PROGNOSTIC-SIGNIFICANCE OF SOLUBLE FAS IN THE SERUM OF PATIENTS WITH BLADDER-CANCER

Purpose: The interaction of Fas antigen (Fas) and Fas ligand plays an important role in cytotoxic T lymphocyte- and natural killer cell-medi ated cytotoxicity against cancer cells. Circulating soluble Fas (sFas) antagonizes cell-surface Fas function and may interfere with immune s urveillance against autologous tumors. This possibility was examined i n patients with bladder cancer. Materials and Methods: The levels of s Fas in the serum of 173 patients with bladder cancer were determined b y using an enzyme-linked immunosorbent assay. Cytotoxicity of anti-Fas monoclonal antibody was examined by a 1-day microculture tetrazolium dye assay. Anti-autologous tumor cytotoxic activity was determined by the 12-hour Cr-51 release assay. Results: The mean serum level of sFas in patients with bladder cancer was threefold higher than the mean in normal donors. The patients were divided into 2 groups based on the l evel of sFas in the serum. Bladder cancer patients with low level of s erum sFas (less than the mean value) had a higher disease-specific sur vival rate, when compared with those with high level of serum sFas (gr eater than the mean value) in the 5-year followup. There were no stati stical differences in patients' age and sex, as well as histological s tage and grade of bladder cancer between the patients with high and lo w levels of serum sFas. Furthermore, patients with Ta bladder cancer w ith a low level of serum sFas had a longer postoperative tumor-free in terval than those with high level in the 5-year followup. Cytotoxic ac tivity of peripheral blood lymphocytes against autologous tumor cells was examined in 25 patients. There was an inverse correlation between the level of serum sFas and anti-autologous tumor cytotoxicity. Conclu sions: The findings suggest that elevated levels of sFas in the serum might be associated with poor prognosis in patients with bladder cance r.