Loss of Prdm11 accelerates MYC-induced lymphomagenesis in vivo. (A) IB of unsorted, B220⁺, and B220^– murine splenocytes from Eµ-Myc^–;Prdm11 WT and Eµ-Myc^–;Prdm11 KO mice. PAX5 was used as a sorting control and GAPDH served as a loading control. The arrows mark the 3 major PRDM11 protein species, which are also present in the human Toledo lymphoma cell line detected by α-PRDM11 monoclonal antibody (n = 2). (B) Kaplan-Meier plot of survival probability of Eµ-Myc;Prdm11 WT (n = 82) and Eµ-Myc;Prdm11 KO (n = 65) mice. Tumors occurred earlier in Eµ-Myc⁺;Prdm11 KO mice (P = .0017, log-rank test). (C) Representative micrographs of end-stage LN tumors from Eµ-Myc;Prdm11 WT or Eµ-Myc;Prdm11 KO mice immunostained with Ki67, B220, or CD3 antibodies. Scale bar = 50 µm. (D) Summary of immunophenotypes of lymphomas from mice with the indicated genotypes. T1: transitional T1 B cell. (E) IB analysis of the p53-p19^ARF pathway in a panel of end-stage splenic tumors from male (left) and female (right) Eµ-Myc;Prdm11 WT or Eµ-Myc;Prdm11 KO mice. High p53 protein levels, indicative of missense mutations in p53, were detected in 6 of 14 WT tumors and 8 of 20 KO tumors (P > .05, Fisher’s exact test), whereas loss of p19^ARF was seen in 10 of 14 WT tumors and 13 of 20 KO tumors (P > .05, Fisher’s exact test). Vinculin served as loading control. p19^ARF is marked by an arrow. The male and female tumors were run on separate gels. (F) IB of PRDM11 in a panel of splenic end-stage EµMyc;Prdm11 WT tumors. EµMyc;Prdm11 KO tumors and control (spleen from C57BL/6 mouse) were used as controls (Ctr) for the specificity of the α-PRDM11 monoclonal antibody. The 3 major PRDM11 protein species are indicated by arrows; asterisks mark endogenous immunoglobulin heavy and light chains. Vinculin served as loading control.