Fig. 5.

Doxorubicin exposure down-regulates SCF-R/c-Kit expression on CD34⁺ progenitors. a hTERT-MUTZ3, dox90+, and dox90− (4 months drug-free) progenitor cells were analyzed for the expression of the SCF-R/c-Kit. Continuous exposure to doxorubicin abrogated the expression of SCF-R/c-Kit on a subset of CD34⁺ progenitors. SCF-R/c-Kit expression returned upon drug depletion. b wtMUTZ3 cells were cultured in the presence of 0, 30, 100, or 300 nM doxorubicin for 4 days. SCF-R⁺ and SCF-R⁻ CD34⁺ cells were analyzed for their doxorubicin uptake. Left: percentages of SCF-R⁻ (white squares) and SCF-R⁺ (black squares) cells positive for doxorubicin after 4 days with the indicated drug concentrations. Right: doxorubicin uptake in SCF-R⁻ and SCF-R⁺ cells, determined by the mean fluorescence index (doxorubicin mean fluorescence intensity (FL-2 channel) of drug-exposed cells divided by the mean fluorescence intensity of non-exposed (0 nM) cells). *P < 0.05 (n = 3). c Percentages of SCF-R⁻ and SCF-R⁺ cells that died upon doxorubicin treatment, as determined by flowcytometric analysis with propidium iodide (PI). *P < 0.05 (n = 3)