AMD3100 sensitization of APL to Ara-C. (A-C) Syngeneic B6129F1 recipient mice (n = 29) were intravenously injected with 10⁶ APL^luc cells. Twelve days after APL injection, mice were left untreated (control; n = 6) or treated with AMD3100 alone (n = 7), Ara-C alone (n = 8), or the combination of AMD3100 and Ara-C (n = 8). Mice treated with chemotherapy received a single subcutaneous injection of Ara-C (500 mg/kg) on days 12 and 13 after APL injection. Mice treated with AMD3100 received subcutaneous injections of AMD3100 (5 mg/kg) 1 hour before and 3 hours after each Ara-C injection. (A) In vivo bioluminescent imaging of APL^luc cells. One representative animal for each group is shown over time. Photon flux is indicated in the color scale bar. Red arrow indicates initiation of treatment with AMD3100 and/or Ara-C. (B) Expansion of APL^luc cells was quantified in emitted photons over total body area (ventral view). BLI signal intensity at days 15, 19, and 23 after APL injection was significantly reduced in mice receiving the combination of AMD3100 and Ara-C compared with mice receiving Ara-C alone. Each bar represents the mean ± SD of a single experiment with the number of mice in each group exactly as described earlier in the legend. (C) Kaplan-Meier plot of overall survival of mice. Overall survival of leukemic mice is significantly prolonged when mice are treated with the combination of AMD3100 and Ara-C (P < .001 between Ara-C versus Ara-C + AMD3100 cohorts). (D) Syngeneic B6129F1 recipient mice (n = 30) were intravenously injected with 10⁶ nontransduced APL cells. Twelve days after APL injection, mice were left untreated (control; n = 5) or treated with AMD3100 alone (n = 5), Ara-C alone (n = 10), or the combination of AMD3100 and Ara-C (n = 10) exactly as described earlier in the legend. Overall survival of leukemic mice is significantly prolonged when mice are treated with the combination of AMD3100 and Ara-C (P < .001 between Ara-C vs Ara-C + AMD3100 cohorts). *P < .05; **P < .01; and ***P < .001.