Granulocyte Subsets Research Articles

PS1349 UPDATED RISK STRATIFICATION MODEL FOR SMOLDERING MULTIPLE MYELOMA (SMM) INCORPORATING THE REVISED IMWG DIAGNOSTIC CRITERIA

Background: Deep understanding of the complexity and diversity of the TIME and its influence on response to therapy is needed to improve the ability to predict, monitor and guide immunotherapeutic responsiveness. Among cells composing the MM-TIME, granulocytic-MDSCs (G-MDSCs) have a prominent role in promoting tumor growth and inducing immunosuppression; however, their phenotype in MM is not well-established. Aims: To define the phenotype of G-MDSCs based on the integration of phenotypic data, immunosuppressive potential, gene regulatory networks and impact on patients’ outcome of different granulocytic subsets present in the MM-TIME. Methods: We used multidimensional flow cytometry (MFC) to evaluate the pre-established phenotype of G-MDSCs in bone marrow (BM) samples from healthy donors (HD) (n = 4) and MM patients (n = 5). We then used principal component analysis (PCA) to unbiasedly identify different granulocytic subsets in the MM-TIME, and FACSorted them for in vitro experiments to analyze their immunosuppressive potential (n = 9) and for RNAseq to analyze the molecular profile of G-MDSCs in MM (n = 5) vs HD (n = 5). The clinical significance of these subsets was determined comparing their numbers at diagnosis within the BM TIME of MM patients (n = 71) included in the GEM2012MENOS65 trial. Results: Human G-MDSCs have been defined as a cell population displaying a CD11b-CD14-CD15+CD33+HLADR- phenotype, representing 1% of total BM nucleated cells in HD and nearly 25% in MM patients. However, we found that the percentage of cells with this phenotype was similar in the BM of HD and MM patients (median of 8% in both, P>.99). Using MFC and according to PCA, 3 granulocyte subsets were unbiasedly identified in the BM of HD and MM, based on homogeneous CD14-CD15+CD33+HLADR- expression but differential reactivity against CD11b, CD13 and CD16: CD11b-CD13lo/-CD16-, CD11b+CD13lo/-CD16- and CD11b+CD13+CD16+. The percentage of all three subsets was similar (P>.5) between HD and MM. Afterwards, we used FACSorting to isolate (1) or deplete (2) individually each of the 3 subsets from MM-BM and determine its immunosuppressive potential in 2 assays. In (1), we noted a significant decrease in T cell proliferation when these were stimulated with CD3/CD28 and in presence of the CD11b+CD13+CD16+ neutrophil subset (0.5-fold, P = .01) but not of the CD11b-CD13lo/-CD16- and CD11b+CD13lo/-CD16- subsets. In (2), we noted that the cytotoxic potential of T cells significantly increased in presence of the BCMAxCD3 bispecific antibody (P = .04) reaching its maximum with the depletion of the CD11b+CD13+CD16+ subset (4-fold, P = .007). Additionally, RNAseq of the 3 subsets in HD and MM patients revealed that genes commonly associated with G-MDSCs (e.g. PTGS2, TGFβ1) were specifically upregulated in the CD11b+CD13+CD16+ granulocytic subset. Finally, we analyzed the distribution of the 3 subsets in the BM of MM patients. Interestingly, we observed that patients with a high number of CD11b+CD13+CD16+ neutrophils at baseline had lower count of T cells and that patients with low ratio between CD11b+CD13+CD16+ and T cells had inferior 3-year rates of progression-free survival as compared to the remaining patients (100% vs 75%, P = .03). Summary/Conclusion: In this comprehensive analysis that integrated molecular, phenotypic, functional and clinical data, we determined a correlation between three well-defined granulocytic subsets and their immunosuppressive potential, thereby providing for the first time, a set of optimal markers (CD11b/CD13/CD16) for monitoring G-MDSCs in MM.

