A recent study [31] based on animal model and clinical samples clarified that miR-21 overexpression was associated with acquired resistance to EGFR-TKI in NSCLC, which might be caused by miR-21’s function in activating the PI3K/AKT pathway through PTEN and PDCD4 inhibition. The gene discussed is AKT1; the disease is non-small cell lung carcinoma.