Beta-catenin levels are increased in Eμ-TCL1–induced tumor cells of Fzd6^+/−, but not Fzd6^−/−, mice. Flow staining is performed on lymphocytes isolated from peripheral blood of 8-month-old Eμ-TCL1^+/−Fzd6^−/− and Eμ-TCL1^+/−Fzd6^+/− littermates as in Figure 3. (A) CD19⁺CD5⁺ and CD19⁺CD5⁻ B cells are gated as shown in the left panels. The right panels show histograms of β-catenin–FITC staining in these 2 B-cell populations (CD19⁺CD5⁺ cells are within the dashed lines). Results for 3 representative mice from each group are shown in panel A. (B) The difference in β-catenin geometric mean fluorescence intensity between CD19⁺CD5⁺ and CD19⁺CD5⁻ populations for every individual mouse and the mean value for each group of mice are shown. The geometric mean difference in Eμ-TCL1^+/−Fzd6^+/− (▲) mice is significantly higher than that of Eμ-TCL1^+/−Fzd6^−/− (●) mice at P < .05 (Student t test).