Abstract 482: Epstein-Barr virus-encoded miRNAs target ATM-mediated response in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a highly invasive epithelial malignancy that is prevalence in southern China and Southeast Asia. It is well-known to be associated with latent Epstein-Barr virus (EBV) infection. By using small RNA sequencing, we previously established a comprehensive miRNA profile in a panel of NPC samples and revealed that the EBV-encoded miRNAs derived from BamHI-A rightward transcripts (miR-BARTs) are abundantly expressed. The important roles of miR-BARTs in cancer development have been reported extensively. In the present study, we identified multiple putative binding sites of miR-BART5-5p, BART7-3p, BART9-3p and BART14-3p on the 3'-UTR of a critical DNA double-strand break (DSB) repair gene, Ataxia-Telangiectasia-Mutant (ATM). Notably, the expression of these 4 miR-BARTs represented more than 10% of all EBV-encoded miRNAs in NPC cells while downregulation of ATM expression was observed in our local primary NPC samples in both qRT-PCR and immunohistochemical (IHC) staining analysis. In addition, the abilities of miR-BARTs to downregulate ATM expression were demonstrated in the transient transfection experiments. By manipulating the miR-BARTs expression in epithelial cell lines, we further revealed that these four viral miRNAs could inhibit both ionizing radiation (IR)-induced ATM kinase activity and BZLF1-induced viral lytic reactivation. In conclusion, our findings suggest that miR-BART5-5p, BART7-3p, BART9-3p and BART14-3p work co-operatively to modulate DNA damage response and to maintain viral latency, contributing to the NPC tumorigenesis. Acknowledgement: Theme-based Research Scheme (T12-401/13-R) and GRF (14104415 and 14138016), Research Grant Council, Hong Kong.

Citation Format: Raymond W. Lung, Po-Man Hau, Joanna H. Tong, Ka-Hei Lam, Anthony W. Chan, Kevin Y. Yip, George S. Tsao, Kwok-Wai Lo, Ka-Fai To. Epstein-Barr virus-encoded miRNAs target ATM-mediated response in nasopharyngeal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 482.

Nasopharyngeal carcinoma super-enhancer-driven ETV6 correlates with prognosis

Nasopharyngeal carcinoma (NPC) most frequently occurs in southern China and southeast Asia. Epidemiology studies link NPC to genetic predisposition, Epstein-Barr virus (EBV) infection, and environmental factors. Genetic studies indicate that mutations in chromatin-modifying enzymes are the most frequent genetic alterations in NPC. Here, we used H3K27ac chromatin immune precipitation followed by deep sequencing (ChIP-seq) to define the NPC epigenome in primary NPC biopsies, NPC xenografts, and an NPC cell line, and compared them to immortalized normal nasopharyngeal or oral epithelial cells. We identified NPC-specific enhancers and found these enhancers were enriched with nuclear factor κB (NF-κB), IFN-responsive factor 1 (IRF1) and IRF2, and ETS family members ETS1 motifs. Normal cell-specific enhancers were enriched with basic leucine zipper family members and TP53 motifs. NPC super-enhancers with extraordinarily broad and high H3K27ac signals were also identified, and they were linked to genes important for oncogenesis including ETV6. ETV6 was also highly expressed in NPC biopsies by immunohistochemistry. High ETV6 expression correlated with a poor prognosis. Furthermore, we defined the EBV episome epigenetic landscapes in primary NPC tissue.

Abstract 4417: The role of EBV infection in aerobic glycolysis in nasopharyngeal carcinoma

Accumulating evidence indicates that oncogenic viral protein exerts a crucial role in activating aerobic glycolysis during tumorigenesis, but the underlying mechanisms are largely undefined. The Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) is a trans-membrane protein with potent cell signaling properties and has tumorigenic transformation property. Activation of NF-κB is a major signaling pathway mediating many downstream transformation properties of LMP1. Here we report that activation of mTORC1 by LMP1 is a key modulator for activation of NF-κB signaling to mediate aerobic glycolysis. NF-κB activation is involved for LMP1-induced upregulation of glucose transptor-1 (Glut-1) transcription and growth of nasopharyngeal carcinoma (NPC) cells. Collectively, blocking the activity of mTORC1 signaling effectively suppressed LMP1-induced NF-κB activation and Glut-1 transcription. Interfering NF-κB signaling has no effect on mTORC1 activity but effectively altered Glut-1 transcription. Luciferase promoter assay of Glut-1 also confirmed that Glut-1 is a direct target gene of NF-κB signaling. Furthermore, we demonstrated that the LMP1 C-terminal activating region (CTAR) 2 is the key domain involved in mTORC1 activation, mainly through IKKβ-mediated phosphorylation of TSC2 at Ser939. Depletion of Glut-1 effectively led to suppression of aerobic glycolysis, inhibition of cell proliferation, colony formation, and attenuation of tumorigenic growth property of LMP1-expressing nasopharyngeal epithelial (NPE) cells. These findings suggest that targeting the signaling axis of mTORC1/NF-κB/Glut-1 represents a novel therapeutic target against NPC.

