Comparison of physicochemical parameters, microbial community composition and flavor substances during mechanical and traditional brewing process of Jiang-flavor baijiu.

Mechanized, automated and intelligent brewing is an important trend of innovation and transition in Jiang-flavor baijiu industry. In this study, physicochemical parameters, microbial community composition and flavor substances during 3rd round heap fermentation between mechanical and traditional workshop were investigated and compared based on traditional culturable methods, high-throughput sequencing technology and gas chromatography analysis. The dominant bacterial and fungal genera were consistent between the two workshops, but mechanized brewing had a significant impact on the composition of fungal communities. Rhodococcus and Monascus were special genera in mechanical workshop. The interaction relationship between physicochemical parameters and dominant microorganisms in mechanized workshop was different from traditional workshop as well. This study provided a scientific basis for further analyzing the mechanism of mechanized brewing of Jiang-flavor baijiu. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-023-01483-y.

Comprehensive genomic and metabolomic analysis revealed the physiological characteristics and pickle like odor compounds metabolic pathways of Bacillus amyloliquefaciens ZZ7 isolated from fermented grains of Maotai-flavor baijiu.

Pickle like odor (PLO) is one of the main defective flavors of Maotai flavor baijiu (MFB). Understanding and controlling the PLO compounds producing strains not only solves the problem of PLO from the source, but also ensures the high-quality production of MFB. However, the relevant research on PLO compounds producing strains has not been reported in MFB. In this study, we identified a Bacillus amyloliquefaciens ZZ7 with high yield of PLO compounds in the fermented grains of MFB, and measured its physiological characteristics. It produces 627 volatile compounds and 1,507 non-volatile compounds. There are 7 volatile sulfur compounds that cause the PLO, the content of dimethyl disulfide, dimethyl trisulfide, and dimethyl sulfur is relatively high, accounting for 89.43% of the total volatile sulfur compounds. The genome size of B. amyloliquefaciens ZZ7 is 3,902,720 bp with a GC content of 46.09%, and a total of 3,948 protein coding genes were predicted. Moreover, the functional annotation of coding genes and an assessment of the metabolic pathways were performed by genome annotation, showing it has strong ability to transport and metabolize amino acids and carbohydrates. Comprehensive genomic and metabolomic analysis, the metabolic pathway of PLO compounds of B. amyloliquefaciens ZZ7 was revealed, which mainly involves 12 enzymes including sulfate adenylyltransferase, cysteine synthase, cystathionine γ-synthase, etc. This work provides biological information support at both genetic and metabolic levels for the mechanism of B. amyloliquefaciens ZZ7 to synthesize PLO compounds, and provides a direction for the subsequent genetic modification of ZZ7 to solve PLO from the source in the MFB.

Effects of different storage containers on the flavor characteristics of Jiangxiangxing baijiu.

Storage is a key factor controlling the quality of Jiangxiangxing baijiu, and storage time and the type of storage container play crucial roles in shaping the baijiu's distinct flavor. To investigate the influence of storage containers on the flavor characteristics of Jiangxiangxing baijiu, the sensory qualities, flavor components, and metal ions of Jiangxiangxing baijiu were measured during 24 months of storage in a pottery jar or a stainless steel tank. The results showed that Jiangxiangxing baijiu preserved in a pottery jar was superior to that stored in a stainless steel tank. A total of 96 flavor substances were detected, and 17 key flavor characteristic substances were screened by combining the results of odor activity values (OAV) and orthogonal partial least squares-discriminant analysis (OPLS-DA). A correlation heat map and redundancy analysis (RDA) showed that aluminum, cadmium, iron, cobalt, magnesium, potassium, and copper ions promoted the formation of key characteristic substances including diethoxymethane, lactic acid, 2,3-dimethyl-5-ethylpyrazine, 1-hexanol, and 2-methyl-1-propanol. Overall, the results show that 24-month pottery jar storage can promote the flavor quality of Jiangxiangxing baijiu. This study established a theoretical foundation to select the appropriate storage conditions and control the flavor quality of Jiangxiangxing baijiu.

