Serial transplantation of Fzr1-deficient B-ALL cells generates more progressive and resistant disease. (A) Survival curves for the indicated numbers of mice receiving primary, secondary, or tertiary transplants of Fzr1-intact or Fzr1-deficient B-ALL cells. P values for comparisons between the 2 types of B-ALL cells for each transplantation were determined with the log-rank test. The data for the primary transplant recipients are the same as those in Figure 2A. (B) Increase in the percentage of GFP⁺ cells in PB between the day of and 3 days after irradiation for secondary transplant recipients that were irradiated 14 days after transplantation. Data are presented as mean ± SD (n = 3 mice per group); *P = .0043. (C) Survival curves for the secondary transplant recipient mice as in (B). The P value for a comparison between the 2 groups was determined with the log-rank test (n = 6 mice for Fzr1-intact and 5 mice for Fzr1-deficient group).