Tumor Multiplicity and Proliferative Index in <i>p19^Arf /p53</i> Compound Mutant Mice

<div><p>(A) Average number of papillomas (more than 2 mm in diameter) per mouse is plotted against the number of weeks post-initiation.</p> <p>(B) Image of wild-type, <i>p19^Arf (Arf)^−/−, p53^−/−,</i> and <i>p19^Arf−/−p53^−/−</i> mice with skin tumors at time of sacrifice. Wild-type mice show large exophytic tumors, while both <i>p19^Arf</i>- and p53-deficient mice have endophytic tumors. Note larger tumors in <i>p19^Arf /p53</i> compound mutant mice relative to <i>p53</i> single mutants.</p> <p>(C) BrdU-positive cells in papillomas from wild-type<i>, p53^−/−, p19^Arf−/−,</i> and <i>p19^Arf−/−p53^−/−</i> mice at 10 wk postinitiation. (Bars represent average counts ± standard deviation from ten fields and five mice). <i>p53^−/−</i> tumors show significantly fewer BrdU-positive cells than either <i>p19^Arf−/−</i> or wild-type tumors (<i>p</i> < 0.05, Wilcoxon one-sided t-test).</p>