Characteristics of the Tumor Microenvironment That Influence Immune Cell Functions: Hypoxia, Oxidative Stress, Metabolic Alterations

Immunotherapy (IMT) is now a core component of cancer treatment, however, many patients do not respond to these novel therapies. Investigating the resistance mechanisms behind this differential response is now a critical area of research. Immune-based therapies, particularly immune checkpoint inhibitors (ICI), rely on a robust infiltration of T-cells into the tumor microenvironment (TME) for an effective response. While early efforts relied on quantifying tumor infiltrating lymphocytes (TIL) in the TME, characterizing the functional quality and degree of TIL exhaustion correlates more strongly with ICI response. Even with sufficient TME infiltration, immune cells face a harsh metabolic environment that can significantly impair effector function. These tumor-mediated metabolic perturbations include hypoxia, oxidative stress, and metabolites of cellular energetics. Primarily through HIF-1-dependent processes, hypoxia invokes an immunosuppressive phenotype via altered molecular markers, immune cell trafficking, and angiogenesis. Additionally, oxidative stress can promote lipid peroxidation, ER stress, and Treg dysfunction, all associated with immune dysregulation. Finally, the metabolic byproducts of lipids, amino acids, glucose, and cellular energetics are associated with immunosuppression and ICI resistance. This review will explore these biochemical pathways linked to immune cell dysfunction in the TME and highlight potential adjunctive therapies to be used alongside current IMT.

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Enhanced B7-H4 Expression in Gliomas With Low PD-L1 Expression Identifies Cold Tumors

Neurosurgery ◽

10.1093/neuros/nyz310_637 ◽

2019 ◽

Vol 66 (Supplement_1) ◽

Author(s):

Di Chen ◽

Gaopeng Li ◽

Chunxia Ji ◽

Qiqi Lu ◽

Ying Qi ◽

...

Keyword(s):

T Cell ◽

Mrna Expression ◽

Immune Cell ◽

Expression Profiles ◽

Tumor Infiltrating Lymphocytes ◽

Expression Level ◽

Cell Trafficking ◽

Mrna Expression Level ◽

Cell Functions ◽

Genes Expression

Abstract INTRODUCTION The expression profiles of different immune checkpoint molecules are promising for triaging personalized targeted immunotherapy. Our study was performed to determine co-expression levels of 2 major B7 immune molecules, PD-L1 and B7-H4, in gliomas where both have demonstrated to inhibit antitumor host immunity. METHODS We assessed tumor issues from primary gliomas stage II to IV (n = 505) by immunohistochemistry (IHC) for protein levels of both PD-L1 and B7-H4. Gene co-expression analysis assessing clusters based on extent of PD-L1/B7-H4 classifier genes expression were investigated in 2 transcriptome datasets (TCGA and CGGA) to validate IHC expression profiles and explore properties of the glioma immune microenvironment among specific co-expression PD-L1/B7-H4 cluster groups. RESULTS PD-L1 was detected in 61% of patients whereby 23% expressed high levels. B7-H4 was expressed in 54% whereby 20% were identified as high expression. Co-expression of PD-L1 and B7-H4 in high levels was limited to 2% cases. Comparable results were seen in RNA-sequencing datasets when PD-L1 mRNA expression level corelated negatively with B7-H4. Gene co-expression modules clustered in each grade gliomas without double-high modules (gliomas cluster with high mRNA expression of both PD-L1 and B7-H4 classifier genes) also verified restricted coexpression pattern. B7-H4 mRNA expression level had negative correlation with extent of immune cell infiltration, including tumor-infiltrating lymphocytes (TILs), and high-B7-H4 module gliomas (high B7-H4 but low PD-L1 classifier genes expression) was related to a cold tumor with less TILs. CONCLUSION The majority of gliomas express PD-L1 or B7-H4, however, co-expression of both at high levels is minimal. The high-B7-H4 module was significantly lacking in TILs, suggesting that B7-H4 might inhibit T cell trafficking into the central nervous system (CNS). This study demonstrates that PD-L1 expression alone is not fully informative in gliomas for immune targeted or active-specific immunotherapy, and PD-L1 and B7-H4 probably inhibit different aspects of the T cell functions.

