Glucocorticoid-Induced TNF Receptor Family Related Gene Activation Overcomes Tolerance/Ignorance to Melanoma Differentiation Antigens and Enhances Antitumor Immunity

Abstract

Glucocorticoid-induced TNF receptor family related protein (GITR) is present on many different cell types. Previous studies have shown that in vivo administration of an anti-GITR agonist mAb (DTA-1) inhibits regulatory T cells (Treg)-dependent suppression and enhances T cell responses. In this study, we show that administration of DTA-1 induces >85% tumor rejection in mice challenged with B16 melanoma. Rejection requires CD4+, CD8+, and NK1.1+ cells and is dependent on IFN-γ and Fas ligand and independent of perforin. Depletion of Treg via anti-CD25 treatment does not induce B16 rejection, whereas 100% of the mice depleted of CD25+ cells and treated with DTA-1 reject tumors, indicating a predominant role of GITR on effector T cell costimulation rather than on Treg modulation. T cells isolated from DTA-1-treated mice challenged with B16 are specific against B16 and several melanoma differentiation Ags. These mice develop memory against B16, and a small proportion of them develop mild hypopigmentation. Consistent with previous studies showing that GITR stimulation increases Treg proliferation in vitro, we found in our model that GITR stimulation expanded the absolute number of FoxP3+ cells in vivo. Thus, we conclude that overall, GITR stimulation overcomes self-tolerance/ignorance and enhances T cell-mediated antitumor activity with minimal autoimmunity.

Dendritic cells engineered to secrete anti-GITR antibodies are effective adjuvants to dendritic cell-based immunotherapy

“…22,24,[26][27][28][29][30] These reports, which show enhancement of tumor responses using anti-GITR mAb delivered systemically, use 0.5-1 mg of mAb to see an anti-tumor effect, and studies in poorly immunogenic and very aggressive tumor models such as B16 melanoma routinely use 1 mg of anti-GITR mAb. 22,24,26,28 Mice were implanted with B16/F10.9 tumor cells and immunized once with TRP-2 RNA-transfected DC in conjunction with either DC transfected with control IgG RNA or anti-GITR H þ L RNA. Alternatively, mice were immunized with TRP-2 RNA-transfected DC in conjunction with 1 mg of control antibody or anti-GITR mAb injected intraperitoneally.…”

“…13,14,21 An antibody that has been extensively tested in mice targets the glucocorticoid-induced tumor necrosis factor receptor (GITR). [22][23][24][25][26][27][28] GITR, a member of the tumor necrosis factor receptor superfamily, is constitutively expressed on Tregs but it is also expressed at low levels on multiple immune cells, including T cells, natural killer cells and B cells in which it is upregulated on activation. 7,23,[29][30][31] Treatment of mice with an agonistic anti-GITR mAb (anti-GITR), clone DTA-1, alone has been shown to cause exacerbated autoimmune disease in susceptible mice and enhanced anti-viral and anti-tumor immune responses in disease-bearing animals.…”

“…7,23,[29][30][31] Treatment of mice with an agonistic anti-GITR mAb (anti-GITR), clone DTA-1, alone has been shown to cause exacerbated autoimmune disease in susceptible mice and enhanced anti-viral and anti-tumor immune responses in disease-bearing animals. 22,[24][25][26][27][28] When combined with DNA immunization against xenogeneic melanoma-related antigens, DTA-1-treated mice showed increased T-cell responses and protection from tumor challenge. 22 Interestingly, these mice also showed an increase in autoimmune hypopigmentation.…”

An isoleucine-zipper motif enhances costimulation of human soluble trimeric GITR ligand

“…3,[9][10][11][12][13][14] Interestingly, hsGITRL displays biological activity by forming multiple oligomerization. 16 The ILZ motif has been shown to form trimers in solution and many soluble TNF/TNF receptor superfamilies modified by an ILZ motif can form stable trimeric or multiple oligomerization states.…”

“…GITR triggered by soluble GITRL, cell surface GITRL or anti-GITR monoclonal antibody (mAb) (DTA-1) abrogates regulatory Tcell suppression 3,4,7,8 and results in exacerbation of organ-specific autoimmune diseases, 3,9,10 , enhancement of antitumor immunity and the immunity to viral pathogens. [11][12][13] Thus, the functional interaction between GITR and GITRL is important for regulatory T cells to induce immune tolerance and regulate homeostasis. 14,15 Structure analysis has revealed that human soluble GITRL (hsGITRL) increases its receptor-binding affinity and enhances costimulatory activity through self-assembly into a trimer.…”