Ferulic acid altered IL-17A/IL-17RA interaction and protected against imiquimod-induced psoriasis-like skin injury in mice

Ferulic acid (FA), a phenolic phytochemical, is commonly found in grains, vegetables, and fruits. Interleukin-17A (IL-17A) and IL-17 receptor A (IL-17RA) interaction is one of important therapeutic targets for psoriasis. Here we analyzed the FA effects on IL-17A/IL-17RA interaction and psoriasis-like skin injury induced by imiquimod (IMQ). IL-17A-blocking assay and docking analysis showed that FA interacted with Trp-67, Gln-94, and Glu-95 residues of IL-17A via hydrogen bonds and consequently abolished the binding of IL-17RA to IL-17A. Mice were topically given with IMQ and orally given with various amounts of FA for 14 consecutive days. FA attenuated IMQ-induced psoriasis-like skin lesions in a dose-dependent manner, and the epidermal thickness of mice treated with 100 mg/kg FA was reduced by 53.48 ± 4.44% in comparison with sham. Global analysis of differentially expressed genes showed that IMQ and FA significantly affected immune response, metabolism, and mitogen-activated protein kinase signaling pathways. Immunohistochemical staining showed that FA inhibited the infiltration and the cytokine secretion of Th17 cell, dendritic cell, and granulocyte subsets in psoriatic skin tissues. In conclusion, we newly identified that oral administration of FA protected against IMQ-induced psoriatic skin injury in mice. Moreover, its protection was associated with the interference of IL-17A/IL-17RA interaction.

Neutrophils in lupus nephritis.

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease characterized by IgG-autoantibodies to nuclear antigens that can deposit in the kidney and trigger lupus nephritis. Neutrophils accumulate in the kidneys of patients with proliferative LUPUS NEPHRITIS and neutrophil products and a subset of granulocytes, called low-density granulocytes (LDG) may contribute to lupus nephritis pathogenesis. Here, we will discuss recent studies implicating neutrophils in the pathogenesis of human SLE nephritis and then examine studies that provide mechanistic insights into how these cells are recruited to the glomerulus following immune complex deposition and how their products may promote lupus nephritis. SLE patients display unique blood transcriptional signatures linked to Type I interferon and myeloblast differentiation, which could help stratify lupus nephritis progression. Multiphoton intravital microscopy of kidney glomerular capillaries revealed a role for neutrophil FcγRs in the rapid capture of neutrophils following immune complex deposition. The view that reduced degradation of neutrophil extracellular traps (NETS) contributes to lupus nephritis progression, is now challenged by experimental data in lupus-prone mice that genetically fail to produce NETS but still are afflicted. A greater understanding of the neutrophil dependent mechanisms that promote lupus nephritis may potentially inform on newer therapeutic options that target neutrophil accumulation and reactivity in the nephritic kidney.

Detailed Phenotypic, Molecular and Functional Profiling of Myeloid Derived Suppressor Cells (MDSCs) in the Tumor Immune Microenvironment (TIME) of Multiple Myeloma (MM)

Detailed Phenotypic, Molecular and Functional Profiling of Myeloid Derived Suppressor Cells (MDSCs) in the Tumor Immune Microenvironment (TIME) of Multiple Myeloma (MM)

Characterization of monocytic and granulocytic subsets of myeloid-derived suppressor cells in blood donors with occult hepatitis B virus infection.

Myeloid-derived suppressor cells (MDSCs) accumulate from many diseases. MDSCs are rarely explored in occult hepatitis B virus infection (OBI). The frequency of monocytic MDSCs (M-MDSCs) and granulocytic MDSCs (G-MDSCs) in OBI carriers was analyzed for correlation with clinical parameters, which was no different between OBI and healthy individuals, whereas the frequency of M-MDSCs but G-MDSCs in OBI was significantly lower than that observed in chronic hepatitis B carriers (0.4% vs 0.7%, P = 0.0004). The frequency of MDSCs was not correlated with clinical parameters and viral load of OBI, suggesting that the absence of HBsAg in OBI carriers might not induce the accumulation of MDSCs.

Targeted hypoxia reduction restores T cell infiltration and sensitizes prostate cancer to immunotherapy.

Despite the success of immune checkpoint blockade against melanoma, many "cold" tumors like prostate cancer remain unresponsive. We found that hypoxic zones were prevalent across preclinical prostate cancer and resisted T cell infiltration even in the context of CTLA-4 and PD-1 blockade. We demonstrated that the hypoxia-activated prodrug TH-302 reduces or eliminates hypoxia in these tumors. Combination therapy with this hypoxia-prodrug and checkpoint blockade cooperated to cure more than 80% of tumors in the transgenic adenocarcinoma of the mouse prostate-derived (TRAMP-derived) TRAMP-C2 model. Immunofluorescence imaging showed that TH-302 drives an influx of T cells into hypoxic zones, which were expanded by checkpoint blockade. Further, combination therapy reduced myeloid-derived suppressor cell density by more than 50%, and durably reduced the capacity of the tumor to replenish the granulocytic subset. Spontaneous prostate tumors in TRAMP transgenic mice, which completely resist checkpoint blockade, showed minimal adenocarcinoma tumor burden at 36 weeks of age and no evidence of neuroendocrine tumors with combination therapy. Survival of Pb-Cre4, Ptenpc-/-Smad4pc-/- mice with aggressive prostate adenocarcinoma was also significantly extended by this combination of hypoxia-prodrug and checkpoint blockade. Hypoxia disruption and T cell checkpoint blockade may sensitize some of the most therapeutically resistant cancers to immunotherapy.