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Emerging Trends for Radio-Immunotherapy in Rectal Cancer

Cancers ◽

10.3390/cancers13061374 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1374

Author(s):

Claudia Corrò ◽

Valérie Dutoit ◽

Thibaud Koessler

Keyword(s):

Rectal Cancer ◽

Tumor Microenvironment ◽

Immune Checkpoint ◽

Checkpoint Inhibitors ◽

Predictive Biomarkers ◽

Tumor Infiltrating Lymphocytes ◽

T Cell Infiltration ◽

Emerging Trends ◽

Tumor Mutational Burden ◽

Microsatellite Stability

Rectal cancer is a heterogeneous disease at the genetic and molecular levels, both aspects having major repercussions on the tumor immune contexture. Whilst microsatellite status and tumor mutational load have been associated with response to immunotherapy, presence of tumor-infiltrating lymphocytes is one of the most powerful prognostic and predictive biomarkers. Yet, the majority of rectal cancers are characterized by microsatellite stability, low tumor mutational burden and poor T cell infiltration. Consequently, these tumors do not respond to immunotherapy and treatment largely relies on radiotherapy alone or in combination with chemotherapy followed by radical surgery. Importantly, pre-clinical and clinical studies suggest that radiotherapy can induce a complete reprograming of the tumor microenvironment, potentially sensitizing it for immune checkpoint inhibition. Nonetheless, growing evidence suggest that this synergistic effect strongly depends on radiotherapy dosing, fractionation and timing. Despite ongoing work, information about the radiotherapy regimen required to yield optimal clinical outcome when combined to checkpoint blockade remains largely unavailable. In this review, we describe the molecular and immune heterogeneity of rectal cancer and outline its prognostic value. In addition, we discuss the effect of radiotherapy on the tumor microenvironment, focusing on the mechanisms and benefits of its combination with immune checkpoint inhibitors.

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Single-cell RNA Sequencing Reveals Immunosuppressive Myeloid Cell Diversity and Restricted Cytotoxic Effector Cell Trafficking and Activation During Malignant Progression in Glioma

10.1101/2021.09.24.461735 ◽

2021 ◽

Author(s):

Sakthi Rajendran ◽

Clayton Peterson ◽

Alessandro Canella ◽

Yang Hu ◽

Amy Gross ◽

...

Keyword(s):

T Cells ◽

Tumor Microenvironment ◽

Single Cell ◽

Immune Cell ◽

Myeloid Cell ◽

Malignant Progression ◽

Low Grade ◽

Cell Trafficking ◽

High Grade ◽

Single Cell Rna Sequencing

Low grade gliomas (LGG) account for about two-thirds of all glioma diagnoses in adolescents and young adults (AYA) and malignant progression of these patients leads to dismal outcomes. Recent studies have shown the importance of the dynamic tumor microenvironment in high-grade gliomas (HGG), yet its role is still poorly understood in low-grade glioma malignant progression. Here, we investigated the heterogeneity of the immune microenvironment using a platelet-derived growth factor (PDGF)-driven RCAS (replication-competent ASLV long terminal repeat with a splice acceptor) glioma model that recapitulates the malignant progression of low to high-grade glioma in humans and also provides a model system to characterize immune cell trafficking and evolution. To illuminate changes in the immune cell landscape during tumor progression, we performed single-cell RNA sequencing on immune cells isolated from animals bearing no tumor (NT), LGG and HGG, with a particular focus on the myeloid cell compartment, which is known to mediate glioma immunosuppression. LGGs demonstrated significantly increased infiltrating T cells, CD4 T cells, CD8 T cells, B cells, and natural killer cells in the tumor microenvironment, whereas HGGs significantly abrogated this infiltration. Our study identified two distinct macrophage clusters in the tumor microenvironment; one cluster appeared to be bone marrow-derived while another was defined by overexpression of Trem2, a marker of tumor associated macrophages. Our data demonstrates that these two distinct macrophage clusters show an immune-activated phenotype (Stat1, Tnf, Cxcl9 and Cxcl10) in LGG which evolves to an immunosuppressive state (Lgals3, Apoc1 and Id2) in HGG that restricts T cell recruitment and activation. We identified CD74 and macrophage migration inhibition factor (MIF) as potential targets for these distinct macrophage populations. Interestingly, these results were mirrored by our analysis of the TCGA dataset, which demonstrated a statistically significant association between CD74 overexpression and decreased overall survival in AYA patients with grade II gliomas. Targeting immunosuppressive myeloid cells and intra-tumoral macrophages within this therapeutic window may ameliorate mechanisms associated with immunosuppression before and during malignant progression.

