Abstract 4263: Aberrant phospholipid signalling in EBV-associated nasopharyngeal carcinoma.

Abstract

Abstract Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV) associated malignancy that is particularly prevalent in Asia. The main challenges in the management of NPC include late presentation and severe side effects of chemo-radiotherapies due to the close proximity of tumours to vital structures. Two bioactive lipids, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), which signal through G protein-coupled receptors, regulate many biological processes associated with tumour development and progression. Therefore, LPA and S1P have emerged as potential targets in cancer therapies, but the roles of these lipid molecules in the pathogenesis of NPC have not been investigated. Microarray analyses revealed differential expression of several key regulators of LPA and S1P metabolism in NPC cells compared to non-malignant nasopharyngeal epithelium. Imunohistochemical studies showed that autotaxin and SPHK1, the key enzymes involved in the production of LPA and S1P, respectively, were expressed by the tumour cells in primary NPC tissues. QPCR analyses demonstrated that an EBV-positive NPC cell line, C666-1, expressed higher levels of autotaxin and SPHK1 as compared to six EBV-negative NPC cell lines, suggesting that EBV infection might contribute to the de-regulation of phospholipid signalling in NPC. The microarray data showed that LPA receptor 5 (LPA5) was significantly down-regulated in primary NPC tissues and, similarly, LPA5 protein expression in tumour cells was weak or absent in 17/22 primary NPC cases. Consistent with these findings, LPA5 mRNA levels were significantly lower in a panel of six EBV-infected cell lines than in non-infected controls. By treating NPC cell lines with exogenous LPA, we showed that LPA enhanced the migration of NPC cells in vitro. Given that NPC is characterised by prominent lymphocyte infiltration, the effect of LPA on cells within the NPC tumour microenvironment was examined by treating several clones of EBV-specific cytotoxic T lymphocytes (CTLs) in vitro. LPA inhibited the secretion of IFN-γ from peptide stimulated CTLs in a dose-dependent manner, indicating that LPA could inhibit CTL function. Collectively, our results demonstrate that LPA and S1P signalling are de-regulated in NPC. Aberrant LPA production may promote a more aggressive phenotype in NPC and EBV infection might contribute to the aberrant LPA signalling by down-regulating LPA5. Targeting LPA and/or its signalling pathways might represent a novel therapeutic strategy with which to improve the efficiency of EBV-based CTL therapy in NPC patients. Citation Format: Lee-Fah Yap, Christopher W. Dawson, Rajadurai Pathmanathan, Hui-Min Lee, Paul Lim, Tracey Haigh, John R. Arrand, Graham S. Taylor, Ian C. Paterson, Paul G. Murray. Aberrant phospholipid signalling in EBV-associated 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 4263. doi:10.1158/1538-7445.AM2013-4263