SFN facilitates lysine-specific demethylase 1 (LSD1) ubiquitination and degradation in an HDAC5-dependent manner which inhibits breast cancer progression. Combining SFN with a potent LSD1 inhibitor results in synergistic growth inhibition in tumors with no impact on normal breast epithelial cells. Combining SFN and LSD1 inhibitors accelerates the inhibitory effect on MDA-MB-231 xenograft tumor growth. SFN enhances HDAC5-LSD1 axis inhibition and blocks breast cancer growth. This evidence concerns the gene SFN and breast cancer.