Abstract 2007: Hypoxia induced TGF-β regulates Semaphorin7A to promote a pro-tumorigenic mesenchymal phenotype in mammary cells

The study of breast cancer relies heavily upon the identification of tumor-associated proteins that are involved with tumor growth and development. Our lab has discovered that mammary tumor cells express high levels of a novel protein known as Semaphorin7A (SEMA7A). After analyzing breast tissue samples collected at Boca Raton Regional Hospital, we have found that normal human mammary epithelial cells express negligible mRNA levels of SEMA7A, while the malignant mammary tumor cells express elevated levels of SEMA7A. Additionally, our laboratory has established a murine model of mammary cell lines that parallels our human findings. Currently, we have correlated high levels of SEMA7A with increasing tumor malignancy and metastasis. However, it is still unknown what factors could induce the production of SEMA7A in mammary tumors. Recent studies have proven that the expression and induction of SEMA7A in normal endothelial cells is regulated under a hypoxic-response element in the promoter of its gene. Although hypoxia is an established tumorigenic factor, it is unknown if the increased hypoxic conditions in breast tumors could induce SEMA7A. In this study we have investigated if exposing mammary cells to hypoxia induces the expression of pro-tumorgenic SEMA7A. Our results show that SEMA7A is up-regulated in 4T07 and 4T1 mammary tumor cells after hypoxic exposure via TGF-β activation of the PI3/AKT pathway. Furthermore, we have found that shRNA silencing of the SEMA7A in 4T1 mammary cells attenuates the activation of pro-angiogenic and mesenchymal genes even after hypoxic stimuli. In vivo, these cells show a reduced proliferation and metastatic potential. We therefore postulate an exciting new role for SEMA7A as a TGF-β effector that promotes tumorigenesis during breast cancer progression. Citation Format: Ramon A. Garcia-Areas, Stephania Libreros, Samantha Amat, Camila Castro-Silva, Kathy Schilling, Vijaya Iragavarapu-Charyulu. Hypoxia induced TGF-β regulates Semaphorin7A to promote a pro-tumorigenic mesenchymal phenotype in mammary cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2007. doi:10.1158/1538-7445.AM2014-2007