title: Pronounced antitumor effects and tumor radiosensitization of double suicide gene therapy.
abstract: The efficacy of HSV-1 thymidine kinase (TK) and Escherichia coli cytosine deaminase (CD) suicide gene therapies as cancer treatments are currently being examined in humans. We demonstrated previously that compared to single suicide gene therapy, greater levels of targeted cytotoxicity and radiosensitization can be achieved in vitro by genetically modifying tumor cells to express CD and HSV-1 TK concomitantly, as a fusion protein. In the present study, the efficacy of the combined double suicide gene therapy/radiotherapy approach was examined in vivo. Nude mice were injected either s.c. or i.m. with 9L gliosarcoma cells expressing an E. coli CD/HSV-1 TK fusion gene. Double suicide gene therapy using 5-fluorocytosine (500 mg/kg) and ganciclovir (30 mg/kg) proved to be markedly better at delaying tumor growth and achieving a tumor cure than single suicide gene therapy, which used 5-fluorocytosine or ganciclovir administered independently. Importantly, double suicide gene therapy was highly effective against large experimental tumors (>2 cm3), reducing tumor volume an average of 99% and producing a 40% tumor cure. Moreover, double suicide gene therapy profoundly potentiated the antitumor effects of radiation. The results indicate that double suicide gene therapy, particularly when coupled with radiotherapy, may represent a highly effective means of eradicating tumors.
authors.affiliation: Departments of Radiation Oncology and Molecular Biology, Henry Ford Health System, Detroit, Michigan 48202-4689, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Rogulski
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Kolozsvary
authors.forename: J H
authors.initials: JH
authors.lastname: Kim
authors.forename: S O
authors.initials: SO
authors.lastname: Freytag
mesh_terms: D000818:Animals; D003131:Combined Modality Therapy; D005437:Flucytosine / Q000627:therapeutic use*; D015774:Ganciclovir / Q000627:therapeutic use*; D015316:Genetic Therapy; D018316:Gliosarcoma / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy* / Q000628:therapy*; D018259:Herpesvirus 1, Human / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D011355:Prodrugs / Q000627:therapeutic use; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors / Q000235:genetics*; D013997:Time Factors; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
chemical_list: D011355:Prodrugs; D011993:Recombinant Fusion Proteins; D005437:Flucytosine; D013937:Thymidine Kinase; D015774:Ganciclovir