Combined gene therapy with suicide gene and interleukin-12 is more efficient than therapy with one gene alone in a murine model of hepatocellular carcinoma

Background/Aims: Gene therapy has emerged as a new form of treatment for un resectable hepatocellular carcinoma (HCC). We evaluate here the effect of I L-12 and the suicide gene thymidine kinase as single agents and in combinat ion to treat experimental liver cancer, Methods: Recombinant adenoviruses expressing mouse interleukin-la (AdCMVIL- 12) or thymidine kinase of herpes simplex virus (AdCMVtk) or lacZ reporter gene (AdCMVlacZ) were constructed. The efficacy of the treatment was evalua ted in a murine HCC model based on subcutaneous implantation of liver tumor cells (BNL), Results: Transduction of BNL cells after in vitro infection with AdCMVlacZ was very low at multiplicity of infection (moi) of 100, whereas 10-15% of c ells were transduced when using moi 1000, Similarly, production of IL-12 wa s detectable only in BNL cells infected with AdCMVIL-12 at moi 1000, In vit ro infection of BNL cells with AdCMVIL-12 at moi 100 did not abrogate tumor igenicity, whereas moi 1000 re-suited in inhibition of tumor growth in all mice as well as in abrogation of tumor formation in 3 out of 8 animals. In vivo studies showed that intratumor injection of AdCMVIL-12 induced a dose- dependent effect on tumor regression. However, none of the animals exhibite d complete tumor elimination with this treatment. We observed that suppress ion of tumor growth was more intense in animals treated with the combinatio n of AdCMVIL-12 plus AdCMVtk than in animals which received AdCMVtk or AdCM VIL-12 alone. The combined treatment resulted in a significant increase in animal survival, and 25% of treated animals were free of tumor for over 100 days without recurrence of the disease. Conclusions: Combination of AdCMVIL-12 and AdCMVtk is more efficient than e ither of the two vectors alone for the treatment of the murine model of HCC used in this study.