Suppressor Cell Research Articles

AB074. SOH24AB_235. Stromal cell-mediated immunosuppression: sialylated ligands as orchestrators of T cell and natural killer cell suppression in the tumour microenvironment of colorectal cancer

AB074. SOH24AB_235. Stromal cell-mediated immunosuppression: sialylated ligands as orchestrators of T cell and natural killer cell suppression in the tumour microenvironment of colorectal cancer

CD39 expression by regulatory T cells participates in CD8+ T cell suppression during experimental Trypanosoma cruzi infection.

An imbalance between suppressor and effector immune responses may preclude cure in chronic parasitic diseases. In the case of Trypanosoma cruzi infection, specialized regulatory Foxp3+ T (Treg) cells suppress protective type-1 effector responses. Herein, we investigated the kinetics and underlying mechanisms behind the regulation of protective parasite-specific CD8+ T cell immunity during acute T. cruzi infection. Using the DEREG mouse model, we found that Treg cells play a role during the initial stages after T. cruzi infection, restraining the magnitude of CD8+ T cell responses and parasite control. Early Treg cell depletion increased the frequencies of polyfunctional short-lived, effector T cell subsets, without affecting memory precursor cell formation or the expression of activation, exhaustion and functional markers. In addition, Treg cell depletion during early infection minimally affected the antigen-presenting cell response but it boosted CD4+ T cell responses before the development of anti-parasite effector CD8+ T cell immunity. Crucially, the absence of CD39 expression on Treg cells significantly bolstered effector parasite-specific CD8+ T cell responses, preventing increased parasite replication in T. cruzi infected mice adoptively transferred with Treg cells. Our work underscores the crucial role of Treg cells in regulating protective anti-parasite immunity and provides evidence that CD39 expression by Treg cells represents a key immunomodulatory mechanism in this infection model.

DNA-PK participates in pre-rRNA biogenesis independent of DNA double-strand break repair.

Although DNA-PK inhibitors (DNA-PK-i) have been applied in clinical trials for cancer treatment, the biomarkers and mechanism of action of DNA-PK-i in tumor cell suppression remain unclear. Here, we observed that a low dose of DNA-PK-i and PARP inhibitor (PARP-i) synthetically suppresses BRCA-deficient tumor cells without inducing DNA double-strand breaks (DSBs). Instead, we found that a fraction of DNA-PK localized inside of nucleoli, where we did not observe obvious DSBs. Moreover, the Ku proteins recognize pre-rRNA that facilitates DNA-PKcs autophosphorylation independent of DNA damage. Ribosomal proteins are also phosphorylated by DNA-PK, which regulates pre-rRNA biogenesis. In addition, DNA-PK-i acts together with PARP-i to suppress pre-rRNA biogenesis and tumor cell growth. Collectively, our studies reveal a DNA damage repair-independent role of DNA-PK-i in tumor suppression.

Alpha-lipoic acid ameliorates influenza A virus caused acute pneumonia though enhancement of anti-viral T cell immunity and suppression of macrophage activation by inhibiting ERK1/2 signaling pathway

The first outbreak of influenza A virus (IAV), which has been circulating for many decades, has resulted in serious morbidity and mortality. The IAV epidemic has caused serious damage to human life and the economy. Following an IAV infection, lymphatic cells immediately enter the lungs to clear the virus and eliminate damaged cells to maintain normal physiological mechanisms. In this study, we used alpha-lipoic acid (ALA), which has versatile antioxidant functions, as a target to treat and evaluate host antiviral effects and immune mechanisms. We observed that pre-treatment with ALA improved the survival rate and pathological state in a mouse model. A reduction in the inflammatory cytokine tumor necrosis factor-alpha was observed following in vivo experiments. It also increased the release of antiviral cytokines into the lungs by T lymphocytes. ALA pre-treatment effectively prevented acute pneumonia by modulating immune composition and contributing to virus clearance.

Tri-specific killer engager: unleashing multi-synergic power against cancer.

