Cutting edge: Flt3 ligand mediates STAT3-independent expansion but STAT3-dependent activation of myeloid-derived suppressor cells

Myeloid-derived suppressor cells prevent disruption of the gut barrier, preserve microbiota composition, and potentiate immunoregulatory pathways in a rat model of experimental autoimmune encephalomyelitis

Over-activated myeloid cells and disturbance in gut microbiota composition are critical factors contributing to the pathogenesis of Multiple Sclerosis (MS). Myeloid-derived suppressor cells (MDSCs) emerged as promising regulators of chronic inflammatory diseases, including autoimmune diseases. However, it remained unclear whether MDSCs display any therapeutic potential in MS, and how this therapy modulates gut microbiota composition. Here, we assessed the potential of in vitro generated bone marrow-derived MDSCs to ameliorate experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats and investigated how their application associates with the changes in gut microbiota composition. MDSCs differentiated with prostaglandin (PG)E2 (MDSC-PGE2) and control MDSCs (differentiated without PGE2) displayed strong immunosuppressive properties in vitro, but only MDSC-PGE2 significantly ameliorated EAE symptoms. This effect correlated with a reduced infiltration of Th17 and IFN-γ-producing NK cells, and an increased proportion of regulatory T cells in the CNS and spleen. Importantly, both MDSCs and MDSC-PGE2 prevented EAE-induced reduction of gut microbiota diversity, but only MDSC-PGE2 prevented the extensive alterations in gut microbiota composition following their early migration into Payer's patches and mesenteric lymph nodes. This phenomenon was related to the significant enrichment of gut microbial taxa with potential immunoregulatory properties, as well as higher levels of butyrate, propionate, and putrescine in feces. This study provides new insights into the host-microbiota interactions in EAE, suggesting that activated MDSCs could be potentially used as an efficient therapy for acute phases of MS. Considering a significant association between the efficacy of MDSC-PGE2 and gut microbiota composition, our findings also provide a rationale for further exploring the specific microbial metabolites in MS therapy.

Regulatory Dendritic Cells Induced by Bendamustine Are Associated With Enhanced Flt3 Expression and Alloreactive T-Cell Death

The growth factor Flt3 ligand (Flt3L) is central to dendritic cell (DC) homeostasis and development, controlling survival and expansion by binding to Flt3 receptor tyrosine kinase on the surface of DCs. In the context of hematopoietic cell transplantation, Flt3L has been found to suppress graft-versus-host disease (GvHD), specifically via host DCs. We previously reported that the pre-transplant conditioning regimen consisting of bendamustine (BEN) and total body irradiation (TBI) results in significantly reduced GvHD compared to cyclophosphamide (CY)+TBI. Pre-transplant BEN+TBI conditioning was also associated with greater Flt3 expression among host DCs and an accumulation of pre-cDC1s. Here, we demonstrate that exposure to BEN increases Flt3 expression on both murine bone marrow-derived DCs (BMDCs) and human monocyte-derived DCs (moDCs). BEN favors development of murine plasmacytoid DCs, pre-cDC1s, and cDC2s. While humans do not have an identifiable equivalent to murine pre-cDC1s, exposure to BEN resulted in decreased plasmacytoid DCs and increased cDC2s. BEN exposure and heightened Flt3 signaling are associated with a distinct regulatory phenotype, with increased PD-L1 expression and decreased ICOS-L expression. BMDCs exposed to BEN exhibit diminished pro-inflammatory cytokine response to LPS and induce robust proliferation of alloreactive T-cells. These proliferative alloreactive T-cells expressed greater levels of PD-1 and underwent increased programmed cell death as the concentration of BEN exposure increased. Alloreactive CD4⁺ T-cell death may be attributable to pre-cDC1s and provides a potential mechanism by which BEN+TBI conditioning limits GvHD and yields T-cells tolerant to host antigen.

Immunosuppressive Effects of Myeloid-Derived Suppressor Cells in Cancer and Immunotherapy

The primary function of myeloid cells is to protect the host from infections. However, during cancer progression or states of chronic inflammation, these cells develop into myeloid-derived suppressor cells (MDSCs) that play a prominent role in suppressing anti-tumor immunity. Overcoming the suppressive effects of MDSCs is a major hurdle in cancer immunotherapy. Therefore, understanding the mechanisms by which MDSCs promote tumor growth is essential for improving current immunotherapies and developing new ones. This review explores mechanisms by which MDSCs suppress T-cell immunity and how this impacts the efficacy of commonly used immunotherapies.

