LMP1/λ-MYC B-cell lymphomas have decreased p27 expression. (A) Representative immunohistochemical analysis of lymph node tumors from 3 to 6 mice of each genotype. Tumors were isolated from the cervical area in LMP1/λ-MYC, LMP2A/λ-MYC, and LMP1/LMP2A/λ-MYC mice and from cervical or abdominal locations in λ-MYC mice. Formalin-fixed samples were stained with hematoxylin and eosin, B220, and p27^kip1 using an EVOS XL microscope with 40× magnification. (B) Percentages of B-cell lymphoma cells to total prepared tumor cells were calculated by flow cytometry staining for B220. Isolated lymphoma cells were prepared using a nylon mesh. (C) Percentages of IgM⁺ cells in total B220⁺ lymphoma cells are indicated. (D) Representative immunoblots of p27^kip1 expression in purified tumor cells. Prepared tumor samples from LMP2A/λ-MYC/Cks1^−/− in which p27^kip levels were similar to WT splenic B cells were used as a control. (E) P27^kip1 expression was normalized to Gapdh. Dot plot graphs represent the mean ± standard deviation. P values were calculated by unpaired t test, *P < .05.