Immunohistochemical analysis of bcl-2 protein expression in renal cell carcinoma

Purpose: To investigate the incidence, extent, and distribution of bcl-2 protein expression in human renal cell carcinomas. Materials and Methods: Using immunohistochemical tissue staining techniques, bcl-2 protein expression was analyzed in archival nephrectomy specimens removed for renal cell carcinoma or trauma and in 3 renal cell carcinoma cell lines. Results: Normal kidneys demonstrated bcl-2 immunopositivity primarily within the cytoplasm of distal tubule cells. Only rare and minor staining of the proximal tubular cells, thought to be the origin of renal cell carcinoma, was noted in histologically normal controls and areas adjacent to tumor. In contrast, bcl-2 protein expression was demonstrated in 70% of renal cell carcinomas and in all 3 experimental cell lines. Conclusions: Bcl-2 is a proto-oncogene known to regulate apoptosis (programmed cell death). Bcl-2 protein is overexpressed in the majority of renal cell carcinomas examined. Bcl-2 overexpression may have a role in tumorigenesis and may explain the relative resistance of renal cell carcinoma to chemotherapeutic agents and to radiation therapy.