Adenovirus mediated prostate specific enzyme prodrug gene therapy using prostate specific antigen promoter enhanced by the Cre-loxP system.
OBJECTIVE
Tissue or tumor specific gene delivery is crucial for achieving successful results in suicide gene therapy. Prostate specific antigen (PSA) promoter is known to be highly specific in prostate tissue but its promoter activity is much weaker than that of constitutive viral promoters. In the current study we enhanced PSA promoter activity by combining it with the Cre-loxP system. We also applied this system to adenovirus mediated suicide gene therapy with the cytosine deaminase (CD) gene.


METHODS
The Cre-loxP DNA recombination system was used to enhance PSA promoter. A plasmid with the PSA promoter-enhancer combination was constructed to drive Cre recombinase. Another plasmid contained the cytomegalovirus promoter-loxP-flanked stop signal-luciferase gene. LNCaP human prostate cancer cells were co-transfected with these 2 plasmids and luciferase activity was measured to assess promoter activities. Adenoviral vectors with the CD suicide gene were constructed in similar fashion and tested in LNCaP cells in in vitro/in vivo prostate cancer models.


RESULTS
Promoter activity of the combined PSA promoter/enhancer and Cre-loxP system was 3 times stronger than that of PSA promoter/enhancer alone. It was further enhanced 7-fold in the presence of testosterone. Application of this system to CD suicide gene therapy by adenoviral vectors inhibited subcutaneous LNCaP tumor growth in nude mice.


CONCLUSIONS
Combining the Cre-loxP system with PSA promoter/enhancer amplified promoter activity and was found to inhibit the growth of PSA producing prostate cancer cells in vivo.
Yoshimura
Ichiro
I
Department of Urology, National Defence Medical College, Tokorozawa, Saitama, Japan.
Ikegami
Shusei
S
Suzuki
Satoshi
S
Tadakuma
Takushi
T
Hayakawa
Masamichi
M
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000964:Antimetabolites, Antineoplastic; D043525:Cytosine Deaminase; D004742:Enhancer Elements, Genetic; D005437:Flucytosine / Q000627:therapeutic use*; D005472:Fluorouracil / Q000627:therapeutic use*; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D019426:Integrases / Q000235:genetics*; D008156:Luciferases / Q000235:genetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009700:Nucleoside Deaminases / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D011355:Prodrugs / Q000627:therapeutic use*; D011401:Promoter Regions, Genetic; D017430:Prostate-Specific Antigen / Q000235:genetics*; D011471:Prostatic Neoplasms / Q000628:therapy*; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000628:therapy; D014764:Viral Proteins / Q000235:genetics*
D000964:Antimetabolites, Antineoplastic; D011355:Prodrugs; D014764:Viral Proteins; D005437:Flucytosine; D008156:Luciferases; C045073:Cre recombinase; D019426:Integrases; D017430:Prostate-Specific Antigen; D009700:Nucleoside Deaminases; D043525:Cytosine Deaminase; D005472:Fluorouracil