Specific examples include increased expression of claudin-3 and -4 in types of prostate and uterine cancer (13,14), high claudin-4 expression in pancreatic cancer (15), downregulation of claudin-7 in head and neck (16) and metastatic breast (17) cancer, and an increase in claudin-3 and -4 in breast cancer (18). Here, CLDN3 is linked to cancer.