CD4+ T Cell Help Is Required for the Formation of a Cytolytic CD8+ T Cell Subset that Protects against Chronic Infection and Cancer

Aging Compromises Terminal Differentiation Program of Cytotoxic Effector Lineage and Promotes Exhaustion in CD8+ T Cells Responding to Coronavirus Infection

T cell aging increases the risk of viral infection-related morbidity and mortality and reduces vaccine efficacy in the elderly. A major hallmark of T cell aging is the loss of quiescence and shift toward terminal differentiation during homeostasis. However, how aging impacts the differentiation program of virus-specific T cells during infection is unclear. Here, in a murine coronavirus (MHV) infection model with age-associated increased mortality, we demonstrate that aging impairs, instead of promoting, the terminal differentiation program of virus-specific CD8+ T cells. Upon infection, CD8+ and CD4+ T cells in old mice showed marked reduction in clonal expansion and upregulation of immune checkpoints associated with T cell exhaustion. Bulk and single-cell transcriptomics showed that aging upregulated the T cell exhaustion transcriptional program associated with TOX in virus-specific CD8+ T cells and shifted the myeloid compartment from immunostimulatory to immunosuppressive phenotype. In addition, aging downregulated the transcriptional program of terminally differentiated effector CD8+ T cells and diminished the CX3CR1+ cytotoxic effector lineage. Mechanistically, virus-specific CD8+ T cells from infected aged mice displayed defects in inducing transcription factors ZEB2 and KLF2, which were required for terminal differentiation of effector CD8+ T cells. Together, our study shows that aging impairs terminal differentiation and promotes exhaustion of virus-specific CD8+ T cells responding to coronavirus infection through dysregulating expression of lineage-defining transcription factors.

Mechanisms of CD8+ T cell exhaustion and its clinical significance in prognosis of anti-tumor therapies: A review

In recent years, immunotherapy has gradually become one of the main strategies for cancer treatment, with immune checkpoint inhibitors (ICIs) offering new possibilities for tumor therapy. However, some cancer patients exhibit low responses and resistance to ICIs treatment. T cell exhaustion, a process associated with tumor progression, refers to a subset of T cells that progressively lose effector functions and exhibit increased expression of inhibitory receptors. These exhausted T cells are considered key players in the therapeutic efficacy of immune checkpoint inhibitors. Therefore, understanding the impact of T cell exhaustion on tumor immunotherapy and the underlying mechanisms is critical for improving clinical treatment outcomes. Several elegant studies have provided insights into the prognostic value of exhausted T cells in cancers. In this review, we highlight the process of exhausted T cells and its predictive value in various cancers, as well as the relevant mechanisms behind it, providing new insights into the immunotherapy of cancer.

Gfi1 controls the formation of effector-like CD8+ T cells during chronic infection and cancer

During chronic infection and tumor progression, CD8+ T cells lose their effector functions and become exhausted. These exhausted CD8+ T cells are heterogeneous and comprised of progenitors that give rise to effector-like or terminally-exhausted cells. The precise cues and mechanisms directing subset formation are incompletely understood. Here, we show that growth factor independent-1 (Gfi1) is dynamically regulated in exhausted CD8+ T cells. During chronic LCMV Clone 13 infection, a previously under-described Ly108+CX3CR1+ subset expresses low levels of Gfi1 while other established subsets have high expression. Ly108+CX3CR1+ cells possess distinct chromatin profiles and represent a transitory subset that develops to effector-like and terminally-exhausted cells, a process dependent on Gfi1. Similarly, Gfi1 in tumor-infiltrating CD8+ T cells is required for the formation of terminally differentiated cells and endogenous as well as anti-CTLA-induced anti-tumor responses. Taken together, Gfi1 is a key regulator of the subset formation of exhausted CD8+ T cells.

Characterization and prognostic of CD8 + TIM3 + CD101 + T cells in glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM) is a pervasive and aggressive malignant brain tumor. In the tumor immune microenvironment, CD8 + TIM3 + CD101 + T cells (CCT cells) play a pivotal role in tumor progression and immune evasion. This study aimed to characterize differentially expressed genes (DEGs) in CCT cells, establish a prognostic model for GBM, and explore clinical implications.

METHODS

Analysis of data from TCGA, CGGA, and GEO databases included whole-genome expression profiles, clinical data, single nucleotide mutations, and single-cell RNA sequencing. DEGs were identified, and cell trajectories were constructed using Seurat, Monocle 2, and CellChat packages. Functional enrichment analysis was conducted with clusterProfiler, and a prognostic model was developed. Immune infiltration and drug sensitivity analyses were performed to evaluate therapeutic implications.

RESULTS

Eight distinct cell types were distinguished, encompassing T cells, macrophages, neurons, mural cells, endothelial cells, oligodendrocytes, fibroblasts, and B cells. Comparative analysis revealed differences in these cell types between GBM samples with new adjuvant therapy and initial diagnosis controls. Pseudotime analysis indicated CD8 + TIM3 + CD101-T cells as precursors to CCT cells, unveiling unique gene expression patterns during this transition. The prognostic model, incorporating 22 gene features via LASSO regression, demonstrated strong predictive ability through Receiver Operating Characteristic (ROC) curves. Analysis of 28 immune cell types revealed differences between high-risk and low-risk groups, providing insights into GBM's immune evasion mechanisms. Drug sensitivity analysis proposed potential therapeutic strategies for high-risk patients.

CONCLUSION

This study offers an in-depth understanding of CCT cells in GBM, introducing a novel prognostic model and suggesting promising therapeutic approaches.

Hdac1 as an early determinant of intermediate-exhausted CD8+ T cell fate in chronic viral infection

The exhausted CD8+ T (TEX) cells consist of distinct subsets including Tcf1+ stem-like, Tcf1-Cx3cr1+ intermediate (TEX-int) and Tcf1-Cx3cr1- terminally exhausted cells; yet, epigenetic determinants of TEX subset differentiation remain incompletely understood. Using chronic viral infection, we show that histone deacetylase 1 (Hdac1) was specifically required for the formation of antigen-specific TEX-int cells at the effector phase of responses. Single-cell transcriptomics validated that Hdac1 deficiency depleted TEX-int cells and revealed that Hdac1 was critical for positive regulation of TEX-int-characteristic genes, including Cx3cr1, Cxcr6, and Klf2. Furthermore, profiling chromatin accessibility landscape in TEX subsets demonstrated that loss of Hdac1 resulted in a prevalent increase in chromatin open state, as evidently observed at the exhaustion program genes, which were linked to induced expression of exhaustion-inducing Tox transcription factor, PD1 and Lag3 coinhibitory receptors in TEX cells. Hdac1 thus has dual regulatory functions: promoting TEX-int cell fate and preventing excessive activation of the exhaustion program to curtail uncontrolled virus replication.

Transient inhibition of type I interferon enhances CD8+ T cell stemness and vaccine protection

Developing vaccines that promote CD8+ T cell memory is a challenge for infectious disease and cancer immunotherapy. TCF-1+ stem cell-like memory CD8+ T (TSCM) cells are important determinants of long-lived memory. Yet, the developmental requirements for TSCM cell formation are unclear. Here, we identify the temporal window for type I interferon receptor (IFNAR) blockade to drive TSCM cell generation following viral infection and mRNA-lipid nanoparticle vaccination. We reveal a reversible developmental trajectory where transcriptionally distinct TSCM cells emerged from a transitional precursor of exhausted T cellular state concomitant with viral clearance. TSCM cell differentiation correlated with T cell retention within the lymph node paracortex due to disrupted CXCR3 chemokine gradient formation. These effects were linked to increased antigen load and a counterintuitive increase in IFNγ, which controlled cell location. Vaccination with the IFNAR blockade promoted TSCM cell differentiation and enhanced protection against chronic infection. These findings propose an approach to vaccine design whereby modulation of inflammation promotes memory formation and function.

