TCF1 in T cell immunity: a broadened frontier

Urine scRNAseq reveals new insights into the bladder tumor immune microenvironment

Due to bladder tumors' contact with urine, urine-derived cells (UDCs) may serve as a surrogate for monitoring the tumor microenvironment (TME) in bladder cancer (BC). However, the composition of UDCs and the extent to which they mirror the tumor remain poorly characterized. We generated the first single-cell RNA-sequencing of BC patient UDCs with matched tumor and peripheral blood mononuclear cells (PBMC). BC urine was more cellular than healthy donor (HD) urine, containing multiple immune populations including myeloid cells, CD4+ and CD8+ T cells, natural killer (NK) cells, B cells, and dendritic cells (DCs) in addition to tumor and stromal cells. Immune UDCs were transcriptionally more similar to tumor than blood. UDCs encompassed cytotoxic and activated CD4+ T cells, exhausted and tissue-resident memory CD8+ T cells, macrophages, germinal-center-like B cells, tissue-resident and adaptive NK cells, and regulatory DCs found in tumor but lacking or absent in blood. Our findings suggest BC UDCs may be surrogates for the TME and serve as therapeutic biomarkers.

Pan-cancer mapping of single CD8+ T cell profiles reveals a TCF1:CXCR6 axis regulating CD28 co-stimulation and anti-tumor immunity

CD8+ T cells must persist and function in diverse tumor microenvironments to exert their effects. Thus, understanding common underlying expression programs could better inform the next generation of immunotherapies. We apply a generalizable matrix factorization algorithm that recovers both shared and context-specific expression programs from diverse datasets to a single-cell RNA sequencing (scRNA-seq) compendium of 33,161 CD8+ T cells from 132 patients with seven human cancers. Our meta-single-cell analyses uncover a pan-cancer T cell dysfunction program that predicts clinical non-response to checkpoint blockade in melanoma and highlights CXCR6 as a pan-cancer marker of chronically activated T cells. Cxcr6 is trans-activated by AP-1 and repressed by TCF1. Using mouse models, we show that Cxcr6 deletion in CD8+ T cells increases apoptosis of PD1+TIM3+ cells, dampens CD28 signaling, and compromises tumor growth control. Our study uncovers a TCF1:CXCR6 axis that counterbalances PD1-mediated suppression of CD8+ cell responses and is essential for effective anti-tumor immunity.

The impact of tertiary lymphoid structures on tumor prognosis and the immune microenvironment in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a common malignancy whose prognosis and treatment outcome are influenced by many factors. Some studies have found that tertiary lymphoid structures (TLSs) in cancer may contribute to prognosis and the prediction of immunotherapy efficacy However, the combined role of TLSs in NSCLC remains unclear. We accessed The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases to obtain mRNA sequencing data and clinical information as the TCGA cohort, and used our own sample of 53 advanced NSCLC as a study cohort. The samples were divided into TLS+ and TLS- groups by pathological tissue sections. Patients of the TLS+ group had a better OS (p = 0.022), PFS (p = 0.042), and DSS (p = 0.004) in the TCGA cohort, and the results were confirmed by the study cohort (PFS, p = 0.012). Furthermore, our result showed that the count and size of TLSs are closely associated with the efficacy of immunotherapy. In addition, the TLS+ group was associated with better immune status and lower tumor mutation load. In the tumor microenvironment (TME), the expression levels of CD4+ T cells and CD8+ T cells of different phenotypes were associated with TLSs. Overall, TLSs are a strong predictor of survival and immunotherapeutic efficacy in advanced NSCLC, and T cell-rich TLSs suggest a more ordered and active immune response site, which aids in the decision-making and application of immunotherapy in the clinic.

Comparison of preclinical efficacy of immunotherapies against HPV-induced cancers

INTRODUCTION

Persistent infections with the human papilloma viruses, HPV16 and HPV18, are associated with multiple cancers. Although prophylactic vaccines that induce HPV-neutralizing antibodies are effective against primary infections, they have no effect on HPV-mediated malignancies against which there is no approved immuno-therapy. Active research is ongoing on immunotherapy of these cancers.

AREAS COVERED

In this review, we compared the preclinical efficacy of vaccine platforms used to treat HPV-induced tumors in the standard model of mice grafted with TC-1 cells, which express the HPV16 E6 and E7 oncoproteins. We searched for the key words, 'HPV,' 'vaccine,' 'therapy,' 'E7,' 'tumor,' 'T cells' and 'mice' for the period from 2005 to 2023 in PubMed and found 330 publications. Among them, we selected the most relevant to extract preclinical antitumor results to enable cross-sectional comparison of their efficacy.

