Polymorphonuclear Myeloid-derived Suppressor Cells Research Articles

Monocytic myeloid-derived suppressor cells as an immune indicator of early diagnosis and prognosis in patients with sepsis

BackgroundImmunosuppression is a leading cause of septic death. Therefore, it is necessary to search for biomarkers that can evaluate the immune status of patients with sepsis. We assessed the diagnostic and prognostic value of low-density neutrophils (LDNs) and myeloid-derived suppressor cells (MDSCs) subsets in the peripheral blood mononuclear cells (PBMCs) of patients with sepsis.MethodsLDNs and MDSC subsets were compared among 52 inpatients with sepsis, 33 inpatients with infection, and 32 healthy controls to investigate their potential as immune indicators of sepsis. The percentages of LDNs, monocytic MDSCs (M-MDSCs), and polymorphonuclear MDSCs (PMN-MDSCs) in PBMCs were analyzed. Sequential organ failure assessment (SOFA) scores, C-reactive protein (CRP), and procalcitonin (PCT) levels were measured concurrently.ResultsThe percentages of LDNs and MDSC subsets were significantly increased in infection and sepsis as compared to control. MDSCs performed similarly to CRP and PCT in diagnosing infection or sepsis. LDNs and MDSC subsets positively correlated with PCT and CRP levels and showed an upward trend with the number of dysfunctional organs and SOFA score. Non-survivors had elevated M-MDSCs compared with that of patients who survived sepsis within 28 days after enrollment.ConclusionsMDSCs show potential as a diagnostic biomarker comparable to CRP and PCT, in infection and sepsis, even in distinguishing sepsis from infection. M-MDSCs show potential as a prognostic biomarker of sepsis and may be useful to predict 28-day hospital mortality in patients with sepsis.

Blocking OLFM4/galectin-3 axis in placental polymorphonuclear myeloid-derived suppressor cells triggers intestinal inflammation in newborns

Fetal growth restriction (FGR) is a major cause of premature and low-weight births, which increases the risk of necrotizing enterocolitis (NEC); however, the association remains unclear. We report a close correlation between placental polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) and NEC. Newborns with previous FGR exhibited intestinal inflammation and more severe NEC symptoms than healthy newborns. Placental PMN-MDSCs are vital regulators of fetal development and neonatal gut inflammation. Placental single-cell transcriptomics revealed that PMN-MDSCs populations and olfactomedin-4 gene (Olfm4) expression levels were significantly increased in PMN-MDSCs in later pregnancy compared to those in early pregnancy and non-pregnant females. Female mice lacking Olfm4 in myeloid cells mated with wild-type males showed FGR during pregnancy, with a decreased placental PMN-MDSCs population and expression of growth-promoting factors (GPFs) from placental PMN-MDSCs. Galectin-3 (Gal-3) stimulated the OLFM4-mediated secretion of GPFs by placental PMN-MDSCs. Moreover, GPF regulation via OLFM4 in placental PMN-MDSCs was mediated via hypoxia inducible factor-1α (HIF-1α). Notably, the offspring of mothers lacking Olfm4 exhibited intestinal inflammation and were susceptible to NEC. Additionally, OLFM4 expression decreased in placental PMN-MDSCs from pregnancies with FGR and was negatively correlated with neonatal morbidity. These results revealed that placental PMN-MDSCs contributed to fetal development and ameliorate newborn intestinal inflammation.

The Influence of Myeloid-Derived Suppressor Cell Expansion in Neuroinflammation and Neurodegenerative Diseases.

The neuro-immune axis has a crucial function both during physiological and pathological conditions. Among the immune cells, myeloid-derived suppressor cells (MDSCs) exert a pivotal role in regulating the immune response in many pathological conditions, influencing neuroinflammation and neurodegenerative disease progression. In chronic neuroinflammation, MDSCs could lead to exacerbation of the inflammatory state and eventually participate in the impairment of cognitive functions. To have a complete overview of the role of MDSCs in neurodegenerative diseases, research on PubMed for articles using a combination of terms made with Boolean operators was performed. According to the search strategy, 80 papers were retrieved. Among these, 44 papers met the eligibility criteria. The two subtypes of MDSCs, monocytic and polymorphonuclear MDSCs, behave differently in these diseases. The initial MDSC proliferation is fundamental for attenuating inflammation in Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), but not in amyotrophic lateral sclerosis (ALS), where MDSC expansion leads to exacerbation of the disease. Moreover, the accumulation of MDSC subtypes in distinct organs changes during the disease. The proliferation of MDSC subtypes occurs at different disease stages and can influence the progression of each neurodegenerative disorder differently.

Lanosterol synthase deficiency promotes tumor progression by orchestrating PDL1-dependent tumor immunosuppressive microenvironment.

Lipid metabolic reprogramming is closely related to tumor progression with the mechanism not fully elucidated. Here, we report the immune-regulated role of lanosterol synthase (LSS), an essential enzyme in cholesterol synthesis. Database analysis and clinical sample experiments suggest that LSS was lowly expressed in colon and breast cancer tissues, which indicates poor prognosis. The biological activity of tumor cell lines and tumor progression in NOD scid gamma (NSG) mice were not affected after LSS knockdown, whereas LSS deficiency obviously aggravated tumor burden in fully immunized mice. Flow cytometry analysis showed that LSS knockdown significantly promoted the formation of tumor immunosuppressive microenvironment, characterized by the increase in M2 macrophages and polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), as well as the decrease in anti-tumoral T lymphocytes. With the inhibition of myeloid infiltration or loss function of T lymphocytes, the propulsive effect of LSS knockdown on tumor progression disappeared. Mechanistically, LSS knockdown increased programmed death ligand 1 (PDL1) protein stability by 2,3-oxidosqualene (OS) binding to PDL1 protein. Anti-PDL1 therapy abolished LSS deficiency-induced immunosuppressive microenvironment and cancer progression. In conclusion, our results show that LSS deficiency promotes tumor progression by establishing an OS-PDL1 axis-dependent immunosuppressive microenvironment, indicative of LSS or OS as a potential hallmark of response to immune checkpoint blockade.