Cancer continues to be a global health concern, necessitating innovative solutions for treatment. Tri-specific killer engagers (TriKEs) have emerged as a promising class of immunotherapeutic agents, offering a multifaceted approach to cancer treatment. TriKEs simultaneously engage and activate natural killer (NK) cells while specifically targeting cancer cells, representing an outstanding advancement in immunotherapy. This review explores the generation and mechanisms of TriKEs, highlighting their advantages over other immunotherapies and discussing their potential impact on clinical trials and cancer treatment. TriKEs are composed of three distinct domains, primarily antibody-derived building blocks, linked together by short amino acid sequences. They incorporate critical elements, anti-cluster of differentiation 16 (CD16) and interleukin-15 (IL-15), which activate and enhance NK cell function, together with specific antibody to target each cancer. TriKEs exhibit remarkable potential in preclinical and early clinical studies across various cancer types, making them a versatile tool in cancer immunotherapy. Comparative analyses with other immunotherapies, such as chimeric antigen receptor-T (CAR-T) cell therapy, immune checkpoint inhibitors (ICIs), cytokine therapies, and monoclonal antibodies (mAbs), reveal the unique advantages of TriKEs. They offer a safer pathway for immunotherapy by targeting cancer cells without hyperactivating T cells, reducing off-target effects and complications. The future of TriKEs involves addressing challenges related to dosing, tumor-associated antigen (TAA) expression, and NK cell suppression. Researchers are exploring innovative dosing strategies, enhancing specificity through tumor-specific antigens (TSAs), and combining TriKEs with other therapies for increased efficacy.

The C1q and gC1qR axis as a novel checkpoint inhibitor in cancer.

Understanding at the molecular level of the cell biology of tumors has led to significant treatment advances in the past. Despite such advances however, development of therapy resistance and tumor recurrence are still unresolved major challenges. This therefore underscores the need to identify novel tumor targets and develop corresponding therapies to supplement existing biologic and cytotoxic approaches so that a deeper and more sustained treatment responses could be achieved. The complement system is emerging as a potential novel target for cancer therapy. Data accumulated to date show that complement proteins, and in particular C1q and its receptors cC1qR/CR and gC1qR/p33/HABP1, are overexpressed in most cancer cells and together are involved not only in shaping the inflammatory tumor microenvironment, but also in the regulation of angiogenesis, metastasis, and cell proliferation. In addition to the soluble form of C1q that is found in plasma, the C1q molecule is also found anchored on the cell membrane of monocytes, macrophages, dendritic cells, and cancer cells, via a 22aa long leader peptide found only in the A-chain. This orientation leaves its 6 globular heads exposed outwardly and thus available for high affinity binding to a wide range of molecular ligands that enhance tumor cell survival, migration, and proliferation. Similarly, the gC1qR molecule is not only overexpressed in most cancer types but is also released into the microenvironment where it has been shown to be associated with cancer cell proliferation and metastasis by activation of the complement and kinin systems. Co-culture of either T cells or cancer cells with purified C1q or anti-gC1qR has been shown to induce an anti-proliferative response. It is therefore postulated that in the tumor microenvironment, the interaction between C1q expressing cancer cells and gC1qR bearing cytotoxic T cells results in T cell suppression in a manner akin to the PD-L1 and PD-1 interaction.

Irreversible electroporation promotes a pro-inflammatory tumor microenvironment and anti-tumor immunity in a mouse pancreatic cancer model.

Pancreatic cancer is a significant cause of cancer-related mortality and often presents with limited treatment options. Pancreatic tumors are also notorious for their immunosuppressive microenvironment. Irreversible electroporation (IRE) is a non-thermal tumor ablation modality that employs high-voltage microsecond pulses to transiently permeabilize cell membranes, ultimately inducing cell death. However, the understanding of IRE's impact beyond the initiation of focal cell death in tumor tissue remains limited. In this study, we demonstrate that IRE triggers a unique mix of cell death pathways and orchestrates a shift in the local tumor microenvironment driven, in part, by reducing the myeloid-derived suppressor cell (MDSC) and regulatory T cell populations and increasing cytotoxic T lymphocytes and neutrophils. We further show that IRE drives induce cell cycle arrest at the G0/G1 phase in vitro and promote inflammatory cell death pathways consistent with pyroptosis and programmed necrosis in vivo. IRE-treated mice exhibited a substantial extension in progression-free survival. However, within a span of 14 days, the tumor immune cell populations reverted to their pre-treatment composition, which resulted in an attenuation of the systemic immune response targeting contralateral tumors and ultimately resulting in tumor regrowth. Mechanistically, we show that IRE augments IFN-γ signaling, resulting in the up-regulation of the PD-L1 checkpoint in pancreatic cancer cells. Together, these findings shed light on potential mechanisms of tumor regrowth following IRE treatment and offer insights into co-therapeutic targets to improve treatment strategies.

