Lung Tumor Cell-Derived Exosomes Promote M2 Macrophage Polarization.

Alexandra Pritchard,John Strenkowski,Balu K Chacko,Victor M Darley-Usmar,Jessy S Deshane,Saad Khan,Yong Wang,Sultan Tousif,Kenneth Hough

doi:10.3390/cells9051303

Abstract

Cellular cross-talk within the tumor microenvironment (TME) by exosomes is known to promote tumor progression. Tumor promoting macrophages with an M2 phenotype are suppressors of anti-tumor immunity. However, the impact of tumor-derived exosomes in modulating macrophage polarization in the lung TME is largely unknown. Herein, we investigated if lung tumor-derived exosomes alter transcriptional and bioenergetic signatures of M0 macrophages and polarize them to an M2 phenotype. The concentration of exosomes produced by p53 null H358 lung tumor cells was significantly reduced compared to A549 (p53 wild-type) lung tumor cells, consistent with p53-mediated regulation of exosome production. In co-culture studies, M0 macrophages internalized tumor-derived exosomes, and differentiated into M2 phenotype. Importantly, we demonstrate that tumor-derived exosomes enhance the oxygen consumption rate of macrophages, altering their bioenergetic state consistent with that of M2 macrophages. In vitro co-cultures of M0 macrophages with H358 exosomes demonstrated that exosome-induced M2 polarization may be p53 independent. Murine bone marrow cells and bone marrow-derived myeloid-derived suppressor cells (MDSCs) co-cultured with lewis lung carcinoma (LLC)-derived exosomes differentiated to M2 macrophages. Collectively, these studies provide evidence for a novel role for lung tumor-exosomes in M2 macrophage polarization, which then offers new therapeutic targets for immunotherapy of lung cancer.

Highlights

Lung cancer continues to be the leading cause of cancer-associated morbidity and mortality among men and women, claiming ~1.3 million deaths annually worldwide [1,2,3]
To test the hypothesis that lung tumor cell-derived exosomes re-direct macrophage polarization, we first isolated exosomes from conditioned media obtained from adenocarcinoma human alveolar basal epithelial cells (A549) and p53 null human lung cancer cells (H358) including the non-tumor epithelial cell line (HEK293) as a negative control
We demonstrate that human lung tumor cells produce epithelial cell adhesion molecule (EpCAM)+ exosomes that express exosome specific tetraspanin markers CD9, CD63, and CD81 in addition to other protein markers tumor susceptibility gene 101 (TSG-101)

Summary

Introduction

Lung cancer continues to be the leading cause of cancer-associated morbidity and mortality among men and women, claiming ~1.3 million deaths annually worldwide [1,2,3]. The predominant form of lung cancer is non-small-cell lung carcinoma (NSCLC), which accounts for about 85 percent of all lung cancers. The lung tumor microenvironment is complex and is composed of both tumor-promoting and tumor-inhibiting cells. Tumors at their developmental stage actively drive the generation of regulatory and immunosuppressive immune cells such as tumor associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and regulatory lymphocytes that promote tumor growth by suppressing anti-tumor immunity [4,5,6,7]. Abundant infiltration of macrophages occurs in the TME [8,9] and is associated with poor prognosis for cancer patients [10].

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