Objective   To study the roles of Fas/FasL pathway in apoptosis of renal cell carcinoma (RCC) cells induced by 5-Fluorouracil (5-FU).     Methods   The effects of drug 5-FU in regulating the expressions of Fas and FasL in RCC cell line 786-0 and the effects of 5-FU

anti-Fas monoclonal antibody

CH11

and neutralizing anti-FasL monoclonal antibody NOK-2 on the apoptosis and proliferative activity of RCC cell line 786-0 were studied by Western blot

TUNEL

and MTT techniques.     Results   Expression of the protein products of Fas and FasL was found in human RCC cell line 786-0. The expressions of Fas and FasL peaked at 48 h after action of 5-FU at the concentration of 70  g/ml on RCC cells. Action of 5-FU on RCC 786-0 caused a decrease in cell proliferative activity and an increase of apoptotic cells. Action of anti-Fas monoclonal antibody CH11 on 786-0 increased apoptotic cells but decreased the proliferative activity. Combined action of CH11 and 5-FU on 786-0 could significantly inhibit the cell proliferation and induce cell apoptosis. No difference in apoptotic index and proliferative activity was found after blockage of the interaction between FasL and Fas by anti-FasL monoclonal antibody NOK-2.     Conclusion   5-FU may induce apoptosis of RCC cells

which may not be dependent on Fas/FasL pathway.