Combined Interleukin 12 and Granulocyte-macrophage Colony-stimulating Factor Gene Therapy Synergistically Suppresses Tumor Growth in the Murine Fibrosarcoma

[Background]Interleukin (IL-12) and the granulocyte-monocyte colony-stimulating factor gene (GM-CSF) have been used as immunotherapeutic agents in cancer gene therapy as they activate dendritic cells and boost anti-tumor immune responses. IL-12 and GM-CSF have different roles in anti-tumor immune response.[Objectives]The aim of present study was to investigate the anti-tumor effects of combined gene therapy with GM-CSF and IL-12 in a fibrosarcoma mouse model.[Methods]To investigate the combined therapeutic effect of GM-CSF and IL-12, WEHI 164 tumor cells were transfected with Murine GM-CSF (m-GM-CSF) and Murine IL-12 (m-IL-12) genes, using Lipofectamine. The fibrosarcoma mouse model was established by subcutaneous injection of transfected cells to Balb/c mice. Mice were sacrificed and the tumors were extracted. Tumor sizes were measured by caliper. The expression of GM-CSF, IL-12 and IFN-γ was studied by real-time PCR and immunoblotting. The expression of Ki-67 (a proliferation marker) in tumor masses was studied by immunohistochemistry staining.[Results]The tumor size was reduced in IL-12 + GM-CSF group (P < 0.0001); the results of western blotting and real-time PCR demonstrated that IL-12, GM-CSF and IFN-γ expression increased in IL-12+GM-CSF group (with a relative expression of: 2.86, 1.98, and 2.560). Immunohistochemistry staining indicated that Ki-67 expression was reduced in IL-12 + GM-CSF group.[Conclusions]Combination therapy with GM-CSF and IL-12 displayed significant therapeutic effects and represented a promising gene therapy strategy for cancer.