As proved that miR-21 inhibitor can increase apoptosis rate and enhance the sensitivity of radiotherapy in NSCLC A549 and H1299 cells, it is speculated that miR-21 inhibitor can accelerate cell apoptosis and enhance sensitivity of radiotherapy in NSCLC cells by suppressing PDCD4 and inactivating the PI3K/AKT/mTOR signaling pathway. Here, PDCD4 is linked to non-small cell lung carcinoma.