Abstract 4309: Fibulin-2 suppresses tumor growth and angiogenesis through the inhibition of Erk1/2 and p65 pathways in nasopharyngeal carcinoma.

Abstract

Abstract Nasopharyngeal carcinoma (NPC) has distinctive ethnic and geographic distributions, with the highest incidence in Southern China. Infection with the human herpesvirus, Epstein-Barr virus, genetic predisposition, dietary, and environmental factors are high-risk factors for the development of NPC. Evidence indicates that loss of heterozygosity on chromosome 3 is one of the early events contributing to the cancerization of normal nasopharyngeal epithelial cells. By using a chromosome 3 NotI genomic microarray, Fibulin-2 (FBLN2) mapping to chromosome 3p25.1, was previously identified as a candidate tumor suppressor. FBLN2, which is an extracellular matrix (ECM) protein, contains four domains, regions consisting of cysteine-rich and cysteine-free, anaphylatoxin-like domain, serial EGF-like repeats, and a fibulin module. FBLN2 is silenced by promoter hypermethylation in NPC. Re-expression of FBLN2 in NPC cell lines significantly reduces colony formation, cell proliferation, migration, invasion, and in vivo tumor formation and angiogenesis. In this study, the aim is to investigate the molecular mechanisms and signaling pathways of FBLN2-mediated tumor suppressive and anti-angiogenesis effects. Full-length FBLN2 was subcloned into inducible tetracycline-regulated and lentivirus systems. Phosphorylated forms of the key signaling molecules, Erk1/2 and NFκB, were found to be significantly reduced in FBLN2 stably-expressing NPC cell lines after phosphorylation target screening using Western blot analysis. FBLN2 also induces changes in the cytoskeleton arrangement, possibly through the regulation of Rho GTPases. Thus, the activities of Rho GTPases were determined by the Rho pull-down assays and immunofluorescence staining with confocal microscopy. FBLN2 is able to reduce the tumor formation ability via inhibiting Erk1/2 and NFκB pathways and to inhibit the cell migration and invasion via regulating Rho GTPase activities. FBLN2 is a secretory protein and is generally silenced in NPC, suggesting the possibility that it may be useful as a diagnostic marker and/or new target for therapeutics of NPC. Therefore, these studies provide strategic new insights into the understanding of the mechanistic role of FBLN2 in NPC and enhance our understanding of the molecular genetic basis of NPC tumorigenesis. Citation Format: Wai Ho Shuen, Maria Li Lung. Fibulin-2 suppresses tumor growth and angiogenesis through the inhibition of Erk1/2 and p65 pathways in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4309. doi:10.1158/1538-7445.AM2013-4309