To validate the impact of aging on the tumor-suppressive function of PTEN outside of a pooled setting, we initiated tumors in young and aged KrasLSL-G12D/+;Rosa26LSL-tdTomato;H11LSL-Cas9 (KT;H11LSL-Cas9) mice with a lentiviral vector encoding Cre recombinase and a Pten-targeting sgRNA (‘sgPten’ vector; Fig. 3d and Extended Data Fig. 4e). Here, PTEN is linked to neoplasm.