title: Epstein-Barr virus infection to Epstein-Barr virus-negative nasopharyngeal carcinoma cell line TW03 enhances its tumorigenicity.
abstract: Almost all nasopharyngeal carcinomas (NPCs) are infected by Epstein-Barr virus (EBV), but most ex vivo NPC cells lose EBV genomes during passages. In this study, an EBV-negative NPC cell line, TW03, established from EBV-carrying NPC was reinfected with EBV by cocultivation with irradiated Akata cells carrying recombinant EBV containing a neomycin-resistant gene. The reinfected EBV (+) TW03 cells expressed EBERs and EBNA1, but not EBNA2, lytic proteins (ZEBRA and EA-D), or LMP1. They had an epithelial appearance similar to that of EBV (-) TW03 cells. The doubling times of EBV (+) and EBV (-) TW03 cells were almost identical. However, the EBV (+) TW03 cells formed larger colonies with ragged contours in anchorage-independent cultures. An in vitro invasion assay showed that EBV (+) TW03 cells had a higher invasive activity than EBV (-) TW03 cells (p < 0.01). Both EBV (-) and EBV (+) TW03 cells formed poorly differentiated squamous cell carcinomas in SCID and nude mice. EBV (+) TW03 cells showed a higher tumorigenicity to nude mice (12 of 13) than EBV (-) TW03 cells (1 of 9) (p < 0.001). In the severe combined immunodeficiency (SCID) tumors of EBV (+) TW03 cells, not all of the tumor cells were EBER-1 positive. EBER-1 was more frequently detected in the peripheral regions and daughter nodules of the tumors than in the central areas. The microdissection polymerase chain reaction showed that the EBER-1-negative TW03 cells in the EBV (+) TW03 SCID tumors lost EBV genomes. EBER-1-negative cells showed as high a rate of Ki-67 positivity as EBER-1-positive cells, indicating that the former were proliferating rather than dead or dying. In horny pearls, keratinizing cells were ZEBRA-positive and EBER-negative. Loss of EBV genomes was not associated with squamous differentiation. These data indicated that reinfection of EBV promotes the tumorigenicity of EBV (-) TW03 cells by enhancing the invading activity.
authors.affiliation: Department of Pathology, Okayama University Medical School, Japan. terra@med.okayama-u.ac.jp
authors.forename: N
authors.initials: N
authors.lastname: Teramoto
authors.forename: A
authors.initials: A
authors.lastname: Maeda
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: K
authors.initials: K
authors.lastname: Hayashi
authors.forename: T
authors.initials: T
authors.lastname: Oka
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Takada
authors.forename: G
authors.initials: G
authors.lastname: Klein
authors.forename: T
authors.initials: T
authors.lastname: Akagi
mesh_terms: D000818:Animals; D001483:Base Sequence; D002455:Cell Division; D018920:Coculture Techniques; D017931:DNA Primers; D004854:Herpesvirus 4, Human / Q000302:isolation & purification; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D016513:Mice, SCID; D009303:Nasopharyngeal Neoplasms / Q000473:pathology* / Q000821:virology; D009361:Neoplasm Invasiveness; D016133:Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D014412:Tumor Virus Infections / Q000473:pathology* / Q000821:virology
chemical_list: D017931:DNA Primers