Identification and characterization of B220+/B220- subpopulations in murine Gr1+CD11b+ cells during tumorigenesis

Although all murine MDSCs are defined as Gr1⁺CD11b⁺, their true immunophenotype remains elusive. In this study, we found murine Gr1⁺CD11b⁺ cells can be divided into two subsets: Gr1⁺CD11b⁺B220^- and Gr1⁺CD11b⁺B220⁺, especially in the spleen tissues. Unlike the dominant B220^- subset, the B220⁺ subpopulation was not induced by tumor in vivo. Moreover, Gr1⁺CD11b⁺B220⁺ cells from tumor-bearing mice spleens were unable to induce arginase 1 and inducible nitric oxide synthase expression, inhibit T cell proliferation, or promote tumor growth in primary tumor site. Nevertheless, these cells suppressed tumor metastasis in vivo and reduced cancer cell motility in vitro, while Gr1⁺CD11b⁺B220^- cells from tumor-bearing mice spleens promoted tumor metastasis and enhanced cancer cell motility. Furthermore, both the polymorphonuclear (PMN-MDSCs) and monocytic MDSCs (Mo-MDSCs) could be further divided into B220^- and B220⁺ subsets; interestingly, tumor only induced the expansion of B220^- PMN-MDSCs and B220^- Mo-MDSCs, but not the B220⁺ counterparts. Compared with B220^- PMN-MDSCs and B220^- Mo-MDSCs, the Ly6G⁺Ly6C^-CD11b⁺B220⁺ and Ly6G^-Ly6C⁺CD11b⁺B220⁺ cells from tumor-bearing mice spleens exhibited a more mature phenotype without immunosuppressive activity. Additionally, IL-6 deficiency attenuated the tumor-induced accumulation of MDSCs, B220^- MDSCs and B220^- PMN-MDSCs but increased the percentages of Gr1⁺CD11b⁺B220⁺, Ly6G⁺Ly6C^-CD11b⁺B220⁺, and Ly6G^-Ly6C⁺CD11b⁺B220⁺ cells, indicating the opposing roles of the IL-6 signaling pathway in the expansion of B220^- MDSCs and their B220⁺ counterparts. Taken together, our findings indicate that the B220⁺ subset is a distinct subset of Gr1⁺CD11b⁺ cells functionally different from the B220^- subpopulation during tumorigenesis and induction of MDSCs to B220⁺ cells may be helpful for cancer therapy.

Analyzing One Cell at a TIME: Analysis of Myeloid Cell Contributions in the Tumor Immune Microenvironment

Tumor-mediated regulation of the host immune system involves an intricate signaling network that results in the tumor's inherent survival benefit. Myeloid cells are central in orchestrating the mechanisms by which tumors escape immune detection and continue their proliferative programming. Myeloid cell activation has historically been classified using a dichotomous system of classical (M1-like) and alternative (M2-like) states, defining general pro- and anti-inflammatory functions, respectively. Explosions in bioinformatics analyses have rapidly expanded the definitions of myeloid cell pro- and anti-inflammatory states with different combinations of tissue- and disease-specific phenotypic and functional markers. These new definitions have allowed researchers to target specific subsets of disease-propagating myeloid cells in order to modify or arrest the natural progression of the associated disease, especially in the context of tumor-immune interactions. Here, we discuss the myeloid cell contribution to solid tumor initiation and maintenance, and strategies to reprogram their phenotypic and functional fate, thereby disabling the network that benefits tumor survival.

