Percentage of cells in the S and G₂/M phases after release from hydroxyurea cell-cycle arrest of K562 cells subjected to different AS-ODN treatments.

(A) Cells were treated as follows: ⋄, 1 nM ASH-ODN +ASL-ODN for 48 hours; ○, 1 nM IN-ODN for 48 hours; +, 50 μM DFO for the last 24 hours of incubation (added with hydroxyurea); ▿, untreated cells; ∗, 1 nM ASH-ODN+ASL-ODN for 48 hours plus 10 μM DFO added for the last 24 hours of incubation. After 24 hours, hydroxyurea (2 mM) was added for the last 24 hours of incubation, and cells were harvested and analyzed by flow cytometry as described in “Materials and methods.” (B) The same cells were analyzed by flow cytometry 24 hours after the release from hydroxyurea. Data are from a representative experiment.