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Abstract Background Dysfunction of CD8+ T cells in the tumor microenvironment (TME) contributes to tumor immune escape and immunotherapy tolerance. The effects of hormones such as leptin, steroid hormones, and glucocorticoids on T cell function have been reported previously. However, the mechanism underlying thyroid‐stimulating hormone (TSH)/thyroid‐stimulating hormone receptor (TSHR) signaling in CD8+ T cell exhaustion and tumor immune evasion remain poorly understood. This study was aimed at investigating the effects of TSH/TSHR signaling on the function of CD8+ T cells and immune evasion in colorectal cancer (CRC). Methods TSHR expression levels in CD8+ T cells were assessed with immunofluorescence and flow cytometry. Functional investigations involved manipulation of TSHR expression in cellular and mouse models to study its role in CD8+ T cells. Mechanistic insights were mainly gained through RNA‐sequencing, Western blotting, chromatin immunoprecipitation and luciferase activity assay. Immunofluorescence, flow cytometry and Western blotting were used to investigate the source of TSH and TSHR in CRC tissues. Results TSHR was highly expressed in cancer cells and CD8+ T cells in CRC tissues. TSH/TSHR signaling was identified as the intrinsic pathway promoting CD8+ T cell exhaustion. Conditional deletion of TSHR in CD8+ tumor‐infiltrating lymphocytes (TILs) improved effector differentiation and suppressed the expression of immune checkpoint receptors such as programmed cell death 1 (PD‐1) and hepatitis A virus cellular receptor 2 (HAVCR2 or TIM3) through the protein kinase A (PKA)/cAMP‐response element binding protein (CREB) signaling pathway. CRC cells secreted TSHR via exosomes to increase the TSHR level in CD8+ T cells, resulting in immunosuppression in the TME. Myeloid‐derived suppressor cells (MDSCs) was the main source of TSH within the TME. Low expression of TSHR in CRC was a predictor of immunotherapy response. Conclusions The present findings highlighted the role of endogenous TSH/TSHR signaling in CD8+ T cell exhaustion and immune evasion in CRC. TSHR may be suitable as a predictive and therapeutic biomarker in CRC immunotherapy.

CD8+ T cells are the primary mediators of antigen-specific immune responses, with their functional states finely regulated by molecular mechanisms, playing a crucial role in tumor immunity. In recent years, CD8+ T-cell-based cellular therapies (e.g., TCR-T and CAR-T cell therapy) and immune checkpoint therapies that block PD-1 signaling pathway have achieved unprecedented success in clinical cancer treatments. However, the therapeutic effects of these immunotherapies are still limited, mainly due to immune resistance, with a significant factor being the functional exhaustion of tumor antigen-specific CD8+ T cells. Consequently, a major focus and challenge in immunotherapy research is to understand the regulatory mechanisms behind this functional exhaustion and to develop intervention strategies and targets to enhance CD8+ T cell effector functions. This article reviews the research progress in antitumor immune responses of CD8+ T cells from three perspectives: The heterogeneity of exhausted CD8+ T cells, their response to PD-1 immune checkpoint blockade (ICB), and their epigenetic characteristics.

CD8+ T cells are crucial cytotoxic components of the tumor immune system. In chronic inflammation, they become low-responsive, a state known as T cell exhaustion (TEX). The aim of immune checkpoint blockade is to counteract TEX, yet its dynamics in breast cancer remain poorly understood. This review defines CD8+ TEX and outlines its features and underlying mechanisms. It also discusses the primary mechanisms of CD8+ TEX in breast cancer, covering inhibitory receptors, immunosuppressive cells, cytokines, transcriptomic and epigenetic alterations, metabolic reprogramming, and exosome pathways, offering insights into potential immunotherapy strategies for breast cancer.

Coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) is a risk factor for immunological non-response to antiretroviral therapy. In cases of immunological non-response, HIV viral load suppression occurs without an increase in CD4⁺ T-cell counts, heightening the risk of morbidity and mortality in infected individuals. T-cell exhaustion may hinder their regeneration in immunological non-responders. This study aimed to identify markers of CD4⁺ and CD8⁺ T-cell exhaustion in HIV/HCV coinfected immunological non-responders. The study examined three clinical groups: 1) HIV/HCV coinfected immunological non-responders (CD4⁺ T-cells 350/µl blood; n = 9), 2) HIV/HCV coinfected individuals with a standard response to therapy (CD4⁺ T-cells 500/µl blood; n = 9), and 3) relatively healthy volunteers without HIV and HCV infections (n = 9). Ex vivo, the number of CD4⁺ and CD8⁺ T-cells expressing the inhibitory receptor PD-1 was determined using multi-color flow cytometry. In the 7-day in vitro experiment, cell cultures were stimulated with phytohemagglutinin. The number of dying proliferated CD4⁺ and CD8⁺ T-cells (CFSElowZombieUV+) was determined using multi-color flow cytometry. The amount of interleukin-2 in the culture supernatants was measured using an enzyme-linked immunosorbent assay. It was found that in HIV/HCV coinfected immunological non-responders, there was a higher number of CD4⁺ and CD8⁺ T-cells expressing PD-1, a phenotypic marker of exhaustion, compared to the other two groups. Furthermore, the frequency of dying dividing T-cells was higher in immunological non-responders, with an increase in CD4⁺ T-cells but not CD8⁺ T-lymphocytes. Similarly, a decrease in interleukin-2 production was found in stimulated T-cells of HIV/HCV coinfected immunological non-responders in the CD4⁺ T-cell pool, but not in CD8⁺ T-lymphocytes. Thus, in HIV/HCV coinfected immunological non-responders, CD4⁺ T-cells appear exhausted both phenotypically and functionally. While CD8⁺ T-cells express inhibitory receptors, they do not show functional impairments. It appears that the specialized therapy for HIV/HCV coinfected immunological non-responders should aim to improve CD4⁺ T-cell function.

A steady dysfunctional state caused by chronic antigen stimulation in the tumor microenvironment (TME) is known as CD8+ T cell exhaustion. Exhausted-like CD8+ T cells (CD8+ Tex) displayed decreased effector and proliferative capabilities, elevated co-inhibitory receptor generation, decreased cytotoxicity, and changes in metabolism and transcription. TME induces T cell exhaustion through long-term antigen stimulation, upregulation of immune checkpoints, recruitment of immunosuppressive cells, and secretion of immunosuppressive cytokines. CD8+ Tex may be both the reflection of cancer progression and the reason for poor cancer control. The successful outcome of the current cancer immunotherapies, which include immune checkpoint blockade and adoptive cell treatment, depends on CD8+ Tex. In this review, we are interested in the intercellular signaling network of immune cells interacting with CD8+ Tex. These findings provide a unique and detailed perspective, which is helpful in changing this completely unpopular state of hypofunction and intensifying the effect of immunotherapy.

Abstract Background B7‐H3 protein is an important regulator of the adaptive immune response in human tumorigenesis. 4‐1BB is a co‐stimulatory receptor expressed on activated CD8+ T cells, and regulates T cell immunity. Here, we investigated the role of B7‐H3 in the growth and invasion of nasopharyngeal carcinoma (NPC) and the effect of its interaction with 4‐1BB on tumor immunity. Methods Short hairpin (sh) RNA was designed to knock down B7‐H3 expression in NPC cells. NPC cells with stable knockdown of B7‐H3 were established and injected into nude mice. The effects of B7‐H3 on cell proliferation, apoptosis, and epithelial‐to‐mesenchymal transition (EMT) were detected by the CCK8 assay, flow cytometry, TUNEL assay, and western blot analysis. The migration and invasion abilities were determined using the Transwell assay and scratch assay. Co‐immunoprecipitation (Co‐IP) assays were performed to study the interaction between B7‐H3 and 4‐1BB. Anti‐4‐1BB antibody was used in a co‐culture system and xenograft mice to study the effect of 4‐1BB on NPC development. Results NPC cells transfected with sh‐B7‐H3 showed a higher rate of apoptosis, slower growth rate, impaired migration, and less EMT in vitro. Xenograft mice with stable knockout of B7‐H3 had lower tumor burdens, and the stripped tumors had lower rates of cell proliferation, higher rates of apoptosis, and less EMT in vivo. Additionally, decreased B7‐H3 expression was positively correlated with interferon‐γ, tumor necrosis factor‐α, and 4‐1BB+CD8+ tumor‐infiltrating lymphocytes. Co‐IP studies showed that B7‐H3 interacts with 4‐1BB. Also, the inhibitory effects of sh‐B7‐H3 on NPC tumor growth, invasion, and tumor immunity could be alleviated by the anti‐4‐1BB antibody both in vivo and in vitro. Conclusion Our findings suggest that B7‐H3 may accelerate tumor growth, tumor cell invasion, and EMT, and interact with 4‐1BB to produce CD8+ T cell exhaustion that inhibits tumor immunity. B7‐H3 might serve as a novel target for treating NPC.