Radiotherapy-immunomodulated nanoplatform triggers both hypoxic and normoxic tumor associated antigens generation for robust abscopal effect and sustained immune memory

Radiotherapy (RT) induced abscopal effect has garnered substantial attention, nevertheless, it is rarely observed in clinics, due to the tumor hypoxia-related radioresistance, inadequate immune stimulation, and immunosuppressive tumor microenvironment. Herein, we construct a radiotherapy-immunomodulated nanoplatform (THUNDER), which synergizes with RT and greatly triggers the generation of both hypoxic and normoxic tumor cells-derived tumor-associated antigens (TAAs), resulting in robust abscopal effect and sustained immune memory. THUNDER exhibits prolonged blood circulation and high tumor retention capacity. When combined with RT, THUNDER effectively destructs both hypoxic and normoxic tumor cells, facilitating the substantial release of TAAs from both cell types, which further promotes the maturation of dendritic cells (DCs), thus forming powerful immune stimulation and initiating systemic anti-tumor immunity. In murine models, the combination of THUNDER and RT efficiently suppresses the growth of triple-negative breast cancer. In addition, the further combination with PD-L1 blockade yields noteworthy suppression of distant metastasis and tumor recurrence, resulting in a 5.2-fold augmentation in CD8+ T lymphocytes within distant tumors and a 2.8-fold increase in effector memory T cells in the spleen. In conclusion, the radiotherapy-immunomodulated nanoplatform presents an effective strategy for combating tumor metastases and recurrence by eliciting both hypoxic and normoxic TAAs, offering a significant avenue for radioimmunotherapy.

Unravelling the modified T cell receptor through Gen-Next CAR T cell therapy in Glioblastoma: Current status and future challenges

PURPOSE

Despite current technological advancements in the treatment of glioma, immediate alleviation of symptoms can be catered by therapeutic modalities, including surgery, chemotherapy, and combinatorial radiotherapy that exploit aberrations of glioma. Additionally, a small number of target antigens, their heterogeneity, and immune evasion are the potential reasons for developing targeted therapies. This oncologic milestone has catalyzed interest in developing immunotherapies against Glioblastoma to improve overall survival and cure patients with high-grade glioma. The next-gen CAR-T Cell therapy is one of the effective immunotherapeutic strategies in which autologous T cells have been modified to express receptors against GBM and it modulates cytotoxicity.

METHODS

In this review article, we examine preclinical and clinical outcomes, and limitations as well as present cutting-edge techniques to improve the function of CAR-T cell therapy and explore the possibility of combination therapy.

FINDINGS

To date, several CAR T-cell therapies are being evaluated in clinical trials for GBM and other brain malignancies and multiple preclinical studies have demonstrated encouraging outcomes.

IMPLICATIONS

CAR-T cell therapy represents a promising therapeutic paradigm in the treatment of solid tumors but a few limitations include, the blood-brain barrier (BBB), antigen escape, tumor microenvironment (TME), tumor heterogeneity, and its plasticity that suppresses immune responses weakens the ability of this therapy. Additional investigation is required that can accurately identify the targets and reflect the similar architecture of glioblastoma, thus optimizing the efficiency of CAR-T cell therapy; allowing for the selection of patients most likely to benefit from immuno-based treatments.

Trifunctional antibody-cytokine fusion protein formats for tumor-targeted combination of IL-15 with IL-7 or IL-21

Cytokines from the common gamma chain receptor family, such as IL-15, IL-21 and IL-7, show promise for cancer immunotherapy and have been incorporated individually into the immunocytokine approach. However, their efficacy as monotherapy is limited. Here, we investigated the molecular design of tumor-directed trifunctional antibody-cytokine fusion proteins for a combinatorial approach of IL-15 with either IL-7 or IL-21. Various fusion proteins differing in antibody format, cytokine composition and arrangement were generated and cooperative cytokine activity assessed in solution and bound to target cells. Comparative analysis revealed that formats with cytokines positioned at the N- and C-termini of the antibody were more effective than those arranged in series. For the former design, cooperative effects were observed with the scFv-based (IL-15+IL-7) trifunctional fusion protein, primarily enhancing the proliferation of naive T cells, while the scFv/Fab-based (IL-15+IL-21) trifunctional fusion proteins enhanced IFN-y release and the cytotoxic potential of T cells. Combining cytokines in the two-in-one molecule approach was principally advantageous when bound to target cells. Greater potency in inducing JAK-STAT pathway activation highlighted the importance of cytokine colocalization for cooperative receptor activation. Compared to the Fab-based (IL-15+IL-21) format, the scFv-based (IL-15+IL-21) format displayed a tendency towards higher activity in targeted and lower activity in untargeted settings, emphasizing the targeted concept. Thus, this study underscores the importance of molecular design in developing trifunctional immunocytokines and identified the scFv-based trifunctional (IL-15+IL-21) fusion protein, with the antibody in the central position, as a particularly promising candidate for further drug development.

A specific microbial consortium enhances Th1 immunity, improves LCMV viral clearance but aggravates LCMV disease pathology in mice

Anti-viral immunity can vary tremendously from individual to individual but mechanistic understanding is still scarce. Here, we show that a defined, low complex bacterial community (OMM12) but not the general absence of microbes in germ-free mice leads to a more potent immune response compared to the microbiome of specific-pathogen-free (SPF) mice after a systemic viral infection with LCMV Clone-13. Consequently, gnotobiotic mice colonized with OMM12 have more severe LCMV-induced disease pathology but also enhance viral clearance in the intestinal tract. Mechanistically, single-cell RNA sequencing analysis of adoptively transferred virus-specific T helper cells and endogenous T helper cells in the intestinal tract reveal a stronger pro-inflammatory Th1 profile and a more vigorous expansion in OMM12 than SPF mice. Altogether, our work highlights the causative function of the intestinal microbiome for shaping adaptive anti-viral immunity with implications for vaccination strategies and anti-cancer treatment regimens.

Epigenetic landscapes drive CAR-T cell kinetics and fate decisions: Bridging persistence and resistance

Chimeric antigen receptor-T (CAR-T) cell therapy has revolutionized the treatment paradigm for B-cell malignancies and holds promise for solid tumor immunotherapy. However, CAR-T-cell therapy still faces many challenges, especially primary and secondary resistance. Some mechanisms of resistance, including CAR-T-cell dysfunction, an inhibitory tumor microenvironment, and tumor-intrinsic resistance, have been identified in previous studies. As insights into CAR-T-cell biology have increased, the role of epigenetic reprogramming in influencing the clinical effectiveness of CAR-T cells has become increasingly recognized. An increasing number of direct and indirect epigenetic targeting methods are being developed in combination with CAR-T-cell therapy. In this review, we emphasize the broad pharmacological links between epigenetic therapies and CAR-T-cell therapy, not only within CAR-T cells but also involving tumors and the tumor microenvironment. To elucidate the mechanisms through which epigenetic therapies promote CAR-T-cell therapy, we provide a comprehensive overview of the epigenetic basis of CAR-T-cell kinetics and differentiation, tumor-intrinsic factors and the microenvironment. We also describe some epigenetic strategies that have implications for CAR-T-cell therapy in the present and future. Because targeting epigenetics can have pleiotropic effects, developing more selective and less toxic targeting strategies and determining the optimal administration strategy in clinical trials are the focus of the next phase of research. In summary, we highlight the possible mechanisms and clinical potential of epigenetic regulation in CAR-T-cell therapy.