High-density neutrophils in MGUS and multiple myeloma are dysfunctional and immune-suppressive due to increased STAT3 downstream signaling

To understand neutrophil impairment in the progression from MGUS through active MM, we investigated the function of mature, high-density neutrophils (HDNs), isolated from peripheral blood. In 7 MM, 3 MGUS and 3 healthy subjects by gene expression profile, we identified a total of 551 upregulated and 343 downregulated genes in MM-HDN, involved in chemokine signaling pathway and FC-gamma receptor mediated phagocytosis conveying in the activation of STAT proteins. In a series of 60 newly diagnosed MM and 30 MGUS patients, by flow-cytometry we found that HDN from MM, and to a lesser extend MGUS, had an up-regulation of the inducible FcγRI (also known as CD64) and a down-regulation of the constitutive FcγRIIIa (also known as CD16) together with a reduced phagocytic activity and oxidative burst, associated to increased immune-suppression that could be reverted by arginase inhibitors in co-culture with lymphocytes. In 43 consecutive newly-diagnosed MM patients, who received first-line treatment based on bortezomib, thalidomide and dexamethasone, high CD64 could identify at diagnosis patients with inferior median overall survival (39.5 versus 86.7 months, p = 0.04). Thus, HDNs are significantly different among healthy, MGUS and MM subjects. In both MGUS and MM neutrophils may play a role in supporting both the increased susceptibility to infection and the immunological dysfunction that leads to tumor progression.

Neutrophil Heterogeneity in Cancer: From Biology to Therapies

Neutrophils have been extensively described in the pathophysiology of autoimmune and infectious diseases. Accumulating evidence also suggests the important role of neutrophils in cancer progression through their interaction with cancer and immune cells in blood and in the tumor microenvironment (TME). Most studies have described neutrophils as key drivers of cancer progression, due to their involvement in various tumor promoting functions including proliferation, aggressiveness, and dissemination, as well as in immune suppression. However, such studies were focusing on late-stages of tumorigenesis, in which chronic inflammation had already developed. The role of tumor-associated neutrophils (TANs) at early stages of tumor development remains poorly described, though recent findings indicate that early-stage TANs may display anti-tumor properties. Beyond their role at tumor site, evidence supported by NLR retrospective studies and functional analyses suggest that blood neutrophils could also actively contribute to tumorigenesis. Hence, it appears that the phenotype and functions of neutrophils vary greatly during tumor progression, highlighting their heterogeneity. The origin of pro- or anti-tumor neutrophils is generally believed to arise following a change in cell state, from resting to activated. Moreover, the fate of neutrophils may also involve distinct differentiation programs yielding various subsets of pro or anti-tumor neutrophils. In this review, we will discuss the current knowledge on neutrophils heterogeneity across different tissues and their impact on tumorigenesis, as well as neutrophil-based therapeutic strategies that have shown promising results in pre-clinical studies, paving the way for the design of neutrophil-based next generation immunotherapy.

Alternatively activated macrophage-derived secretome stimulates ovarian cancer spheroid spreading through a JAK2/STAT3 pathway

High-grade serous ovarian cancer (HGSOC) metastasizes when tumor spheroids detach from the primary tumor and re-attach throughout the peritoneal cavity. Once the cancer cells have implanted in these new sites, the development of metastatic lesions is dependent on the disaggregation of cancer cells from the spheroids and subsequent expansion across the collagenous extracellular matrix (ECM). As HGSOC progresses an increase in alternatively activated macrophages (AAMs) in the surrounding ascites fluid has been observed and AAMs have been shown to enhance tumor invasion and growth in a wide range of cancers. We hypothesized that soluble factors from AAMs in the peritoneal microenvironment promote the disaggregation of ovarian cancer spheroids across the underlying ECM. We determined that co-culture with AAMs significantly increased HGSOC spheroid spreading across a collagen matrix. Multivariate modeling identified AAM-derived factors that correlated with enhanced spread of HGSOC spheroids and experimental validation showed that each individual cell line responded to a distinct AAM-derived factor (FLT3L, leptin, or HB-EGF). Despite this ligand-level heterogeneity, we determined that the AAM-derived factors utilized a common signaling pathway to induce spheroid spreading: JAK2/STAT3 activation followed by MMP-9 mediated spreading. Furthermore, immunostaining demonstrated that FLT3, LEPR, EGFR, and pSTAT3 were upregulated in metastases in HGSOC patients, with substantial patient-to-patient heterogeneity. These results suggest that inhibiting individual soluble factors will not inhibit AAM-induced effects across a broad group of patients; instead, the downstream JAK2/STAT3/MMP-9 pathway should be examined as potential therapeutic targets to slow metastasis in ovarian cancer.

