Tumor-derived extracellular vesicles regulate tumor-infiltrating regulatory T cells via the inhibitory immunoreceptor CD300a

• Published in: eLife Vol. 10
• Main Authors: Nakazawa, Yuta, Nishiyama, Nanako, Koizumi, Hitoshi, Kanemaru, Kazumasa, Nakahashi-Oda, Chigusa, Shibuya, Akira
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 09.11.2021; eLife Sciences Publications, Ltd
• Subjects: Animals; Cancer Biology; CD300a; Cell activation; Chromosomes; Dendritic cells; Endosomes; Extracellular vesicles; Extracellular Vesicles - physiology; Flow cytometry; IFN-b; Immunology and Inflammation; immunoreceptor; Immunoregulation; Internalization; Lymphatic system; Lymphocytes; Lymphocytes T; Medical prognosis; Melanoma; Mice; Mice, Inbred C57BL; MicroRNAs; Neutrophils; Receptors, Immunologic - genetics; Receptors, Immunologic - metabolism; T-Lymphocytes, Regulatory - immunology; TLR3 protein; Toll-like receptors; Transplantation; Tumor microenvironment; tumor-derived extracellular vesicles; Tumor-infiltrating lymphocytes; tumor-infiltrating regulatory T cells; Variance analysis; β-Interferon; mouse; tumor-infiltrating regulatory T cells; IFN-b; dendritic cells; CD300a; inflammation; tumor-derived extracellular vesicles; cancer biology; immunology; immunoreceptor
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.61999

Although tumor-infiltrating regulatory T (Treg) cells play a pivotal role in tumor immunity, how Treg cell activation are regulated in tumor microenvironments remains unclear. Here, we found that mice deficient in the inhibitory immunoreceptor CD300a on their dendritic cells (DCs) have increased numbers of Treg cells in tumors and greater tumor growth compared with wild-type mice after transplantation of B16 melanoma. Pharmacological impairment of extracellular vesicle (EV) release decreased Treg cell numbers in CD300a-deficient mice. Coculture of DCs with tumor-derived EV (TEV) induced the internalization of CD300a and the incorporation of EVs into endosomes, in which CD300a inhibited TEV-mediated TLR3-TRIF signaling for activation of the IFN-β-Treg cells axis. We also show that higher expression of CD300A was associated with decreased tumor-infiltrating Treg cells and longer survival time in patients with melanoma. Our findings reveal the role of TEV and CD300a on DCs in Treg cell activation in the tumor microenvironment.