Abstract 3664: Epac1 activates migration of melanoma and angiogenesis of endothelial cells via FGF-2 intercellular signaling
Authors: Baljinnyam Erdene , Umemura Masanari , De Lorenzo Mariana S. , Iwatsubo Kousaku 
Published: June 2012

Abstract
Background: Fibroblast growth factor (FGF-2) regulates migration and angiogenesis in cancer. The binding of FGF-2 to its receptor requires N-sulfated glucosamine in heparan sulfate (HS), suggesting that a molecule that increases N-sulfation of glucosamine could enhance FGF-2 signaling. Recently, we demonstrated that Epac1, an exchange protein activated by cAMP, increases expression of N-deacetylase/N-sulfotransferase-1 (NDST-1) that increases N-sulfation of glucosamine. It is plausible that melanoma cells with abundant expression of Epac1 produce N-sulfation-rich glucosamine, which results in enhancement of intercellular FGF-2 signaling in melanoma microenvironment. The purpose of this study was to examine whether Epac1-rich melanoma cells can increase migration of surrounding Epac1-poor melanoma cells and endothelial cells.
Methods: Immunohistochemistry was performed on human melanoma tissue microarrays to examine expressions of Epac1, NDST-1 and N-sulfated glucosamine. For in vitro studies, we used 2 human melanoma cell lines, WM1552C (radial growth phase melanoma) and C8161 (metastatic melanoma), and human umbilical vein endothelial cells (HUVEC). Since Epac1 expression was much lower in WM1552C than C8161 cells, WM1552C were used as Epac1-poor, and C8161 as Epac1-rich melanoma cells. We evaluated the migratory responses in WM1552C and HUVEC cells to conditioned medium (CM) from C8161 cells with or without Epac1 ablation (C8161/Epac1(−)) or overexpression (C8161/Epac1OE). Endothelial tube formation assay was performed in HUVEC with conditioned media.
Results: The expression of Epac1 positively correlated with that of NDST-1, and N-sulfated glucosamine in human melanoma tissue microarray. Migration of WM1552C and HUVEC cells was increased by CM from C8161 cells, which was significantly enhanced by CM from C8161/Epac1OE, but reduced by CM from C8161/Epac1(−). The CM-induced migration was inhibited by a neutralizing antibody against FGF-2 (nFGF-2 ab) or heparitinase, a HS-degrading enzyme, suggesting involvement of FGF-2 and HS in the CM-induced migration. Binding of FGF-2 to FGF receptors in HUVEC cells was increased by CM from C8161 cells, which was significantly enhanced by CM from C8161/Epac1OE but reduced by CM from C8161/Epac1(−). Similar to migration, the CM-induced FGF-2 binding was inhibited by nFGF-2 ab or heparitinase. Since the expression of FGF-2 in C8161 cells was not changed by ablation of Epac1 or Epac1 overexpression, these data suggested that C8161 cells increase migration of WM1552C and HUVEC cells via modification of HS. Finally, tube formation of HUVEC was increased by CM from C8161 cells, but it was inhibited by Epac1 ablation on these cells.
Conclusion: Epac1-rich melanoma cells increase migration of Epac1-poor melanoma cell, and endothelial cells via intercellular FGF-2-signaling, suggesting the role of Epac1 in melanoma progression.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3664. doi:10.1158/1538-7445.AM2011-3664