Myeloid-Derived Suppressor Cells in Hematologic Diseases: Promising Biomarkers and Treatment Targets

Myeloid-derived suppressor cells (MDSC) are a heterogeneous group of immature myeloid cells that exist at very low numbers in healthy subjects but can expand significantly in malignant, infectious, and chronic inflammatory diseases. These cells are characterized as early-MDSCs, monocytic-MDSCs, and polymorphonuclear-MDSCs and can be studied on the basis of their immunophenotypic characteristics and their functional properties to suppress T-cell activation and proliferation. MDSCs have emerged as important contributors to tumor expansion and chronic inflammation progression by inducing immunosuppressive mechanisms, angiogenesis and drug resistance. Most experimental and clinical studies concerning MDSCs have been mainly focused on solid tumors. In recent years, however, the implication of MDSCs in the immune dysregulation associated with hematologic malignancies, immune-mediated cytopenias and allogeneic hemopoietic stem cell transplantation has been documented and the potential role of these cells as biomarkers and therapeutic targets has started to attract a particular interest in hematology. The elucidation of the molecular and signaling pathways associated with the generation, expansion and function of MDSCs in malignant and immune-mediated hematologic diseases and the clarification of mechanisms related to the circulation and the crosstalk of MDSCs with malignant cells and other components of the immune system are anticipated to lead to novel therapeutic strategies. This review summarizes all available evidence on the implication of MDSCs in hematologic diseases highlighting the challenges and perspectives arising from this novel field of research.

Myeloid-Derived Suppressor Cells in Hematologic Diseases: Promising Biomarkers and Treatment Targets

Myeloid-derived suppressor cells (MDSC) are a heterogeneous group of immature myeloid cells that exist at very low numbers in healthy subjects but can expand significantly in malignant, infectious, and chronic inflammatory diseases. These cells are characterized as early-MDSCs, monocytic-MDSCs, and polymorphonuclear-MDSCs and can be studied on the basis of their immunophenotypic characteristics and their functional properties to suppress T-cell activation and proliferation. MDSCs have emerged as important contributors to tumor expansion and chronic inflammation progression by inducing immunosuppressive mechanisms, angiogenesis and drug resistance. Most experimental and clinical studies concerning MDSCs have been mainly focused on solid tumors. In recent years, however, the implication of MDSCs in the immune dysregulation associated with hematologic malignancies, immune-mediated cytopenias and allogeneic hemopoietic stem cell transplantation has been documented and the potential role of these cells as biomarkers and therapeutic targets has started to attract a particular interest in hematology. The elucidation of the molecular and signaling pathways associated with the generation, expansion and function of MDSCs in malignant and immune-mediated hematologic diseases and the clarification of mechanisms related to the circulation and the crosstalk of MDSCs with malignant cells and other components of the immune system are anticipated to lead to novel therapeutic strategies. This review summarizes all available evidence on the implication of MDSCs in hematologic diseases highlighting the challenges and perspectives arising from this novel field of research.

STAT3 antisense oligonucleotide AZD9150 in a subset of patients with heavily pretreated lymphoma: results of a phase 1b trial

Background

The Janus kinase (JAK) and signal transduction and activation of transcription (STAT) signaling pathway is an attractive target in multiple cancers. Activation of the JAK-STAT pathway is important in both tumorigenesis and activation of immune responses. In diffuse large B-cell lymphoma (DLBCL), the transcription factor STAT3 has been associated with aggressive disease phenotype and worse overall survival. While multiple therapies inhibit upstream signaling, there has been limited success in selectively targeting STAT3 in patients. Antisense oligonucleotides (ASOs) represent a compelling therapeutic approach to target difficult to drug proteins such as STAT3 through of mRNA targeting. We report the evaluation of a next generation STAT3 ASO (AZD9150) in a non-Hodgkin’s lymphoma population, primarily consisting of patients with DLBCL.

Methods

Patients with relapsed or treatment refractory lymphoma were enrolled in this expansion cohort. AZD9150 was administered at 2 mg/kg and the 3 mg/kg (MTD determined by escalation cohort) dose levels with initial loading doses in the first week on days 1, 3, and 5 followed by weekly dosing. Patients were eligible to remain on therapy until unacceptable toxicity or progression. Blood was collected pre- and post-treatment for analysis of peripheral immune cells.

