By contrast, ectopic expression of TAp63γ, a p63 isoform that has the strongest transcriptional activity among all the splice variants, dramatically induced the expression of CCDC3 and p21 (as a control) at RNA levels in p53-null H1299 lung adenocarcinoma cells, but the induction was not observed when the cells overexpressed p40 (Fig. 1a), which is a shorter and transcriptionally inactive isoform of p63 without the TA domain13, 14. This evidence concerns the gene TP53 and lung adenocarcinoma.