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The Immune Endocannabinoid System of the Tumor Microenvironment

International Journal of Molecular Sciences ◽

10.3390/ijms21238929 ◽

2020 ◽

Vol 21 (23) ◽

pp. 8929

Author(s):

Melanie Kienzl ◽

Julia Kargl ◽

Rudolf Schicho

Keyword(s):

Tumor Microenvironment ◽

Tumor Progression ◽

Immune Cells ◽

Cannabinoid Receptors ◽

Immune Cell ◽

Tumor Development ◽

Endocannabinoid System ◽

Cell Functions ◽

In Vitro Effects

Leukocytes are part of the tumor microenvironment (TME) and are critical determinants of tumor progression. Because of the immunoregulatory properties of cannabinoids, the endocannabinoid system (ECS) may have an important role in shaping the TME. Members of the ECS, an entity that consists of cannabinoid receptors, endocannabinoids and their synthesizing/degrading enzymes, have been associated with both tumor growth and rejection. Immune cells express cannabinoid receptors and produce endocannabinoids, thereby forming an “immune endocannabinoid system”. Although in vitro effects of exogenous cannabinoids on immune cells are well described, the role of the ECS in the TME, and hence in tumor development and immunotherapy, is still elusive. This review/opinion discusses the possibility that the “immune endocannabinoid system” can fundamentally influence tumor progression. The widespread influence of cannabinoids on immune cell functions makes the members of the ECS an interesting target that could support immunotherapy.

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Highly Multiplexed Digital Spatial Profiling of the Tumor Microenvironment of Head and Neck Squamous Cell Carcinoma Patients

Frontiers in Oncology ◽

10.3389/fonc.2020.607349 ◽

2021 ◽

Vol 10 ◽

Author(s):

Arutha Kulasinghe ◽

Touraj Taheri ◽

Ken O’Byrne ◽

Brett G. M. Hughes ◽

Liz Kenny ◽

...

Keyword(s):

Squamous Cell Carcinoma ◽

Tumor Microenvironment ◽

Cell Carcinoma ◽

Head And Neck ◽

Squamous Cell ◽

Immune Cell ◽

Checkpoint Inhibitors ◽

Neck Squamous Cell Carcinoma ◽

Protein Markers ◽

Spatial Profiling

BackgroundImmune checkpoint inhibitors (ICI) have shown durable and long-term benefits in a subset of head and neck squamous cell carcinoma (HNSCC) patients. To identify patient-responders from non-responders, biomarkers are needed which are predictive of outcome to ICI therapy. Cues in the tumor microenvironment (TME) have been informative in understanding the tumor-immune contexture.MethodsIn this preliminary study, the NanoString GeoMx™ Digital Spatial Profiling (DSP) technology was used to determine the immune marker and compartment specific measurements in a cohort of HNSCC tumors from patients receiving ICI therapy.ResultsOur data revealed that markers involved with immune cell infiltration (CD8 T-cells) were not predictive of outcome to ICI therapy. Rather, a number of immune cell types and protein markers (CD4, CD68, CD45, CD44, CD66b) were found to correlate with progressive disease. Cross platform comparison with the Opal Vectra (Perkin Elmer) for a number of markers across similar regions of interest demonstrated concordance for pan-cytokeratin, CD8, and PD-L1.ConclusionThis study, to our knowledge, represents the first digital spatial analysis of HNSCC tumors. A larger cohort of HNSCC will be required to orthogonally validate the findings.

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Immunomodulating Therapies in Breast Cancer—From Prognosis to Clinical Practice

Cancers ◽

10.3390/cancers13194883 ◽

2021 ◽

Vol 13 (19) ◽

pp. 4883

Author(s):

Marcus Schmidt ◽

Anne-Sophie Heimes

Keyword(s):