In vivo armed macrophages curb liver metastasis through tumor-reactive T-cell rejuvenation

Despite recent progress in cancer treatment, liver metastases persist as an unmet clinical need. Here, we show that arming liver and tumor-associated macrophages in vivo to co-express tumor antigens (TAs), IFNα, and IL-12 unleashes robust anti-tumor immune responses, leading to the regression of liver metastases. Mechanistically, in vivo armed macrophages expand tumor reactive CD8+ T cells, which acquire features of progenitor exhausted T cells and kill cancer cells independently of CD4+ T cell help. IFNα and IL-12 produced by armed macrophages reprogram antigen presenting cells and rewire cellular interactions, rescuing tumor reactive T cell functions. In vivo armed macrophages trigger anti-tumor immunity in distinct liver metastasis mouse models of colorectal cancer and melanoma, expressing either surrogate tumor antigens, naturally occurring neoantigens or tumor-associated antigens. Altogether, our findings support the translational potential of in vivo armed liver macrophages to expand and rejuvenate tumor reactive T cells for the treatment of liver metastases.

A realistic FastQ-based framework FastQDesign for ScRNA-seq study design issues

Single-cell RNA sequencing (scRNA-seq) has emerged as a powerful technology for characterizing transcriptomic profiles at single-cell resolution. It is crucial to consider both the number of cells and sequencing depth during library preparation. The existing methods are primarily simulation-based, rely on Unique Molecular Identifier (UMI) matrix, and have little context in the actual FastQ reads. Here we propose the first FastQ-based study design framework, named "FastQDesign," which leverages raw FastQ files from publicly available datasets as references and suggests an optimal design within a fixed budget. We demonstrate our framework through a synthetic dataset and applications to nine real-world datasets. Our study underscores the importance of an appropriate design to investigate the biology of heterogeneous cell populations and offers practical guidance considering cost-benefit trade-offs. A high-efficiency software suite is available at https://github.com/yuw444/FastQDesign .

Constructions and immunogenicity evaluations of two porcine epdemic diarrhea virus-like particle vaccines

Porcine epidemic diarrhea virus (PEDV), a swine enteropathogenic coronavirus, causing acute diarrhea, dehydration, and up to 100 % mortality in neonatal suckling piglets, leading to huge economic losses in the global swine industry. Vaccination remains the most promising and effective way to prevent and control PEDV. In this study, we produced PEDV virus-like particles (VLPs) composed of S, M, and E proteins with a baculovirus expression system and a mammalian expression system. The S, M, and E proteins were effectively expressed and successfully assembled into VLPs. Subsequently, S subunits and commercially inactivated vaccines were selected and compared with two VLPs vaccines for immune efficacy through mouse immunization. The results showed that both VLPs induced higher levels of IgG, IgA, and neutralizing antibody titers, lymphocyte proliferation indexes and T, B cell ratios. Compared with the baculovirus VLPs, the mammalian VLPs exhibited better effects in inducing neutralizing antibodies, lymphocyte proliferations, and IFN-γ. These data indicated that the PEDV VLPs vaccine constructed using the mammalian expression system has better immune efficacy and has the potential to serve as a novel PEDV vaccine.

Molecular Mechanisms Governing CD8 T Cell Differentiation and Checkpoint Inhibitor Response in Cancer

CD8 T cells play a critical role in antitumor immunity. However, over time, they often become dysfunctional or exhausted and ultimately fail to control tumor growth. To effectively harness CD8 T cells for cancer immunotherapy, a detailed understanding of the mechanisms that govern their differentiation and function is crucial. This review summarizes our current knowledge of the molecular pathways that regulate CD8 T cell heterogeneity and function in chronic infection and cancer and outlines how T cells respond to therapeutic checkpoint blockade. We explore how T cell-intrinsic and -extrinsic factors influence CD8 T cell differentiation, fate choices, and functional states and ultimately dictate their response to therapy. Identifying cells that orchestrate long-term antitumor immunity and understanding the mechanisms that govern their development and persistence are critical steps toward improving cancer immunotherapy.

An early precursor CD8+ T cell that adapts to acute or chronic viral infection

This study examines the origin and differentiation of stem-like CD8+ T cells that are essential for sustained T cell immunity in chronic viral infections and cancer and also have a key role in PD-1 directed immunotherapy1-10. These PD-1+TCF-1+TOX+ stem-like CD8+ T cells (also known as precursors of exhausted T cells8,9) have a distinct program that enables them to adapt to chronic antigen stimulation. Here, using the mouse model of chronic lymphocytic choriomeningitis virus (LCMV) infection, we find that virus-specific stem-like CD8+ T cells are generated early (day 5) during chronic infection, suggesting that this crucial fate commitment occurs irrespective of the infection outcome. Indeed, we find that nearly identical populations of stem-like CD8+ T cells were generated early during acute or chronic LCMV infection, and that antigen was essential for maintaining the stem-like phenotype. We performed reciprocal adoptive transfer experiments to determine the fate of these early stem-like CD8+ T cells after viral clearance versus persistence. After transfer of day 5 stem-like CD8+ T cells from chronically infected mice into acutely infected mice, these cells downregulated canonical markers of the chronic stem-like CD8+ T cells and expressed markers (CD127 and CD62L) associated with central memory CD8+ T cells. Reciprocally, when day 5 stem-like cells from acutely infected mice were transferred into chronically infected mice, these CD8+ T cells functioned like chronic resource cells and responded effectively to PD-1 therapy. These findings highlight the ability of these early PD-1+TCF-1+TOX+ stem-like CD8+ T cells to adapt their differentiation trajectory to either an acute or a chronic viral infection. Importantly, our study shows that the host is prepared a priori to deal with a potential chronic infection.

VDAC2 loss elicits tumour destruction and inflammation for cancer therapy

Tumour cells often evade immune pressure exerted by CD8+ T cells or immunotherapies through mechanisms that are largely unclear1,2. Here, using complementary in vivo and in vitro CRISPR-Cas9 genetic screens to target metabolic factors, we established voltage-dependent anion channel 2 (VDAC2) as an immune signal-dependent checkpoint that curtails interferon-γ (IFNγ)-mediated tumour destruction and inflammatory reprogramming of the tumour microenvironment. Targeting VDAC2 in tumour cells enabled IFNγ-induced cell death and cGAS-STING activation, and markedly improved anti-tumour effects and immunotherapeutic responses. Using a genome-scale genetic interaction screen, we identified BAK as the mediator of VDAC2-deficiency-induced effects. Mechanistically, IFNγ stimulation increased BIM, BID and BAK expression, with VDAC2 deficiency eliciting uncontrolled IFNγ-induced BAK activation and mitochondrial damage. Consequently, mitochondrial DNA was aberrantly released into the cytosol and triggered robust activation of cGAS-STING signalling and type I IFN response. Importantly, co-deletion of STING signalling components dampened the therapeutic effects of VDAC2 depletion in tumour cells, suggesting that targeting VDAC2 integrates CD8+ T cell- and IFNγ-mediated adaptive immunity with a tumour-intrinsic innate immune-like response. Together, our findings reveal VDAC2 as a dual-action target to overcome tumour immune evasion and establish the importance of coordinately destructing and inflaming tumours to enable efficacious cancer immunotherapy.

