Immature Myeloid-derived Suppressor Cells Research Articles

Immunophenotypic variations in syphilis: insights from Mendelian randomization analysis.

Infection with Treponema pallidum instigates complex immune responses. Prior research has suggested that persistent Treponema pallidum infection can manipulate host immune responses and circumvent host defenses. However, the precise role of immune cells in Treponema pallidum infection across different stages remains a contentious issue. Utilizing summary data from genome-wide association studies, we employed a two-sample Mendelian randomization method to investigate the association between 731 immunophenotypes and syphilis. Syphilis was categorized into early and late stages in this study to establish a more robust correlation and minimize bias in database sources. Our findings revealed that 33, 36, and 27 immunophenotypes of peripheral blood were associated with syphilis (regardless of disease stage), early syphilis and late syphilis, respectively. Subsequent analysis demonstrated significant variations between early and late syphilis in terms of immunophenotypes. Specifically, early syphilis showcased activated, secreting, and resting regulatory T cells, whereas late syphilis was characterized by resting Treg cells. More B cells subtypes emerged in late syphilis. Monocytes in early syphilis exhibited an intermediate and non-classical phenotype, transitioning to classical in late syphilis. Early syphilis featured naive T cells, effector memory T cells, and terminally differentiated T cells, while late syphilis predominantly presented terminally differentiated T cells. Immature myeloid-derived suppressor cells were evident in early syphilis, whereas the dendritic cell immunophenotype was exclusive to late syphilis. Multiple immunophenotypes demonstrated associations with syphilis, showcasing substantial disparities between the early and late stages of the disease. These findings hold promise for informing immunologically oriented treatment strategies, paving the way for more effective and efficient syphilis interventions.

Alternative Chemotherapies: Angiotensin-Converting Enzyme Inhibitors Reduce Myeloid-Derived Suppressor Cells to Benefit Older Patients with Colorectal Cancer.

Older individuals are more likely to develop solid cancers, but at the same time are more sensitive to the side effects of chemotherapy. In addition, older adults are more likely to present with chronic diseases (comorbidities) and immunosenescence that may decrease immunosurveillance against cancer. Clinical outcomes for the older patient with cancer are different from the younger patient and require different research and treatment approaches. Thus, alternative therapeutic approaches tailored specifically to the older patients are required. Colorectal cancer (CRC) has a high incidence in older individuals and is the third leading cause of cancer death globally. Anti-hypertensives are used by a large proportion of older patients and some studies have pointed to a positive impact of angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB) on CRC outcomes. As we have previously shown in a mouse model, lung metastases express ACE and contain many infiltrating myeloid-derived suppressor cells (MDSC); particularly high levels of MDSC are also present in the blood of older patients with CRC and other cancers, and are associated with disease severity. In this Commentary, we hypothesize that one mechanism responsible for the positive impact of ACEi or ARB on the outcome of CRC is the modulation of myeloid cells contributing to their maturation to non-suppressive neutrophils/monocytes and diverting them away from retaining an immature MDSC phenotype.

Alpha-Fetoprotein: A Revolutionary Anti-Cancer Drug

Alpha-fetoprotein is an oncofetal protein the embryo produces during fetal development. The protein serves two critical functions simultaneously: it delivers nutrients to growing embryo cells and immature myeloid-derived suppressor cells, so the mother’s immune system doesn’t attack the embryo. The protein is present in minuscule amounts in adults and elevated alpha-fetoprotein levels serve as pregnancy or tumor markers. Exogenous alpha-fetoprotein has a new application as an immunotherapy drug. It can deliver drugs in a natural shuttle manner to myeloid-derived suppressor cells and stimulate them to calm the hyperactive immune response during many physiological and pathological conditions. On the other hand, alpha-fetoprotein loaded with toxins kills myeloid-derived suppressor cells and unleashes natural killer cells and cytotoxic lymphocytes to erase cancer. Most cancers have cells that specifically bind alpha-fetoprotein, and this protein targets chemotherapy to them also. So, alpha-fetoprotein with toxins combines both potent cancer immunotherapy and targeted chemotherapy activities. Alpha-fetoprotein can be chemically conjugated with or bind toxins non-covalently. Both preparations have demonstrated superior efficacy and safety compared to chemotherapy alone. Alpha-fetoprotein-toxin immuno/chemotherapy is not personalized. There is no need to preselect patients for cancer treatments as they have elevated myeloid-derived suppressor cell levels. The anti-cancer efficacy of porcine alpha-fetoprotein non-covalent complexes with selected toxins administered orally is a remarkable discovery that needs research. Cancer treatment and prevention are different issues, and they could need different approaches. Alpha-fetoprotein administration with drugs or toxins could be as effective in early cancer and metastasis prevention as mifepristone pills in pregnancy prevention.