Exhausted T cell (Tex) is a specific state of T cell dysfunction, in which these T cells gradually lose their effector function and change their phenotype during chronic antigen stimulation. The enrichment of exhausted CD8 + T cell (CD8 + Tex) in the tumor microenvironment is one of the important reasons leading to the poor efficacy of immunotherapy. Recent studies have reported many reasons leading to the CD8 + T cell exhaustion. In addition to cancer cells, myeloid cells can also contribute to T cell exhaustion via many ways. In this review, we discuss the history of the concept of exhaustion, CD8 + T cell dysfunction states, the heterogeneity, origin, and characteristics of CD8 + Tex. We then focus on the effects of myeloid cells on CD8 + Tex, including tumor-associated macrophages (TAMs), dendritic cells (DCs) and neutrophils. Finally, we systematically summarize current strategies and recent advancements in therapies reversing and CD8 + T cell exhaustion., Competing Interests: All authors listed have made a substantial, direct and intellectual contribution to the article. Mi Deng, Yijie Zhai and Xiaoting Liang conceived the structure and idea of the article. Yijie Zhai was responsible for writing the basic situation of CD8+ Tex and the effect of myeloid cells on CD8+ Tex. Xiaoting Liang was responsible for systematically summarizing current strategies and recent advancements in therapies reversing CD8+ T cell exhaustion. All authors conceived, discussed content, and contributed to the manuscript and figures. All authors contributed to the article and approved the submitted version. Conflicts of Interest: The authors have no conflicts of interest to declare.Conflicts of Interest: The authors have no conflicts of interest to declare., (Copyright ©2024 Chinese Journal of Cancer Research. All rights reserved.)

Aim: Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related mortality and is characterized by T-cell exhaustion, particularly in effector CD8+ T-cells. This exhaustion, driven by persistent immunosuppressive signals in the tumor microenvironment, impairs immune function and hinders effective immunotherapy. This study aimed to identify key exhaustion-related marker genes in CD8+ T-cells linked to PDAC and assess the potential of repurposing anti-inflammatory drugs to counteract T-cell exhaustion and enhance immune responses against PDAC. Methods: We employed a multi-omics approach, integrating single-cell RNA sequencing data with whole genome sequencing to identify dysregulated exhaustion-related immune markers in CD8+ T-cells in PDAC. We examined gene expression profiles and conducted functional enrichment analysis to evaluate their roles in immune exhaustion. We analyzed mutations in the shortlisted biomarkers from The Cancer Genome Atlas (TCGA) and performed in silico mutational analysis using Maestro to evaluate the impact of an IL7R mutation (K110N) on protein function. Virtual screening using a deep learning framework, GNINA, explored the inhibitory features of the anti-inflammatory drugs oxaprozin and celecoxib on IL7R. Results: Key dysregulated exhaustion-related immune markers were identified including PRF1, GZMA, CD8A, CD3D, NKG7, IL7R, and IL2RG. Pathway enrichment analysis indicated significant involvement in T-cell receptor signaling, Th1 and Th2 differentiation, and Th17 differentiation pathways, correlating with reported poor survival outcomes in PDAC patients. Mutational analysis of IL7R revealed a likely pathogenic mutation (K110N) located in the IL-7Ralpha fibronectin type III domain. Drug repurposing of oxaprozin and celecoxib showed favorable binding interactions with both wild and mutant IL7R proteins. Conclusions: The K110N mutation, despite not causing significant structural changes, may impact T-cell and B-cell homeostasis and development. Our findings suggest that oxaprozin and celecoxib could effectively inhibit T-cell exhaustion through favorable interactions with IL7R. Further clinical studies are necessary to validate the therapeutic potential of these anti-inflammatory drugs in enhancing immune responses in pancreatic cancer.

