These nine cell lines (MDA-MB-435, MDA-MB-436, Hs578T, BT549, MDA-MB-231, MDA-MB-157, SUM1315MO2, SUM159PT and HBL100) showed a gene expression pattern similar to the claudin-low tumor subtype with the lowest expression of genes involved in epithelial cell-cell adhesion (i.e., E-cadherin and claudins 3, 4 and 7), luminal differentiation (i.e., CD24, EpCAM) and high values for the CD44/CD24 and CD49f/EpCAM mRNA ratios (Figure S4, Table S3 in Additional file 1). This evidence concerns the gene CD44 and neoplasm.