CX3CR1 deficiency-induced TIL tumor restriction as a novel addition for CAR-T design in solid malignancies.

Advances in the understanding of the tumor microenvironment have led to development of immunotherapeutic strategies, such as chimeric antigen receptor T cells (CAR-Ts). However, despite success in blood malignancies, CAR-T therapies in solid tumors have been hampered by their restricted infiltration. Here, we used our understanding of early cytotoxic lymphocyte infiltration of human lymphocytes in solid tumors in vivo to investigate the receptors in normal, adjacent, and tumor tissues of primary non-small-cell lung cancer specimens. We found that CX3CL1-CX3CR1 reduction restricts cytotoxic cells from the solid-tumor bed, contributing to tumor escape. Based on this, we designed a CAR-T construct using the well-established natural killer group 2, member D (NKG2D) CAR-T expression together with overexpression of CX3CR1 to promote their infiltration. These CAR-Ts infiltrate tumors at higher rates than control-activated T cells or IL-15-overexpressing NKG2D CAR-Ts. This construct also had similar functionality in a liver-cancer model, demonstrating potential efficacy in other solid malignancies.

Combined nivolumab and ipilimumab with or without stereotactic body radiation therapy for advanced Merkel cell carcinoma: a randomised, open label, phase 2 trial.

BACKGROUND: Merkel cell carcinoma is among the most aggressive and lethal of primary skin cancers, with a high rate of distant metastasis. Anti-programmed death receptor 1 (anti-PD-1) and programmed death ligand 1 (PD-L1) monotherapy is currently standard of care for unresectable, recurrent, or metastatic Merkel cell carcinoma. We assessed treatment with combined nivolumab plus ipilimumab, with or without stereotactic body radiotherapy (SBRT) in patients with advanced Merkel cell carcinoma as a first-line therapy or following previous treatment with anti-PD-1 and PD-L1 monotherapy. METHODS: In this randomised, open label, phase 2 trial, we randomly assigned adults from two cancer sites in the USA (one in Florida and one in Ohio) to group A (combined nivolumab and ipilimumab) or group B (combined nivolumab and ipilimumab plus SBRT) in a 1:1 ratio. Eligible patients were aged at least 18 years with histologically proven advanced stage (unresectable, recurrent, or stage IV) Merkel cell carcinoma, a minimum of two tumour lesions measureable by CT, MRI or clinical exam, and tumour tissue available for exploratory biomarker analysis. Patients were stratified by previous immune-checkpoint inhibitor (ICI) status to receive nivolumab 240 mg intravenously every 2 weeks plus ipilimumab 1 mg/kg intravenously every 6 weeks (group A) or the same schedule of combined nivolumab and ipilimumab with the addition of SBRT to at least one tumour site (24 Gy in three fractions at week 2; group B). Patients had to have at least two measurable sites of disease so one non-irradiated site could be followed for response. The primary endpoint was objective response rate (ORR) in all randomly assigned patients who received at least one dose of combined nivolumab and ipilimumab. ORR was defined as the proportion of patients with a complete response or partial response per immune-related Response Evaluation Criteria in Solid Tumours. Response was assessed every 12 weeks. Safety was assessed in all patients. This trial is registered with ClinicalTrials.gov, NCT03071406. FINDINGS: 50 patients (25 in both group A and group B) were enrolled between March 14, 2017, and Dec 21, 2021, including 24 ICI-naive patients (13 [52%] of 25 group A patients and 11 [44%] of 25 group B patients]) and 26 patients with previous ICI (12 [48%] of 25 group A patients and 14 [56%] of 25 group B patients]). One patient in group B did not receive SBRT due to concerns about excess toxicity. Median follow-up was 14·6 months (IQR 9·1-26·5). Two patients in group B were excluded from the analysis of the primary endpoint because the target lesions were irradiated and so the patients were deemed non-evaluable. Of the ICI-naive patients, 22 (100%) of 22 (95% CI 82-100) had an objective response, including nine (41% [95% CI 21-63]) with complete response. Of the patients who had previously had ICI exposure, eight (31%) of 26 patients (95% CI 15-52) had an objective response and four (15% [5-36]) had a complete response. No significant differences in ORR were observed between groups A (18 [72%] of 25 patients) and B (12 [52%] of 23 patients; p=0·26). Grade 3 or 4 treatment-related adverse events were observed in 10 (40%) of 25 patients in group A and 8 (32%) of 25 patients in group B. INTERPRETATION: First-line combined nivolumab and ipilimumab in patients with advanced Merkel cell carcinoma showed a high ORR with durable responses and an expected safety profile. Combined nivolumab and ipilimumab also showed clinical benefit in patients with previous anti-PD-1 and PD-L1 treatment. Addition of SBRT did not improve efficacy of combined nivolumab and ipilimumab. The combination of nivolumab and ipilimumab represents a new first-line and salvage therapeutic option for advanced Merkel cell carcinoma. FUNDING: Bristol Myers Squibb Rare Population Malignancy Program.

