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Proc Natl Acad Sci U S A. 2019 Feb 15. pii: 201819473. doi: 10.1073/pnas.1819473116. [Epub ahead of print]

Reactive oxygen species modulate macrophage immunosuppressive phenotype through the up-regulation of PD-L1.

Author information

1
The Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, ON M5G 2M9, Canada.
2
Molecular Biotechnology Center, University of Turin, 10126 Turin, Italy.
3
Breast Cancer and Systems Biology Laboratory, Program Against Cancer Therapeutic Resistance, Catalan Institute of Oncology (Oncobell), Bellvitge Institute for Biomedical Research, L'Hospitalet del Llobregat, 08908 Barcelona, Catalonia, Spain.
4
The Campbell Family Institute for Breast Cancer Research, Princess Margaret Cancer Centre, Toronto, ON M5G 2M9, Canada; tak.mak@uhnresearch.ca paola.cappello@unito.it Chiara.Gorrini@uhnresearch.ca.
5
Molecular Biotechnology Center, University of Turin, 10126 Turin, Italy; tak.mak@uhnresearch.ca paola.cappello@unito.it Chiara.Gorrini@uhnresearch.ca.
6
Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy.

Abstract

The combination of immune checkpoint blockade with chemotherapy is currently under investigation as a promising strategy for the treatment of triple negative breast cancer (TNBC). Tumor-associated macrophages (TAMs) are the most prominent component of the breast cancer microenvironment because they influence tumor progression and the response to therapies. Here we show that macrophages acquire an immunosuppressive phenotype and increase the expression of programmed death ligand-1 (PD-L1) when treated with reactive oxygen species (ROS) inducers such as the glutathione synthesis inhibitor, buthionine sulphoximine (BSO), and paclitaxel. Mechanistically, these agents cause accumulation of ROS that in turn activate NF-κB signaling to promote PD-L1 transcription and the release of immunosuppressive chemokines. Systemic in vivo administration of paclitaxel promotes PD-L1 accumulation on the surface of TAMS in a mouse model of TNBC, consistent with in vitro results. Combinatorial treatment with paclitaxel and an anti-mouse PD-L1 blocking antibody significantly improved the therapeutic efficacy of paclitaxel by reducing tumor burden and increasing the number of tumor-associated cytotoxic T cells. Our results provide a strong rationale for the use of anti-PD-L1 blockade in the treatment of TNBC patients. Furthermore, interrogation of chemotherapy-induced PD-L1 expression in TAMs is warranted to define appropriate patient selection in the use of PD-L1 blockade.

KEYWORDS:

chemotherapy; immune suppression; macrophages; programmed death ligand-1; reactive oxygen species

PMID:
30770442
PMCID:
PMC6410837
[Available on 2019-09-05]
DOI:
10.1073/pnas.1819473116

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