Suppression of Tregs by anti-glucocorticoid induced TNF receptor antibody enhances the antitumor immunity of interferon-α gene therapy for pancreatic cancer.
Bottom Line: First we showed that an intraperitoneal administration of an agonistic anti-glucocorticoid induced TNF receptor (GITR) monoclonal antibody (mAb), which is reported to suppress the function of Tregs, significantly inhibited subcutaneous tumor growth in a murine pancreatic cancer model.The CCR5 expression on Tregs was downregulated in the antibody-treated mice, which may explain the decrease of tumor-infiltrating Tregs.The combination of Treg-suppression by GITR mAb and the tumor immunity induction by IFN-α gene therapy could be a promising therapeutic strategy for pancreatic cancer.
Affiliation: Division of Gene and Immune Medicine, National Cancer Center Research Institute, Tokyo, Japan; Department of Urology, St. Marianna University, Kanagawa, Japan.Show MeSH
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Mentions: To examine the in vivo immune reaction by the combination therapy, splenocytes were collected from the treated mice and cultured with Pan02 cells. An ELISpot assay showed that the average number of IFN-γ-producing splenocytes in response to Pan02 cells was increased in the Ad-mIFN alone group, whereas the combination therapy further increased the IFN-γ-positive spots (Fig. 4a). The numbers of spots in splenocytes co-cultured with syngeneic lymphocytes were not changed in the treated groups (Fig. 4a). In fact, all treated mice looked healthy during the course of experiments and blood chemistry showed no abnormal values in the treated mice at 4 weeks (data not shown), indicating that the combination therapy did not induce autoimmunity. To analyze the subset of activated lymphocytes, the frequency of tumor-reactive immune cells was determined by intracellular cytokine staining and flow cytometry. The percentage of CD4+ and CD8+ T cells stimulated to produce IFN-γ in response to Pan02 cells increased significantly in the mice treated by the combination therapy (Fig. 4b), indicating that this therapy enhances systemic antitumor immunity.
Affiliation: Division of Gene and Immune Medicine, National Cancer Center Research Institute, Tokyo, Japan; Department of Urology, St. Marianna University, Kanagawa, Japan.