MAPK3 and neoplasm: To assess the effects of restoration in the absence of p53, we initiated lung tumors in KT;Trp53flox/flox (KPT);Lkb1XTR/XTR and KPT;Lkb1XTR/XTR;FLPo-ERT2 mice and began vehicle or tamoxifen treatment at 6 weeks after tumor initiation (Supplementary Fig. 5a).