Fig. 1

A Schematic view of the claudins in the TJ. The claudins are located at the membranes, narrowing the TJs, thereby increasing barrier function. B Epithelial cell-to-cell contact, where claudins are located at the membranes. In non-tumorigenic tissues, the TJ is intact between the cells, meaning there is controlled paracellular transport of nutrients and growth factors. When there is a loss of TJ activity, such as that seen in tumorigenesis, the barrier weakens, allowing for more liberal paracellular transport of nutrients and growth factors [6, 7, 11]