Abstract 4138: Understanding the effects of NF-kappaB signaling on macrophage phenotype to inform therapeutic approaches

It is recognized that modulation of macrophage phenotypes within the tumor microenvironment has the potential to achieve anti-tumor outcomes. However, formulating a strategy to achieve the benefits of such an approach in a cell-specific manner while minimizing off-target or uncontrolled deleterious side effects remains a challenge. We hypothesize that modulation of Nuclear Factor Kappa-B (NF-kappaB) signaling within macrophages in the proximal tumor microenvironment represents an effective approach. However, there remains controversy whether NF-kappaB signaling in macrophages induces pro- or anti-tumor outcomes. Understanding the mechanisms by which this signaling pathway defines predominant macrophage characteristics is therefore critical in order to use strategic interventions to obtain therapeutic benefits. Our goal is to gain insight into how to modulate NF-kappaB signaling in macrophages to generate anti-tumor phenotypes and to use this information to develop new treatments. We use immortalized bone marrow-derived macrophages or ex vivo macrophages in cell culture approaches to investigate impacts of modulation of NF-kappaB signaling on macrophage phenotypes. We have three methods to modulate signaling: doxycycline inducible transgenic mice, liposomal delivery of the bacterial cell mimic MTP-PE, and optimized polymeric nanoparticle-mediated delivery of siRNA targeting the NF-kappaB inhibitor. In addition to our in vitro assays, we also employ in vivo murine models of ovarian and breast tumor progression. This multi-faceted approach is providing insights into how altering NF-kappaB signaling in macrophages impacts their interactions with tumor cells and other cells in the tumor microenvironment. Our data suggests that high levels of NF-kappaB signaling in macrophages induce both direct tumor cell-killing and immune-stimulating responses. These studies are designed to better understand the mechanisms by which NF-kappaB regulates macrophage functions to inform development of a novel macrophage-based immunotherapy that will be effective across a wide spectrum of solid tumors and metastatic disease. Citation Format: Evan B. Glass, Alyssa Hoover, Whitney Harris, Zahra Mirafzali, Todd D. Giorgio, Andrew Wilson, Fiona Yull. Understanding the effects of NF-kappaB signaling on macrophage phenotype to inform therapeutic approaches [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4138.