Activation of ROR alpha-SEMA3F pathway in epithelial cells inhibits angiogenesis

Cross-talk between epithelial and endothelial cells provides morphogenic cues to guide angiogenesis in many pathological conditions. Our long-term goal is to understand molecular mechanisms of the cross-talk and identify potential therapeutic targets to modulate angiogenesis with the ultimate goal of providing better therapy for these diseases. SEMA3F is a microenvironmental factor with anti-angiogenesis activity. SEMA3F inhibits endothelial cell adhesion, migration, and tubule formation. We have exciting data demonstrating that the RORá-SEMA3F pathway is inactivated during the disruption of epithelial polarity, and restoring this pathway in disorganized epithelial cells suppressed angiogenesis. These data include: 1) Disorganized mammary epithelial cells promote migration and tubule formation of endothelial cells compared to the polarized epithelial cells in the three-dimensional (3D) co-culture assay; 2) The RORá-SEMA3F pathway is inactivated in disorganized epithelial cells compared to polarized epithelial cells; 3) Expression of RORá in epithelial cells induces SEMA3F expression and suppresses migration of endothelial cells in the 3D co-culture assay; 4) Reduced RORá mRNA levels in breast cancer tissues are associated with poor prognosis and metastasis. Building upon these findings, the central hypothesis of our proposal is that activation of RORá in epithelial cells inhibits angiogenesis through inducing SEMA3F expression. The objective of this proposal is to delineate the mechanisms by which RORá mediates signal transduction from epithelial to endothelial cells and to determine whether activation of the RORá-SEMA3F pathway in disorganized MECs inhibits angiogenesis. To test our central hypothesis and achieve the objective of this proposal, we have designed experiments with the following specific aims. Specific aim 1 will test the hypothesis that the RORá-SEMA3F pathway in mammary epithelial cells inhibits migration and tubule formation of endothelial cells in the 3D coculture assays. Specific aim 2 will test the hypothesis that RORá recruits chromatin remodeling complexes to the SEMA3F promoter to induce gene transcription. Specific aim 3 will test the hypothesis that activation of RORá-SEMA3F pathway in epithelial cells inhibits angiogenesis in vivo. Our findings reveal that RORá induce SEMA3F expression in polarized mammary epithelial cells, and restoring this pathway in disorganized and malignant epithelial cells inhibits migration of endothelial cells. We anticipate that our work on the RORá-SEMA3F signaling axis will significantly advance our understanding of signal transduction from epithelial to endothelial cells and will contribute to the successful targeting of angiogenesis. We have put together a strong team with expertise in biochemistry and cell biology (Xu Ren) and the in vivo angiogenesis model (Dr. Jayakrishna Ambati). To achieve our aims, we will use a novel 3D co-culture system and the corneal angiogenesis model as well as a balanced approach utilizing breast cancer tissue arrays, a variety of molecular methods and biochemical characterization of molecular interactions. Therefore, we are well-positioned to advance the proposed research.