Synergistic activation by p38MAPK and glucocorticoid signaling mediates induction of M2-like tumor-associated macrophages expressing the novel CD20 homolog MS4A8A

MS4A6D Promotes carrageenan-induced footpad swelling in mice through enhancing macrophages-derived inflammation

Our previous work has demonstrated that the tetraspan MS4A6D interacts with MHC-II to be a complex that promotes macrophage activation (Mol Immunol. 2023; 160: 121-132), however, the exact role of MS4A6D in controlling macrophage-derived inflammation is still poorly understood. Here, we showed that Ms4a6d-deficient (Ms4a6d-/-) mice manifested a lower level of footpad swelling induced by subcutaneous injection of 100 μL of 1% Carrageenan (CGN, w/v) plus CaCl2 (50 mM), a phenomenon that is similar to Nlrp3-/-, Casp-1-/-, and Ilr1-/- mice. Mechanistically, F4/80+ macrophages infiltrated in the footpad tissues of the Ms4A6d-/- mice was significantly lower than that of the WT littermates, leading to dramatically lower levels of proIL-1β in vivo. Moreover, macrophages from Ms4a6d-/- mice also showed a dramatical reduction of Il-1β secretion following NLRP3 inflammsome activation in vitro. Interestingly, both Ms4a6dC237G mutant (Interruption of MS4A6D homodimerization) and Ms4a6dY241G mutant (deletion of heITAM motif) mice also significantly inhibited CGN-induced footpad swelling due to lower levels of Il-1β secretion in vivo. Collectively, MS4A6D aggravates CGN-induced footpad swelling in mice by enhancing NLRP3 inflammasome in macrophages and inducing the release of IL-1β, indicating that MS4A6D promotes the progression of acute inflammation.

Tumor microenvironment restricts IL-10 induced multipotent progenitors to myeloid-lymphatic phenotype

Lymphangiogenesis is induced by local pro-lymphatic growth factors and bone marrow (BM)-derived myeloid-lymphatic endothelial cell progenitors (M-LECP). We previously showed that M-LECP play a significant role in lymphangiogenesis and lymph node metastasis in clinical breast cancer (BC) and experimental BC models. We also showed that differentiation of mouse and human M-LECP can be induced through sequential activation of colony stimulating factor-1 (CSF-1) and Toll-like receptor-4 (TLR4) pathways. This treatment activates the autocrine interleukin-10 (IL-10) pathway that, in turn, induces myeloid immunosuppressive M2 phenotype along with lymphatic-specific proteins. Because IL-10 is implicated in differentiation of numerous lineages, we sought to determine whether this pathway specifically promotes the lymphatic phenotype or multipotent progenitors that can give rise to M-LECP among other lineages. Analyses of BM cells activated either by CSF-1/TLR4 ligands in vitro or orthotopic breast tumors in vivo showed expansion of stem/progenitor population and coincident upregulation of markers for at least four lineages including M2-macrophage, lymphatic endothelial, erythroid, and T-cells. Induction of cell plasticity and multipotency was IL-10 dependent as indicated by significant reduction of stem cell markers and those for multiple lineages in differentiated cells treated with anti-IL-10 receptor (IL-10R) antibody or derived from IL-10R knockout mice. However, multipotent CD11b+/Lyve-1+/Ter-119+/CD3e+ progenitors detected in BM appeared to split into a predominant myeloid-lymphatic fraction and minor subsets expressing erythroid and T-cell markers upon establishing tumor residence. Each sub-population was detected at a distinct intratumoral site. This study provides direct evidence for differences in maturation status between the BM progenitors and those reaching tumor destination. The study results suggest preferential tumor bias towards expansion of myeloid-lymphatic cells while underscoring the role of IL-10 in early BM production of multipotent progenitors that give rise to both hematopoietic and endothelial lineages.

Molecular subtyping based on immune cell marker genes predicts prognosis and therapeutic response in patients with lung adenocarcinoma

OBJECTIVE

Lung adenocarcinoma (LA) is one of the most common malignancies and is responsible for the greatest number of tumor-related deaths. Our research aimed to explore the molecular subtype signatures of LA to clarify the correlation among the immune microenvironment, clinical outcomes, and therapeutic response.

METHODS

The LA immune cell marker genes (LICMGs) identified by single-cell RNA sequencing (scRNA-seq) analysis were used to discriminate the molecular subtypes and homologous immune and metabolic traits of GSE72094 LA cases. In addition, the model-building genes were identified from 1441 LICMGs by Cox-regression analysis, and a LA immune difference score (LIDscore) was developed to quantify individual differences in each patient, thereby predicting prognosis and susceptibility to immunotherapy and chemotherapy of LA patients.