EXPERT OPINION SECTION

We compared these studies for HPV antigen design, immunization regimen, immunogenicity, and antitumor effect, considering their drawbacks and advantages. Among all strategies used in murine models, certain adjuvanted proteins and viral vectors showed the strongest antitumor effects, with the use of lentiviral vectors being the only approach to result in complete tumor eradication in 100% of experimental individuals while providing the longest-lasting memory.

PVRIG is Expressed on Stem-Like T Cells in Dendritic Cell-Rich Niches in Tumors and Its Blockade May Induce Immune Infiltration in Non-Inflamed Tumors

Cancers that are poorly immune infiltrated pose a substantial challenge, with current immunotherapies yielding limited clinical success. Stem-like memory T cells (TSCM) have been identified as a subgroup of T cells that possess strong proliferative capacity and that can expand and differentiate following interactions with dendritic cells (DCs). In this study, we explored the pattern of expression of a recently discovered inhibitory receptor poliovirus receptor-related immunoglobulin domain protein (PVRIG) and its ligand, poliovirus receptor-related ligand 2 (PVRL2), in the human tumor microenvironment. Using spatial and single-cell RNA transcriptomics data across diverse cancer indications, we found that among the T-cell checkpoints, PVRIG is uniquely expressed on TSCM and PVRL2 is expressed on DCs in immune aggregate niches in tumors. PVRIG blockade could therefore enhance TSCM-DC interactions and efficiently drive T-cell infiltration to tumors. Consistent with these data, following PVRIG blockade in patients with poorly infiltrated tumors, we observed immune modulation including increased tumor T-cell infiltration, T-cell receptor (TCR) clonality, and intratumoral T-cell expansion, all of which were associated with clinical benefit. These data suggest PVRIG blockade as a promising strategy to induce potent antitumor T-cell responses, providing a novel approach to overcome resistance to immunotherapy in immune-excluded tumors.

Stem-like T cells are associated with the pathogenesis of ulcerative colitis in humans

To understand the role of T cells in the pathogenesis of ulcerative colitis (UC), we analyzed colonic T cells isolated from patients with UC and controls. Here we identified colonic CD4+ and CD8+ T lymphocyte subsets with gene expression profiles resembling stem-like progenitors, previously reported in several mouse models of autoimmune disease. Stem-like T cells were increased in inflamed areas compared to non-inflamed regions from the same patients. Furthermore, TCR sequence analysis indicated stem-like T cells were clonally related to proinflammatory T cells, suggesting their involvement in sustaining effectors that drive inflammation. Using an adoptive transfer colitis model in mice, we demonstrated that CD4+ T cells deficient in either BCL-6 or TCF1, transcription factors that promote T cell stemness, had decreased colon T cells and diminished pathogenicity. Our results establish a strong association between stem-like T cell populations and UC pathogenesis, highlighting the potential of targeting this population to improve clinical outcomes.

Regulation of 3D genome organization during T cell activation

Within the three-dimensional (3D) nuclear space, the genome organizes into a series of orderly structures that impose important influences on gene regulation. T lymphocytes, crucial players in adaptive immune responses, undergo intricate transcriptional remodeling upon activation, leading to differentiation into specific effector and memory T cell subsets. Recent evidence suggests that T cell activation is accompanied by dynamic changes in genome architecture at multiple levels, providing a unique biological context to explore the functional relevance and molecular mechanisms of 3D genome organization. Here, we summarize recent advances that link the reorganization of genome architecture to the remodeling of transcriptional programs and conversion of cell fates during T cell activation and differentiation. We further discuss how various chromatin architecture regulators, including CCCTC-binding factor and several transcription factors, collectively modulate the genome architecture during this process.

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 T (T SCM ) cells are important determinants of long-lived memory. Yet, the developmental requirements for T SCM formation are unclear. Here, we identify the temporal window for type I interferon (IFN-I) receptor (IFNAR) blockade to drive T SCM cell generation. T SCM cells were transcriptionally distinct and emerged from a transitional precursor of exhausted (T PEX ) cellular state concomitant with viral clearance. T SCM differentiation correlated with T cell retention within the lymph node paracortex, due to increased CXCR3 chemokine abundance which disrupted gradient formation. These affects were due a counterintuitive increase in IFNψ, which controlled cell location. Combining IFNAR inhibition with mRNA-LNP vaccination promoted specific T SCM differentiation and enhanced protection against chronic infection. These finding propose a new approach to vaccine design whereby modulation of inflammation promotes memory formation and function.

HIGHLIGHTS

Early, transient inhibition of the type I interferon (IFN) receptor (IFNAR) during acute viral infection promotes stem cell-like memory T (T SCM ) cell differentiation without establishing chronic infection. T SCM and precursor of exhausted (T PEX ) cellular states are distinguished transcriptionally and by cell surface markers. Developmentally, T SCM cell differentiation occurs via a transition from a T PEX state coinciding with viral clearance. Transient IFNAR blockade increases IFNψ production to modulate the ligands of CXCR3 and couple T SCM differentiation to cell retention within the T cell paracortex of the lymph node. Specific promotion of T SCM cell differentiation with nucleoside-modified mRNA-LNP vaccination elicits enhanced protection against chronic viral challenge.