Results

Thirty patients were enrolled, 10 at 2 mg/kg and 20 at 3 mg/kg dose levels. Twenty-seven patients had DLBCL. AZD9150 was safe and well tolerated at both doses. Common drug-related adverse events included transaminitis, fatigue, and thrombocytopenia. The 3 mg/kg dose level is the recommended phase 2 dose. All responses were seen among DLBCL patients, including 2 complete responses with median duration of response 10.7 months and 2 partial responses. Peripheral blood cell analysis of three patients without a clinical response to therapy revealed a relative increase in proportion of macrophages, CD4+, and CD8+ T cells; this trend did not reach statistical significance.

Conclusions

AZD9150 was well tolerated and demonstrated efficacy in a subset of heavily pretreated patients with DLBCL. Studies in combination with checkpoint immunotherapies are ongoing.

Trial registration

Registered at ClinicalTrials.gov: NCT01563302. First submitted 2/13/2012.

Electronic supplementary material

The online version of this article (10.1186/s40425-018-0436-5) contains supplementary material, which is available to authorized users.

AAV-Vectored Fms-Related Tyrosine Kinase 3 Ligand Inhibits CD34+ Progenitor Cell Engraftment in Humanized Mice

Humanized mice have become useful animal models for HIV/AIDS. Since NOD.Cg-Prkdc scid Il2rgtm1Wjl/SzJ (NSG) mice allow the engraftment of primary human immune cells, we aim to determine the role of human Fms-related tyrosine kinase 3 ligand (hFlt3L), a major growth factor for dendritic cells (DCs), in regulating the differentiation of cord blood-derived CD34⁺ progenitor cells in this murine species. Soluble recombinant hFlt3L protein and AAV-vectored hFlt3L were administrated before or after human CD34⁺ progenitor cell transplantation, respectively. We then measured the peripheral levels of hFlt3L by ELISA. Meantime, reconstituted human immune cells were analyzed by flow cytometry over time. We found that without hFlt3L there were significantly increased types of human immune cells in NSG-huCD34 compared with NSG-huPBL mice but the frequency of human DCs remains low. Transient treatment with recombinant hFlt3L expanded human conventional CD1c⁺ and CD141⁺ DCs as well as plasmacytoid DCs in humanized NSG-huCD34 mice. Surprisingly, however, the prolonged in vivo expression of AAV-vectored hFlt3L resulted in significant suppression of total human CD34⁺ cell engraftment and differentiation. The suppression occurred within 2 weeks when AAV-vectored hFlt3L was administered either before or after the transplantation of CD34⁺ progenitor cells, which was likely associated with the induction of murine myeloid-derived immune suppressive cells and reactive oxygen species in NSG-huCD34 mice. Since chronic  HIV-1 patients displayed significantly high levels of hFlt3L expression, our findings may have implication to explore the role of prolonged hFlt3L in regulating  the differentiation of human CD34⁺ progenitor cells in both NSG-huCD34 mice and infected people. Graphical Abstract ᅟ.

Bendamustine with Total Body Irradiation Limits Murine Graft-versus-Host Disease in Part Through Effects on Myeloid-Derived Suppressor Cells

Graft-versus-host disease (GVHD) remains a significant challenge in allogeneic hematopoietic cell transplantation (HCT). An underinvestigated strategy to reduce GVHD is the modification of the preparative conditioning regimen. In the present study, we aimed to evaluate GVHD associated with bendamustine (BEN) conditioning in conjunction with total body irradiation (TBI) as an alternative to the standard myeloablative regimen of cyclophosphamide (CY) and TBI. We demonstrate that BEN-TBI conditioning, although facilitating complete donor chimerism, results in significantly less GVHD compared with CY-TBI. In BEN-TBI-conditioned mice, suppressive CD11b⁺Gr-1^high myeloid cells are increased in the blood, bone marrow, spleen, and intestines. When Gr-1^high cells are depleted before transplantation, the beneficial effects of BEN-TBI are partially lost. Alternatively, administration of granulocyte colony-stimulating factor, which promotes CD11b⁺Gr-1⁺ myeloid cell expansion, is associated with a trend toward increased survival in BEN-TBI-conditioned mice. These findings indicate a potential role of myeloid-derived suppressor cells in the mechanism by which BEN allows engraftment with reduced GVHD. BEN-TBI conditioning may present a safer alternative to CY-TBI conditioning for allogeneic HCT.

