REDUCTION OF TUMOR-NECROSIS-FACTOR-ALPHA BIOACTIVITY BY A HUMAN OVARIAN EPITHELIAL CANCER CELL-LINE IN-VITRO

OBJECTIVE: Our purpose was to determine the ability of an ovarian epit helial carcinoma cell line, Caov-3, to alter the bioactivity of exogen ously added tumor necrosis factor-alpha. STUDY DESIGN: Caov-3 cells we re cultured for up to 6 days in Dulbecco's modified Eagle's medium con taining 10% fetal calf serum. The control and tumor necrosis factor-al pha-treated cells were analyzed for proliferation, distribution throug hout the cell cycle by flow cytometry, their ability to release bioact ive tumor necrosis factor-alpha by L929 bioassay, and their ability to release immunoreactive tumor necrosis factor-alpha by a specific doub le sandwich enzyme-linked immunosorbent assay. RESULTS: Tumor necrosis factor-alpha induced a dose- and time-dependent inhibition of cell pr oliferation accompanied by accumulation of cells in late S and G(2)/M phases of the cell cycle. Tumor necrosis factor-a bioactivity was unde tectable in the media of control Caov-3 cell cultures, but these cells exhibited TNF-alpha messenger ribonucleic acid. After culture of the cells for 2 days in the presence of various doses of TNF-alpha (0.1, 1 .0, 10, or 100 ng/ml), a significant decline (p < 0.01) in bioactivity was observed in all groups with the exception of 100 ng of TNF-alpha. Further declines in bioactivity were observed 2 and 4 days later. Add ition of TNF-alpha to Caotr-3 cells did not affect its immunoactivity, and Western blots of media revealed major bands of immunoactivity at similar to 17 kd, the expected molecular size of TNF-alpha. CONCLUSION : These results indicate that Caov-3 ovarian carcinoma cells reduce th e bioactivity of TNF-alpha, an important growth regulator, by a novel yet unknown mechanism to escape the modulatory effects of the normal i mmune response during cancer cell growth.