DNA-PKcs Dysfunction Enhances the Antitumor Activity of Radioimmunotherapy by Activating the cGAS-STING Pathway in HNSCC

Introduction

Combining radiotherapy (RT) with immunotherapy for head and neck squamous cell carcinoma (HNSCC) has limited effectiveness due to the DNA damage repair (DDR) pathway activated by ionizing radiation. DNA-PK, encoded by the PRKDC gene, plays a key role in this repair. The potential improvement of radioimmunotherapy by inhibiting the DDR pathway is still unclear.

Methods

The effectiveness of different treatments on tumor growth and survival was tested using the C3H/HeN mouse tumor model. Flow cytometry analyzed treatment-induced immunophenotypic changes. In vitro, Western blot and PCR confirmed the impact of combining immunotherapy with RT on the cGAS-STING pathway after DNA-PKcs dysfunction.

Results

The combination of a DNA-PK inhibitor (NU7441), radiation therapy, and a PD-1 checkpoint inhibitor showed improved antitumor effects and extended survival in mice. Adding NU7441 into the RT and immunotherapy regimen increased CD8+ T cell infiltration. PRKDC alterations or DNA-PKcs dysfunction increased IR-induced DNA breaks, activating the cGAS-STING pathway and boosting the anti-tumor immune response.

Conclusion

These findings suggest that targeting the DDR pathway may represent a promising therapeutic strategy and biomarker to improve the efficacy of radioimmunotherapy in HNSCC.

A polyvalent vaccine for selectively killing tumor-associated bacteria to prevent cancer metastasis

Specific bacteria, including Fusobacterium nucleatum, Streptococcus sanguis, Enterococcus faecalis, and Staphylococcus xylosus, have been identified as contributors to breast cancer metastasis. Due to limitations such as lack of selectivity, traditional antibiotic therapies face obstacles in eliminating intratumoral bacteria. Herein, this work proposes the use of therapeutic vaccines to selectively target and eliminate harmful bacteria within tumors. A multivalent vaccine encapsulating both insoluble and soluble bacterial antigens was developed, addressing the shortcomings of traditional antibacterial vaccines by balancing broad antigen coverage with effective immune activation. This vaccine induces robust downstream immune responses to eliminate F. nucleatum, S. sanguis, E. faecalis, and S. xylosus, demonstrating notable therapeutic and preventive efficacy in bacteria-induced cancer metastasis models. Unexpectedly, vaccinated infected mice showed even slower tumor metastasis than uninfected mice. Overall, this study validates the potential of nanovaccines in modulating the intratumoral microbiome for tumor therapy and highlights tumor-associated bacterial infections as potential promising antitumor targets.

Continuous expression of TOX safeguards exhausted CD8 T cell epigenetic fate

Although checkpoint blockade temporarily improves exhausted CD8 T (Tex) cell function, the underlying Tex epigenetic landscape remains largely unchanged, preventing durable Tex "reinvigoration" in cancer and chronic infections. The transcription factor TOX initiates Tex epigenetic programming, yet it remains unclear whether TOX continually preserves Tex biology after Tex establishment. Here, we demonstrated that induced TOX ablation in committed Tex cells resulted in apoptotic-driven loss of Tex cells, reduced expression of inhibitory receptors, and decreased terminal differentiation. Gene expression and epigenetic profiling revealed a critical role for TOX in maintaining chromatin accessibility and transcriptional patterns in committed Tex cells. Moreover, TOX removal endows established Tex cells with greater fate flexibility to differentiate into more functional effector-like T cells. Thus, continuous TOX expression in established Tex cells acts as a durable epigenetic barrier reinforcing the Tex developmental fate. TOX manipulation even after Tex establishment could therefore provide therapeutic opportunities to rewire Tex cells in chronic infections or cancer.

Epigenetic Regulation of CD8+ Effector T Cell Differentiation by PDCD5

Epigenetic modification plays a crucial role in establishing the transcriptional program that governs the differentiation of CD8+ effector T cells. However, the mechanisms by which this process is regulated at an early stage, prior to the expression of master transcription factors, are not yet fully understood. In this study, we have identified PDCD5 as an activation-induced molecule that is necessary for the proper differentiation and expansion of antigen-specific CD8+ effector T cells in a mouse model of chronic viral infection. The genetic deletion of Pdcd5 resulted in impaired differentiation and function of effector T cells, while T-cell activation, metabolic reprogramming, and the differentiation of memory/exhausted T cells were largely unaffected. At the molecular level, we observed reduced chromatin accessibility and transcriptional activity of Tbx21 and its regulated genes in Pdcd5-/- CD8+ T cells. We further identified that PRDM9 facilitates the H3K4me3 modification of genes associated with the effector phenotype in CD8+ T cells. The interaction between PDCD5 and PRDM9 promotes the nuclear translocation and lysine methyltransferase activity of PRDM9. Collectively, these findings highlight the crucial role of the PDCD5/PRDM9 axis in epigenetic reprogramming during the early stages of fate determination for effector CD8+ T cell fate.

Tumor-specific CD8+ T cells from the bone marrow resist exhaustion and exhibit increased persistence in tumor-bearing hosts as compared with tumor-infiltrating lymphocytes

BACKGROUND

Immunotherapy is now an integral aspect of cancer therapy. Strategies employing adoptive cell therapy (ACT) have seen the establishment of chimeric antigen receptor (CAR)-T cells using peripheral blood lymphocytes as well as tumor-infiltrating lymphocytes (TILs) with significant clinical results. The bone marrow (BM) is an immunological niche housing T cells with specificity for previously encountered antigens, including tumor-associated antigens from certain solid cancers. This study sought to improve our understanding of tumor-specific BM T cells in the context of solid tumors by comparing them with TILs, and to assess whether there is a rationale for using the BM as a source of T cells for ACT against solid malignancies.

METHODS

We used the murine B16 melanoma model examining both the endogenous OVA-specific T cell response using an OVA-specific tetramer or examining the OVA-specific response with OVA-specific transgenic CD8+ (OT-1) T cells. Specifically, we compared baseline intrinsic properties of TILs or BM T cells from tumor-bearing mice and their changes following adoptive transfer in the tumor and bone marrow (as well as other compartments when indicated).

RESULTS

In tumor-bearing mice, endogenous tumor-specific T cells could be detected in the BM early in the course of tumor progression and possessed a more stem-cell-like and memory phenotype in an unsupervised cluster analysis compared with TILs which appeared more exhausted. The BM and tumor microenvironments significantly impact the fate of T cells. Naïve OT-1 transferred T cells acquired an exhausted phenotype in the tumor but maintained a more memory-like phenotype in the BM with tumor progression. Importantly, in a competitive transfer experiment, BM T cells infiltrated the tumor more efficiently than TILs, displayed a higher polyfunctionality with interleukin-2, interferon-γ, tumor necrosis factor-α production and showed greater persistence compared with TILs.

CONCLUSIONS

T cells from the BM appear superior to TILs as a source of cells for cellular therapy. They possess a memory-enriched phenotype and exhibit improved effector function, greater persistence within a tumor-bearing host, and the capacity for increased tumor infiltration. These data provide a foundation for further exploring the BM as a source of tumor-specific T cells for ACT in solid malignancies.

