ABSTRACT
The receptor NLRP3 is involved in the formation of the NLRP3 inflammasome that activates caspase-1 and mediates the release of interleukin 1ß (IL-1ß) and IL-18. Whether NLRP3 can shape immunological function independently of inflammasomes is unclear. We found that NLRP3 expression in CD4(+) T cells specifically supported a T helper type 2 (TH2) transcriptional program in a cell-intrinsic manner. NLRP3, but not the inflammasome adaptor ASC or caspase-1, positively regulated a TH2 program. In TH2 cells, NLRP3 bound the Il4 promoter and transactivated it in conjunction with the transcription factor IRF4. Nlrp3-deficient TH2 cells supported melanoma tumor growth in an IL-4-dependent manner and also promoted asthma-like symptoms. Our results demonstrate the ability of NLRP3 to act as a key transcription factor in TH2 differentiation.
Subject(s)
Carrier Proteins/immunology , Cell Differentiation/immunology , Th2 Cells/immunology , Trans-Activators/immunology , Animals , Asthma/genetics , Asthma/immunology , Asthma/metabolism , Blotting, Western , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/metabolism , Carrier Proteins/genetics , Carrier Proteins/metabolism , Cell Differentiation/genetics , Cell Line, Tumor , Female , Gene Expression Profiling , Gene Expression Regulation, Neoplastic/immunology , Inflammasomes/genetics , Inflammasomes/immunology , Inflammasomes/metabolism , Interferon Regulatory Factors/genetics , Interferon Regulatory Factors/immunology , Interferon Regulatory Factors/metabolism , Interleukin-4/genetics , Interleukin-4/immunology , Interleukin-4/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , NIH 3T3 Cells , NLR Family, Pyrin Domain-Containing 3 Protein , Neoplasms, Experimental/genetics , Neoplasms, Experimental/immunology , Neoplasms, Experimental/metabolism , Oligonucleotide Array Sequence Analysis , Promoter Regions, Genetic/genetics , Promoter Regions, Genetic/immunology , Protein Binding/immunology , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/genetics , Signal Transduction/immunology , Th2 Cells/metabolism , Trans-Activators/genetics , Trans-Activators/metabolismABSTRACT
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.
