In this study, LUAD cell models with EGFR mutation, TP53 and RB1 co-mutation/inactivation, and ASCL1 overexpression were constructed to represent two different stages of transformation of LUAD into SCLC, the first one is the currently recognized prerequisite for transformation, that is co-mutation/inactivation of TP53 and RB1. This evidence concerns the gene RB1 and small cell lung carcinoma.