Comparison of in vivo parameters and tumor development in WT and mutant-BTK–expressing MEC-1 cells. MEC-1 cells harboring WT or mutant BTK were injected into 8-week-old Rag2^−/−γ_c^−/− female mice (n = 10 per group), and the animals were monitored for body weight and development and progression of leukemia. At the end point of the study, the spleens, livers, and femurs were collected and macroscopically evaluated. (A) Body weight of mice (n = 10 per group) in each cohort. (B) Spleen/body weight ratios of mice in each cohort (n = 8 BTK^WT, n = 9 BTK^C481S, n = 10 BTK^C481R; *P < .05). (C) Liver/body weight ratios of mice in each cohort (n = 8 BTK^WT, n = 9 BTK^C481S, n = 10 BTK^C481R). Groups were compared by fitting a linear mixed-effect model for analysis of variance. (D) Kaplan-Meier curves depict the overall survival of mice in each group (n = 10 per group; mutant vs WT, log-rank test; P = .0001).