Early Detection of Myeloid-Derived Suppressor Cells in the Lung Pre-Metastatic Niche by Shortwave Infrared Nanoprobes.

Metastatic breast cancer remains a significant source of mortality amongst breast cancer patients and is generally considered incurable in part due to the difficulty in detection of early micro-metastases. The pre-metastatic niche (PMN) is a tissue microenvironment that has undergone changes to support the colonization and growth of circulating tumor cells, a key component of which is the myeloid-derived suppressor cell (MDSC). Therefore, the MDSC has been identified as a potential biomarker for PMN formation, the detection of which would enable clinicians to proactively treat metastases. However, there is currently no technology capable of the in situ detection of MDSCs available in the clinic. Here, we propose the use of shortwave infrared-emitting nanoprobes for the tracking of MDSCs and identification of the PMN. Our rare-earth albumin nanocomposites (ReANCs) are engineered to bind the Gr-1 surface marker of murine MDSCs. When delivered intravenously in murine models of breast cancer with high rates of metastasis, the targeted ReANCs demonstrated an increase in localization to the lungs in comparison to control ReANCs. However, no difference was seen in the model with slower rates of metastasis. This highlights the potential utility of MDSC-targeted nanoprobes to assess PMN development and prognosticate disease progression.

An Integrative Study of Scrophularia takesimensis Nakai in an Ovalbumin-Induced Murine Model of Asthma: The Effect on T Helper 2 Cell Activation.

Scrophularia have traditionally been used as herbal medicines to treat neuritis, sore throats, and laryngitis. In particular, S. takesimensis, a Korean endemic species with restricted distribution on Ulleung Island, holds significant resource and genetic value. However, its pharmacological properties have not been thoroughly evaluated. Thus, we provide detailed morphological characteristics and genomic information for S. takesimensis in this study. Moreover, its pharmacological activity was evaluated in an ovalbumin-induced asthma rat model, using extracts of S. takesimensis roots (100 or 200 mg/kg). The distinguishing features of S. takesimensis from related species include the presence or absence of stem wings, leaf shape, and habitat. The chloroplast (cp) genome of this species is 152,420 bp long and exhibits a conserved quadripartite structure. A total of 114 genes were identified, which included 80 protein-coding genes, 30 transfer RNA (tRNA) genes, and 4 ribosomal RNA (rRNA) genes. The gene order, content, and orientation of the S. takesimensis cp genome was highly conserved and consistent with the general structure observed in S. buergeriana and S. ningpoensis cp genomes. Confirming the anti-inflammatory effects of S. takesimensis extract (STE) using an established mouse model of ovalbumin-induced asthma, we observed reduced asthmatic phenotypes, including inflammatory cell infiltration, mucus production, and suppression of T helper 2 (Th2) cell. Furthermore, STE treatment reduced Th2 cell activation and differentiation. This study underscores the medicinal value of S. takesimensis. The importance of preserving S. takesimensis was revealed and crucial insights were provided for further research on its utilization as a medicinal resource.

Biomimetic MDSCs membrane coated black phosphorus nanosheets system for photothermal therapy/photodynamic therapy synergized chemotherapy of cancer

