Regarding KRAS oncogene, despite the fact that KRAS-MAPK pathway is downstream of EGFR signalling, KRAS-mutation-driven lung cancers, which are mostly adenocarcinomas, do not respond to EGFR TKIs [88] because the mutations in KRAS activate and release mutant KRAS from the upstream regulation. Here, EGFR is linked to adenocarcinoma.