Abstract 56: Establishment and characterization of new tumor xenografts and cancer cell lines from EBV positive nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is rare worldwide but common in southern China, including Hong Kong. The endemic NPC among southern Chinese is typically non-keratinizing carcinoma, which is almost 100% associated with Epstein-Barr virus (EBV) infection. Patient-derived xenografts (PDXs), given their close resemblance with patient tumors, serve as important models in preclinical evaluation for novel therapeutic drugs. For unclear reasons, it has been difficult to establish NPC PDXs in vivo and cell lines in vitro. Currently, there are few NPC PDXs available for research, including X666, X2117, C15, C17 and C18. However, all of them have been passaged in nude mice for over 25 years and may deviate from their original NPC tumors in patients. In vitro, C666-1 is the only EBV-positive (EBV+ve) NPC cell line which has been used extensively in investigations. C666-1 was established from the NPC xenograft (X666), which had been propagated for a long period of time. Most if not all the other previously reported NPC cell lines have lost their EBV episomes upon in vitro propagation. Furthermore, many of these reported NPC cell lines have been shown with genetic contamination of HeLa cells. Hence, their applications in NPC studies are limited. The lack of representative nasopharyngeal carcinoma (NPC) models has also seriously hampered research on EBV carcinogenesis and preclinical studies in NPC. In this study, we report the successful establishment and comprehensive characterization of four new NPC PDXs (all EBV+ve) and three NPC cell lines (one EBV+ve; two EBV-ve). These newly established EBV+ve NPC PDXs and cell lines significantly recapitulate the mutation profiles of their original NPC tumors, and harbor common genetic alterations reported in NPC, which supports their potential applications in the investigations of NPC pathogenesis. We postulate that lytic EBV reactivation may be an intrinsic barrier to the successful establishment of EBV+ve NPC PDXs and cell lines. The ROCK inhibitor (Y-27632) was shown to be able to suppress epithelial differentiation and lytic reactivation of EBV in infected NPC cells. Establishment of a new EBV-positive NPC cell line, NPC43, was achieved directly from patient NPC tissues by including Y-27632 in culture medium. NPC43 cells exhibited tumorigenicity in immunodeficient mice, and could be induced to undergo EBV lytic reactivation with production of infectious visions. The establishment and characterization of new NPC PDXs and cell lines will provide valuable experimental tools for NPC and EBV research. Funding support: Research Grant Council, Hong Kong: AoE NPC grant (AoE/M-06/08), Theme-based Research Scheme grant (T12-401/13-R) and Collaborative Research Fund (C7027-16G), General Research Fund (106140069, 106160185, 17111516, 17110315) and HMRF grant (04151726, 13142201). Citation Format: Weitao Lin, Yim Ling Yip, Lin Jia, Wen Deng, Kwok Wai Lo, Chin Man Tsang, Maria Li Lung, George Sai Tsao. Establishment and characterization of new tumor xenografts and cancer cell lines from EBV positive nasopharyngeal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 56.