Figure 3. CircFOXK2 is required for BC metastasis. (A) Expressions of circFOXK2 and FOXK2 mRNA in BT-549 cells transfected with circFOXK2-expressing plasmids and the negative control. (B) Migration ability of circFOXK2-overexpressing BT-549 cells. Scale bar: 20 μm. (C) Invasion ability of circFOXK2-overexpressing BT-549 cells. Scale bar: 20 μm. (D) Lung metastasis of mice injected with circFOXK2-overexpressing BT-549 cells through the tail vein, as determined by H&E stain. Scale bar: 50 μm. (E) The expression of Ki67 in lung tissues of mice injected with circFOXK2-overexpressing BT-549 cells through the tail vein, as determined by IHC assay. Scale bar: 40 μm. (F) Expressions of circFOXK2 and FOXK2 mRNA in BT-549 cells transfected with circLONP2-specific anti-sense oligonucleotide (ASO). (G) Migration ability of circFOXK2-Knockdown BT-549 cells. Scale bar: 20 μm. (H) Invasion ability of circFOXK2-Knockdown BT-549 cells. Scale bar: 20 μm. (I) Lung metastasis of mice injected with circFOXK2-Knockdown BT-549 cells through the tail vein, as determined by H&E stain. Scale bar: 50 μm. (J) The expression of Ki67 in lung tissues of mice injected with circFOXK2-Knockdown BT-549 cells through the tail vein, as determined by IHC assay. Scale bar: 40 μm. Data were represented as mean ± SD. Each experimental group had at least three replicates. *p < 0.05, **p < 0.01, ***p < 0.001.