Impact of caveolin-1 expression on clinicopathological parameters in renal cell carcinoma

Purpose: Caveolin-1 is a major structural component of caveolae, which are plasma membrane microdomains implicated in the regulation of intracellular signaling pathways. Previous studies of the expression and function of caveolin-1 in cancer have shown controversial results, indicating that the physiological role of caveolin-1 varies according to cancer type. We evaluated caveolin-1 expression in renal cell carcinoma and investigated its association with pathological features and clinical outcome. Materials and Methods: Caveolin-1 expression was evaluated by immunohistochemistry using rabbit polyclonal antibody against caveolin-1 in 60 paraffin embedded primary renal cell carcinoma specimens and 6 metastatic renal cell carcinoma specimens. When more than 50% of all cancer cell cytoplasm stained, the tumor was considered caveolin-1 positive. Associations between caveolin-1 expression, and pathological features and clinical outcomes were analyzed. Results: Of 60 primary tumors 16 (26.7%) and 5 of 6 metastatic tumors (83.3%) were immunoreactive in more than 50% of cancer cells and considered caveolin-1 positive. Although no significant associations between caveolin-1 expression, pathological stage (T stage) and distant metastasis at initial presentation were observed, significant associations between positive caveolin-1 expression and high grade tumor (p = 0.0009) and regional lymph node metastasis at initial presentation (p = 0.0049) and venous invasion (p = 0.0195) were observed. There was no difference in cancer specific survival between caveolin-1 positive and negative groups. However, in 43 patients without metastasis to regional lymph nodes or a distant site at initial presentation (N0M0) the caveolin-1 positive group had significantly shorter progression-free survival than the caveolin-1 negative group (p = 0.0332). Conclusions: Caveolin-1 over expression could be a common finding in aggressive forms of renal cell carcinoma. Caveolin-1 might have an important role in the invasion and metastatic progression of renal cell carcinoma.