STAT3 and non-small cell lung carcinoma: Signal transducer and activator of transcription 3 (STAT3), as one of the key proteins in EGFR downstream pathways, is persistently activated in over 50% of patients with NSCLC, and its increased expression is associated with poor tumor differentiation, advanced clinical stage, lymph node metastasis, and drug resistance [7,8,9,10,11,12].