Immunodepletion of MDSC by AMV564, a novel bivalent, bispecific CD33/CD3 T cell engager, ex vivo in MDS and melanoma.

We have reported previously that CD33hi myeloid-derived suppressor cells (MDSCs) play a direct role in the pathogenesis of myelodysplastic syndromes (MDSs) and that their sustained activation contributes to hematopoietic and immune impairment, including modulation of PD1/PDL1. MDSCs can also limit the clinical activity of immune checkpoint inhibition in solid malignancies. We hypothesized that depletion of MDSCs may ameliorate resistance to checkpoint inhibitors and, hence, targeted them with AMV564 combined with anti-PD1 in MDS bone marrow (BM) mononuclear cells (MNCs) enhanced activation of cytotoxic T cells. AMV564 was active in vivo in a leukemia xenograft model when co-administered with healthy donor peripheral blood MNCs (PBMCs). Our findings provide a strong rationale for clinical investigation of AMV564 as a single agent or in combination with an anti-PD1 antibody and in particular for treatment of cancers resistant to checkpoint inhibitors.

BCL11B is positioned upstream of PLZF and RORγt to control thymic development of mucosal-associated invariant T cells and MAIT17 program.

Mucosal-associated invariant T (MAIT) cells recognize microbial riboflavin metabolites presented by MR1 and play role in immune responses to microbial infections and tumors. We report here that absence of the transcription factor (TF) Bcl11b in mice alters predominantly MAIT17 cells in the thymus and further in the lung, both at steady state and following Salmonella infection. Transcriptomics and ChIP-seq analyses show direct control of TCR signaling program and position BCL11B upstream of essential TFs of MAIT17 program, including RORγt, ZBTB16 (PLZF), and MAF. BCL11B binding at key MAIT17 and at TCR signaling program genes in human MAIT cells occurred mostly in regions enriched for H3K27Ac. Unexpectedly, in human MAIT cells, BCL11B also bound at MAIT1 program genes, at putative active enhancers, although this program was not affected in mouse MAIT cells in the absence of Bcl11b. These studies endorse BCL11B as an essential TF for MAIT cells both in mice and humans.

Constitutively Activated DAP12 Induces Functional Anti-Tumor Activation and Maturation of Human Monocyte-Derived DC.

