Abstract 2875: NF-κB signaling in myeloid cells limits urethane-induced lung tumorigenesis.

Abstract

Abstract The transcription factor Nuclear Factor κB (NF-κB) is a master regulator of inflammation, and its activation is associated with tumorigenesis in a variety of cancers. Our group has shown that NF-κB signaling in lung epithelial cells is critical for lung tumor formation. However, the role of NF-κB in other cell types, such as myeloid cells, during lung carcinogenesis is uncertain. We hypothesized that NF-κB signaling in myeloid cells (macrophages, monocytes, and neutrophils) promotes lung tumorigenesis by facilitating lung inflammation. Surprisingly, we found that mice with myeloid cell-targeted IKKβ deletion (IKKβΔmye mice) developed significantly more tumors than wild-type (WT) mice 4 months following a single intraperitoneal (IP) injection of the lung carcinogen urethane (1g/kg). IKKβΔmye mice exhibited a paradoxical increase in the proinflammatory cytokines IL-1β, TNFα, and CXCL1 at 1 and 2 weeks after urethane treatment, and a more than 3-fold higher influx of CD11b+Ly-6G+ cells into IKKβΔmye lungs compared to WT lungs was observed by flow cytometry 1 week post-urethane. By 6 weeks after urethane, IKKβΔmye mice developed more lung inflammation than WT mice, which was accompanied by an increased burden of atypical adenomatous hyperplasia lesions. Flow cytometric analysis of inflammatory cell populations at this time point revealed a sustained increase in granulocytic cells, indicated by significantly higher numbers of CD11b+Gr-1hi cells in the lungs of IKKβΔmye mice compared to WT mice. Depletion of granulocytic cells using Ly-6G antibody treatment (50ug/weekly IP injection) during the first 6 weeks of urethane-induced lung carcinogenesis reduced lung NF-κB activation and lung tumor incidence in IKKβΔmye mice to levels observed in urethane-treated WT mice, indicating that granulocytic cells play an important role in lung tumorigenesis during early tumor development and may do so by limiting NF-κB activation in lung epithelial cells. Together, our data suggest that the impact of NF-κB signaling on lung tumorigenesis is cell type specific and that myeloid NF-κB signaling limits urethane-induced inflammation and lung tumorigenesis. Granulocytes are important players during early lung tumor promotion, and we propose that they promote lung carcinogenesis through interactions that increase survival and/or proliferation of mutated lung epithelial cells. Citation Format: Allyson McLoed, Rinat Zaynagetdinov, Taylor Sherrill, Fiona Yull, Timothy Blackwell. NF-κB signaling in myeloid cells limits urethane-induced lung tumorigenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2875. doi:10.1158/1538-7445.AM2013-2875