A microRNA-regulated transcriptional state defines intratumoral CD8+ T cells that respond to immunotherapy

The rising incidence of advanced-stage colorectal cancer (CRC) and poor survival outcomes necessitate new and effective therapies. Immune checkpoint inhibitors (ICIs), specifically anti-PD-1 therapy, show promise, yet clinical determinants of a positive response are suboptimal. Here, we identify microRNA-155 (miR-155) as necessary for CD8+ T cell-infiltrated tumors through an unbiased in vivo CRISPR-Cas9 screen identifying functional tumor antigen-specific CD8+ T cell-expressed microRNAs. T cell miR-155 is required for anti-PD-1 responses and for a vital intratumor CD8+ T cell differentiation cascade by repressing Ship-1, inhibiting Tcf-1 and stemness, and subsequently enhancing Cxcr6 expression, anti-tumor immunity, and effector functions. Based on an underlying miR-155-dependent CD8+ T cell transcriptional profile, we identify a gene signature that predicts ICI responses across 12 diverse cancers. Together, our findings support a model whereby miR-155 serves as a central regulator of CD8+ T cell-dependent cancer immunity and ICI responses that may be leveraged for future therapeutics.

Comprehensive analysis of mitochondrial-related gene signature for prognosis, tumor immune microenvironment evaluation, and candidate drug development in colon cancer

Colon adenocarcinoma (COAD), a common digestive system malignancy, involves crucial alterations in mitochondria-related genes influencing tumor growth, metastasis, and immune evasion. Despite limited studies on prognostic models for these genes in COAD, we established a mitochondrial-related risk prognostic model, including nine genes based on available TCGA and MitoCarta 3.0 databases, and validated its predictive power. We investigated the tumor microenvironment (TME), immune cell infiltration, complex cell communication, tumor mutation burden, and drug sensitivity of COAD patients using R language, CellChat, and additional bioinformatic tools from single-cell and bulk-tissue sequencing data. The risk model revealed significant differences in immune cell infiltration between high-risk and low-risk groups, with the strongest correlation found between tissue stem cells and macrophages in COAD. The risk score exhibited a robust correlation with TME signature genes and immune checkpoint molecules. Integrating the risk score with the immune score, microsatellite status, or TMB through TIDE analysis enhanced the accuracy of predicting immunotherapy benefits. Predicted drug efficacy offered options for both high- and low-risk group patients. Our study established a novel mitochondrial-related nine-gene prognostic signature, providing insights for prognostic assessment and clinical decision-making in COAD patients.

Supercharging CAR-T cells through transcriptional and epigenetic armoring

Inspired by the remarkable success of CAR-T therapy in hematologic malignancies, research is increasingly focused on adapting this treatment for solid tumors. However, CAR-T efficacy remains limited due to its exhaustion and shortened persistence. Transcription factors and epigenetic modifications play pivotal roles in modulating T cell differentiation and functionality, which have been leveraged in numerous strategies to promote the formation of long-lasting memory cells with stem-like properties and supercharging CAR-T performance. This review highlights pivotal transcriptional factors, such as c-Jun and FOXO1, which enhance and sustain T cell effector function, diminishes exhaustion, and epigenetic regulators like TET2 and DNMT3A, whose knockout promotes memory T subsets formation. We explore their interconnections, downstream targets, biological impacts, and the potential application risks of certain candidates, providing a comprehensive theoretical framework for supercharging CAR-T therapies through transcriptional and epigenetic interventions.

Functional memory T cells are derived from exhausted clones and expanded by checkpoint blockade

Immune checkpoint blockade can facilitate tumor clearance by T cells, resulting in long term patient survival. However, the capacity of exhausted CD8+ T cells (Tex), present during chronic antigen exposure, to form memory after antigen clearance remains unclear. Here, we performed longitudinal single cell RNA/T cell receptor sequencing and ATAC-sequencing on antigen-specific T cells after the clearance of chronic lymphocytic choriomeningitis virus (LCMV) infection. These data revealed the formation of a robust population of memory CD8+ T cells that transcriptionally, epigenetically, and functionally resemble central memory T cells (Tcm) that form after clearance of acute infection. To lineage trace the origin and memory recall response of Tex-derived memory clones, we utilized T cell receptor sequencing over the course of primary infection and rechallenge. We show that chronic Tcm are a clonally distinct lineage of Tex derived from progenitor exhausted cells, persist long-term in the absence of antigen, and undergo rapid clonal expansion during rechallenge. Finally, we demonstrate that αPD-L1 immune checkpoint blockade after chronic LCMV infection preferentially expands clones which form Tcm after clearance. Together, these data support the concept that chronically stimulated T cells form bona fide functional memory T cells through an analogous differentiation pathway to acutely stimulated T cells, which may have significant implications for enhancing immune memory to cancer through checkpoint blockade and vaccination.

Durable lymphocyte subset elimination upon a single dose of AAV-delivered depletion antibody dissects immune control of chronic viral infection

To interrogate the role of specific immune cells in infection, cancer, and autoimmunity, immunologists commonly use monoclonal depletion antibodies (depletion-mAbs) or genetically engineered mouse models (GEMMs). To generate a tool that combines specific advantages and avoids select drawbacks of the two methods, we engineered adeno-associated viral vectors expressing depletion mAbs (depletion-AAVs). Single-dose depletion-AAV administration durably eliminated lymphocyte subsets in mice and avoided accessory deficiencies of GEMMs, such as marginal zone defects in B cell-deficient animals. Depletion-AAVs can be used in animals of different genetic backgrounds, and multiple depletion-AAVs can readily be combined. Exploiting depletion-AAV technology, we showed that B cells were required for unimpaired CD4+ and CD8+ T cell responses to chronic lymphocytic choriomeningitis virus (LCMV) infection. Upon B cell depletion, CD8+ T cells failed to suppress viremia, and they only helped resolve chronic infection when antibodies dampened viral loads. Our study positions depletion-AAVs as a versatile tool for immunological research.

Nutrient-driven histone code determines exhausted CD8+ T cell fates

Exhausted T cells (TEX) in cancer and chronic viral infections undergo metabolic and epigenetic remodeling, impairing their protective capabilities. However, the impact of nutrient metabolism on epigenetic modifications that control TEX differentiation remains unclear. We showed that TEX cells shifted from acetate to citrate metabolism by down-regulating acetyl-CoA synthetase 2 (ACSS2) while maintaining ATP-citrate lyase (ACLY) activity. This metabolic switch increased citrate-dependent histone acetylation, mediated by histone acetyltransferase KAT2A-ACLY interactions, at TEX signature genes while reducing acetate-dependent histone acetylation, dependent on p300-ACSS2 complexes, at effector and memory T cell genes. Nuclear ACSS2 overexpression or ACLY inhibition prevented TEX differentiation and enhanced tumor-specific T cell responses. These findings unveiled a nutrient-instructed histone code governing CD8+ T cell differentiation, with implications for metabolic- and epigenetic-based T cell therapies.

