Abstract 1432: CXCL8 is a secretory inflammatory stimulus of the activated TME that modulates breast cancer phenotype.
Authors: George Andrea L. , Bednarczyk Robert , Rajoria Shilpi , Hanly Elyse , Suriano Robert , Mittelman Abraham , Tiwari Raj K. 
Published: August 2014

The tumor microenvironment (TME) is a heterogeneous niche consisting of numerous stromal cells, structural components, and secreted molecules from both the malignant and surrounding cells that contribute to tumor growth and progression. Importantly, these diverse types of secreted molecules can initiate crosstalk events between the tumor cells and TME. One such molecule, CXCL8/Interleukin-8 (IL-8), is a proinflammatory chemokine, primarily involved in neutrophil mobilization, which activates multiple cellular signaling pathways via the membrane associated G protein-coupled CXCL8 cognate receptors, CXCR1 and CXCR2. We hypothesized that IL-8, a ubiquitous inflammatory molecule that is secreted by macrophages, activated fibroblasts and mesenchymal cells, can alter breast cancer phenotype. To this end, using a cell culture model we analyzed both estrogen receptor (ER) positive and ER negative breast cancer cell lines T47D and MDA-MB-231 respectively that were found to express the CXCL8 receptors CXCR1 and CXCR2. The cellular source of IL-8 was from conditioned media (CM) from in vitro cultures of primary stromal cells including primary mesenchymal and fibroblast cells, as well as the established monocytic cell lines HL-60 and THP-1. Each cell line secreted adequate amounts of IL-8 as measured by ELISA, however primary mesenchymal cells produced four times that of the fibroblasts and macrophages suggesting that activated mesenchymal cells may be a very potent source of chronic inflammation in the TME. Interestingly, treatment with IL-8 or CM from the phorbol ester treated macrophages THP-1 led to increased proliferation in T47D in vitro however only IL-8 treatment led to proliferation of MDA-MB-231. Recombinant IL-8 as well as CM of THP-1 and mesenchymal cells enhanced migration and invasion of both T47D and MDA-MB-231 cells as evaluated by a modified Boyden chamber assay. Supplementation of the triple negative MDA-MB-231 line with THP-1 CM enhanced its invasive propensity nearly two fold. THP-1 CM treatment also led to the activation of the PI3K/p-Akt and Mek/Erk pathways in the ER− MDA-MB-231 cells but not the ER+ T47D cells suggesting a link between CXCL8 mediated inflammation and constitutive signal transduction pathways that is translatable into enhanced metastatic propensity. Our studies are directed towards the analysis of both chronic and acute inflammation of the TME and we believe IL-8 and its associated intracellular molecular markers may be important preventive and therapeutic targets in triple negative breast cancer.

Citation Format: Andrea L. George, Robert Bednarczyk, Shilpi Rajoria, Elyse Hanly, Robert Suriano, Abraham Mittelman, Raj K. Tiwari. CXCL8 is a secretory inflammatory stimulus of the activated TME that modulates breast cancer phenotype. [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 1432. doi:10.1158/1538-7445.AM2013-1432