Effects of HU and SAR expression on K562 cell growth. (A) Growth curve generated as described in “Materials and methods.” ⋄ indicates parental K562 cells; •, HU-treated parental K562 cells; ○, vector-transfected cells; and ▪, SAR-expressing cells. Cell-doubling times were calculated from the graph. (B) Enforced expression of SAR (2 clones are shown) led to dramatic macrocytosis and a relatively immature appearance in some K562 cells, as seen with hematoxylin and eosin staining. HU-treated parental cells are also shown (HU). (C) A sizable fraction of SAR transfectants underwent apoptosis, as shown by TUNEL assays. Apoptotic cells are stained green; the nuclei of cells stained with DAPI are blue. Similarly, K562 cells treated with HU for 24 hours showed some apoptotic cells. (D) Cell-cycle and FACS analysis. SAR-expressing cells were arrested in G1/S phase and showed a decreased G2/M fraction. Cell-cycle analysis was performed after cells were plated for 48 hours. Error bars indicate standard deviation of the mean of 3 independent experiments.