Intravenous administration of IL-12 encoding self-replicating RNA-lipid nanoparticle complex leads to safe and effective antitumor responses

Interleukin 12 (IL-12) is a potent immunostimulatory cytokine mainly produced by antigen-presenting cells (e.g., dendritic cells, macrophages) and plays an important role in innate and adaptive immunity against cancers. Therapies that can synergistically modulate innate immunity and stimulate adaptive anti-tumor responses are of great interest for cancer immunotherapy. Here we investigated the lipid nanoparticle-encapsulated self-replicating RNA (srRNA) encoding IL-12 (referred to as JCXH-211) for the treatment of cancers. Both local (intratumoral) and systemic (intravenous) administration of JCXH-211 in tumor-bearing mice induced a high-level expression of IL-12 in tumor tissues, leading to modulation of tumor microenvironment and systemic activation of antitumor immunity. Particularly, JCXH-211 can inhibit the tumor-infiltration of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). When combined with anti-PD1 antibody, it was able to enhance the recruitment of T cells and NK cells into tumors. In multiple mouse solid tumor models, intravenous injection of JCXH-211 not only eradicated large preestablished tumors, but also induced protective immune memory that prevented the growth of rechallenged tumors. Finally, intravenous injection of JCXH-211 did not cause noticeable systemic toxicity in tumor-bearing mice and non-human primates. Thus, our study demonstrated the feasibility of intravenous administration of JCXH-211 for the treatment of advanced cancers.

Abstract 3917: A CXCR4 partial agonist TFF2-MSA improves anti-PD-1 immunotherapy in advanced gastric cancer by selectively targeting PMN-MDSC

Abstract Introduction: Advanced gastric cancer poses a challenge for PD-1 immunotherapy due in part to the prevalence of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). PMN-MDSCs are mostly immature granulocytes but coexist with mature neutrophils, complicating their precise targeting. While PMN-MDSCs highly express CXCR4, recent clinical trials suggest that CXCR4 antagonists may provide limited additive efficacy to PD-1 blockade. This study explored the efficacy of a secreted CXCR4 partial agonist, trefoil factor family 2 (TFF2), in the context of anti-PD-1 refractory gastric cancer. Methods: We fused mouse TFF2 with murine serum albumin to generate a novel TFF2-MSA peptide with extended half-life, and evaluated its therapeutic effects with or without anti-PD-1 antibody. As histidine decarboxylase (HDC) is expressed in immature neutrophils, we used the HDC-GFP transgene to track PMN-MDSC in vivo. The HDC-GFP mice received subcutaneous or orthotopic implantation of murine syngeneic gastric cancer cells and subsequent treatments. Additionally, human blood was assessed for both serum TFF2 and immune profiles. Results: The combination of TFF2-MSA plus anti-PD-1 antibody displayed remarkable synergy, boosting intratumoral cytotoxic CD8 T cells by 50-fold, leading to tumor regression or eradication, 80% reduction of distant metastasis and 2-fold extension of mouse survival. The immunosuppressive HDC-GFP+ PMN-MDSCs expressed the highest level of CXCR4 among immune cells, and TFF2-MSA treatment systematically reduced HDC-GFP+ PMN-MDSCs in the tumor, blood, spleen and their myeloid progenitors in the bone marrow. In contrast, CXCR4 antagonist AMD3100 in combination with anti-PD-1 failed to restrict tumor growth or PMN-MDSCs. Further single-cell RNA-seq and functional assays revealed that combination of TFF2-MSA plus anti-PD-1 induced a skewing of remaining tumor HDC-GFP+PMN-MDSC compositions from highly immature CD300ld+ subsets to less immature subsets expressing interferon-stimulated genes, accompanied by reduced immunosuppression and increased antigen presentation functions. Rather than local reprogramming, this compositional shift stemmed from an IRF1-driven interferon response in splenic HDC-GFP+ PMN-MDSCs. In human, PMN-MDSCs marked by LOX1 significantly expanded in the blood of gastric cancer patients compared to healthy donors. Human LOX1+ PMN-MDSCs showed an inverse correlation with T cell number, activation, proliferation and the serum TFF2 level. Conclusions: TFF2-MSA synergizes with PD-1 blockade by selectively targeting CXCR4high PMN-MDSCs. This study provides a rational for a novel combination therapy of the CXCR4 partial agonist, TFF2-MSA, rather than CXCR4 antagonists, plus PD-1 blockade for treatment of advanced gastric cancer. Citation Format: Jin Qian, Chenkai Ma, Quin T. Waterbury, Christine S. Moon, Xiaofei Zhi, Feijing Wu, Ruhong Tu, Biyun Zheng, Hiroki Kobayashi, Leah B. Zamechek, Ryan H. Moy, Arnold Han, Bruce Daugherty, Seth Lederman, Timothy C. Wang. A CXCR4 partial agonist TFF2-MSA improves anti-PD-1 immunotherapy in advanced gastric cancer by selectively targeting PMN-MDSC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3917.

