Claudins are in contact with scaffolding proteins like ZO-1, ZO-2 and ZO-3 and through them with the cellular cytoskeleton [102] . ZO-1 has been shown to recruit the transcriptional factor ZONAB from cytoplasm thus preventing its movement to the nucleus where it promotes cell proliferation. ZO-2, on the other hand, is able to bind AP-1 [103] . How the expression of different claudins influences the functions of such zona occludens proteins is not known but it is possible that in cancer cells the relation between claudins and zona occludens and other scaffolding proteins is deranged leading to a dysregulation of transcription factors such as ZONAB or AP-1. Clearly more research is needed to understand the functions and consequences of claudin expression in lung cancer.