CLDN4 and breast cancer: We found that breast cancer cells had a higher expression of epithelial markers (CLDN4, IMP3, MUC1, CDH1, CEACAM5, SCGB2A2, CLDN3 and CLDN7) that are associated with breast cancer,21 while mesothelial cell populations had a higher expression of known mesothelial markers (CALB2, WT1, UPK3B, CDH2, COL1A2, S100A4 and MSLN)21, 41, 42 (Figure 3C, ‘Epithelial’ and ‘Mesothelial’ markers).