Opposing roles of eosinophils in cancer.

Eosinophils are a subset of granulocytes mostly known for their ability to combat parasites and induce allergy. Although they were described to be related to cancer more than 100years ago, their role in tumors is still undefined. Recent observations revealed that they display regulatory functions towards other immune cell subsets in the tumor microenvironment or direct cytotoxic functions against tumor cells, leading to either antitumor or protumor effects. This paradoxical role of eosinophils was suggested to be dependent on the different factors in the TME. In addition, the clinical relevance of these cells has been recently addressed. In most cases, the accumulation of eosinophils both in the tumor tissue, called tumor-associated tissue eosinophilia, and in the peripheral blood were reported to be prognostic markers for a better outcome of cancer patients. In immunotherapy of cancer, particularly in therapy with immune checkpoint inhibitors, eosinophils were even shown to be a potential predictive marker for a beneficial clinical response. A better understanding of their role in cancer progression will help to establish them as prognostic and predictive markers and to design strategies for targeting eosinophils.

Abstract 1100: Screening the chemical library against granulocytic MDSCs: Critical player in breast cancer metastasis

Abstract We recently demonstrated that infiltration of granulocytic MDSCs in distant organs is a critical step in metastatic process. The mouse transcriptome analysis of in vitro co-cultures and samples from syngeneic mouse model revealed that granulocytic subset of myeloid-derived suppressor cells (gMDSCs) from metastatic 4T1 tumor bearing mice are regulated a distinct set of genes. Two genes, S100A8 and S100A9 were highly upregulated in gMDSCs isolated from mice with metastatic 4T1 tumors compared to mice with non-invasive tumors. Using the recombinant single S100A8, S100A9 proteins or the S100A8/S100A9 heterotetramer (calprotectin), we demonstrated that calprotectin is a critical player in gMDSC induction and infiltration in distant organs particularly in lungs. Furthermore, injection of recombinant calprotectin but not single S100A8 or S100A9 proteins via tail vein enhanced the metastatic ability of nan-invasive EMT6 tumors in mice. We therefore performed computational screen of NCI compounds against the crystal structure of calprotectin and identified over 100 lead compounds. In vitro gMDSC differentiation assay identified 3 compounds with strong gMDSC inhibitory activity. We therefore designed a pilot experiment to test these compounds in preclinical mouse models. We also compared the activity of these compounds against tasquinimod, a small molecule targeting S100A9 only. However, tasquinimod treatment of 4T1 tumor-bearing mice had a moderate anti-tumor activity which may be due to a limited activity on granulocytic MDSC accumulation. In addition, we determined that there was a significant upregulation of S100A8 in MDSCs from tasquinimod treated mice. This data suggested that inhibiting only S100A9 leads to activation of S100A8 and thus may be ineffective targeting of MDSCs. In line with these data, one of the compounds (#10) showed a potent activity against gMDSCs in 4T1 tumor-bearing mice and significantly inhibited pulmonary metastasis. Moreover, this compound eliminated the cytotoxicity caused by cyclophosphamide and animals were free of cancer. In summary, we have identified a molecular target which regulates gMDSC induction and play critical role in metastatic process and our findings from in vitro screens and preclinical testing provide a strong rationale for targeting MDSCs. Citation Format: Hasan Korkaya, Eunmi Lee, Raziye Piranioglu, Thomas Albers, Maria Ouzounova, Charlie Weeks, Riley Rodier, Ahmet K. Korkaya, Khaled A. Hassan. Screening the chemical library against granulocytic MDSCs: Critical player in breast cancer metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1100.

Myeloid-derived suppressor cells (MDSCs) in patients with solid tumors: considerations for granulocyte colony-stimulating factor treatment.

Myeloid-derived suppressor cells (MDSCs) have been shown to contribute to tumor escape from host immune surveillance and to cancer progression by production of tumor-promoting soluble factors. Granulocyte colony-stimulating factor (G-CSF) is a principle cytokine controlling granulocyte number. Recombinant human G-CSF (rhG-CSF) has become the main therapeutic agent for the treatment of neutropenia and prophylaxis of febrile neutropenia in cancer patients. However, we show here that rhG-CSF triggers accumulation of granulocytic and monocytic subsets. Consequently, we discuss the pharmacological use of granulopoiesis stimulating factors not only in the context of febrile neutropenia but also from the perspective of MDSC-dependent and MDSC-independent mechanisms of immunosuppression and cancer angiogenesis.

