TP53 and neoplasm: However, when KrasG12C were compared with KrasG12D mice matched for time after AdCre inhalation, there was a striking difference in tumorigenic properties between KrasG12D and KrasG12C models on both tp53 wild-type (tp53WT) and tp53KO backgrounds: KrasG12D-expressing mice had a dramatically increased tumor burden compared to KrasG12C (Fig. 1C, D).