Effects of pharmacologic inhibition of the mTOR/p70 S6 kinase pathway in the generation of the inhibitory effects of imatinib mesylate and IFNα on primary leukemic progenitors. Peripheral blood or bone marrow mononuclear cells isolated from different patients with CML were plated in a methylcellulose culture assay system with imatinib mesylate (1 μM; A) or IFNα (1000 IU/mL; B), in the presence or absence of rapamycin, as indicated. Leukemic CFU-GM progenitor colonies were scored on day 14 of culture. (A) Comparison of the effects of imatinib mesylate alone versus imatinib mesylate plus rapamycin. Means plus SE of the values from the experiments using different patient samples (cases 1, 2, 3, and 5 from Table 1) are shown. (B) Comparison of the effects of IFNα alone versus IFNα plus rapamycin. Means plus SE of the values from the experiments using different patient samples (cases 2, 3, 4, and 6 from Table 1) are shown.