Figure 6. Combined Mdm2 overexpression and p73 loss result in increased Bcl-2 expression and reduced apoptosis.

(A) Analysis of Bcl-2 protein expression in Mdm2^Tg;p73+/− B-cell lymphomas. Protein lysates (50ug) from B-cell lymphomas from Mdm2^Tg, Mdm2^Tg;p73+/−, p73+/−, and Mdm2^Tg;p73−/− mice were western blotted for Bcl-2 and the loading control Vinculin (2 tumor samples from each genotype). Lysate from a wild type spleen was used as a control (Lane 1). (B) Quantification of Bcl-2 protein expression as shown in the western blot in Figure 6A. Quantification was performed using ImageJ software. Statistical significance between genotypes was calculated by averaging two biological replicates from each genotype followed by two-tailed unpaired student t-tests. (C). Representative histological sections of B-cell lymphomas subjected to immunohistochemistry using an antibody against mouse Bcl-2 (Top 2 panels) and TUNEL staining (Bottom 2 panels). Of the 12 lymphomas that arose in Mdm2^Tg mice, 7 were examined by immunohistochemistry to identify the cell of origin and apoptosis. Of the 26 lymphomas that arose in Mdm2^Tg;p73+/− mice, 25 were examined by immunohistochemistry (Note: the remaining tumors were evaluated using flow cytometry; See Figure 4B).