Abstract 2092: FOXO1/Sprouty2 pathway regulates vascular tumor growth

Abstract

Abstract Vascular tumors are endothelial cell neoplasms with a wide spectrum of clinical presentations, ranging from benign infantile hemangiomas in children to low-grade malignant hemangioendotheliomas and highly aggressive angiosarcomas in adults. To date, the molecular basis of vascular tumor pathogenesis is poorly understood and standard therapy for these tumors have limited clinical efficacy. Forkhead box protein O1 (FOXO1) is a transcription factor with tumor suppressor function and is dysregulated in human cancer. In this study, we showed that FOXO1 suppressed vascular tumor growth, and mechanistically, the inhibitory effects of FOXO1 were mediated by Sprouty2. FOXO1 expression was reduced in a variety of human vascular tumors examined (infantile hemangioma, hemangioendothelioma and angiosarcoma) as compared with normal blood vessels as determined by western blotting and immunohistochemical stains. Knockdown of FOXO1 gene expression with short hairpin RNA resulted in increased vascular tumor cell migration and proliferation in vitro and in vivo. Conversely, over-expression of constitutively active FOXO1 in these cells suppressed cell growth. We observed that FOXO1 interacted with Sprouty2 promoter in situ in chromatin immunoprecipitation assay and increased Sprouty2 gene expression in tumor cells. Similar to FOXO1, Sprouty2 expression was reduced in vascular tumors. Over-expression of Sprouty2 decreased tumor cell growth and migration. Conversely, knockdown of Sprouty2 increased tumor growth in vitro and in vivo. Knockdown of Sprouty2 in cells with over-expression of constitutively active FOXO1 resulted in reduced tumor growth and “rescued” the FOXO1 phenotype, indicating that Sprouty2 is an important mediator of the biological effects of FOXO1. Microarray gene expression profiling of human angiosarcoma cells with Sprouty2 knockdown together with network data integration using bioinformatics analysis and validated by quantitative PCR revealed important Sprouty2-regulated genes that are involved in angiogenesis, apoptosis and growth signal transduction pathways, including the collagen gene family, Notch signaling pathway and the GTPase IMAP family members. In summary, these findings demonstrate important growth regulatory role of the FOXO1/Sprouty2 pathway in vascular tumors and highlight the potential roles of novel pathways downstream of Sprouty2 in these tumors. Citation Format: Sriram Ayyaswamy, Wa Du, Christopher Anderson, Thuy L. Phung. FOXO1/Sprouty2 pathway regulates vascular tumor growth. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2092. doi:10.1158/1538-7445.AM2015-2092