title: Killing Epstein-Barr virus-positive B lymphocytes by gene therapy: comparing the efficacy of cytosine deaminase and herpes simplex virus thymidine kinase.
abstract: Epstein-Barr virus (EBV)-positive lymphomas are frequent among immunosuppressed patients. We have examined the feasibility of killing EBV-immortalized B lymphocytes by gene transfer involving the use of "suicide" genes whose expression in target cells renders them susceptible to killing by a prodrug. We examined two gene/prodrug pairs: the Escherichia coli cytosine deaminase (CD) gene with the prodrug 5-fluorocytosine (5-FC), and the herpes simplex virus thymidine kinase (HSV-TK) gene with the prodrug ganciclovir. Retroviral vectors and drug selection were used to obtain CD or HSV-TK expression in cells. Both the CD/5-FC and the HSV-TK/ganciclovir combinations yielded substantial killing of EBV-immortalized B lymphocytes in vitro, although the CD/5-FC regimen had a significantly greater therapeutic margin than the HSV-TK/ganciclovir combination. The CD/5-FC pair, but not the HSV-TK/ganciclovir pair, was shown to have a "bystander killing effect" in vitro. When only 30% of the cells expressed the suicide gene, scid mouse tumors regressed in both the CD/5-FC regimen and the HSV-TK/ganciclovir regimen, documenting an in vivo bystander effect with both regimens. However, a greater percentage of tumors completely regressed with the CD/5-FC regimen. Overall, the sum of our data indicates that the CD/5-FC combination is the more promising regimen for treatment of EBV-associated lymphomas in vivo.
authors.affiliation: Department of Diagnostic Sciences, University of North Carolina School of Dentistry, Chapel Hill 27599, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Rogers
authors.forename: J Q
authors.initials: JQ
authors.lastname: Ge
authors.forename: E
authors.initials: E
authors.lastname: Holley-Guthrie
authors.forename: D K
authors.initials: DK
authors.lastname: Hoganson
authors.forename: K E
authors.initials: KE
authors.lastname: Comstock
authors.forename: J C
authors.initials: JC
authors.lastname: Olsen
authors.forename: S
authors.initials: S
authors.lastname: Kenney
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000821:virology; D002461:Cell Line, Transformed; D043525:Cytosine Deaminase; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005260:Female; D005437:Flucytosine / Q000494:pharmacology / Q000627:therapeutic use; D015774:Ganciclovir / Q000494:pharmacology / Q000627:therapeutic use; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D004854:Herpesvirus 4, Human; D006801:Humans; D016393:Lymphoma, B-Cell / Q000628:therapy*; D051379:Mice; D016513:Mice, SCID; D009700:Nucleoside Deaminases / Q000235:genetics* / Q000378:metabolism; D011355:Prodrugs / Q000494:pharmacology / Q000627:therapeutic use; D012190:Retroviridae / Q000235:genetics; D018139:Simplexvirus / Q000201:enzymology / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism
chemical_list: D011355:Prodrugs; D005437:Flucytosine; D013937:Thymidine Kinase; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase; D015774:Ganciclovir