The Cross-Talk between Myeloid and Mesenchymal Stem Cells of Human Bone Marrow Represents a Biomarker of Aging That Regulates Immune Response and Bone Reabsorption

One of the mechanisms that characterizes the aging process of different organs is the accumulation of fat. Different authors have demonstrated that adipose tissue replaces the loss of other cell types, deriving from mesenchymal cells. During aging, there is substitution or trans-differentiation of mesenchymal cells with other cells having the same embryological origin. Newly formed adipocytes were also observed in the trabecular matrix of elderly people’s bones, associated with myeloid cells. In this study, we have investigated the relationship between immature myeloid-derived suppressor cells (I-MDSCs) and mesenchymal stem cells (MSCs) in bone marrow (BM) samples harvested from 57 patients subjected to different orthopedic surgeries. Patients aged from 18 to 92 years were considered in order to compare the cellular composition of bone marrow of young and elderly people, considered a biomarker of immunity, inflammation, and bone preservation. The I-MDSC percentage was stable during aging, but in elderly people, it was possible to observe a strong basal immunosuppression of autologous and heterologous T cells’ proliferation. We hypothesized that this pattern observed in elders depends on the progressive accumulation in the BM of activating stimuli, including cell–cell contact, or the production of different cytokines and proteins that induce the differentiation of bone marrow mesenchymal stem cells in adipocytes. The collected data provided underline the importance of specific biomarkers of aging that promote a reduction in immune response and incremented inflammatory pathways, leading to bone reabsorption in elderly people.

Dysregulated Immunometabolism Is Associated with the Generation of Myeloid-Derived Suppressor Cells in Staphylococcus aureus Chronic Infection

Myeloid-derived suppressor cells (MDSCs) are a compendium of immature myeloid cells that exhibit potent T-cell suppressive capacity and expand during pathological conditions such as cancer and chronic infections. Although well-characterized in cancer, the physiology of MDSCs in the infection setting remains enigmatic. Here, we integrated single-cell RNA sequencing (scRNA-seq) and functional metabolic profiling to gain deeper insights into the factors governing the generation and maintenance of MDSCs in chronic Staphylococcus aureus infection. We found that MDSCs originate not only in the bone marrow but also at extramedullary sites in S. aureus-infected mice. scRNA-seq showed that infection-driven MDSCs encompass a spectrum of myeloid precursors in different stages of differentiation, ranging from promyelocytes to mature neutrophils. Furthermore, the scRNA-seq analysis has also uncovered valuable phenotypic markers to distinguish mature myeloid cells from immature MDSCs. Metabolic profiling indicates that MDSCs exhibit high glycolytic activity and high glucose consumption rates, which are required for undergoing terminal maturation. However, rapid glucose consumption by MDSCs added to infection-induced perturbations in the glucose supplies in infected mice hinders the terminal maturation of MDSCs and promotes their accumulation in an immature stage. In a proof-of-concept in vivo experiment, we demonstrate the beneficial effect of increasing glucose availability in promoting MDSC terminal differentiation in infected mice. Our results provide valuable information of how metabolic alterations induced by infection influence reprogramming and differentiation of MDSCs.

Higher neutrophil-to-lymphocyte ratio after the first cycle of the first-line chemotherapy is associated with poor cancer specific survival of upper urinary tract carcinoma patients.

BackgroundInflammatory cytokines and immature myeloid derived suppressor cells (MDSCs), which increase during cancer progression, could lead to a neutrophil increase and lymphocyte reduction. Thus, the neutrophil-lymphocyte ratio (NLR) was used to predict survival of patients suffering from urological cancers including upper urinary tract carcinoma. We further determined whether the NLR during the first cycle of first-line chemotherapy could predict cancer specific survival.MethodsWe recruited patients with locally advanced or metastatic upper urinary tract urothelial carcinoma (UTUC) who received chemotherapy between January 2014 and July 2019. We investigated the impact of various clinical variables, including age, sex, performance status, and estimated creatinine clearance (CCr), and NLR before and after the first cycle of the first-line chemotherapy on prognosis.ResultsA total of 41 patients were included in our study. Cancer specific survival of the patients with lower NLR was significantly better than that of the patients with higher NLR measured after the first cycle of the first-line chemotherapy (log-rank test P=0.005, median 29.2 vs. 11.9 months, respectively). Cox proportional regression analysis showed that higher NLR after the first cycle of the first-line chemotherapy was a significant predictor of cancer specific survival.ConclusionsThe NLR after the first cycle of the first-line chemotherapy could be an indication for patients with locally advanced or metastatic UTUC to maintain their first-line chemotherapy treatment.

Immunosuppressive effects and mechanisms of three myeloid-derived suppressor cells subsets including monocytic-myeloid-derived suppressor cells, granulocytic-myeloid-derived suppressor cells, and immature-myeloid-derived suppressor cells.

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immune cells of myeloid lineage. Recent reports have suggested that human MDSC are divided into three subsets: monocytic MDSC (M-MDSC), granulocytic MDSC (G-MDSC), and immature MDSC (I-MDSC). However, the characteristics of each human MDSC subset still remain unclear. To evaluate the immunosuppressive effects and mechanisms, we first performed a T-cell suppression assay using cells obtained from healthy donor peripheral blood samples. The levels of immune inhibitory molecules in the culture supernatant of each MDSC subset were measured to reveal the T-cell suppressive mechanisms. Then, we compared these results with the results from cells obtained from cancer patient blood samples. Finally, we investigated the difference in the frequency of each MDSC subset between the healthy donors and the cancer patients. Although M-MDSC and G-MDSC suppressed T-cell activation, I-MDSC had no T-cell suppressive effect. We found that the culture supernatant of M-MDSC and G-MDSC contained high levels of interleukin-1 receptor antagonist (IL-1RA) and arginase, respectively, in both healthy donors and cancer patients. No inhibitory molecules were detected in the culture supernatant of I-MDSC. The population of functional MDSC (M-MDSC and G-MDSC) in the total MDSC was significantly increased in cancer patients compared with that in healthy donors. Although M-MDSC and G-MDSC, which released IL-1RA and arginase, respectively, suppressed T-cell activation, I-MDSC did not have an immunosuppressive effect. The population of functional MDSC was increased in cancer patients compared with that in healthy donors.

