KRT18 and breast cancer: Besides activation of the motility-related pathways, the subset of LumA tumors presenting high ID4 expression also shows a reduced expression of the luminal commitment factors Foxa1, GATA3, BRCA1, KRT18, KRT8, and KRT19 compared to the portion of LumA expressing low ID4 (Fig. 1E), further confirming the negative association between ID4 and BC cell differentiation.