Characterization and Comparison of GITR Expression in Solid Tumors

Abstract

Purpose: Determine the differential effect of a FcgR-binding, mIgG2a anti-GITR antibody in mouse tumor models, and characterize the tumor microenvironment for the frequency of GITR expression in T-cell subsets from seven different human solid tumors.Experimental Design: For mouse experiments, wild-type C57BL/6 mice were subcutaneously injected with MC38 cells or B16 cells, and BALB/c mice were injected with CT26 cells. Mice were treated with the anti-mouse GITR agonist antibody 21B6, and tumor burden and survival were monitored. GITR expression was evaluated at the single-cell level using flow cytometry (FC). A total of 213 samples were evaluated for GITR expression by IHC, 63 by FC, and 170 by both in seven human solid tumors: advanced hepatocellular carcinoma, non-small cell lung cancer (NSCLC), renal cell carcinoma, pancreatic carcinoma, head and neck carcinoma, melanoma, and ovarian carcinoma.Results: The therapeutic benefit of 21B6 was greatest in CT26 followed by MC38, and was least in the B16 tumor model. The frequency of CD8 T cells and effector CD4 T cells within the immune infiltrate correlated with response to treatment with GITR antibody. Analysis of clinical tumor samples showed that NSCLC, renal cell carcinoma, and melanoma had the highest proportions of GITR-expressing cells and highest per-cell density of GITR expression on CD4 þ Foxp3 þ T regulatory cells. IHC and FC data showed similar trends with a good correlation between both techniques.Conclusions: Human tumor data suggest that NSCLC, renal cell carcinoma, and melanoma should be the tumor subtypes prioritized for anti-GITR therapy development.

The Role of GITR/GITRL Interaction in Autoimmune Diseases

“…GITR is constitutively expressed in Treg cells and is critical for the development and activity of Treg cells ( 2 , 8 , 25 ). The expression of GITR in Tregs can be up-regulated after activation or in tumor microenvironment, and the level of GITR usually positively correlates with the immunosuppressive function of Tregs ( 26 , 27 ). GITR engagement in Treg cells can have multiple distinct effects.…”

New emerging targets in cancer immunotherapy: the role of GITR

“…34 Vence et al confirmed that tumours with high expression of CD8 + and CD4 + , after GITR mAb treatment, have the better response, mainly lung cancer, renal cancer and melanoma. 25 Moreover, preliminary results showed a better suppression of tumour growth with intratumour compared with intravenous injection. In fact, the intratumour injection was able to induce a systemic antitumour immune reaction, exerting its effect on injected and on un-injected tumours.…”

“…[21][22][23][24] Importantly, GITR is not expressed on the tumour itself, but it is expressed on tumour-infiltrating lymphocytes (TILs) of several human cancer types including lung cancers, renal cell carcinoma, head and neck carcinoma and melanoma. 25 The most widely used molecules to trigger GITR are agonist antibodies like DTA-1 (a rat IgG2b) 5 or recombinant version of GITRL, like GITR-Fc.…”

“…Importantly, GITR is not expressed on the tumour itself, but it is expressed on tumour-infiltrating lymphocytes (TILs) of several human cancer types including lung cancers, renal cell carcinoma, head and neck carcinoma and melanoma. 25 …”

“…Vence et al confirmed that tumours with high expression of CD8 + and CD4 + , after GITR mAb treatment, have the better response, mainly lung cancer, renal cancer and melanoma. 25 …”