To verify the pro‐metastatic role of SIX‐1 in BC, we overexpressed SIX‐1 via lentivirus infection in MCF‐7 (MCF‐7‐SIX‐1‐OE), a BC cell line with low metastatic potential and knockdown SIX‐1 via lentivirus infection in MDA‐MB‐231 (MDA‐MB‐231‐SIX‐1‐Sh), a BC cell line with high metastatic potential,27 for further investigation (Figure 2A,B). This evidence concerns the gene SIX1 and infection.