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Stat6 is known to drive macrophage M2 polarization. However, how macrophage polarization is fine-tuned by Stat6 is poorly understood. Here, we find that Lys383 of Stat6 is acetylated by the acetyltransferase CREB-binding protein (CBP) during macrophage activation to suppress macrophage M2 polarization. Mechanistically, Trim24, a CBP-associated E3 ligase, promotes Stat6 acetylation by catalyzing CBP ubiquitination at Lys119 to facilitate the recruitment of CBP to Stat6. Loss of Trim24 inhibits Stat6 acetylation and thus promotes M2 polarization in both mouse and human macrophages, potentially compromising antitumor immune responses. By contrast, Stat6 mediates the suppression of TRIM24 expression in M2 macrophages to contribute to the induction of an immunosuppressive tumor niche. Taken together, our findings establish Stat6 acetylation as an essential negative regulatory mechanism that curtails macrophage M2 polarization. Stat6 promotes M2 macrophage polarization. Here the authors characterize Trim24-CBP-Stat6 circuit regulating M2 macrophage polarization via Stat6 acetylation, and show it contributes to pro-tumorigenic macrophage activity in mice.

Chronic inflammation and an immunosuppressive microenvironment promote prostate cancer (PCa) progression and diminish the response to immune checkpoint blockade (ICB) therapies. However, it remains unclear how and to what extent these two events are coordinated. Here, we show that ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, functions downstream of inflammation-induced IKKβ activation to shape the immunosuppressive tumor microenvironment (TME). Prostate-specific deletion of Arid1a cooperates with Pten loss to accelerate prostate tumorigenesis. We identify polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) as the major infiltrating immune cell type that causes immune evasion and reveal that neutralization of PMN-MDSCs restricts the progression of Arid1a -deficient tumors. Mechanistically, inflammatory cues activate IKKβ to phosphorylate ARID1A, leading to its degradation via β-TRCP. ARID1A downregulation in turn silences the enhancer of A20 deubiquitinase, a critical negative regulator of NF-κB signaling, and thereby unleashes CXCR2 ligand-mediated MDSC chemotaxis. Importantly, our results support the therapeutic strategy of anti-NF-κB antibody or targeting CXCR2 combined with ICB for advanced PCa. Together, our findings highlight that the IKKβ/ARID1A/NF-κB feedback axis integrates inflammation and immunosuppression to promote PCa progression. The accumulation of myeloid derived suppressor cells (MDSC) has been associated with prostate cancer progression and castration resistance. Here the authors show that loss of ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, results in polymorphonuclear-MDSC infiltration and cooperates with Pten loss to accelerate prostate tumorigenesis.

Background Characterizing the unique immune microenvironment of each tumor is of great importance for better predicting prognosis and guiding cancer immunotherapy. However, the unique features of the immune microenvironment of triple negative breast cancer (TNBC) compared with other subtypes of breast cancer remain elusive. Therefore, we aimed to depict and compare the immune landscape among TNBC, human epidermal growth factor receptor 2‐positive (HER2+) breast cancer, and luminal‐like breast cancer. Methods Single‐cell RNA sequencing (scRNA‐seq) was performed on CD45+ immune cells isolated from human normal breast tissues and primary breast tumors of various subtypes. By analyzing the scRNA‐seq data, immune cell clusters were identified and their proportions as well as transcriptome features were compared among TNBC, human HER2+ breast cancer, and luminal‐like breast cancer. Pseudotime and cell‐cell communication analyses were also conducted to characterize the immune microenvironment. Results ScRNA‐seq data of 117,958 immune cells were obtained and 31 immune clusters were identified. A unique immunosuppressive microenvironment in TNBC was decoded as compared to that in HER2+ or luminal‐like breast cancer, which was characterized by higher proportions of regulatory T cells (Tregs) and exhausted CD8+ T cells and accompanied by more abundant plasma cells. Tregs and exhausted CD8+T cells in TNBC exhibited increased immunosuppression signature and dysfunctional scores. Pseudotime analyses showed that B cells tended to differentiate to plasma cells in TNBC. Cell‐cell communication analyses indicated that these unique features are fostered by the diversified T cell‐B cell crosstalk in TNBC. Based on the T cell‐B cell crosstalk, a prognostic signature was established that could effectively predict the prognosis status for patients with TNBC. Additionally, it was found that TNBC had a higher proportion of cytotoxic natural killer (NK) cells, whereas HER2+ or luminal‐like breast cancer lost this feature, suggesting that HER2+ or luminal‐like breast cancer, but not TNBC, may benefit from NK‐based immunotherapy. Conclusions This study identified a distinct immune feature fostered by T cell‐B cell crosstalk in TNBC, which provides better prognostic information and effective therapeutic targets for breast cancer.

