-C perturbed the cell cycle of HL-60 cells more than t hat of THP-1 cells at 24 and 48 hr. These results suggest that the eff ects of VP-16 on the cell cycle may be more intense in THP-1 than HL-6 0 cells, and support the efficacy of VP-16 for treating monocytic leuk emia in vivo.