title: Antibiotic-mediated chemoprotection enhances adaptation of E. coli PNP for herpes simplex virus-based glioma therapy.
abstract: The E. coli PNP suicide gene sensitizes solid tumors to nucleoside prodrugs, such as 6-methylpurine-2'-deoxyriboside (MeP-dR). In this study using lentiviral, MuLv, and HSV-based gene transfer, we quantified thresholds for inhibition of tumor growth and bystander killing by E. coli PNP and tested the role of intestinal flora in this process. Regressions of human glioma tumors following retroviral transduction exhibited dose dependence on both the level of PNP expression and the dose of MeP-dR administered, including strong tumor inhibition when 90-99% bystander cells comprised the tumor mass. A replication competent, non-neurovirulent herpes simplex virus (HSV) deficient in both copies of the gamma-1 34.5 gene was next engineered to express E. coli PNP under the egr-1 promoter (HSV-PNP). HSV-PNP injected intratumorally (17 million pfu/0.05 ml) in nude mice bearing 300 mg human glioma flank tumors produced a delay in tumor growth (approximately 24 days delay to one doubling). MeP-dR treatment after antibiotic therapy (to eliminate enteric flora encoding PNP enzymes) resulted in antitumor enhancement, with arrest of tumor growth (delay to doubling >50 days). Bystander killing of the magnitude described here has been difficult to accomplish with other suicide genes, such as HSV-tk or cytosine deaminase. The results establish a model for applying E. coli PNP to HSV treatment of glioma.
authors.affiliation: Department of Surgery, University of Alabama at Birmingham, AL 35294, USA.
authors.forename: Suman
authors.initials: S
authors.lastname: Bharara
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Sorscher
authors.forename: G Yancey
authors.initials: GY
authors.lastname: Gillespie
authors.forename: J Russell
authors.initials: JR
authors.lastname: Lindsey
authors.forename: Jeong S
authors.initials: JS
authors.lastname: Hong
authors.forename: Kimberly V
authors.initials: KV
authors.lastname: Curlee
authors.forename: Paula W
authors.initials: PW
authors.lastname: Allan
authors.forename: V K
authors.initials: VK
authors.lastname: Gadi
authors.forename: Sherrie A
authors.initials: SA
authors.lastname: Alexander
authors.forename: John A
authors.initials: JA
authors.lastname: Secrist
authors.forename: William B
authors.initials: WB
authors.lastname: Parker
authors.forename: William R
authors.initials: WR
authors.lastname: Waud
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004926:Escherichia coli / Q000235:genetics; D018014:Gene Transfer Techniques; D041722:Genes, Transgenic, Suicide / Q000235:genetics*; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics / Q000627:therapeutic use; D005856:Germ-Free Life; D005910:Glioma / Q000235:genetics / Q000628:therapy*; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D011355:Prodrugs / Q000378:metabolism / Q000627:therapeutic use; D011684:Purine Nucleosides / Q000378:metabolism / Q000627:therapeutic use*; D011683:Purine-Nucleoside Phosphorylase / Q000235:genetics / Q000378:metabolism* / Q000627:therapeutic use*; D018139:Simplexvirus / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D011355:Prodrugs; D011684:Purine Nucleosides; C032885:6-methylpurine 2'-deoxyriboside; D011683:Purine-Nucleoside Phosphorylase