Incidence of mediastinal lymphomas and changes in DNA methylation in Eμ-Myc, Eμ-Myc/DNMT3B7, and Eμ-Myc/Dnmt3b^+/− mice. (A) Eµ-Myc/Dnmt3b^+/− (dotted line) vs Eµ-Myc/DNMT3B7 (dashed line) and Eµ-Myc mice (solid line). Cumulative incidence curves were compared using the K-sample test (Eµ-Myc vs Eµ-Myc/Dnmt3b^+/−: P < .0001; Eµ-Myc vs Eµ-Myc/DNMT3B7: P = .009).⁵  (B) Growth curves of cell lines established from mediastinal lymphomas of Eµ-Myc (solid line), Eµ-Myc/DNMT3B7 (dashed line), and Eµ-Myc/Dnmt3b^+/− mice (dotted line). Curves were compared using 2-way analysis of variance (ANOVA) (P = .012). (C) Total 5-methylcytosine levels were quantified by liquid chromatography-electrospray ionization/tandem mass spectometry,¹⁰  n ≥ 4 for each genotype. DNA methylation levels were normalized to wild-type (WT) peripheral blood B cells (gray bar). The 2-tailed Student t test was used to compare global DNA methylation. (D-G) Relative quantification of Dnmt levels, normalized to β-Actin levels. Dnmt1 (D), Dnmt3a (E), Dnmt3b (F), and Dnmt3l (G) levels in WT lymph node (LN) (gray bar) and Eµ-Myc (white bar), Eµ-Myc/DNMT3B7 (hatched bar), and Eµ-Myc/Dnmt3b^+/− (striped bar) cell lines. P values were calculated by ANOVA, using WTLN as the control.