We found that the fluorescence intensities in the lungs were much weaker in the downregulated circFOXK2 expression group than in the NC group, and adding FOXK2-142aa overexpression plasmid reversed these findings, suggesting that circFOXK2 also promoted lung metastasis of HCC cells via encoding FOXK2-142aa (Supplemental Fig. 4A). Here, FOXK2 is linked to hepatocellular carcinoma.