Inhibition of PPARγ in myeloid-lineage cells induces systemic inflammation, immunosuppression, and tumorigenesis.

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Adenocarcinoma, Animals, Blotting, Western, Bone Marrow Transplantation, Cell Proliferation, Chromatin Immunoprecipitation, Enzyme-Linked Immunosorbent Assay, Flow Cytometry, Genes, Dominant, Hematopoietic Stem Cells, Humans, Immunoenzyme Techniques, Immunosuppression, Inflammation, Interleukin-1beta, Interleukin-6, Liver Neoplasms, Lung Neoplasms, Lymph Nodes, Male, Mice, Mice, Transgenic, Myeloid Cells, NF-kappa B, PPAR gamma, Proto-Oncogene Proteins c-kit, RNA, Messenger, Real-Time Polymerase Chain Reaction, Receptors, Interleukin-7, STAT3 Transcription Factor, Sarcoma, Signal Transduction, Splenic Neoplasms, T-Lymphocytes, Tumor Necrosis Factor-alpha, Up-Regulation

JAX Source

Blood 2012 Jan 5; 119(1):115-26.




Peroxisome proliferator-activated receptor-γ (PPARγ) is an anti-inflammatory molecule. To study its biologic function in myeloid cells, dominant-negative PPARγ (dnPPARγ) was overexpressed in a myeloid-specific bitransgenic mouse model. In this bitransgenic system, overexpression of the dnPPARγ-Flag fusion protein in myeloid-lineage cells abnormally elevated frequencies and total numbers of IL-7Rα(-)Lin(-)c-Kit(+)Sca-1(-), Lin(-)/Scal(+)/c-Kit(+), common myeloid, and granulocyte-monocyte progenitor populations in the BM. dnPPARγ overexpression led to up-regulation of IL-1β, IL-6, and TNFα in the blood plasma. As a result, CD11b(+)Ly6G(+) cells were systemically increased in association with activation of Stat3, NF-κB, Erk1/2, and p38 molecules. Myeloid-derived suppressor cells (MDSCs) inhibited the proliferation and lymphokine production of wild-type CD4+ T cells in vitro. CD4+ T cells from doxycycline-treated bitransgenic mice displayed reduced proliferation and lymphokine release. Both CD4+ and CD8+ T-cell populations were decreased in doxycycline-treated bitransgenic mice. Multiple forms of carcinoma and sarcoma in the lung, liver, spleen, and lymph nodes were observed in doxycycline-treated bitransgenic mice. BM transplantation revealed that a myeloid-autonomous defect was responsible for MDSC expansion, immunosuppression, and tumorigenesis in these mice. These studies suggest that anti-inflammatory PPARγ in myeloid-lineage cells plays a key role in controlling pro-inflammatory cytokine synthesis, MDSC expansion, immunosuppression, and the development of cancer.