This TGFβ2/Smads‐Snail1/EZH2‐miRNATGFβ2 feed‐forward circuitry is only operated in TNBC, not in luminal subtype BC because ERα interrupts this circuitry by interacting with Smads and blocking Snail1 expression in luminal subtype BC. Here, ESR1 is linked to breast cancer.