Abstract 1803: ACOD1 is a key regulator of immunosuppressive MDSCs, prostate cancer progression, and resistance to immunotherapy

Abstract Although Immune checkpoint therapy (ICT) is highly effective in a wide range of malignancies, patients with metastatic castration-resistant prostate cancer (mCRPC) are largely resistant to ICT. Yet, the cellular and molecular basis of the poor response to ICT in lethal prostate cancer remain poorly defined. Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) have emerged as a key driver of prostate cancer progression and resistance to immunotherapy. Yet the molecular mechanisms underlying the immunosuppressive activities of PMN-MDSCs remains poorly defined. By performing single-cell RNA-sequencing (scRNA-seq) of prostate tumors, we identified Acod1, a gene that encodes cis-aconitate decarboxylase (ACOD1) and catalyzes the synthesis of itaconate from cis-aconitate in the tricarboxylic acid (TCA) cycle, is among the top 5 metabolic-related genes that are overexpressed in PMN-MDSCs. Moreover, bulk RNA-seq and microarray datasets revealed that intratumoral and splenic PMN-MDSCs express a significantly higher level of Acod1 compared to less immunosuppressive bone marrow PMN-MDSCs. Importantly, high ACOD1 expression is strongly associated with significantly shorter overall survival and higher Gleason scores in human mCRPC. Using an autochthonous whole-body Acod1-KO mouse model, we showed that Acod1 KO in TRAMP mice led to a reduction in tumor burden and an increase in overall survival. Furthermore, using syngeneic prostate cancer models, we showed that whole-body or PMN-specific Acod1-KO delayed tumor progression. As expected, Acod1 KO dramatically reduced the production of itaconate in bone marrow-derived MDSCs (BM-MDSC) as shown by targeted metabolic profiling. Importantly, we found that Acod1 KO impaired immunosuppressive activities of BM-MDSC and an increase in CD3+ and CD8+ T cell infiltration in the tumors. Also, Acod1-KO in BM-MDSC led to a reduction of H2DCFDA staining intensity suggesting a reduction in the production of reactive oxygen species (ROS). Gene set enrichment analysis (GSEA) revealed that Acod1-KO MDSCs have hyperactive oxidative phosphorylation (OXPHOS) compared to Acod1-WT BM-MDSCs. KO of Acod1 also leads to suppression of key MDSC functions signaling such as TNFα/NFκB, IL6/JAK/STAT3, and C/EBPβ pathways. In summary, our data suggests that the upregulation of ACOD1 in PMN-MDSCs has a vital role in prostate cancer progression and resistance to ICT by regulating their immunosuppressive activities through metabolic reprogramming. Also, our data suggest that targeting ACOD1 could be an effective therapeutic strategy for lethal prostate cancer as a monotherapy and in combination with immunotherapy. Citation Format: Celia Sze Ling Mak, Xin Liang, Jessica Suh, Derek Liang, Ming Zhu, Guocan Wang. ACOD1 is a key regulator of immunosuppressive MDSCs, prostate cancer progression, and resistance to immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1803.

Abstract 2706: Identification and characterization of cancer-associated polymorphonuclear cell subsets in mice

Abstract Background: Neutrophils are the main type of polymorphonuclear cells (PMN) and comprise most immune cells in the body. PMN cells are upregulated in cancer and accumulate in the tumors. Tumor-associated PMNs comprise a heterogeneous population consisting of immunologically active mature neutrophils and immature polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). The phenotype of these cells evolves with disease progression and is implicated in modulating immune response. However, there is yet to be a consensus to define PMN populations in tumors and blood. Methods: Here, we used single-cell RNA-seq, bulk RNA sequencing, flow cytometry, and immunohistochemistry (IHC) analysis to characterize cancer-associated PMN-MDSCs in tumor-bearing mice. Results: Single-cell RNA-seq data from lung tumors and healthy individuals revealed five metaclusters (MC): MCA, MCB, MCC, MCD, and MCE. MCA and MCB made up 34.4 and 65.1% of PMNs in healthy tissues, respectively. MCA, MCB, MCC, MCD, and MCE comprised 3.8%, 23.5% 3.3% 14.6%, and 54.7% of PMNs in tumors, respectively. Genes enriched in MCA and MCE were associated with MDSCs and myeloid progenitor cells. MCB and MCC were associated with inflammatory responses mediated by TNF-alpha signaling and neutrophil degranulation. MCD was associated with a CD33 myeloid cell phenotype and had high expression levels of CD274, Pdcd1lg2, Havcr2, and Tigit genes. Cells from MCE were associated with protein translation signatures and had elevated levels of Nt5e. Gene expression signatures from single-cell RNA-seq data were compared with bulk transcriptomic data from healthy mouse prostates and Pten-null prostate tumors characterized by high PMN cell infiltration. Gene set enrichment analysis showed enrichments after androgen deprivation therapy and Cluster MCE was associated with castration-resistant tumors. Flow cytometric and IHC analysis confirmed the enrichment of PMN cells expressing elevated levels of proteins identified from gene expression analysis including CD73, PD-L1, and PD-L2. Conclusion: This study offers further insights into the distinct subsets of PMN-MDSCs present in tumors. Citation Format: Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Takashi Kikuchi, Yasunori Mori, Takafumi Minami, Kazuhiro Yoshimura, Kazutoshi Fujita, Kazuto Nishio, Hirotsugu Uemura. Identification and characterization of cancer-associated polymorphonuclear cell subsets in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2706.

