KRAS and infection: Administration of the viral Cre recombinase via the trachea induces the genetic rearrangement of the Lox-stop-Lox cassette to activate oncogenic Kras and delete the tumor suppressor p53. Lung tumors developed uniformly with 100% penetrance and tumors can distinctively be observed two to 3 months post-infection (Masri et al., 2016; Verlande et al., 2021).