Metastasis-associated macrophages constrain antitumor capability of natural killer cells in the metastatic site at least partially by membrane bound transforming growth factor β

Brownlie, D., Doughty-Shenton, D., Soong, D. Y.H., Nixon, C., Carragher, N. O., Carlin, L. M. and Kitamura, T. (2021) Metastasis-associated macrophages constrain antitumor capability of natural killer cells in the metastatic site at least partially by membrane bound transforming growth factor β. Journal for ImmunoTherapy of Cancer, 9(1), e001740. (doi: 10.1136/jitc-2020-001740) (PMID:33472858) (PMCID:PMC7818844)

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Abstract

Background: Metastatic breast cancer is a leading cause of cancer-related death in women worldwide. Infusion of natural killer (NK) cells is an emerging immunotherapy for such malignant tumors, although elimination of the immunosuppressive tumor environment is required to improve its efficacy. The effects of this “metastatic” tumor environment on NK cells, however, remain largely unknown. Previous studies, including our own, have demonstrated that metastasis-associated macrophages (MAMs) are one of the most abundant immune cell types in the metastatic tumor niche in mouse models of metastatic breast cancer. We thus investigated the effects of MAMs on antitumor functions of NK cells in the metastatic tumor microenvironment. Methods: MAMs were isolated from the tumor-bearing lung of C57BL/6 mice intravenously injected with E0771-LG mouse mammary tumor cells. The effects of MAMs on NK cell cytotoxicity towards E0771-LG cells were evaluated in vitro by real-time fluorescence microscopy. The effects of MAM depletion on NK cell activation, maturation, and accumulation in the metastatic lung were evaluated by flow cytometry (CD69, CD11b, CD27) and in situ hybridization (Ncr1) using colony-stimulating factor 1 (CSF-1) receptor conditional knockout (Csf1r-cKO) mice. Finally, metastatic tumor loads in the chest region of mice were determined by bioluminescence imaging in order to evaluate the effect of MAM depletion on therapeutic efficacy of endogenous and adoptively transferred NK cells in suppressing metastatic tumor growth. Results: MAMs isolated from the metastatic lung suppressed NK cell-induced tumor cell apoptosis in vitro via membrane-bound transforming growth factor β (TGF-β) dependent mechanisms. In the tumor-challenged mice, depletion of MAMs increased the percentage of activated (CD69+) and mature (CD11b+CD27–) NK cells and the number of Ncr1+ NK cells as well as NK cell-mediated tumor rejection in the metastatic site. Moreover, MAM depletion or TGF-β receptor antagonist treatment significantly enhanced the therapeutic efficacy of NK cell infusion in suppressing early metastatic tumor outgrowth. Conclusion: This study demonstrates that MAMs are a main negative regulator of NK cell function within the metastatic tumor niche, and MAM targeting is an attractive strategy to improve NK cell-based immunotherapy for metastatic breast cancer.

Item Type:Articles
Additional Information:This study was funded by a Wellcome Trust Seed Award in Science (109657/ Z/15/Z) and a Medical Research Council (MRC) Career Development Award (MR/S006982/1) to TK. LMC laboratory is supported by Cancer Research UK (A17196 and A23983). NC laboratory is supported by Cancer Research UK funding (C42454/A28596 and C42454/A24892). The MRC Centre for Reproductive Health at the University of Edinburgh receives a core funding support from MRC (MR/ N022556/1).
Keywords:Immune cell therapies and immune cell engineering, 1506, 2436, breast neoplasms, tumor microenvironment, macrophages, killer cells, natural, immunotherapy.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Nixon, Mr Colin and Carlin, Dr Leo and Brownlie, Ms Demi and Carragher, Professor Neil
Authors: Brownlie, D., Doughty-Shenton, D., Soong, D. Y.H., Nixon, C., Carragher, N. O., Carlin, L. M., and Kitamura, T.
College/School:College of Medical Veterinary and Life Sciences > School of Cancer Sciences
Journal Name:Journal for ImmunoTherapy of Cancer
Publisher:BMJ Publishing Group
ISSN:2051-1426
ISSN (Online):2051-1426
Published Online:20 January 2021
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in Journal for ImmunoTherapy of Cancer 9(1): e001740
Publisher Policy:Reproduced under a Creative Commons License

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