Expression Of Immunosuppressive Genes Research Articles

Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression.

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

Abstract 3926: ARF6-dependent endocytic trafficking of the interferon-gamma receptor drives adaptive immune resistance and response to immune checkpoint blockade

Abstract Interferon-gamma (IFNγ)-driven adaptive immune resistance (AIR) in cancer begins at the plasma membrane where cytokine signaling is initiated. Cytotoxic CD8+ T cells secrete IFNγ, eliciting tumor-intrinsic IFNγ signaling and expression of immunosuppressive genes, which are critical for effective therapeutic response to anti-PD-1 and anti-CTLA-4 immune checkpoint blockade (ICB). Although the IFNγ receptor (IFNγR) is expressed in all cell types, its surface density can determine a cell’s responsiveness to ligand. Mechanistic control over this process remains a mystery. Herein we report that the endocytic trafficking protein ADP-Ribosylation Factor 6 (ARF6) is critical for IFNγ-driven AIR during primary tumor progression and in the setting of ICB therapy. The IFNγR1 subunit of the receptor is constitutively internalized in a ligand-independent manner. ARF6 is necessary for endocytic recycling of IFNγR1 and determines the steady-state surface density of the receptor. Loss of ARF6 results in lysosomal degradation of the receptor and controls IFNγR1 protein levels in melanoma, non-small cell lung cancer, colorectal cancer, and triple-negative breast cancer. IFNγ activates ARF6 in parallel with JAK1-STAT1 signaling, suggesting a positive feedback loop that allows tumor cells to dynamically respond to immune attack. Silencing ARF6 reduces tumor intrinsic IFNγ signaling and downstream expression of immunosuppressive genes. In murine melanoma, loss of ARF6 causes resistance to systemic ICB therapy. Likewise, low expression of ARF6 in patient tumors correlates with inferior outcomes with ICB. Our data provide new mechanistic insights into tumor immune escape, defined by ARF6-dependent adaptive immunity, and support that ARF6-dependent endomembrane trafficking of the IFNγ receptor shapes clinical outcomes of ICB therapy. Private Information Citation Format: Yinshen Wee, Junhua Wang, Emily C. Wilson, Coulson P. Rich, Aaron Rogers, Zhongzong Tong, Evelyn DeGroot, Y.N. Vashisht Gopal, Michael Davies, Huseyin Atakan Ekiz, Joshua K.H. Tay, Chris Stubben, Kenneth M. Boucher, Juan M. Oviedo, Keke C. Fairfax, Matthew A. Williams, Sheri L. Holmen, Roger K. Wolff, Allie H. Grossmann. ARF6-dependent endocytic trafficking of the interferon-gamma receptor drives adaptive immune resistance and response to immune checkpoint blockade [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 3926.

Abstract 5261: Immunologic signatures of peripheral blood cells in patients with advanced pancreatic cancer under lenvatinib-pembrolizumab maintenance therapy

Abstract Background: The treatment of pancreatic cancer is limited by chemotherapy toxicities which impacts quality of life. This is a phase 2 clinical trial of lenvatinib and pembrolizumab as maintenance therapy in patients with advanced pancreatic cancer. We observed preclinical activity of this combination in pancreatic mouse models. We hypothesize that this combination may address unmet needs to minimize toxicities associated with standard treatments, stimulate anti-tumor T cell immunity, and improve the progression free and overall survival. Exploratory studies aim to characterize immune-related systemic changes in peripheral blood over the course of therapy and to identify global changes in expression of tumor-related genes in needle biopsy samples of liver metastatic lesions. Methods: Multiplex gene expression analysis of unsorted peripheral blood mononuclear cells (PBMC) was performed using PanCancer Immune Profiling Panel on NanoString nCounter platform. PBMC samples from pre- through week 32 of treatment were assessed for differential expression of 730 immune profiling genes defining T cell functions and associated immune categories. Results: PBMC immune profiling from 4/5 patients show a distinctive pattern of increased activation of T cells during the first 9 weeks of treatment followed by a sharp inhibition starting at weeks 9-12 after 3-4 cycles of treatment (CD3E, CD247, LCK, TBX1, TCF7, STAT4, IL2RG). Subsequent upregulation of macrophage-derived scavenger, inflammatory, and immunosuppressive gene expression patterns continued for the remainder of treatment (CD14, MSR1, MARCO, CD68, TGFB1, IL10RA). The median PFS of first 10 patients was 21.5 (9-32) weeks. Conclusions: Immunotherapy resistance may be related to rapidly developing terminal differentiation and unresponsiveness of T cells in parallel with upregulation of macrophage-derived inflammatory and immunosuppressive processes. Studies are on-going to prevent inhibition of the T-cells. Citation Format: Vincent Chung, Ferdynand Kos, Edwin Manual, Shannon Dempsey, Don J. Diamond. Immunologic signatures of peripheral blood cells in patients with advanced pancreatic cancer under lenvatinib-pembrolizumab maintenance therapy [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 5261.