Photothermal therapy is favored by cancer researchers due to its advantages such as controllable initiation, direct killing and immune promotion. However, the low enrichment efficiency of photosensitizer in tumor site and the limited effect of single use limits the further development of photothermal therapy. Herein, a photo-responsive multifunctional nanosystem was designed for cancer therapy, in which myeloid-derived suppressor cell (MDSC) membrane vesicle encapsulated decitabine-loaded black phosphorous (BP) nanosheets (BP@ Decitabine @MDSCs, named BDM). The BDM demonstrated excellent biosafety and biochemical characteristics, providing a suitable microenvironment for cancer cell killing. First, the BDM achieves the ability to be highly enriched at tumor sites by inheriting the ability of MDSCs to actively target tumor microenvironment. And then, BP nanosheets achieves hyperthermia and induces mitochondrial damage by its photothermal and photodynamic properties, which enhancing anti-tumor immunity mediated by immunogenic cell death (ICD). Meanwhile, intra-tumoral release of decitabine induced G2/M cell cycle arrest, further promoting tumor cell apoptosis. In vivo, the BMD showed significant inhibition of tumor growth with down-regulation of PCNA expression and increased expression of high mobility group B1 (HMGB1), calreticulin (CRT) and caspase 3. Flow cytometry revealed significantly decreased infiltration of MDSCs and M2-macrophages along with an increased proportion of CD4+, CD8+ T cells as well as CD103+ DCs, suggesting a potentiated anti-tumor immune response. In summary, BDM realizes photothermal therapy/photodynamic therapy synergized chemotherapy for cancer.

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.

Platelet-derived TGF-β1 induces functional reprogramming of myeloid-derived suppressor cells in immune thrombocytopenia

AbstractPlatelet α-granules are rich in transforming growth factor β1 (TGF-β1), which is associated with myeloid-derived suppressor cell (MDSC) biology. Responders to thrombopoietin receptor agonists (TPO-RAs) revealed a parallel increase in the number of both platelets and MDSCs. Here, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient mice to establish an active murine model of immune thrombocytopenia (ITP). Subsequently, we demonstrated that TPO-RAs augmented the inhibitory activities of MDSCs by arresting plasma cells differentiation, reducing Fas ligand expression on cytotoxic T cells, and rebalancing T-cell subsets. Mechanistically, transcriptome analysis confirmed the participation of TGF-β/Smad pathways in TPO-RA–corrected MDSCs, which was offset by Smad2/3 knockdown. In platelet TGF-β1–deficient mice, TPO-RA-induced amplification and enhanced suppressive capacity of MDSCs was waived. Furthermore, our retrospective data revealed that patients with ITP achieving complete platelet response showed superior long-term outcomes compared with those who only reach partial response. In conclusion, we demonstrate that platelet TGF-β1 induces the expansion and functional reprogramming of MDSCs via the TGF-β/Smad pathway. These data indicate that platelet recovery not only serves as an end point of treatment response but also paves the way for immune homeostasis in immune-mediated thrombocytopenia.

B7-H3 Expression in Breast Cancer and Brain Metastasis.

Brain metastasis is a significant challenge for some breast cancer patients, marked by its aggressive nature, limited treatment options, and poor clinical outcomes. Immunotherapies have emerged as a promising avenue for brain metastasis treatment. B7-H3 (CD276) is an immune checkpoint molecule involved in T cell suppression, which is associated with poor survival in cancer patients. Given the increasing number of clinical trials using B7-H3 targeting CAR T cell therapies, we examined B7-H3 expression across breast cancer subtypes and in breast cancer brain metastases to assess its potential as an interventional target. B7-H3 expression was investigated using immunohistochemistry on tissue microarrays of three clinical cohorts: (i) unselected primary breast cancers (n = 347); (ii) brain metastatic breast cancers (n = 61) and breast cancer brain metastases (n = 80, including a subset of 53 patient-matched breast and brain metastasis cases); and (iii) mixed brain metastases from a range of primary tumours (n = 137). In primary breast cancers, B7-H3 expression significantly correlated with higher tumour grades and aggressive breast cancer subtypes, as well as poorer 5-year survival outcomes. Subcellular localisation of B7-H3 impacted breast cancer-specific survival, with cytoplasmic staining also correlating with a poorer outcome. Its expression was frequently detected in brain metastases from breast cancers, with up to 90% expressing B7-H3. However, not all brain metastases showed high levels of expression, with those from colorectal and renal tumours showing a low frequency of B7-H3 expression (0/14 and 2/16, respectively). The prevalence of B7-H3 expression in breast cancers and breast cancer brain metastases indicates potential opportunities for B7-H3 targeted therapies in breast cancer management.

YAP/TAZ-TEAD signalling axis: A new therapeutic target in malignant pleural mesothelioma.

