Ginger polysaccharide promotes myeloid-derived suppressor cell apoptosis by regulating lipid metabolism

Recently, targeting myeloid-derived suppressor cells (MDSCs) which mainly play an immunosuppressive role in tumor microenvironment has become a hot spot in tumor immunotherapy. This study focuses on biological effect of ginger polysaccharide extracted from natural plants on promoting apoptosis of MDSCs by regulating lipid metabolism. An MTT assay was used to detect the inhibitory effect of ginger polysaccharide on the growth of an MDSC-like cell line (MSC-2). The apoptosis-promoting effect of ginger polysaccharide on MSC-2 cells was detected by flow cytometry. Expression levels of apoptosis proteins (caspase 9 and Bcl-2) and lipid metabolism enzymes (fatty acid synthase (FASN) and diacylglycerol acyltransferase 2) in MSC-2 cells treated with different concentrations of ginger polysaccharide were detected by western blot assay. Nile red staining was used to quantitatively detect the effect of ginger polysaccharide on lipid droplet synthesis. Ginger polysaccharide inhibited proliferation of MSC-2 cells and promoted their apoptosis by upregulating pro-apoptotic caspase 9 protein, downregulating anti-apoptotic Bcl-2 protein, inhibiting expression of FASN and diacylglycerol acyltransferase 2 (key enzymes in fatty acid synthesis and lipid droplet formation, respectively). Ginger polysaccharide promoted apoptosis of MDSCs by regulating key lipid metabolism enzymes, inhibiting fatty acid synthesis and lipid droplet accumulation, and reducing the energy supply of cells.

Tailoring Chemoimmunostimulant Bioscaffolds for Inhibiting Tumor Growth and Metastasis after Incomplete Microwave Ablation

Microwave ablation has attracted the most attention as a locoregional therapeutic method for solid neoplasms. However, the high incidence of incomplete ablation that could promote the rapid cancer progression still remains a challenge in clinic. Herein, we found that the high invasiveness of residual tumor following incomplete microwave ablation (iMWA) is mainly due to the myeloid cell-mediated immunosuppression. Accordingly, we develop a biohydrogel scaffold-enabled chemoimmunotherapeutic strategy by targeting myeloid cells with a phosphoinositide 3-kinase γ (PI3Kγ) inhibitor (IPI549) to synergize with immunostimulatory chemotherapy (Oxaliplatin, OX) for post-ablative cancer therapy. With several tumor mouse models, we reveal that OX&IPI549@Gel-based localized chemoimmunotherapy can substantially suppress the growth of tumor post-iMWA, simultaneously evoke robust systemic anticancer immunity to inhibit metastatic spread, and offer strong long-term immunological memory functions against tumor rechallenge. Besides, this work proposes a potential opportunity for precision medicine by utilizing a mechanism-based rationale to the adoption of our pre-existing arsenal of anticancer immunotherapeutic schedule.

[Mechanism of Xiaowugui decoction for treating collagen-induced arthritis in mice]

OBJECTIVE

To explore the mechanism of Xiaowugui decoction (XWGD) decoction in treating rheumatoid arthritis (RA) in mice.

METHODS

Healthy male DBA/1 mice were used for CIA modeling. Twenty-five CIA mice with successful modeling and similar arthritis index (AI) scores were randomized equally into model group (CIA), methotrexate (MTX) group, and low-, medium-, and high-dose XWGD groups (0.975, 1.95, and 3.9 g/mL, respectively), with another 5 normal mice as the normal control group. The mice in normal control and CIA groups were given saline once a day, those in MTX group were given 0.1 mg/mL MTX once a week, and those in XWGD groups were treated daily via garage of XWGD containing crude drugs of different doses for 28 consecutive days. The AI score and HE staining were used to evaluate the changes in the joints of the CIA mice. The effect of XWGD on Th1, Th17, MDSC, G-MDSC and M-MDSC cells were evaluated with flow cytometry.

RESULTS

Treatment with MTX and different doses of XWGD significantly decreased the AI score of the mice and relieved joint inflammation as compared with the model group (P < 0.05), and a higher dose of XWGD decoction produced a stronger therapeutic effect. Compared with those in CIA model group, the mice in MTX and XWGD treatment groups showed significantly decreased percentages of Th1, Th17 and M-MDSC cells in the spleen and increased percentages of G-MDSC cells (P < 0.01), and these changes were more conspicuous with a higher dose of XWGD. Correlation analysis showed that Th1 and Th17 cells were positively correlated with M-MDSC and negatively correlated with G-MDSC cells (P < 0.01).