RESULTS

Patients of the GSE72094 cohort were divided into two distinct molecular subtypes based on LICMGs: immune activating subtype (Cluster-C1) and metabolically activating subtype (cluster-C2). The two molecular subtypes have distinct characteristics regarding prognosis, clinicopathology, genomics, immune microenvironment, and response to immunotherapy. Among the LICMGs, LGR4, GOLM1, CYP24A1, SFTPB, COL1A1, HLA-DQA1, MS4A7, PPARG, and IL7R were enrolled to construct a LIDscore model. Low-LIDscore patients had a higher survival rate due to abundant immune cell infiltration, activated immunity, and lower genetic variation, but probably the higher levels of Treg cells in the immune microenvironment lead to immune cell dysfunction and promote tumor immune escape, thus decreasing the responsiveness to immunotherapy compared with that of the high-LIDscore patients. Overall, high-LIDscore patients had a higher responsiveness to immunotherapy and a higher sensitivity to chemotherapy than the low-LIDscore group.

CONCLUSIONS

Molecular subtypes based on LICMGs provided a promising strategy for predicting patient prognosis, biological characteristics, and immune microenvironment features. In addition, they helped identify the patients most likely to benefit from immunotherapy and chemotherapy.

Tetraspan MS4A6D is a coreceptor of MHC class II antigen (MHC-II) that promotes macrophages-derived inflammation

Our previous research demonstrated that the tetraspan MS4A6D is an adapter of VSIG4 that controls NLRP3 inflammasome activation (Sci Adv. 2019: eaau7426); however, the expression, distribution and biofunction of MS4A6D are still poorly understood. Here, we showed that MS4A6D is restricted to mononuclear phagocytes and that its gene transcript is controlled by the transcription factor NK2 homeobox-1 (NKX2-1). Ms4a6d-deficient (Ms4a6d-/-) mice showed normal macrophage development but manifested a greater survival advantage against endotoxin (lipopolysaccharide) challenge. Mechanistically, MS4A6D homodimers crosslinked with MHC class II antigen (MHC-II) to form a surface signaling complex under acute inflammatory conditions. MHC-II occupancy triggered Tyr241 phosphorylation in MS4A6D, leading to activation of SYK-CREB signaling cascades, further resulting in augmenting the transcription of proinflammatory genes (Il1b, Il6 and Tnfa) and amplifying the secretion of mitochondrial reactive oxygen species (mtROS). Deletion of Tyr241 or interruption of Cys237-mediated MS4A6D homodimerization in macrophages alleviated inflammation. Importantly, both Ms4a6dC237G and Ms4a6dY241G mutation mice phenocopied Ms4a6d-/- animals to prevent endotoxin lethality, highlighting MS4A6D as a novel target for treating macrophage-associated disorders.

Role of the membrane-spanning 4A gene family in lung adenocarcinoma

Lung adenocarcinoma, which is the second most prevalent cancer in the world, has a poor prognosis and a low 5-year survival rate. The MS4A protein family is crucial to disease development and progression, particularly for cancers, allergies, metabolic disorders, autoimmune diseases, infections, and neurodegenerative disorders. However, its involvement in lung adenocarcinoma remains unclear. In this study, we found that 11 MS4A family genes were upregulated or downregulated in lung adenocarcinoma. Furthermore, we described the genetic variation landscape of the MS4A family in lung adenocarcinoma. Notably, through functional enrichment analysis, we discovered that the MS4A family is involved in the immune response regulatory signaling pathway and the immune response regulatory cell surface receptor signaling pathway. According to the Kaplan-Meier curve, patients with lung adenocarcinoma having poor expression of MS4A2, MS4A7, MS4A14, and MS4A15 had a low overall survival rate. These four prognostic genes are substantially associated with immune-infiltrating cells, and a prognosis model incorporating them may more accurately predict the overall survival rate of patients with lung adenocarcinoma than current models. The findings of this study may offer creative suggestions and recommendations for the identification and management of lung adenocarcinoma.

The short isoform of MS4A7 is a novel player in glioblastoma microenvironment, M2 macrophage polarization, and tumor progression

BACKGROUND

The unique intracranial tumor microenvironment (TME) contributes to the immunotherapy failure for glioblastoma (GBM), thus new functional protein targets are urgently needed. Alternative splicing is a widespread regulatory mechanism by which individual gene can express variant proteins with distinct functions. Moreover, proteins located in the cell plasma membrane facilitate targeted therapies. This study sought to obtain functional membrane protein isoforms from GBM TME.