Neoadjuvant anti-4-1BB confers protection against spontaneous metastasis through low-affinity intratumor CD8 + T cells in triple-negative breast cancer

Neoadjuvant immunotherapy seeks to harness the primary tumor as a source of relevant tumor antigens to enhance systemic anti-tumor immunity through improved immunological surveillance. Despite having revolutionized the treatment of patients with high-risk early-stage triple-negative breast cancer (TNBC), a significant portion of patients remain unresponsive and succumb to metastatic recurrence post-treatment. Here, we found that optimally scheduled neoadjuvant administration of anti-4-1BB monotherapy was able to counteract metastases and prolong survival following surgical resection. Phenotypic and transcriptional profiling revealed enhanced 4-1BB expression on tumor-infiltrating intermediate (T int ), relative to progenitor (T prog ) and terminally exhausted (T term ) T cells. Furthermore, T int was enriched in low-affinity T cells. Treatment with anti-4-1BB drove clonal expansion of T int , with reduced expression of tissue-retention marker CD103 in T prog . This was accompanied by increased TCR clonotype sharing between paired tumors and pre-metastatic lungs. Further interrogation of sorted intratumor T cells confirmed enhanced T cell egress into circulation following anti-4-1BB treatment. In addition, gene signature extracted from anti-4-1BB treated T int was consistently associated with improved clinical outcomes in BRCA patients. Combinatorial neoadjuvant anti-4-1BB and ablation of tumor-derived CXCL16 resulted in enhanced therapeutic effect. These findings illustrate the intratumor changes underpinning the efficacy of neoadjuvant anti-4-1BB, highlighting the reciprocity between local tissue-retention and distant immunologic fortification, suggesting treatment can reverse the siphoning of intratumor T cells to primary tumor, enabling redistribution to distant tissues and subsequent protection against metastases.

A reappraisal of IL-9 in inflammation and cancer

While much is known about the functional effects of type 2 cytokines interleukin (IL)-4, IL-5 and IL-13 in homeostasis and disease, we still poorly understand the functions of IL-9. Chronic inflammation seen in allergic diseases, autoimmunity and cancer is however frequently accompanied by overproduction of this elusive type 2 cytokine. Initially identified as a T cell and mast cell growth factor, and later as the hallmark cytokine defining TH9 cells, we now know that IL-9 is produced by multiple innate and adaptive immune cells. Recent evidence suggests that IL-9 controls discrete aspects of the allergic cascade, cellular responses of immune and stromal cells, cancer progression, tolerance and immune escape. Despite functioning as a pleiotropic cytokine in mucosal environments, like the lungs, the direct and indirect cellular targets of IL-9 are still not well characterized. Here, we discuss IL-9's cellular senders and receivers, focusing on asthma and cancer. Moreover, we review current research directions and the outlook of targeted therapy centered around the biology of IL-9.

Neoantigen-Displaying Protein Nanoparticles as a Therapeutic Cancer Vaccine Against Melanoma

Although interest in peptide-based cancer vaccines has surged in the era of personalized immunotherapy enabled by the discovery of neoantigens, the effective generation of neoantigen-specific T cell responses has been limited. Here, a Brucella BP26 protein-based nanoparticle displaying the MHC class II-restricted melanoma neoantigen, M30, is reported for use as a therapeutic cancer vaccine. Genetic engineering of 10 tandem repeats of the M30 neoepitope to a BP26 monomer results in the self-assembled, neoantigen-displaying protein nanoparticles (BP26-M30 NPs). Subcutaneous immunization of mice with BP26-M30 NPs/CpG adjuvant leads to the activation and maturation of antigen-presenting cells in draining local lymph nodes and elicits M30-specific CD4+ T cell immune responses and immunological memory. In a mouse model of aggressive B16-F10 melanoma, immunization with BP26-M30 NPs/CpG significantly inhibits the growth of established tumors. These findings suggest that the BP26-based self-assembled protein nanoparticle has the potential to be used as a cancer vaccine platform for personalized cancer immunotherapy.

Dynamic Tracking of Tumor Microenvironment Modulation Using Kaede Photoconvertible Transgenic Mice Unveils New Biological Properties of Viral Immunotherapy

SIGNIFICANCE

This study utilized a novel photoconvertible mouse tumor model to track immune cell trafficking upon treatment with an investigational viral immunotherapy (CAN-2409), revealing enhanced T-cell responses after viral immunotherapy associated with local proliferation of T cells within tumors that could further enhance antitumor efficacy in combination with immune checkpoint inhibitors. These findings define temporally and spatially distinct interactions of immune cells that could be harnessed by novel therapeutics.

Stem-like memory and precursors of exhausted T cells share a common progenitor defined by ID3 expression

Stem-like T cells are attractive immunotherapeutic targets in patients with cancer given their ability to proliferate and differentiate into effector progeny. Thus, identifying T cells with enhanced stemness and understanding their developmental requirements are of broad clinical and therapeutic interest. Here, we demonstrate that during acute infection, the transcriptional regulator inhibitor of DNA binding 3 (ID3) identifies stem-like T cells that are uniquely adapted to generate precursors of exhausted T (Tpex) cells in response to chronic infection or cancer. Expression of ID3 itself enables Tpex cells to sustain T cell responses in chronic infection or cancer, whereas loss of ID3 results in impaired maintenance of CD8 T cell immunity. Furthermore, we demonstrate that interleukin-1 (IL-1) family members, including IL-36β and IL-18, promote the generation of ID3+ T cells that mediate superior tumor control. Overall, we identify ID3 as a common denominator of stem-like T cells in both acute and chronic infections that is specifically required to sustain T cell responses to chronic stimulation.

The ending is not the end: Lymph node metastasis in oral squamous cell carcinoma

Lymph node metastasis is an important biological feature of oral squamous cell carcinoma, bearing poorly prognostic implications. However, the role of lymph node metastasis in cancer progression remains inconclusive. On the one hand, lymph nodes are pivotal sites for initiating specific immunity, which is crucial for maintaining antitumor immune response. On the other hand, they also serve as primary conduits for tumor metastasis, with lymph node colonization potentially inducing systemic immune dysfunction, thereby further promoting tumor progression. Considering this paradoxical role of lymph nodes, comprehending their impact on the primary tumor and immunity becomes paramount. Furthermore, leveraging these distinctive attributes of lymph nodes presents novel avenues for enhancing current therapeutic strategies against oral squamous cell carcinoma. This review summarizes the anatomical and molecular profiles of lymph node metastasis in oral squamous cell carcinoma, elucidating how lymphatic involvement compromises antitumor immunity, thus facilitating primary tumor and distant metastases. Additionally, it explores avenues for harnessing these mechanisms to optimize clinical interventions.

Integrative Single-Cell and Bulk RNA Sequencing Identifies a Macrophage-Related Prognostic Signature for Predicting Prognosis and Therapy Responses in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common malignant tumors, characterized by a high incidence and mortality rate. Macrophages, as a key immune cell type within the tumor microenvironment (TME), play a key role in tumor immune evasion and the progression of CRC. Therefore, identifying macrophage biomarkers is of great significance for predicting the prognosis of CRC patients. This study integrates scRNA-seq and bulk RNA-seq data to identify macrophage-related genes in CRC. By applying a comprehensive machine learning framework, the macrophage-related prognostic signature (MRPS) was constructed by 15 macrophage-related genes with prognostic values. The MRPS demonstrated strong predictive performance across multiple datasets, effectively stratifying high-risk and low-risk patients in terms of overall survival (OS) and disease-specific survival (DSS). Furthermore, immune analysis revealed significant differences between the high-risk and low-risk groups in immune cell infiltration levels and immune checkpoint gene expression patterns. Drug screening identified several small molecules, including Bortezomib and Mitoxantrone, as potential therapeutic options for high-risk patients. Pseudotime trajectory analysis further highlighted the potential role of genes comprising the MRPS in macrophage differentiation. This study provides a powerful tool for personalized prognosis prediction in CRC patients, offering new insights into macrophage-driven mechanisms in tumor progression and potential therapeutic strategies.

Architects of immunity: How dendritic cells shape CD8+ T cell fate in cancer

Immune responses against cancer are dominated by T cell exhaustion and dysfunction. Recent advances have underscored the critical role of early priming interactions in establishing T cell fates. In this review, we explore the importance of dendritic cell (DC) signals in specifying CD8+ T cell fates in cancer, drawing on insights from acute and chronic viral infection models. We highlight the role of DCs in lymph nodes and tumors in maintaining stem-like CD8+ T cells, which are critical for durable antitumor immune responses. Understanding how CD8+ T cell fates are determined will enable the rational design of immunotherapies, particularly therapeutic cancer vaccines, that can modulate DC-T cell interactions to generate beneficial CD8+ T cell fates.

Is modulation of immune checkpoints on glioblastoma-infiltrating myeloid cells a viable therapeutic strategy?

The field of immunology has traditionally focused on immune checkpoint modulation of adaptive immune cells. However, many malignancies such as glioblastoma are mostly devoid of T cells and rather are enriched with immunosuppressive myeloid cells of the innate immune system. While some immune checkpoint targets are shared between adaptive and innate immunity, myeloid-specific checkpoints could also serve as potential therapeutics. To better understand the impact of immune checkpoint blockade on myeloid cells, we systematically summarize the current literature focusing on the direct immunological effects of PD-L1/PD-1, CD24/Siglec-10, collagen/LAIR-1, CX3CL1/CX3CR1, and CXCL10/CXCR3. By synthesizing the molecular mechanisms and the translational implications, we aim to prioritize agents in this category of therapeutics for glioblastoma.

KLF2 maintains lineage fidelity and suppresses CD8 T cell exhaustion during acute LCMV infection

Naïve CD8 T cells have the potential to differentiate into a spectrum of functional states during an immune response. How these developmental decisions are made and what mechanisms exist to suppress differentiation toward alternative fates remains unclear. We employed in vivo CRISPR-Cas9-based perturbation sequencing to assess the role of ~40 transcription factors (TFs) and epigenetic modulators in T cell fate decisions. Unexpectedly, we found that knockout of the TF Klf2 resulted in aberrant differentiation to exhausted-like CD8 T cells during acute infection. KLF2 was required to suppress the exhaustion-promoting TF TOX and to enable the TF TBET to drive effector differentiation. KLF2 was also necessary to maintain a polyfunctional tumor-specific progenitor state. Thus, KLF2 provides effector CD8 T cell lineage fidelity and suppresses the exhaustion program.

Efficacy of CTLA-4 checkpoint therapy is dependent on IL-21 signaling to mediate cytotoxic reprogramming of PD-1+CD8+ T cells

The mechanisms underlying the efficacy of anti-programmed cell death protein 1 (PD-1) and anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) therapy are incompletely understood. Here, by immune profiling responding PD-1+CD8+ T (TResp) cell populations from patients with advanced melanoma, we identified differential programming of TResp cells in response to combination therapy, from an exhausted toward a more cytotoxic effector program. This effect does not occur with anti-PD-1 monotherapy. Single-cell transcriptome and T cell receptor repertoire analysis was used to identify altered effector programming of expanding PD-1+CD8+ T cell clones with distinct regulon usage, STAT1 and STAT3 utilization and antitumor specificity connected to interleukin (IL)-21 signaling in combination and anti-CTLA-4 monotherapy. Therapeutic efficacy of CTLA-4 blockade was lost in B16F10 melanoma models with either Il21r- deficiency or anti-IL-21 receptor blockade. Together, these results show how IL-21 signaling to TResp is critical for anti-CTLA-4-based checkpoint therapies and highlight major signaling differences to anti-PD-1 monotherapy.

Construction of an Oxidative Stress Risk Model to Analyze the Correlation Between Liver Cancer and Tumor Immunity

BACKGROUND

Hepatocellular carcinoma (HCC) remains one of the most lethal cancers globally. Despite advancements in immunotherapy, the prognosis for patients with HCC continues to be poor. As oxidative stress plays a significant role in the onset and progression of various diseases, including metabolism-related HCC, comprehending its mechanism in HCC is critical for effective diagnosis and treatment.

METHODS

This study utilized the TCGA dataset and a collection of oxidative stress genes to identify the expression of oxidative stress-related genes in HCC and their association with overall survival using diverse bioinformatics methods. A novel prognostic risk model was developed, and the TCGA cohort was divided into high-risk and low-risk groups based on each tumor sample's risk score. Levels of immune cell infiltration and the expression of immune checkpoint-related genes in different risk subgroups were analyzed to investigate the potential link between tumor immunity and oxidative stress-related features. The expression of model genes in actual samples was validated through immunohistochemistry, and their mRNA and protein expression levels were measured in cell cultures.

RESULTS

Four oxidative stress-related genes (EZH2, ANKZF1, G6PD, and HMOX1) were identified and utilized to create a predictive risk model for HCC patient overall survival, which was subsequently validated in an independent cohort. A correlation was found between the expression of these prognostic genes and the infiltration of tumor immune cells. Elevated expression of EZH2, ANKZF1, G6PD, and HMOX1 was observed in both HCC tissues and cell lines.

CONCLUSION

The combined assessment of EZH2, ANKZF1, G6PD, and HMOX1 gene expression can serve as an oxidative stress risk model for assessing HCC prognosis. Furthermore, there is a correlation between the expression of these risk model genes and tumor immunity.

Myeloid cells meet CD8+ T cell exhaustion in cancer: What, why and how

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.

Flt3L enhances clonal diversification and selective expansion of intratumoral CD8+ T cells while differentiating into effector-like cells

PD-1 blockade enhances anti-tumoral CD8+ T cell responses via type 1 conventional dendritic cells (cDC1s), but how cDC1s change the properties of intratumoral CD8+ T cells remains to be determined. Here, we identified two populations of intratumoral CD8+ T cells distinguished by their expression of asialo-ganglio-N-tetraosylceramide (asGM1). asGM1neg and asGM1posCD8+ T cells show enriched expression of genes characteristic for precursor exhausted T (Tpex) cells and terminally exhausted T (Tex) cells, respectively. The in situ expression of Flt3L or inhibition of PD-1 each promote the differentiation of asGM1negCD8+ T cells into asGM1posCD8+ T cells via interleukin-12 (IL-12) while also increasing the expression of Tpex and effector-like T cell-associated genes and their effector functions. Both interventions selectively expand CD8+ T cells, but only Flt3L expression broadens their T cell receptor (TCR) repertoire. These data indicate the distinct role of Flt3L in diversifying the TCR repertoire, offering potential solutions for immune checkpoint blockade-resistant cancers.

Spatial Dynamics of T- and B-Cell Responses Predicts Clinical Outcome of Resectable and Unresectable Hepatocellular Carcinoma

PURPOSE

Immunotherapies have led to a paradigm shift in the treatment of hepatocellular carcinoma (HCC). Studies have revealed the single-cell catalogs of tumor-infiltrating immune cells and the trajectories of their differentiation. Nevertheless, the spatial distribution of these immune cells with distinct phenotypes in the tumor microenvironment and their clinicopathologic significance in resectable and unresectable HCCs are still largely unclear.

EXPERIMENTAL DESIGN

We analyzed the spatial dynamics of intratumoral CD4 and CD8 T cells and their association with B and plasma cells using 283 surgically resected HCC samples, 58 unresectable HCC samples before combined immunotherapy [atezolizumab plus bevacizumab (Atezo + Bev)], and autopsy specimens from 50 cases of advanced-stage HCC through multiplex IHC combined with transcriptomic and driver gene mutation analyses. Classification based on the spatial dynamics of T- and B-cell responses (refined immunosubtype) was developed, and its clinicopathologic significance was analyzed.

RESULTS

We found that stem-like CD4 and CD8 T cells were mainly observed in T-cell aggregates and T-cell zone of tertiary lymphoid structure (TLS). The differentiation of T follicular helper cells was associated with the development of TLS, whereas the differentiation of CXCL13-expressing CD4 TCXCL13 cells with a phenotype resembling T peripheral helper cells was associated with the development of the lymphoplasmacytic microenvironment. The refined immunosubtype could predict clinical outcomes of resectable HCC after surgery and unresectable HCC after Atezo + Bev therapy. The immune microenvironment of metastatic lesions tended to reflect those of primary lesions.

CONCLUSIONS

We revealed the spatial dynamics of T- and B-cell responses in HCC, which is closely associated with the clinical outcome after surgical resection or Atezo + Bev therapy.

PI3K/AKT/mTOR and PD‑1/CTLA‑4/CD28 pathways as key targets of cancer immunotherapy (Review)

T cells play an important role in cancer, and energy metabolism can determine both the proliferation and differentiation of T cells. The inhibition of immune checkpoint molecules programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA-4) are a promising cancer treatment. In recent years, research on CD28 has increased. Although numerous reports involve CD28 and its downstream PI3K/AKT/mTOR signaling mechanisms in T cell metabolism, they have not yet been elucidated. A literature search strategy was used for the databases PubMed, Scopus, Web of Science and Cochrane Library to ensure broad coverage of medical and scientific literature, using a combination of keywords including, but not limited to, 'lung cancer' and 'immunotherapy'. Therefore, the present study reviewed the interaction and clinical application of the PD-1/CTLA-4/CD28 and PI3K/AKT/mTOR pathways in T cells, aiming to provide a theoretical basis for immunotherapy in clinical cancer patients.

CX3CR1+CD8+ T cells: Key players in antitumor immunity

CX3CR1 functions as the specific receptor for the chemokine CX3CL1, demonstrating expression across a broad spectrum of immune cells. This underscores its pivotal role in communication and response mechanisms within the immune system. Upon engagement with CX3CL1, CX3CR1 initiates a cascade of downstream signaling pathways that regulate various biological functions. In the context of tumor progression, the intricate and inhibitory nature of the tumor microenvironment presents a significant challenge to current clinical treatment techniques. This review aims to comprehensively explore the tumor-destructive potential shown by CX3CR1+CD8+ T cells. Simultaneously, it investigates the promising prospects of utilizing CX3CR1 in future tumor immunotherapies.

The redox sensor KEAP1 facilitates adaptation of T cells to chronic antigen stimulation by preventing hyperactivation

During persistent antigen stimulation, exhausted CD8+ T cells are continuously replenished by self-renewing stem-like T cells. However, how CD8+ T cells adapt to chronic stimulation remains unclear. Here, we show that persistent antigen stimulation primes chromatin for regulation by the redox-sensing KEAP1-NRF2 pathway. Loss of KEAP1 in T cells impaired control of chronic viral infection. T cell-intrinsic KEAP1 suppressed NRF2 to promote expansion and persistence of virus-specific CD8+ T cells, drive a stem-like T cell response, down-regulate immune checkpoint molecules, and limit T cell receptor (TCR) hyperactivation and apoptosis. NRF2 epigenetically derepressed BACH2 targets and opposed a stem-like program driven by BACH2. In exhausted T cells induced by tonic GD2 chimeric antigen receptor (CAR) signaling, the effects of KEAP1 deficiency were rescued by inhibiting proximal TCR signaling. Enhancing mitochondrial oxidation improved the expansion and survival of KEAP1-deficient CD8+ GD2 CAR T cells and up-regulated markers associated with stem-like cells. Thus, the KEAP1-NRF2 axis regulates stem-like CD8+ T cells and long-term T cell immunity during chronic antigen exposure.

TET2 regulates early and late transitions in exhausted CD8+ T cell differentiation and limits CAR T cell function

CD8+ T cell exhaustion hampers control of cancer and chronic infections and limits chimeric antigen receptor (CAR) T cell efficacy. Targeting TET2 in CAR T cells provides therapeutic benefit; however, TET2's role in exhausted T cell (TEX) development is unclear. In chronic lymphocytic choriomeningitis virus (LCMV) infection, TET2 drove conversion from stem cell-like TEX progenitors toward terminally differentiated and effector (TEFF)-like TEX. TET2 also enforced a terminally differentiated state in the early bifurcation between TEFF and TEX, indicating broad roles for TET2 in acquisition of effector biology. To exploit the therapeutic potential of TET2, we developed clinically actionable TET2-targeted CAR T cells by disrupting TET2 via knock-in of a safety switch alongside CAR knock-in at the TRAC locus. TET2-targeted CAR T cells exhibited restrained terminal exhaustion in vitro and enhanced antitumor responses in vivo. Thus, TET2 regulates fate transitions in TEX differentiation and can be targeted with a safety mechanism in CAR T cells for improved tumor control.

CD8+ T-cell exhaustion: Impediment to triple-negative breast cancer (TNBC) immunotherapy

CD8+ T-cell exhaustion has been identified as a significant contributor to immunosuppression and immune escape in triple-negative breast cancer (TNBC). Dysfunction due to cell exhaustion is characterized by reduced effector capacity and sustained expression of inhibitory receptors (IRs). The factors contributing to CD8+ T-cell exhaustion are multifaceted, encompassing external influences such as the upregulation of IRs, reduction of effector cytokines, and internal changes within the immune cell, including transcriptomic alterations, epigenetic landscape remodeling, and metabolomic shifts. The impact of the altered TNBC tumor microenvironment (TME) on Tex is also a critical consideration. The production of exhausted CD8+ T-cells (CD8+ Tex) is positively correlated with poor prognosis and reduced response rates to immunotherapy in TNBC patients, underscoring the urgent need for the development of novel TNBC immunotherapeutic strategies that target the mechanisms of CD8+ T-cell exhaustion. This review delineates the dynamic trajectory of CD8+ T-cell exhaustion development in TNBC, provides an update on the latest research advancements in understanding its pathogenesis, and offers insights into potential immunotherapeutic strategies.

Cell Identity and Spatial Distribution of PD-1/PD-L1 Blockade Responders

The programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) axis inhibits T cell activity, impairing anti-tumor immunity. Blocking this axis with therapeutic antibodies is one of the most promising anti-tumor immunotherapies. It has long been recognized that PD-1/PD-L1 blockade reinvigorates exhausted T (TEX) cells already present in the tumor microenvironment (TME). However, recent advancements in high-throughput gene sequencing and bioinformatic tools have provided researchers with a more granular and dynamic insight into PD-1/PD-L1 blockade-responding cells, extending beyond the TME and TEX populations. This review provides an update on the cell identity, spatial distribution, and treatment-induced spatiotemporal dynamics of PD-1/PD-L1 blockade responders. It also provides a synopsis of preliminary reports of potential PD-1/PD-L1 blockade responders other than T cells to depict a panoramic picture. Important questions to answer in further studies and the translational and clinical potential of the evolving understandings are also discussed.