Accumulation of tumor infiltrating myeloid-derived suppressor cells associates with changes in the immune landscape of clear cell renal cell carcinoma.

655 Background: Myeloid-derived suppressor cells (MDSC) are capable of inducing profound immune suppression of anti-tumor T cell responses. Here we examined the ability of intratumoral MDSC accumulation to alter the immune landscape of RCC and to identify the factors involved. Methods: Using flow cytometry, 41 clear cell RCC nephrectomy samples were assessed for their total MDSC infiltrate and the percentage of granulocytic (PMN-MDSC) or monocytic (M-MDSC) subsets. RNA isolated from these tumor samples and 4 non-tumor samples was also evaluated for expression levels of immune-related genes using a Nanostring PanCancer immune panel. A multiple linear regression model was used to identify which immune-related genes might be significantly associated with PMN-MDSC intratumoral accumulation. Log-Rank test was used for comparison of survival curves. Results: Genes encoding cytokines, cancer-testis antigens, interleukins, and T cell function were differentially expressed by clear cell RCC and the non-tumor samples. The transcription of 55 immune-related genes was significantly associated (FDR adjusted p < 0.05) with PMN-MDSC infiltration, including mediators of MDSC recruitment such as CXCL1, CXCL3, CXCL5, CXCR2, IL8, LIF, S100A8, CSF3R, and CCR3, and molecules governing MDSC expansion and function such as IL10, C/EBPB, CD44, COX2, and NFATC3. When a statistically significant 10 gene signature was analyzed in the context of patient survival using the TCGA database of clear cell RCC patients (n = 945), a strong association between the expression of these genes and reduced survival was observed. Moreover, this association seemed to be additive, with expression of 7-10 of these genes correlating with poorer survival when compared to patients expressing 3 or less (p < 0.0001). Conclusions: Consistent with previous studies defining the immunoregulatory role of MDSCs, these results suggest that MDSC accumulation can alter the inflammatory state of the tumor, and indicate that mediators associated with the function of PMN-MDSCs can have a negative impact on outcome. Mechanistic studies aimed at identifying the functionally relevant mediators are ongoing.

Granulocytes: New Members of the Antigen-Presenting Cell Family.

Granulocytes, the most abundant types of leukocytes, are the first line of defense against pathogen invasion. However, the plasticity and diversity of granulocytes have been increasingly revealed, especially with regard to their versatile functions in orchestrating adaptive immune responses. A substantial body of recent evidence demonstrates that granulocytes can acquire the function as antigen-presenting cells under pathological or inflammatory conditions. In addition, they can acquire surface expression of MHC class II and costimulatory molecules as well as T cell stimulatory behavior when cultured with selected cytokines. The classic view of granulocytes as terminally differentiated, short-lived phagocytes is therefore changing to phenotypically and functionally heterogeneous cells that are engaged in cross-talk with other leukocyte populations and provide an additional link between innate and adaptive immunity. In this brief review, we summarize the current knowledge on the antigen-presenting capacity of granulocyte subsets (neutrophils, eosinophils, and basophils). Underlying mechanisms, relevant physiological significance and potential controversies are also discussed.

Myeloid-derived Suppressor Cells Are Necessary for Development of Pulmonary Hypertension.

Pulmonary hypertension (PH) complicates the care of patients with chronic lung disease, such as idiopathic pulmonary fibrosis (IPF), resulting in a significant increase in morbidity and mortality. Disease pathogenesis is orchestrated by unidentified myeloid-derived cells. We used murine models of PH and pulmonary fibrosis to study the role of circulating myeloid cells in disease pathogenesis and prevention. We administered clodronate liposomes to bleomycin-treated wild-type mice to induce pulmonary fibrosis and PH with a resulting increase in circulating bone marrow-derived cells. We discovered that a population of C-X-C motif chemokine receptor (CXCR) 2+ myeloid-derived suppressor cells (MDSCs), granulocytic subset (G-MDSC), is associated with severe PH in mice. Pulmonary pressures worsened despite improvement in bleomycin-induced pulmonary fibrosis. PH was attenuated by CXCR2 inhibition, with antagonist SB 225002, through decreasing G-MDSC recruitment to the lung. Molecular and cellular analysis of clinical patient samples confirmed a role for elevated MDSCs in IPF and IPF with PH. These data show that MDSCs play a key role in PH pathogenesis and that G-MDSC trafficking to the lung, through chemokine receptor CXCR2, increases development of PH in multiple murine models. Furthermore, we demonstrate pathology similar to the preclinical models in IPF with lung and blood samples from patients with PH, suggesting a potential role for CXCR2 inhibitor use in this patient population. These findings are significant, as there are currently no approved disease-specific therapies for patients with PH complicating IPF.