METHODS

With combined single-cell RNA-seq and bulk RNA-seq analyses, novel candidate membrane proteins generated by prognostic splicing events were screened within GBM TME. The short isoform of MS4A7 (MS4A7-s) was selected for evaluation by RT-PCR and western blotting in clinical specimens. Its clinical relevance was evaluated in a GBM patient cohort. The function of MS4A7-s was identified by in vitro and in vivo experiments. MS4A7-s overexpression introduced transcriptome changes were analyzed to explore the potential molecular mechanism.

RESULTS

The main expression product, isoform MS4A7-s, generated by exon skipping, is an M2-specific plasma membrane protein playing a pro-oncogenic role in GBM TME. Higher expression of MS4A7-s correlates with poor prognosis in a GBM cohort. In vitro cell co-culture experiments, intracranial co-injection tumorigenesis assay, and RNA-seq suggest MS4A7-s promotes activation of glioma-associated macrophages' (GAMs) PI3K/AKT/GSK3β pathway, leading to M2 polarization, and drives malignant progression of GBM.

CONCLUSIONS

MS4A7-s, a novel splicing isoform of MS4A7 located on the surface of GAMs in GBM TME, is a predictor of patient outcome, which contributes to M2 polarization and the malignant phenotype of GBM. Targeting MS4A7-s may constitute a promising treatment for GBM.

Th2 cytokines IL-4, IL-13, and IL-10 promote differentiation of pro-lymphatic progenitors derived from bone marrow myeloid precursors

Myeloid-lymphatic endothelial cell progenitors (M-LECP) are a subset of bone marrow (BM)-derived cells characterized by expression of M2-type macrophage markers. We previously showed significant contribution of M-LECP to tumor lymphatic formation and metastasis in human clinical breast tumors and corresponding mouse models. Since M2-type is induced in macrophages by immunosuppressive Th2 cytokines IL-4, IL-13, and IL-10, we hypothesized that these factors might promote pro-lymphatic specification of M-LECP during their differentiation from BM myeloid precursors. To test this hypothesis, we analyzed expression of Th2 cytokines and their receptors in mouse BM cells under conditions leading to M-LECP differentiation, namely, CSF-1 treatment followed by activation of TLR4. We found that under these conditions, all three Th2 receptors were strongly upregulated in >95% of the cells that also secrete endogenous IL-10 but not IL-4 or IL-13 ligands. However, addition of any of the Th2 factors to CSF-1 primed cells significantly increased generation of myeloid-lymphatic progenitors as indicated by co-induction of lymphatic-specific (e.g., Lyve-1, integrin-a9, collectin-12, and stabilin-1) and M2-type markers (e.g., CD163, CD204, CD206, and PD-L1). Antibody-mediated blockade of either IL-10 receptor (IL-10R) or IL-10 ligand significantly reduced both immunosuppressive and lymphatic phenotypes. Moreover, tumor-recruited Lyve-1+ lymphatic progenitors in vivo expressed all Th2 receptors as well as corresponding ligands including IL-4 and IL-13 that were absent in BM cells. This study presents original evidence for the significant role of Th2 cytokines in co-development of immunosuppressive and lymphatic phenotypes in tumor-recruited M2-type myeloid cells. Progenitor-mediated increase in lymphatic vessels can enhance immunosuppression by physical removal of stimulatory immune cells. Thus, targeting Th2 pathways might simultaneously relieve immunosuppression and inhibit differentiation of pro-lymphatic progenitors that ultimately promote tumor spread.

Tumor microenvironment remodeling modulates macrophage phenotype in breast cancer lymphangiogenesis

Hyaluronan (HA) is dynamically remodeled in tumor microenvironment (TME) and is reported to be closely related to tumor lymphatic metastasis by inducing lymphangiogenesis. Macrophages are known to be involved in neo-lymphatic vessels formation. However, few studies have investigated the role of HA-mediated TME remodeling on macrophages-dependent lymphangiogenesis. We previously showed that HA could drive macrophages to acquire the M2 phenotype. In this study, we attempt to study the crosstalk between HA in TME and macrophages dependent lymphangiogenesis. First, we found that the abundant assembly of HA in breast cancer tissue was accompanied by increased infiltration of macrophages featured by expressing lymphatic endothelial markers. Then, to further identify the remodeling of HA in regulating macrophage phenotype, we used HA fragments which are usually enriched in TME for this purpose. Our results showed that the reconstructed HA could induce bone marrow-derived macrophages (BMDMs) to express markers of lymphatic endothelium and form tube-like structures, suggesting a novel function of HA from TME on macrophages-dependent lymphangiogenesis. Finally, we found that inhibition of the HA-TLR4 pathway could reduce the ability of BMDMs to exhibit lymphatic endothelial phenotype. Our results provide new insight into tumor microenvironment remodeling and macrophages in breast cancer lymphangiogenesis.