RNA-Seq Analysis of Colorectal Tumor-Infiltrating Myeloid-Derived Suppressor Cell Subsets Revealed Gene Signatures of Poor Prognosis.

Elevated levels of myeloid-derived suppressor cells (MDSCs), including polymorphonuclear MDSCs (PMN-MDSCs) and immature MDSCs (I-MDSCs), are usually associated with disease progression in cancer patients, including colorectal cancer (CRC). However, biological mechanisms and molecular pathways regulated by MDSC subpopulations in the CRC tumor microenvironment (TME) have not been fully investigated. In this study, we performed transcriptomic analysis of tumor-infiltrating I-MDSCs and PMN-MDSCs isolated from tumor tissues of six CRC patients, compared to antigen-presenting cells (APCs). We also compared the transcriptomic profiles of tumor-infiltrating PMN-MDSCs to I-MDSCs. Our results showed different molecular pathways regulated by each MDSC subset, potentially reflecting their phenotypical/molecular/functional characteristics in the CRC TME. Moreover, we identified gene signatures in PMN-MDSC and I-MDSC of poor overall survival (OS) and disease-free survival (DFS) using the Cancer Genome Atlas (TCGA) dataset from patients with colon adenocarcinoma (COAD). However, functional studies are required to validate these findings.

Transcriptomic Analyses of Myeloid-Derived Suppressor Cell Subsets in the Circulation of Colorectal Cancer Patients

Myeloid-derived suppressor cells (MDSCs) promote tumor immune evasion and favor tumorigenesis by activating various tumor-promoting downstream signals. MDSC expansion is evident in the circulation and tumor microenvironment of many solid tumors including colorectal cancer (CRC). We have recently reported the transcriptomic profiles of tumor-infiltrating MDSCs in CRC patients and uncovered pathways, which could potentially assist tumor progression. In this study, we sorted different subsets of circulating MDSCs in CRC patients and investigated their transcriptomic profiles in order to disclose pathways, which could potentially contribute to disease progression. The sorted subsets included polymorphonuclear/granulocytic MDSCs (PMN-MDSCs), immature MDSCs (I-MDSCs), and monocytic MDSCs (M-MDSCs). Our functional annotation analyses revealed that multiple pathways including DNA damage-, chemotaxis-, apoptosis-, mitogen-activated protein kinase-, transforming growth factor β-, and myeloid differentiation–related transcripts were higher in PMN-MDSCs, compared with monocytic antigen-presenting cells (APCs) or I-MDSCs. Furthermore, genes related to Janus kinase (JAK)–signal transducer and activator of transcription (STAT) were also elevated in PMN-MDSCs. These data suggest that upregulation of JAK-STAT pathway could trigger multiple downstream targets in PMN-MDSCs, which favor tumor progression. Additionally, we found that pathways including phosphatidyl inositol 3-kinase (PI3K), interleukin 6, and TGF-β in M-MDSCs and cell cycle–related pathways in I-MDSCs were upregulated, compared with monocytic APCs. Moreover, acetylation-related genes were upregulated in both PMN-MDSCs and M-MDSCs. This latter finding implicates that epigenetic modifications could also play a role in the regulation of multiple tumor-promoting genes in PMN-MDSCs and M-MDSCs. Taken together, this study reveals various signaling pathways, which regulate the function of MDSC subsets in the circulation of CRC patients. However, functional studies are warranted to support these findings.

Abstract LB-213: Pro-angiogenic and myeloid cell gene expression markers in prognostication of advanced stage colorectal cancer patients