Background: Hepatocellular carcinoma (HCC) is a prevalent type of cancer with high incidence and mortality rates. It is the third most common cause of cancer-related deaths. CD8 + T cell exhaustion (TEX) is a progressive decline in T cell function due to sustained T cell receptor stimulation from continuous antigen exposure. Studies have shown that CD8 + TEX plays an important role in the anti-tumor immune process and is significantly correlated with patient prognosis. The aim of the research is to establish a reliable CD8 + TEX-based signature using single-cell RNA sequencing (scRNA-seq) and high-throughput RNA sequencing (RNA-seq), providing a new approach to evaluate HCC patient prognosis and immune microenvironment., Methods: The RNA-seq data of HCC patients were download from three different databases: The Cancer Genome Atlas (TCGA), the Gene Expression Omnibus (GEO), and the International Cancer Genome Consortium (ICGC). HCC's 10× scRNA data were acquired from GSE149614. Based on single-cell sequencing data, CD8 + TEX-related genes were identified using uniform manifold approximation and projection (UMAP) algorithm, singleR, and marker gene methods. Afterwards, we proceeded to construct CD8 + TEX signature using differential gene analysis, univariate Cox regression analysis, least absolute shrinkage and selection operator (LASSO) regression, and multivariate Cox regression analysis. We also validated the CD8 + TEX signature in GEO and ICGC external cohorts and investigated clinical characteristics, chemotherapy sensitivity, mutation landscape, functional analysis, and immune cell infiltration in different risk groups., Results: The CD8 + TEX signature, consisting of 13 genes ( HSPD1 , UBB , DNAJB4, CALM1 , LGALS3 , BATF , COMMD3 , IL7R , FDPS , DRAP1 , RPS27L , PAPOLA ), was found to have a strong predictive effect on the prognosis of HCC. The Kaplan-Meier (KM) analysis showed that the overall survival (OS) rate of patients in the low-risk group was higher than that of patients in the high-risk group across different datasets and specific populations. The research findings suggested that the risk score was an independent predictor of HCC prognosis. The model based on clinical features and risk score has a strong predictive effect. We observed significant differences among various risk groups in terms of clinical characteristics, functional analysis, mutation landscape, chemotherapy sensitivity, and immune cell infiltration.GPR171 ), was found to have a strong predictive effect on the prognosis of HCC. The Kaplan-Meier (KM) analysis showed that the overall survival (OS) rate of patients in the low-risk group was higher than that of patients in the high-risk group across different datasets and specific populations. The research findings suggested that the risk score was an independent predictor of HCC prognosis. The model based on clinical features and risk score has a strong predictive effect. We observed significant differences among various risk groups in terms of clinical characteristics, functional analysis, mutation landscape, chemotherapy sensitivity, and immune cell infiltration., Conclusions: We constructed a CD8 + TEX signature to predict the survival probability of patients with HCC. We also found that the model could predict the sensitivity of targeted drugs and immune cell infiltration, and the risk score was negatively correlated with CD8 + T cell infiltration. In summary, the CD8 + TEX signature of HCC was constructed for the prediction of prognosis and immune microenvironment by integrated analysis of bulk and scRNA-seq data., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-24-650/coif). The authors have no conflicts of interest to declare., (2024 AME Publishing Company. All rights reserved.)

CD8+ T cells are essential lymphocytes with cytotoxic properties for antitumor immunotherapy. However, during chronic infection or tumorigenesis, these cells often become dysfunctional with a gradually depleted ability to release cytokines and the exhibition of reduced cytotoxicity, the state referred to as “T-cell exhaustion” (Tex). This unique state was characterized by the increasing expression of inhibitory checkpoint receptors, and interventions targeting immune checkpoint blockades (ICBs) have been considered as a promising strategy to stimulate T-cell killing. Recent investigations have demonstrated that exhausted T cells not only display functional, metabolic, transcriptional, and epigenetic differences but also comprise a heterogeneous group of cells. In this review, we summarize the current findings on dynamic differentiation process during Tex heterogeneity development in cancer and chronic infection. We discuss how the responses to immunotherapy are determined by these distinct subsets and highlight prospective approaches for improving the efficacy of ICB therapy for cancer by leveraging the heterogeneity of T cells.

CD8 + T cells play a crucial role in anti-tumor immunity, but their function can be impaired by exhaustion induced by prolonged antigen stimulation. Mitochondrial dysfunction, a hallmark of the tumor microenvironment (TME), has been linked to various pathologies, but its specific role in CD8 + T cell exhaustion remains underexplored. Here, we established an in vitro model of CD8 + T cell exhaustion by co-culturing OVA-specific OT1 CD8 + T cells with OVA-expressing MC38 tumor cells. Next, we investigated the impact of mitochondrial dysfunction on exhaustion using pharmacological inhibitors targeting the electron transport chain. The role of the mitochondrial complex I component NDUFA10 was further examined through genetic knockout in CD8 + T cells using CRISPR-Cas9. Inhibition of the mitochondrial electron transport chain significantly accelerated CD8 + T cell exhaustion in vitro. Knockout of NDUFA10 in CD8 + T cells led to enhanced tumor growth and increased exhaustion of tumor-infiltrating CD8 + T cells in a Rag1 -/- tumor-bearing transfer model. This study highlights the critical role of mitochondrial function in regulating CD8 + T cell exhaustion and anti-tumor activity, providing new insights into the metabolic underpinnings of immune dysfunction in cancer., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)