PTEN down-regulation in K562 cells and inhibition of K562 cells by rapamycin. (A) PTEN protein level was elevated by K562 cells treated with imatinib (IM). K562 cells were treated with imatinib (1μM) for 24 hours, and protein lysates were analyzed by the use of Western blotting with the antibodies indicated. (B) Rapamycin inhibits proliferation of K562 cells. K562 cells were treated with DMSO or rapamycin (10μM) for 48 and 72 hours, and live cells were counted. (C) Rapamycin induces apoptosis of K562 cells. K562 cells were treated with DMSO or rapamycin (10μM) for 48 hours. Apoptotic cells (annexin V⁺/7AAD⁺) cells were analyzed by FACS.