CLDN2 and cancer: The claudin-low subtype is characterized by a high expression of mesenchymal markers, immune response genes (lymphocytes and endothelial cell markers) and cancer stem cell-like features, and a low expression of luminal genes, proliferation-related genes, genes involved in tight junctions and epithelial cell-adhesion (claudins 2, 4, 7, occludin and E-cadherin) [30,31,32,33].