Abstract 104: Profiling peripheral blood to predict response to targeted androgen receptor axis therapy in mice

Abstract Background: Targeting the androgen receptor (AR) signaling axis (ARAT) continues to be the mainstay treatment for advanced-stage prostate cancer. Using second-generation antiandrogens like abiraterone acetate (Abi) and apalutamide (Apa) has contributed to the survival of prostate cancer patients. However, resistance to these therapies remains a problem and most of these patients progress to castration-resistant prostate cancer (CRPC). Myeloid-derived suppressor cells (MDSCs) have been shown to drive CRPC. We previously showed that unfavorable responses to androgen deprivation therapy (ADT) or ADT plus Apa were associated with polymorphonuclear MDSCs (PMN-MDSCs) cells enriched in prostate tumors from conditional Pten/Trp53-double knockout (DKO) mice. Here, we explore the association between pre-treatment immune cell subsets blood and antitumor to ARAT therapy DKO mice. Methods: Twenty-eight-week-old DKO mice were surgically castrated and after four weeks were randomized to treatments with vehicle, Apa or Abi for an additional four weeks (n=20). Individual treatment responses were assessed and classified according to tumor burden as follows: high tumor burden (HTB), ≥20% of median; moderate tumor burden (MTB), -20% to 20% of median; or low tumor burden (LTB), ≤-20% of median. Peripheral blood was collected both before and after treatment and analyzed by multi-color flow cytometry panels for lymphoid and myeloid subsets. Blood samples from healthy wildtype and untreated DKO mice with castration-naïve prostate tumors were collected as reference samples. Subsets of PMN-MDSCs and monocytic-MDCSs (m-MDSCs) were represented as % of total abundance and 5 of parental population. revealed a signature that was correlated with treatment responses. Profiles were constructed and the data was used to train supervised learning models to predict treatment responses. Shapely additive explanations (ShAP) were used to determine feature importance. The model was tested and validated on an independent cohort of 20 DKO mice treated with ADT and ADT plus Abi. Results: Moderate prediction from baseline blood could be identified for tumor burden following ARAT using a Naïve Bayes classifier. Model evaluation, using an independent cohort, yielded favorable performance with area under the curve (AUC) mean, 0.707; HTB, 0.627; MTB, 0.750; and LTB, 0.745. The most important features for prediction were identified. Conclusion: Our study revealed that MDSC subsets present in blood were associated with treatment responses to ARAT. Citation Format: Marco A. De Velasco, Yurie Kura, Kazuko Sakai, Yoshitaka Saito, Takafumi Minami, Kazuhiro Yoshimura, Kazutoshi Fujita, Kazuto Nishio, Hirotsugu Uemura. Profiling peripheral blood to predict response to targeted androgen receptor axis therapy in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 104.

Abstract 7519: Elucidation of the mechanism of acquisition of immune checkpoint inhibitor resistance by chronic inflammation

Abstract Introduction: Eight molecules that are structurally similar to angiopoietin but do not bind to angiopoietin's specific receptor Tie2 were identified and named angiopoietin-like factors (ANGPTL). ANGPTL2, particularly abundantly expressed in adipose tissue, promotes damage repair through tissue remodeling, and contributes to tissue homeostasis; however, in severe obesity, ANGPTL2 is overexpressed, resulting in irreversible tissue remodeling, which induces chronic inflammation and is involved in systemic insulin resistance and diabetes development. On the other hand, it is unclear how systemic chronic inflammation controlled by ANGPTL2 is involved in cancer progression and acquisition of immune checkpoint inhibitor (ICI) resistance. Therefore, we aimed to elucidate the mechanisms in the acquisition of ICI resistance by systemic chronic inflammation from the perspective of ANGPTL2. Materials and Methods: 1. To induce chronic inflammation in adipose tissue, BALB/c mice were fed high-fat-diet (HFD) for 6 weeks. CT26 cells, a mouse colon cancer cell line, were subcutaneously implanted in normal diet (ND) and HFD mice and anti PD-1/PD-L1 antibody was administered intraperitoneally. Immune cell fractions in tumor tissue and bone marrow were analyzed by flow cytometry. 2. CT26 was subcutaneously implanted in WT and systemic ANGPTL2-deficient (Angptl2−/−) mice, and anti PD-1/PD-L1 antibody was administered intraperitoneally. Tumor size and survival time were analyzed. Bone marrow cells were isolated and the immune cell fractions were analyzed by flow cytometry, and the expression of inflammatory cytokines in adipose tissue were also analyzed. 3. Bone marrow cells were isolated from BALB/c mice, and myeloid-derived suppressor cells (MDSCs) were established in vitro by GM-CSF and IL-6. Recombinant ANGPTL2 protein was added, and MDSC differentiation and function were evaluated by flow cytometry and qRT-PCR. Results: 1. HFD mice had larger tumor size and poorer response to ICI treatment compared to ND mice. In tumor microenvironment, MDSCs were increased in HFD mice. HFD mice had significantly increased MDSCs, especially polymorphonuclear MDSCs (PMN-MDSCs) in bone marrow. 2. ICI-treated Angptl2−/− mice showed higher treatment efficacy and prolonged survival compared to WT mice. In bone marrow, MDSCs were reduced in Angptl2−/− mice under ICI treatment. In adipose tissue, the expression of chronic inflammatory markers was increased. 3. In vitro, addition of recombinant ANGPTL2 protein to MDSCs induced differentiation from mouse bone marrow cells did not significantly increase the cell ratio of MDSCs. No changes in the expression of MDSCs markers were observed in qRT-PCR. Conclusions: Chronic inflammation induced by ANGPTL2 promotes MDSCs differentiation and maturation in the bone marrow, which may suppress anti-tumor immunity and contribute to ICI resistance. Citation Format: Shinsei Yumoto, Haruki Horiguchi, Hideo Baba, Yuichi Oike. Elucidation of the mechanism of acquisition of immune checkpoint inhibitor resistance by chronic inflammation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7519.