Abstract Colorectal cancer (CRC) is third deadliest cancer in United States, only behind lung and prostate cancer. Myeloid cell involvement in tumor development is dichotomous. There is evidence that they can be immunostimulatory and tumor suppressive as well as immunosuppressive and tumorigenic. These cells seem to play a crucial role in tumor angiogenesis & vasculogenesis. The functional fluidity is driven by factors present in the tumor microenvironment (TME), which alter myeloid cell gene expression and thus phenotype & function. Broadly, the pathologic myeloid cells present within the tumor can be broken down into two classes: immature myeloid-derived suppressor cells (MDSCs) & mature tumor-associated myeloid cells (TAMCs). This project investigates the angiogenic/vasculogenic gene signatures of MDSCs & TAMCs. Seven genes that were either markers of myeloid cells or expressed by pro-angiogenic MDSCs & TAMCs: CD14, CD15, VEGF, TNF-a, TGF-b, cathepsin B, & MMP-14 were analyzed in tumor samples using Syber Green qPCR. The aim of this study is to determine possible associations of gene expression with endpoints such as tumor stage, tumor grade & patient survival, so as to determine their prognostic value in predicting outcome in CRC patients. Under the IRB approved protocol, a total of 750 colon cancer patients at Medical College of Georgia with 5 years follow-up were initially selected. The patients were stratified on the basis of overall survival in two groups, with higher (> 5 years) and lower survival (<1 year) along with AJCC staging (I to IV), grade, gender and age. A total of 88 patients fitted in our inclusion criteria on the basis of survival duration after diagnosis. H&E slides were reviwed and macrodissected for tumor only regions. Total RNA was isolated and quantified through Nanodrop method. The statistical analysis of data was performed using student t-test. Compared to stage 1 patients, CD15 expression was found to be significantly upregulated in stage 4 (p=0.04). The same observation was made for stage 2 (p=0.06) and 3 patients (0.54), though it did not achieve statistical significance (p=0.076). Also, TGF-b expression was found to be significantly upregulated in stage 2 (p=0.05) & stage 4 (p=0.05). The same observation was made for stage 3 patients, though it did not achieve statistical significance (p=0.076). Our findings suggest that both CD15 (marker of mature myeloid cell populations), and TGF-β (associated with both immunosuppresion and angiogenesis) are associated with advanced stage colorectal cancer. CD15 and TGF-β seems to be potential biomarkers of prognostic significance. Inaddition, TGF-B might be targeted in advanced colorectal cancer for personalized therapy. Citation Format: Ben Johnson, Nikhil Sahajpal, Pankaj Ahaluwalia, Ashis Mondal, Allan Njau, Meenaskhi Ahaluwalia, Ravindra Kolhe. Pro-angiogenic and myeloid cell gene expression markers in prognostication of advanced stage colorectal cancer patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-213.

Abstract A01: Treatment with Imprime PGG, a soluble yeast β-glucan PAMP, induces trafficking of activated Ly6Ghigh cells to secondary lymphoid organs and tumor and facilitates immune activation within the tumor microenvironment

Abstract Imprime PGG (Imprime), an intravenously administered, soluble, yeast β-1,3/1,6 glucan, is currently in clinical development with tumor-targeting, antiangiogenic and checkpoint inhibitor antibodies. The fundamental mechanistic rationale for these different therapeutic combinations is that Imprime, a pathogen-associated molecular pattern (PAMP), primes innate immune effector functions to drive a coordinated anticancer immune response. Previous preclinical mechanistic work has shown that Imprime activates the functionalities of monocytes, macrophages, and dendritic cells (cells that principally influence the TME), eliciting a tumor microenvironment (TME) that activates T cell-dependent antitumor immunity. Studies have shown that mature neutrophils and immature myeloid-derived suppressor cells (PMN-MDSC) accumulate, like other myeloid cells, in the tumor and play a role in establishing the immunosuppressive TME and impair T-cell immunity. Herein, we provide evidence that Imprime treatment reorients neutrophil function, enlisting these cells in anticancer immunity. To date, exploration of the effect of Imprime on neutrophils has evaluated direct neutrophil-mediated tumor killing. In this study, we further explored the impact of Imprime treatment on mature neutrophils and immature PMN-MDSC (i.e., the Ly6Ghigh population) in both tumor-free and tumor-bearing mice. In tumor-free C57BL/6 mice, Imprime mobilized Ly6Ghigh cells into the blood, spleen, and skin draining lymph nodes (sdLNs). The increase of these cells in the sdLN coincided with increased levels of CCL2, CCL3, CCL4, CXCL1 and CXCL10, chemokines important for the mobilization of myeloid cells. In the H1299 lung cancer xenograft model, the addition of Imprime to bevacizumab enhanced CD86 expression on Ly6Ghigh cells in both spleen and tumor tissues when compared to bevacizumab alone, indicating that these cells could play a role in T-cell activation. We therefore assessed the effect of Imprime in MC-38, syngeneic tumor model, shown to be sensitive to Imprime in combination with immune checkpoint inhibitor antiboides (i.e., anti-PD1 and PD-L1). Consistent with our earlier findings, Imprime and Imprime + anti-PD-1 treatments significantly increased the percentage of Ly6Ghigh cells in the spleen and the tumor compared to the vehicle alone. The Ly6Ghigh cells in both the spleen and TME showed increased expression of CD86, MHCII and PD-L1. The enriched PMN-MDSC (~60-70% Ly6Ghigh) from the spleens of Imprime-treated mice were significantly less suppressive to CD3/CD28-mediated proliferation of CD3+ splenocytes. Collectively, these data show that neutrophils have a role in Imprime-mediated remodeling of the immunosuppressive TME, driving a more conducive environment to T-cell immunity. The effects of Imprime on peripheral and tumor-associated neutrophils in cancer patients are currently being explored in phase 2 clinical trials employing the combination of Imprime and anti-PD1 antibody, pembrolizumab. Citation Format: Adria L. Bykowski Jonas, Anissa S.H. Chan, Nadine C. Ottoson, Xiaohong Qui, Keith Gordon, Mark Uhlik, Jeremy Graff, Nandita Bose. Treatment with Imprime PGG, a soluble yeast β-glucan PAMP, induces trafficking of activated Ly6Ghigh cells to secondary lymphoid organs and tumor and facilitates immune activation within the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A01.