Abstract 948: Characterization of the microenvironment of murine primary triple negative breast cancer

Abstract The purpose of this study was to investigate the role of inflammatory cells in the metastatic process using reliably metastatic murine models of Triple Negative Breast Cancer (TNBC). We have previously selected, developed and characterized two reliably metastatic TNBC mouse models for our investigations. The T11 (claudin-low) and 2225LM (basal-like) Balb/c-derived transplantable tumors display molecular profiles that mirror human TNBC. Here we report characterization of the inflammatory cells and microenvironment in these primary TNBC tumors and at metastatic sites in both heterotopic and orthotopic models. Tumors were implanted in the s.c. flank or mammary fat pad and resected 1-2 weeks later to promote the growth of seeded metastases, when volumes reached ~700 mm3 or 300 mm3, respectively. Both flow cytometric analysis and immunohistochemistry of primary tumors demonstrated high infiltration by myeloid-derived cells (CD11b+) and low levels of lymphoid cells (CD3+). Myeloid cells were also the major infiltrating cells in lung metastases and were significantly elevated compared to normal lung. The granulocytic subset (CD11b+Ly6G+) predominated, consistent with an immunosuppressive role for cells with this phenotype (N2, G-MDSC, etc.). Primary 2225LM and T11 tumors and metastatic lung tumor homogenates were assayed for immunomodulators and compared to normal breast and lung tissue from age-matched contemporary controls. G-CSF was significantly increased in tumors and levels (pg/mg protein) were correlated with tumor burden. VEGF was significantly elevated in all tumors, as were chemoattractants for granulocytic cells (KC/CXCL1, MIP-2/CXCL2), monocytic cells (MCP-1/CCL2), eosinophils (Eotaxin/CCL11) and T cells (MIG/CXCL-9). In the heterotopic model, lung levels of KC/CXCL1 and MCP-1/CCL2 were significantly increased prior to frank lung metastasis (5-30 days post-implant). These data suggest that TNBC-derived G-CSF may play a role in the mobilization of CD11b+Ly6G+ granulocytes and progenitors from the bone marrow and key chemokines may mediate migration of these cells to metastatic sites. Future studies will define phenotypic and functional characteristics of the G-MDSC that are promoting tumor progression in these murine TNBC models. Citation Format: Kassondra Balestrieri, Keith Pittman, Mohamed Ramez, Nasreen Vohra, Kathryn Verbanac. Characterization of the microenvironment of murine primary triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 948. doi:10.1158/1538-7445.AM2017-948

Abstract 2956: Chemical library screen identifies compounds that target S100A8/S100A9 complex and MDSC accumulation

Abstract We previously demonstrated that MDSC subsets accumulated in primary tumor and distant organs regulate tumor plasticity. The mouse transcriptome analysis of in vitro co-cultures and samples from syngeneic mouse model revealed that granulocytic subset of myeloid-derived suppressor cells (gMDSCs) from metastatic 4T1 tumor bearing mice regulate several hundred genes in tumor cells upon co-culture. The top genes are S100A8, S100A9, MMP8, FPR1, CCL3, and TGFβ2 which also predicted poor survival in human solid tumors including breast cancer. Therefore, we called these 6 genes as “metastatic gene signature”. It has been reported that S100A8/S100A9 heterotetramer, called calprotectin, play a key role in inflammation-associated cancer progression. To investigate the role of calprotectin (S100A8/A9) in tumor-mediated immunosuppression and metastasis, we first utilized Tasquinimod, a small molecule targeting S100A9 only. However, Tasquinimod treatment of 4T1 tumor-bearing mice had a moderate anti-tumor activity which may be due to a limited activity on granulocytic MDSC accumulation. In addition, we determined that there was a significant upregulation of S100A8 in MDSCs from Tasquinimod treated mice. This data suggested that inhibiting only S100A9 leads to activation of S100A8 and thus may be ineffective targeting of MDSCs. We therefore run a computational screen of the NCI chemical library against the crystal structure of calprotectin (S100A8/S100A9) and identified 40 lead compounds. We then performed in vitro screening assay to identify compounds that inhibit MDSC induction. We identified 3 compounds that significantly suppressed gMDSC differentiation. We are currently performing in vivo studies with these 3 candidate drugs in our murine breast cancer model and will present our findings at the AACR meeting. We believe that this study will provide a novel drug targeting S100A8/S100A9 heterotetramer, a key molecule in MDSC induction and its regulatory functions during tumor progression. Citation Format: Eunmi Lee, Maria Ouzounova, Raziye Piranlioglu, Abdeljabar El Andaloussi, Sena Arbag, Gang Zhou, Hasan Korkaya. Chemical library screen identifies compounds that target S100A8/S100A9 complex and MDSC accumulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2956. doi:10.1158/1538-7445.AM2017-2956

