Claudins as prognostic factors for renal cell cancer.

Claudins are tight junction proteins and their expression is often different in normal and corresponding tumor cells. In the present study, we determined how the expression of claudins 1-5 and 7 correlated to survival, grade and stage of patients with renal cell cancer (RCC). Primary tumor samples were collected retrospectively from 229 RCC patients. Claudins were detected by immunohistochemistry using commercial monoclonal antibodies against claudins 1-5 and 7. Median survival time was 6.5 years confidence interval (CI) (4.5-8.5, n=224). Kaplan-Meier survival estimated method was used in survival analyses. Positive expression was detected in 62%, 67%, 45%, 55%, 7% and 35% of cases for claudins 1, 2, 3, 4, 5 and 7, respectively. High expression of claudin 2 was observed in 20% of cases while high expression of other claudins was less frequent. Claudins were compared to classical prognostic factors. On cross-tabulation, claudin 1 (p<0.001) and claudin 2 (p=0.009) were significantly associated with lower-grade and higher-grade tumors, respectively. None of the claudins was significantly associated with tumor stage or patient survival. Claudins 1 and 2 were associated with tumor grade. However, none of the claudins was a more powerful prognostic factor than tumor stage.