Abstract 7367: Dissecting cellular and molecular alterations in pre-invasive to invasive lung cancer progression at single-cell resolution

Abstract Non-small cell lung cancer (NSCLC) accounts for most cancer-related deaths worldwide, largely due to diagnosis at advanced metastatic stages. Increased implementation of low-dose computed tomography (CT)-guided screening has led to the identification of non-solid lesions or ground-glass opacities (GGOs) that are not visible on plain chest radiography and can harbor very early-stage tumors. Growth of the lesions and/or development of a solid component can indicate more aggressive behavior. Using the low-dose CT reduced lung cancer mortality by >20%, underscoring the need for early detection and intervention. However, the cellular and molecular determinants contributing to the malignant progression of those early preinvasive lesions remain poorly understood. To assess intratumoral heterogeneity and associated dynamic changes in the immune contexture during early lung carcinogenesis, we performed single-cell RNA-seq and Hyperion imaging on surgically resected freshly harvested tissues from 37 patients (matched solid and non-solid components of lesions and adjacent non-involved lungs), representing a spectrum from preneoplasia to invasive disease. Analysis of >300K cells identified cellular, transcriptomic, and metabolic alterations as well as tumor-stroma cross-talk pathways. Specifically, preinvasive to invasive disease progression was associated with significant changes in the immune landscape determined by an increase in exhausted CD4/CD8 T-cells, suppressive T-regs, polymorphonuclear myeloid-derived suppressor cells, and M2-like macrophages; and a decrease in cytotoxic CD8 T-cells, NK cells, and inflammatory cDC2 cells, suggesting that activation of immunosuppressive/anti-inflammatory microenvironment and suppression of immune activation microenvironment may enable tumor progression. Citation Format: Liron Yoffe. Dissecting cellular and molecular alterations in pre-invasive to invasive lung cancer progression at single-cell resolution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7367.

Abstract 3866: Azvudine: An emerging immunomodulator in the treatment of cancer and viral infections

Abstract Azvudine (FNC) is a nucleoside analog that has secured approval from the CDE in China for the treatment of both AIDS and COVID-19. In these contexts, it has showed remarkable efficacy and safety when taken orally. Typically, nucleoside analog drugs function by integrating into DNA and impeding DNA synthesis, evident in drugs like 5-FU, Capecitabine, Ara-C, and Gemcitabine. Furthermore, FNC has been reported to exhibit robust anti-tumor properties, curbing cell proliferation, initiating G1 and S phase arrests, and advancing apoptosis across various human cancer cell lines. Grounded in this mode of action, we have ascertained that the anti-tumor effects of FNC intricately align with the expression of deoxycytidine kinase (dCK) both in vitro and in vivo. Remarkably, our studies delved into the effects and underlying mechanisms of FNC in enhancing the tumor microenvironment within solid tumors. Our findings, stemming from cell-based assays and in vivo animal experiments, elucidate the following: 1. FNC can trigger immunogenic cell death (ICD) in tumor cells. This is evidenced by the surface presentation and liberation of damage-associated molecular patterns (DAMPs) such as Calreticulin, HSP70, HSP90, Annexin A1, and HMGB1, which in turn stimulate both innate and adaptive immune responses. 2. FNC substantially reduces the population of monocytic-myeloid derived suppressor cells (M-MDSC) and Polymorphonuclear-myeloid derived suppressor cells (PMN-MDSC) in the tumor microenvironment. Concurrently, it boosts the infiltration and proliferation of CD8+T, CD4+T and NK cells. This instigates the transformation of the tumor microenvironment from a 'cold' state to a 'hot' one, enhancing the synergistic effects of PD-1 when used in tandem with FNC. This mechanism was substantiated through a high proportion of MDSCs observed in H22 and CT-26 syngeneic models, and contrastingly, a low proportion in MC38 and LL/2 in vivo syngeneic models. Notably, every animal subjected to combined FNC and PD-1 treatment in the H22 and CT-26 in vivo models witnessed complete tumor regression. Given these revelations, there's a compelling argument that FNC monotherapy possesses immense potential as an anti-tumor agent. The potent anticancer effects of FNC in vitro and in vivo warrants further investigation of its anticancer potential as immunomodulator. Citation Format: Pan Li, Limin Jia, Zhaoyang Wang, Jinfa Du. Azvudine: An emerging immunomodulator in the treatment of cancer and viral infections [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3866.

Abstract 5366: ATR promotes extracellular matrix stiffness mediated cytoskeleton remodeling and immunosuppression

Abstract The stiffening of the extracellular matrix (ECM), a phenomenon that often promotes metastasis and immunosuppression in many cancers, is a process that is not yet fully understood. Our study reveals that ATR, a molecule primarily recognized for its role in maintaining the genome, plays a crucial role in ECM stiffness-induced immune evasion and metastasis in triple negative breast cancer (TNBC) through DNA repair independent manner. In response to ECM stiffness, ATR activates SUN2, a component of the linker of nucleoskeleton and cytoskeleton (LINC) complex. This activation enhances the interaction of SUN2 with outer nuclear membrane proteins KASH1 and KASH2. The interaction between SUN2 and KASH1/2 facilitates the nuclear localization of β-catenin, which in turn promotes epithelial mesenchymal transition (EMT) and reduces the expression of E-cadherin. E-cadherin is essential for attracting CD103+ immune cells that perform anti-tumor immunity. Interestingly, inhibiting ATR reduces EMT in tumor cells, leading to an increase in CD103+ dendritic cell infiltration while decreasing neutrophil and polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) infiltration. Further, we found that ATR levels are inversely correlated with immunotherapy response rates in patients. The alteration in immune cell composition sensitizes tumors to immunotherapy, thereby suppressing tumor growth and metastasis. In conclusion, the role of ATR in remodeling the immune environment could be crucial for optimizing the clinical use of ATR inhibitors. This makes ATR a promising target for overcoming immunotherapy resistance. We suggest early or prolonged treatment with an ATR inhibitor to potentially reduce metastasis rates and improve the prognosis of TNBC patients. Furthermore, we suggest using ATR levels as a marker to predict response rates and prognosis in TNBC patients. For patients with higher ATR expression levels, combination treatment with ATR inhibitors and immunotherapy may yield better outcomes. Enhanced anti-tumor immunity could increase the chances for patients to eliminate cancer cells and help end breast cancer. Finally, our research suggests the combined treatment of ATR inhibition and immunotherapy for patients without necessarily applying DNA damage stimulation. This approach could potentially reduce toxicity while still benefiting patients. Citation Format: Xinyi Tu, Zhenkun Lou, Robert Mutter. ATR promotes extracellular matrix stiffness mediated cytoskeleton remodeling and immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5366.