Abstract 3992: Immune regulation of disseminated tumor cell clearance versus metastatic growth

Abstract Metastatic disease is the end stage of extremely inefficient processes that entail overcoming multiple barriers including anti-tumor immunity. Although evidences from preclinical and clinical settings suggest that dissemination of malignant cells is an early process, majority of disseminated cells either eliminated or remain dormant in distant organs, while very few cells eventually develop successful metastasis. Therefore, it is widely accepted that dynamic and reversible tumor cell plasticity is required for metastasis, however, in vivo steps and molecular mechanisms are poorly elucidated. We provide evidence that monocytic and granulocytic subsets of myeloid derived suppressor cells (m-MDS, g-MDSC) infiltrated in primary 4T1 tumor and distant organs with different time kinetics regulate spatiotemporal tumor plasticity. Using co-culture experiments and syngeneic mouse models of murine 4T1 (metastatic) tumor, we demonstrated that tumor infiltrated m-MDSCs facilitate tumor cell dissemination from the primary site by inducing the EMT/CSC phenotype. In contrast, g-MDSCs infiltrated in the lungs support metastatic growth by reverting the EMT/CSC phenotype and thus promoting tumor cell proliferation. In contrast, less invasive EMT6 tumors fail to induce efficient pulmonary infiltration of g-MDSCs and results in clearance of disseminated tumor cells in the lungs. Gene expression analyses of tumors and MDCS subsets in primary tumor site and distant organs at different time points reveal mechanistic temporal regulation of in vivo tumor plasticity by m-MDSC and g-MDSC subsets in 4T1 tumor-bearing mice. However, the lung microenvironment of EMT6 tumor-bearing mice display a gene expression signature of anti-tumor immunity which predict better survival in breast cancer patients. In our functional studies, we demonstrate that EMT6 tumor-bearing animals efficiently eliminate disseminated tumor cells in the lungs. Furthermore, g-MDSCs isolated from 4T1-tumor bearing animals significantly enhance metastatic growth of already disseminated tumor cells. Consistent with the “seed and soil” hypothesis, our studies provide a molecular mechanism by which the immune system regulate spatiotemporal tumor plasticity and generation of permissive or anti-tumorigenic microenvironment in distant organs determining the fate of disseminated tumor cells. Citation Format: Hasan Korkaya, Eunmi Lee, Raziye Piranioglu, Maria Ouzounova, Abdeljabar El-Andaloussi, Iskander Asm, Ahmet K. Korkaya, Gang Zhou, Ali Arbab, Paulo Rodriguez. Immune regulation of disseminated tumor cell clearance versus metastatic growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3992. doi:10.1158/1538-7445.AM2017-3992

Adhesion-induced eosinophil cytolysis requires the receptor-interacting protein kinase 3 (RIPK3)–mixed lineage kinase-like (MLKL) signaling pathway, which is counterregulated by autophagy

