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Anti-PD-1/anti-CTLA-4 efficacy in melanoma brain metastases depends on extracranial disease and augmentation of CD8+ T cell trafficking.

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Date
2018-02
ICR Author
Melcher, Alan
Author
Taggart, D
Andreou, T
Scott, KJ
Williams, J
Rippaus, N
Brownlie, RJ
Ilett, EJ
Salmond, RJ
Melcher, A
Lorger, M
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Type
Journal Article
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Abstract
Inhibition of immune checkpoints programmed death 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) on T cells results in durable antitumor activity in melanoma patients. Despite high frequency of melanoma brain metastases (BrM) and associated poor prognosis, the activity and mechanisms of immune checkpoint inhibitors (ICI) in metastatic tumors that develop within the "immune specialized" brain microenvironment, remain elusive. We established a melanoma tumor transplantation model with intracranial plus extracranial (subcutaneous) tumor, mimicking the clinically observed coexistence of metastases inside and outside the brain. Strikingly, intracranial ICI efficacy was observed only when extracranial tumor was present. Extracranial tumor was also required for ICI-induced increase in CD8+ T cells, macrophages, and microglia in brain tumors, and for up-regulation of immune-regulatory genes. Combined PD-1/CTLA-4 blockade had a superior intracranial efficacy over the two monotherapies. Cell depletion studies revealed that NK cells and CD8+ T cells were required for intracranial anti-PD-1/anti-CTLA-4 efficacy. Rather than enhancing CD8+ T cell activation and expansion within intracranial tumors, PD-1/CTLA-4 blockade dramatically (∼14-fold) increased the trafficking of CD8+ T cells to the brain. This was mainly through the peripheral expansion of homing-competent effector CD8+ T cells and potentially further enhanced through up-regulation of T cell entry receptors intercellular adhesion molecule 1 and vascular adhesion molecule 1 on tumor vasculature. Our study indicates that extracranial activation/release of CD8+ T cells from PD-1/CTLA-4 inhibition and potentiation of their recruitment to the brain are paramount to the intracranial anti-PD-1/anti-CTLA-4 activity, suggesting augmentation of these processes as an immune therapy-enhancing strategy in metastatic brain cancer.
URI
https://repository.icr.ac.uk/handle/internal/1051
DOI
https://doi.org/10.1073/pnas.1714089115
Collections
  • Radiotherapy and Imaging
Subject
CD8-Positive T-Lymphocytes
T-Lymphocytes, Cytotoxic
Lymphocytes, Tumor-Infiltrating
Tumor Cells, Cultured
Animals
Mice, Inbred C57BL
Mice
Melanoma, Experimental
Brain Neoplasms
Skin Neoplasms
Antibodies, Monoclonal
Tumor Burden
Female
T-Lymphocytes, Regulatory
Granzymes
Programmed Cell Death 1 Receptor
Research team
Translational Immunotherapy
Language
eng
Date accepted
2018-02-13
License start date
2018-02
Citation
Proceedings of the National Academy of Sciences of the United States of America, 2018, 115 (7), pp. E1540 - E1549

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