Abstract 5132: Hypo-glycosylation of vascular endothelial growth factor receptor-1 may contribute to intracrine signaling in human colorectal cancer cells

Abstract

Abstract Introduction: Vascular endothelial growth factor receptor-1 (VEGFR-1) is highly expressed in endothelial cells, macrophages and cancer cells in the tumor microenvironment. VEGFR-1 plays an important role in tumor angiogenesis, inflammation and metastasis. In colorectal cancer (CRC) cells with hyperactive Wnt signaling, its function has been linked to cell motility, anchorage-independent growth, and cell survival. To better understand the role of VEGFR-1 in CRC, we performed studies to define the subcellular location and post-translational modifications of VEGFR-1 in human CRC cells. Methods/Results: Utilizing IHC analysis, GFP-tagged imaging and cell surface receptor assays, we observed that VEGFR-1 locates mostly in intracellular compartments in CRC cells, which is distinct from its membrane receptor status in endothelial cells. Moreover, spontaneous apoptosis was increased with endogenous VEGF knockout whereas treatment with the VEGF neutralizing antibody bevacizumab had no effect on apoptosis (Samuel et al. Oncogene, in press); these studies suggest that CRC cells require VEGF/VEGFR-1 intracrine signaling for suppression of apoptosis. In order to understand the means by which VEGFR-1 cellular localization is determined, we analyzed the glycosylation of VEGFR-1 in CRC cells, endothelial cells and clinical specimens of metastatic CRC from the liver. We found that VEGFR-1 is partially N-glycosylated by high mannose oligosaccharides in the CRC cells and human tumors, in contrast to complex, mature N-glycosylation of VEGFR-1 in the endothelial cells and normal liver tissue. Conclusion: VEGFR-1 is differentially post-translationally modified and intracellularly localized in CRC cells and metastatic tumors. Because N-glycosylation is critical for the membrane receptor's intracellular trafficking and ligand interaction on the cell surface, hypo-glycosylation of VEGFR-1 in CRC cells likely contributes to its cytoplasmic localization and intracrine activation through a non-RTK pathway. The implications of intracrine function of VEGFR-1 in CRC warrant further investigation. 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 5132. doi:10.1158/1538-7445.AM2011-5132