Tumor-Associated Macrophage-Derived Exosomes Promote the Progression of Gastric Cancer by Regulating the P38MAPK Signaling Pathway and the Immune Checkpoint PD-L1

Objective: To investigate the effects of M2 macrophage-derived exosomes (M2-Exos) on proliferation, migration, and apoptosis of gastric cancer cells in the tumor microenvironment and to further explore their possible molecular mechanism. Materials and Methods: M2 macrophages were induced from THP-1 cells and identified by qRT-PCR. Exosomes were extracted by ultracentrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot analysis. Fluorescence labeling was used to detect the internalization of exosomes in receptors. The proliferation, migration, and invasion of AGS and HGC27 cells were determined by EdU and MTS, wound healing and Transwell assay, and flow cytometry, respectively. Proteins in the related pathway of M2-Exos affecting the progression of gastric cancer were detected by Western blot analysis. Results: In this study, M2 macrophages and M2-Exos were successfully obtained. The purified M2-Exos were observed as small round vesicles with diameters of 50-90 nm and positive expression of CD63, CD9, and TSG101. Besides, M2-Exos can be effectively taken up and internalized by AGS and HGC27 cells. Cell behavior studies showed that M2-Exos promoted proliferation and migration and inhibited the apoptosis of AGS and HGC27. Further research illustrated that M2-Exos promoted the phosphorylation of P38 and high expression of programmed death ligand 1 (PD-L1). Conclusions: This study demonstrated that M2-Exos promoted proliferation and migration and inhibited the apoptosis of gastric cancer cells. Mechanically, M2-Exos may promote gastric cancer progression through the P38MAPK signaling pathway and achieve immune escape through elevating the expression of PD-L1.

Elevated SYNC Expression Is Associated with Gastric Tumorigenesis and Infiltration of M2-Polarized Macrophages in the Gastric Tumor Immune Microenvironment

Aims: To assess the expression and epigenetic regulation of Syncoilin, intermediate filament protein (SYNC) in gastric cancer tissues, and to determine its associations with clinicopathological features; immune infiltration of macrophages in tumors; and patient survival. Materials and Methods: Clinicopathological features, expression profiles, and methylation data of the SYNC gene were obtained from multi-institutional real-world public datasets. A total of 1601 samples from patients with gastric cancer were examined. The associations between clinicopathological features and SYNC expression levels were assessed by the chi-square test; survival was assessed using the Kaplan-Meier analysis. The infiltration levels of M1, 2-polarized tumor-associated macrophages (TAMs) in a gastric tumor immune microenvironment were quantified using deconvolution, and the correlation between SYNC expression level and M1, 2-polarized macrophages' infiltration was examined using the Pearson correlation test. SYNC gene methylation data were analyzed to investigate epigenetic control of its expression. Results: SYNC expression was elevated in gastric cancer tissues (p < 0.01), and was associated with a poorer overall survival (p < 0.01) and poorer postprogression survival (p = 0.01). Higher SYNC levels were significantly associated with more aggressive clinicopathological features in gastric cancer patients (p < 0.05). SYNC was also associated with the infiltration of M2-polarized TAMs in the gastric tumor immune microenvironment (p < 0.001). Hypomethylation was shown to be associated with SYNC's upregulation (p < 0.05). Conclusion: SYNC is highly expressed in gastric cancer tissues and has the potential to be a therapeutic target and to serve as a prognostic marker.

The tetraspan MS4A family in homeostasis, immunity, and disease

The membrane-spanning 4A (MS4A) family includes 18 members with a tetraspan structure in humans. They are differentially and selectively expressed in immunocompetent cells, such as B cells (CD20/MS4A1) and macrophages (MS4A4A), and associate with, and modulate the signaling activity of, different classes of immunoreceptor, including pattern recognition receptors (PRRs) and Ig receptors. Evidence from preclinical models and genetic evidence from humans suggest that members of the MS4A family have key roles in different pathological settings, including cancer, infectious diseases, and neurodegeneration. Therefore, MS4A family members might serve as candidate biomarkers and therapeutic targets for various conditions.

Fibronectin in Cancer: Friend or Foe

The role of fibronectin (FN) in tumorigenesis and malignant progression has been highly controversial. Cancerous FN plays a tumor-suppressive role, whereas it is pro-metastatic and associated with poor prognosis. Interestingly, FN matrix deposited in the tumor microenvironments (TMEs) promotes tumor progression but is paradoxically related to a better prognosis. Here, we justify how FN impacts tumor transformation and subsequently metastatic progression. Next, we try to reconcile and rationalize the seemingly conflicting roles of FN in cancer and TMEs. Finally, we propose future perspectives for potential FN-based therapeutic strategies.

