The STAT3 transcription factor plays a critical role in promoting BC metastasis by targeting genes that play a role in BC cell proliferation; survival and apoptosis inhibition (Bcl2, Bcl-xL, and survivin), angiogenesis (VEGF), invasion and metastasis (MMPs), EMT (Twist and Snail), inflammatory microenvironment that promote tumor growth and survival (IL-6) [15,16], and cellular response to hypoxia or low oxygen levels (HIF) [17]. This evidence concerns the gene SNAI1 and breast cancer.