Abstract 6680: High-fiber diet induces favorable gut microbiota, reduces immunosuppression, and inhibits lung cancer development

Abstract Emerging evidence suggests that resident microbial communities act as a central regulator of host homeostasis. The dynamic structure, composition, and function of gut microbiota can be influenced by numerous factors, among which nutritional profile act as most crucial determinant. Microbial consortia inhabiting the gut have been implicated in the etiology and pathogenesis of various cancers and are known to influence cancer immunosurveillance and response to immunotherapy. Despite these known associations, the underlying mechanisms by which dietary interventions such as those rich in fiber (high-fiber diet) regulate gut-immune axis in prevention of lung cancer are poorly defined. Here, we employed a human-relevant mouse model in which knockout of G-protein coupled receptor 5A (Gprc5a−/−) and exposure to tobacco lead to development of preneoplasia and lung adenocarcinoma (LUAD). Mice were randomly grouped based on dietary treatment: no fiber (control), 10% cellulose, 10% pectin-inulin following weaning (early life) or after transplant of MDA-F471 NNK-induced LUAD cells (dietary intervention). Tumor growth and volumes were most significantly reduced in mice fed a high-fiber pectin-inulin diet. Notably, anti-tumor effects of the high-fiber diet were observed in both early life and later dietary intervention settings. 16S rRNA-Seq analysis of fecal pellets revealed significant differences in gut alpha as well as beta diversity, the latter indicating clear separation of community structure between fiber-deprived versus high-fiber diet groups. Evidently, gut microbiota of pectin-inulin fed mice displayed significantly elevated relative abundance of Bacteroides sartorii, Bacteroides caecimuris, Akkermansia muciniphila and Bifidobacterium pseudolongum, taxa that have been reported to be strongly associated with favorable responses to immunotherapy. High-fiber fed mice also showed significantly reduced fractions of tumor-promoting genera such as Odoribacter and Alistipes. These effects were accompanied by widespread changes in the tumor immune microenvironment between fiber-rich and fiber-poor groups. Pectin-inulin fed mice displayed enhanced antitumor immune responses evident by remarkably increased fractions of B lineage cells, cDC1s and M1-likemacrophages and, conversely, reduced levels of activated cDC2s, M2 macrophages and polymorphonuclear myeloid-derived suppressor cells. Our findings inform on novel mechanisms by which dietary fiber robustly impacts gut consortia and immune milieu in the inhibition of LUAD. Our findings also suggest that the incorporation of dietary fiber in cancer treatment (e.g., immunotherapy) could improve outcomes for patients with LUAD. Citation Format: Manvi Sharma, Yuejiang Liu, Hannah Moreno, Inti C. Reischle, Mohamed A. Jamal, Tieling Zhou, Zahraa Rahal, Chidera O. Chukwuocha, Ke Liang, Robert R. Jenq, Matthew C. Ross, Kristi L. Hoffman, Humam Kadara. High-fiber diet induces favorable gut microbiota, reduces immunosuppression, and inhibits lung cancer development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6680.

Abstract 5373: Decoding the role of intrinsic pancreatic cellular signaling in shaping the immunosuppressive tumor microenvironment

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) has the highest mortality rate among major cancers, with over 50% of patients having liver metastases at diagnosis. Conventional T-cell-based immunotherapies are ineffective against PDAC liver metastases due to the intricate hepatic tumor microenvironment (TME) that hinders effective immune responses. Thus, it is vital to promote the influx of cytotoxic lymphocytes and prime antitumor immunity. PDAC cells exhibit plasticity and intrinsic cellular heterogeneity, leading to varying immune cell infiltrates and immune responses. Concurrently, early metastases to the liver create an immunosuppressive environment. Our study employs multiple PDAC models, originating from a congenic array of distinct PDAC cell clone tumors with varying degrees of T cell infiltration to delineate the signaling pathways that lead to immunosuppression in the pancreas and liver. Methods: The compendium of congenic PDAC murine cell clones mirrors immune heterogeneity observed in tumors, spanning from low to high T cell infiltration. To overcome a scarcity of tumor-specific neoepitopes in PDAC, we engineered PDAC cell clones expressing chicken ovalbumin (OVA) for antigen-specific T and B cell responses. By subcutaneous and intraportal vein injection of PDAC cell clones into mice, we induce primary pancreatic and metastatic liver tumors to explore immune phenotypes and assess anti-tumor adaptive immune responses, including myeloid and lymphoid cell subsets. Results: In vivo engraftment of PDAC clones showed varied CD4+/CD8+ T cells and polymorphonuclear myeloid-derived suppressor cells, accentuated with immunogenic OVA antigen expression. While all OVA+ PDAC lines elicited antigen-specific immune responses, only ‘TIL high’ tumors were eradicated, while ‘TIL low’ clones persisted in vivo. Additionally, ‘TIL low’ clones formed liver metastases upon intraportal injection, despite OVA expression. RNAseq unveiled differential expression in IL-1 family cytokines and receptors, chemokine-like factor gene superfamily, parathyroid hormone relevant function and metabolism. Current investigations include altering these pathways to re-program the tumor microenvironment and induce local immune suppression. Conclusion: Using diverse PDAC models, we created tumors with immune heterogeneity and altered transcriptional profiles. We identified validated differentially expressed immune altering cytokines, such as CXCL1 and CSF3, and potential novel IL-1 family genes and parathyroid signaling genes. The altered TME conferred protection against tumor antigen-specific immunity in certain clones, both in subcutaneous and liver metastasis models. Ongoing studies will assess the impact of these genes in the distinct environments, offering avenues for immunotherapeutic strategies targeting pancreatic cancer liver metastasis. Citation Format: Bushangqing Liu, Ethan Agritelley, Daniel Nussbaum, Junping Wei, Gangjun Lei, Melissa Gajda, Zachary Hartman. Decoding the role of intrinsic pancreatic cellular signaling in shaping the immunosuppressive tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5373.

