Abstract 2045: Mechanistic insights into the role of cAMP-regulated EPAC1 in tumor-induced angiogenesis and metastatic potential in triple-negative breast cancer

Background: Breast cancer is the leading cause of cancer-related mortality in women. Triple negative breast cancer (TNBC) is one of most aggressive subtypes, which is often accompanied by metastasis, a feature that requires development of new blood vessels (neovasculature) to disseminate tumor cells throughout the body. We recently reported that down-regulation of exchange factor directly activated by Cyclic AMP (cAMP), also known as EPAC1, leads to a reduction in proliferation and inhibition of cell migration. Methods: Here, using gene knockdown by siRNA and a 3-dimensional in-vitro TNBC co-culture model with Human Vascular Endothelial Cells (HUVECs), we studied microvascular density and the role of EPAC1. Angiogenesis proteome profiling was employed to examine protein networks that were regulated by EPAC1 in the TNBC cell line, MDA-MB-231. Immunofluorescence along with Electric cell-substrate impedance sensing (ECIS) was used to study vascular permeability. To confirm these findings in a translational context, we employed a human tumor explant assay that predicts clinical response to therapy (CANscriptTM) and studied CD34+ nodes to determine how neovasculature associates to drug response. Results: We determined that downregulation of EPAC1 in the TNBC cell line, MDA-MB-231, leads to reduction of proteins involved in cell migration, metastasis, angiogenesis and adhesion. Interestingly, we determined that loss of EPAC1 leads to increased expression of negative regulators in these same pathways. Immunofluorescence imaging showed that EPAC1 downregulation in MDA-MB-231 cells leads to diminished expression of proteins such as Paxillin, MENA, MMP-9 and tubulin. indicated that EPAC1 role in vascular permeability. Finally, CANscriptTM demonstrated a link between response to therapy and microvascular density, which was reduced under drug pressure in patients that were predicted to respond to treatment. Conclusion: Our results suggest that EPAC1 is a driver of microvascular density in the tumor microenvironment, a feature that may play a key role in distant metastasis and therapy failure. Ex-vivo modeling of neovasculature may be a novel strategy to predict clinical response and distant metastasis. Citation Format: Muthu Dhandapani, Aaron Goldman, Naveen Kumar, Peeyush Prasad, Eshna Jash, Itender Singh, Kodaganur S. Gopinath, Krishnamurthy S, Prabhusankar P, Seema Sehrawat. Mechanistic insights into the role of cAMP-regulated EPAC1 in tumor-induced angiogenesis an