Caveolin-1 expression is associated with high-grade bladder cancer.

OBJECTIVES: To assess the levels of caveolin-1 in a series of bladder tumor specimens of varying stage and grade and to identify possible links between caveolin-1 status and clinical behavior. Caveolae have emerged as sites of important regulatory events at the cell membrane in many different cell types. Caveolins are the main structural components of caveolae and belong to a family of highly conserved integral membrane proteins. The function of caveolin-1 appears to be intrinsically linked to cell signaling modulation by multiple pathways. Modification of CAV-1 gene expression appears to be a common feature of the oncogenically transformed phenotype.
METHODS: Using a rabbit polyclonal antibody against caveolin-1 and immunohistochemistry, we assessed caveolin-1 protein expression in 89 formalin-fixed, paraffin-embedded bladder tumor sections. The patient group studied included 71 men and 18 women (mean age +/- SD 69.7 +/- 10.9 years). The stage was Ta-T1 in 68 and T2-T4 in 21 tumors in this series. The clinical follow-up was 1 to 38 months (mean 21.2 +/- 9.9).
RESULTS: A statistically significant association was observed between caveolin-1 immunoreactivity and tumor grade (P = 0.0118, chi-square test), with 8 (21%) of 38 G3, 1 (3%) of 30 G2, and 0 of 21 G1 tumors positive for caveolin-1. When the clinical data were examined in conjunction with caveolin-1 status, no statistically significant relationship was seen between caveolin-1 expression and tumor multiplicity, tumor recurrence, tumor progression, or patient survival.
CONCLUSIONS: The results of our study demonstrate that altered expression of caveolin-1 protein is a component of tumor dedifferentiation in a subset of high-grade bladder cancers. This pilot study provides a basis for further investigation of the role of caveolin-1 and the function of caveolae in the most aggressive forms of this tumor.