To understand the intrinsic epithelial or mesenchymal characteristics of IBC cells, we first quantified protein levels of epithelial marker E-cadherin and mesenchymal marker vimentin in IBC cell lines as well as in cell lines of other breast cancer subtypes: estrogen receptor-positive (ER+) and triple-negative breast cancer (TNBC) (Fig. 1A, Supplementary Figs S1, S2). This evidence concerns the gene ESR1 and breast cancer.