IL-2 enhances standard IFN gamma/LPS activation of macrophage cytotoxicityto human ovarian carcinoma in vitro: A potential for adoptive cellular immunotherapy

Objective. The objective was to evaluate the enhancement of human peritonea l macrophage cytotoxic in vitro activity by the addition of interleukin-2 ( IL-2) to the standard interferon gama (IFN gamma) and lipopolysaccharide (L PS) activation procedure used for cellular adoptive immunotherapy in a huma n ovarian cancer system. This cytotoxic effect of these activated macrophag es was tested on cells from ovarian cancers of various stages, histology ty pe, and grade, both prior to chemotherapy and at recurrence, in ovarian car cinoma cells lines and normal cells. Increased activation of the macrophage may make it a better candidate for intraperitoneal cellular adoptive immun otherapy as a component of ovarian cancer therapy. This was not a study of the mechanism of macrophage killing. Methods. Ascites specimens were collected from 24 ovarian cancer patients a t the time of surgery or by paracentesis. The mononuclear cell fraction was isolated by discontinuous density gradient centrifugation and used as a ce llular source of peritoneal macrophages (PMs) and primary cultured ovarian cancer cells. PMs were separated by 1-h adhesion followed by intensive wash ing to remove floating cells. The floating cells were cultured for 24 h whi ch left the cancer cells attached after unattached cells were removed by wa shing. These cells formed a monolayer of cancer cells, which could be subcu ltured in 22 patients. The cells from the third to fifth passages were used as target cells without coculture with other cells. PMs were identified by latex ingestion, and their purity after isolation by adhesion culture was tested by how cytometry and immunofluorescence. PMs were activated by cultu ring in the presence of IFN gamma, with or without IL-2, for 18 h followed by the addition of LPS 6 h prior to use as effector cells in cytotoxicity a ssays. Ovarian cancer cells of both established cell lines and primary cult ures were labeled with Cr-51 and utilized as target cells to quantitatively measure PM-mediated cytotoxicity. Ovarian cancer cells were also coculture d with PMs for morphologic observations to provide supporting evidence to t he cytotoxicity assays. Results. IL-2 enhances the cytotoxicity of the standard IFN gamma/LPS macro phage activation in this system. Peritoneal macrophages so activated are cy totoxic to autologous and allogenic primary cultured ovarian tumors and to ovarian carcinoma cell lines. The macrophages are cytotoxic to cells both p rior to treatment and at recurrence, but the data from the few recurrent pa tients did reach statistical significance. This cytotoxicity is not NMC ass ociated. Normal cells are minimally affected. Conclusions. IL-2 augmented the standard IFN gamma/LPS method of activating peritoneal macrophage cell killing of human ovarian cancer cells in this i n vitro system. The cell killing occurred with autologous and allogenic tum or cells from patients with primary and possibly recurrent tumors. Activate d PMs minimally affected the normal cells tested. This enhanced activation may improve the disappointing results of previous adoptive cellular immunot herapy human trials and should be considered for ovarian cancer clinical tr ials. (C) 1999 Academic Press.