Adenovirus-mediated CD40L gene transfer increases Teffector/Tregulatory cell ratio and upregulates death receptors in metastatic melanoma patients

Background and aims

Malignant melanoma is an aggressive tumor sensitive for immunotherapy such as checkpoint blockade antibodies. Still, most patients with late stage disease do not respond, and the side effects can be severe. Stimulation of the CD40 pathway to initiate anti-tumor immunity is a promising alternative. Herein, we demonstrate immune profiling data from melanoma patients treated with an adenovirus-based CD40 ligand gene therapy (AdCD40L).

Methods

Peripheral blood mononuclear cells and plasma were collected from malignant melanoma patients (n = 15) enrolled in a phase I/IIa study investigating intratumoral delivery of AdCD40L with or without low dose cyclophosphamide. Cells were analyzed by flow cytometry while plasma samples were analyzed by a multi-array proteomics.

Results

All patients had an increased Teffector/Tregulatory cell ratio post therapy. Simultaneously, the death receptors TNFR1 and TRAIL-R2 were significantly up-regulated post treatment. Stem cell factor (SCF), E-selectin, and CD6 correlated to enhanced overall survival while a high level of granulocytic myeloid-derived suppressor cells (gMDSCs), IL8, IL10, TGFb1, CCL4, PlGF and Fl3t ligand was highest in patients with short survival.

Conclusions

AdCD40L intratumoral injection induced desirable systemic immune effects that correlated to prolonged survival. Further studies using CD40 stimulation in malignant melanoma are warranted.

Trial registration The 002:CD40L trial “Phase I/IIa AdCD40L Immunogene Therapy for Malignant Melanoma and Other Solid Tumors” (clinicalTrials.gov identifier: NCT01455259) was registered at September 2011

In Vivo Mobilization and Functional Characterization of Nonhuman Primate Monocytic Myeloid-Derived Suppressor Cells

Increasing evidence from small animal models shows that myeloid-derived suppressor cells (MDSCs) can play a crucial role in inhibiting allograft rejection and promoting transplant tolerance. We identified CD3(-)CD20(-)HLA-DR(-)CD14(+)CD33(+)CD11b(+) cells in peripheral blood of healthy rhesus macaques. These putative monocytic MDSCs constituted 2.1% ± 1.7% of lin(-)HLA-DR(-) peripheral blood mononuclear cells. Administration of granulocyte-macrophage colony-stimulating factor (CSF) and granulocyte CSF increased their incidence to 5.3% ± 3.4%. The total number of MDSCs that could be flow sorted from a single whole rhesus leukapheresis product was 38 ± 13 × 10(6) (n = 10 monkeys). Freshly isolated or cryopreserved MDSCs from mobilized monkeys incorporated in cultures of anti-CD3- and anti-CD28-stimulated autologous T cells markedly suppressed CD4(+) and CD8(+) T cell proliferation and cytokine secretion (interferon γ, IL-17A). Moreover, these MDSCs enhanced CD4(+)CD25(hi)Foxp3(+) regulatory T cell (Treg) expansion while inhibiting proliferation of activated memory T cells and increasing Treg relative to effector and terminally differentiated memory T cells. Inhibition of arginase-1, but not inducible nitric oxide synthase activity, partially reversed the inhibitory effect of the MDSCs on CD8(+) T cell proliferation. Consequently, functional MDSCs can be isolated from nonhuman primates for prospective use as therapeutic cellular vaccines in transplantation.