CONCLUSIONS

XWGD can improve joint inflammation in CIA mice by increasing the percentages of G-MDSC cells and decreasing the percentages of M-MDSC, Th1 and Th17 cells, and a high dose of XWGD can produce an equivalent therapeutic effect to methotrexate but with better safety.

Effect of Graphene Oxide Nanoparticles on Differentiation of Myeloid Suppressor Cells

We studied the effect of graphene oxide (GO) nanoparticles on differentiation of human myeloid suppressor cells (MDSC) in an in vitro system. Separated mononuclear cells of healthy donors were induced with cytokines (IL-6 and GM-CSF) into the MDSC phenotype (both polymorphonuclear (PMN-MDSC) and monocyte (M-MDSC) subsets of these cells were taken into account). Pegylated GO nanoparticles (GO-PEG; mean size 569±14 nm, PEG content ~20%) were used. GO-PEG in low concentrations (2.5 and 5 μg/ml) increased the percentage of MDSC in cultures, but reduced their content in high concentration (10 μg/ml). After exposure to GO-PEG (2.5 and 5 μg/ml), the MDSC content increased at the expense of M-MDSC, while the level of PMN-MDSC did not change. The decrease in MDSC levels after exposure to high doses of GO-PEG (10 μg/ml) was due to a decrease in PMN-MDSC. Thus, GO-PEG nanoparticles can oppositely regulate differentiation of MDSC by inhibiting or stimulating differentiation of these cells depending on the concentration.

Tadalafil has biologic activity in human melanoma. Results of a pilot trial with Tadalafil in patients with metastatic Melanoma (TaMe)

Myeloid-derived suppressor cells (MDSCs) are known to play a critical role in the suppression of T cell antitumor responses. Our preclinical data showed that the phosphodiesterase (PDE)-5 inhibitor sildenafil impaired MDSC functions, enhanced intratumoral T cell activity and prolonged survival of melanoma-bearing mice. In this study, we evaluated biologic effects, safety and efficacy of palliative treatment with the PDE-5 inhibitor tadalafil in metastatic melanoma patients. We conducted an open-label, dose de-escalation trial with tadalafil in pretreated metastatic melanoma patients. Tumor and peripheral blood samples were taken before and 4 weeks after the start of treatment. Samples were investigated by immunohistochemistry and FACS analysis, for different immune subsets with numbers of CD8⁺ tumor-infiltrating lymphocytes (TIL) as primary end point. Stable disease was achieved in 3/12 patients (25%). Median progression-free survival was 4.6 mo (range 0.7–7.1), median overall survival (OS) 8.5 mo (range 2.7–23.7). The treatment was well tolerated. Stable patients displayed significantly higher numbers of CD8⁺ TIL in the center of metastases before treatment as compared with progressive patients. Upon the therapy, they showed increased expression of ζ-chain (used as a marker of T cell activation) in CD8⁺ and CD4⁺TILs and CD8⁺T cells in the peripheral blood as compared with baseline. Our study suggests that the PDE-5 inhibitor tadalafil can improve clinical outcome of advanced melanoma patients by enhancing antitumor immunity and highlights its potential application in combined melanoma immunotherapy.

Energy metabolism drives myeloid-derived suppressor cell differentiation and functions in pathology

Over the last decade, a heterogeneous population of immature myeloid cells with major regulatory functions has been described in cancer and other pathologic conditions and ultimately defined as MDSCs. Most of the early work on the origins and functions of MDSCs has been in murine and human tumor bearers in which MDSCs are known to be immunosuppressive and to result in both reduced immune surveillance and antitumor cytotoxicity. More recent studies, however, suggest that expansion of these immature myeloid cells may be linked to most, if not all, chronic and acute inflammatory processes. The universal expansion to inflammatory stimuli of MDSCs suggests that these cells may be more of a normal component of the inflammatory response (emergency myelopoiesis) than simply a pathologic response to a growing tumor. Instead of an adverse immunosuppressive response, expansion of these immature myeloid cell populations may result from a complex balance between increased immune surveillance and dampened adaptive immune responses that are common to many inflammatory responses. Within this scenario, new pathways of metabolic reprogramming are emerging as drivers of MDSC differentiation and functions in cancer and inflammatory disorders, crucially linking metabolic syndrome to inflammatory processes.

Targeting neutrophilic inflammation in severe neutrophilic asthma: can we target the disease-relevant neutrophil phenotype?