IFN-γ-stimulated MHC class I (MHC-I) antigen presentation underlies the core of antitumor immunity. However, sustained IFN-γ signaling also enhances the programmed death ligand 1 (PD-L1) checkpoint pathway to dampen antitumor immunity. It remains unclear how these opposing effects of IFN-γ are regulated. Here, we report that loss of the histone dimethyltransferase WHSC1 impaired the antitumor effect of IFN-γ signaling by transcriptional downregulation of the MHC-I machinery without affecting PD-L1 expression in colorectal cancer (CRC) cells. Whsc1 loss promoted tumorigenesis via a non-cell-autonomous mechanism in an Apcmin/+ mouse model, CRC organoids, and xenografts. Mechanistically, we found that the IFN-γ/STAT1 signaling axis stimulated WHSC1 expression and, in turn, that WHSC1 directly interacted with NLRC5 to promote MHC-I gene expression, but not that of PD-L1. Concordantly, silencing Whsc1 diminished MHC-I levels, impaired antitumor immunity, and blunted the effect of immune checkpoint blockade. Patient cohort analysis revealed that WHSC1 expression positively correlated with enhanced MHC-I expression, tumor-infiltrating T cells, and favorable disease outcomes. Together, our findings establish a tumor-suppressive function of WHSC1 that relays IFN-γ signaling to promote antigen presentation on CRC cells and provide a rationale for boosting WHSC1 activity in immunotherapy.

Macrophages, dendritic cells and other innate immune cells are involved in inflammation and host defense against infection. Metabolic shifts in mitochondrial dynamics may be involved in Toll-like receptor agonist-mediated inflammatory responses and immune cell polarization. However, whether the mitochondrial morphology in myeloid immune cells affects anti-tumor immunity is unclear. Here we show that FAM73b, a mitochondrial outer membrane protein, has a pivotal function in Toll-like receptor-regulated mitochondrial morphology switching from fusion to fission. Switching to mitochondrial fission via ablation of Fam73b (also known as Miga2 ) promotes IL-12 production. In tumor-associated macrophages, this switch results in T-cell activation and enhances anti-tumor immunity. We also show that the mitochondrial morphology affects Parkin expression and its recruitment to mitochondria. Parkin controls the stability of the downstream CHIP–IRF1 axis through proteolysis. Our findings identify mechanisms associated with mitochondrial dynamics that control anti-tumor immune responses and that are potential targets for cancer immunotherapy. Macrophage metabolism controls differentiation and subsequent adaptive immune responses. Here the authors show that mitochondrial membrane protein Fam73b regulates TLR-mediated mitochondrial switching of fusion to fission to induce IL-12 production via accumulation of Parkin and stabilization of IRF1 in macrophages, resulting in control of anti-tumor immunity in mice.

Sun and colleagues show that the deubiquitinase Trabid mediates the TLR-induced deubiqutination and stabilization of the histone demethylase Jmjd2d at the Il12 and Il23 promoters in dendritic cells. The proinflammatory cytokines interleukin 12 (IL-12) and IL-23 connect innate responses and adaptive immune responses and are also involved in autoimmune and inflammatory diseases. Here we describe an epigenetic mechanism for regulation of the genes encoding IL-12 ( Il12a and Il12b ; collectively called ' Il12 ' here) and IL-23 ( Il23a and Il12b ; collectively called ' Il23 ' here) involving the deubiquitinase Trabid. Deletion of Zranb1 (which encodes Trabid) in dendritic cells inhibited induction of the expression of Il12 and Il23 by Toll-like receptors (TLRs), which impaired the differentiation of inflammatory T cells and protected mice from autoimmune inflammation. Trabid facilitated TLR-induced histone modifications at the promoters of Il12 and Il23 , which involved deubiqutination and stabilization of the histone demethylase Jmjd2d. Our findings highlight an epigenetic mechanism for the regulation of Il12 and Il23 and establish Trabid as an innate immunological regulator of inflammatory T cell responses.