Bioprofiling TS/A Murine Mammary Cancer for a Functional Precision Experimental Model

The TS/A cell line was established in 1983 from a spontaneous mammary tumor arisen in an inbred BALB/c female mouse. Its features (heterogeneity, low immunogenicity and metastatic ability) rendered the TS/A cell line suitable as a preclinical model for studies on tumor-host interactions and for gene therapy approaches. The integrated biological profile of TS/A resulting from the review of the literature could be a path towards the description of a precision experimental model of mammary cancer.

Stress hormone-mediated acceleration of breast cancer metastasis is halted by inhibition of nitric oxide synthase

Stress hormones have been shown to be important mediators in driving malignant growth and reducing treatment efficacy in breast cancer. Glucocorticoids can induce DNA damage through an inducible nitric oxide synthase (iNOS) mediated pathway to increase levels of nitric oxide (NO). Using an immune competent mouse breast cancer model and 66CL4 breast cancer cells we identified a novel role of NOS inhibition to reduce stress-induced breast cancer metastasis. On a mechanistic level we show that the glucocorticoid cortisol induces expression of keys genes associated with angiogenesis, as well as pro-tumourigenic immunomodulation. Transcriptomics analysis confirmed that in the lungs of tumour-bearing mice, stress significantly enriched pathways associated with tumourigenesis, some of which could be regulated with NOS inhibition. These results demonstrate the detrimental involvement of NOS in stress hormone signalling, and the potential future benefits of NOS inhibition in highly stressed patients.

Exploiting vulnerabilities of cancer by targeting nuclear receptors of stromal cells in tumor microenvironment

The tumor microenvironment is a complex and dynamic cellular community comprising the tumor epithelium and various tumor-supporting cells such as immune cells, fibroblasts, immunosuppressive cells, adipose cells, endothelial cells, and pericytes. The interplay between the tumor microenvironment and tumor cells represents a key contributor to immune evasiveness, physiological hardiness and the local and systemic invasiveness of malignant cells. Nuclear receptors are master regulators of physiological processes and are known to play pro-/anti-oncogenic activities in tumor cells. However, the actions of nuclear receptors in tumor-supporting cells have not been widely studied. Given the excellent druggability and extensive regulatory effects of nuclear receptors, understanding their biological functionality in the tumor microenvironment is of utmost importance. Therefore, the present review aims to summarize recent evidence about the roles of nuclear receptors in tumor-supporting cells and their implications for malignant processes such as tumor proliferation, evasion of immune surveillance, angiogenesis, chemotherapeutic resistance, and metastasis. Based on findings derived mostly from cell culture studies and a few in vivo animal cancer models, the functions of VDR, PPARs, AR, ER and GR in tumor-supporting cells are relatively well-characterized. Evidence for other receptors, such as RARβ, RORγ, and FXR, is limited yet promising. Hence, the nuclear receptor signature in the tumor microenvironment may harbor prognostic value. The clinical prospects of a tumor microenvironment-oriented cancer therapy exploiting the nuclear receptors in different tumor-supporting cells are also encouraging. The major challenge, however, lies in the ability to develop a highly specific drug delivery system to facilitate precision medicine in cancer therapy.

Relationship among MS4A8 expression, its variants, and the immune response in a porcine model of Salmonella

Salmonella colonization often establishes carrier status in infected animals, which decreases their performance. Salmonella-carrying pigs shed large amounts of bacteria in their feces, and thus they have a negative economic impact on the swine industry. The MS4A8 gene (membrane-spanning 4-domains A8) was significantly activated, by up to 119-fold, in peripheral blood after Salmonella inoculation of pigs. The present study analyzed the correlation of peripheral blood expression level and a genetic variant of porcine MS4A8 with Salmonella-infection traits. The result indicated that MS4A8 expression levels correlated significantly with Salmonella shedding counts. Both the expression of MS4A8 and fecal shedding counts correlated with leukocytes, lymphocytes, monocytes, segmented neutrophils, and banded neutrophils. A novel single nucleotide polymorphism of porcine MS4A8 (nonsynonymous, Val > Ala) was associated with Salmonella shedding counts and average daily gain (ADG) of body weight. The TT genotype had higher fecal shedding counts, leukocyte counts, and lymphocyte counts than the TC and CC genotypes. The CC genotype had higher level of ADG than the TC and TT genotype (p < 0.05). Those results indicated that MS4A8 is intriguing and could be used as a prospective genetic marker for Salmonella susceptibility.

