Monocytic Myeloid-derived Suppressor Cells Research Articles

Kras-driven intratumoral heterogeneity triggers infiltration of M2 polarized macrophages via the circHIPK3/PTK2 immunosuppressive circuit

Intratumoral heterogeneity in lung cancer is essential for evasion of immune surveillance by tumor cells and establishment of immunosuppression. Gathering data reveal that circular RNAs (circRNAs), play a role in the pathogenesis and progression of lung cancer. Particularly Kras-driven circRNA signaling triggers infiltration of myeloid-associated tumor macrophages in lung tumor microenvironment thus establishing immune deregulation, and immunosuppression but the exact pathogenic mechanism is still unknown. In this study, we investigate the role of oncogenic Kras signaling in circRNA-related immunosuppression and its involvement in tumoral chemoresistance. The expression pattern of circRNAs HIPK3 and PTK2 was determined using quantitative polymerase chain reaction (qPCR) in lung cancer patient samples and cell lines. Apoptosis was analyzed by Annexin V/PI staining and FACS detection. M2 macrophage polarization and MDSC subset analysis (Gr1−/CD11b−, Gr1−/CD11b+) were determined by flow cytometry. Tumor growth and metastatic potential were determined in vivo in C57BL/6 mice. Findings reveal intra-epithelial CD163+/CD206+ M2 macrophages to drive Kras immunosuppressive chemoresistance through myeloid differentiation. In particular, monocytic MDSC subsets Gr1−/CD11b−, Gr1−/CD11b+ triggered an M2-dependent immune response, creating an immunosuppressive tumor-promoting network via circHIPK3/PTK2 enrichment. Specifically, upregulation of exosomal cicHIPK3/PTK2 expression prompted Kras-driven intratumoral heterogeneity and guided lymph node metastasis in C57BL/6 mice. Consequent co-inhibition of circPTK2/M2 macrophage signaling suppressed lung tumor growth along with metastatic potential and prolonged survival in vivo. Taken together, these results demonstrate the key role of myeloid-associated macrophages in sustaining lung immunosuppressive neoplasia through circRNA regulation and represent a potential therapeutic target for clinical intervention in metastatic lung cancer.

Estradiol correlates with the accumulation of Monocytic Myeloid-Derived Suppressor Cells in Pre-term birth: A possible explanation of immune suppression in pre-term babies

Synergistic interplay of immune endocrine interaction is prerequisite for an effective maternal fetal tolerance. Pre-term birth (PTB) may be a consequence of altered immune-endocrine crosstalk during third trimester resulting in early breakdown of this tolerance. Myeloid derived suppressor cells (MDSCs), a heterogenous population of immature immune cells are increased in pregnant women and healthy newborns, but their role in PTB still remains obscure. We now report that granulocytic MDSCs (G-MDSCs) is decreased in women delivering prematurely, suggesting their potential role in maintaining maternal fetal tolerance. Interestingly, in contrast statistically significant increase in MDSCs and monocytic MDSCs (M-MDSCs) along with positive correlation with cord serum estradiol (E2), and overexpressed ER-α in placental tissue suggested E2 mediated accumulation of M-MDSCs in PTB babies. MDSCs mediated immune suppression is accompanied with subsequent decline in total T cells and its subtypes: Th and Tc in PTB babies, which signifies their potential contribution towards the impaired immune system of PTB babies.

Age-related expansion and increased osteoclastogenic potential of myeloid-derived suppressor cells

Aging is associated with excessive bone loss that is not counteracted with the development of new bone. However, the mechanisms underlying age-related bone loss are not completely clear. Myeloid-derived suppressor cells (MDSCs) are a population of heterogenous immature myeloid cells with immunosuppressive functions that are known to stimulate tumor-induced bone lysis. In this study, we investigated the association of MDSCs and age-related bone loss in mice. Our results shown that aging increased the accumulation of MDSCs in the bone marrow and spleen, while in the meantime potentiated the osteoclastogenic activity of the CD11b+Ly6ChiLy6G+ monocytic subpopulation of MDSCs. In addition, CD11b+Ly6ChiLy6G+ MDSCs from old mice exhibited increased expression of c-fms compared to young mice, and were more sensitive to RANKL-induced osteoclast gene expression. On the other hand, old mice showed elevated production of IL-6 and receptor activator of nuclear factor kappa-B ligand (RANKL) in the circulation. Furthermore, IL-6 and RANKL were able to induce the proliferation of CD11b+Ly6ChiLy6G+ MDSCs and up-regulate c-fms expression. Moreover, CD11b+Ly6ChiLy6G+ MDSCs obtained from old mice showed increased antigen-specific T cell suppressive function, pStat3 expression, and cytokine production in response to inflammatory stimulation, compared to those cells obtained from young mice. Our findings suggest that CD11b+Ly6ChiLy6G+ MDSCs are a source of osteoclast precursors that together with the presence of persistent, low-grade inflammation, contribute to age-associated bone loss in mice.

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.

Abstract 507: Association of circulating myeloid derived suppressor cells with systemic lymphopenia following chemoradiotherapy in glioblastoma

Abstract Systemic lymphopenia is common among glioblastoma (GBM) patients after chemoradiotherapy and is observed up to six months to 1 year after irradiation. Systemic lymphopenia is associated with a worse survival outcome in GBM. To delineate the underlying mechanisms of lymphopenia in GBM, we prospectively evaluated peripheral blood of GBM patients treated with standard radiation therapy (RT) and concurrent temozolomide as well as conducted in vivo experiments using a syngeneic murine GBM model. Among 20 patients prospectively evaluated, 10 patients (50%) developed lymphopenia and the other 10 did not. The RNA sequencing analysis of the peripheral blood mononuclear cell (PBMC) showed an elevated level of myeloid-derived suppressor cells (MDSCs) regulatory genes including Arg-1 in lymphopenic patients compared to non-lymphopenic patients after chemoradiotherapy. The single-cell RNA sequencing (scRNA-Seq) analysis of two selected phenotypical patients also demonstrated that a severe lymphopenic patient had elevated levels of two types of monocytic MDSCs (M-MDSCs) after RT compared to a non-lymphopenic patient. Immunophenotyping analysis of the PBMCs using flow cytometry confirmed reductions of CD4 and CD8 T cells as well as increased polymorphonuclear MDSCs (PMN-MDSCs) and M-MDSCs in lymphopenic patients compared to non-lymphopenic patients. The in vitro T cell proliferation and functional assays showed that MDSCs from lymphopenic patients exhibited were more suppressive compared to MDSCs from non-lymphopenic patients. Using a syngeneic orthotopic mouse (C57BL/6) GBM (GL261) model, we demonstrated that fractionated RT (2 Gy/day x 5) reduced CD4/CD8 cells and increased MDSCs compared to sham irradiated mice. The MDSCs from the irradiated mice also had increased Arg-1 expression. The addition of Arg-1 inhibitor (Arg1i) or phosphodiesterase type 5 inhibitor (PDE5i) to RT blocked the radiation-induced increase of MDSCs and reduction of CD4/CD8 cells. The combination of either Arg1i or PDE5i also enhanced the survival of mice with orthotopic tumors when compared to mice treated with RT alone or drug alone. In conclusion, we found that RT can induce an increase in circulating MDSCs in both patients and mice and the resulting circulating MDSCs can suppress T-cell proliferation and function. Inhibition of MDSCs using either Arg1i or PDE5i during RT may prevent systemic lymphopenia and affect disease control, which should warrant further investigation in clinical trials. Citation Format: Subhajit Ghosh, Matthew Inkman, Jin Zhang, Sukrutha Thotala, Ekaterina Tikhonova, Natalia Miheecheva, Felix Frenkel, Ravshan Ataullakhanov, Xiaowei Wang, Dennis Hallahan, Jiayi Huang, Dinesh Thotala. Association of circulating myeloid derived suppressor cells with systemic lymphopenia following chemoradiotherapy in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 507.

WDR5-H3K4me3 epigenetic axis regulates OPN expression to compensate PD-L1 function to promote pancreatic cancer immune escape

BackgroundDespite PD-L1 (Programmed death receptor ligand-1) expression on tumor cells and cytotoxic T lymphocytes tumor infiltration in the tumor microenvironment, human pancreatic cancer stands out as one of the human...

Abstract 1793: Regional administration of class C CpG Oligodeoxynucleotides results in superior intrahepatic TLR9 activation and immunomodulation compared to systemic infusion

Abstract CpG oligodeoxynucleotides (ODNs) are TLR9 agonists (TLR9As) that stimulate pDC and B cells. Yet, multiple other cell types in the liver express TLR9. The effect of TLR9A in reshaping the tumor microenvironment (TME), particularly in the myeloid-derived suppressor cells (MDSC) compartment, is yet to be determined. Clinical success of TLR9As has been limited by toxicity when given systemically and delivery limitations when administered by direct needle injection. Here, we hypothesized that regional intra-vascular infusion of TRL9As would reprogram the liver MDSC compartment to enable immune control of liver metastases (LM). In this study, we evaluated the effect of class C ODN-2395 as TLR9A in inhibiting LM progression and its impact on the liver MDSC population. C57/BL6 mice were challenged with 2.5e6 MC38-CEA-Luc cells via intra-splenic route. After a week, mice were treated with 1, 3, 10 or 30 µg ODN2395 via PV or IV (30 µg). Bioluminescence was measured at 24 and 48 hrs post-ODN administration. CD45+ cells were isolated, and FACS analysis was performed to quantify MDSCs, monocytic MDSCs (M-MDSC), and M1-macrophage subsets, along with downstream signaling. We found that 30 µg ODN2395 delivered via PV compared to IV reduced tumor burden at 24 hrs and persisted up to 48 hrs. Also, 30 µg ODN2395 infused via PV was optimal in controlling MDSC, M-MDSC cells and polarized CD11b+F4/80+ monocytic cells towards pro-inflammatory/anti-tumorigenic M1 macrophage. Using an NFκB-dependent soluble alkaline phosphatase assay (SEAP), we determined that ODN2395 dose-dependently enhanced NFκB transcription factor activity (p<0.001). Western Blot data of tumor lysates show that ODN delivery by PV increased NFκB (pP65) activity and production of IL-6, significantly relative to IV. Overall, our data suggest that the regional delivery of a TLR9A has the potential to provide superior modulation of the TME within the liver. Table:Readout30µg IV30µg PVP valuenBioluminescence-24 h (photon/s)4e71e7<0.0113Bioluminescence-48h (photon/s)7e72e7<0.0513FACSCD11b+Gr1+ cells/CD45+ NPC (MDSC)29.70 %20.75%<0.0113CD11b+LY6C+ (M-MDSC)60.03%38.98%<0.0113CD11b+F4/80+CD38+EGR2-(M1 macrophage)34.82%58.20%<0.0113Western BlottingpNFκB/NFκB (pP65s276/pP65): Fold change0.862.028<0.016IL6/GAPDH Fold change12.387<0.056 Citation Format: Chandra Ghosh, Kara Heatherton, Kyle O'Connell, Jason Laporte, Prajna Guha, David Jaroch, Bryan Cox, Steven C. Katz. Regional administration of class C CpG Oligodeoxynucleotides results in superior intrahepatic TLR9 activation and immunomodulation compared to systemic infusion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1793.

Abstract 1629: IO-202, a first-in-class LILRB4 antagonist antibody, activates dendritic cells and inhibits solid tumor growth in preclinical studies

Abstract LILRB4, also known as ILT3, is an immune inhibitory transmembrane protein found on monocytes and antigen presenting cells, including dendritic cells (DCs). LILRB4 upregulation in DCs induces a tolerogenic phenotype that facilitates the generation of antigen-specific T regulatory cells. LILRB4 is also expressed on acute myeloid leukemia (AML) with monocytic differentiation, in which it promotes T cell suppression and tumor infiltration. IO-202 is a first-in-class LILRB4 antagonist antibody that is being evaluated in a Phase I trial (NCT04372433) for the treatment of AML and chronic myelomonocytic leukemia (CMML). RNA-seq data from TCGA database indicates that LILRB4 expression is upregulated in many solid tumor types. Therefore, the therapeutic potential of IO-202 in solid tumors was investigated in this study. Using computational biology approaches, we found that high LILRB4 expression in solid tumors from TCGA database is associated with macrophage infiltration in the tumor microenvironment. Flow cytometric analysis of cancer patients' blood and tumor samples confirmed LILRB4 expression on tumor-associated macrophages (TAMs) and on monocytic myeloid-derived suppressor cells (M-MDSCs) and DCs in tumor and periphery. These data raised the hypothesis that LILRB4 functions as a myeloid checkpoint and contributes to tumor immune evasion, not only in AML, but also in many solid tumor types. LILRB4 is not present in rodents. As such, the functional activity and anti-tumor efficacy of IO-202 were evaluated using human primary immune cells and immunocompetent LILRB4 transgenic mice, respectively. In healthy donor monocyte-derived DCs, IO-202 treatment promoted DC maturation, activation and an antigen presenting phenotype, as well as enhanced their ability to activate allogeneic T cells. In the radiation therapy (RT)-resistant Lewis lung carcinoma (LLC) syngeneic model, IO-202 in combination with RT resulted in tumor growth inhibition, which was associated with changes in the relative abundance of tumor-infiltrating immune cells, evidenced by a reduction in M-MDSCs and an increase in T cells, along with increased T cell activation. In conclusion, our data suggest that LILRB4 functions as a myeloid checkpoint in multiple cancer types and that IO-202, the first-in-class LILRB4 antagonist antibody, enhances dendritic cell function and T cell activation in vitro and anti-tumor immunity in a solid tumor model in vivo. These data demonstrate the therapeutic potential of IO-202 as a myeloid checkpoint inhibitor for solid tumors. Citation Format: Maria José Costa, Tao Huang, Jing-Tyan Ma, Caroline Bonnans, Azita Tabrizi, Xiaoling C. Liao, Paul Woodard, Benjamin P. Chen, Ching-Cheng Hsu, Mi Deng, Cheng Cheng Zhang, An Song. IO-202, a first-in-class LILRB4 antagonist antibody, activates dendritic cells and inhibits solid tumor growth in preclinical studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1629.

CD73 expression in myeloid-derived suppressor cells is correlated with clinical stages in head and neck squamous cell carcinomas.

BackgroundEcto-5'-nucleotidase (cluster of differentiation 73/CD73) is an ectonucleotidase that is being evaluated as a biomarker for the diagnosis and prognosis of various types of cancer. However, the clinicopathological relationship between CD73 expression in monocytic MDSCs (M-MDSCs) and polymorphonuclear MDSC (PMN-MDSCs) in head and neck squamous cell carcinomas (HNSCCs) is not clear. Understanding the phenotypic and functional characteristics of human CD73+ MDSCs in the tumor microenvironment could help elucidate the roles of these cells in the ontogeny, spread, and treatment of solid cancer.MethodsIn the present study, we first analyzed the expression percentage of human M-MDSCs and PMN-MDSCs subsets circulating in peripheral blood of patients with head and neck tumors originated in nasopharynx, oropharynx, oropharynx and larynx. To identify the correlation between phenotypic characteristics of MDSCs and clinical stages in HNSCC, we extended the study by analyzing the percentage, CD73 phenotype and immunosuppressive function of MDSCs and the correlation with the clinical parameters. Moreover, we compare the functions of both M-MDSCs and PMN-MDSCs blunts T-cell function in an ectonucleotidase-dependent manner.ResultsOur study revealed that PMN-MDSCs were significantly increased in HNSCC patients, contributing to MDSC-mediated T cell immune suppression. Our results indicated that PMN-MDSCs comprised the majority of MDSCs participating in anticancer immunosuppression. The increase in PMN-MDSCs was directly correlated with the clinical stages of HNSCC. Levels of CD73 were increased in PMN-MDSCs and were correlated with the clinical stages of HNSCC. The ectonucleotidase inhibitor adenosine 5'-(α,β-methylene)diphosphate (APCP) decreased its suppression towards T cell proliferation. Ectonucleotidase inhibitors are promising candidates for the treatment of HNSCC.ConclusionsThese studies demonstrate the expansion of PMN-MDSCs correlated with expression of CD73 and increasing clinical stages in HNSCC. These CD73+ PMN-MDSCs contributes to T cell immune suppression activity in HNSCC patients. Using ectonucleotidase inhibitors is a promising rationale for PMN-MDSCs in future clinical development of immunotherapy in human HNSCC cancer.

Abstract 523: Modulation of immune suppressive cells by toll-like 7 agonist DSP-0509 which leads to potentiate anti-tumor activity of radiotherapy

Abstract Toll-like receptors (TLRs) are a family of pattern-recognition receptors that recognize pathogen-associated molecular patterns. TLR7 stimulation in pDCs (plasmacytoid dendritic cell) induces type I interferon, which results in innate immune activation. We previously showed that intravenously injectable DSP-0509 activated anti-tumor immunity in combination with immune checkpoint inhibitors. In this study, we present that DSP-0509 can enhance anti-tumor activity of radiation therapy (RT). RT is generally known to induce not only anti-tumor effector T cells through immunogenic cell death, but also cause immune suppression. We assessed the modulatory activity of DSP-0509 on immune suppressive cells. In CD8+ T cell suppression assay in which CD8+ T cells were cocultured with mMDSC (monocytic myeloid-derived suppressor cell, CD11b+Gr-1low), DSP-0509 restored the proliferation of CD8+ T cell suppressed by mMDSC. In Treg differentiation assay, in which Treg (CD4+CD25+Foxp3+) was differentiated from naïve CD4+ T cell in the presence of TGF-β, DSP-0509 suppressed the Treg differentiation. Treg function was assessed in coculture system, in which proliferation of CTV-labeled (CellTrace™ Violet) CD4+ T cell was suppressed by Treg. DSP-0509 restored the proliferation of CD4+ T cell. As a next step, to confirm a combination effect with RT, DSR-0509 (5 mg/kg, weekly) was administered with RT (5 Gy x 5 consecutive day). The combination administration extended the survival of CT26-bearing mice. The ratio of effector memory T cell (CD8+CD62L-CD127+) in CD8+ T cell was increased after administration of combination of DSP-0509 with RT. ELISpot assay using splenocytes collected from CT26-bearing mice after the administration of combination of DSP-0509 with RT was conducted. As a result, the number of IFNγ secreting cytotoxic T lymphocytes (CTLs) that responded to gp70 peptide was increased in combination of DSP-0509 with RT. When CT26 cells were re-challenged to the mice that completely rejected tumor after combination of DSP-0509 with RT, no tumor growth was observed in all mice. Anti-CD8 antibody treatment prior to re-challenge of CT26 cells cancelled this memory effect. qPCR analysis using mRNA isolated from treated tumor was conducted. RT monotherapy increased the expression of Cd8b1, but addition of DSP-0509 further enhanced the expression of Gzmb and Il12b in tumor. We showed two novel effects of DSP-0509 in this study, 1) modulation of immune suppressive cells and 2) extension of the survival of tumor-bearing mice in combination with RT, which would be explained by the additive CTL activation and memory T cell induction. Taken together, these results supported the hypothesis that combination of DSP-0509 with RT may enhance the anti-tumor immune activity by modulating CTL activity as well as immune suppressive cells. Citation Format: Yosuke Ota, Yasuhiro Nagai, Masashi Goto, Jun Oishi, Setsuko Yamamoto. Modulation of immune suppressive cells by toll-like 7 agonist DSP-0509 which leads to potentiate anti-tumor activity of radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 523.

Abstract 2738: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediates tumor immune evasion in cholangiocarcinoma

Abstract Background and Aims: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a member of the tumor necrosis factor superfamily, is predominantly expressed on immune cells. Although TRAIL biology has garnered considerable interest as a potential anti-cancer strategy, TR agonists have had very limited anti-cancer activity in humans. TRAIL signaling in T cells may also potentially provide an immune checkpoint function as it can inhibit T cell activation and proliferation by interfering with T cell receptor signaling. However, this potential immune checkpoint function of TRAIL has not been examined in cancer biology. Cholangiocarcinoma (CCA), a malignancy of the bile ducts, provides a model to examine the potential immune checkpoint function of TRAIL. Methods: Using a syngeneic, orthotopic murine model of CCA (PMID: 29464042), murine CCA cells (SB cells) that express both TRAIL and TRAIL receptor (TR) were implanted into livers of WT C57BL/6J and Tr−/− mice. Hence, in this model the host immune cells express TRAIL but not the receptor; they would be capable of inducing TRAIL-mediated apoptosis in CCA cells but would be resistant to potential TRAIL-mediated immunosuppression. After 4 weeks of tumor growth, mice were sacrificed and tumor and immune characterization (via flow cytometry) was conducted. Results: Implantation of SB cells into Tr−/− mice result in a significant reduction in tumor volumes compared to WT mice. Tumor-bearing Tr−/− mice had a significant infiltration of cytotoxic T lymphocytes (CTLs) (CD45+CD3+CD8+CD11a+) and enhanced CTL effector function. Moreover, Tr−/− mice tumors had a significant decrease in granulocytic and monocytic myeloid-derived suppressor cell (MDSCs) as well as tumor-associated macrophages (TAMs) (CD45+F4/80+CD11b+CD206+) compared to WT mice tumors. Conclusion: Using a unique syngeneic orthotopic implantation model of murine CCA, we demonstrate that CCA cells expressing TRAIL in a mouse genetically deficient for TR exhibit reduced tumor volumes enhanced CTL infiltration and function, and reduced MDSC and TAM infiltration into the tumors. These data suggest that TRAIL has a potential immune checkpoint function, and targeting TRAIL signaling with consequent augmentation of CTL function maybe a promising therapeutic approach in human cancers. Citation Format: Emilien Loeuillard, Jingchun Yang, Haidong Dong, Gregory J. Gores, Sumera Ilyas. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediates tumor immune evasion in cholangiocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2738.

Abstract 440: Potentiation of EGFR peptide cancer vaccine by an orally bioavailable glutamine antagonist prodrug JHU-083

Abstract Lung cancer is the leading cause of cancer mortality worldwide. More than 85% of lung cancers are non-small cell lung cancer (NSCLC). EGFR mutations occur in 47.9% of Asia-Pacific patients with NSCLC and 19.2% of Western patients. The most common EGFR mutations (>90%) are deletions in exon 19 and/or point mutations in exon 21 (L858R). Th1 helper cellular immunity is critical for immunotherapy-mediated tumor regression. We have previously characterized an MHC-II-restricted EGFR multi-peptide vaccine (two peptides: “SCVRACGADSYEMEEDGVRK” and “VWSYGVTVWELMTFGSKPY”) (EGFR-V) that targets the EGFR protein and decreases EGFR-driven lung tumorigenesis by ~80% in EGFRL858R transgenic mice that were vaccinated before doxycycline-induction of the EGFR protein [1]. However, diminished efficacy was observed when this MHC-II-restricted EGFR multi-peptide vaccine was given two weeks after doxycycline induction of the EGFR protein, suggesting that expression of the EGFR oncoprotein significantly increased the immunosuppressive microenvironment. JHU083, an orally bioavailable glutamine antagonist, has recently been shown to not only inhibit tumor growth but also boost anti-cancer immunity [2]. To determine if JHU083 could potentiate the efficacy of EGFR vaccine in a post-initiation setting, we evaluated in vivo antitumor efficacy of EGFR vaccine combined with JHU083 using an EGFRL858R transgenic mouse model. JHU083 inhibited tumor burden by 31% and EGFR vaccine suppressed tumor burden by 33%, whereas combining JHU083 with anti-EGFR peptide vaccine had an additive effect (54% tumor inhibition). Mechanistically, JHU083 by itself, markedly reduced the immunosuppressive monocytic myeloid-derived suppressor cells (MDSCs) in lung tissues. The combination of JHU083 and the vaccine significantly reduced Tregs in lung tissues. The anti-EGFR vaccine primarily induced expansion of antigen specific antitumor CD4+ effector T cells. Long term administration of JHU-083 did not decrease bodyweight in mice. Together with previous results, these data suggest that JHU083 could be used to reshape the tumor microenvironment toward one that enhances antitumor T cell responses and could further enhance the efficacy of the EGFR anticancer vaccine.

Abstract 1730: Up-regulation of C/EBPα inhibits suppressive activity of myeloid cells and potentiates antitumor response in mice and cancer patients

Abstract Tumor associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC) are widely implicated in the suppression of immune responses in cancer and are associated with negative clinical outcomes. We report that in mouse tumor models, therapeutic up-regulation of the transcriptional factor C/EBPα with small activating RNA (MTL-CEBPA) blocks the suppressive activity of monocytic (M) MDSC and TAM without affecting polymorphonuclear (PMN) MDSC. MTL-CEBPA treatment demonstrated antitumor activity that was dependent on T cells. Combination of MTL-CEBPA and anti-PD1 antibody or with PMN-MDSC targeted therapy resulted in marked antitumor effect. A phase I trial was conducted in 36 patients with advanced hepatocellular carcinoma (HCC). Marked decrease in M-MDSC and the expression of genes and proteins involved in immune suppressive activity of these cells were observed. Combined treatment with MTL-CEBPA and sorafenib resulted in a 27% objective radiological response and three complete responses in patients with virally associated HCC. Tissue biopsies from these patients demonstrated decrease in M2 polarized macrophages within the tumors. Thus, therapeutic up-regulation of C/EBPα inhibited suppressive myeloid cells that resulted in potent antitumor effect in mice and with encouraging clinical response in cancer patients. We are currently recruiting to a multi-centre study of MTL-CEBPA in combination with a PD-1 inhibitor (pembrolizumab) in adult patients with advanced solid tumors (TIMEPOINT - ClinicalTrials.gov Identifier: NCT04105335). Citation Format: Ayumi Hashimoto, Debashis Sarker, Vikash Reebye, Sheba Jarvis, Mikael H. Sodergren, Andrew Kossenkov, Nina Raulf, Jenni Vasara, Pinelopi Andrikakou, Tim Meyer, Kai-Wen Huang, Ruth Plummer, Cheng Ean Chee, Duncan Spalding, Madhava Pai, David J. Pinato, Rohini Sharma, Bristi Basu, Daniel Palmer, Yuk-Ting Ma, Robert Habib, Anna Martirosyan, Naouel Elasri, Adeline Reynaud, John Rossi, Mark Cobbold, Nagy Habib, Dmitry Gabrilovich. Up-regulation of C/EBPα inhibits suppressive activity of myeloid cells and potentiates antitumor response in mice and cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1730.

Abstract LB050: Modulation of innate and adaptive immunity in blood and tumor of patients receiving the SHP2 inhibitor RMC-4630

Abstract RMC-4630 is a potent, selective, orally bioavailable allosteric inhibitor of SHP2, a central node in the RAS signaling pathway. In preclinical models, SHP2 inhibition not only directly inhibited tumor growth through suppression of tumor-intrinsic RAS signaling, but also resulted in transformation of the tumor immune microenvironment, characterized by an increase in CD8+T cell infiltrates and selective depletion of pro-tumorigenic M2 macrophages. In this study, we evaluated pharmacodynamic biomarkers in blood and tumors from patients in the RMC-4630 phase I monotherapy clinical trial (NCT 03634982) by using flow cytometry and immunohistochemistry (IHC). Safety, PK and efficacy data are reported in a separate abstract. Longitudinal analysis of immune cell phenotyping in blood was conducted in 35 patients. There was a trend for lower pre-study monocytic myeloid-derived suppressor cell (mMDSC) to be associated with a better clinical outcome on RMC-4630 therapy. While the proportion of circulating T cell and B cell populations did not change, both blood mMDSC and total monocytes were significantly reduced during RMC-4630 administration. Furthermore, tumor volumes changes, and the proportion of patients with SD versus PD, positively correlated with the ratio of mMDSCs to total monocytes on RMC-4630 treatment. Inhibition of pERK was observed in a subset of patients. Three paired tumor biopsies from efficacy-evaluable patients, including 1 PR, 1 SD and 1 PD, were available for tumor microenvironment analysis by multiplexed-IHC assays. Increase in tumor infiltrating T cells in the tumors of one patient with a PR and another with SD was observed on RMC-4630 therapy. Inhibition of tumor PD-L1 expression and a decrease in M2 macrophages was also observed on treatment in the tumor biopsy of the PR patient. Collectively, the preliminary clinical biomarker data supports the preclinical observations that SHP2 inhibition with RMC-4630 modulates both innate and adaptive anti-tumor immunity. Citation Format: Ariel Yung-Chia Chen, Eric Haura, Jose Pacheco, Marianna Koczywas, Michael Gordon, Susanna Ulahannan, Howard A. Burris, Sai-Hong Ignatius Ou, Judy S. Wang, Jonathan W. Riess, Caroline McCoach, Anna Capasso, Elsa Quintana, Josie Hayes, Richa Dua, Bojena Bitman, Martha Guerra, Hongfang Wang, Xiaolin Wang, Pasi A. Janne. Modulation of innate and adaptive immunity in blood and tumor of patients receiving the SHP2 inhibitor RMC-4630 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB050.

YIV-906 potentiated anti-PD1 action against hepatocellular carcinoma by enhancing adaptive and innate immunity in the tumor microenvironment

YIV-906 (PHY906) is a standardized botanical cancer drug candidate developed with a systems biology approach—inspired by a traditional Chinese herbal formulation, historically used to treat gastrointestinal symptoms including diarrhea, nausea and vomiting. In combination with chemotherapy and/or radiation therapy, preclinical and clinical results suggest that YIV-906 has the potential to prolong survival and improve quality of life for cancer patients. Here, we demonstrated that YIV-906 plus anti-PD1 could eradicate all Hepa 1–6 tumors in all tumor bearing mice. YIV-906 was found to have multiple mechanisms of action to enhance adaptive and innate immunity. In combination, YIV-906 reduced PD1 or counteracted PD-L1 induction caused by anti-PD1 which led to higher T-cell activation gene expression of the tumor. In addition, YIV-906 could reduce immune tolerance by modulating IDO activity and reducing monocytic MDSC of the tumor. The combination of anti-PD1 and YIV-906 generated acute inflammation in the tumor microenvironment with more M1-like macrophages. YIV-906 could potentiate the action of interferon gamma (IFNg) to increase M1-like macrophage polarization while inhibiting IL4 action to decrease M2 macrophage polarization. Flavonoids from YIV-906 were responsible for modulating IDO activity and potentiating IFNg action in M1-like macrophage polarization. In conclusion, YIV-906 could act as an immunomodulator and enhance the innate and adaptive immune response and potentiate anti-tumor activity for immunotherapies to treat cancer.

The Role of Matrix Metalloproteinase-9 in Monocytic Myeloid-Derived Suppressor Cells in Allogeneic Hematopoietic Stem Cell Transplantation

Background: Myeloid-derived suppressor cells (MDSCs) have emerged as a heterogeneic immunoregulatory population that accumulate in large numbers during many pathologic conditions, including cancer, infectious diseases, trauma, and sepsis. Given that MDSCs are an important element of a cellular network regulating immune responses, their recovery early after allogeneic hematopoietic stem cell transplantation (allo-HSCT) seems to be related to regulating graft-versus-host disease (GVHD) and/or immune reconstitution. However, the nature of these cells remains controversial in terms of clinical allo-HSCT. Therefore, we conducted a large prospective analysis of patients undergoing allogeneic HSCT for hematologic malignancies to evaluate MDSC recovery and function in the proinflammatory milieu post-transplant, and its immune suppressive mechanisms.Methods: We examined the expansion of circulating monocytic (M-) MDSCs and granulocytic (G-) MDSCs at the time of engraftment in 130 patients undergoing allo-HSCT. Further, we investigated differentially expressed genes between G-MDSCs and M-MDSCs by transcriptome resequencing and characterized the molecular functions using carboxyfluorescein succinimidyl ester (CFSE) assay.Results: The high M-MDSC group had a higher infection rate within 100 days, worse 1-year cumulative incidence of treatment-related mortality (TRM) and 2-year probability of event-free survival (EFS) compared to those with low M-MDSC group. The frequency of M-MDSCs was associated with preceding severe mucositis. Transcriptome profiling analysis of 2 isolated subtypes of MDSCs showed that matrix metalloproteinase-9 (MMP-9) was expressed much more highly in M-MDSCs than in G-MDSCs. The high expression of MMP-9 (P<0.001)and its upstream genes, including ARRB2 (P = 0.010) and F2RL1 (P = 0.024), in M-MDSC was confirmed using qRT-PCR. Moreover, MMP-9 concentrations in cell lysates (P < 0.001) and in culture supernatants (P = 0.001) were much higher in M-MDSCs than G-MDSCs, as shown by ELISA.Importantly, M-MDSCs isolated from patients post-HSCT had a higher capacity to suppress T cell responses than did G-MDSCs, and MMP-9 blockade more forcefully inhibited the immunosuppressive effect of M-MDSCs than that of G-MDSCs. Ultimately, the patients with high serum levels of MMP-9 had significantly higher infections within 100 days (P = 0.015), TRM by 1 year (P = 0.001) and a trend toward reduced EFS (P = 0.055) compared to those with low MMP-9.Conclusion: Our data demonstrated that early expansion of M-MDSCs was associated with early infections and poorer clinical outcomes than was expansion of G-MDSCs. Post-HSCT M-MDSCs exhibited increased levels of matrix metalloproteinase-9 (MMP-9), which might play a key role in worsening post-transplant infections and, ultimately, survival outcomes. DisclosuresKim:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Il-Yang: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Modulating the Immunologic Microenvironment in AML By Blocking Both CXCR4 and PD-L1

