Objective: To investigate the therapeutic effects of the murine IL-12 (mIL-12) retrovirus packaging cell line on hepatoma injected locally. Methods: The retrovirus vector encoding mIL-12 gene was constructed and transfected into packaging cell line PA317. The cells were then used to treat the rats with experimental orthotopic hepatoma at different time. The therapeutic effects, immune functions of the hosts, pathological and toxicological responses were documented. Results: the results showed that the mIL-12 retrovirus packaging cell line could significantly inhibit the growth of the hepatoma cells injected locally to the hepatoma. The early treatment made the rats survive long, while the medium or late stage treatment could prolong the life time of the rats compared with the bland control group or bland vector control group, though the rats did not survive. The number of NK cells and T cells increased significantly in the treatment group. The effects of the early treatment were superior to those of the medium and late stage treatment. Moreover, the transfection of IL-12 gene locally in the hepatoma tissue could make the hepatoma disappear from other liver lobe. This phenomenon demonstrated that IL-12 could activate the immune cells of the host to kill the untransfected tumor cells. This is very important for IL-12 to be used in gene therapy clinically. Meanwhile, the hepatoma would not recur in the rats that had survived more than 2 months from the early treatment after being re-challenged with tumor cells. Conclusion: the results showed that IL-12 gene injected locally in the hepatoma tissue could enhance the anti-tumor immunity of the host.
Objective: To investigate the synergistic anti-tumor effects of murine IL-12 gene and HSV-TK gene therapy in mice bearing liver cancer. Methods: Mouse liver cancer MM45T. Li (H-2d) cells were transfected with retroviral vector containing IL-12 gene or HSV-TK gene insert. Gene-modified liver cancer cells, MM45T. Li/IL-12 and MM45T. Li/TK, with stable expression of IL-12 and TK were obtained. Balb/c mice were inoculated subcutaneously with 2′105 MM45T. Li cells. When the tumor reached a size of 0.5-1.0 cm, a mixture of MM45T.Li/TK cells and 60Co-irradiated MM45T. Li/IL-12 cell were injected intratumoraly. Ganciclovir (GCV) was injected ip (40 mg.kg-1.d-1) for 10 days. Intratumoral injection of 60Co-irradiated MM45T. Li/IL-12 cells was repeated twice in one week apart. Mice with distant tumors were treated according to the same protocol. CTL activity of spleen cells was measured by 51Cr-release assay and phenotype of tumor infiltrating lymphocytes by immunohistochemical staining. Results: In mice treated with MM45T. Li/IL-12 or MM45T. Li/TK+GCV individually led to moderate reduction in tumor growth, but neither could eradicate the tumor completely, while in 60% of mice treated with a mixture of MM45T. Li/IL-12 and MM45T. Li/TK cells plus GCV, complete tumor regression was observed, with no tumor recurrence for two months. The growth of distant tumor was also inhibited significantly in mice similarly treated. Most of the mice received combined gene therapy plus GCV had abundant CD4+, CD8+T lymphocyte infiltration. Their CTL activity was significantly higher than in mice received single gene therapy. Conclusion Combination therapy with IL-12 gene and HSV-TK gene plus GCV is effective for mouse liver cancer.