Identifying immune-related prognostic biomarkers in osteosarcoma: Development and validation of the tumor immune microenvironment risk model based on analysis of TCGA.

Osteosarcoma is a rare and aggressive malignancy with limited effective therapeutic options. This study aimed to identify immune-related prognostic biomarkers and develop a prognostic model for osteosarcoma. We performed integrated analysis of transcriptomic data and immune cell infiltration profiles of 84 osteosarcoma samples from the Cancer Genome Atlas (TCGA) database. Time-dependent receiver operating characteristic (ROC) curve analysis was used to assess the prognostic value of the TIMErisk model. We also performed functional annotation and pathway enrichment analyses to explore the potential mechanisms underlying the TIMErisk model. We identified a seven-gene TIMErisk model (C2, APBB1IP, BST2, TRPV2, CCL5, GBP1, and F13A1) that was independently associated with overall survival of osteosarcoma patients. The TIMErisk model showed significant associations with immune cell infiltration and immunosuppressive gene expression. In addition, the TIMErisk model was associated with drug sensitivity, and we found that several immune checkpoint genes were significantly differentially expressed between high- and low-TIMErisk groups. Functional annotation and pathway enrichment analyses revealed that the TIMErisk model was associated with multiple immune-related pathways, including antigen processing and presentation, cytokine-cytokine receptor interaction, and T cell receptor signaling pathway. Our study identified a novel TIME-based prognostic model for osteosarcoma that incorporates immune-related genes and can be used to predict patient prognosis and response to immunotherapy. Our findings highlight the importance of the TIME microenvironment in osteosarcoma progression and suggest that immune-related biomarkers may have clinical significance in the management of osteosarcoma.

Comprehensive single-cell analysis demonstrates radiotherapy-induced infiltration of macrophages expressing immunosuppressive genes into tumor in esophageal squamous cell carcinoma

Radiotherapy (RT) combined with immunotherapy is promising; however, the immune response signature in the clinical setting after RT remains unclear. Here, by integrative spatial and single-cell analyses using multiplex immunostaining (CODEX), spatial transcriptome (VISIUM), and single-cell RNA sequencing, we substantiated the infiltration of immune cells into tumors with dynamic changes in immunostimulatory and immunosuppressive gene expression after RT. In addition, our comprehensive analysis uncovered time- and cell type–dependent alterations in the gene expression profile after RT. Furthermore, myeloid cells showed prominent up-regulation of immune response–associated genes after RT. Notably, a subset of infiltrating tumor-associated myeloid cells showing PD-L1 positivity exhibited significant up-regulation of immunostimulatory (HMGB1 and ISG15), immunosuppressive (SIRPA and IDO1), and protumor genes (CXCL8, CCL3, IL-6, and IL-1AB), which can be targets of immunotherapy in combination with PD-L1. These datasets will provide information on the RT-induced gene signature to seek an appropriate target for personalized immunotherapy combined with RT and guide the timing of combination therapy.

LMAP-07 POTENTIAL MECHANISM OF IMMUNE ESCAPE RELATED TO TUMOR-ASSOCIATED MACROPHAGE IN GLIOBLASTOMA AFTER COMBINED THERAPY WITH RADIOTHERAPY AND IMMUNE CHECKPOINT BLOCKER

Abstract Immune checkpoint blockers (ICBs) have revolutionized the treatment of cancer. Radiotherapy (RT) has been demonstrated to increase the survival benefit of ICBs in some cancers through its local and systemic immunomodulation, although its efficacy in glioblastoma (GBM) is very limited. With a thorough investigation of the immune responses to single and dual treatment utilizing single-cell RNA-seq analyses on the synergy of RT and anti-PD-L1 antibody (aPD-L1), we studied the potential mechanism of immune escape in GBM even when RT and ICB are combined. Our findings demonstrated a statistically significant longer survival of mice treated with RT and aPD-L1 combined than either single modality of treatment in an orthotopic syngeneic GBM model achieving a 70% cure rate. In the tumor tissues collected from the mouse brain that failed dual treatment, i.e., immune escaped, immune cell profiling still demonstrated much lower T regulatory cells and higher CD8+ cytotoxic T cells infiltrated to tumor, and elevated CD8+/CD4+ and CD8+/Treg ratios in the dual therapy group compared to single therapies, as expected with synergistic effects of dual treatment. RT with aPD-L1 markedly reduced CD8+ and CD4+ T exhaustion cells and elevated T-memory cells in comparison to single modality groups. Nevertheless, compared to the RT alone or no treatment control group, dual therapy failed to decrease the proportion of Arginase1-positive glioma-associated macrophages (GAM) in macrophage/monocytes in tumor microenvironment, which were considerably increased if treated with aPD-L1 only. Moreover, the combination of RT with aPD-L1 did not alter immunosuppressive gene expression in the macrophage/monocyte groups. In conclusion, our research demonstrated that RT and aPD-L1 together may elicit a potent and durable antitumor immune response in the GBM mouse model through regulating lymphocytes but not macrophages. Our findings point to the urgent need for research into GAM-modulating drug and their potential to prevent immunological escape.

