Cellular expansion of CD34⁺ cells with increasing doses of imatinib. Mobilized CD34⁺ cells from donors with nonhematopoietic disorders were expanded in serum-free medium (SFM) supplemented with growth factors starting with 1 × 10³ cells/well under increasing doses of imatinib (0-10 μM). The average cell number per well was determined every third day for a total of 12 days in culture. The mean ± SE of replicate experiments (n = 3) is shown. The asterisk (*) indicates significantly reduced expansion in imatinib-treated as compared to control cells at day 12 (P < .001).