Interferon-gamma and tumor necrosis factor-alpha induce synergistic cytolytic effects in ovarian cancer cell lines - Roles of the TR60 and TR80 tumornecrosis factor receptors

Objective. Utilizing ovarian cancer cell lines, we examined the effect of I FN-gamma on each type of TNF receptor. Additionally, we sought to determine the effect of receptor modulation on TNF-alpha-mediated cytolysis. Methods. Ovarian cancer cell lines Caov-3, A2780, and SK-OV-3 were employed . The number of TNF receptors was determined by a TNF-alpha binding assay u tilizing I-125-labeled TNF-alpha. Monoclonal antibodies specific for the 55 - to 60-kDa (TR60) and the 75- to 80-kDa (TR80) TNF receptors were used to determine the relative density of each receptor type. Northern blot analyse s were performed employing cDNA probes for the TR60 and TR80 mRNAs. To eluc idate which receptor(s) was responsible for mediating the signal for cytoly sis, 24-h MTT cytolytic assays were performed in the presence of receptor-s pecific monoclonal antibodies. Results. IFN-gamma treatment resulted in an increase in TNF receptors in th e cell lines A2780 and Caov-3 (P < 0.001), but not SK-OV-3. Northern blot a nalyses suggested distinct regulatory mechanisms for the two receptors. In Caov-3 and SK-OV-3 cells a synergistic increase in TNF-alpha-mediated cytol ysis was seen when cells were pretreated with IFN-gamma. In both cell lines , pretreatment with IFN-gamma markedly enhanced the ability of the TR60 rec eptor to mediate cell lysis. Conversely, under similar treatment conditions , the TR80 receptor did not appear capable of generating a cytolytic signal . Conclusions. TNF receptor modulation by IFN-gamma appears to be unique to i ndividual cell lines. The TR60 TNF receptor plays a central role in the syn ergistic cytolytic effects of IFN-gamma and TNF-alpha. Sequential therapy w ith IFN-gamma and TNF-alpha and specific TNF receptor activation may provid e novel translational strategies for the use of cytokines in the treatment of ovarian cancer. (C) 1999 Academic Press.