Triple negative breast cancer: Immunogenicity, tumor microenvironment, and immunotherapy.

Triple negative breast cancer (TNBC) is a biologically diverse subtype of breast cancer characterized by genomic and transcriptional heterogeneity and exhibiting aggressive clinical behaviour and poor prognosis. In recent years, emphasis has been placed on the identification of mechanisms underlying the complex genomic and biological profile of TNBC, aiming to tailor treatment strategies. High immunogenicity, specific immune activation signatures, higher expression of immunosuppressive genes and higher levels of stromal Tumor Infiltrating Lymphocytes, constitute some of the key elements of the immune driven landscape associated with TNBC. The unprecedented response of TNBC to immunotherapy has undoubtedly changed the standard of care in this disease both in the early and the metastatic setting. However, the extent of interplay between immune infiltration and mutational signatures in TNBC is yet to be fully unravelled. In the present review, we present clinical evidence on the immunogenicity and tumour microenvironment influence on TNBC progression and the current treatment paradigms in TNBC based on immunotherapy.

Kaposi's sarcoma-associated herpesvirus replication and transcription activator protein activates CD274/PD-L1 gene promoter.

Kaposi's sarcoma-associated herpesvirus (KSHV) is responsible for the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. The expression of immunosuppressive genes, such as IL-10 and CD274/PD-L1 is observed during KSHV-associated pathogenesis, and the modulation of the host immune system by KSHV contributes to establishing viral persistence in the host. Understanding the mechanism that allows the virus to evade host cell immunity would be helpful in order to develop therapeutic strategies for KSHV malignancy. In this study, we show that KSHV replication and transcriptional activator (K-RTA), an essential activator of the viral lytic cycle, transactivates the CD274/PD-L1 gene promoter. Mechanistically, we demonstrate that the binding of K-RTA to the cellular specificity protein 1 (SP1) is critical for K-RTA-mediated CD274/PD-L1 promoter activation. These findings suggest that K-RTA cooperates with intracellular SP1 to activate the expression of CD274/PD-L1, which helps the virus regulate immune checkpoints to escape and survive.

Exploring the Effects of G-CSF Mobilization on the Immune Function of Mucosal-Associated Invariant T Cell Subsets By Single-Cell RNA-Seq

