INTERLEUKIN-12-MEDIATED TUMORICIDAL ACTIVITY OF PATIENT LYMPHOCYTES IN AN AUTOLOGOUS IN-VITRO OVARIAN-CANCER ASSAY SYSTEM

This study was designed to examine if interleukin-12 (IL-12) can induc e cytolytic function of lymphocytes from ovarian cancer patients again st either an ovarian cancer cell line or their own autologous tumor ce lls. Lymphocytes were obtained from the peripheral blood or ascites of ovarian cancer patients and activated with IL-12 alone or concomitant ly with interleukin 2 (IL-2) for 2 to 3 days, Activation of lymphocyte s and assessment of tumoricidal function by a chromium release assay w ere performed directly in a standard control medium (RPMI 1640 contain ing 2 mM glutamine, 100 mu g/ml streptomycin, 100 units penicillin, 5% heat-inactivated human AB serum, and 5 mM 4-(2-hydroxyethyl)-1-pipera zinesulfonic acid) and in 50% ascitic fluid (50% by volume filter-ster ilized ascites with 50% of the above-mentioned control medium). Target cells were added directly into the medium in which the lymphocytes we re activated in order to more closely mimic in vivo conditions. Lympho cytes, activated by IL-12 in 50% ascitic fluid, were able to lyse auto logous tumor cells in 3 of 6 assays and were able to lyse SKOV3 cells (an ovarian cancer cell line) in 5 of 7 assays. The results were not s ignificantly different in the control medium. When both IL-2 and IL-12 were used to activate lymphocytes in 50% ascitic fluid, significant c ytotoxicity was generated in 6 of 6 autologous assays and in all 7 pat ient assays using SKOV3 as a target (P < 0.05), Synergy between the tw o cytokines was seen in all 13 patient assays in ascitic medium compar ed to only 5 of 13 assays in control medium. Additionally, when lympho cytes were stimulated with both IL-2 and IL-12, significantly greater cytotoxicity was seen in the ascitic fluid medium compared to the cont rol medium in 13 of 14 assays (P < 0.05). No significant tumoricidal a ctivity was seen by lymphocytes maintained in either medium without th e addition of IL-2 or IL-12. Ascitic fluid consistently potentiates th e synergy between IL-2 and IL-12 in generating cytotoxicity against ov arian cancer cells but does not increase cytotoxicity induced by IL-12 alone. IL-12 by itself activates tumoricidal activity of lymphocytes in ascitic fluid; however, the addition of IL-2 increases the degree a nd consistency of this effect. These data support the possibility that IL-12 may warrant further investigation as a potential therapeutic ag ent in the treatment of advanced ovarian cancer. (C) 1995 Academic Pre ss, Inc.