Dasatinib therapy induces initial responses followed by clinical relapses. (A) Whole-animal luminescent signals (photons/s/cm²/sr) from recipient mice that received 2 × 10⁵Arf^−/−p185⁺luc⁺ LICs were acquired at the start (St) of dasatinib therapy 10 days after injection of LICs (n = 36). Serial images were obtained 1 week (1w; n = 37), 2 weeks (2w; n = 31), or 3 weeks (3w; n = 27) after twice-daily (5 days per week) dasatinib therapy or at clinical relapse (Rel; n = 16). For comparison, the imaging signals obtained from moribund, vehicle-treated mice (Veh; n = 4) are also presented. Median values ± standard errors are indicated by horizontal lines and brackets, respectively. (B-E) Quantitative in vitro luminescence intensities plotted as relative light units (RLUs, ordinate) were performed on 100 μL of erythrocyte-free whole blood (B) and 1 × 10⁶ suspended bone marrow (BM) cells (C) prepared from representative mice taken from cohorts depicted in panel A. In situ spleen (D) and cervical lymph node (LN) luminescence signals (E) recorded in photons/second (ordinate) were acquired from intact whole tissues. Four mice were analyzed in each group (except Rel, where n = 15). Values in panels B-E are presented as median ± SE. The empirically determined lower limits of sensitivity are indicated by dotted lines at the bottom of the panels.