Dendritic cells (DCs) are professional antigen presenting cells with a great capacity for cross-presentation of exogenous antigens from which robust anti-tumor immune responses ensue. However, this function is not always available and requires DCs to first be primed to induce their maturation. In particular, in the field of DC vaccine design, currently available methodologies have been limited in eliciting a sustained anti-tumor immune response. Mechanistically, part of the maturation response is influenced by the presence of stimulatory receptors relying on ITAM-containing activating adaptor molecules like DAP12, that modulates their function. We hypothesize that activating DAP12 in DC could force their maturation and enhance their potential anti-tumor activity for therapeutic intervention. For this purpose, we developed constitutively active DAP12 mutants that can promote activation of monocyte-derived DC. Here we demonstrate its ability to induce the maturation and activation of monocyte-derived DCs which enhances migration, and T cell stimulation in vitro using primary human cells. Moreover, constitutively active DAP12 stimulates a strong immune response in a murine melanoma model leading to a reduction of tumor burden. This provides proof-of-concept for investigating the pre-activation of antigen presenting cells to enhance the effectiveness of anti-tumor immunotherapies.

MicroRNA-155 governs SHIP-1 expression and localization in NK cells and regulates subsequent infiltration into murine AT3 mammary carcinoma.

NK cell migration and activation are crucial elements of tumor immune surveillance. In mammary carcinomas, the number and function of NK cells is diminished, despite being positively associated with clinical outcome. MicroRNA-155 (miR-155) has been shown to be an important regulator of NK cell activation through its interaction with SHIP-1 downstream of inhibitory NK receptor signaling, but has not been explored in regard to NK cell migration. Here, we explored the migratory potential and function of NK cells in subcutaneous AT3 in mice lacking miR-155. Without tumor, these bic/miR-155-/- mice possess similar numbers of NK cells that exhibit comparable surface levels of cytotoxic receptors as NK cells from wild-type (WT) mice. Isolated miR-155-/- NK cells also exhibit equivalent cytotoxicity towards tumor targets in vitro compared to isolated WT control NK cells, despite overexpression of known miR-155 gene targets. NK cells isolated from miR-155-/- mice exhibit impaired F-actin polymerization and migratory capacity in Boyden-chamber assays in response chemokine (C-C motif) ligand 2 (CCL2). This migratory capacity could be normalized in the presence of SHIP-1 inhibitors. Of note, miR-155-/- mice challenged with mammary carcinomas exhibited heightened tumor burden which correlated with a lower number of tumor-infiltrating NK1.1+ cells. Our results support a novel, physiological role for SHIP-1 in the control of NK cell tumor trafficking, and implicate miR-155 in the regulation of NK cell chemotaxis, in the context of mammary carcinoma. This may implicate dysfunctional NK cells in the lack of tumor clearance in mice.

CD45 Phosphatase Inhibits STAT3 Transcription Factor Activity in Myeloid Cells and Promotes Tumor-Associated Macrophage Differentiation.

Recruitment of monocytic myeloid-derived suppressor cells (MDSCs) and differentiation of tumor-associated macrophages (TAMs) are the major factors contributing to tumor progression and metastasis. We demonstrated that differentiation of TAMs in tumor site from monocytic precursors was controlled by downregulation of the activity of the transcription factor STAT3. Decreased STAT3 activity was caused by hypoxia and affected all myeloid cells but was not observed in tumor cells. Upregulation of CD45 tyrosine phosphatase activity in MDSCs exposed to hypoxia in tumor site was responsible for downregulation of STAT3. This effect was mediated by the disruption of CD45 protein dimerization regulated by sialic acid. Thus, STAT3 has a unique function in the tumor environment in controlling the differentiation of MDSC into TAM, and its regulatory pathway could be a potential target for therapy.

Phase I/II Study of Metastatic Melanoma Patients Treated with Nivolumab Who Had Progressed after Ipilimumab.

