Abstract LB-346: The Oxysterol-CXCR2 axis plays a key role in the recruitment of tumor promoting neutrophils. (2013)

Abstract Tumor formation depends on molecular alterations responsible for neoplastic transformation of normal cells, as well as on the ability of tumor cells to co-opt inflammatory/immune cells to create a tumor growth-permissive microenvironment. Targeted therapies inhibiting molecular alterations in tumor cells have improved antitumor responses. However, overall survival has been enhanced only slightly. Tumor-infiltrating immune cells can be conditioned by molecules released within the microenvironment to thwart antitumor immune responses. Among immune cells, neutrophils are recognized as playing an important pro-tumorigenic role, by favoring neoangiogenesis and/or by suppressing antitumor immune responses. We have recently shown that tumor-derived Liver X Receptor (LXR) ligands/oxysterols, known to be involved in cholesterol homeostasis and in modulating physiologic immune responses, favor tumor growth by inhibiting dendritic cell migration towards lymphoid organs. Here, we identify an unanticipated function of tumor-derived LXR ligands/oxysterols, which contribute to the recruitment of neutrophils within tumor microenvironment in an LXR-independent, CXCR2-dependent manner, ultimately favoring tumor growth. In particular, we show a continuous recruitment of neutrophils in oxysterol-releasing tumors, as evaluated by parabiosis experiments. We demonstrate by mass spectrometry and high-performance liquid chromatography analyses that the lymphoma RMA, the Lewis Lung Carcinoma (LLC) and the mesothelioma AB1 produce some oxysterols (22R-HC, 27-HC and 24S-HC), which are able to induce CD11b+Ly6G+ neutrophil migration in vitro and in vivo. Neutrophil migration is independent of LXR signaling both in vitro and in vivo, as demonstrated by using Lxrαβ-/- mice, while it depends on the oxysterol-CXCR2 interaction, as evaluated in vitro by migration experiments with Cxcr2-/- neutrophils, GTPγS binding assays, measurements of cAMP levels, and, in vivo by tumor challenge experiments in Cxcr2-/- bone marrow chimera mice. Tumor-recruited neutrophils are then able to favor tumor growth by promoting neoangiogenesis or immunosuppression of antitumor responses. Furthermore, we demonstrate that RMA, LLC and AB1 tumors engineered to express the oxysterol-inactivating enzyme sulfotransferase 2B1b (SULT2B1b), show a reduced number of tumor-infiltrating neutrophils as well as of CD31+CD45- endothelial cells, as compared to mock-expressing tumors. This reduction parallels tumor growth delay and prolonged survival of SULT2B1b-tumor-bearing mice. Antitumor responses are also obtained with genetic or pharmacologic inactivation of CXCR2, the latter mediated by the CXCR2 antagonist SB225002. These results, along with the observation that some human tumors release oxysterols, identify an unanticipated pro-tumor function of the oxysterol-CXCR2 axis and a possible new target for cancer therapy. Citation Format: Vincenzo Russo, Laura Raccosta, Raffaella Fontana, Daniela Maggioni, Claudia Lanterna, Aida Paniccia, Andrea Musumeci, Claudio Doglioni, Andrea Leiva, Eduardo J. Villablanca, Rodrigo Mora, Elena Chiricozzi, Maria Grazia Ciampa, Laura Mauri, Alessandro Prinetti, Sandro Sonino, Maria Letizia Trincavelli, Simona Daniele, Claudia Martini, Knut Steffensen, Jan-Ake Gustafsson, Safiyè Gozalvo Feo, Claudio Bordignon, Catia Traversari, Silvano Sozzani. The Oxysterol-CXCR2 axis plays a key role in the recruitment of tumor promoting neutrophils. [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 LB-346. doi:10.1158/1538-7445.AM2013-LB-346