Fc-dependent depletion of tumor-infiltrating regulatory T cells co-defines the efficacy of anti–CTLA-4 therapy against melanoma

TR Simpson, F Li, W Montalvo-Ortiz… - Journal of Experimental …, 2013 - rupress.org
TR Simpson, F Li, W Montalvo-Ortiz, MA Sepulveda, K Bergerhoff, F Arce, C Roddie…
Journal of Experimental Medicine, 2013rupress.org
Treatment with monoclonal antibody specific for cytotoxic T lymphocyte–associated antigen
4 (CTLA-4), an inhibitory receptor expressed by T lymphocytes, has emerged as an effective
therapy for the treatment of metastatic melanoma. Although subject to debate, current
models favor a mechanism of activity involving blockade of the inhibitory activity of CTLA-4
on both effector (T eff) and regulatory (T reg) T cells, resulting in enhanced antitumor effector
T cell activity capable of inducing tumor regression. We demonstrate, however, that the …
Treatment with monoclonal antibody specific for cytotoxic T lymphocyte–associated antigen 4 (CTLA-4), an inhibitory receptor expressed by T lymphocytes, has emerged as an effective therapy for the treatment of metastatic melanoma. Although subject to debate, current models favor a mechanism of activity involving blockade of the inhibitory activity of CTLA-4 on both effector (T eff) and regulatory (T reg) T cells, resulting in enhanced antitumor effector T cell activity capable of inducing tumor regression. We demonstrate, however, that the activity of anti–CTLA-4 antibody on the T reg cell compartment is mediated via selective depletion of T reg cells within tumor lesions. Importantly, T reg cell depletion is dependent on the presence of Fcγ receptor–expressing macrophages within the tumor microenvironment, indicating that T reg cells are depleted in trans in a context-dependent manner. Our results reveal further mechanistic insight into the activity of anti-CTLA-4–based cancer immunotherapy, and illustrate the importance of specific features of the local tumor environment on the final outcome of antibody-based immunomodulatory therapies.
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