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 anti-GITR mAb was then combined with the intratumoral injection of the IFN-α-adenovirus vector.The CCR5 expression on Tregs was downregulated in the antibody-treated mice, which may explain the decrease of tumor-infiltrating Tregs.
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 whether the blockade of GITR-GITR ligand interaction was able to inhibit the tumor growth of Pan02 subcutaneous tumors, an agonistic anti-GITR mAb (DTA-1: 100 μg) was intraperitoneally injected into the mice with right-leg Pan02 tumors. This significantly suppressed tumor growth as compared with the control IgG injection (Fig. 2a). Then, to examine the expansion of tumor-responsive lymphocytes after the injection of GITR mAb, the splenocytes were harvested 14 days after the antibody administration, and stimulated with MMC-treated Pan02 cells or syngeneic lymphocytes. An ELISpot assay showed that the anti-GITR mAb significantly increased the number of IFN-γ-secreting cells in response to Pan02 cells but not to syngeneic lymphocytes compared with the control IgG treatment (Fig. 2b), suggesting that the blockade of GITR effectively expanded tumor-responsive immune cells.
Affiliation: Division of Gene and Immune Medicine, National Cancer Center Research Institute, Tokyo, Japan; Department of Urology, St. Marianna University, Kanagawa, Japan.