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 8

Exosomes produced by human cancer cell lines or metastatic cancer patients dictate Stat3 activation in MDSCs and their immunosuppressive function through TLR2 and Hsp72.

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Exosomes produced by human cancer cell lines or metastatic cancer patien...
(A) The frequency of MDSCs, defined as HLA-DR CD33+ cells, is shown in the PBMCs of healthy volunteers (H.V.) (n = 11) and metastatic cancer patients (n = 18). Each plot is an individual measure, and the horizontal bar is the mean. (B) Immunosuppressive function of MDSCs from peripheral blood of healthy volunteers and metastatic cancer patients on stimulated T cell proliferation. T cell stimulation was induced by a mixture of anti-CD2, anti-CD3, and anti-CD28 beads (n = 10). (C) PBMCs from healthy volunteers were cultured for 24 hours in medium alone or medium containing TDEs from H23 cells with or without blocking TLR2 Abs or anti-Hsp72 polyclonal Abs (pAbs). pStat3 was determined by flow cytometry on MDSC gated cells (n = 10). (D) Immunosuppressive function of MDSCs from blood of healthy volunteers either untreated or treated with TDEs from H23 cells alone or with blocking TLR2 Abs or anti-Hsp72 pAbs (n = 8). (E) PBMCs from metastatic cancer patients were incubated overnight in serum-free medium supplemented with autologous serum or PBS. pStat3 expression in gated MDSC was determined by flow cytometry. pStat3 MFI ratio between PBS and serum condition was represented. The same patients were sampled before and after 3 weeks of amiloride treatment (n = 11). (F) Immunosuppressive function of MDSCs prepared from peripheral blood of metastatic cancer patients, treated with amiloride or not treated, on T cell proliferation stimulated as in B. *P < 0.05. Error bars represent mean + SD.