Background: Mucosal-associated invariant T cells (MAITs) are a group of mucosal-enriched unconventional T cells that can exert a variety of immune functions including pro-inflammatory, cytotoxic and immunomodulatory effects, whereas with the characteristics of innate immune cells. A few studies including our previous work have confirmed the relationship between MAITs and gut acute graft-versus-host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (HSCT). In addition, we further proved that specific gut microbiota can promote MAIT17 subset activation, and MAITs has a direct immunosuppressive effect on T cells in vitro, which may potentially explain our results that higher number of MAITs in granulocyte colony-stimulating factor (G-CSF) mobilized grafts is associated with lower incidence of gut aGVHD. G-CSF has been widely used to mobilize hematopoietic stem/progenitor cells before HSCT. It also plays an important immunomodulatory role in inducing immune tolerance by regulating both innate and adaptive immune cells, especially T cells. Therefore, we used single-cell RNA sequencing to further explore the different effects of G-CSF mobilization on the immune function of each subset of MAITs. Methods & Cases: We isolated MAITs from the peripheral blood (PB) of 4 healthy donors pre- and post-G-CSF mobilization by flow cytometry pre-transplantation. 8 samples were performed by single-cell RNA-seq (Figure 1A). One of these recipients who received these 4 healthy donor grafts developed gut aGVHD after transplantation. Through single-cell bioinformatics analysis, we compared the sequencing data from pre- and post-G-CSF-mobilized MAITs of doners, and from G-CSF-mobilized donors in the group of recipients with or without gut aGVHD after transplantation. Results: By performing UMAP cluster analysis on these 8 samples, according to the expression of key cell type-associated marker genes of each cluster, MAITs were annotated into 14 subsets (Figure 1A and 1B). Among these subsets, Cluster 1(CD8_effector_EOMES), 4(CD4_effector_CCR6), 5(CD4_immature_CCR7), 6(CD8_effector_RORC), 12(CD4_immunomodulatory) increased significantly after G-CSF mobilization (Figure 1C). By comparing the bioinformatical data of MAITs of pre- and post-G-CSF mobilization, the results showed that molecular markers responsible for MAIT cell hyporesponsiveness were upregulated, including potential direct or indirect modulation mediated by the IL-4/IL-13 signaling pathway (FOS, JUNB, DDIT4, NFKBIA, MT2A, VIM, etc.) (Figure 1D) or ligand receptor (G-CSF-CSF3R) interactions (Figure 1E). Besides, a specific subset of MAITs defined as Cluster 12-CD4_immunomodulatory MAITs (Figure 1A) was found that played the most important role in immune regulation after G-CSF stimulation, which specifically expressed G-CSF receptor CSF3R. Furthermore, IL-17 signaling pathway was up-regulated and GVHD pathway was down-regulated in Cluster 12 post-G-CSF mobilization (Figure 1F), which suggested the Cluster 12 is an important subset of MAITs anti-GVHD. Compared to the sequencing data of donors in the group of recipients with gut aGVHD after G-CSF mobilization (post-G-CSF-gut aGVHD), we also observed the higher expression of immunosuppressive genes (JUN, DUSP2, JUNB, VIM, etc.) of doner MAITs in group without gut aGVHD after mobilization (post-G-CSF-no gut aGVHD). In addition, in the post-G-CSF-no gut aGVHD group, the expression of SOCS3, STAT3, CCR6 (Figure 1G) and other key markers that may potentially explain the anti-GVHD effect of MAITs was upregulated, as well as the ability of tissue repair and gut-directed migration of MAITs was upregulated (Figure 1H), while its cytotoxic effector functions were not significantly affected. Conclusions: Our results indicated that G-CSF mobilization can enhance the immunosuppressive effect of MAITs. Cluster 12 (CD4_immunomodulatory) is an important immunoregulatory and anti-GVHD subset of MAITs, contributing to the differentiation of MAITs towards MAIT17. The upregulation of markers such as SOCS3, CCR6, STAT3 that involved in CSF3R-JAK-STAT pathway, as well as markers related to mucosal tissue repair may partially explain the protective effect from gut aGVHD of G-CSF mobilized MAITs. These results also enlighten us that gut aGVHD might be prevented by effectively expanding the specific immunosuppressive subset of MAIT cells in the future. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

High ORM1 Expression Marks a Subset of Genetically Adverse-Risk B-ALL Characterized By MDSC Enrichment, T-Cell Dysfunction, and Inferior Overall Survival

Alterations in the transcriptional activity of certain bone marrow microenvironment populations have been shown to contribute to the pathogenesis of B-lymphoblastic leukemia (B-ALL); however, the precise mechanisms by which neoplastic lymphoblasts shape the gene expression programs of reactive immune and stromal cell populations to support a leukemogenic niche remain incompletely characterized. ORM1 is an acute phase protein with immunomodulatory properties that is overexpressed in a subset of high-risk B-ALL. In an initial exploratory analysis of 1,104 adult and pediatric B-ALL RNA-seq transcriptomes annotated with mature survival outcomes (PMID 30643249), high ORM1 expression was significantly associated with inferior event-free and overall survival and predominantly associated with Ph+, Ph-like, and KMT2A-r B-ALL subtypes. We hypothesized that B-ALL with high ORM1 expression is associated with transcriptionally distinct bone marrow microenvironment immune cell subsets that contribute to its aggressive clinical behavior and sought to delineate these alterations through digital cytometry and analysis of single cell proteogenomic sequencing (CITE-seq) data. To delineate the tumor microenvironment (TME) features of ORM1 high B-ALL through digital cytometry, we constructed a novel bone marrow signature matrix that recapitulates the native BM cellular landscape, including hematopoietic progenitors and mesenchymal stem cells, and performed de novo transcriptional subtype discovery agnostic to clinical outcomes using the Ecotyper platform on a cohort of 577 B-ALL microarray transcriptomes from the MILE study (GSE13159). Discovery analysis identified 51 transcriptionally defined TME cell states across 17 cell types. ORM1 overexpression significantly correlated with transcriptionally-distinct neutrophil, promyelocyte, monocyte, and macrophage subsets enriched for immunosuppressive gene expression programs as well as CD8+ and γδ T-cell subsets with hallmark transcriptional features of effector dysfunction and exhaustion. To validate the imputed cell states at single-cell resolution and define their immunophenotypic features, we drew upon several B-ALL CITE-seq datasets. Recovery and assignment of discovery cohort transcriptional states to single-cell transcriptomes in KMT2A-r and Ph+ cases confirmed enrichment for multiple myeloid-derived suppressor cell (MDSC) and dysfunctional T-cell transcriptional subsets. MDSCs were predominantly monocytic but also included neutrophilic promyelocytes with surface expression of CD123 and CD155/PVR, which interacts with TIGIT to suppress immune cell activation. Indeed, enrichment for CD8+ cytotoxic lymphocytes with surface expression of PD-1 and TIGIT was also present. Neutrophilic MDSCs were present at diagnosis, in pre-relapse remission samples and at the time of relapse, suggesting that their persistence following frontline therapy may facilitate the immune evasion and expansion of treatment-resistance leukemic clones that drive eventual relapse. Taken together, high ORM1 expression marks a subset of high-risk B-ALL characterized by enrichment for transcriptionally-distinct immunosuppressive TME cell states which may be targetable with emerging therapeutic strategies aimed at restoring host anti-tumor immunity.