BackgroundWe have shown the importance of microenvironments by displaying the restoration of dysfunctional natural killer (NK) cells' antitumor effects both in vitro and in vivo after a trial of CXCR4 inhibition combined with conventional chemotherapy in acute myeloid leukemia (AML). Recently, the inhibition of programmed death-1(PD-1) /PD-ligand1 (PD-L1) axis in solid cancer has been regarded as a key factor to treating cancer by activating the suppressed immune cells. However, the significance of PD-1/PD-L1 expression in AML has yet to be established, even though PD-1/PD-L1 has already been targeted in clinical trials. Thus, our aim was to revitalize suppressed immune cells by utilizing CXCR4 blockade and anti-PD-L1 in combination with chemotherapy in an AML mouse model.Methods and Results The leukemic mouse model was induced by injecting C1498 (murine AML cell line) cells into C57/Bl-6 mice at D0, and leukemic blasts of the organs of several subgroups treated with cytosine arabinoside (Ara-C) (2 mg/kg, I.P.), plerixafor (2.5 mg/kg, S.C.), and anti-PD-L1 (200 ug/kg, I.P.) in one-by-one additive manners were examined (Fig. 1). Flow cytometric analyses at D+3, D+14, D+19, D+26 and histologic examination after sacrifice were performed to read the therapy-responsive changes of immune cell subsets and blasts reduction. Our data indicated noticeable benefits of this triple combinational treatment with plerixafor, anti-PD-L1, and Ara-C (AMP subgroup in Fig. 2 & Fig. 3) in removal of blasts in vivo; especially, survival rates of leukemic mice in the triple-combined treatment subgroup were higher than those in other subgroups. Moreover, in immune cell subsets in the peripheral blood, the frequency of CD4+ and CD8+ T cells was significantly increased specifically early after completion of the treatment in the triple combinational subgroup with remarkable changes of monocytic myeloid-derived suppressor cells (M-MDSCs) as well as regulatory T cells (Tregs), compared to that of other subgroups. Interestingly, in the triple combinational subgroup, Tregs and M-MDSCs were both significantly decreased while G-MDSCs were significantly increased in the bone marrow (BM) of leukemic mice that were sacrificed alive at D+26. In addition, the phenotypic levels of PD-1 both in the BM and the spleen were relatively low compared to those of other subgroups. These findings implied that the modulation of immune status by applying plerixafor and anti-PD-L1 with Ara-C could lead to a more efficient leukemic blasts ablation through the activation of CD4+ and CD8+ T cells and possibly the suppression of Tregs and/or M-MDSCs in AML. Integrated responses of NK, NKT, and DC cells should be pursued in the future.Conclusion We demonstrated the impact of a strategic triple combinational therapy with anti-PD-L1 and plerixafor with Ara-C in AML. Our results suggest some clues and provide guidelines to developing therapeutic strategies for chemotherapy-resistant patients in clinic by the modulation of leukemic microenvironments. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

PD-1 Mediates Lineage Fate Determination and Function of Myeloid Cells in Response to Tumor-Mediated “Emergency” Myelopoiesis

