We verified epithelial-like phenotype of luminal breast cancer cell lines BT474 and MCF-7 with regard to formation of compact spheroids after plating on ultra-low attachment (ULA) plates (Additional file 2: Figure S2a, S2b) and expression of epithelial markers (E-cadherin and EpCAM in both cell lines, and additionally cytokeratin 18 in MCF-7 (Additional file 3: Figure S3a). This evidence concerns the gene KRT18 and breast cancer.