Transduction of cytosine deaminase gene makes rat glioma cells highly sensitive to 5-fluorocytosine.
To investigate the potential use of E. coli cytosine deaminase (CD) gene instead of the commonly used HSV-TK gene in the gene therapy of brain tumors, we constructed a retrovirus vector carrying the CD gene. We then transduced a rat glioma cell line C6 with CD gene by the retrovirus vector. Transduction of the CD gene made C6 cells become highly sensitive to the anti-fungi drug 5-fluorocytosine (5FC). IC50 for 5FC was 6,000 microM in CD-negative cells, while it was 3 microM in CD-positive cells. Mixed cellular assay showed that CD-positive cells had a strong "bystander effect" on CD-negative cells when exposed to 5FC. Significant anti-tumor effects were observed in nude mice bearing s.c. tumors derived from CD-positive cells when these animals were given 250 mg/kg 5FC twice a day for 20 consecutive days. A marked decrease in tumor weight occurred when a mixture containing 50% CD-positive and 50% CD-negative C6 cells was injected s.c., followed by 5FC treatment, suggesting the bystander effect in vivo. Concerning the pharmacokinetics of 5FC, especially its high oral bio-availability and good penetration into cerebrospinal fluid, we suppose that the combination of CD-gene transfer and 5FC oral administration may have potential use in the gene therapy of brain tumors.
Ge
K
K
Shanghai Institute of Biochemistry, Chinese Academy of Sciences, China.
Xu
L
L
Zheng
Z
Z
Xu
D
D
Sun
L
L
Liu
X
X
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology* / Q000627:therapeutic use; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D043525:Cytosine Deaminase; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005437:Flucytosine / Q000494:pharmacology* / Q000627:therapeutic use; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000008:administration & dosage; D005910:Glioma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009700:Nucleoside Deaminases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016037:Single-Blind Method; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000964:Antimetabolites, Antineoplastic; D011993:Recombinant Fusion Proteins; D005437:Flucytosine; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase