Myeloid-derived Suppressor Research Articles

Abstract A54: Transient depletion of MDSCs and Tregs as an effective immunotherapy against triple-negative breast cancer (TNBC)

Abstract Background: Checkpoint inhibitors (CPI) have revolutionized the field of cancer immunotherapy. However, CPIs have shown only modest efficacy in the clinical trials for TNBC, which could be attributed to the presence of immunosuppressive cells—both myeloid-derived suppressor (MDSCs) and T regulatory (Treg) cells—in the tumor microenvironment (TME). We hypothesize that transient depletion of Tregs and MDSCs along with the administration of checkpoint inhibitors would markedly reduce immunosuppressive signals to the effector arm of the immune system and thereby lead to a more robust antitumor response, causing tumor regression and a better disease outcome. To target Treg/MDSCs cells, we have developed two diphtheria-toxin based fusion protein toxins and are currently evaluating the activity of these molecules both as monotherapies and in combination with CPIs. Methods: To target MDSCs and TNBC tumor cells, we genetically constructed, expressed, and purified a diphtheria toxin-based fusion protein, s-DAB389mIL-4 that targets the IL-4 receptor (IL-4R) on these cell populations. This fusion protein toxin was tested in vitro against murine TNBC 4T1 cells and in vivo in a syngeneic murine adenocarcinoma model both as a monotherapy and in combination with s-DABIL-2(V6A), which targets Tregs cells through high- and intermediate-affinity IL-2 receptors. Results: We found that s-DAB389mIL-4 is highly potent against 4T1 cells in vitro (IC50 ranging from 10 pM to ~3 nM), and adversely affects 4T1 cell survival, proliferation, invasion, and migratory abilities. Recombinant IL-4 and anti-IL-4 antibody block the cytotoxic action of s-DAB389mIL-4, confirming that the fusion protein’s activity is mediated through the IL-4R. s-DAB389mIL-4 treatment in a 4T1 cell-based murine adenocarcinoma model results in a significant reduction of (a) tumor volume, (b) MDSCs, and (c) 4T1 metastasis to the lung. Sequential combination therapy with both s-DABIL-4 and s-DABIL-2(V6A) resulted in (1) reduction in both tumor volume and weight, (2) transient depletion of activated Tregs, and (3) increased infiltration of T-effector cells in the TME. NanoString analysis of RNA isolated from tumor tissues treated with these two fusion protein toxins showed enrichment of those gene signatures, which enhance the infiltration of antitumor immune cells in the TME, and concomitant inhibition of those processes, which lead to tumor growth and metastasis. Conclusions: These findings suggest that s-DABmIL-4 both as a monotherapy and in combination with s-DABIL-2(V6A) results in transient reduction of both MDSCs and Treg. These observations suggest that these novel fusion protein toxins may serve as an effective immunotherapeutic regimen for the treatment of TNBC. Based upon these results, we are currently testing these fusion protein toxins in combination with checkpoint blockade therapy. Citation Format: Sadiya Parveen, Sumit Siddharth, Laurene Cheung, John R. Murphy, Dipali Sharma, William R. Bishai. Transient depletion of MDSCs and Tregs as an effective immunotherapy against triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A54.

Interim results from a phase Ib/II study of pepinemab in combination with avelumab in advanced NSCLC patients following progression on prior systemic and/or anti-PDx therapies.

75 Background: Despite progress of immune checkpoint therapies, many cases of non-small cell lung cancer (NSCLC) are refractory or acquire resistance to current therapies. Antibody blockade of semaphorin 4D (SEMA4D, CD100) can overcome resistance mechanisms of immune exclusion and myeloid suppression. Importantly, combinations of anti-SEMA4D with various immunotherapies enhanced T cell infiltration and activity, as well as durable tumor regression in preclinical models. Pepinemab (VX15/2503) is a first-in-class humanized monoclonal antibody targeting SEMA4D. Methods: The CLASSICAL-Lung clinical trial (NCT03268057) evaluates the combination of pepinemab with anti-PD-L1 antibody avelumab to couple beneficial modifications of the immune microenvironment via pepinemab with immune activation via checkpoint inhibition. This ongoing study evaluates the safety, tolerability and efficacy of the combination in patients with advanced (stage IIIB/IV) NSCLC, including immunotherapy-naïve (ION) patients and patients whose tumors progressed during or following immunotherapy (IOF). Results: The combination was well tolerated with no major safety signals identified. Among 29 evaluable IOF patients, two experienced confirmed partial response (PR) with 63% and 52% tumor reduction on study following acquired resistance to prior treatment with pembrolizumab, 15 additional patients experienced stable disease, and at least 5 patients with durable clinical benefit of ≥ 23 weeks. Among 21 evaluable ION patients, 5 experienced PR, clinical benefit ≥ 1 year was observed in 3 patients, and Disease Control Rate was 81%. Analysis of pre- and on-treatment biopsies demonstrated increased CD8+ T cell density correlating with response, reduction or elimination of tumor in 11/13 biopsies from subjects with PR or SD. Conclusions: Interim analysis suggests the combination of pepinemab plus avelumab is well tolerated and shows initial clinical signals of antitumor activity. Updated clinical response data (minimum of 6 mo. follow-up), as well as additional immunophenotyping of both inflammatory and suppressive myeloid cells will be presented. Clinical trial information: NCT03268057.

New drugs approved for acute myeloid leukaemia in 2018.

Acute myeloid leukaemia (AML) is a haematopoietic stem cell disorder, that is characterized by the clonal expansion of myeloid blasts and suppression of normal haematopoiesis. The 3 + 7 regimen is the backbone of standard first-line induction therapy among young/fit patients. However, in elderly and/or unfit patients with newly diagnosed AML, who cannot receive intensive chemotherapy, low-dose cytarabine or hypomethylating agents (azacitidine or decitabine) are the treatment options, which generally cannot induce durable responses. Among young/fit patients, for high-risk disease in first remission, or in cases with relapsed/refractory AML, allogeneic stem cell transplantation should be performed when complete remission is achieved. However, since AML is primarily a disease of the elderly, neither intensive chemotherapy nor allogeneic stem cell transplantation can be generally tolerated in most cases. There is clearly a need for new treatment options in elderly and young/unfit patients who cannot receive intensive chemotherapy. The discovery of novel molecular genetic markers (e.g. FMS-like tyrosine kinase 3, isocitrate dehydrogenase 1 and 2) resulted in the development of new therapeutic options in AML. This review mainly focuses on 4 targeted therapy agents; glasdegib and venetoclax used in combination treatment with low-dose cytarabine or hypomethylating agents among newly diagnosed cases with AML; and ivosidenib and gilteritinib as monotherapy in the treatment of relapsed/refractory AML, which were all approved by the US Food and Drug Administration in 2018.

5-Androstenediol prevents radiation injury in mice by promoting NF-κB signaling and inhibiting AIM2 inflammasome activation

In the present study, the therapeutic effects of 5-androstenediol on radiation-induced myeloid suppression and tissue damage in mice and the possible mechanism were explored. The mice were subjected to whole-body irradiation, and 5-androstenediol was administered subcutaneously at different times and doses. The evaluation of the survival rate showed that the administration of 5-androstenediol every three days post-irradiation was the most effective in decreasing the death of the mice. Additionally, 5-androstenediol dose-dependently reduced the death caused by 9 Gy radiation. The pharmacological mechanism was investigated by blood analysis, western blot analysis, immunofluorescence and immunohistochemistry. 5-Androstenediol significantly ameliorated myeloid suppression, as demonstrated by elevated levels of total white blood cells, including neutrophils and platelets, in the peripheral blood. By H&E staining, we found that radiation-induced myeloid suppression in the bone marrow and spleen, as well as tissue damage in the lung and colon, was significantly ameliorated by treatment with 5-androstenediol. Immunohistochemistry showed elevated phosphorylation of p65 in the bone marrow and spleen, indicating the activation of NF-κB signaling. Moreover, 5-androstenediol markedly hampered the radiation-induced activation of caspase-1 and GSDMD in the colon by decreasing the interaction between AIM2 and ASC. Taken together, our results suggest that, by promoting NF-κB signaling and inhibiting inflammasome-mediated pyroptosis, 5-androstenediol can be used as a radioprotective drug.

Antiretroviral therapy partially improves the abnormalities of dendritic cells and lymphoid and myeloid regulatory populations in recently infected HIV patients

This study aimed to evaluate the effects of antiretroviral therapy on plasmacytoid (pDC) and myeloid (mDC) dendritic cells as well as regulatory T (Treg) and myeloid-derived suppressor (MDSC) cells in HIV-infected patients. Forty-five HIV-infected patients (20 of them with detectable HIV load −10 recently infected and 10 chronically infected patients-, at baseline and after antiretroviral therapy, and 25 with undetectable viral loads) and 20 healthy controls were studied. The influence of HIV load, bacterial translocation (measured by 16S rDNA and lipopolysaccharide-binding protein) and immune activation markers (interleukin –IL- 6, soluble CD14, activated T cells) was analyzed. The absolute numbers and percentages of pDC and mDC were significantly increased in patients. Patients with detectable viral load exhibited increased intracellular expression of IL-12 by mDCs and interferon -IFN- α by pDCs. Activated population markers were elevated, and the proportion of Tregs was significantly higher in HIV-infected patients. The MDSC percentage was similar in patients and controls, but the intracellular expression of IL-10 was significantly higher in patients. The achievement of undetectable HIV load after therapy did not modify bacterial translocation parameters, but induce an increase in pDCs, mDCs and MDSCs only in recently infected patients. Our data support the importance of early antiretroviral therapy to preserve dendritic and regulatory cell function in HIV-infected individuals.

Abstract 562: Antibodies to Sirpα enhance innate and adaptive immune responses to promote anti-tumor activity

Abstract Targeting the CD47-SIRPα myeloid checkpoint pathway represents a novel therapeutic approach to enhance anti-cancer immunity. CD47 is a widely expressed cell surface protein that functions as a marker of self. Signal regulatory protein-α (SIRPα) is an ITIM-containing inhibitory receptor of CD47 on myeloid cells. Tumor cells up-regulate CD47 expression to evade immune surveillance. Clinical trials targeting CD47 to inhibit SIRPα interaction have shown promising results (N Lakhani et al, 2018 SITC #P335). Unlike CD47, which is expressed ubiquitously, SIRPα has limited expression, mainly on myeloid cells including macrophages, dendritic cells, and neutrophils, and neurons. Targeting SIRPα circumvents the need to overcome the CD47 sink that is necessary for CD47 targeting molecules. Antibodies to SIRPα that bind mouse, human and cynomolgus monkey SIRPα with high affinity, were evaluated for their effects on macrophage function, anti-tumor activity and normal blood cells. Humanized antibody to SIRPα was generated to bind both human SIRPα allele V1 and V2 with high affinity (pM) and cross-react with cynomolgus and mouse SIRPα. Anti-SIRPα antibody in combination with targeted anti-cancer antibodies enhanced antibody-dependent cellular phagocytosis (ADCP) of tumor cell lines by human monocyte derived macrophages. In preclinical xenograft models of SIRPα positive and negative malignant cell lines, administration of anti-SIRPα antibody enhanced anti-tumor activity of rituximab and cetuximab via ADCP. The impact of SIRPα blockade on anti-tumor immunity was assessed in immunocompetent tumor mouse models. SIRPα antibodies enhanced anti-tumor activity of checkpoint inhibitors in syngeneic tumor models. Combination therapy with SIRPα antibodies and checkpoint inhibitors in tumor models showed eradication of tumors, acquired memory immune response upon tumor rechallenge and decreased lung metastasis. The cellular mechanisms driving efficacy include dendritic cell activation, reduction of myeloid suppression and enhancement of T cell effector profile. Exploratory safety and PK/PD profiles of anti-SIRPα antibodies were assessed in cynomolgus monkeys. Antibodies to SIRPα demonstrated a typical antibody PK and complete SIRPα target occupancy. There were no adverse clinical observations, no changes in hematological parameters and no impact on serum chemistries. In summary, anti-SIRPα antibodies combined with targeted anti-cancer antibodies or checkpoint inhibitors integrate innate and adaptive immune responses to promote anti-tumor activity in preclinical models. Together with the favorable safety profile in cynomolgus monkeys, these data support the development of SIRPα antibodies for solid tumors and hematological malignancies. Citation Format: Tracy C. Kuo, Amy Chen, Ons Harrabi, Steven E. Kauder, Emma R. Sangalang, Laura Doyle, Sangeetha Bollini, Bora Han, Janet Sim, Jaume Pons, Hong I. Wan. Antibodies to Sirpα enhance innate and adaptive immune responses to promote anti-tumor 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 562.

Myeloid immunosuppressive state as a predictor of rapidly progressive phenotype and poor survival in advanced non-small cell lung cancer (NSCLC) patients treated with PD-1/PD-L1 inhibitors.

e20594 Background: Immune subpopulations within the tumor microenvironment (TME) play a central role in determining response to checkpoint inhibitors. Myeloid derived suppressor cells, a heterogeneous population of immature myeloid cells, have a predominantly immunosuppressive role by stimulating T regulatory cells. We hypothesize that elevated myeloid-to-lymphocyte measures in the peripheral blood predict for greater numbers of myeloid derived suppressor cells in the TME and worse outcomes. Methods: In advanced NSCLC patients who received immunotherapy between 2010-2018, baseline characteristics collected retrospectively included age, sex, histology, stage, smoking status, ethnicity, PD-L1 expression and tumor genotype. Pre-treatment neutrophil/lymphocyte (NLR) and monocyte/lymphocyte ratios (MLR) were log transformed and analyzed using cox and logistic regression models. Results: Among 219 eligible patients, a high NLR was associated with shorter time-to-treatment-failure (HR 1.38, 95%CI 1.09-1.75, p = 0.008) and poorer OS (HR 1.62, 95%CI 1.23-2.14, p < 0.001), independent of PD-L1 levels. Disproportionate increases in NLR and MLR were highly correlated (Spearman’s rho = 0.78). Further, higher NLR (p = 0.09) or MLR (p = 0.06) tended to associate with best overall response (BOR) to immunotherapy, with higher rates of progressive disease (PD) and lower rates of clinical response. A high NLR (p = 0.01) and MLR (p = 0.02) were associated with a rapidly progressive phenotype defined by PD as the BOR and duration of therapy ≤2 months. This remained significant after adjusting for confounders in a multivariate model (p = 0.03 for NLR and p = 0.03 for MLR). No associations were observed between high myeloid counts and other clinical prognostic factors such as liver metastases. Conclusions: A myeloid immunosuppressive state characterized by a disproportionate increase in peripheral immune myeloid populations is significantly associated with primary refractory disease, rapidly progressive phenotype, and poorer survival. Further investigation into myeloid mediated mechanisms of resistance is warranted.

Landscape of innate and adaptive immunity targets in oesophagogastric adenocarcinoma (OGA).

4063 Background: Anti-PD-1 therapy modestly improves survival in chemorefractory OGA. Combining PD-1 blockade with novel checkpoint inhibitors, T-cell co-stimulatory molecules, or myeloid suppressors could enhance PD-1 inhibition. Herein, we explore the landscape of known targetable immune markers in non-Asian OGA. Methods: OGA patient biopsies were prospectively collected and clinically annotated from 19 UK cancer centres (Oesophageal Cancer Clinical and Molecular Stratification – OCCAMs network). Genomic (WGS) and transcriptomic (bulk-RNA seq) data were generated using Illumina and processed using a validated in-house pipeline (Frankell, Nat Genetics 2019). Gene expression was computed in transcripts per kilobase. Using unsupervised clustering patient clusters were selected according to the expression of gene targets for immune therapy - PD-L1, LAG3, TIM3, TIGIT, ICOS, CCR2, CCR5, CXCR4, and CSF1R. Immune cell infiltration was extrapolated using GSVA gene set enrichment analysis. Results: RNAseq data were available for 251 patients; 96% had operable tumours (Stage I: 6%, II: 63%, III: 22%, IV: 4%). In untreated patients (n = 156) 3 subgroups were identified: immune low (83, 53%) with low level expression of all 9 markers, immune high (14, 9%) with high expression of all or majority of markers and intermediate (59, 38%) with heterogenous marker expression. Clinicopathological variables (sex, age, smoking, tumour location (gastric/GEJ/esophagus) and tumour regression grade) were similarly distributed across subgroups. In a cohort of 114 patients with matched WGS and RNAseq data tumour mutation burden was not different between subgroups. In post-chemotherapy biopsies (n = 95) a similar co-expression pattern was observed. Gene enrichment analysis supported infiltration by cells of innate and adaptive immune system in immune high patients. Neoantigen results, phenotypic immunohistochemistry and optimised survival outcomes according to lymphoid and myeloid target expression will be presented. Conclusions: High level co-expression of immune regulatory targets in OGA patients may limit the efficacy of anti-PD-1 monotherapy. Combination immune directed therapies may be required in this patient group.

Monosomy 7: recent progress

Fifty years after its discovery, the enigma of monosomy 7 (-7) is eventually unraveling. The key to understanding -7 is "haploinsufficiency" mechanism, through which the function of myeloid tumor-suppressor genes is lost via the deletion/mutation of one allele. In this century, powerful tools such as microarray-CGH and next generation sequencing have enabled the search for tumor-suppressor genes on chromosome 7. Five genes (Samd9, Samd9-like (Samd9L), Ezh2, MLL3, and CUX1) have been identified and their myeloid tumor suppression potential has been verified using mouse models. Mice lacking one Samd9L gene developed MDS at an advanced age, whereas mice children harboring a gain-of-function mutation of Samd9 or Samd9L gene suffer from bone marrow failure, which is frequently followed by childhood MDS with -7, suggesting that these tumor-suppressor genes are the key to understanding not only MDS with -7 but also MDS in general. However, lack of Ezh2 and MLL3, which encode epigenetic regulators, contribute to the promotion of the progression of myeloid tumor cells that harbor abnormalities in the p53 or Ras pathways.

The Erythro-Myeloblastic Island (EMBI): A Hematopoietic Niche Balancing Erythropoiesis and Myelopoiesis

Mammalian erythropoiesis has long been established to occur within erythroblastic islands (EBIs), niches where erythroblasts differentiate in close contact with a central macrophage. While it is generally accepted that EBI macrophages play an important role in regulation of erythropoiesis, very little is known about the specific macrophage populations involved in EBI formation, the regulation that occurs within EBIs, or how this niche fits into the broader context of hematopoiesis.We analyzed native EBIs isolated from mouse bone marrow using multispectral imaging flow cytometry (Seu et. al. Front Immunol 2017). Consistent with historical observations, the EBIs were heterogeneous and many contained a number of closely CD11b+ cells in addition to erythroblasts and a central F4/80+ macrophage. Flow cytometry analysis of cells dissociated from native bone marrow EBIs indicated these niches are also enriched 2-3 fold in myeloblasts and granulocytic precursors up to metamyelocytes relative to the total bone marrow while they are depleted of mature granulocytes (bands and segmented cells). Bulk RNAseq of the CD11b+ population isolated from EBIs showed high expression of genes characteristic of the granulocytic lineage (e.g. Elane, Mpo, Gfi1, Cebpe, Camp, and Mmp9), indicating the EBI macrophages may regulate myelopoiesis along with erythropoiesis and that EBIs should really be considered as erythro-myeloblastic islands (EMBIs).To critically document the various hematopoietic cell populations that constitute EMBIs, we used the 10x Genomics Chromium system to obtain single cell gene expression data on ~3,500 total cells from isolated EMBIs along with at least 1,000 sorted cells from each of the 3 major EMBI-associated populations (F4/80+, CD71+, and CD11b+) (Fig 1a, b). The data were analyzed using 10x Genomics' Loupe cell Browser and Iterative Clustering and Guide-gene Selection (ICGS, http://www.AltAnalyze.org, Olsson et. al. Nature 2016). From the ICGS analysis, ~30% of the total EMBI-associated cells were myeloid cells that segregated into at least 3 transcriptionally distinct clusters representing granulocytic progenitors and precursors. As expected, erythroblasts with a progressive maturation pattern made up the bulk (60%) of the EMBI-associated cells, while up to 10% were a heterogeneous population of cells that exhibited expression of macrophage markers such as Csf1R and Irf8, along with genes previously described to characterize resident macrophages, such as Fn1and Fsp1/S100A4 (Fig 1c).In order to investigate the balance of myeloid cells with erythroid cells within the EMBIs, we examined the ratio of CD71+ cells to CD11b+ and how this ratio changes in models of altered granulopoiesis. While the number of myeloid cells at any island varied, the overall ratio of CD11b+ area to CD71+ within the EMBIs was relatively constant at steady state. In three different murine models of anemia of inflammation (AoI), we found that this ratio of CD11b+ to CD71+ cells within the EMBI increases dramatically indicating that the increased granulopoiesis and suppression of erythropoiesis noted in AoI is a result of altered balance of the hematopoiesis within the EMBI unit. Similarly, stimulation of granulopoiesis with GCSF also results in a shift within the EMBIs to CD11b+ myeloid cells and suppression of erythroid cells. Alternatively, in gfi1 KO mice, a model of congenital neutropenia in which granulopoiesis fails at an early stage, the ratio shifts toward CD71+ erythroid cells with paucity of the granulocytic precursors that are typically found at the EMBIs.Taken together, these data indicate that granulocyte progenitors and precursors are specifically associated with EMBI macrophages in the mouse bone marrow. The preferential localization of myeloid precursors within EMBIs suggests this niche is a site for granulopoiesis as well as erythropoiesis and production of these lineages is dynamically regulated within this niche. Our work with multiple murine models of altered granulopoiesis demonstrates that pathological expansion of one of the lineages within this niche may suppress the other and that the interactions within the EMBI could be a useful therapeutic target for AoI. These novel findings significantly broaden our understanding of the role of this hematopoietic niche in the regulated development of lineage committed erythroid and myeloid cells. DisclosuresNo relevant conflicts of interest to declare.

Research progress of immune factors associated with patients discontinuing of tyrosine kinase inhibitor for chronic myeloid leukemia

Tyrosine kinase inhibitor (TKI) therapy has significant improved the survival and prognosis of patients with chronic myeloid leukemia(CML). Long-term therapy of TKI drugs not only has produced a heavy financial burden of patients, but also results in chronic adverse effects. At present, the treatment-free remission (TFR) has been gradually regarded as the new treatment target for patients with CML.The key to recurrence of CML patients who discontinued of TKI is dependent whether the immune system maintains a sustained TFR. In this paper, immune factors associated with discontinuation of TKI for patients with CML, such as natural killer (NK) cells, killer-cell immunoglobulin-like receptor (KIR), proteinase-1 specific cytotoxic T lymphocyte (PR1-CTL), myeloid derived suppressor cells (MDSC), regulatory T cells (Treg), CD86+ plasmacytoid dendritic cells(pDC), L-selectin(CD62L) and soluble CD62L(sCD62L) were reviewed. Key words: Leukemia, myelogenous, chronic, BCR-ABL positive; Tyrosine kinase inhibitor; Drug resistence, neoplasm; Treatment-free remission; Immunity cellular; Discontinuation

Abstract 3362: Mice with a “deletor” phenotype allow high resolution detection of lymphoid leukemia tumor suppressor genes

Abstract Mice that are homozygous for a deficiency allele of the DNA replication factor minichromosome maintenance protein 2 (designated Mcm2def) are born viable and are healthy for the first 2 months of life. Beginning at three months, these mice develop precursor T-cell lymphoblastic leukemia/lymphoma (pre-T LBL). Copy number aberration (CNA) analysis showed that these pre-T LBL samples had 8-14 small (100-1000 kb) interstitial deletions per sample. Remarkably, all mice had two or more deletions that encompassed genes known to be relevant for human pre-T LBL, including Pten, Cdkn1a, Tcf3, and Tcf12. Mice that express a NUP98-HOXD13 (NHD13) transgene develop a wide array of leukemias, most commonly myeloid, less commonly T-cell, and, rarely, B-lineage. To identify myeloid tumor suppressor genes, we crossed the NHD13 transgene onto the Mcm2def background. All Mcm2def:NHD13+ mice developed pre-T LBL by 3 months of age, reflecting the highly penetrant nature of the Mcm2def phenotype. None of the Mcm2def:NHD13+ mice developed myeloid leukemia. Surprisingly, approximately 30% of the Mcm2def:NHD13+ mice developed concurrent B-cell precursor acute lymphoblastic leukemia (BCP-ALL) and pre-T LBL. The thymus was typically infiltrated with pre-T LBL cells, whereas the bone marrow and spleen were infiltrated with BCP-ALL cells, characterized by clonal VDJ rearrangement and CD19 staining. Parenchymal organs (lung, kidney, liver) were variably infiltrated with pre-T LBL, BCP-ALL, or both. CNA analysis showed that the pre-T LBL were characterized by Pten, CDkn1a, Tcf3, and Tcf12 deletions, similar to the Mcm2def pre-T LBL, whereas the BCP-ALL were characterized by homozygous or heterozygous deletions of Pax5 and a 400 kb region encompassing Cebpb and Ptpn1. There were no shared deletions present in both BCP-ALL and pre-T LBL from the same mouse, indicating that the BCP-ALL and pre-T LBL arose independently, and not from a common precursor. The high frequency (5/7 samples) of acquired Pax5 deletions in the BCP-ALL samples serves to validate the model; whereas the finding of Cebpb/Ptpn1 deletions (5/7 samples) suggests an unanticipated role of either Cebpb or Ptpn1 in BCP-ALL. Citation Format: Mianmian Yin, Timour Baslan, Amy Freeland, Steven C. Pruitt, Peter D. Aplan. Mice with a “deletor” phenotype allow high resolution detection of lymphoid leukemia tumor suppressor genes [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 3362.

Abstract 4738: IL-17 induces myeloid-related stimulating factors by stromal cells

Abstract Pancreatic ductal adenocarcinoma (PDA) is one of the most aggressive cancer with a 5-year survival rate of ∼ 8%. An hallmark of PDA is the massive desmoplasia and the complex stromal-tumor interaction, regulated by a pletory of secreted factors. The role of IL-17 and T-helper 17 in cancer progression or anti-tumour immunity remain controversial. To assess the role of this molecule, we crossed genetically engineered mice (GEM) characterized by a spontaneous PDA development, with IL-17 knockout mice (GEM/IL-17 KO). The absence of IL-17 correlated with an increased pancreatic fibrosis, evaluated by second harmonic generation approach. The transcripts and secretome of Cancer Associated Fibroblasts (CAFs), obtained from tumors arose in both WT and IL-17 KO GEM, have been evaluated. More than 60 genes were differently modulated in the CAFs from GEM/IL-17 KO mice. Among them, GM-CSF, G-CSF, M-CSF, CXCL1 and 2 where strongly up-regulated in GEM/WT compared to GEM/IL-17 KO mice and significantly inhibited by the addition of the recombinant cytokine. The absence of those factors paralleled an increased Th1-skewed cytokine pattern released by CAF that affected T cell infiltration and response. Taken together, these results suggest that IL-17 does affect the tumor progression by promoting a CAFs-mediated release of cytokines involved in myeloid cells recruitment and suppression of an anti-tumoral immune response. This feature defines IL-17 as a potential target to shape the tumor microenvironment and favour immunotherapy success. Citation Format: Gianluca Mucciolo, Roberta Curto, Claudia Curcio, Cecilia Roux, Luca Vannucci, Francesco Novelli, Paola Cappello. IL-17 induces myeloid-related stimulating factors by stromal cells [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 4738.

Discovery of Blood Transcriptional Endotypes in Women with Pelvic Inflammatory Disease.

Sexually transmitted infections with Chlamydia trachomatis and/or Neisseria gonorrhoeae and rates of pelvic inflammatory disease (PID) in women continue to rise, with reinfection being common because of poor adaptive immunity. Diagnosis remains imprecise, and pathogenesis data are derived primarily from monoinfection of mice with C. trachomatis or N. gonorrhoeae By comparing blood mRNA responses of women with C. trachomatis- and/or N. gonorrhoeae-induced PID and histologic endometritis with those from women with C. trachomatis and/or N. gonorrhoeae infection limited to their cervix and asymptomatic uninfected women determined via microarray, we discovered important pathogenic mechanisms in PID and response differences that provide a pathway to biomarker discovery. Women with N. gonorrhoeae- and/or C. trachomatis-induced PID exhibit overexpression of myeloid cell genes and suppression of protein synthesis, mitochondrial oxidative phosphorylation, and T cell-specific genes. Coinfected women exhibited the greatest activation of cell death pathways and suppression of responses essential for adaptive immunity. Women solely infected with C. trachomatis expressed elevated levels of type I and type II IFN genes, and enhanced type I IFN-induced chemokines in cervical secretions were associated with ascension of C. trachomatis to the endometrium. Blood microarrays reveal discrete pathobiological endotypes in women with PID that are driven by pathogen invasion of the upper genital tract.

Contribution to Tumor Angiogenesis From Innate Immune Cells Within the Tumor Microenvironment: Implications for Immunotherapy.

The critical role of angiogenesis in promoting tumor growth and metastasis is strongly established. However, tumors show considerable variation in angiogenic characteristics and in their sensitivity to antiangiogenic therapy. Tumor angiogenesis involves not only cancer cells but also various tumor-associated leukocytes (TALs) and stromal cells. TALs produce chemokines, cytokines, proteases, structural proteins, and microvescicles. Vascular endothelial growth factor (VEGF) and inflammatory chemokines are not only major proangiogenic factors but are also immune modulators, which increase angiogenesis and lead to immune suppression. In our review, we discuss the regulation of angiogenesis by innate immune cells in the tumor microenvironment, specific features, and roles of major players: macrophages, neutrophils, myeloid-derived suppressor and dendritic cells, mast cells, γδT cells, innate lymphoid cells, and natural killer cells. Anti-VEGF or anti-inflammatory drugs could balance an immunosuppressive microenvironment to an immune permissive one. Anti-VEGF as well as anti-inflammatory drugs could therefore represent partners for combinations with immune checkpoint inhibitors, enhancing the effects of immune therapy.

Myeloid-deprived suppressor cell mediated the prognostic value of platelet-to-lymphocyte ratio for advanced hepatocellular carcinoma patients.

331 Background: Myeloid Deprived Suppressor Cell (MDSC) has been recoganized as a promising target for hepatocellular carcinoma (HCC). However, targeted therapy on MDSC failed to display convincing efficacy. Optimization of patient selection to find the most potential beneficiaries might be a solution to this issue. In the present study, we aimed to identify clinical parameters relevant to MDSC level in HCC patients for future MDSC targeted therapy. Methods: In the present study, a series of 55 HCC patients (prospective group) and 20 healthy donors were analyzed investigating frequencies of MDSC in peripheral blood mononuclear cells (PBMC). Results: As a result, we found that MDSC level was increased in HCC patients compared to healthy donors (10.33% vs 1.54%, p< 0.0001). The monocytes (r2= 0.2875, p< 0.0001), neutrophils (r2= 0.3630, p< 0.0001) and platelet counts (r2= 0.0828, p= 0.0331) in circulation was positively associated with MDSC level. Then, the prognostic value of the above predictors was determined in a retrospective database of 243 HCC patients (retrospective group). The baseline characteristics of prospective and retrospective group were similar. Platelet-to-lymphocyte ratio (PLR) were confirmed to be an independent predictor for OS ( p= 0.003) with the rest parameters presented negative results. Then, advanced HCC patients were divided into two groups based on PLR value ≤111.23 or > 111.23 according to ROC analysis. Patients with low PLR presented higher 3-month survival rate (57.6% vs 37.6%) compared with patients with high PLR. PLR was associated with aggressive behavior of malignancies, such as distant metastasis and portal vein thrombosis. Conclusions: In summary, the present study firstly indentified blood platelet counts was a predictor of MDSC level in PBMC for HCC patients. And, patients with higher PLR might be the optimal patient subgroup for MDSC targeted therapy.

Abstract B010: Antitumor cellular immune response elicited by Toca 511 and Toca FC therapy in preclinical and clinical studies

Abstract Toca 511 (vocimagene amiretrorepvec), in combination with Toca FC (5-FC; flucytosine extended-release tablets), is an investigational combination product currently under development for the treatment of high-grade glioma (HGG) and other solid tumors. Toca 511 is a gamma-retroviral replicating vector (RRV) delivering a cytosine deaminase transgene to infected cells to convert antifungal drug 5-fluorocytosine (5-FC) into antineoplastic drug 5-fluorouracil (5-FU). Toca 511 can be administered by multiple routes; selectively infects, spreads, and persists in cancer cells; and through multiple mechanisms of action can elicit an antitumor immune response. Treatment directly kills infected cancer cells. Diffusible 5-FU also kills neighboring susceptible cells that contribute to the immune-suppressed tumor microenvironment, especially myeloid immune suppressor cells. After multiple cycles of 5-FC, treated animals that clear tumor are resistant to tumor rechallenge. Adoptive transfer recipients of splenocytes from animals that previously cleared their tumor through treatment with Toca 511 and 5-FC experience a significant survival benefit compared to animals receiving spleen cells from naïve donors. Toca 511 and Toca FC have been administered to 126 recurrent high-grade glioma (rHGG) patients in three phase I studies (NCT01156584, NCT01470794, NCT01985256), and a phase 2/3 trial (Toca 5) is ongoing (NCT02414165). Toca 511 plus Toca FC has been well tolerated in these patients. In the clinical study presented, Toca 511 is injected into resection cavity walls at time of tumor resection, and followed with multiple courses of Toca FC. In a subset of phase I patients that mimic the phase 2/3 rHGG enrollment criteria, there were 3 complete responses and 2 partial responses out of 24 patients observed. The median duration of response is 26.7 months. These responders have an overall survival range from 24.0+ to 42.6+ months and ongoing. Data are consistent with induction of antitumor immune responses after Toca FC administration. Changes in peripheral immune populations as well as interrogation of immunogenic biomarkers in responding compared to nonresponding patients will be presented. Citation Format: Tiffany T. Montellano, Derek Ostertag, Daniel J. Hogan, Oscar R. Diago, Dawn Gammon, Ali Haghighi, William Accomando, Leah Mitchell, Asha Das, Harry Gruber, Douglas J. Jolly. Antitumor cellular immune response elicited by Toca 511 and Toca FC therapy in preclinical and clinical studies [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B010.

髓源性抑制细胞在结直肠癌复发转移中的研究进展

髓源性抑制细胞在结直肠癌复发转移中的研究进展

Advances in the relation between myeloid derived suppre-ssor cells and digestive system tumors

Myeloid derived suppressor cell (MDSC) is a kind of myogenic stem cells that are induced by tumor-derived cytokines. MDSCs not only have their own immunosuppressive effects, but also can mediate the immunosuppressive effects of T lymphocytes through different mechanisms. Recent studies have shown that MDSCs involved in tumor immune escape, immune tolerance as well as other pathological processes, and played an important role in promoting the generation and development of tumors. The advances of the generation, immunosuppressive effects of MDSCs and their relation with digestive system tumors were summarized in this paper, which would provide evidences for the clinical use of MDSCs in treating digestive system tumors. Key words: Digestive system neoplasms; Myeloid derived suppressor cells; Immunodepression; Target

Strategies to Improve Vaccine Efficacy against Tuberculosis by Targeting Innate Immunity.

The global tuberculosis epidemic is the most common cause of death after infectious disease worldwide. Increasing numbers of infections with multi- and extensively drug-resistant variants of the Mycobacterium tuberculosis complex, resistant even to newly discovered and last resort antibiotics, highlight the urgent need for an efficient vaccine. The protective efficacy to pulmonary tuberculosis in adults of the only currently available vaccine, M. bovis BCG, is unsatisfactory and geographically diverse. More importantly, recent clinical studies on new vaccine candidates did not prove to be better than BCG, yet. Here, we propose and discuss novel strategies to improve efficacy of existing anti-tuberculosis vaccines. Modulation of innate immune responses upon vaccination already provided promising results in animal models of tuberculosis. For instance, neutrophils have been shown to influence vaccine efficacy, both, positively and negatively, and stimulate specific antibody secretion. Modulating immune regulatory properties after vaccination such as induction of different types of innate immune cell death, myeloid-derived suppressor or regulatory T cells, production of anti-inflammatory cytokines such as IL-10 may have beneficial effects on protection efficacy. Incorporation of lipid antigens presented via CD1 molecules to T cells have been discussed as a way to enhance vaccine efficacy. Finally, concepts of dendritic cell-based immunotherapies or training the innate immune memory may be exploitable for future vaccination strategies against tuberculosis. In this review, we put a spotlight on host immune networks as potential targets to boost protection by old and new tuberculosis vaccines.