Acknowledgement: 96 800x600 This project was supported by the General Research Fund (HKU 779810M, 17120814 and 17161116), CRF equipment grant (1061402980, Health and Medical Research Fund of Hong Kong (12110782), AoE grant (AoE/M-06/08) and TBRS grant (T12-401/13-R). We thank Prof. Dongyan Jin (Department of Biochemistry, The University of Hong Kong) for the kind gifts of IKK related plasmids and Prof. Zhenguo Wu (Division of Life Science, The Hong Kong University of Science and Technology) for the discussion and interpretation of the data. We also thank Mr. Tony Chan for his technical support.

Note: This abstract was not presented at the meeting.

Citation Format: George S. Tsao, Jun Zhang, Lin Xia, C Tsang, Weitao Lin, Y Yip, W Deng, K Lo, M Lung. The role of EBV infection in aerobic glycolysis in nasopharyngeal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4417. doi:10.1158/1538-7445.AM2017-4417

Abstract 5003: Functional significance of TIGAR expression in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus associated cancer of the nasopharynx. Annual incidence in China is high, reaching up to 25 per 100,000. NPC is a highly invasive and metastatic disease. At diagnosis, over 60% of patients have advanced disease where treatment failure due to distant recurrence or metastasis is common. More effective forms of therapy to treat this deadly disease are therefore urgently needed.

The TP53 induced glycolysis and apoptosis regulator (TIGAR) is a p53 target gene which blocks glycolysis and promotes cellular metabolism via the pentose phosphate pathway. TIGAR promotes production of cellular nicotinamide adenine dinucleotide phosphate (NADPH), leading to enhanced scavenging of intracellular reactive oxygen species (ROS) and inhibition of oxidative-stress induced apoptosis in normal cells. Previously, we have found that a novel nucleoside analog inhibited cell growth and induced apoptosis in NPC cell lines via down-regulation of TIGAR expression. Moreover, the growth inhibitory effect of c-Met tyrosine kinase inhibitors was ameliorated by over-expression of TIGAR in NPC cell lines. These results are indicative of a pivotal role for TIGAR expression in maintaining NPC cell survival.

In this study, we investigated the expression pattern of TIGAR in NPC tumor tissues and the consequences of TIGAR overexpression and knockdown on NPC cell growth and invasion. It was found that TIGAR is overexpressed in 27 out of 36 (75%) NPC cases in the tumor cells compared to their respective normal epithelial cells. Overexpression of TIGAR in NPC cell lines resulted in increased proliferation, invasion, NADPH production and up-regulation of mesenchymal markers including fibronectin and vimentin. These changes were reversed when TIGAR expression was knocked down by transfection with siRNA, demonstrating specificity of the observed effects. Together, our results indicate that TIGAR expression promotes proliferation, invasiveness and expression of mesenchymal markers in NPC cells. These findings may form the basis for development of a new therapeutic target for treatment of NPC in the future.

Citation Format: Elaine YL Wong, SC Cesar Wong, Charles ML Chan, Emily KY Lam, Louisa Ho, Cecilia PY Lau, Thomas CC Au, Amanda KC Chan, CM Tsang, George SW Tsao, Vivian WY Lui, Anthony TC Chan. Functional significance of TIGAR expression in nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5003. doi:10.1158/1538-7445.AM2014-5003

A comparative study of the clinicopathological significance of E-cadherin and catenins (alpha, beta, gamma) expression in the surgical management of oral tongue carcinoma

PURPOSE

E-cadherin and catenins are important epithelial adhesion molecules in normal epithelium. Loss of E-cadherin-catenin adhesion is an important step in the progression of many epithelial cancers. E-cadherin and catenins expression in carcinoma of the tongue were evaluated in relation to their clinicopathological features and prognostic values.

