Among miRs that instead are upregulated in NSCLC, miR-21 is particularly interesting, as it is frequently overexpressed in EGFRM+ NSCLC cell lines, in which it contributes to TKI-resistance by downregulating Phosphatase and TEnsin homolog (PTEN) and Programmed Cell Death protein 4 (PDCD4) expression and thereby activating the PI3K-AKT pathway [260,261]. Here, PTEN is linked to non-small cell lung carcinoma.