Claudins are the main protein components of
tight junctions (TJs) which function as selective barriers
by controlling paracellular diffusion, maintain cellular
polarity and play a role in signal transduction. The
expression pattern of the 24 known members of the
claudin family proved to be organ and tissue specific.
The up- or downregulation of individual claudins has
been described, especially during carcinogenesis. A
significant increase of claudins-1 and -7 was detected in
premalignant cervical lesions and invasive cancer
compared with normal cervical epithelia. Claudins-3 and
-4 were elevated in endometrial cancer. Claudin-1
overexpression characterized type II (seropapillary)
endometrial carcinoma, while claudin-2 was elevated in
type I (endometrioid) carcinoma. Claudins-3 and -4 were
highly expressed in serous ovarian carcinoma. The
expression data on claudins in different premalignant
and malignant alterations suggest that these proteins
might serve as diagnostic and prognostic markers and
might be targets for future therapy