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Blockade of CTLA-4 on both effector and regulatory T cell compartments contributes to the antitumor activity of anti-CTLA-4 antibodies.

Peggs KS, Quezada SA, Chambers CA, Korman AJ, Allison JP - J. Exp. Med. (2009)

Bottom Line: The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses.However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity.We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Immunology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

ABSTRACT
Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical negative regulator of immune responses. Uniquely among known inhibitory receptors, its genetic ablation results in a fulminating and fatal lymphoproliferative disorder. This central regulatory role led to the development of antibodies designed to block CTLA-4 activity in vivo, aiming to enhance immune responses against cancer. Despite their preclinical efficacy and promising clinical activity against late stage metastatic melanoma, the critical cellular targets for their activity remains unclear. In particular, debate has focused on whether the effector T cell (T(eff)) or regulatory T cell (T reg cell) compartment is the primary target of antibody-mediated blockade. We developed a mouse expressing human instead of mouse CTLA-4, allowing us to evaluate the independent contributions of CTLA-4 blockade of each T cell compartment during cancer immunotherapy in an in vivo model of mouse melanoma. The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses. However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity. We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

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CTLA-4 blockade of effector and regulatory compartments synergizes to produce maximal antitumor activity. (a) Experimental design. RAG2-deficient mice were reconstituted with four combinations of WT and HuTg T reg and non–T reg (CD4+ and CD8+) cells. 10 wk later, they were challenged with 20 × 103 B16/BL6 melanoma cells intradermally. From day 3, they received combination immunotherapy with Gvax and aMuCTLA-4. (b) Tumor growth curves for mice reconstituted with WT Teff and T reg cells (red), HuTg Teff and WT T reg cells (green), WT Teff and HuTg T reg cells (black), and HuTg Teff and T reg cells (blue; n = 10 per group). Error bars indicate SEM. Data represent three independent experiments. (c) Survival curves with color coding as in b. Mice were euthanized when tumor volume exceeded 350 mm3. Pooled results from three independent experiments are shown.
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fig4: CTLA-4 blockade of effector and regulatory compartments synergizes to produce maximal antitumor activity. (a) Experimental design. RAG2-deficient mice were reconstituted with four combinations of WT and HuTg T reg and non–T reg (CD4+ and CD8+) cells. 10 wk later, they were challenged with 20 × 103 B16/BL6 melanoma cells intradermally. From day 3, they received combination immunotherapy with Gvax and aMuCTLA-4. (b) Tumor growth curves for mice reconstituted with WT Teff and T reg cells (red), HuTg Teff and WT T reg cells (green), WT Teff and HuTg T reg cells (black), and HuTg Teff and T reg cells (blue; n = 10 per group). Error bars indicate SEM. Data represent three independent experiments. (c) Survival curves with color coding as in b. Mice were euthanized when tumor volume exceeded 350 mm3. Pooled results from three independent experiments are shown.

Mentions: After B16/BL6 tumor challenge, all mice received combination therapy with aMuCTLA-4 (clone 9H10, 100 µg every 3 d from day 3) and an irradiated GM-CSF–secreting B16/BL6 cellular vaccine (Gvax, 106 cells on days 3, 6, and 9; Fig. 4 a) as previously described (Quezada et al., 2006). Tumor growth in mice in which CTLA-4 blockade affected only the T reg cell compartment did not differ significantly from those in which it targeted neither population (Fig. 4 b). This is consistent with our previous experience of therapeutic T reg cell depletion with either anti-CD25 mAbs or in Foxp3-DTR transgenic mice (Quezada et al., 2008) and with the minimal impact that CTLA-4 blockade had on T reg cell function in the in vitro experiments (Fig. 2). Unicompartmental blockade of the Teff cells resulted in a significant delay in tumor growth and improved rejection rates and long-term tumor-free survival (Fig. 4, b and c). Combined survival from three experiments was 12/30 (40%; P = 0.001 compared with unicompartmental blockade of T reg cells). Blockade in this instance would also have included that of induced T reg cells, but the additional blockade of the entire T reg cell compartment markedly enhanced antitumor activity. Thus, bicompartmental blockade resulted in synergy of antitumor activity, with tumor rejection in the majority of mice and much delayed growth in the others (Fig. 4, b and c). 22/30 (73%) mice were long-term survivors (P = 0.0017 compared with unicompartmental blockade of Teff).


Blockade of CTLA-4 on both effector and regulatory T cell compartments contributes to the antitumor activity of anti-CTLA-4 antibodies.

