Rapamycin enhances doxorubicin-induced apoptosis of ALL cells. Mean values ± SD of apoptosis of ALL blasts, from 8 responder samples (A; patients 1, 2, 3, 6, 11, 14, 18, 19) and 7 nonresponder samples (B; patients 4, 5, 7, 9, 12, 15, 20), incubated for 24 hours with and without rapamycin (100 ng/mL) or doxorubicin (0.5 μM). (C) Dose/response effect of rapamycin on doxorubicin-induced apoptosis. ALL cells (patient 7) were cultured with and without 0.5 μM doxorubicin and with or without rapamycin at the indicated concentrations; 24 hours later, apoptosis was measured by annexin V staining. (D) Flow cytometry diagrams of apoptosis of blasts, from patient 20, cultured with doxorubicin at the indicated concentrations, with and without rapamycin (100 ng/mL). The percentages on the bars indicate the amount of annexin V-positive cells.