To verify whether USP26 induction by TGF‐β is prevalent in other cell types, we analyzed the induction of USP26 and SMAD7 at early time points in the TGF‐β‐responsive breast cancer cell lines MCF7, MDA‐MB‐231, T47D, and CAL51 and glioma cell lines U373, PCTC, and A172 (Fig EV4A–G). Here, TGFB1 is linked to breast carcinoma.