Peggs KS, Quezada SA, Chambers CA, Korman AJ, Allison JP - J. Exp. Med. (2009)

CTLA-4 blockade of effector and regulatory compartments synergizes to produce maximal antitumor activity. (a) Experimental design. RAG2-deficient mice were reconstituted with four combinations of WT and HuTg T reg and non–T reg (CD4+ and CD8+) cells. 10 wk later, they were challenged with 20 × 103 B16/BL6 melanoma cells intradermally. From day 3, they received combination immunotherapy with Gvax and aMuCTLA-4. (b) Tumor growth curves for mice reconstituted with WT Teff and T reg cells (red), HuTg Teff and WT T reg cells (green), WT Teff and HuTg T reg cells (black), and HuTg Teff and T reg cells (blue; n = 10 per group). Error bars indicate SEM. Data represent three independent experiments. (c) Survival curves with color coding as in b. Mice were euthanized when tumor volume exceeded 350 mm3. Pooled results from three independent experiments are shown.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2722174&req=5

fig4: CTLA-4 blockade of effector and regulatory compartments synergizes to produce maximal antitumor activity. (a) Experimental design. RAG2-deficient mice were reconstituted with four combinations of WT and HuTg T reg and non–T reg (CD4+ and CD8+) cells. 10 wk later, they were challenged with 20 × 103 B16/BL6 melanoma cells intradermally. From day 3, they received combination immunotherapy with Gvax and aMuCTLA-4. (b) Tumor growth curves for mice reconstituted with WT Teff and T reg cells (red), HuTg Teff and WT T reg cells (green), WT Teff and HuTg T reg cells (black), and HuTg Teff and T reg cells (blue; n = 10 per group). Error bars indicate SEM. Data represent three independent experiments. (c) Survival curves with color coding as in b. Mice were euthanized when tumor volume exceeded 350 mm3. Pooled results from three independent experiments are shown.
Mentions: After B16/BL6 tumor challenge, all mice received combination therapy with aMuCTLA-4 (clone 9H10, 100 µg every 3 d from day 3) and an irradiated GM-CSF–secreting B16/BL6 cellular vaccine (Gvax, 106 cells on days 3, 6, and 9; Fig. 4 a) as previously described (Quezada et al., 2006). Tumor growth in mice in which CTLA-4 blockade affected only the T reg cell compartment did not differ significantly from those in which it targeted neither population (Fig. 4 b). This is consistent with our previous experience of therapeutic T reg cell depletion with either anti-CD25 mAbs or in Foxp3-DTR transgenic mice (Quezada et al., 2008) and with the minimal impact that CTLA-4 blockade had on T reg cell function in the in vitro experiments (Fig. 2). Unicompartmental blockade of the Teff cells resulted in a significant delay in tumor growth and improved rejection rates and long-term tumor-free survival (Fig. 4, b and c). Combined survival from three experiments was 12/30 (40%; P = 0.001 compared with unicompartmental blockade of T reg cells). Blockade in this instance would also have included that of induced T reg cells, but the additional blockade of the entire T reg cell compartment markedly enhanced antitumor activity. Thus, bicompartmental blockade resulted in synergy of antitumor activity, with tumor rejection in the majority of mice and much delayed growth in the others (Fig. 4, b and c). 22/30 (73%) mice were long-term survivors (P = 0.0017 compared with unicompartmental blockade of Teff).

Bottom Line: The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses.However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity.We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Department of Immunology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.

ABSTRACT
Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a critical negative regulator of immune responses. Uniquely among known inhibitory receptors, its genetic ablation results in a fulminating and fatal lymphoproliferative disorder. This central regulatory role led to the development of antibodies designed to block CTLA-4 activity in vivo, aiming to enhance immune responses against cancer. Despite their preclinical efficacy and promising clinical activity against late stage metastatic melanoma, the critical cellular targets for their activity remains unclear. In particular, debate has focused on whether the effector T cell (T(eff)) or regulatory T cell (T reg cell) compartment is the primary target of antibody-mediated blockade. We developed a mouse expressing human instead of mouse CTLA-4, allowing us to evaluate the independent contributions of CTLA-4 blockade of each T cell compartment during cancer immunotherapy in an in vivo model of mouse melanoma. The data show that although blockade on effector cells significantly improves tumor protection, unicompartmental blockade on regulatory cells completely fails to enhance antitumor responses. However, concomitant blockade of both compartments leads to a synergistic effect and maximal antitumor activity. We conclude that the combination of direct enhancement of T(eff) cell function and concomitant inhibition of T reg cell activity through blockade of CTLA-4 on both cell types is essential for mediating the full therapeutic effects of anti-CTLA-4 antibodies during cancer immunotherapy.

Show MeSH
Related in: MedlinePlus