Figure 5 Troponin C1, slow skeletal and cardiac type (TNNC1) promoted autophagy of A549 cells and affected gemcitabine (GEM) sensitivity, which was negatively transcription regulated by forkhead box 03 (FOXO3). A549-overexpressed TNNC1-stable cells were transfected with FOXO3 overexpression plasmid (TNNC1+FOXO3) for 48 h, whereas A549-overexpressed TNNC1-stable cells (TNNC1) were used as controls. At the same time, A549/GemR cells were transfected with TNNC1 short interfering ribonucleic acid (siRNA) (siTNNC1) or TNNC1 siRNA plus FOXO3 siRNA (siTNNC1+siFOXO3) respectively for 48 h. Meanwhile, GEM was incubated for 24 h before testing. (A, B) Cell proliferation of A549 and A549/GemR was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The data were presented as the mean±SD (*** P<0.001). (C) Autophagy-related proteins LC3B and P62 were detected by western blot. (D) Apoptosis was investigated by flow cytometry. (E) GFP-LC3 punctate structures were observed and imaged using a fluorescence microscope in A549 and A549/GemR model cells after AAv-mRFP-GFP-LC3 viruses infected them. The original magnification was ×200.