EXPRESSION OF THE DNASE ENCODED BY THE BGLF5 GENE OF EPSTEIN-BARR-VIRUS IN NASOPHARYNGEAL CARCINOMA EPITHELIAL-CELLS

In contrast with most Epstein-Barr virus (EBV)-infected healthy carrie rs, nasopharyngeal carcinoma patients frequently have increased serum levels of antibodies directed against EBV-DNase. These antibodies are potentially interesting serological markers for the diagnosis and the follow-up of nasopharyngeal carcinoma (NPC). In this context, it is im portant to determine whether malignant EBV-infected cells are the sour ce of significant amounts of EBV-DNase contributing to antigenic stimu lation. Therefore EBV-DNase expression has been investigated in severa l NPC specimens. A significant expression of this viral enzyme was dem onstrated in both fresh biopsies and transplanted tumor lines. The DNa se isolated from tumor has a molecular weight varying between 52 and 6 0 kDa and its activity eluted from a single-stranded DNA affinity colu mn was specifically inhibited by both NPC sera and the rabbit polyclon al antibody against EBV-DNase. The enzyme activity was functional in t he presence of 300 mM KC1, with which cellular DNases are completely i nhibited. The DNase was mainly localized in epithelial tumor cells of both NPC biopsies and nude mice-derived NPC cells. (C) 1996 Academic P ress, Inc.