Eosinophils are a subset of granulocytes that can be involved in the pathogenesis of different diseases, including allergy. Their effector functions are closely linked to their cytotoxic granule proteins. Release takes place through several different mechanisms, one of which is cytolysis, which is associated with release of intact granules, so-called clusters of free eosinophil granules. The mechanism underlying this activation-induced form of cell death in eosinophils has remained unclear. We aimed to elucidate the molecular mechanism of eosinophil cytolysis. Isolated blood eosinophils were incubated on glass coverslips coated with intravenous immunoglobulin and inactive complement component 3b. Amorphologic characterization of the distinct stages of the proposed cascade was addressed by means of time-lapse automated fluorescence microscopy, electron microscopy, and immunohistochemistry. Experiments with pharmacologic inhibitors were performed to elucidate the sequence of events within the cascade. Tissue samples of patients with eosinophilic skin diseases or eosinophilic esophagitis were used for invivo analyses. After eosinophil adhesion, we observed reactive oxygen species production, early degranulation, and granule fusion processes, leading to a distinct morphology exhibiting cytoplasmic vacuolization and, finally, cytolysis. Using a pharmacologic approach, we demonstrate the presence of a receptor-interacting protein kinase 3 (RIPK3)-mixed lineage kinase-like (MLKL) signaling pathway in eosinophils, which, after its activation, leads to the production of high levels of reactive oxygen species in a p38 mitogen-activated protein kinase and phosphatidylinositol 3'-kinase-dependent manner. All these steps are required for cytoplasmic vacuolization and subsequent cytolysis to occur. Interestingly, triggering cytolysis is associated with an induction of autophagy in eosinophils, and additional stimulation of autophagy by means of pharmacologic inhibition of the mechanistic target of rapamycin counterregulates cell death. Moreover, MLKL phosphorylation, cytoplasmic vacuolization, and cytolysis were observed in eosinophils under invivo inflammatory conditions. We report that adhesion-induced eosinophil cytolysis takes place through RIPK3-MLKL-dependent necroptosis, which can be counterregulated by autophagy.

Thiol-Reactive Star Polymers Display Enhanced Association with Distinct Human Blood Components.

Directing nanoparticles to specific cell types using nonantibody-based methods is of increasing interest. Thiol-reactive nanoparticles can enhance the efficiency of cargo delivery into specific cells through interactions with cell-surface proteins. However, studies to date using this technique have been largely limited to immortalized cell lines or rodents, and the utility of this technology on primary human cells is unknown. Herein, we used RAFT polymerization to prepare pyridyl disulfide (PDS)-functionalized star polymers with a methoxy-poly(ethylene glycol) brush corona and a fluorescently labeled cross-linked core using an arm-first method. PDS star polymers were examined for their interaction with primary human blood components: six separate white blood cell subsets, as well as red blood cells and platelets. Compared with control star polymers, thiol-reactive nanoparticles displayed enhanced association with white blood cells at 37 °C, particularly the phagocytic monocyte, granulocyte, and dendritic cell subsets. Platelets associated with more PDS than control nanoparticles at both 37 °C and on ice, but they were not activated in the duration examined. Association with red blood cells was minor but still enhanced with PDS nanoparticles. Thiol-reactive nanoparticles represent a useful strategy to target primary human immune cell subsets for improved nanoparticle delivery.

Monocytic and granulocytic myeloid derived suppressor cells differentially regulate spatiotemporal tumour plasticity during metastatic cascade

It is widely accepted that dynamic and reversible tumour cell plasticity is required for metastasis, however, in vivo steps and molecular mechanisms are poorly elucidated. We demonstrate here that monocytic (mMDSC) and granulocytic (gMDSC) subsets of myeloid-derived suppressor cells infiltrate in the primary tumour and distant organs with different time kinetics and regulate spatiotemporal tumour plasticity. Using co-culture experiments and mouse transcriptome analyses in syngeneic mouse models, we provide evidence that tumour-infiltrated mMDSCs facilitate tumour cell dissemination from the primary site by inducing EMT/CSC phenotype. In contrast, pulmonary gMDSC infiltrates support the metastatic growth by reverting EMT/CSC phenotype and promoting tumour cell proliferation. Furthermore, lung-derived gMDSCs isolated from tumour-bearing animals enhance metastatic growth of already disseminated tumour cells. MDSC-induced ‘metastatic gene signature’ derived from murine syngeneic model predicts poor patient survival in the majority of human solid tumours. Thus spatiotemporal MDSC infiltration may have clinical implications in tumour progression.

Aberrant function of myeloid-derived suppressor cells (MDSCs) in experimental colitis and in inflammatory bowel disease (IBD) immune responses

