Cks1 knockout decreases the pretumor B-cell population in LMP2A/λ-MYC mice. (A) Spleens were isolated from 4-week-old mice at the pretumor stage, and spleen weights as a percentage of whole body weight are indicated. (B) Lymphocytes were isolated from the bone marrow (BM) and spleens (SP) of pretumor mice, and their B- and T-cell numbers and percentages were calculated by flow cytometry stained with B220-allophycocyanin and CD3ε- phycoerythrin antibodies. Data represent the mean ± standard deviation. (C) The percentage of IgM-positive cells to total splenic B cells were calculated by staining with IgM-FITC antibody. (D) Representative immunohistochemical analysis of 4-week-old mouse spleens from 3 mice of each genotype stained with B220 (original magnification ×4). The statistic differences of Cks1 knockouts against their controls are indicated with thick lines. *P < .05, **P < .01, ***P < .001, ****P < .0001, calculated by 1-way ANOVA with post hoc multiple comparison tests. MYC, λ-MYC mice; 2A MYC, LMP2A/λ-MYC mice.