Membrane-associated Hsp72 from tumor-derived exosomes mediates STAT3-dependent immunosuppressive function of mouse and human myeloid-derived suppressor cells
Fanny Chalmin, … , Cédric Rébé, François Ghiringhelli
Fanny Chalmin, … , Cédric Rébé, François Ghiringhelli
Published January 19, 2010
Citation Information: J Clin Invest. 2010;120(2):457-471. https://doi.org/10.1172/JCI40483.
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Research Article Immunology

Membrane-associated Hsp72 from tumor-derived exosomes mediates STAT3-dependent immunosuppressive function of mouse and human myeloid-derived suppressor cells

Abstract

Myeloid-derived suppressor cells (MDSCs) have been identified in humans and mice as a population of immature myeloid cells with the ability to suppress T cell activation. They accumulate in tumor-bearing mice and humans and have been shown to contribute to cancer development. Here, we have isolated tumor-derived exosomes (TDEs) from mouse cell lines and shown that an interaction between TDE-associated Hsp72 and MDSCs determines the suppressive activity of the MDSCs via activation of Stat3. In addition, tumor-derived soluble factors triggered MDSC expansion via activation of Erk. TDE-associated Hsp72 triggered Stat3 activation in MDSCs in a TLR2/MyD88-dependent manner through autocrine production of IL-6. Importantly, decreasing exosome production using dimethyl amiloride enhanced the in vivo antitumor efficacy of the chemotherapeutic drug cyclophosphamide in 3 different mouse tumor models. We also demonstrated that this mechanism is relevant in cancer patients, as TDEs from a human tumor cell line activated human MDSCs and triggered their suppressive function in an Hsp72/TLR2-dependent manner. Further, MDSCs from cancer patients treated with amiloride, a drug used to treat high blood pressure that also inhibits exosome formation, exhibited reduced suppressor functions. Collectively, our findings show in both mice and humans that Hsp72 expressed at the surface of TDEs restrains tumor immune surveillance by promoting MDSC suppressive functions.

Authors

Fanny Chalmin, Sylvain Ladoire, Grégoire Mignot, Julie Vincent, Mélanie Bruchard, Jean-Paul Remy-Martin, Wilfrid Boireau, Alain Rouleau, Benoit Simon, David Lanneau, Aurélie De Thonel, Gabriele Multhoff, Arlette Hamman, François Martin, Bruno Chauffert, Eric Solary, Laurence Zitvogel, Carmen Garrido, Bernhard Ryffel, Christophe Borg, Lionel Apetoh, Cédric Rébé, François Ghiringhelli

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Figure 4

IL-6–induced pStat3 expression in MDSCs is dependent on the TLR2/MyD88 pathway.

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IL-6–induced pStat3 expression in MDSCs is dependent on the TLR2/MyD88 p...
Purified MDSCs from WT or TLR2-, TLR4-, MyD88-, and Trif-deficient C57BL/6 tumor-free mice were cultured for 24 hours in complete medium supplemented or not with TDEs. IL-6 concentration in the supernatant was determined by ELISA (A), and pStat3 expression in cells was determined by FACS analysis (B). Data represent mean ± SD. (C) WT C57BL/6 mice or TLR2-, TLR4-, MyD88-, and Trif-deficient mice were s.c. injected with 1 × 106 EL4 cells. 3 weeks later, spleen cells were harvested, MDSC percentage was determined in spleen (denoted in left panels), and pStat3 expression was determined by FACS analysis on MDSC gated cells (right panel). (D) 2 × 105 OT-1 cells were labeled with CFSE, loaded with 10 μg/ml of SIINFEKL, and cultured 3 days alone or with different ratios of MDSCs from EL4 tumor-bearing WT mice or from EL4 tumor-bearing TLR2-deficient mice. Percentage of OT-1 proliferating cells was determined by flow cytometry. Each experiment was done in duplicate (n = 3 mice per group). (E) WT or TLR2–/– mice were injected s.c. with EL4 cells, and tumor growth was monitored. *P < 0.05.