Cholinergic macrophages promote the resolution of peritoneal inflammation.

The non-neural cholinergic system plays a critical role in regulating immune equilibrium and tissue homeostasis. While the expression of choline acetyltransferase (ChAT), the enzyme catalyzing acetylcholine biosynthesis, has been well documented in lymphocytes, its role in the myeloid compartment is less understood. Here, we identify a significant population of macrophages (Mϕs) expressing ChAT and synthesizing acetylcholine in the resolution phase of acute peritonitis. Using Chat-GFP reporter mice, we observed marked upregulation of ChAT in monocyte-derived small peritoneal Mϕs (SmPMs) in response to Toll-like receptor agonists and bacterial infections. These SmPMs, phenotypically and transcriptionally distinct from tissue-resident large peritoneal macrophages, up-regulated ChAT expression through a MyD88-dependent pathway involving MAPK signaling. Notably, this process was attenuated by the TRIF-dependent TLR signaling pathway, and our tests with a range of neurotransmitters and cytokines failed to induce a similar response. Functionally, Chat deficiency in Mϕs led to significantly decreased peritoneal acetylcholine levels, reduced efferocytosis of apoptotic neutrophils, and a delayed resolution of peritonitis, which were reversible with exogenous ACh supplementation. Intriguingly, despite B lymphocytes being a notable ChAT-expressing population within the peritoneal cavity, Chat deletion in B cells did not significantly alter the resolution process. Collectively, these findings underscore the crucial role of Mϕ-derived acetylcholine in the resolution of inflammation and highlight the importance of the non-neuronal cholinergic system in immune regulation.

PERK reprograms hematopoietic progenitor cells to direct tumor-promoting myelopoiesis in the spleen.

The spleen is an important site of hematopoietic stem/progenitor cell (HSPC) preconditioning and tumor-promoting myeloid cell generation in cancer, but the regulatory mechanism remains unclear. Here, we found that PKR-like endoplasmic reticulum kinase (PERK) mediated HSPC reprogramming into committed MDSC precursors in the spleen via PERK-ATF4-C/EBPß signaling. Pharmacological and genetic inhibition of this pathway in murine and human HSPCs prevented their myeloid descendant cells from becoming MDSCs even with subsequent exposure to tumor microenvironment (TME) factors. In mice, the selective delivery of PERK antagonists to the spleen was not only sufficient but more effective than the tumor-targeted strategy in preventing MDSC activation in the tumor, leading to profound TME reshaping and tumor regression. Clinically, HSPCs in the spleen of cancer patients exhibit increased PERK signaling correlated with enhanced myelopoiesis. Our findings indicate that PERK-mediated HSPC preconditioning plays a crucial role in MDSC generation, suggesting novel spleen-targeting therapeutic opportunities for restraining the tumor-promoting myeloid response at its source.

Type I IFNs repolarized a CD169+ macrophage population with anti-tumor potentials in hepatocellular carcinoma.

Macrophages constitute a major component in human hepatocellular carcinoma (HCC) and perform various functions to facilitate disease progression. Reprogramming or reconstituting the tumor surveillance phenotypes of macrophages represents an attractive immunotherapeutic strategy in cancer treatments. The current study identified CD169 as a potential target for macrophage repolarization since it signified a population of macrophages positively correlated with an activated immune signature and better prognosis of patients with HCC. In vitro experiments revealed that a low dose of type I interferon (IFN) could effectively reprogram human monocyte-derived macrophages to upregulate CD169 expression, and such induced CD169+ macrophages exhibited significantly enhanced phagocytotic and CD8+ T cell-activating capacities compared to controls. A low dose of IFNα also inhibited hepatoma growth in mice in vivo, presumably through polarizing the CD169+ macrophage population and enhancing CD8+ T cell activities. Notably, IFNα also induced substantial PD-L1 expression on macrophages in vivo, and thus blockade of PD-L1 could further increase the anti-tumor efficacy of IFNα in the treatment of HCC. We propose a low dose of IFNα in combination with a PD-L1 blocking agent as a potential anti-tumor therapeutic strategy via its effects on macrophage polarization.

Generation of Myeloid Cells in Cancer: The Spleen Matters.