The checkpoint inhibitor nivolumab is active in patients with metastatic melanoma who have failed ipilimumab. In this phase I/II study, we assessed nivolumab's safety in 92 ipilimumab-refractory patients with unresectable stage III or IV melanoma, including those who experienced grade 3-4 drug-related toxicity to ipilimumab. We report long-term survival, response duration, and biomarkers in these patients after nivolumab treatment (3 mg/kg) every 2 weeks for 24 weeks, then every 12 weeks for up to 2 years, with or without a multipeptide vaccine. The response rate for ipilimumab-refractory patients was 30% (95% CI, 21%-41%). The median duration of response was 14.6 months, median progression-free survival was 5.3 months, and median overall survival was 20.6 months, when patients were followed up for a median of 16 months. One- and 2-year survival rates were 68.4% and 31.2%, respectively. Ipilimumab-naïve and ipilimumab-refractory patients showed no significant difference in survival. The 21 patients with prior grade 3-4 toxicity to ipilimumab that was managed with steroids tolerated nivolumab well, with 62% (95% CI, 38%-82%) having complete or partial responses or stabilized disease at 24 weeks. High numbers of myeloid-derived suppressor cells (MDSC) were associated with poor survival. Thus, survival and long-term safety were excellent in ipilimumab-refractory patients treated with nivolumab. Prior grade 3-4 immune-related adverse effects from ipilimumab were not indicative of nivolumab toxicities, and patients had a high overall rate of remission or stability at 24 weeks. Prospectively evaluating MDSC numbers before treatment could help assess the expected benefit of nivolumab.

Effects of notch signaling on regulation of myeloid cell differentiation in cancer.

Functionally altered myeloid cells play an important role in immune suppression in cancer, in angiogenesis, and in tumor cells' invasion and metastases. Here, we report that inhibition of Notch signaling in hematopoietic progenitor cells (HPC), myeloid-derived suppressor cells (MDSC), and dendritic cells is directly involved in abnormal myeloid cell differentiation in cancer. Inhibition of Notch signaling was caused by the disruption of the interaction between Notch receptor and transcriptional repressor CSL, which is normally required for efficient transcription of target genes. This disruption was the result of serine phosphorylation of Notch. We demonstrated that increased activity of casein kinase 2 (CK2) observed in HPC and in MDSC could be responsible for the phosphorylation of Notch and downregulation of Notch signaling. Inhibition of CK2 by siRNA or by pharmacological inhibitor restored Notch signaling in myeloid cells and substantially improved their differentiation, both in vitro and in vivo. This study demonstrates a novel mechanism regulation of Notch signaling in cancer. This may suggest a new perspective for pharmacological regulation of differentiation of myeloid cells in cancer.

Induction of myelodysplasia by myeloid-derived suppressor cells.

Myelodysplastic syndromes (MDS) are age-dependent stem cell malignancies that share biological features of activated adaptive immune response and ineffective hematopoiesis. Here we report that myeloid-derived suppressor cells (MDSC), which are classically linked to immunosuppression, inflammation, and cancer, were markedly expanded in the bone marrow of MDS patients and played a pathogenetic role in the development of ineffective hematopoiesis. These clonally distinct MDSC overproduce hematopoietic suppressive cytokines and function as potent apoptotic effectors targeting autologous hematopoietic progenitors. Using multiple transfected cell models, we found that MDSC expansion is driven by the interaction of the proinflammatory molecule S100A9 with CD33. These 2 proteins formed a functional ligand/receptor pair that recruited components to CD33's immunoreceptor tyrosine-based inhibition motif (ITIM), inducing secretion of the suppressive cytokines IL-10 and TGF-ß by immature myeloid cells. S100A9 transgenic mice displayed bone marrow accumulation of MDSC accompanied by development of progressive multilineage cytopenias and cytological dysplasia. Importantly, early forced maturation of MDSC by either all-trans-retinoic acid treatment or active immunoreceptor tyrosine-based activation motif­bearing (ITAM-bearing) adapter protein (DAP12) interruption of CD33 signaling rescued the hematologic phenotype. These findings indicate that primary bone marrow expansion of MDSC driven by the S100A9/CD33 pathway perturbs hematopoiesis and contributes to the development of MDS.

Regulation of dendritic cell differentiation in bone marrow during emergency myelopoiesis.

