TRANSCRIPTIONAL ACTIVATION OF NF-KAPPA-B ACTIVITY BY EPSTEIN-BARR-VIRUS (EBV) LMP1 AS A SELECTIVE THERAPEUTIC STRATEGY FOR EBV-ASSOCIATED DISEASES

Epstein-Barr virus (EBV) has been known to be associated with many mal ignant tumors, including nasopharyngeal carcinoma (NPC). Previous stud ies have indicated that an EBV-encoded oncoprotein, latent membrane pr otein 1 (LMP1), is expressed in many NPC tissues. LMP1 has been shown to stimulate HIV LTR through the two NF-kappa B binding sites within t his promoter. In this study, we examined the feasibility of using this property of LMP1 as a therapeutic strategy for the treatment of NPC. This therapy consists of the preferential killing of the LMP1-expressi ng cells by gene transfer using the NF-kappa B-mediated herpes simplex virus thymidine kinase (HSVtk)/gancivlovir (GCV) system. The 800-bp H IV-LTR, which contains two NF-kappa B binding sites, was used to drive the HSVtk gene. Stable C33A cell clones expressing the LMP1 and the H SVtk genes were subjected to the GCV sensitivity test Results; showed that cells expressing both the LMP1 and the HSVtk genes were highly se nsitive to GCV treatment These cells were introduced into nude mice su bcutaneously and introduced intraperitoneally to these mice and the si zes of tumors became palpable within 2 weeks. GCV;was then the tumors were measured daily. Results showed that the tumors regressed in the g roup of mice carrying cells that stably expressed both the LMP1 and th e HSVtk genes, but not in mice carrying cells containing LMP1 or HSVtk alone. Our data indicate that the HSVtk gene expressed from a: NF-kap pa B-binding motif-containing promoter that is regulated by LMP1 may b e used as an in vivo gene therapy strategy of EBV LMP1-expressing canc ers such as NPC.