Targeting a disintegrin and metalloprotease (ADAM) 17-CD122 axis enhances CD8+ T cell effector differentiation and anti-tumor immunity

CD8+ T cell immune responses are regulated by multi-layer networks, while the post-translational regulation remains largely unknown. Transmembrane ectodomain shedding is an important post-translational process orchestrating receptor expression and signal transduction through proteolytic cleavage of membrane proteins. Here, by targeting the sheddase A Disintegrin and Metalloprotease (ADAM)17, we defined a post-translational regulatory mechanism mediated by the ectodomain shedding in CD8+ T cells. Transcriptomic and proteomic analysis revealed the involvement of post-translational regulation in CD8+ T cells. T cell-specific deletion of ADAM17 led to a dramatic increase in effector CD8+ T cell differentiation and enhanced cytolytic effects to eliminate pathogens and tumors. Mechanistically, ADAM17 regulated CD8+ T cells through cleavage of membrane CD122. ADAM17 inhibition led to elevated CD122 expression and enhanced response to IL-2 and IL-15 stimulation in both mouse and human CD8+ T cells. Intriguingly, inhibition of ADAM17 in CD8+ T cells improved the efficacy of chimeric antigen receptor (CAR) T cells in solid tumors. Our findings reveal a critical post-translational regulation in CD8+ T cells, providing a potential therapeutic strategy of targeting ADAM17 for effective anti-tumor immunity.

Osr2 functions as a biomechanical checkpoint to aggravate CD8+ T cell exhaustion in tumor

Alterations in extracellular matrix (ECM) architecture and stiffness represent hallmarks of cancer. Whether the biomechanical property of ECM impacts the functionality of tumor-reactive CD8+ T cells remains largely unknown. Here, we reveal that the transcription factor (TF) Osr2 integrates biomechanical signaling and facilitates the terminal exhaustion of tumor-reactive CD8+ T cells. Osr2 expression is selectively induced in the terminally exhausted tumor-specific CD8+ T cell subset by coupled T cell receptor (TCR) signaling and biomechanical stress mediated by the Piezo1/calcium/CREB axis. Consistently, depletion of Osr2 alleviates the exhaustion of tumor-specific CD8+ T cells or CAR-T cells, whereas forced Osr2 expression aggravates their exhaustion in solid tumor models. Mechanistically, Osr2 recruits HDAC3 to rewire the epigenetic program for suppressing cytotoxic gene expression and promoting CD8+ T cell exhaustion. Thus, our results unravel Osr2 functions as a biomechanical checkpoint to exacerbate CD8+ T cell exhaustion and could be targeted to potentiate cancer immunotherapy.

Translational Frontiers and Clinical Opportunities of Immunologically Fitted Radiotherapy

Ionizing radiation can have a wide range of impacts on tumor-immune interactions, which are being studied with the greatest interest and at an accelerating pace by the medical community. Despite its undeniable immunostimulatory potential, it clearly appears that radiotherapy as it is prescribed and delivered nowadays often alters the host's immunity toward a suboptimal state. This may impair the full recovery of a sustained and efficient antitumor immunosurveillance posttreatment. An emerging concept is arising from this awareness and consists of reconsidering the way of designing radiation treatment planning, notably by taking into account the individualized risks of deleterious radio-induced immune alteration that can be deciphered from the planned beam trajectory through lymphocyte-rich organs. In this review, we critically appraise key aspects to consider while planning immunologically fitted radiotherapy, including the challenges linked to the identification of new dose constraints to immune-rich structures. We also discuss how pharmacologic immunomodulation could be advantageously used in combination with radiotherapy to compensate for the radio-induced loss, for example, with (i) agonists of interleukin (IL)2, IL4, IL7, IL9, IL15, or IL21, similarly to G-CSF being used for the prophylaxis of severe chemo-induced neutropenia, or with (ii) myeloid-derived suppressive cell blockers.

The role of CD4+ T cells in visceral leishmaniasis; new and emerging roles for NKG7 and TGFβ

Visceral leishmaniasis is a potentially devastating neglected tropical disease caused by the protozoan parasites Leishmania donovani and L. infantum (chagasi). These parasites reside in tissue macrophages and survive by deploying a number of mechanisms aimed at subverting the host immune response. CD4+ T cells play an important role in controlling Leishmania parasites by providing help in the form of pro-inflammatory cytokines to activate microbiocidal pathways in infected macrophages. However, because these cytokines can also cause tissue damage if over-produced, regulatory immune responses develop, and the balance between pro-inflammatory and regulatory CD4+ T cells responses determines the outcomes of infection. Past studies have identified important roles for pro-inflammatory cytokines such as IFNγ and TNF, as well as regulatory co-inhibitory receptors and the potent anti-inflammatory cytokine IL-10. More recently, other immunoregulatory molecules have been identified that play important roles in CD4+ T cell responses during VL. In this review, we will discuss recent findings about two of these molecules; the NK cell granule protein Nkg7 and the anti-inflammatory cytokine TGFβ, and describe how they impact CD4+ T cell functions and immune responses during visceral leishmaniasis.

