ATM and non-small cell lung carcinoma: Regulation of miRNAs was shown to influence cellular sensitivity to radiation, primarily through modulation of molecules involved in the DDR such as ATM, ATR, RAD51, and DNA-PK.2, 9, 13 In particular, miR-421 suppresses ATM expression and increases sensitivity to IR.15 MiR-214 is upregulated in radio-resistant non-small cell lung cancer (NSCLC) cells relative to their radiosensitive counterparts.24 Overexpression of miR-214 in radiosensitive NSCLC cells protects against RT-induced apoptosis via downregulation of p38 kinase.