Abstract 4049: Cellular phenotypes of spleen cells in cancer patients targeted for adoptive cellular therapy

Abstract The spleen is a rich resource of large numbers of lymphocytes, with potential for use in adoptive cellular therapy (ACT). This is of particular relevance to patients with a distal pancreatic ductal adenocarcinoma (PDAC) who frequently undergo a pancreatectomy that required a splenectomy to clear the nodal basin. In this study we compared the phenotypes of eight paired sets of peripheral blood (PB) and spleen cell populations to assess the frequency of myeloid derived suppressor cells (MDSC) and lymphocyte subpopulations. Because a positive clinical response to ACT requires a low frequency of T-regs and MDSC’s, both systemically and in the tumor microenvironment these cells were one of the foci for our studies. A high frequency of these cells negatively correlate with survival and positively with tumor burden. Indeed, in this study we observed a significant decrease in the frequency of granulocytic, monocytic and immature MDSC’s in the spleen vs PB (4.8±1.6 vs. 54.4±6.1; 0.2±0.1 vs. 0.9±0.4; and 0.6±0.1 vs. 2.3±0.8 percent respectively) but not T-regulatory (T-reg) cells (0.8+0.5 vs. 0.1+0.04 percent) supporting the potential superiority of spleen cells relative to PB as a cellular source for ACT. In addition to a significantly higher number of spleen cells as compared to the PB for expansion/infusion, spleens have a higher frequency of T-cells as compared to the PB including CD3+ (35+5 vs. 16+4%), CD4+ (19+2 vs. 10+2%) and CD8+ (10+1 vs. 5+2%) T-cells. The frequency of transitional memory (Ttm) T-cells, which have a high proliferative potential were also significantly increased in the spleen vs. PB (37.5±6 vs. 26±3.0%) as was the frequency of PD1+CD8+ T-cells (8+2 vs 1+0.5%), which have been shown to have tumor specific cytotoxicity in cancer patients. In summary the increased frequency of PD-1+CD8+ cells, a Ttm memory phenotype and low levels of an exhaustion phenotype (TIM3 and Lag3 expression) in spleen cells vs the PB is supportive of the potential utility of these cells for expansion and therapeutic utility for these cells. Citation Format: Kathryn Cole, Quan Ly, Jesse L. Cox, Michael A. Hollingsworth, James C. Padussis, Jason M. Foster, Luciano M. Vargas, James E. Talmadge. Cellular phenotypes of spleen cells in cancer patients targeted for adoptive cellular therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4049.

Abstract 1233: Myeloperoxidase (MPO) activity in myeloid-derived suppressor cells (MDSCs): effects on anticancer drug activity

Abstract In cancer, suppression of host immunity is related, in part, to immature myeloid-derived suppressor cells (MDSCs) expanded in response to various tumor- or stroma-derived factors. Here, the expression and activity of myeloperoxidase (MPO) was examined in both granulocytic (PMN) and monocytic (M) MDSC subsets recovered from the spleens of 4T1 tumor-bearing mice, as well as interferon regulatory factor-8 (IRF8) knockout mice (IRF8-/-) which develop high levels of MDSCs due to IRF8-deficiency. Phenotypically identical cells from non-tumor-bearing mice served as controls. In addition, the role of MPO in PMN-MDSCs as a determinant of DNA damage induced by the anticancer agents etoposide (VP-16), camptothecin (CPT) and parthenolide (PTL), was evaluated for potential immunomodulatory effects. MPO protein content was ~4-fold greater in PMN-MDSCs from tumor-bearing compared to non-tumor-bearing mice, while MPO specific activity was equivalent in these two populations. MPO protein content in PMN-MDSCs from IRF8-/- mice was at least comparable to levels found in tumor-bearing hosts. In both IRF8-/- and tumor-bearing mice, PMN-MDSCs contained 5-10-fold greater MPO protein and overall enzyme activity compared to isolated M-MDSCs. VP-16 (5 µM)- and PTL (100 µM)-induced DNA strand breaks were 4-fold greater in PMN- compared to M-MDSCs from tumor-bearing mice. In addition, the heme-synthesis inhibitor, succinylacetone (SA) reduced MPO activity 2-3-fold in PMN-MDSCs from tumor-bearing mice with a corresponding decrease in drug-induced DNA damage for both VP-16 and PTL with no effect on CPT-induced DNA damage. The antioxidant dehydroascorbate decreased VP-16-induced DNA damage in PMN-MDSCs containing MPO activity, but not in those cells pre-incubated with SA to deplete MPO. These results indicate that MPO-dependent activation of VP-16 and PTL enhance DNA damage. Antioxidant protection against VP-16-induced DNA damage is consistent with MPO-mediated oxidative activation of VP-16 to a redox-cycling phenoxyl radical (Mol. Pharmacol. 79: 479-487, 2011). Overall, these results suggest that: 1) PTL may be useful to eliminate PMN-MDSCs; 2) MPO activation of VP-16 in PMN-MDSCs may be deleterious via oxidative DNA damage resulting in mixed-lineage leukemia (MLL) gene rearrangements known to be causal for therapy-related myeloid leukemias. Support: CA172105; CA090787; CA140622 Citation Format: Jack C. Yalowich, Ragu Kanagasabai, Colleen S. Netherby, Michelle N. Messmer, Scott I. Abrams. Myeloperoxidase (MPO) activity in myeloid-derived suppressor cells (MDSCs): effects on anticancer drug activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1233.

