After confirming that SFRP1 was highly expressed in breast cancer, we further explored the SFRP1 promoter methylation level, and the results showed that SFRP1 was hypermethylation in breast cancer (Supplementary Figure 6A), regardless of individual cancer stages (Supplementary Figure 6B), race (Supplementary Figure 6C), nodal metastasis status (Supplementary Figure 6D), tumor histology (Supplementary Figure 6E), major subclasses (Supplementary Figure 6F), menopause status (Supplementary Figure 6G), and TP53 mutation status (Supplementary Figure 6H). Here, SFRP1 is linked to cancer.