STAT3 and lung cancer: TGF-β can also function through non-Smad (Figure 1) pathways to modulate lung cancer EMT, such as the nuclear factor-kappa B (NF-κB)/Snail [37], Janus-activated kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) [38], phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT), and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase 1/2 (ERK1/2) [39] pathways.