Abstract 1382: Activation of the cGAS-STING pathway by large oncosomes induces type I IFN inflammation in mesenchymal stem cells that triggers an immunosuppressive phenotype in neutrophils

Abstract Extracellular vesicles (EVs) have been recognized as key players in cancer progression and metastasis, particularly large oncosomes (LO), secreted by invasive cancer cells, represent a distinct class of EVs with unique features. Previous research by the Di Vizio lab revealed LO's ability to alter recipient cell behavior, induce vascular morphogenesis, and carry cancer-specific biomolecules. Our preliminary studies point to a new mechanism of intercellular communication that involves the release of LO-containing DNA from PC cells. Notably, LO from prostate cancer exhibits enhanced potency in reprogramming bone marrow-derived mesenchymal stem cells (BM-MSCs) compared to exosomes (Exo) as observed by RNAseq. When evaluating the response to LO and Exo of BM-MSC, which are emerging as important drivers of bone metastasis, LO induces a robust inflammatory response, including metastasis-relevant chemokines and transcription factors involved in type I IFN response such as IRF7 and RASD2. Further, REACTOME pathway analysis of the differentially expressed genes revealed enrichment of the cGAS-STING pathway in BM-MSCs treated with LO, indicating a potential link between DNA/RNA sensors and the inflammatory response. BM cells isolated from WT and mutant Sting1gt/J mice demonstrated that up-regulation of IRF3 and IFNA1 genes induced by LO is inhibited when STING is absent. Suggesting that nucleic acid sensors engage in the LO-induced immune response in BM cells. Gene ontology analysis (GO) also identified several chemokines involved in neutrophil chemotaxis. In line with the observation from GO, neutrophil chemotaxis was significantly promoted by PC-derived LO-treated BM-MSC. Interestingly, human blood-derived neutrophils exposed to a conditioned medium from EVs-treated BM-MSC significantly increased the percentage of a population of LOX-1high and CD62Llow/− after 6h of culture. This was observed in concert with increased expression of Arginase1 and IL-10, suggesting their differentiation into polymorphonuclear-myeloid-derived suppressor cells (PMN-MDSC). An experimental orthotopic model using the breast cancer bone metastatic 4T1.2 cell line, with increased capacity to shed LO, demonstrated an increase in the presence of PMN-MDSC in the bone marrow of tumor-bearing mice in addition to a complete lack of lymphocyte populations, indicating their immunosuppressive activity that could lead to a pre-metastatic niche formation. This comprehensive study unveils the molecular pathways underlying the immune response to LO in the bone marrow, shedding light on mechanisms that could influence metastatic progression in prostate cancer. The findings underscore the unique role of LO in modulating the BM microenvironment, providing potential targets for therapeutic intervention and biomarkers for early disease detection. Citation Format: Taylon F. Silva, Diana Kitka, Blandine Victor, Chen Qian, Minhyung Kim, Tatyana Vagner, Giorgia Guerra, Catherine Grasso, Sungyong You, Fayyazz Sutterwala, Caroline Jefferies, Paola de Candia, Michael Freeman, Helen Goodridge, Karen Cavassani, Jlenia Guarnerio, Dolores Di Vizio. Activation of the cGAS-STING pathway by large oncosomes induces type I IFN inflammation in mesenchymal stem cells that triggers an immunosuppressive phenotype in neutrophils [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1382.

Abstract 5283: Polyamine blockade therapy: A strategy to block immunosuppression in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is lethal in 88% of patients and is characterized by a dense tumor microenvironment (TME) which impedes tumor entry of immune cells and delivery of therapeutics. Immunosuppressive myeloid populations of PDAC, including myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs), are known to not only support PDAC development but also impede the anti-tumor immune response elicited by therapeutic agents. To improve prognosis while maintaining tolerability, this study aims to target polyamine metabolism that is upregulated in the immunosuppressive myeloid populations and cancer cells to disrupt their contribution to PDAC progression and the immunosuppressive TME. We previously demonstrated that polyamine blockade therapy (PBT), via blocking biosynthesis with difluoromethylornithine (DFMO) and transport with a novel inhibitor (Trimer44NMe), elicits an anti-tumor response and improves median survival in PDAC engrafted immunocompetent mice. In the current study, PBT was found to lead to a selective reduction of the dominant MDSC subtype in PDAC, polymorphonuclear (PMN) MDSCs. Upon co-culturing of MDSCs with CD8+ T cells, PBT dampened MDSC-mediated suppression of T cell activity. These findings were corroborated by tracking Arginase 1, a driver of MDSC-mediated immunosuppression, which exhibited a significant decrease in response to PBT at both the activity and gene expression level. Ex-vivo generated M2 macrophages and TAMs treated with PBT also demonstrated a shift from the M2 pro-tumor phenotype towards the anti-tumor M1 macrophage phenotype. In summary, these findings support that PBT is effective at reducing myeloid-mediated immunosuppression through subtype specific modulation and supports the use of PBT for treatment of PDAC in combination with other immunomodulatory therapeutics. Citation Format: Joseph A. Goode. Polyamine blockade therapy: A strategy to block immunosuppression in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5283.