PD-1 is an inhibitory receptor for which blocking agents have achieved significant success as anti-cancer therapeutics. The mechanism(s) of how PD-1 compromises anti-tumor function and how such effect is reversed by PD-1 blockade remain poorly understood. The rapid change in hematopoietic output that occurs in response to immunologic stress is known as “emergency” myelopoiesis. This process is co-opted by tumors to evade the immune system by inducing potent immunosuppression. Cancer-driven granulo-monocytopoiesis modifies the composition of the hematopoietic output by stimulating the expansion of tumor promoting immature myeloid populations, defined as myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs). Monocytic (M-) and granulocytic (PMN-) MDSCs and TAMs differentiate from granulocyte/macrophage progenitors (GMP) in the bone marrow. We analyzed the myeloid compartment of tumor-bearing mice to determine the expression and function of PD-1 in myeloid cells during cancer-driven emergency myelopoiesis. Using three different mouse tumor models (MC38, B16 and MC17), we determined that PD-1 and its natural ligand PD-L1, were expressed at high levels in all subsets of myeloid cells isolated from the spleen of tumor-bearing mice, including CD11b+Ly6C+ M-MDSC, CD11b+Ly6G+ PMN-MDSC, CD11b+F/480+ macrophages and CD11b+HLA-DR+ dendritic cells (DC). This was in contrast to the significantly lower or undetectable levels of PD-1 expressed in these cellular counterparts isolated from non-tumor bearing mice. High expression of PD-1 and PD-L1 was also identified in these myeloid subsets isolated from the tumor site and at sites of secondary myelopoiesis in the gut. Because these myeloid cell populations differentiate from GMP upon cancer-mediated emergency myelopoiesis, we examined bone marrow myeloid progenitors in tumor bearing and control, non-tumor bearing mice. In non-tumor bearing mice, PD-1 was detected in Lin-/Sca+/Kit+ (LSK) myeloid progenitors, whereas PD-L1 was expressed in Lin-/Sca-/Kit+ (LK), common myeloid progenitors (CMP) and GMP. In tumor-bearing mice, both PD-1 and PD-L1 expression was significantly higher in all myeloid progenitors compared to tumor-free control mice. To determine whether PD-1-mediated signaling in myeloid cells might affect the magnitude and composition of the myeloid output that is altered by cancer-mediated emergency response, we used PD-1 deficient mice. PD-1 ablation, which decreased tumor growth and metastasis, stimulated the differentiation of hematopoietic progenitor cells and resulted in increase of Ly6Chi monocytes and monocyte-derived DC (mo-DC). Abrogation of PD-1 signaling enhanced the maturation of MDSCs by inducing the lineage commitment transcription factors IRF8, IRF4 and RORC1. IRF8 and IRF4 promote monocyte/macrophage and hinder granulocyte differentiation, whereas RORC1 is required for expansion of Ly6Chi monocytes and resolution of inflammation. To examine whether the effects of PD-1 on cancer-mediated emergency myelopoiesis and on myeloid lineage commitment and differentiation were mediated by myeloid cell-intrinsic mechanisms, we generated mice with conditional targeting of the PD-1 gene in the myeloid compartment by crossing PD-1fl/fl with LysM-Cre mice. Myeloid-specific ablation of PD-1 signaling in PD-1fl/fl/LysM-Cre mice impaired tumor growth to a similar extent as global PD-1 ablation in PD1-KO mice and induced a myeloid cell fate switch from MDSCs to effector-like myeloid cells that could be identified in spleen and tumor. Further, abrogation of PD-1 signaling in the myeloid compartment prevented the expansion of tumor-stress associated GMP in PD-1fl/fl/LysM-Cre mice and resulted in increased differentiation of committed monocyte progenitors (CMOP) and monocyte progenitors (MP) in the bone marrow. Moreover, PD-1 deletion significantly diminished NO production by M-MDSC and reversed their ability to suppress antigen-specific T cell responses. Our results reveal a previously unidentified role of the PD-1:PD-L1 pathway in the differentiation of lineage-committed myeloid progenitors during tumor-mediated emergency myelopoiesis to promote MDSCs and suppress effector monocytes and mo-DCs. Switch of myeloid progenitor fate commitment might be a key mechanism by which PD-1 blockade mediates its anti-tumor function. DisclosuresNo relevant conflicts of interest to declare.

A Proteomic Atlas of Lineage and Cancer-Polarized Expression Modules in Myeloid Cells Modeling Immunosuppressive Tumor-Infiltrating Subsets.

Monocytic and granulocytic myeloid-derived suppressor cells together with tumor-infiltrating macrophages constitute the main tumor-infiltrating immunosuppressive myeloid populations. Due to the phenotypic resemblance to conventional myeloid cells, their identification and purification from within the tumors is technically difficult and makes their study a challenge. We differentiated myeloid cells modeling the three main tumor-infiltrating types together with uncommitted macrophages, using ex vivo differentiation methods resembling the tumor microenvironment. The phenotype and proteome of these cells was compared to identify linage-dependent relationships and cancer-specific interactome expression modules. The relationships between monocytic MDSCs and TAMs, monocytic MDSCs and granulocytic MDSCs, and hierarchical relationships of expression networks and transcription factors due to lineage and cancer polarization were mapped. Highly purified immunosuppressive myeloid cell populations that model tumor-infiltrating counterparts were systematically analyzed by quantitative proteomics. Full functional interactome maps have been generated to characterize at high resolution the relationships between the three main myeloid tumor-infiltrating cell types. Our data highlights the biological processes related to each cell type, and uncover novel shared and differential molecular targets. Moreover, the high numbers and fidelity of ex vivo-generated subsets to their natural tumor-shaped counterparts enable their use for validation of new treatments in high-throughput experiments.

Treatment with lentiviral vectors encoding shRNA against interleukin 10 modulates the immunosuppressive activity of murine colon carcinoma-associated myeloid-derived suppressor cells.

Myeloid-derived suppressor cells (MDSCs) are potent suppressors of antitumor immunity and their accumulation is often associated with poor prognosis. The aim of the present study was to determine the mechanisms of action of lentiviral vectors encoding short hairpin (sh)RNA against interleukin-10 (IL-10), with particular emphasis on their influence on the activity of tumor-derived MDSCs. Lentiviral vectors encoding shRNA against IL-10 (shIL-10 LVs) were utilized to silence the expression of IL-10 either in MDSCs that were generated ex vivo from bone marrow cells cultured in the presence of supernatant from MC38 colon carcinoma cells, or in situ in the MC38 murine colon carcinoma environment. Although monocytic MDSCs (M-MDSCs) transduced with shIL-10 LVs exhibited increased suppressor activity, transduction of polymorphonuclear MDSCs (PMN-MDSCs) appeared to reduce their ability to inhibit T lymphocyte functions. Analysis of EGFP expression in MC38 tumors revealed that intratumorally inoculated shIL-10 LVs transduced tumor-infiltrating myeloid cells with the highest efficiency and, led to a decreased IL-10 level in the tumor microenvironment. However, the effect was accompanied by increased influx of PMN-MDSCs into tumors observed both on the 6th and on the 10th day after shIL-10 LV injections. Nevertheless, it was noted that suppressor activity of myeloid cells isolated from tumors was dependent on the efficiency of tumor-derived PMN-MDSC transduction with shIL-10 LVs. The increased percentage of transduced PMN-MDSCs on the 10th day was associated with diminished immunosuppressive activity of tumor-derived myeloid cells and an elevated ratio of cytotoxic T lymphocytes to M-MDSCs. The obtained data indicated that treatment with shIL-10 LVs may result in modulation of the immunosuppressive activity of MC38 colon carcinoma-derived MDSCs.