The novel immunoglobulin super family receptor SLAMF9 identified in TAM of murine and human melanoma influences pro-inflammatory cytokine secretion and migration

Melanoma is a highly immunogenic tumor with a good response to treatment with immune checkpoint inhibitors. Tumor-associated macrophages (TAMs) play an important immunosuppressive role in such tumors and have therefore been identified as possible future therapeutic targets in oncology. The aim of this study was to identify novel immunoregulatory receptors specifically expressed on TAM. Expression of Slamf9, a member of the signaling lymphocytic-activating molecule (Slam) immunoreceptor family, was found to be upregulated in a gene expression analysis of murine bone marrow-derived macrophages (BMDM) stimulated with tumor-conditioned medium of B16F1 melanoma cells. SLAMF9⁺ macrophages were identified in human and murine melanomas by using self-generated antibodies against human and murine SLAMF9. A comprehensive immunohistochemical analysis of tissue microarrays detected SLAMF9⁺ TAM in 73.3% of human melanomas, but also in 95.5% of naevi of melanoma patients and in 50% of naevi from healthy controls. In addition, 20% of melanomas and 2.3% of naevi from melanoma patients displayed a positive SLAMF9 expression also in melanocytic cells. No SLAMF9 expression was detected in naevus cells of healthy donors. Although SLAMF9 has no intracellular signaling motif, a comprehensive functional analysis revealed that the molecule was able to significantly enhance TNF-α secretion after LPS-stimulation. In addition, SLAMF9 delayed the wound closure of RAW 264.7 cells in a scratch assay, while proliferation and cell death were not affected. Taken together, SLAMF9 is a novel type-I-transmembrane receptor with immunomodulatory properties in macrophages. Further studies are required to evaluate whether SLAMF9 classifies as a promising future therapeutic target in melanoma.

Crosstalk between glucocorticoids and IL-4 modulates Ym1 expression in alternatively activated myeloid cells

Airway epithelial cells induce a tolerogenic microenvironment by modulating immune cells in the lung. We recently showed that the supernatant of airway epithelial cells induces two marker genes of alternative activation, Ym1 and Ms4a8a, in respiratory myeloid cells. This induction was partially mediated by glucocorticoids, secreted by airway epithelial cells. In this study, we further investigated Ym1 and Ms4a8a regulation in alternatively activated myeloid cells in the presence of the T_H2 cytokines IL-4 and IL-13. We show that Ym1 expression is boosted upon co-stimulation with airway epithelial cell supernatant and IL-4/IL-13, whereas Ms4a8a expression is down-regulated. This suggests that a crosstalk between IL-4/IL-13 and glucocorticoid signaling exists. Blocking protein synthesis indicated that dexamethasone-induced de novo protein synthesis is required for the interaction between glucocorticoid and IL-4 signaling regarding Ym1 regulation. Using reporter gene constructs, we demonstrate that the important regulatory region within the Ym1 promoter is found between -602bp and -969bp upstream of the start of translation. Bioinformatic analysis identified several glucocorticoid response elements (GREs) in this region. Further analysis identified overlapping but functionally active glucocorticoid receptor and STAT-6 binding sites, supporting the cooperative effect of glucocorticoids and IL-4 in the regulation of Ym1. These findings further prove the plasticity and complexity of alternatively activated myeloid cells and the importance of the local microenvironment. We believe that this regulation is of special importance in the pulmonary system, since both factors, glucocorticoids and IL-4/13, play a role in airway diseases such as asthma.

Increase of Alternatively Activated Antigen Presenting Cells in Active Experimental Autoimmune Encephalomyelitis

The importance of CD11c⁺ antigen-presenting cells (APCs) in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) is well accepted and the gate keeper function of perivascular CD11c⁺ APCs has been demonstrated. CD11c can be expressed by APCs from external sources or by central nervous system (CNS) resident APCs such as microglia. Yet, changes in the gene expression pattern of CNS CD11c⁺ APCs during disease are still unclear and differentially expressed genes might play a decisive role in EAE progression. Due to their low numbers in the diseased brain and due to the absence of considerable numbers in the healthy CNS, analysis of CNS CD11c⁺ cells is technically difficult. To ask whether the CD11c⁺ APC population contributes to remission of EAE disease, we used Illumina deep mRNA sequencing (RNA-Seq) and quantitative real time polymerase chain reaction (qRT-PCR) analyses to identify the transcriptome of CD11c⁺ APCs during disease course. We identified a battery of genes that were significantly regulated during the exacerbation of the disease compared to remission and relapse. Three of these genes, Arginase-1, Chi3l3 and Ms4a8a, showed a higher expression at the exacerbation than at later time points during the disease, both in SJL/J and in C57BL/6 mice, and could be attributed to alternatively activated APCs. Expression of Arginase-1, Chi3l3 and Ms4a8a genes was linked to the disease phase of EAE rather than to disease score. Expression of these genes suggested that APCs resembling alternatively activated macrophages are involved during the first wave of neuroinflammation and can be directly associated with the disease progress.

