Forced CircPTK2 expression was discovered to suppress the metastasis of lung cancer cells and downregulate TIF1γ expression by altering the EMT process and decreasing SNAIL expression, suggesting that circPTK2 suppresses TGF-β-triggered EMT and metastases through the modulation of TIF1γ in NSCLC. The gene discussed is SNAI1; the disease is lung carcinoma.