Immunohistochemical expression of caveolin-1 as a marker for the biological potential of renal cell carcinoma

H Sakai, MD, K Takehara, MD, S Koga, MD, H Kanetake, MD

Department of Urology, Nagasaki University School of Medicine, Nagasaki, Japan

AIM: Caveolin-1 is a principal component of caveolae membranes. It has been suggested that caveolin-1 may act a general kinase inhibitor. The aim of this study was to assess the cellular expression of caveolin-1 and correlate the expression with clinicopathological variables in patients with renal cell carcinoma. METHODS: Formalin-fixed, paraffin-embedded nephrectomy specimens from 52 patients with renal cell carcinoma were stained immunohistochemically with polyclonal anti-caveolin-1 antibody. The relationship between caveolin-1 expression and various clinicopathological factors was examined by chi-square test or Fisher's exact test. RESULTS: Immunohistochemical analysis revealed cytoplasmic expression of caveolin-1 in normal kidney tubules with abundant staining of endothelial cells. Of the 52 primary tumor specimens, caveolin-1 expression was recognized in 20 cases (38%), and the expression varied in localization from only the cell membrane to the whole cytoplasm. The cytoplasmic caveolin-1 expression level, which was observed in 12 cases (23%), was significantly associated with the histological grade (p<0.05), tumor size (p<0.01), and clinical stage (p<0.05). Cytoplasmic expression of caveolin-1 was also observed in all three metastatic lesions, although one of the primary sites was negative for staining. CONCLUSIONS: This is the first study of caveolin-1 expression in human malignant kidney tumors. Our results suggest that caveolin-1 protein may play an important role in the progression of renal cell carcinoma.

KEY WORDS: Kidney neoplasms, Membrane protein, Immunohistochemistry, Disease progression.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Predictive Markers.