FCM assay showed that A549GSCs and H1650GSCs have a significant increase in proportions of ALDH1A1bright/CD44high cells (Fig. 2), and we further confirmed that these ALDH1A1bright/CD44high GSCs exhibit increased IC50 values for gefitinib compared to that of their respective parental cells (Table 1 and Fig. 1a and b), and are involved in CSCs but not in EGFR T790M-mediated gefitinib resistance (Supplementary Figure 1), suggesting that ALDH1A1bright/CD44high CSCs in NSCLC/ADC contribute to resistance to gefitinib. Here, EGFR is linked to non-small cell lung carcinoma.