Blockade of CXCR4-driven motility delays the contribution of Kras-mutant HSC. (A) Representative snapshots of intravital imaging of reporter mice before or after the administration of the CXCR4 inhibitor LY2510924. Red and green signals represent Tom⁺ cells and autofluorescent macrophages, respectively; select Tom⁺ cells are marked by gray spheres, and their tracks are indicated. Data are representative of two to three mice per group. Scale bar, 10 µm. (B) Representative flower plots showing tracks of individual Tom⁺ cells (marked by different colors) relative to each cell’s starting point before or after treatment with LY2510924. (C and D) Track velocity and displacement velocity of Tom⁺ cells before and after treatment with LY2510924 (C) and their corresponding MSD (D). Individual Tom⁺ WT cells (426 cells from three mice) and Tom⁺Kras-mutant cells (1,108 cells from two mice) were analyzed. Lines on violin plots indicate median and quartiles; on MSD graphs, MSD values are plotted as a function of time and MSD rates for each condition, determined by linear regression analyses, are indicated. (E) Effect of CXCR4 antagonist on the contribution of Kras^G12D-mutant HSC to hematopoiesis. Kras^G12D or WT reporter animals were induced with tamoxifen, and 2 wk later were injected s.c. with LY2510924 or PBS twice a day for 1 wk, followed by endpoint analysis. (F–H) Accrual of Kras-mutant cells in reporter mice after LY2510924 or control treatment. Shown are the fractions of Tom⁺ cells in the stem/progenitor cells in the BM (F) and mature cells in the spleen (G) and BM (H). Symbols represent individual mice; bars represent the mean ± SD of the data pooled from three independent experiments. Statistical significance was estimated by unpaired Student’s t test (C) or the Mann–Whitney test (other panels). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.