Strong claudin 5 expression is a poor prognostic sign in pancreatic adenocarcinoma

We investigated the expression of claudin 5 in 88 ductal adenocarcinomas of the pancreas. The results were correlated with patient prognosis, with claudin 5 expression in blood vessels, with the expression level of bcl2 and bax and with apoptosis. Claudin 5 expression was detected in 24 (38 %) cases. It was not associated with tumour size or spread, but strong claudin 5 expression correlated with a worse survival (p = 0.005). Claudin 5 also associated with a higher extent of apoptosis and greater expression of bax protein. In the tumour vasculature, some vessels displayed a loss of claudin 5 expression. The presence of this loss was associated with tumour grade and the presence of nodal metastases (p = 0.02, p = 0.022, respectively). These results indicate that claudin 5 is upregulated in a proportion of pancreatic ductal adenocarcinomas. The association of strong claudin 5 expression with a worse survival is in line with some earlier reports indicating that this protein is involved with increased locomotion and more aggressive spread of carcinomas. The association of claudin 5 with apoptosis and bax might be due to stronger cellular kinetics found in such tumours. The loss of claudin 5 expression in the tumour vasculature points to a leaky vessel type; this might also ease the access of tumours to vessels and be reflected in its association with the presence of nodal metastases.