ADRIAMYCIN AND DAUNOMYCIN INDUCE PROGRAMMED CELL-DEATH (APOPTOSIS) IN TUMOR-CELLS

HeLa S3 cells exposed to Adriamycin(R) and Daunomycin(R) for 3 hr at EC90 and 10 X EC90 concentrations and incubated in drug-free medium demonstrated the characteristics of apoptosis, morphological changes and fragmentation of DNA into oligonucleosome-sized fragments. The kinetics of DNA degradation after incubation with Adriamycin did not differ significantly at the EC90 and 10 x EC90 concentrations and DNA fragmentation in cells treated with both doses of Adriamycin could be observed after 12 hr of post-incubation in drug-free medium. At the EC90 concentration of Daunomycin, DNA fragmentation was not observed until 24 hr after drug exposure, whereas at the 10 X EC90 concentration apoptosis-related DNA degradation was detectable as early as 3 hr after drug treatment. For both drugs, at both studied concentrations, HeLa S3 cells were arrested in the G2 phase of the cell cycle as can be concluded from cell size distribution studies. Additionally, the growth inhibition of HeLa S3 cells treated with the drugs was observed at concentrations about 10 times lower than those inhibiting DNA synthesis of these cells. At lower concentrations of Adriamycin and Daunomycin (EC90), apoptosis was inhibited by post-incubation with 1 mug/mL cycloheximide whereas at higher concentrations of the drugs (10 X EC90) there was a potentiation of cell death in cycloheximide-treated cells. The presented results suggest that apoptosis may be the process directly responsible for cell killing by Adriamycin, Daunomycin and probably other anthracyclines, in which the cytostatic effect of these compounds leads to cytotoxicity (cell death).