ZEB1 and breast cancer: To reduce dimensionality and visualize trends in the data, we stratified tumor composition into 3 cohorts (>1%, 0.01–0.99%, <0.01%) and performed principal component analysis (PCA) on the 9 variables that we had measured (CK8, CK14, Zeb1, EpCAM, MHC-I, PD-L1, proliferation rate, in vitro fold change in contribution to the BC Pool, and in vivo fold change in contribution during tumor progression) (Supplementary Table 9).