Objectives. To investigate cell proliferation, apoptosis, and bcl-2 immunoreactivity in renal cell carcinoma (RCC).

Methods. Formalin-fixed and paraffin-embedded tissue blocks from 70 patients with RCC were studied. Cell proliferation activity was detected by Ki-67 immunostaining and the proliferation index (PI) was expressed as a percentage of the Ki-67-positive cells in the tumor cells. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), and the apoptotic index (AI) was expressed as a percentage of the TUNEL-positive cells in the tumor cells. Immunoreactivity of bcl-2 was assessed immunohistochemically and coexpression of Ki-67 with bcl-2 was examined by double immunostaining.

Results. The PI ranged from 5.0% to 44.0% (median 19.23%) and the AI from 0.9% to 3.4% (median 2.13%) in RCC. Statistical analysis revealed close associations between PI and tumor grade and stage, and a significant relationship between AI and the tumor grade of RCC. The expression of bcl-2 was detected in 24 (34.3%) of 70 RCCs. Coexpression of Ki-67 with bcl-2 was noted in 3 of the 24 RCCs with bcl-2 expression. The expression of bcl-2 was not related to PI, AI, or the clinicopathologic factors of RCC.

Conclusions. Our observations suggest that active cell proliferation may be accompanied by frequent apoptosis and that cell proliferation as reflected by Ki-67 staining may be the most important parameter of cell turnover in RCC.