This procedure triggers recombination at twin loxP sites in a small subset of lung epithelial cells, in which expression of KRASG12D and luciferase would be switched on, and p53 and/or LKB1 and/or AMPK-α1/-α2 would be knocked out; expression of luciferase also allowed tumours to be imaged by bioluminescence, and thus their growth to be monitored in vivo. Here, TP53 is linked to neoplasm.