TGFB1 and breast carcinoma: Isoform‐specific qRT–PCR showed that QKI‐5 mRNA is expressed at a much higher level than QKI‐6 and QKI‐7 in breast cancer and TGF‐β‐treated mammary epithelial cells (Fig EV3A–D), and immunoblotting confirmed QKI‐5 protein is much more abundant than the other isoforms (Fig 2A).