Objective: Our purpose was to define the expression of tumor necrosis factor receptors on ovarian cancer cells and determine what role these receptors play in tumor necrosis factor-alpha-mediated cytolysis.
Study design: Cell surface expression of tumor necrosis factor-alpha receptors was determined on ovarian cancer cell lines Caov-3, SK-OV-3, NIH:OVCAR-3, and A2780 by a tumor necrosis factor-alpha-binding assay that used iodine 125-labeled tumor necrosis factor-alpha. Monoclonal antibodies specific for the 55 to 60 kd (TR60) and 75 to 80 kd (TR80) tumor necrosis factor receptors were used to determine the relative density of each receptor type. To elucidate which receptor(s) was responsible for mediating the signal for cytolysis, 24-hour MTT cytolytic assays that used tumor necrosis factor-alpha and emetine were performed in the presence or absence of receptor-specific monoclonal antibodies.
Results: The four ovarian cell lines expressed a similar number of surface receptors, 4500 to 7000 per cell, had similar dissociation constants, 0.3 to 0.6 nmol/L, and expressed predominately the TR60 receptor subtype. Receptor function studies showed that the presence of the monoclonal antibody to the TR60 receptor completely inhibited tumor necrosis factor-alpha-mediated cytolysis, whereas the monoclonal antibody to the TR80 receptor only partially blocked cytolysis.
Conclusions: Ovarian cancer cell lines express both tumor necrosis factor receptors, with the TR60 receptor being the dominant subtype. Tumor necrosis factor-alpha-mediated cytolysis appears to be dependent on the presence of a functional TR60 receptor. The TR80 receptor does not appear requisite for cytolysis; however, a complementary role cannot be excluded. Manipulation of tumor necrosis factor receptor subtypes on ovarian cancer cells may enhance the cytotoxic effects, thus improving the therapeutic efficacy of tumor necrosis factor-alpha.