TP53 and neoplasm: Cre-recombinase was delivered to the lungs by nasal inhalation of lentiviral vectors, triggering recombination at twin loxP sites in a small subset of lung epithelial cells, so that expression of the KrasG12D oncogene and luciferase would be switched on, while different combinations of p53, LKB1, and AMPK-α1 plus -α2 would be simultaneously knocked out; growth of tumours could be monitored in vivo via bioluminescence from the expressed luciferase.