In severe, neutrophilic asthma, neutrophils are thought to have an important role in both the maintenance of the disease and during exacerbations. These patients often display excessive, mucosal airway inflammation with unresolving neutrophilia. Because this variant of asthma is poorly controlled by glucocorticoids, specific pharmacologic targeting of neutrophils seems a plausible therapeutic approach. However, most attempts with this approach have failed in the clinic. We propose that this could be attributed, in part, to an incomplete understanding of the emerging new insights underlying neutrophil homeostasis and life span, neutrophil reverse transmigration, neutrophil phenotypes, and neutrophil transdifferentiation in human health and disease. Of clinical relevance, recent translational studies have started to uncover distinct neutrophil subsets in humans, namely mature and hypersegmented phenotypes that have bimodal immunomodulatory functions during an acute inflammatory response. In this review, we will elaborate on some of the novel insights in neutrophil biology and attempt to translate them into potential consequences for pharmacologic intervention of severe neutrophilic asthma. We speculate that the disease-relevant neutrophil phenotype should be targeted selectively without compromising the immunomodulatory functions essential for homeostasis and pulmonary immunity. However, the identity and exact functional role of distinct neutrophil phenotypes in inflammatory diseases of the human airway remain elusive.

Salmonella-mediated tumor regression involves targeting of tumor myeloid suppressor cells causing a shift to M1-like phenotype and reduction in suppressive capacity

The effectiveness of attenuated Salmonella in inhibiting tumor growth has been demonstrated in many therapeutic models, but the precise mechanisms remain incompletely understood. In this study, we show that the anti-tumor capacity of Salmonella depends on a functional MyD88-TLR pathway and is independent of adaptive immune responses. Since myeloid suppressor cells play a critical role in tumor growth, we investigated the consequences of Salmonella treatment on myeloid cell recruitment, phenotypic characteristics, and functional activation in spleen and tumor tissue of B16.F1 melanoma-bearing mice. Salmonella treatment led to increased accumulation of splenic and intratumoral CD11b(+)Gr-1(+) myeloid cells, exhibiting significantly increased expression of various activation markers such as MHC class II, costimulatory molecules, and Sca-1/Ly6A proteins. Gene expression analysis showed that Salmonella treatment induced expression of iNOS, arginase-1 (ARG1), and IFN-γ in the spleen, but down-regulated IL-4 and TGF-β. Within the tumor, expression of iNOS, IFN-γ, and S100A9 was markedly increased, but ARG1, IL-4, TGF-β, and VEGF were inhibited. Functionally, splenic CD11b(+) cells maintained their suppressive capacity following Salmonella treatment, but intratumoral myeloid cells had significantly reduced suppressive capacity. Our findings demonstrate that administration of attenuated Salmonella leads to phenotypic and functional maturation of intratumoral myeloid cells making them less suppressive and hence enhancing the host's anti-tumor immune response. Modalities that inhibit myeloid suppressor cells may be useful adjuncts in cancer immunotherapy.

Differential effects of low-dose decitabine on immune effector and suppressor responses in melanoma-bearing mice

BACKGROUND

Low doses of the demethylating agent decitabine have been shown to enhance the sensitivity of tumors to immune effector cells and molecules through upregulation of tumor antigen presentation and apoptotic pathways. Effects on host immune effector and suppressor responses have not been well characterized.

METHODS

Mice bearing B16 melanoma were treated with low-dose decitabine, cytokine, interleukin-2 (IL-2), toll-like receptor 9 agonist ODN1826, and/or a viral vectored vaccine targeting the melanoma antigen Trp2. Lymphoid and myeloid effector and suppressor cells were examined both systemically and intratumorally with functional, flow cytometric, and polymerase chain reaction-based assays.

RESULTS

Enhancement of tumor growth delay was observed when decitabine was applied sequentially but not concurrently with IL-2. In contrast, complete responses and prolonged survival were observed when decitabine was applied with ODN1826 as therapy and with ODN1826 as a Trp2 vaccine adjuvant. Decitabine decreased natural killer and antigen-specific cellular immune responses when administered concurrently with IL-2 and with ODN1826; the Th1-associated transcription factor Tbet also decreased. T regulatory cells were not affected. When applied concurrently with ODN1826, decitabine increased macrophage cytotoxicity, M1 polarization, and dendritic cell activation. Myeloid-derived suppressor cells were reduced.

CONCLUSION

Low-dose decitabine promotes both anti- and pro-tumor host immune responses to immunotherapeutics in melanoma-bearing mice. Macrophage effector and dendritic cell activation increase, and myeloid suppressor cells decrease. Lymphoid effector responses, however, can be inhibited.

Myeloid-derived suppressor cells: mechanisms of action and recent advances in their role in transplant tolerance

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature hematopoietic precursors known to suppress immune responses in infection, chronic inflammation, cancer, and autoimmunity. In this paper, we review recent findings detailing their mode of action and discuss recent reports that suggest that MDSC are also expanded during transplantation and that modulation of MDSC can participate in preventing graft rejection as well as graft-versus-host disease.