Transcription factor sine oculis homeobox 1 (SIX1) is a key regulator of organogenesis and tumorigenesis.[11, 12, 13, 14, 15, 16, 17] SIX1 is overexpressed in many cancers, such as hepatocellular carcinoma, breast cancer, colorectal cancer, and prostate cancer.[14, 15, 16] Increased expression of SIX1 predicts poor clinical outcomes. Here, SIX1 is linked to breast cancer.