The Colony-Forming Cell in the Normal and Leukemic Human Host: Responses to Streptovaricin and Rifamycin SV

Summary

The in vitro effects of streptovaricin complex (SvCx), streptovaricin C (SvC), and rifamycin SV (RiSV) on colony-forming cells (CFCs) from the peripheral blood of 19 normal individuals and 2 patients with chronic myelogenous leukemia (CML) were determined in a soft-agar culture system. All 3 ansamycins, which inhibit the RNAdependent DNA polymerase of oncornaviruses, had strong anti-CFC activity at concentrations <50 μg/ml. The order of potency was RiSV > > SvCx > SvC; the mean 50/e inhibitory concentrations were 2.5, 25, and 42 μg/ml, respectively. Antiproliferative activities of these ansamycins on CFCs from both CML patients were similar and no selective toxicity was observed.