UC Irvine

We have demonstrated the presence of the 55- and 75-kDa receptor for tumor necrosis factor (TNF) and lymphotoxin (LT) (TNF-R) in serum, and ascites from women with ovarian cancer. The present studies were initiated to begin to examine the possible cellular source of these receptors in women with ovarian cancer. Human ovarian tumor cells (PA-1) were cocultured for 24-48 hr with various levels of recombinant human cytokines (IL-1 beta, IL-4, IFN-gamma) and the supernatants were assayed by ELISA for the soluble forms of each receptor. PA-1 cells spontaneously release the 55-kDa TNF-R and low levels of the 75-kDa TNF-R. The release of both 55- and 75-kDa TNF-R was stimulated when PA-1 cells were cultured with IL-1 beta and IFN-gamma but unaffected by IL-4. The level of 55-kDa TNF-R was elevated slightly over spontaneous release but the level of 75-kDa TNF-R increased dramatically. IFN-gamma was the most potent stimulator of receptor release particularly of the 75-kDa TNF-R. IFN-gamma also induced increased expression of cell membrane TNF-R measured by binding of 125I-labeled TNF. Membrane TNF-Rs which were induced by IFN-gamma were the 75-kDa type, because TNF binding was blocked by anti-75-kDa TNF-R antibody. These data suggest that IFN-gamma selectively induced release and expression of 75-kDa TNF-Rs.