Abstract 952: Modulation of Immune Cell Trafficking into Human Colorectal Cancer by Gut Microbiota

Abstract Introduction: Colorectal cancer (CRC) is a leading cause of cancer-related death. CRC infiltration by immune cells, including cytotoxic CD8+ T cells (CTLs), IFN-gamma-producing T-helper 1 cells (Th1), Foxp3+ regulatory T cells (Tregs) and CD16+ MPO+ neutrophils, is associated with favorable prognosis. However, chemokines driving these cell populations into the tumor site, their cellular sources and their microenvironmental triggers remain to be elucidated. Aim: We investigated the chemokine/chemokine receptor network promoting CRC infiltration by immune cells associated to favorable prognosis. Results: CRC infiltration by immune cells was associated with defined chemokine gene signatures, including CCL5, CXCL9 and CXCL10 for cytotoxic T lymphocytes and T-helper 1 cells, and CCL17, CCL22 and CXCL12 for T-helper 1 and regulatory T cells. Most of these chemokine genes were expressed by tumor cells upon exposure to gut bacteria in vitro and in vivo. Indeed, chemokine expression levels were significantly higher in orthotopic xenografts than in intraperitoneal tumors, and were drastically reduced by antibiotic treatment of tumor-bearing mice. Importantly, in human CRC samples, extents of chemokine production and immune cell infiltration was significantly associated with bacterial loads. Conclusion: Gut microbiota stimulates chemokine production by CRC cells, thus favoring T cell recruitment into tumor tissues. Note: This abstract was not presented at the meeting. Citation Format: Eleonora Cremonesi, Jesus G. Garzón, Valeria Governa, Valentina Mele, Francesca Amicarella, Elisabetta Padovan, Manuele Muraro, Paul Zajac, Daniel Oertli, Lubor Borsig, Giandomenica Iezzi. Modulation of immune cell trafficking into human colorectal cancer by gut microbiota [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 952. doi:10.1158/1538-7445.AM2017-952