Comparison of the ability of mobilized LD-PBCs collected from treated mice followed by a single injection of SB-251353 to rescue lethally irradiated mice.

(A) Long-term (more than 100 days) survival after transplantation of SB-251353– and/or G-CSF–mobilized LD-PBCs. Analysis of mobilized long-term repopulating stem cells by SB-251353 alone, G-CSF alone, or the combination of SB-251353 plus G-CSF was determined by limiting dilution analysis. SB-251353 was administered as a single SQ injection (2.5 mg/kg), and 50 μg/kg G-CSF was administered SQ bid for 4 days. Irradiated recipients were injected with mobilized LD-PBCs by tail vein injection. Each time point represents n = 20-30 mice per time point. Survival of at least 50% was statistically increased compared with PBS by a nonparametric Fischer exact test (P < .001). (B) PCR analysis of donor origin of long-term hematopoietic progenitor cells from mice that received transplantations with SB-251353–mobilized stem cells. Bone marrow from 7 of 10 surviving mice more than 100 days after transplantation was grown in a CFU-GM assay. Representative analysis of the Y chromosome region in 9 CFU-GMs isolated from marrow cultures of a single female mouse at more than 100 days after transplantation with SB-251353–mobilized LD-PBCs from syngeneic male donor mice. Similar analysis of 42 CFU-GMs from 6 additional mice that received transplantations (4-9 CFU-GMs per mouse) demonstrated that 98% of colonies were positive for the Y region. All colonies were analyzed for RNA for both PDGF receptor (700-bp band) and the Y chromosome (400-bp band) by PCR. PCR analysis on CFU-GM from normal male (M) and female (F) mice was used as control.