The Hippo signalling pathway, a highly conserved signalling cassette, regulates organ size by controlling cell growth, apoptosis and stem cell self-renewal. The tumourigenic potential of this pathway is largely attributed to the activity of YAP/TAZ, which activate the TEAD1-4 transcription factors, leading to the expression of genes involved in cell proliferation and suppression of cell death. Aberrant regulation of the YAP/TAZ-TEAD signalling axis is commonly observed in malignant pleural mesothelioma (MPM), an insidious neoplasm of the pleural tissue that lines the chest cavity and covers the lungs with poor prognosis. Given the limited effectiveness of current treatments, targeting the YAP/TAZ-TEAD signalling cascade has emerged as a promising therapeutic strategy in MPM. Several inhibitors of the YAP/TAZ-TEAD signalling axis are presently undergoing clinical development, with the goal of advancing them to clinical use in the near future.

Myeloid-derived suppressor cell mitochondrial fitness governs chemotherapeutic efficacy in hematologic malignancies

Myeloid derived suppressor cells (MDSCs) are key regulators of immune responses and correlate with poor outcomes in hematologic malignancies. Here, we identify that MDSC mitochondrial fitness controls the efficacy of doxorubicin chemotherapy in a preclinical lymphoma model. Mechanistically, we show that triggering STAT3 signaling via β2-adrenergic receptor (β2-AR) activation leads to improved MDSC function through metabolic reprograming, marked by sustained mitochondrial respiration and higher ATP generation which reduces AMPK signaling, altering energy metabolism. Furthermore, induced STAT3 signaling in MDSCs enhances glutamine consumption via the TCA cycle. Metabolized glutamine generates itaconate which downregulates mitochondrial reactive oxygen species via regulation of Nrf2 and the oxidative stress response, enhancing MDSC survival. Using β2-AR blockade, we target the STAT3 pathway and ATP and itaconate metabolism, disrupting ATP generation by the electron transport chain and decreasing itaconate generation causing diminished MDSC mitochondrial fitness. This disruption increases the response to doxorubicin and could be tested clinically.

Bioinformatics-based screening and analysis of the key genes involved in the influence of antiangiogenesis on myeloid-derived suppressor cells and their effects on the immune microenvironment.

This study aimed to screen differentially expressed genes (DEGs) involved in the influence of antiangiogenic therapy on myeloid-derived suppressor cell (MDSC) infiltration and investigate their mechanisms of action. Data on DEGs after the action of antiangiogenic drugs in a pan-cancer context were obtained from the Gene Expression Omnibus (GEO) database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the clusterProfiler package in R software. Single-sample gene set enrichment analysis was performed using the gene set variation analysis package to evaluate the levels of immune cells and the activity of immune-related pathways. The relationships of DEGs with the infiltration levels of MDSCs and specific immune cell subpopulations were investigated via gene module analysis. The top 10 key genes were subsequently obtained from PPI network analysis using the cytoHubba plugin of the Cytoscape platform. When the DEGs of the four datasets were intersected, a DEG in the intersection of three datasets and 12 DEGs in the intersection of two datasets were upregulated, and 28 DEGs in the intersection of two datasets were downregulated. GO and KEGG pathway enrichment analyses revealed that the DEGs were associated with multiple important signaling pathways closely related to tumor onset and development, including cell differentiation, cell proliferation, the cell cycle, and immune responses. Most downregulated genes in lung adenocarcinoma (LUAD) were positively correlated with MDSC expression. Only MGP was negatively correlated; the correlation between CACNG6 and MDSC expression was statistically insignificant. In lung squamous cell carcinoma (LUSC), the relationships of PMEPA1, PCDH7, NEURL1B, and CACNG6 with MDSC expression were statistically insignificant; MGP was negatively correlated with MDSC expression. The top 10 key genes with the highest degree scores obtained using the cytoHubba plugin of Cytoscape were AURKB, RRM2, BUB1, NUSAP1, PRC1, TOP2A, NCAPH, CENPA, KIF2C, and CCNA2. Most of these genes were upregulated in LUAD and associated with immune cell infiltration and prognosis in tumors. An analysis of the relationships between DEGs and infiltration by other specific immune cells revealed the presence of consistent patterns in the downregulated genes, which exhibited positive correlations with the levels of Th2 cells, γδ T cells, and CD56dim NK cells, and negative correlations with other infiltrating immune cells. Antiangiogenic therapy may regulate MDSC infiltration through multiple important signaling pathways closely associated with tumor onset and development, such as cell differentiation, cell proliferation, the cell cycle, and immune responses. Antiangiogenic drugs may exert effects by affecting various types of infiltrating cells associated with immune suppression.