Interleukin-17D promotes lung cancer progression by inducing tumor-associated macrophage infiltration via the p38 MAPK signaling pathway.

Cancer immunoediting is defined as the integration of the immune system’s dual host-protective and tumor-promoting roles, including three phases: elimination, equilibrium, and escape. Immune selective pressure causes tumor cells to lose major histocompatibility complex expression or acquire immunosuppressive gene expression, which promotes tumor immune evasion and tumor progression. Interleukin-17D (IL-17D), a member of the IL-17 family of cytokines, plays an important role in the host defense against infection and inflammation. However, the role of IL-17D in the progression of lung cancer remains unclear. In this study, we found that IL-17D was highly expressed in human lung cancer, and increased IL-17D expression was associated with tumor stage and short overall survival. IL-17D overexpression significantly promoted tumor growth in subcutaneous xenograft mouse models but only slightly affected cell proliferation in vitro. Using flow cytometry, we found that IL-17D overexpression enhances the recruitment of tumor-associated macrophages to the tumor microenvironment. Based on the expression profile of IL17D–overexpressing A549 cells, we found that IL-17D increased the expression levels of macrophage polarization– and recruitment–related genes through the MAPK signaling pathway. Moreover, inhibition of the p38 pathway blocked macrophage infiltration induced by IL-17D. These results suggest that IL-17D regulates the tumor immune microenvironment via the p38 MAPK signaling pathway, highlighting IL-17D as a potential therapeutic target for lung cancer.

Inhibition of myeloid-derived suppressive cell function with all-trans retinoic acid enhanced anti-PD-L1 efficacy in cervical cancer

PD-1/PD-L1 inhibitor treatments are relatively inefficacious in advanced cervical cancer patients. The presence of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment may be one significant barrier to efficacy. It has been shown that all-trans retinoic acid (ATRA) can differentiate MDSCs into mature myeloid cells. However, whether ATRA suppression of MDSCs function could enhance PD-L1 blockade-mediated tumor immunotherapy remains unknown. Here, the frequency of tumor-infiltrating MDSCs in cervical cancer patients was measured. ATRA was used to target MDSCs both in vitro and in tumor-bearing mice. The impact of ATRA on the human cell line HeLa was also investigated. The frequency of MDSCs and T cells was determined by flow cytometry. The expression of immunosuppressive genes was measured with quantitative real time-PCR and infiltration of immune cells was assessed by immunohistochemical examination. We found that tumor-infiltrating PD-L1+ MDSCs were more prevalent in cervical cancer patients. Blockade of PD-L1 expression in MDSCs with anti-PD-L1 antibody cannot relieve the suppressive activity of MDSCs induced by HeLa cells, while ATRA efficiently abrogated the suppressive activity of MDSCs. Furthermore, ATRA had no effect on PD-L1 expression in HeLa cells in vitro. In in vivo treatment, ATRA decreased MDSCs accumulation and increased the frequency of CD8+ T cells in BALB/C mice with U14 cervical tumors. Importantly, a combination treatment of ATRA and anti-PD-L1 antibody further delayed U14 tumor growth and increased the proportion of CD62L−CD8+ T cells, CD62L−CD4+ T cells, CD107a+CD8+ T cells as well as IFN-γ and TNF-α levels in tumors. Our results provide a rationale for the use of ATRA to suppress MDSCs and enhance anti-PD-L1 cancer immunotherapy in cervical cancer.