Although accumulation of dendritic cell (DC) precursors occurs in bone marrow, the terminal differentiation of these cells takes place outside bone marrow. The signaling, regulating this process, remains poorly understood. We demonstrated that this process could be differentially regulated by Notch ligands: Jagged-1 (Jag1) and Delta-like ligand 1 (Dll1). In contrast to Dll1, Jag1, in vitro and during induced myelopoiesis in vivo, prevented DC differentiation by promoting the accumulation of their precursors. Although both ligands activated Notch in hematopoietic progenitor cells, they had an opposite effect on Wnt signaling. Dll1 activated Wnt pathways, whereas Jag1 inhibited it via downregulation of the expression of the Wnt receptors Frizzled (Fzd). Jag1 suppressed fzd expression by retaining histone deacetylase 1 in the complex with the transcription factor CSL/CBF-1 on the fzd promoter. Our results suggest that DC differentiation, during induced myelopoiesis, can be regulated by the nature of the Notch ligand expressed on adjacent stroma cells.

Epigenetic silencing of retinoblastoma gene regulates pathologic differentiation of myeloid cells in cancer.

Two major populations of myeloid-derived suppressor cells (MDSCs), monocytic MDSCs (M-MDSCs) and polymorphonuclear MDSCs (PMN-MDSCs) regulate immune responses in cancer and other pathologic conditions. Under physiologic conditions, Ly6C(hi)Ly6G(-) inflammatory monocytes, which are the normal counterpart of M-MDSCs, differentiate into macrophages and dendritic cells. PMN-MDSCs are the predominant group of MDSCs that accumulates in cancer. Here we show that a large proportion of M-MDSCs in tumor-bearing mice acquired phenotypic, morphological and functional features of PMN-MDSCs. Acquisition of this phenotype, but not the functional attributes of PMN-MDSCs, was mediated by transcriptional silencing of the retinoblastoma gene through epigenetic modifications mediated by histone deacetylase 2 (HDAC-2). These data demonstrate a new regulatory mechanism of myeloid cells in cancer.

Antigen-specific CD4(+) T cells regulate function of myeloid-derived suppressor cells in cancer via retrograde MHC class II signaling.

Myeloid-derived suppressor cells (MDSC) play a major role in cancer-related immune suppression, yet the nature of this suppression remains controversial. In this study, we evaluated the ability of MDSCs to elicit CD4(+) T-cell tolerance in different mouse tumor models. In contrast to CD8(+) T-cell tolerance, which could be induced by MDSCs in all the tumor models tested, CD4(+) T-cell tolerance could be elicited in only one of the models (MC38) in which a substantial level of MHC class II was expressed on MDSCs compared with control myeloid cells. Mechanistic investigations revealed that MDSCs deficient in MHC class II could induce tolerance to CD8(+) T cells but not to CD4(+) T cells. Unexpectedly, antigen-specific CD4(+) T cells (but not CD8(+) T cells) could dramatically enhance the immune suppressive activity of MDSCs by converting them into powerful nonspecific suppressor cells. This striking effect was mediated by direct cell-cell contact through cross-linking of MHC class II on MDSCs. We also implicated an Ets-1 transcription factor-regulated increase in expression of Cox-2 and prostaglandin E2 in MDSCs in mediating this effect. Together, our findings suggest that activated CD4(+) T cells that are antigen specific may enhance the immune suppressive activity of MDSCs, a mechanism that might serve normally as a negative feedback loop to control immune responses that becomes dysregulated in cancer.

Tumor-infiltrating myeloid cells induce tumor cell resistance to cytotoxic T cells in mice.

