TNBCs are enriched in basal-like (BLBC) and claudin-low breast cancer molecular subtypes, the former expressing basal cell markers and the latter, in addition to low claudin 3, 4, 7 and E-cadherin expression, showing induced expression of EMT (epithelial-to-mesenchymal transition)-related genes, immune system-related genes and stem-cell features [18, 19]. Here, CLDN3 is linked to breast cancer.