Adenovirus-mediated interleukin-12 gene transfer combined with cytosine deaminase followed by 5-fluorocytosine treatment exerts potent antitumor activity in Renca tumor-bearing mice.
BACKGROUND
Therapeutic gene transfer affords a clinically feasible and safe approach to cancer treatment but a more effective modality is needed to improve clinical outcomes. Combined transfer of therapeutic genes with different modes of actions may be a means to this end. Interleukin-12 (IL-12), a heterodimeric immunoregulatory cytokine composed of covalently linked p35 and p40 subunits, has antitumor activity in animal models. The enzyme/prodrug strategy using cytosine deaminase (CD) and 5-fluorocytosine (5-FC) has been used for cancer gene therapy. We have evaluated the antitumor effect of combining IL-12 with CD gene transfer in mice bearing renal cell carcinoma (Renca) tumors.


METHODS
Adenoviral vectors were constructed encoding one or both subunits of murine IL-12 (Ad.p35, Ad.p40 and Ad.IL-12) or cytosine deaminase (Ad.CD). The functionality of the IL-12 or CD gene products expressed from these vectors was validated by splenic interferon (IFN)-gamma production or viability assays in cultured cells. Ad.p35 plus Ad.p40, or Ad.IL-12, with or without Ad.CD, were administered (single-dose) intratumorally to Renca tumor-bearing mice. The animals injected with Ad.CD also received 5-FC intraperitoneally. The antitumor effects were then evaluated by measuring tumor regression, mean animal survival time, splenic natural killer (NK) cell activity and IFN-gamma production.


RESULTS
The inhibition of tumor growth in mice treated with Ad.p35 plus Ad.p40 and Ad.CD, followed by injection of 5-FC, was significantly greater than that in mice treated with Ad.CD/5-FC, a mixture of Ad.p35 plus Ad.p40, or Ad.GFP (control). The combined gene transfer increased splenic NK cell activity and IFN-gamma production by splenocytes. Ad.CD/5-FC treatment significantly increased the antitumor effect of Ad.IL-12 in terms of tumor growth inhibition and mean animal survival time.


CONCLUSIONS
The results suggest that adenovirus-mediated IL-12 gene transfer combined with Ad.CD followed by 5-FC treatment may be useful for treating cancers.
Hwang
Kyung-Sun
KS
Laboratory of Gene Therapy and Virology, Korea Research Institute of Bioscience and Biotechnology, Yusong, Daejeon, Republic of Korea. hwangksun@hanmail.net
Cho
Won-Kyung
WK
Yoo
Jinsang
J
Yun
Hwan-Jung
HJ
Kim
Samyong
S
Im
Dong-Soo
DS
D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D043525:Cytosine Deaminase / Q000494:pharmacology*; D018076:DNA, Complementary / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000378:metabolism; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology*; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000235:genetics* / Q000378:metabolism; D007680:Kidney Neoplasms / Q000378:metabolism; D007694:Killer Cells, Natural / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000235:genetics / Q000628:therapy*; D009374:Neoplasms, Experimental / Q000235:genetics / Q000628:therapy; D011355:Prodrugs / Q000494:pharmacology; D013154:Spleen / Q000378:metabolism; D013997:Time Factors; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D018076:DNA, Complementary; D011355:Prodrugs; D049452:Green Fluorescent Proteins; D018664:Interleukin-12; D007371:Interferon-gamma; D043525:Cytosine Deaminase; D005472:Fluorouracil