Nicotinamide Phosphoribosyltransferase Acts as a Metabolic Gate for Mobilization of Myeloid-Derived Suppressor Cells.

Cancer induces alteration of hematopoiesis to fuel disease progression. We report that in tumor-bearing mice the macrophage colony-stimulating factor elevates the myeloid cell levels of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway, which acts as negative regulator of the CXCR4 retention axis of hematopoietic cells in the bone marrow. NAMPT inhibits CXCR4 through a NAD/Sirtuin 1-mediated inactivation of HIF1α-driven CXCR4 gene transcription, leading to mobilization of immature myeloid-derived suppressor cells (MDSC) and enhancing their production of suppressive nitric oxide. Pharmacologic inhibition or myeloid-specific ablation of NAMPT prevented MDSC mobilization, reactivated specific antitumor immunity, and enhanced the antitumor activity of immune checkpoint inhibitors. Our findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in patients with cancer. SIGNIFICANCE: These findings identify NAMPT as a metabolic gate of MDSC precursor function, providing new opportunities to reverse tumor immunosuppression and to restore clinical efficacy of immunotherapy in cancer patients.

Anti-CD123 Targeted Therapy with Talacotuzumab in Advanced MDS and AML after Failing Hypomethylating Agents - Final Results of the Samba Trial

IntroductionRecently, progress has been made in the treatment of patients with higher risk myelodysplastic syndromes (HR MDS) and acute myeloid leukemia (AML). Nevertheless, patients failing hypomethylating agents (HMA) have a dismal prognosis and very limited treatment options. Targeting CD123 on leukemic stem cells (LSC) is one promising approach in MDS and AML. Talacotuzumab (TAL, JNJ-56022473) is an IgG1 monoclonal antibody targeting CD123 preferentially via antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer cells (NKs).AimThe SAMBA trial, a phase II study of the German and French MDS study groups within the EMSCO network assessed the overall hematological response rate after 3 months of single agent TAL treatment in AML or HR MDS patients failing hypomethylating agents (HMAs).MethodsTAL was given IV at a dose of 9 mg/kg once every two weeks for a total of 6 infusions, responders received up to 20 additional infusions. After the first 3 months, overall hematological response rate (either CR, PR, marrow-CR, HI, SD) was evaluated by bone marrow biopsy. The study was accompanied by an immune monitoring via flow cytometric analysis to investigate the distribution of T- and NK cells in peripheral blood (PB) and bone marrow (BM) at the time of screening and during therapy in comparison with healthy, age-matched controls.Results24 patients (19 AML and 5 HR MDS) with a median age of 77 (range 71-90) years, who either failed to achieve complete- (CR), partial response (PR), hematological improvement (HI) or relapsed after HMA therapy were included in the study. After TAL administration, 14 patients could be assessed for response after 4 infusions and 10 patients after 6 infusions. The overall response rate (ORR) was 20.8% including 1 complete remission (CRi), 1 patient with hematologic improvement (HI-E) and additionally 3 patients with disease stabilization. The median duration of response in these patients was 3 months (range 3-14 months). Two patients are still on treatment, one patient despite losing objective response (14 months) and one patient with disease stabilization (13 months). The median overall survival for the entire cohort of patients was 3.2 months (range 0.4-11.2 months). In 10 patients (41.6%), therapy with TAL resulted in grade 3/4 infusion related side effects (pneumonia, n=1; infusion-related reaction, n=8; septic shock, n=1).Before treatment initiation, patients had lower levels of CD56dim NK-cells in PB (82% vs. 89% of NK-cells; p=0.069) expressing significantly more inhibiting NK-cell receptors like KIR2DL2 (8.8% vs. 3.2% of NK-cells; p<0.001) and less activating NK-cells receptors like NKG2D (95% vs. 99% of NK-cells; p<0.01) compared to healthy controls. Moreover, expression of PD-1 on lymphocytes and monocytes as well as their matching ligands PD-L1 and PD-L2 on blasts and monocytes in PB was significantly higher in patients compared to healthy controls (p<0.01), another evidence for an exhausted T-cell immune status in our patients prior to treatment initiation.We could not detect any difference in NK-cell levels in responding patients compared to non-responders. Interestingly, pre-treatment expression (MFI and percentage) of CD123 on immature myeloid derived suppressor cells (iMDSC) was higher in responders than in non-responders (p<0.01). Anti-CD123 targeted therapy with TAL resulted in a decreased CD123+ MFI (4239 vs. 2910; p<0.01) on iMDSCs as well as lower levels of iMDSCs in PB and BM (p<0.05).Responding patients displayed a 10-fold reduction of CD123 MFI after 3 months of treatment (2565 vs. 236; p=0.06), indicating that the CD123 molecule on immature MDSCs is targeted effectively by TAL.ConclusionSingle agent TAL has limited efficacy in patients with advanced myeloid malignancies failing HMA. Expression of CD123 on immature MDSCs might serve as a biomarker of response for future anti-CD123 targeted approaches. [Display omitted] DisclosuresGötze:Celgene: Honoraria, Research Funding; JAZZ Pharmaceuticals: Honoraria; Novartis: Honoraria; Takeda: Honoraria, Other: Travel aid ASH 2017. Krönke:Celgene: Honoraria. Middeke:Roche: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Fenaux:Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Otsuka: Honoraria, Research Funding. Schlenk:Pfizer: Research Funding, Speakers Bureau. Ades:JAZZ: Honoraria; Takeda: Membership on an entity's Board of Directors or advisory committees; silent pharma: Consultancy; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Platzbecker:Celgene: Research Funding.

