CCNE2 and breast cancer: Seven candidate genes expressed significantly higher in breast cancer compared to its adjacent breast tissues, based on the TCGA database (p < 0.05) (Figure 4A), this is consistent with the immunohistochemical results from the Human Protein Atlas database (HPA) database, indicating that the expression of CCNE2, CDCA5, RAD51, KNTC1, and MCM10 in breast cancer tissues was higher than in normal breast tissues (Figure 4B).