Finding ε and δ of Traditional Disclosure Control Systems

This paper analyzes the privacy of traditional Statistical Disclosure Control (SDC) systems under a differential privacy interpretation. SDCs, such as cell suppression and swapping, promise to safeguard the confidentiality of data and are routinely adopted in data analyses with profound societal and economic impacts. Through a formal analysis and empirical evaluation of demographic data from real households in the U.S., the paper shows that widely adopted SDC systems not only induce vastly larger privacy losses than classical differential privacy mechanisms, but, they may also come at a cost of larger accuracy and fairness.

Abstract 7540: Impact of IL-2 and IL-7 on human regulatory T cell suppression and pembrolizumab-mediated reversal of human T cell exhaustion

Abstract Inhibitory pathways within the tumour microenvironment limit the anti-cancer immune response. Two central mechanisms limiting the T cell response in the tumour are suppression of effector T cells responses by regulatory T cells, and chronic exposure to tumour antigens that may bestow T cell unresponsiveness or exhaustion. Restoring exhausted T cell responsiveness through blockade of inhibitory immune checkpoints such as the PD-1/PDL-1 interaction is an established therapeutic modality leading to durable responses and improved survival rates in some patients.We have modelled suppressive mechanisms in vitro using purified human T cells and investigated the impact of the cytokines IL-2 and IL-7. A comparison of in vitro assay systems for T cell exhaustion including T cell/allogeneic dendritic cells, a recall response to a viral antigen, prolonged stimulation of T cells to generate an ‘exhausted’ phenotype followed by a secondary stimulation with allogeneic DCs, revealed in some donors, the greatest impact of pembrolizumab was with exhausted T cells, a finding consistent with our studies using a dissociated tumour cell response with primary cells from patients with lung or colon carcinomas. Quantifying a range of cytokines (e.g. IFNγ, TNFα and IL-10) and flow cytometry activation markers (e,g, CD69, CD25, CD71, OX40 and CD137) established that in general pembrolizumab was effective at restoring the IFNγ response, although some donors were not responsive, and there was a more modest impact on other readouts indicating not all T cell functionality is restored. We therefore tested the impact of IL-2 and IL-7 on the reversal of the ‘exhausted’ phenotype and identified further improved functionality and donor responsiveness. We subsequently tested the impact of these cytokines in another ‘inhibitory’ context, that of regulatory T cell suppression; we identified that high-levels of IL-2 overcame regulatory T cell suppression and IL-7 led to an overall enhancement of response.These findings highlight how multiple suppressive mechanisms may need to be overcome to maximally restore anti-cancer immune responses, and that the combination of cytokines, such as IL-2 and IL-7, and checkpoint inhibitors, such as pembrolizumab, may enhance T cell responses. Citation Format: Gokhan Tut, Neale Harrison, Leila Sallie, Emma Welsh, Ashley Pegg, Arshpreet Kaur, Zhi Li, Ines Morano, Hujo Chan, Jamie Cowley, Catherine Brady, John Gordon, Mark Bryant, Omar Qureshi, Nicholas M. Barnes. Impact of IL-2 and IL-7 on human regulatory T cell suppression and pembrolizumab-mediated reversal of human T cell exhaustion [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 7540.

