Previously, both Snail and Slug have been shown to inhibit ERα expression through transcriptional repression.24, 51 Here, we report a different mechanism for Slug to repress ERα expression through recruiting LSD1 to the E-boxes of ESR1 promoter and demethylating H3K4me2 in ERα-negative breast cancers. The gene discussed is SNAI1; the disease is breast cancer.