Intratracheal delivery of lentivirus-expressing Cre and an Msh2-targeting single guide (sg)RNA (sgMsh2) into the former or alveolar type II, cell-specific, adenovirus-expressing Cre into the latter induced lung adenocarcinomas with efficient MSH2 knockout (Fig. 1a–c and Extended Data Fig. 1a–e). Here, MSH2 is linked to lung adenocarcinoma.