Interferons alpha and gamma with monocytes as a therapeutic strategy for ovarian cancer.

Abstract

9 Background: In the presence of pro-inflammatory cytokines, monocytes are cytotoxic to tumor cells. We previously showed that monocytes stimulated with interferon alpha and gamma result in synergistic killing of ovarian cancer cells in vitro. Here we better characterize monocyte differentiation and their ability to induce cell death through co-culture experiments with spheroids and in mouse xenografts. Methods: OVCAR8 cells were grown in ultra-low attachment conditions for three days before being co-cultured with human monocytes as well as interferon gamma and interferon alpha. Monocytes and OVCAR8s were assayed by flow cytometry for markers of differentiation and viability, respectively. Mouse studies were performed to confirm the viability of human monocytes stimulated with interferon alpha and gamma within the peritoneal cavity seventy-two hours after injection. Subsequent mouse experiments analyzed monocyte differentiation towards M1 or M2 phenotypes by flow cytometry with or without exposure to tumor cells and/or interferons. Results: OVCAR8 spheroids showed decreased viability in the presence of monocytes combined with interferon. We show that monocytes also express a hybrid M1/M2 phenotype when stimulated to IFN and exposed to tumor cells. In mice, monocytes demonstrated a unique differentiation towards both M1 and M2 macrophages as well as plasmacytoid and classic DCs. Various immune cell subsets also differed when comparing peritoneal washes versus tissue digests. Mouse survival studies are ongoing. Conclusions: Monocytes with the combination of interferons alpha and gamma are effective at killing ovarian cancer cells in laboratory models. Phenotypic analyses show a novel pattern of differentiation markers. Our ongoing clinical trial with these agents will incorporate similar studies to correlate monocyte differentiation with anti-tumor activity.