TP53 and neoplasm: Reduction in Trp53 protein was also seen in Kras;Trp53−/−-targeted tumors relative to normal tissue and Kras;Stk11−/−-targeted tumors with a 70% and 75% reduction in Trp53 and Stk11 protein relative to normal lung tissue, respectively, confirming the corresponding genotypes in these heterogenous masses of tumor and stromal cells (Fig. 4d).