CD44 expression on murine hepatic stellate cells promotes the induction of monocytic and polymorphonuclear myeloid-derived suppressor cells.

In chronic inflammation regulatory immune cells, such as regulatory T cells and myeloid-derived suppressor cells (MDCS) can develop. Local signals in the inflamed tissue, such as cytokines and eicosanoids, but also contact dependent signals, can promote MDSC development. In the liver, hepatic stellate cells (HSC) may provide such signals via the expression of CD44. MDSC generated in the presence of HSC and anti-CD44 antibodies were functionally and phenotypically analyzed. We found that both monocytic (M-) and polymorphonuclear (PMN-) MDSC generated in the presence of αCD44 antibodies were less suppressive towards T cells as measured by T cell proliferation and cytokine production. Moreover, both M- and PMN- MDSC were phenotypically altered. M-MDSC mainly changed their expression of CD80 and CD39, PMN-MDSC showed altered expression of CD80/86, PD-L1 and CCR2. Moreover, both PMN- and M-MDSC lost expression of Nos2 mRNA, whereas M-MDSC showed reduced expression of TGFb mRNA and PMN-MDSC reduced expression of Il10 mRNA. In summary, the presence of CD44 on hepatic stellate cells promotes the induction of both M- and PMN-MDSC, although the mechanisms by which these MDSC may increase suppressive function due to interaction with CD44 is only partially overlapping.

Intratumoral injection of interferon gamma promotes the efficacy of anti-PD1 treatment in colorectal cancer

Immune checkpoint inhibitors (ICIs) offer new options for the treatment of patients with solid cancers worldwide. The majority of colorectal cancers (CRC) are proficient in mismatch-repair (pMMR) genes, harboring fewer tumor antigens and are insensitive to ICIs. These tumors are often found to be immune-deserted. We hypothesized that forcing immune cell infiltration into the tumor microenvironment followed by immune ignition by PD1 blockade may initiate a positive immune cycle that can boost antitumor immunity. Bioinformatics using a public database suggested that IFNγ was a key indicator of immune status and prognosis in CRC. Intratumoral administration of IFNγ increased immune cells infiltration into the tumor, but induced PD-L1 expression. A combined treatment strategy using IFNγ and anti-PD-1 antibody significantly increased T cell killing of tumor cells in vitro and showed synergistic inhibition of tumor growth in a mouse model of CRC. CyTOF found drastic changes in the immune microenvironment upon combined immunotherapy. Treatment with IFNγ and anti-PD1 antibody in CT26 tumors significantly increased infiltration of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). IFNγ had a more pronounced effect in decreasing intratumoral M2-like macrophages, while PD1 blockade increased the population of CD8+Ly6C + T cells in the tumor microenvironment, creating a more pro-inflammatory microenvironment. Additionally, PD1 induced increased expression of lymphocyte activating 3 (LAG3) in a significant fraction of CD8+ T cells and Treg cells, indicating potential drug resistance and feedback mechanisms. In conclusion, our work provides preclinical data for the Combined immunotherapy of CRC using intratumoral delivery of IFNγ and systemic anti-PD1 monoclonoal antibody.

Involvement of CX3CR1+ cells appearing in the abdominal cavity in the immunosuppressive environment immediately after gastric cancer surgery

BackgroundGastric cancer is primarily treated by surgery; however, little is known about the changes in the intraperitoneal immune environment and the prognostic impact of surgery. Surgical stress and cancer-associated inflammation cause immune cells to mobilize into the abdominal cavity via numerous cytokines. One such cytokine, CX3CR1, has various immune-related functions that remain to be fully explained. We characterized the intraperitoneal immune environment by investigating CX3CR1+ cells in intraperitoneal lavage fluid during gastric cancer surgery.MethodsLavage fluid samples were obtained from a total of 41 patients who underwent gastrectomy. The relative expression of various genes was analyzed using quantitative real-time PCR. The association of each gene expression with clinicopathological features and surgical outcomes was examined. The fraction of CX3CR1+ cells was analyzed by flow cytometry. Cytokine profiles in lavage fluid samples were investigated using a cytometric beads array.ResultsCX3CR1high patients exhibited higher levels of perioperative inflammation in blood tests and more recurrences than CX3CR1low patients. CX3CR1high patients tended to exhibit higher pathological T and N stage than CX3CR1low patients. CX3CR1 was primarily expressed on myeloid-derived suppressor cells and tumor-associated macrophages. In particular, polymorphonuclear myeloid-derived suppressor cells were associated with perioperative inflammation, pathological N, and recurrences. These immunosuppressive cells were associated with a trend toward unfavorable prognosis. Moreover, CX3CR1 expression was correlated with programmed death–1 expression.ConclusionsOur results suggest that CX3CR1+ cells are associated with an acute inflammatory response, tumor-promotion, and recurrence. CX3CR1 expression could be taken advantage of as a beneficial therapeutic target for improving immunosuppressive state in the future. In addition, analysis of intra-abdominal CX3CR1+ cells could be useful for characterizing the immune environment after gastric cancer surgery.