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 betwee n caveolin-1 status and clinical behavior. Caveolae have emerged as sites o f important regulatory events at the cell membrane in many different cell t ypes. Caveolins are the main structural components of caveolae and belong t o 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 immunoh istochemistry, we assessed caveolin-1 protein expression in 89 formalin-fix ed, paraffin-embedded bladder tumor sections. The patient group studied inc luded 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 caveo lin-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 caveo lin-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 o f caveolin-1 protein is a component of tumor dedifferentiation in a subset of high-grade bladder cancers. This pilot study provides a basis for furthe r investigation of the role of caveolin-1 and the function of caveolae in t he most aggressive forms of this tumor. (C) 2001, Elsevier Science Inc.