Low expression of PGC-1β and other mitochondrial biogenesis modulators in melanoma is associated with growth arrest and the induction of an immunosuppressive gene expression program dependent on MEK and IRF-1

Mitochondria are specialized metabolic and immune organelles that have important roles in tumor progression, metastasis, and response to chemotherapy and immunotherapy. Mitochondrial biogenesis and functions are under the control of the peroxisome-proliferator activated receptor-gamma (PGC-1) transcriptional coactivators. Recent research unveiled the role of PGC-1α in bolstering mitochondrial oxidative functions and in the suppression of metastasis in melanoma, but the role of PGC-1s in tumor immunology remains elusive. Herein, we show that low PGC-1s expression in human melanoma tumors is associated with increased expression of a repertoire of immunosuppressive (CD73, PD-L2, Galectin-9) and pro-inflammatory (IL-8, TNF, IL-1β) transcripts, and that experimental depletion of PGC-1β recapitulates this signature in human melanoma cell lines. The depletion of PGC-1β reduces the expression of HSPA9, impairs mitochondrial activity, and leads to cell cycle arrest. Using pharmacological and gene silencing approaches, we further show that MEK1/2 and IRF-1 mediate the observed immune transcriptional response. Overall, this research suggests that mitochondrial biogenesis modulators can modulate tumor progression, immune evasion, and response to therapeutics through transcriptional control of immune pathways.

Abstract IA01: Unconventional ER stress response pro-tumorigenic polarization and survival in TAMs

Abstract Tumor-associated macrophages (TAMs) display pro-tumorigenic phenotypes for supporting tumor progression in response to microenvironmental cues imposed by tumor and stromal cells. However, the underlying mechanisms by which tumor cells instruct TAM behavior remain elusive. Here we uncover that tumor cell-derived glucosylceramide stimulated unconventional endoplasmic reticulum (ER) stress responses by inducing reshuffling of lipid composition and saturation on the ER membrane in macrophages, which induced IRE1-mediated spliced XBP1 production and STAT3 activation. The cooperation of spliced XBP1 and STAT3 reinforced the pro-tumorigenic phenotype and expression of immunosuppressive genes. Ablation of XBP-1 expression with genetic manipulation or ameliorating ER stress responses by facilitating LPCAT3-mediated incorporation of unsaturated lipids to the phosphatidylcholine hampered pro-tumorigenic phenotype and survival in TAMs. Together, our findings reveal the unexpected roles of tumor cell-produced lipids that simultaneously orchestrate macrophage polarization and survival in tumors via induction of ER stress responses and therapeutic targets for sustaining host anti-tumor immunity. Citation Format: Ping-Chih Ho. Unconventional ER stress response pro-tumorigenic polarization and survival in TAMs [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr IA01.

Cutibacterium acnes Induces the Expression of Immunosuppressive Genes in Macrophages and is Associated with an Increase of Regulatory T-Cells in Prostate Cancer.

ABSTRACTTumors and infectious agents both benefit from an immunosuppressive environment. Cutibacterium acnes (C. acnes) is a bacterium in the normal skin microbiota, which has the ability to survive intracellularly in macrophages and is significantly more common in prostate cancer tissue compared with normal prostate tissue. This study investigated if prostate cancer tissue culture positive for C. acnes has a higher infiltration of regulatory T-cells (Tregs) and if macrophages stimulated with C. acnes induced the expression of immunosuppressive genes that could be linked to an increase of Tregs in prostate cancer. Real-time PCR and enzyme-linked immunosorbent spot assay (ELISA) were used to examine the expression of immunosuppressive genes in human macrophages stimulated in vitro with C. acnes, and associations between the presence of C. acnes and infiltration of Tregs were investigated by statistically analyzing data generated in two previous studies. The in vitro results demonstrated that macrophages stimulated with C. acnes significantly increased their expression of PD-L1, CCL17, and CCL18 mRNA and protein (p <0.05). In the cohort, Tregs in tumor stroma and tumor epithelia were positively associated with the presence of C. acnes (P = 0.0004 and P = 0.046, respectively). Since the macrophages stimulated with C. acnes in vitro increased the expression of immunosuppressive genes, and prostate cancer patients with prostatic C. acnes infection had higher infiltration of Tregs than their noninfected counterparts, we suggest that C. acnes may contribute to an immunosuppressive tumor environment that is vital for prostate cancer progression.IMPORTANCE In an immune suppressive tumor microenvironment constituted by immunosuppressive cells and immunosuppressive mediators, tumors may improve their ability to give rise to a clinically relevant cancer. In the present study, we found that C. acnes might contribute to an immunosuppressive environment by recruiting Tregs and by increasing the expression of immunosuppressive mediators such as PD-L1, CCL17, and CCL18. We believe that our data add support to the hypothesis of a contributing role of C. acnes in prostate cancer development. If established that C. acnes stimulates prostate cancer progression it may open up avenues for targeted prostate cancer treatment.

Tumor-induced reshuffling of lipid composition on the endoplasmic reticulum membrane sustains macrophage survival and pro-tumorigenic activity.