Chronic neuroinflammation is known to contributes to the toxicity of neurodegeneration of Parkinson’s disease (PD). However, the molecular and cellular mechanisms controlling inflammatory responses in the central nervous system remain poorly understood. Here we found that a E3 ubiquitin ligase Peli1 is dramatically induced only in the substantia nigra (SN) of the human and mouse PD brains. The ablation of Peli1 significantly suppressed LPS-induced production of neurotoxic mediators and proinflammatory cytokines in SN and in primary microglia, whereas Peli1 is dispensable for the inflammatory responses in astrocyte. Accordingly, Peli1 deficiency markedly inhibited neuron death induced by the conditioned medium from LPS-stimulated microglia. Mechanistical study suggested that Peli1 acts as a positive regulator of inflammatory response in microglia through activation of NF-κB and MAP kinase. Our results established Peli1 as a critical mediator in the regulation of microglial activation and neuroinflammation-induced death of dopaminergic neurons during PD pathogenesis, suggesting that targeting Peli1 may have therapeutic effect in neuroinflammation.

Ginkgo biloba extract is reported to have therapeutic effects on aging‐related disorders. However, the specific component responsible for this biological function and its mechanism of action remain largely unknown. This study finds that Ginkgetin, an active ingredient of Ginkgo biloba extract, can alleviate cellular senescence and improve pathologies in multiple tissues of aging mice. To reveal the molecular mechanism of Ginkgetin's anti‐aging effect, a graph convolutional network‐based drug “on‐target” pathway prediction algorithm for prediction is employed. The results indicate that the cGAS‐STING pathway may be a potential target for Ginkgetin. Subsequent cell biological and biophysical data confirmed that Ginkgetin directly binds to the carboxy‐terminal domain of STING protein, thereby inhibiting STING activation and signal transduction. Furthermore, in vivo pharmacodynamic data showed that Ginkgetin effectively alleviates systemic inflammation in Trex1−/− mice and inhibits the abnormally activated STING signaling in aging mouse model. In summary, this study, utilizing an artificial intelligence algorithm combined with pharmacological methods, confirms STING serves as a critical target for Ginkgetin in alleviating inflammation and senescence. Importantly, this study elucidates the specific component and molecular mechanism underlying the anti‐aging effect of Ginkgo biloba extract, providing a robust theoretical basis for its therapeutic use. An artificial intelligence algorithm is utilized to predict and confirm that STING serves as a critical target for Ginkgetin, an active ingredient of Ginkgo biloba extract, combined with pharmacological methods. In vivo experiments indicate that Ginkgetin effectively alleviates systemic inflammation in Trex1−/− mice and inhibits the aging phenotype and the abnormally activated STING signaling in aging mice.

Amyloid-β (Aβ) accumulation in the brain is a hallmark of Alzheimer's disease (AD) pathology. However, the molecular mechanism controlling microglial Aβ phagocytosis is poorly understood. Here we found that the E3 ubiquitin ligase Pellino 1 (Peli1) is induced in the microglia of AD-like five familial AD (5×FAD) mice, whose phagocytic efficiency for Aβ was then impaired, and therefore Peli1 depletion suppressed the Aβ deposition in the brains of 5×FAD mice. Mechanistic characterizations indicated that Peli1 directly targeted CCAAT/enhancer-binding protein (C/EBP)β, a major transcription factor responsible for the transcription of scavenger receptor CD36. Peli1 functioned as a direct E3 ubiquitin ligase of C/EBPβ and mediated its ubiquitination-induced degradation. Consequently, loss of Peli1 increased the protein levels of C/EBPβ and the expression of CD36 and thus, promoted the phagocytic ability in microglial cells. Together, our findings established Peli1 as a critical regulator of microglial phagocytosis and highlighted the therapeutic potential by targeting Peli1 for the treatment of microglia-mediated neurological diseases.

Systemic lupus erythematosus (SLE) is characterized by uncontrolled secretion of autoantibodies by plasma cells. Although the functional importance of plasma cells and autoantibodies in SLE has been well established, the underlying molecular mechanisms of controlling autoantibody production remain poorly understood. Here we show that Peli1 has a B cell-intrinsic function to protect against lupus-like autoimmunity in mice. Peli1 deficiency in B cells induces autoantibody production via noncanonical NF-κB signaling. Mechanically, Peli1 functions as an E3 ligase to associate with NF-κB inducing kinase (NIK) and mediates NIK Lys48 ubiquitination and degradation. Overexpression of Peli1 inhibits noncanonical NF-κB activation and alleviates lupus-like disease. In humans, PELI1 levels negatively correlate with disease severity in SLE patients. Our findings establish Peli1 as a negative regulator of the noncanonical NF-κB pathway in the context of restraining the pathogenesis of lupus-like disease. Systemic lupus erythematosus (SLE) is an autoimmune disorder mediated by excessive autoantibodies. Here the authors show that an E3 ubiquitin ligase, Peli1, negatively modulates noncanonical NF-κB signaling to restrain lupus-like symptoms in mice, and that Peli1 expression inversely correlates with SLE severity in humans.