To elucidate whether DDX3X expression was correlated with CSC-like properties, we transfected PC9 cells, lung adenocarcinoma cells harboring an EGFR exon 19 deletion mutation, with cDNA encoding DDX3X and established a novel cell line, termed A-1 cells, which overexpressed DDX3X (Fig. 1A). Here, EGFR is linked to lung adenocarcinoma.