Tumor-associated macrophages (TAMs) display pro-tumorigenic phenotypes for supporting tumor progression in response to microenvironmental cues imposed by tumor and stromal cells. However, the underlying mechanisms by which tumor cells instruct TAM behavior remain elusive. Here we uncover that tumor cell-derived glucosylceramide stimulated unconventional endoplasmic reticulum (ER) stress responses by inducing reshuffling of lipid composition and saturation on the ER membrane in macrophages, which induced IRE1-mediated spliced XBP1 production and STAT3 activation. The cooperation of spliced XBP1 and STAT3 reinforced the pro-tumorigenic phenotype and expression of immunosuppressive genes. Ablation of XBP-1 expression with genetic manipulation or ameliorating ER stress responses by facilitating LPCAT3-mediated incorporation of unsaturated lipids to the phosphatidylcholine hampered pro-tumorigenic phenotype and survival in TAMs. Together, our findings reveal the unexpected roles of tumor cell-produced lipids that simultaneously orchestrate macrophage polarization and survival in tumors via induction of ER stress responses and therapeutic targets for sustaining host anti-tumor immunity.

Tumor NLRP3-Derived IL-1β Drives the IL-6/STAT3 Axis Resulting in Sustained MDSC-Mediated Immunosuppression.

Tumors evade the immune system by inducing inflammation. In melanoma, tumor-derived IL-1β drives inflammation and the expansion of highly immunosuppressive myeloid-derived suppressor cells (MDSCs). Similar in many tumors, melanoma is also linked to the downstream IL‐6/STAT3 axis. In this study, we observed that both recombinant and tumor-derived IL-1β specifically induce pSTAT3(Y705), creating a tumor-autoinflammatory loop, which amplifies IL-6 signaling in the human melanoma cell line 1205Lu. To disrupt IL-1β/IL-6/STAT3 axis, we suppressed IL-1β-mediated inflammation by inhibiting the NOD-like receptor protein 3 (NLRP3) using OLT1177, a safe-in-humans specific NLRP3 oral inhibitor. In vivo, using B16F10 melanoma, OLT1177 effectively reduced tumor progression (p< 0.01); in primary tumors, OLT1177 decreased pSTAT3(Y705) by 82% (p<0.01) and II6 expression by 53% (p<0.05). Disruption of tumor-derived NLRP3, either pharmacologically or genetically, reduced STAT3 signaling in bone marrow cells. In PMN-MDSCs isolated from tumor-bearing mice treated with OLT1177, we observed significant reductions in immunosuppressive genes such as Pdcd1l1, Arg1, Il10 and Tgfb1. In conclusion, the data presented here show that the inhibition of NLRP3 reduces IL-1β induction of pSTAT3(Y705) preventing expression of immunosuppressive genes as well as activity in PMN-MDSCs.

Adversity in early life and pregnancy are immunologically distinct from total life adversity: macrophage-associated phenotypes in women exposed to interpersonal violence

Early childhood and pregnancy are two sensitive periods of heightened immune plasticity, when exposure to adversity may disproportionately increase health risks. However, we need deeper phenotyping to disentangle the impact of adversity during sensitive periods from that across the total lifespan. This study examined whether retrospective reports of adversity during childhood or pregnancy were associated with inflammatory imbalance, in an ethnically diverse cohort of 53 low-income women seeking family-based trauma treatment following exposure to interpersonal violence. Structured interviews assessed early life adversity (trauma exposure ≤ age 5), pregnancy adversity, and total lifetime adversity. Blood serum was assayed for pro-inflammatory (TNF-a, IL-1ß, IL-6, and CRP) and anti-inflammatory (IL-1RA, IL-4, and IL-10) cytokines. CD14+ monocytes were isolated in a subsample (n = 42) and gene expression assayed by RNA sequencing (Illumina HiSeq 4000; TruSeq cDNA library). The primary outcome was a macrophage-associated M1/M2 gene expression phenotype. To evaluate sensitivity and specificity, we contrasted M1/M2 gene expression with a second, clinically-validated macrophage-associated immunosuppressive phenotype (endotoxin tolerance) and with pro-inflammatory and anti-inflammatory cytokine levels. Adjusting for demographics, socioeconomic status, and psychopathology, higher adversity in early life (ß = .337, p = 0.029) and pregnancy (ß = .332, p = 0.032) were each associated with higher M1/M2 gene expression, whereas higher lifetime adversity (ß = −.341, p = 0.031) was associated with lower immunosuppressive gene expression. Adversity during sensitive periods was uniquely associated with M1/M2 imbalance, among low-income women with interpersonal violence exposure. Given that M1/M2 imbalance is found in sepsis, severe COVID-19 and myriad chronic diseases, these findings implicate novel immune mechanisms underlying the impact of adversity on health.