METHOD

Immunohistochemical staining was carried out with E-cadherin and (alpha, beta, gamma)-catenin monoclonal antibodies for 85 surgical specimens of oral tongue carcinoma, nine matched metastatic lymph nodes, and seven locally recurrent tumours.

RESULTS

There was under-expression in 85% of E-cadherin, 94% of alpha-catenin, 89% of beta-catenin, and 83% of gamma-catenin in the primary tumours. There was no correlation of E-cadherin/catenin expression with sex, age, cancer stage, and differentiation. Nodal metastasis was found in 68% of patients with weak expression of gamma-catenin compared with 9% with strong expression in primary tumours (chi-square, P = 0.02). E-cadherin was a significant prognostic factor for survival and recurrence; patients with weak E-cadherin expression had 53% 5-year survival compared with 85% with strong expression (Wilcoxon, P = 0.0159).

CONCLUSIONS

Both E-cadherin and catenins were highly under-expressed in oral tongue carcinoma, metastatic lymph node, and recurrent tumour. gamma-catenin had predictive value for nodal metastasis. E-cadherin was, however, a more important prognostic factor for recurrence and survival.

Regulation of telomerase activity by gamma-radiation in nasopharyngeal carcinoma cells

Since telomerase has been suggested to play a role in radiation response, the effect of radiation on the regulation of telomerase activity was studied on two NPC cell lines, CNE1 and 915. In order to investigate the correlation between cell survival and telomerase activity, three low doses (0.25, 0.5 and 1 Gy) and three high doses (2, 4 and 8 Gy) of gamma-radiation were used. We found that low doses of radiation induced telomerase activity (up to 250% of untreated controls) followed by a cell cycle G1 arrest, suggesting that the up-regulation of telomerase may play a role in initiating radiation induced cell cycle arrest. High doses of radiation resulted in decreased telomerase activity (down to 30% of untreated controls) and this was followed by an increased cell death. Our results indicate that the up-regulation of telomerase activity is an important response to radiation induced sub-lethal DNA damage. Our results also suggest that inhibition of telomerase activity by high doses of radiation may play a role radiation-induced cell death.

Nuclear matrix of human ovarian cancer cells in vitro

The epithelial neoplasia constitute 60% of all primary tumors of the ovary and 90% of these are malignant. Nuclear matrix has been found to be involved in normal and abnormal nuclear activities. Previously, we have identified tumor-associated nuclear matrix proteins in cancers of human liver, nasopharynx and cervix. In this study, we compared nuclear matrices of immortalized ovarian and cancer cell lines by morphometric and 2-D gel electrophoresis analysis.

Studies of lymphocyte subpopulations and immunoglobulin production in IgA nephropathy

This work was undertaken to examine the immunoregulation of T lymphocytes in patients with IgA nephropathy. Fifty patients and thirty-seven control subjects were studied in an infection-free interval. T lymphocyte subpopulations were determined using OKT monoclonal antibodies against helper (OKT4) and suppressor (OKT8) T cell subsets. The proportions of T lymphocyte subpopulations did not differ between patients and controls. Patients with significant renal impairment demonstrated a reduced OKT4/T8 ratio (p less than 0.001) due to an absolute reduction of T helper cells (p less than 0.02) and an increase of T suppressor cells (p less than 0.001). Longitudinal studies performed in 13 patients revealed consistent findings during clinical quiescence. However, synpharyngitic macroscopic haematuria was associated with a rise in T4 positive cells and a simultaneous reduction of T8 positive cells; these changes reverted to pre-infection values when the infection subsided. Functional studies assessing T lymphocyte activities including in vitro immunoglobulin synthesis by cultured peripheral blood mononuclear cells, thymidine uptake by cultured lymphocytes and T lymphocytes activation with expression of interleukin-2 receptors were measured in unstimulated and mitogen stimulated cultures. No significant difference between patients with IgA nephropathy in clinical quiescence and the control subjects was demonstrated. Our results failed to support a shift in the immuno-regulatory T lymphocyte subpopulations during clinical quiescence but a more profound defect in immunoregulation may probably occur during clinical exacerbation.