The MS4A family: counting past 1, 2 and 3

The MS4A (membrane-spanning 4-domain family, subfamily A) family of proteins contains some well-known members including MS4A1 (CD20), MS4A2 (FcɛRIβ) and MS4A3 (HTm4). These three MS4A family members are expressed on the cell surface of specific leukocyte subsets and have been well characterized as having key roles in regulating cell activation, growth and development. However, beyond MS4A1-3 there are a large number of related molecules (18 to date in humans) where our understanding of their biological roles is at a relatively nascent stage. This review examines the larger MS4A family focusing on their structure, expression, regulation and characterized and/or emerging biological roles. Our own work on one family member MS4A8B, and its possible role in epithelial cell regulation, is also highlighted.

Bronchial epithelial cells induce alternatively activated dendritic cells dependent on glucocorticoid receptor signaling

Airway epithelial cells mount a tolerogenic microenvironment that reduces the proinflammatory potential of respiratory dendritic cells (DCs). We recently demonstrated that tracheal epithelial cells continuously secrete soluble mediators that affect the reactivity of local innate immune cells. Using transcriptional profiling, we now observed that conditioning of DCs by tracheal epithelial cells regulated 98 genes under homeostatic conditions. Among the most upregulated genes were Ms4a8a and Ym1, marker genes of alternatively activated myeloid cells. Ex vivo analysis of respiratory DCs from nonchallenged mice confirmed a phenotype of alternative activation. Bioinformatic analysis showed an overrepresentation of hormone-nuclear receptors within the regulated genes, among which was the glucocorticoid receptor. In line with a role for glucocorticoids, pharmacological blockade as well as genetic manipulation of the glucocorticoid receptor within DCs inhibited Ms4a8a and Ym1 expression as well as MHC class II and CD86 regulation upon epithelial cell conditioning. Within epithelial cell-conditioned medium, low amounts of glucocorticoids were present. Further analysis showed that airway epithelial cells did not produce glucocorticoids de novo, yet were able to reactivate inactive dehydrocorticosterone enzymatically. The results show that airway epithelial cells regulate local immune responses, and this modulation involves local production of glucocorticoids and induction of an alternative activation phenotype in DCs.

MS4A8B promotes cell proliferation in prostate cancer

BACKGROUND

Prostate cancer cells must maintain or achieve the further ability of proliferation during the progression. The molecular mechanisms, however, remain poorly understood. We identified a novel oncogene, termed membrane-spanning 4-domains, subfamily A, member 8B (MS4A8B), over-expressed in prostate cancer.

METHODS

We firstly detected MS4A8B mRNA in 13 types of paired human normal and cancer tissues by real-time polymerase chain reaction (RT-PCR). In 140 clinically localized prostate cancer samples from radical prostatectomy, immunohistochemical staining was performed to study MS4A8B and PCNA protein level as an index of proliferative activity, TUNEL staining as an index of apoptosis. As MS4A8B RNAi and cDNA transfection technologies were used, the effect of MS4A8B on cellular vitality was determined in vitro and in vivo.

RESULTS

MS4A8B mRNA was over-expressed specifically in prostate cancer. Positive ratios of MS4A8B protein expression were 1.94%, 5.92%, and 62.8% in benign, HPIN and prostate cancer, respectively. Moreover, MS4A8B was positively associated with Gleason score, the proliferation index. In vitro, MS4A8B knockdown resulted in G1 -S cell cycle arrest and descended vitality, MS4A8B over-expression with accelerated S phase entry, elevated vitality in prostate cancer cells. Moreover, it was also found that expression of MS4A8B led to changes of Cyclin D1 , Cyclin E1 and PCNA. LNCaP cells transfected with sh-MS4A8B lentivirus particles grew more slowly when subcutaneously injected into the flanks of nude mice.

CONCLUSIONS

We conclude that the expression of MS4A8B expression promotes cell proliferation and plays an important role in carcinogenesis and progression of prostate cancer.