Cancer immunotherapeutic approaches induce tumor-specific immune responses, in particular CTL responses, in many patients treated. However, such approaches are clinically beneficial to only a few patients. We set out to investigate one possible explanation for the failure of CTLs to eliminate tumors, specifically, the concept that this failure is not dependent on inhibition of T cell function. In a previous study, we found that in mice, myeloid-derived suppressor cells (MDSCs) are a source of the free radical peroxynitrite (PNT). Here, we show that pre-treatment of mouse and human tumor cells with PNT or with MDSCs inhibits binding of processed peptides to tumor cell-associated MHC, and as a result, tumor cells become resistant to antigen-specific CTLs. This effect was abrogated in MDSCs treated with a PNT inhibitor. In a mouse model of tumor-associated inflammation in which the antitumor effects of antigen-specific CTLs are eradicated by expression of IL-1ß in the tumor cells, we determined that therapeutic failure was not caused by more profound suppression of CTLs by IL-1ß-expressing tumors than tumors not expressing this proinflammatory cytokine. Rather, therapeutic failure was a result of the presence of PNT. Clinical relevance for these data was suggested by the observation that myeloid cells were the predominant source of PNT in human lung, pancreatic, and breast cancer samples. Our data therefore suggest what we believe to be a novel mechanism of MDSC-mediated tumor cell resistance to CTLs.

HIF-1α regulates function and differentiation of myeloid-derived suppressor cells in the tumor microenvironment.

Myeloid-derived suppressor cells (MDSCs) are a major component of the immune-suppressive network described in cancer and many other pathological conditions. We demonstrate that although MDSCs from peripheral lymphoid organs and the tumor site share similar phenotype and morphology, these cells display profound functional differences. MDSC from peripheral lymphoid organs suppressed antigen-specific CD8(+) T cells but failed to inhibit nonspecific T cell function. In sharp contrast, tumor MDSC suppressed both antigen-specific and nonspecific T cell activity. The tumor microenvironment caused rapid and dramatic up-regulation of arginase I and inducible nitric oxide synthase in MDSC, which was accompanied by down-regulation of nicotinamide adenine dinucleotide phosphate-oxidase and reactive oxygen species in these cells. In contrast to MDSC from the spleen, MDSC from the tumor site rapidly differentiated into macrophages. Exposure of spleen MDSC to hypoxia resulted in the conversion of these cells to nonspecific suppressors and their preferential differentiation to macrophages. Hypoxia-inducible factor (HIF) 1α was found to be primarily responsible for the observed effects of the tumor microenvironment on MDSC differentiation and function. Thus, hypoxia via HIF-1α dramatically alters the function of MDSC in the tumor microenvironment and redirects their differentiation toward tumor-associated macrophages, hence providing a mechanistic link between different myeloid suppressive cells in the tumor microenvironment.

Regulation of dendritic cell differentiation and function by Notch and Wnt pathways.

The process of dendritic cell differentiation is governed by a tightly controlled signaling network regulated by cytokines and direct interaction between progenitor cells and bone marrow stroma. Notch signaling represents one of the major pathways activated during direct interaction between hematopoietic progenitor cells and bone marrow stroma. Wnt pathway is activated by soluble proteins produced by bone marrow stroma. Until recently, the role of Notch and Wnt signaling in the development of myeloid cells and dendritic cells in particular remained unclear. In this review, we discuss recent exciting findings that shed light on the critical role of Notch and Wnt pathways, their interaction in differentiation and function of dendritic cells, and their impact on immune responses.

Notch and wingless signaling cooperate in regulation of dendritic cell differentiation.

Dendritic cell (DC) differentiation is regulated by stroma via a network of soluble and cell-bound factors. Notch is one of the major elements of this network. Its role in DC differentiation, however, is controversial. Here, we demonstrate that activation of Notch signaling in hematopoietic progenitor cells (HPCs) promoted differentiation of conventional DCs via activation of the canonical Wingless (Wnt) pathway. Inhibition of the Wnt pathway abrogated the effect of Notch on DC differentiation. The fact that activation of the Wnt pathway in Notch-1-deficient embryonic stem cells restored DC differentiation indicates that Wnt signaling is downstream of the Notch pathway in regulating DC differentiation. Notch signaling activated the Wnt pathway in HPCs via expression of multiple members of the Frizzled family of Wnt receptors, which was directly regulated by the CSL (RPB-Jkappa) transcription factor. Thus, these data suggest a model of DC differentiation via cooperation between Wnt and Notch pathways.