Phenotype, development, and biological function of myeloid-derived suppressor cells

CD11b⁺Gr-1⁺ myeloid-derived suppressor cells (MDSCs) are an important population of innate regulatory cells mainly comprising monocytic MDSCs (M-MDSCs) with a phenotype of CD11b⁺Ly6G^-Ly6C^high and granulocytic MDSCs (G-MDSCs) with a phenotype of CD11b⁺Ly6G⁺Ly6C^low in mice. They play crucial roles in the pathogenesis of cancers, chronic infections, autoimmune diseases, and transplantation. Various extracellular factors such as lipopolysaccharide (LPS), macrophage colony-stimulating factor (M-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), stem cell factor (SCF), interleukin (IL)-6, interferon gamma (IFNγ), IL-1β, vascular endothelial growth factor (VEGF), Hsp72, IL-13, C5a, and prostaglandin E2 (PGE2) can induce MDSC differentiation, whereas IL-4 and all-trans-retinoic acid can inhibit this process. For the intracellular signals, signal transducer and activator of transcription (STAT) family members, C/EBPβ and cyclooxigenase-2 (COX-2) promote MDSC function, whereas interferon regulatory factor-8 (IRF-8) and Smad3 downregulate MDSC activity. The immunosuppressive function of MDSCs is mediated through various effector molecules, primarily cellular metabolism-related molecules such as nitric oxide (NO), arginase, reactive oxygen species (ROS), transforming growth factor β (TGFβ), IL-10, indoleamine 2,3-dioxygenase (IDO), heme oxygenase-1 (HO-1), carbon monoxide (CO), and PGE2. In this article, we will summarize the molecules involved in the induction and function of MDSCs as well as the regulatory pathways of MDSCs.

New Strategies in Sarcoma: Linking Genomic and Immunotherapy Approaches to Molecular Subtype

There are more than 100 sarcoma subtypes, each uncommon and diagnostically challenging. Conventional chemotherapy has little benefit for most soft-tissue sarcomas; new treatment strategies are needed. Multiple recent genomic studies have provided detailed insights into sarcoma biology, including more accurate classification by molecular subtype, identification of recurrent mutations in oncogenic pathways, and evidence of epigenetic dysregulation. Advances in immunotherapy (adoptive immune cell transfer, tumor vaccine strategies, and immune checkpoint inhibition) have also provided a better understanding of how immuno-oncology might best be applied to sarcoma treatment, including connections to oncogenic pathways that may support combination strategies with conventional and targeted therapies. In this article, we review the latest sarcoma genomic studies and immuno-oncology developments and discuss how the findings suggest potential strategies to improve diagnosis and treatment across multiple sarcoma subtypes.

Myeloid-derived suppressor cells: their role in the pathophysiology of hematologic malignancies and potential as therapeutic targets

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells at various stages of differentiation/maturation that have a role in cancer induction and progression. They function as vasculogenic and immunosuppressive cells, utilizing multiple mechanisms to block both innate and adaptive anti-tumor immunity. Recently, their mechanism of action and clinical importance have been defined, and the cross-talk between myeloid cells and cancer cells has been shown to contribute to tumor induction, progression, metastasis and tolerance. In this review, we focus on the role of MDSCs in hematologic malignancies and the therapeutic approaches targeting MDSCs that are currently in clinical studies.

Concurrence of B-lymphoblastic leukemia and myeloproliferative neoplasm with copy neutral loss of heterozygosity at chromosome 1p harboring a MPL W515S mutation

B-lymphoblastic leukemia (B-ALL) is a neoplasm of precursors committed to B-cell lineage, whereas myeloproliferative neoplasm (MPN) is a clonal proliferation derived from myeloid stem cells. Concurrent B-ALL with MPN is uncommon except in the presence of abnormalities of the PDGFRA, PDGFRB, or FGFR1 genes or the BCR-ABL1 fusion gene. Herein, we describe a rare concurrence, B-ALL with MPN without the aforementioned genetic aberrations, in a 64-year-old male patient. The patient was initially diagnosed with B-ALL with normal karyotype and responded well to aggressive chemotherapy but had sustained leukocytosis and splenomegaly. The posttreatment restaging bone marrow was free of B-ALL but remained hypercellular with myeloid predominance. Using a single nucleotide polymorphism microarray study, we identified a copy neutral loss of heterozygosity at the terminus of 1p in the bone marrow samples taken at diagnosis and again at remission, 49% and 100%, respectively. Several additional genetic abnormalities were present in the initial marrow sample but not in the remission marrow samples. Retrospective molecular studies detected a MPL W515S homozygous mutation in both the initial and remission marrows for B-ALL, at 30-40% and 80% dosage effect, respectively. In summary, we present a case of concurrent B-ALL and MPN and demonstrate a stepwise cytogenetic and molecular approach to the final diagnosis.