Claudin 3 monoclonal antibody

Tight junctions, or zonula occludens, form a continuous barrier to fluids across the epithelium and endothelium. They function in regulation of paracellular permeability and in the maintenance of cell polarity, blocking the movement of transmembrane proteins between the apical and the basolateral cell surfaces. Tight junctions are composed of claudin and occludin proteins, which join the junctions to the cytoskeleton. The claudin family is composed of 23 integral membrane proteins, and their expression, which varies among tissue types, may determine both the strength and properties of the epithelial barrier. Alteration in claudin protein expression pattern is associated with several types of cancer. Claudin-1 is expressed primarily in keratinocytes and normal mammary epithelial cells, but is absent or reduced in breast carcinomas and breast cancer cell lines.

Claudin-3 is the product of an intronless gene (CLDN3) whose expression is markedly dysregulated in distinct cancer subtypes, including ovarian and breast carcinomas. Somewhat paradoxically, reduced claudin-3 expression is also a hallmark of a subset of breast tumors known as the claudin-low subtype, in which reduced claudin-3 expression was shown to correlate with a phenotype characteristic of cells undergoing epithelial-mesenchymal transition.