Fas labeling status does not correlate with apoptosis of renal cell carcinoma in vivo.

ABSTRACT

BACKGROUND: Contribution of the Fas system to apoptosis of renal cell carcinoma (RCC) was investigated in vivo. MATERIALS AND METHODS: Tissues from 30 RCC cases were immunostained for Fas and Fas ligand (FasL) to assess associations between Fas labeling status of RCC, indices of FasL-positive tumor-infiltrating mononuclear cells (FasL-TIM) and apoptotic indices (AI) of RCC. RESULTS: In all cases, tumor cells co-expressed Fas and FasL; strongly and diffusely in 13 cases (43%) and weakly in 17 (57%). Despite the constitutive co-expression of Fas and FasL, AI was low in most cases (median, 7 per 1,000 tumor cells; range, 1 to 257). The Fas labeling status did not significantly associate with AI while FasL-TIM index positively correlated with AI. CONCLUSION: These results suggest that the Fas system is not the principal mechanism of apoptosis of RCC while activated tumor-infiltrating mononuclear cells induce apoptosis via mechanisms other than the Fas system.