AKT1 and non-small cell lung carcinoma: As shown in Fig. 3d, PTEN expression levels were reduced in the resistant cell lines compared to the parental cell lines, whereas the other proteins upstream of the AKT pathway were not decreased in the resistant cell lines compared to the parental cell lines, indicating that insufficient PTEN expression contributes to AKT activation in EGFR-TKI-resistant NSCLC cells.