使用腫瘤內電衝法轉染IL-6與IL-15基因可強化CTL及NK細胞毒殺作用並抑制腫瘤的生長

Abstract

Malignant cells escape from the surveillance of immune system and proliferate unrestrictedly. They cause severe alternations on host physiological activities. Malignant cells can metastasize and create further disturbances on normal functions of tissues and organs. There are three major mechanisms for tumor cell to escape: (1)Loss of recognition of foreign antigens. Tumor cells do not express MHCⅠmolecule to escape T lymphocytes recongition. (2) Decrease of cytotoxicity. Decrease the cytotoxiciity of T cells and NK cells (3)Inhibition of immune system. Tumor cells or stromal cells produce some inhibiting factors to suppress the function of immune stystem. During progression, canine transmissible venereal tumor (CTVT) secretes TGF-β to inhibit the IFN-γ induction of MHC molecules and the cytotoxicity of tumor infiltrating lymphocytes (TIL). In experimentally transplanted CTVT, it exhibits a spontaneous regression (R phase). This is due to the fact that TIL secret high concentration of IL-6 from TIL in R phase, which antagonizes the activity of tumor-derived TGF-β. After the release of TGF-β inhibition, IFN-γ can restore the MHC expression activity and T cells are activated. IL-6 also restore the cytotoxicity of NK cells. That is once inhibited by TGF-β. This research first used IL-6 gene delivery intratumorly through electroporation to antagonize TGF-β activity to promote MHC expression and then by additional IL-15 gene delivery to activate T and NK cells activities. This combinatize successfully treat this tumor in dogs. Besides, we have studied the mechanism of the combined immunogene. The combined treatment of IL-6 and IL-15 inhibited the growth or eiminated CTVT. The surface expression of MHCⅠmolecules on CTVT cells was significantly increased after gene therapy from 5.9% to 34% and MHCⅡ from 8.86% to 25.86% . This gene therapy induced more infiltrating lymphocytes from in the tumors with significant higher percentage of CD8+ T cell from 5.84% to 21.64%. This treatment also changed the cytokine profile of CTVT in favor of immune response. The mRNA levels of IL-1β, IL-8 and TNF-α were increased. But, there were no difference in TGF-β secreting activity of CTVT cells. NK cells and CTL cytotoxicity were also greatly enhanced. In conclusion, our results demonstrated that intratumoral electroporation-mediated IL-6 and IL-15 gene therapy for canine transmissible venereal tumor in the canine model efficiently tumor escape mechanism and also intensified the host immune responses. This strategy to promote MHC expression and enhance the responses on NK and other immune cells could be additional choice for cancer therapy.