Breast Cancer ◽

Immune Responses ◽

Triple Negative Breast Cancer ◽

Immune Checkpoint ◽

Triple Negative ◽

Immune Cell ◽

Checkpoint Inhibitors ◽

Tumor Infiltrating Lymphocytes ◽

Response To Chemotherapy ◽

Infiltrating Lymphocytes

The role of the immune system in breast cancer has been debated for decades. The advent of technologies such as next generation sequencing (NGS) has elucidated the crucial interplay between somatic mutations in tumors leading to neoantigens and immune responses with increased tumor-infiltrating lymphocytes and improved prognosis of breast cancer patients. In particular, triple-negative breast cancer (TNBC) has a higher mutational burden compared to other breast cancer subtypes. In addition, higher levels of tumor-associated antigens suggest that immunotherapies are a promising treatment option, specifically for TNBC. Indeed, higher concentrations of tumor-infiltrating lymphocytes are associated with better prognosis and response to chemotherapy in TNBC. An important target within the cancer immune cell cycle is the “immune checkpoint”. Immune checkpoint inhibitors (ICPis) block the interaction of certain cell surface proteins that act as “brakes” on immune responses. Recent studies have shown that ICPis improve survival in both early and advanced TNBC. However, this comes at the price of increased toxicity, particularly immune-mediated toxicity. As an alternative approach, individualized mRNA vaccination strategies against tumor-associated neoantigens represent another promising approach leading to neoantigen-specific immune responses. These novel strategies should help to improve treatment outcomes, especially for patients with triple negative breast cancer.

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Dietary Intervention Impacts Immune Cell Functions and Dynamics by Inducing Metabolic Rewiring

Frontiers in Immunology ◽

10.3389/fimmu.2020.623989 ◽

2021 ◽

Vol 11 ◽

Author(s):

Takuma Okawa ◽

Motoyoshi Nagai ◽

Koji Hase

Keyword(s):

T Cell ◽

Cell Fate ◽

Molecular Mechanisms ◽

Dietary Intervention ◽

Immune Cell ◽

Aerobic Glycolysis ◽

Acid Oxidation ◽

Intermittent Fasting ◽

Cell Trafficking ◽

Cell Functions

Accumulating evidence has shown that nutrient metabolism is closely associated with the differentiation and functions of various immune cells. Cellular metabolism, including aerobic glycolysis, fatty acid oxidation, and oxidative phosphorylation, plays a key role in germinal center (GC) reaction, B-cell trafficking, and T-cell-fate decision. Furthermore, a quiescent metabolic status consolidates T-cell-dependent immunological memory. Therefore, dietary interventions such as calorie restriction, time-restricted feeding, and fasting potentially manipulate immune cell functions. For instance, intermittent fasting prevents the development of experimental autoimmune encephalomyelitis. Meanwhile, the fasting response diminishes the lymphocyte pool in gut-associated lymphoid tissue to minimize energy expenditure, leading to the attenuation of Immunoglobulin A (IgA) response. The nutritional status also influences the dynamics of several immune cell subsets. Here, we describe the current understanding of the significance of immunometabolism in the differentiation and functionality of lymphocytes and macrophages. The underlying molecular mechanisms also are discussed. These experimental observations could offer new therapeutic strategies for immunological disorders like autoimmunity.

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Differences in Immunological Landscape between EGFR-Mutated and Wild-Type Lung Adenocarcinoma

Disease Markers ◽

10.1155/2021/3776854 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Jia-Wei Luo ◽

Yan-Hua Guo ◽

Feng-Ying Wu ◽

Xue-Fei Li ◽

Xue-Cheng Sun ◽

...

Keyword(s):

Tumor Microenvironment ◽

Lung Adenocarcinoma ◽

Immune Checkpoint ◽

Immune Checkpoint Inhibitors ◽

Immune Cell ◽

Checkpoint Inhibitors ◽

Disease Free Survival ◽

Egfr Mutations ◽

Wild Type ◽

Egfr Mutant

Recent clinical trials of lung adenocarcinoma with immune checkpoint inhibitors revealed that lung adenocarcinoma patients with EGFR mutations have a poor response to immunotherapy. However, the mechanisms have not been addressed. We performed immunohistochemistry analyses of resected lung adenocarcinoma tissues with and without EGFR mutations to investigate and compare the characteristics of the tumor microenvironment (TME). We retrospectively enrolled a total of 323 lung adenocarcinoma patients (164 had EGFR mutations), and their corresponding tissue samples were analyzed by the EGFR mutation test and immunohistochemistry. We selected the markers of the immune checkpoint molecule (PD1, PD-L1, and LAG-3) and immune cell (CD3, CD4, CD8, and Foxp3) as markers of the tumor microenvironment. Our results revealed that patients had a distinct tumor microenvironment between EGFR-mutant and wild-type lung adenocarcinomas; the expression of CD3, CD4, PD-L1, and Foxp3 in EGFR-mutant tumors was significantly higher than that in wild-type tumors, while the expression of LAG3 and PD-1 showed a positive correlation with EGFR-wild-type tumors. In survival analysis, EGFR-wild-type patients had longer disease-free survival (DFS) than EGFR-mutant patients ( P = 0.0065 ). Our research demonstrates significant differences in tumor microenvironment composition between EGFR-mutant and wild-type patients. Our findings provide novel evidence that contributes to understanding the mechanism underlying the poor efficacy of immune checkpoint inhibitors.