Chronic Inflammation Contributes to Tumor Growth: Possible Role of L-Selectin-Expressing Myeloid-Derived Suppressor Cells (MDSCs).

Recent data have demonstrated that chronic inflammation is a crucial component of tumor initiation and progression. We previously reported that immature myeloid-derived suppressor cells (MDSCs) with immunosuppressive activity toward effector T cellswere expanded in experimental chronic inflammation. We hypothesized that elevated levels of MDSCs, induced by chronic inflammation, may contribute to the progression of tumor growth. Using the Ehrlich carcinoma animal model, we found increased tumor growth in mice with chronic adjuvant arthritis, which was accompanied by a persistent increase in the proportion of splenic monocytic and granulocytic MDSCs expressing CD62L (L-selectin), when compared to tumor mice without adjuvant arthritis. Depletion of inflammation-induced MDSCs resulted in decreased tumor growth. In vitro studies demonstrated that increased expression of CD62L by MDSCs was mediated by TNFα, elevated concentrations of which were found in tumor mice subjected to chronic inflammation. Moreover, the addition of exogenous TNFα markedly enhanced the suppressive activity of bone marrow-derived MDSCs, as revealed by the ability to impair the proliferation of CD8+ T cells in vitro.This study provides evidence that chronic inflammation may promote tumor growth via induction of CD62L expression by MDSCs that can facilitate their migration to tumor and lymph nodes and modulation of their suppressor activity.

Myeloid-derived suppressor cell accumulation in renal cell carcinoma is correlated with CCL2, IL-17 and IL-18 expression in blood and tumors.

Myeloid-derived suppressor cells (MDSC) play an important role in tumor-mediated immune evasion. Levels of MDSC in peripheral blood are increased in patients with cancer, correlating with cancer stage and outcome. Studies have confirmed the associations between MDSC and various cytokines in the peripheral blood of murine and human cancer hosts. However, little is known about the association between parenchymal MDSC subsets and cytokines, or the mechanism drawing MDSC into tumor parenchyma. The aim of this study was to analyze the correlation between MDSC subsets and tumor grade as well as stage in renal cell carcinoma (RCC) patients. The expression of chemokine (C-C motif) ligand 2 (CCL2), interleukin 17 (IL-17) and interleukin 18 (IL-18) in the peripheral blood and parenchyma of RCC patients was also detected to explore its correlation with MDSC accumulation. Total MDSC, granulocytic MDSC (G-MDSC), monocytic MDSC (M-MDSC), and immature MDSC (I-MDSC) from the blood and parenchyma were isolated and analyzed by flow cytometry. Cytokines were detected by the enzyme-linked immunosorbent assay (ELISA), real-time polymerase chain reaction (PCR) and western blot in blood and tumors. Parenchymal levels of MDSC had a positive correlation with levels of CCL2, IL-17, and IL-18, suggesting these cytokines may attract MDSC into the parenchyma. Moreover, peripheral total MDSC, G-MDSC and I-MDSC were shown to correlate with tumor grade and stage. Gene and protein expression of CCL2, IL-17, and IL-18 was significantly increased in blood and tumors of RCC patients. Our study has provided potential new targets for the risk stratification of patients with limited stages of renal carcinoma, in addition to elucidating a possible association between MDSC subsets and cytokine-induced migration into the tumor tissue.

Immune Effector Recovery in Chronic Myeloid Leukemia and Treatment-Free Remission.

Chronic myeloid leukemia (CML) is a hematological cancer, characterized by a reciprocal chromosomal translocation between chromosomes 9 and 22 [t(9;22)], producing the Bcr-Abl oncogene. Tyrosine kinase inhibitors (TKIs) represent the standard of care for CML patients and exert a dual mode of action: direct oncokinase inhibition and restoration of effector-mediated immune surveillance, which is rendered dysfunctional in CML patients at diagnosis, prior to TKI therapy. TKIs such as imatinib, and more potent second-generation nilotinib and dasatinib induce a high rate of deep molecular response (DMR, BCR-ABL1 ≤ 0.01%) in CML patients. As a result, the more recent goal of therapy in CML treatment is to induce a durable DMR as a prelude to successful treatment-free remission (TFR), which occurs in approximately half of all CML patients who cease TKI therapy. The lack of overt relapse in such patients has been attributed to immunological control of CML. In this review, we discuss an immunological timeline to successful TFR, focusing on the immunology of CML during TKI treatment; an initial period of immune suppression, limiting antitumor immune effector responses in newly diagnosed CML patients, linked to an expansion of immature myeloid-derived suppressor cells and regulatory T cells and aberrant expression of immune checkpoint signaling pathways, including programmed death-1/programmed death ligand-1. Commencement of TKI treatment is associated with immune system re-activation and restoration of effector-mediated [natural killer (NK) cell and T cell] immune surveillance in CML patients, albeit with differing frequencies in concert with differing levels of molecular response achieved on TKI. DMR is associated with maximal restoration of immune recovery in CML patients on TKI. Current data suggest a net balance between both the effector and suppressor arms of the immune system, at a minimum involving mature, cytotoxic CD56dim NK cells may be important in mediating TFR success. However, a major goal remains in CML to identify the most effective pathways to target to maximize an advantageous immune response and promote TFR success.

