Abstract 1494: Intrinsic and extrinsic TME factors modulate breast cancer progression

Abstract

Abstract The tumor microenvironment (TME) of breast cancer is a heterogeneous population of tumor cells, infiltrating endothelial cells, immunomodulatory cells, and underlying stroma. This cellular cross-talk is key to tumor progression; however the signaling pathways involved remain unclear. Rapid expansion of breast cancer cells requires sufficient supply of oxygenated blood supported by tumor induced neovasculature. Our previous studies demonstrated that estrogen mediates neovascularization via recruitment of bone marrow derived endothelial progenitor cells (BM-EPCs). However, hypoxia, a major cellular characteristic of cancer cell growth, mimics estrogen induced vascularization as evidenced by HIF-1α translocation and secretion of vascular endothelial growth factor (VEGF). These studies were carried out in the TG1-1 murine mammary cancer cell line and used as a model. Conditioned media from TG1-1 cells enhanced endothelial cell migration and tube formation in vitro. Treatment of tumor cells with the anti-estrogen Fulvestrant as well as the HIF-1 inhibitor YC-1 abrogated the effects of estrogen. Further, use of the PI3K inhibitor wortmannin as well as the protein inhibitor cyclohexamide, elucidated the necessity of a functional AKT signaling pathway in this estrogen induced neovasculogenesis. While the cell-cell interaction studies demonstrate a considerable modulation of the tumor microenvironment, the co-culture experiments using immunomodulatory cells and epithelial cells induced epithelial to mesenchymal transition (EMT) in TG1-1 cells. We demonstrated that the murine macrophage cell line RAW264.7 secretes factors that modulate tumor cell EMT via upregulation of TWIST and Slug and an increase in tumor cell migration and invasion. To elucidate the modulatory secreted factors, we performed western blot analysis of the TGF-β signaling pathway and observed differences in SMAD levels. However, neutralizing antibody studies indicate that TGF-β is not the sole modulator of RAW264.7 induced EMT in Tg1-1 cells. Taken together, cytokines as extrinisic factors and tumor hypoxic conditions generating intrinsic factors, act in concert to alter breast cancer progression. Our data demonstrate a need to target multiple TME interacting pathways as a future breast cancer treatment strategy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1494. doi:1538-7445.AM2012-1494