Abstract 4084: Crosstalk between TNBC and stromal components via secreted factors enhances cell motility that can be attenuated by a CXCR1 inhibitor

Triple negative breast cancer (TNBC) as a metastatic disease is currently incurable. Unfortunately reliable and reproducible methods for testing drugs against metastasis are not available. We have previously developed a robust metastatic model in which mice are pretreated with tumor cell-conditioned media (TCM) from human TNBC cells (MDA-MB-231 and SUM149) for 2 weeks prior to tumor cell inoculation. In this model we found reproducible metastases in lymph nodes (LN) and lungs within 4-5 weeks after orthotropic tumor inoculation. We have discovered that the TNBC tumor cells secrete large amounts of interleukin-6 (IL-6) that “educates” lymphatic endothelial cells (LEC) in the LN and lungs. Stat3, a transcription factor, gets activated and induces the synthesis of CCL5 and VEGF among other factors. CCL5 recruits the tumor cells to the LN and lungs; VEGF helps build blood vessels in the LN to facilitate tumor cell survival; VEGF produced in the lung helps the tumor cells extravasate into the lung. We have confirmed the importance of these factors by showing that inhibitors of these factors significantly inhibit metastasis. In this report, using a human antibody array, we identified factors secreted by fibroblasts (HGF, IL-6, IL-8, CCL7, MIF, GDF-15, EMMPRIN and VEGF) and by macrophages (CXCL5, IL-8 and uPAR) upon induction by MDA-MB-231 TCM. We ranked the expression level of each factor by real time qRT-PCR and determined that interleukin 8 (IL-8) was the top candidate. We confirmed by ELISA that IL-8 secreted from either fibroblasts or macrophages treated with MDA-MB-231 TCM was upregulated compared to treatment with serum free media (SFM). Our data showed that the proliferation of MDA-MB-231 cells incubated with conditioned media (CM) from TCM-induced fibroblasts or TCM-induced macrophages was enhanced compared to SFM treatment. Furthermore, MDA-MB-231 cell migration, a key step in tumor metastasis, was promoted by CM from TCM-induced fibroblasts or macrophages. Significantly, inhibition of the IL-8 signaling pathway by Reparixin, an inhibitor of the IL-8 receptor CXCR1, abrogated the upregulation of MDA-MB-231 cell proliferation and migration induced by TCM-induced fibroblasts or macrophages. These findings implicate IL-8 signaling as a critical event in TNBC cell proliferation and migration via crosstalk with stromal components. Further, these studies suggest that IL-8 acts as a key regulator orchestrating TNBC metastatic breast cancer. Therefore, we have provided evidence that supports the hypothesis that functional antagonism of the IL-8 signaling pathway has the potential to circumvent TNBC breast cancer growth and metastasis. Citation Format: Kideok Jin, Niranjan B. Pandey, Aleksander S. Popel. Crosstalk between TNBC and stromal components via secreted factors enhances cell motility that can be attenuated by a CXCR1 inhibitor. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4084.