Abstract 5287: Ex vivo pharmacologic inhibition of STAT3 effectively targets tumor and tumor associated suppressor cells in high-grade glioma 3D spheroids

Abstract Gliomas, a type of brain tumor originating from glial cells, comprise a heterogenous group of neoplasms. High-grade gliomas, in particular, present significant therapeutic challenges in the clinic. Unlike other solid tumors, the heterogenous glioma microenvironment is heavily enriched with tumor associated suppressor cells including myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs), which can account for 30-40% of the cellular composition1. These pro-tumorigenic myeloid cells are thought to contribute to the resistance of glioma to immunotherapy. Efforts to target the suppressive nature of these dominating cell types are in development to yield more therapeutic options for patients with these devastating diseases. Constitutive activation of STAT3 in gliomas has been associated with increased tumor progression and reduced immune response. We have observed in other cancer models that a phenotypic switch occurs from STAT3 pathway activation in 3D spheroid culture to STAT3 inactivation when cultured in 2D. Therefore, we sought to determine the role of STAT3 activation and its role in the interplay between glioma and their immune suppressive environment using a 3D spheroid model. We modified our commercially available test platform, 3D-Predict™ Glioma, such that it is conducive to monitoring immune cell function. Newly diagnosed treatment naive primary samples from HGG patients were dissociated and cryogenically preserved and banked. Samples were profiled for the abundance of tumor associated suppressive myeloid cells using flow cytometry. We determined that relative proportions of tumor suppressor cells were detectable and varied across HGG primary patient samples with TAMs being the predominate immune cell type identified. Pro-tumorigenic TAM markers including CD163 and CD206 were correlated with temozolomide response and were associated with poor patient prognosis. When we evaluated the role of p-STAT in HGG primary samples, p-STAT was detected at baseline and abundance was related back to the presence of tumor associated immune suppressor cells. The impact of STAT3 signaling blockade by the inhibitor WP1066 was determined ex vivo, and efficacy was related back to MGMT promotor methylation status and patient clinical outcome. We detected shifts in cytokine signatures following treatment of HGG 3D spheroid models with WP1066 which are known to target tumor associated suppressor cell functions. This work demonstrates the critical role suppressive immune cells play in HGG clinical response. Given p-STAT can be altered in 2D culture compared to 3D culture, ex vivo therapeutic response profiling of HGG samples is necessary using the more physiologically relevant spheroid culture model. 1.Hambardzumyan et al. The role of microglia and macrophages in glioma maintenance and progression. Nat. Neurosci. 19, 20-27 (2016). Citation Format: Katy A. Lassahn, Ashley K. Elrod, Teresa M. DesRochers, Kathryn M. Appleton. Ex vivo pharmacologic inhibition of STAT3 effectively targets tumor and tumor associated suppressor cells in high-grade glioma 3D spheroids [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 5287.

Abstract 3037: Sex-specific differences in Yap1 and Cd276 function and expression regulate medulloblastoma progression and immune evasion

Abstract Unveiling the molecular mechanisms underlying sex-specific differences in cancer initiation, progression and treatment outcomes will provide novel insights that will advance cancer research and clinical care. This study highlights an unexpected, sex-biased role of the oncogene Yap1 in SHH medulloblastoma (MB). We discovered that Yap1 deletion in SmoM2-driven SHH MB significantly prolongs survival in male but not female mice. Using an integrated multi-omics approach, we show that YAP1 promotes cancer stem cell maintenance through concurrent transcriptional activation of stemness genes, such as Sox2, and repression of differentiation genes such as NeuroD1 and Zic1/2. Interestingly, while Yap1 is essential for maintaining cancer stem cells in both sexes, it plays a more critical role in immune evasion in males. Specifically, YAP1 regulates the expression of an immune checkpoint molecule Cd276 to suppress T cell function. Blocking CD276 or deleting Yap1 is sufficient to significantly reverse T cell suppression in males but not females. Furthermore, YAP1 direct targets of transcriptional regulation, including CD276, predicts survival in male but not female patients across multiple human cancers, suggesting that our findings have broader implications beyond medulloblastomas and is conserved across species. This study provides compelling evidence for male-biased susceptibility to Yap1 inhibition and uncovers the YAP1-CD276 axis as a sexually diverse pathway in T cell suppression in tumors. Citation Format: Nourhan Abdelfattah, Sivaraman Natarajan, Han Nhat Tran, Jose Maldonado, Rachael McMinimy, Hannah Borland, Shu-hsia Chen, Fernando Camargo, James Olson, Joshy George, Kyuson Yun. Sex-specific differences in Yap1 and Cd276 function and expression regulate medulloblastoma progression and immune evasion [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 3037.