Myeloid cells are key components of the tumor microenvironment and critical regulators of disease progression. These innate immune cells are usually short-lived and require constant replenishment. Emerging evidence indicates that tumors alter the host hematopoietic system and induce the biased differentiation of myeloid cells to tip the balance of the systemic immune activities toward tumor-promoting functions. Altered myelopoiesis is not restricted to the bone marrow and also occurs in extramedullary organs. In this review, we outline the recent advances in the field of cancer-associated myelopoiesis, with a focus on the spleen, the major site of extramedullary hematopoiesis in the cancer setting. We discuss the functional specialization, distinct mechanisms, and clinical relevance of cancer-associated myeloid cell generation from early progenitors in the spleen and its potential as a novel therapeutic target.

Myeloid signature reveals immune contexture and predicts the prognosis of hepatocellular carcinoma.

BACKGROUNDDespite an increasing appreciation of the roles that myeloid cells play in tumor progression and therapy, challenges remain in interpreting the tumor-associated myeloid response balance and its translational value. We aimed to construct a simple and reliable myeloid signature for hepatocellular carcinoma (HCC).METHODSUsing in situ immunohistochemistry, we assessed the distribution of major myeloid subtypes in both peri- and intratumoral regions of HCC. A 2-feature-based, myeloid-specific prognostic signature, named the myeloid response score (MRS), was constructed using an L1-penalized Cox regression model based on data from a training subset (n = 244), a test subset (n = 244), and an independent internal (n = 341) and 2 external (n = 94; n = 254) cohorts.RESULTSThe MRS and the MRS-based nomograms displayed remarkable discriminatory power, accuracy, and clinical usefulness for predicting recurrence and patient survival, superior to current staging algorithms. Moreover, an increase in MRS was associated with a shift in the myeloid response balance from antitumor to protumor activities, accompanied by enhanced CD8+ T cell exhaustion patterns. Additionally, we provide evidence that the MRS was associated with the efficacy of sorafenib treatment for recurrent HCC.CONCLUSIONWe identified and validated a simple myeloid signature for HCC that showed remarkable prognostic potential and may serve as a basis for the stratification of HCC immune subtypes.FUNDINGThis work was supported by the National Science and Technology Major Project of China, the National Natural Science Foundation of China, the Science and Information Technology of Guangzhou, the Fundamental Research Funds for the Central Universities, the Guangdong Basic and Applied Basic Research Foundation, and the China Postdoctoral Science Foundation.

Targeting adenosinergic pathway enhances the anti-tumor efficacy of sorafenib in hepatocellular carcinoma.

BACKGROUND: Sorafenib is the most widely used first-line treatment for patients with advanced hepatocellular carcinoma (HCC), but such treatment provides only limited survival benefits that might be related to the immune status of distinct tumor microenvironments. A fundamental understanding of the distribution and phenotypes of T lymphocytes in tumors will undoubtedly lead to the development of novel immunotherapeutic strategies that could possibly enhance the efficacy of sorafenib treatments. METHODS: Flow cytometry, immunohistochemistry and immunofluorescence analyses were performed to detect the infiltration and distribution of various leukocyte populations, and the expression of different immune checkpoint molecules in fresh HCC tumor tissues. Correlations among indicating genes were calculated in 365 patients with HCC from The Cancer Genome Atlas (TCGA) data set, and the cumulative overall survival time was calculated using the Kaplan-Meier method. Moreover, role of adenosinergic pathway on sorafenib anti-tumor efficacy was investigated using both subcutaneous and orthotopic transplantation tumor model in immune competent C57BL/6 mice. RESULTS: We revealed that levels of CD3+ and CD8+ T cells were significantly downregulated in HCC tumor tissue, so were the infiltration of CD169+ cells (a Mφ subpopulation with T cell activation capacities) and their contact with CD8+ cells in tumor milieus. Moreover, levels of PD-1 and CD39 expression were significantly upregulated in human HCC-infiltrating CD4+ and CD8+ T cells, and CD39+CD8+ T cells exhibited a CD69+PD-1+perforinlowIFNγlow "exhausted" phenotype. Levels of both CD39+ T cells infiltration and adenosine receptor ADORA2B expression in tumor tissues were negatively correlated with overall survival of patients with HCC. Accordingly, mice treated with sorafenib in combination with adenosine A2B receptor blockage reagents exhibited significantly reduced tumor progression compared with control groups. CONCLUSIONS: These results suggest that adenosinergic pathway might represent an applicable target for sorafenib-combined-therapies in human HCC.