Sepsis Pathophysiology, Chronic Critical Illness, and Persistent Inflammation-Immunosuppression and Catabolism Syndrome.

To provide an appraisal of the evolving paradigms in the pathophysiology of sepsis and propose the evolution of a new phenotype of critically ill patients, its potential underlying mechanism, and its implications for the future of sepsis management and research. Literature search using PubMed, MEDLINE, EMBASE, and Google Scholar. Sepsis remains one of the most debilitating and expensive illnesses, and its prevalence is not declining. What is changing is our definition(s), its clinical course, and how we manage the septic patient. Once thought to be predominantly a syndrome of over exuberant inflammation, sepsis is now recognized as a syndrome of aberrant host protective immunity. Earlier recognition and compliance with treatment bundles has fortunately led to a decline in multiple organ failure and in-hospital mortality. Unfortunately, more and more sepsis patients, especially the aged, are suffering chronic critical illness, rarely fully recover, and often experience an indolent death. Patients with chronic critical illness often exhibit "a persistent inflammation-immunosuppression and catabolism syndrome," and it is proposed here that this state of persisting inflammation, immunosuppression and catabolism contributes to many of these adverse clinical outcomes. The underlying cause of inflammation-immunosuppression and catabolism syndrome is currently unknown, but there is increasing evidence that altered myelopoiesis, reduced effector T-cell function, and expansion of immature myeloid-derived suppressor cells are all contributory. Although newer therapeutic interventions are targeting the inflammatory, the immunosuppressive, and the protein catabolic responses individually, successful treatment of the septic patient with chronic critical illness and persistent inflammation-immunosuppression and catabolism syndrome may require a more complementary approach.

P2.04-019 A Peripheral Immune Signature Associated with Clinical Activity of Sunitinib in Thymic Carcinoma: Topic: Thymic Malignancies Clinical and Translational

We have previously reported an objective response rate of 26% and disease stabilization in 65% of patients with advanced thymic carcinoma (TC) treated with the multi kinase inhibitor sunitinib after failure of platinum-based chemotherapy. The current study investigates the impact of sunitinib on systemic immunity in patients with thymic epithelial tumors with an aim to discover blood-based, predictive immune biomarkers. Patients with thymoma and TC received sunitinib at a dose of 50 mg once daily in 6-week cycles consisting of 4 weeks of treatment followed by 2 weeks without treatment. Results from 15 patients with TC are reported here. Blood samples were collected before initiation of sunitinib therapy (Cycle 1 day 1; C1D1), and prior to treatment on day 1 of cycles 2 and 3 (C2D1; C3D1). Multiparameter flow cytometry was used to study T-cell subsets with immune checkpoint expression, four phenotypes of myeloid-derived suppressor cells (MDSCs) with CD40, and CD14+ monocytes with HLA-DR expression. Expression of 730 immune-related genes in peripheral blood was analyzed by NanoString technology. Differences in paired markers or changes in markers between two time points was evaluated by the Wilcoxon signed rank test. The Kaplan-Meier method was used to obtain estimates of progression-free survival (PFS) and overall survival (OS). Immunosuppressive Tim-3-positive Tregs declined after 2 cycles of sunitinib (p=0.024). A decrease in granulocytic MDSCs (p=0.012), lineage negative (CD3-CD19-CD56-) MDSCs (p=0.013), and immature MDSCs (p=0.01) but not monocytic MDSCs was observed after 1 cycle of sunitinib. TC patients with no objective response to sunitinib had a higher baseline immature MDSC level than responders (p=0.0044). Greater than median declines in granulocytic MDSC CD40 (C2D1 p=0.027, C3D1 p=0.0046) and lineage-MDSC CD40 (C3D1, p=0.0046) after sunitinib therapy was associated with improved PFS. Similarly, a greater than median decline in CD14+HLA-DRlo/neg monocyte levels on C2D1 was associated with longer PFS (p=0.020). Among the immune genes examined, higher baseline FEZ1 expression was associated with improved PFS and OS. Our findings suggest significant interplay between sunitinib and systemic immunity impacts therapeutic outcome in TC. Monitoring CD40 expression on specific MDSC phenotypes and FEZ1 gene expression may predict a survival benefit after treatment with sunitinib. These results, if validated in larger studies, can serve as potential blood-based predictive biomarkers in TC patients treated with sunitinib.