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Chemokine-Directed Tumor Microenvironment Modulation in Cancer Immunotherapy

International Journal of Molecular Sciences ◽

10.3390/ijms22189804 ◽

2021 ◽

Vol 22 (18) ◽

pp. 9804

Author(s):

Pedro Bule ◽

Sandra I. Aguiar ◽

Frederico Aires-Da-Silva ◽

Joana N. R. Dias

Keyword(s):

Tumor Microenvironment ◽

Immune Cells ◽

Immune Cell ◽

Vascular Endothelial Cells ◽

Tumor Biology ◽

Large Family ◽

Response To Therapy ◽

Cell Trafficking ◽

Immunotherapy Target ◽

Patient Prognosis

Chemokines are a large family of small chemotactic cytokines that coordinates immune cell trafficking. In cancer, they have a pivotal role in the migration pattern of immune cells into the tumor, thereby shaping the tumor microenvironment immune profile, often towards a pro-tumorigenic state. Furthermore, chemokines can directly target non-immune cells in the tumor microenvironment, including cancer, stromal and vascular endothelial cells. As such, chemokines participate in several cancer development processes such as angiogenesis, metastasis, cancer cell proliferation, stemness and invasiveness, and are therefore key determinants of disease progression, with a strong influence in patient prognosis and response to therapy. Due to their multifaceted role in the tumor immune response and tumor biology, the chemokine network has emerged as a potential immunotherapy target. Under the present review, we provide a general overview of chemokine effects on several tumoral processes, as well as a description of the currently available chemokine-directed therapies, highlighting their potential both as monotherapy or in combination with standard chemotherapy or other immunotherapies. Finally, we discuss the most critical challenges and prospects of developing targeted chemokines as therapeutic options.

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Lifting the innate immune barriers to antitumor immunity

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-000695 ◽

2020 ◽

Vol 8 (1) ◽

pp. e000695 ◽

Cited By ~ 5

Author(s):

Carla V Rothlin ◽

Sourav Ghosh

Keyword(s):

Immune Response ◽

Innate Immunity ◽

Immune System ◽

T Cell ◽

Time Course ◽

Immune Cell ◽

Checkpoint Inhibitors ◽

Cell Activity ◽

Innate Immune ◽

Cell Functions

The immune system evolved for adequate surveillance and killing of pathogens while minimizing host damage, such as due to chronic or exaggerated inflammation and autoimmunity. This is achieved by negative regulators and checkpoints that limit the magnitude and time course of the immune response. Tumor cells often escape immune surveillance and killing. Therefore, disrupting the brakes built into the immune system should effectively boost the anticancer immune response. The success of anti-CTLA4, anti-PD-1 and anti-PD-L1 have firmly established this proof of concept. Since the response rate of anti-CTLA4, anti-PD-1 and anti-PD-L1 is still limited, there is an intense effort for the identification of new targets and development of approaches that can expand the benefits of immunotherapy to a larger patient pool. Additional T cell checkpoints are obvious targets; however, here we focus on the unusual suspects—cells that function to initiate and guide T cell activity. Innate immunity is both an obligate prerequisite for the initiation of adaptive immune responses and a requirement for the recruitment of activated T cells to the site of action. We discuss some of the molecules present in innate immune cells, including natural killer cells, dendritic cells, macrophages, myeloid-derived suppressor cells, endothelial cells and stromal cells, that can activate or enhance innate immune cell functions, and more importantly, the inhibitors or checkpoints present in these cells that restrain their functions. Boosting innate immunity, either by enhancing activator functions or, preferably, by blocking the inhibitors, may represent a new anticancer treatment modality or at least function as adjuvants to T cell checkpoint inhibitors.

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