IQGAP2 acts as an independent prognostic factor and is related to immunosuppression in DLBCL

BackgroundAlmost one-third of patients with diffuse large B-cell lymphoma (DLBCL) cannot be cured with initial therapy and will eventually succumb to the disease. Further elaboration of prognostic markers of DLBCL will provide therapeutic targets. IQ motif-containing GTPase activating protein 2 (IQGAP2) acts as a tumour suppressor in hepatocellular, prostate, and gastric cancers. However, the role of IQGAP2 in DLBCL remains unclear.MethodsWe collected mRNA expression data from 614 samples and the corresponding clinical information. The survival time of patients was compared between groups according to the mRNA expression level of IQGAP2. Survival analyses were performed in different subgroups when considering the effect of age, tumour stage, serum lactate dehydrogenase (LDH) concentration, performance status, and the number of extra nodal disease sites. The biological processes associated with IQGAP2-associated mRNAs were analysed to predict the function of IQGAP2. The correlation of IQGAP2 mRNA with immunosuppressive genes and leukocyte infiltration were analysed.ResultsThe overall survival of patients with increased IQGAP2 mRNA levels was reduced even after aggressive treatment independent of age, tumour stage, serum LDH concentration, performance status, and the number of extra nodal disease sites. Furthermore, the biological processes of IQGAP2-associated mRNAs were mainly immune processes. IQGAP2 mRNA expression was correlated with the expression of immunosuppressive genes and leukocyte infiltration.ConclusionIQGAP2 mRNA is an independent prognostic factor and is related to immunosuppression in DLBCL. This discovery may provide a promising target for further development of therapy.

Impact of cell density in lymphocyte-rich areas in the tumor microenvironment on prognosis and gene expression landscape in hepatocellular carcinoma.

4107 Background: Cellular and non-cellular components in the tumor microenvironment (TME) impact prognosis and treatment in hepatocellular carcinoma (HCC). We previously reported a deep learning-based model of tissue segmentation in pathology images, showing an impact of stromal and malignant cell distribution with respect to gene expression on survival and molecular subtypes of cancer [1]. Methods: Clinical outcomes data, mRNA-seq, and histopathology images of 351 patients (pts) with HCC were obtained from TCGA. We established a combined algorithm of two deep learning models: ResNet-based model for tissue segmentation; YOLO-based model for cell detection, using published data sets [2, 3]. The tissue segmentation model defines six segments having following predominant components: malignant cells, lymphocytes, adipose, stromal, mucinous, and normal liver tissues. The cell detection model calculates density and mapping of cells in the TME. The immune landscape was analyzed via mRNA-seq of 770 genes enriched in TME. This comprehensive analysis defined parameters including the cell density per lymphocyte segmented area (CDpLA), representing the density of lymphocytes on a lymphocyte-rich area in TME. Results: Pts were clustered into two groups with high and low CDpLA (212 and 139 pts). High CDpLA was defined as lymphocyte density &gt; 0.5 (13,618 cells/mm2 lymphocyte area). Pts with high CDpLA showed significantly better median overall survival (OS) than those with low CDpLA (82.9 vs 37.8 month, p &lt; 0.005). The hazard ratio of CDpLA in OS was 0.36 (95% CI 0.18-0.72, p &lt; 0.005). Among pts with available clinical data, 29 and 21 pts were with hepatitis C (HCV) and hepatitis B (HBV). Out of 29 HCV pts, 23 and 6 pts were with high and low CDpLA; out of 21 HBV pts, 17 and 4 pts were with high and low CDpLA. Fifty three were with alcoholic abuse, and 26 and 27 pts were with high and low CDpLA. Of note, pts with high CDpLA had significantly better OS in HCV pts (61.7 vs 19.9 months, p &lt; 0.005). Genomic analysis with mRNA-seq shows that HCV pts with high CDpLA have lower expression of genes related to myeloid-derived suppressor cells (TRANK1, MEGF9, HS3ST2, GPNMB) and higher in genes related to immune activation (PLD4, IL3RA, TNFRSF4). Conclusions: A deep learning-assisted model of TME segmentation and cell detection showed an impact on survival from CDpLA, rather than the total number of lymphocytes in the TME. HCV pts are more likely to have higher CDpLA, and CDpLA was a strong prognostic indicator in HCV pts. Pts with high CDpLA are those with elevated expression of genes related to immune activation and decreased expression of immunosuppressive genes. Retrospective and prospective analysis of clinical response to immunotherapy and tyrosine kinase inhibitors is underway. [1] Kim et al. Cancer Res 2020 (80) (16 Supp) 2631 [2] Kather et al. PLoS Med 2019 16(1): e1002730 [3] Gamper et al. arXiv 2020:10778