Background and aims: Myeloid-derived suppressor cells (MDSCs) encompass a novel population of suppressor cells and a potential candidate for cell-based therapies in inflammatory diseases. Herein, we investigated their immunomodulatory properties in experimental inflammatory colitis and T cell-mediated immune responses in inflammatory bowel disease (IBD) patients. Methods: MDSCs (defined as CD14−HLA−DR−/lowCD33+CD15+) numbers were determined in peripheral blood (PB) from IBD patients. PB MDSC function was assessed in vitro. Experimental colitis was induced upon 2,4,6-trinitrobenzene sulfonic acid (TNBS) treatment and MDSCs were characterized by flow cytometry. The in vivo suppressive potential of bone marrow (BM)-derived MDSCs (BM-MDSCs) was tested by using both depleting and adoptive transfer strategies. Results: MDSCs were enriched in the periphery of IBD patients during active disease. TNBS colitis induced amplification of MDSCs, particularly of the granulocytic (Ly6G+) subset during the effector phase of disease. Of interest, BM-MDSCs potently suppressed CD4+ T cell responses under steady state but failed to control colitis-associated immune responses in vivo. Mechanistically, under the colonic inflammatory milieu MDSCs switched phenotype (decreased proportion of Gr1high and increased numbers of Gr1low) and downregulated CCAAT/enhancer-binding protein beta (CEBPβ) expression, a critical transcription factor for the suppressive function of MDSCs. In accordance with the murine data, human CD33 + CD15+ MDSCs from peripheral blood of IBD patients not only failed to suppress autologous T cell responses but instead enhanced T cell proliferation in vitro. Conclusions: Our findings demonstrate an aberrant function of MDSCs in experimental inflammatory colitis and in IBD-associated immune responses in vitro. Delineation of the mechanisms that underlie the loss of MDSCs function in IBD may provide novel therapeutic targets.

Abstract P4-12-05: Extracellular vesicles from young women's and postpartum breast cancer display unique proteomic content, alter breast cancer aggressive behavior, and influence immune cell function

Abstract Background: Young women's breast cancer[YWBC] affects 27,000 US women age ≤45 annually. Half of these cancers occur within 5-10 years of a prior childbirth, a postpartum breast cancer[PPBC], incurring a 3 fold increased risk for metastasis and death. Recently, extracellular vesicles[EV] have been identified in human circulation, released from cancer cells, that have paracrine and autocrine effects, alter the tumor microenvironment and establish metastatic niches. EVs isolated from breast cancer lines increase proliferation and invasion of other breast cancer cells in vitro. However, the impact of EVs isolated from primary breast cancer patients on tumor invasion, metastasis and their role in tumor immune suppression is largely unknown. We hypothesized that EVs from YWBC/PPBC patients may contain unique pro-metastatic cargo, influence aggressive breast cancer cell behavior and may demonstrate the ability to alter immune cell function. Method: We isolated EVs using size-exclusion chromatography [SEC] from the plasma of 10 unaffected young women and 20 YWBC patients balanced for parity, age, subtype and stage. We compared the breast cancer-specific EV proteins within various clinical groups of YWBC and PPBC to identify significant proteomic differences by parity, sub-type, stage, and disease recurrence. We determined the functional impact of these EVs on tumor cell motility and proliferation, and analyzed the effect of breast cancer derived EVs on immune cell phenotype, function, and T cell proliferation assays. Results: Of the 582 proteins, 22 proteins are significantly increased in the EVs of YWBC compared to unaffected donors. The protein set includes breast cancer antigens [MUC 1, 2, 5b], transcriptional regulators [Myc target protein], enzymes [catalase, MMP inhibitor 1], and signaling molecules [Annexin 1, latent TGFb binding protein 1], among others. Several identified proteins specifically track with those YWBC cases with subsequent metastases. Furthermore, 8 unique proteins track with PPBC, including cartilage oligomeric matrix protein, a novel breast cancer biomarker that correlates with increased invasiveness, and decreased recurrence-free survival. EVs isolated from the plasma of newly diagnosed YWBC increase breast cancer invasion and EVs derived from breast cancer are engulfed by the majority of monocytic immune cells, including dendritic cells, classical and activated monocytes, but not by lymphocytes. Specifically, CD14+ monocytic myeloid derived suppressor cells engulfed the EVs while the CD15+ granulocytic subset did not. Once engulfed, phenotypic changes occurr in the EV containing monocytes and a significantly reduction in T cell stimulation in standard mixed-lymphocyte reactions is observed. Conclusion: EVs isolated from YWBC & PPBC cases have unique protein content and increase breast cancer invasiveness, which suggests potential mechanistic roles for EVs as increasing metastatic risk and provides novel candidate biomarkers. We identified an immunomodulatory effect of breast cancer EVs on human monocytes that may contribute to immunosuppression in breast cancer and a role for EVs as directly modulating the host and tumor microenvironment. Citation Format: Borges VF, Jordan KR, Hall JK, Schedin T, Hansen K, Schedin P. Extracellular vesicles from young women's and postpartum breast cancer display unique proteomic content, alter breast cancer aggressive behavior, and influence immune cell function [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-05.