Identification of the novel differentiation marker MS4A8B and its murine homolog MS4A8A in colonic epithelial cells lost during neoplastic transformation in human colon

The CD20-homolog Ms4a8a has recently been shown to be a marker for alternatively activated macrophages but its expression is not restricted to hematopoietic cells. Here, MS4A8A/MS4A8B expression was detected in differentiated intestinal epithelium in mouse and human, respectively. Interestingly, no MS4A8B expression was found in human colon carcinoma. Forced overexpression of MS4A8A in the murine colon carcinoma cell line CT26 led to a reduced proliferation and migration rate. In addition, MS4A8A-expressing CT26 cells displayed an increased resistance to hydrogen peroxide-induced apoptosis, which translated in an increased end weight of subcutaneous MS4A8A+ CT26 tumors. Gene profiling of MS4A8A+ CT26 cells revealed a significant regulation of 225 genes, most of them involved in cytoskeletal organization, apoptosis, proliferation, transcriptional regulation and metabolic processes. Thereby, the highest upregulated gene was the intestinal differentiation marker cytokeratin 20. In conclusion, we show that MS4A8A/MS4A8B is a novel differentiation marker of the intestinal epithelium that supports the maintenance of a physiological barrier function in the gut by modulating the transcriptome and by conferring an increased resistance to reactive oxygen species. The absence of MS4A8B in human colonic adenocarcinomas shown in this study might be a helpful tool to differentiate between healthy and neoplastic tissue.

The CD20 homolog Ms4a8a integrates pro- and anti-inflammatory signals in novel M2-like macrophages and is expressed in parasite infection

Recently, we identified the CD20 homolog Ms4a8a as a novel molecule expressed by tumor-associated macrophages that directly enhances tumor growth. Here, we analyzed Ms4a8a(+) macrophages in M2-associated infectious pathologies. In late-stage Trypanosoma congolense and Taenia crassiceps infections, Ms4a8a expression was detected in hepatic and peritoneal macrophages respectively. Innate immunity in these infections is modulated by Toll-like receptor (TLR) signaling and TLR2/4/7 agonists strongly induced Ms4a8a expression in bone marrow derived macrophages (BMDMs) treated with M2 mediators (glucocorticoids/IL-4). LPS/dexamethasone/IL-4-induced Ms4a8a(+) BMDMs were characterized by strong expression of mRNA of mannose receptor (Mmr), arginase 1, and CD163, and by decreased iNOS expression. Coinduction of Ms4a8a by M2 mediators and TLR agonists involved the classical TLR signaling cascade via activation of MyD88/TRIF and NF-κB. Forced overexpression of Ms4a8a modulated the TLR4 response of RAW264.7 cells as shown by gene expression profiling. Upregulation of Hdc, Tcfec, and Sla was confirmed both in primary LPS/dexamethasone/IL-4-stimulated Ms4a8a(+) BMDMs and in peritoneal macrophages from late-stage Taenia crassiceps infection. In conclusion, we show that TLR signaling skews the typical alternative macrophage activation program to induce a special M2-like macrophage subset in vitro that also occurs in immunomodulatory immune reactions in vivo, a process directly involving the CD20 homolog Ms4a8a.

Differentiation and gene expression profile of tumor-associated macrophages

Tumor microenvironment is composed of proliferating neoplastic cells, a vascular network of endothelial cells, extra cellular matrix produced by fibroblasts, cellular compartments of adaptive immunity like lymphocytes and dendritic cells as well as cells of innate immunity, e.g., natural killer cells and macrophages. Many pre-clinical and clinical studies demonstrate an inversed correlation between macrophage infiltrate and patients' prognosis indicating a macrophage supporting role for tumor progression as producers of growth and angiogenic factors and as regulators of tissue remodelling. Based on in vitro models, macrophages have been classified in pro-inflammatory, classically activated macrophages (M1; stimulated by IFN-γ or LPS) and anti-inflammatory, alternatively activated macrophages (M2; stimulated by either IL-4/IL-13, IL-1β/LPS in combination with immune complexes or by IL-10/TGFβ/glucocorticoids). Tumor escape has been linked with a switch from M1 activation in the early tumor initiation process towards M2-like phenotype during tumor progression, a process that highlights the heterogeneity and plasticity of macrophage activation and which offers a possible therapeutic target directed against reversing the TAM phenotype in the tumor. Here, we review different tumor-environmental stimuli and signalling cascades involved in this switch in differentiation and the so connected gene regulation in TAMs. In addition, therapeutic applications deducted from this differentiation and gene regulatory processes are presented. Data from pre-clinical as well as clinical studies clearly support the notion, that TAMs are excellent novel therapeutic targets for the fight against cancer.

Tumor cells and tumor-associated macrophages: secreted proteins as potential targets for therapy

Inflammatory pathways, meant to defend the organism against infection and injury, as a byproduct, can promote an environment which favors tumor growth and metastasis. Tumor-associated macrophages (TAMs), which constitute a significant part of the tumor-infiltrating immune cells, have been linked to the growth, angiogenesis, and metastasis of a variety of cancers, most likely through polarization of TAMs to the M2 (alternative) phenotype. The interaction between tumor cells and macrophages provides opportunities for therapy. This paper will discuss secreted proteins as targets for intervention.