Sex differences in cancer and immunotherapy outcomes: the role of androgen receptor

Across the wide range of clinical conditions, there exists a sex imbalance where biological females are more prone to autoimmune diseases and males to some cancers. These discrepancies are the combinatory consequence of lifestyle and environmental factors such as smoking, alcohol consumption, obesity, and oncogenic viruses, as well as other intrinsic biological traits including sex chromosomes and sex hormones. While the emergence of immuno-oncology (I/O) has revolutionised cancer care, the efficacy across multiple cancers may be limited because of a complex, dynamic interplay between the tumour and its microenvironment (TME). Indeed, sex and gender can also influence the varying effectiveness of I/O. Androgen receptor (AR) plays an important role in tumorigenesis and in shaping the TME. Here, we lay out the epidemiological context of sex disparity in cancer and then review the current literature on how AR signalling contributes to such observation via altered tumour development and immunology. We offer insights into AR-mediated immunosuppressive mechanisms, with the hope of translating preclinical and clinical evidence in gender oncology into improved outcomes in personalised, I/O-based cancer care.

CAR T cells outperform CAR NK cells in CAR-mediated effector functions in head-to-head comparison

BACKGROUND

CAR NK cells as vehicles for engineered "off-the-shelf" cellular cancer immunotherapy have attracted significant interest. Nonetheless, a comprehensive comparative assessment of the anticancer activity of CAR T cells and CAR NK cells carrying approved benchmark anti-CD19 CAR constructs is missing. Here, we report a direct head-to-head comparison of CD19-directed human T and NK cells.

METHODS

We generated CAR T and CAR NK cells derived from healthy donor PBMC by retroviral transduction with the same benchmark second-generation anti-CD19 CAR construct, FMC63.28z. We investigated IFN-γ secretion and direct cytotoxicity in vitro against various CD19+ cancer cell lines as well as in autologous versus allogeneic settings. Furthermore, we have assessed anticancer activity of CAR T and CAR NK cells in vivo using a xenograft lymphoma model in an autologous versus allogeneic setting and a leukemia model.

RESULTS

Our main findings are a drastically reduced capacity for CAR-mediated IFN-γ production and lower CAR-mediated cytotoxicity of CAR NK cells relative to CAR T cells in vitro. Consistent with these in vitro findings, we report superior anticancer activity of autologous CAR T cells compared with allogeneic CAR NK cells in vivo.

CONCLUSIONS

CAR T cells had significantly higher CAR-mediated effector functions than CAR NK cells in vitro against several cancer cell lines and autologous CAR T cells outperformed allogeneic CAR NK cells both in vitro and in vivo. CAR NK cells will likely benefit from further engineering to enhance anticancer activity to ultimately fulfill the promise of an effective off-the-shelf product.

Decreased progenitor TCF1 + T-cells correlate with COVID-19 disease severity

COVID-19, caused by SARS-CoV-2, can lead to a severe inflammatory disease characterized by significant lymphopenia. However, the underlying cause for the depletion of T-cells in COVID-19 patients remains incompletely understood. In this study, we assessed the presence of different T-cell subsets in the progression of COVID-19 from mild to severe disease, with a focus on TCF1 expressing progenitor T-cells that are needed to replenish peripheral T-cells during infection. Our results showed a preferential decline in TCF1+ progenitor CD4 and CD8+ T-cells with disease severity. This decline was seen in various TCF1+ subsets including naive, memory and effector-memory cells, and surprisingly, was accompanied by a loss in cell division as seen by a marked decline in Ki67 expression. In addition, TCF1+ T-cells showed a reduction in pro-survival regulator, BcL2, and the appearance of a new population of TCF1 negative caspase-3 expressing cells in peripheral blood from patients with severe disease. The decline in TCF1+ T-cells was also seen in a subgroup of severe patients with vitamin D deficiency. Lastly, we found that sera from severe patients inhibited TCF1 transcription ex vivo which was attenuated by a blocking antibody against the cytokine, interleukin-12 (IL12). Collectively, our findings underscore the potential significance of TCF1+ progenitor T-cells in accounting for the loss of immunity in severe COVID-19 and outline an array of markers that could be used to identify disease progression.

Comment on "An Injectable Hydrogel to Modulate T Cells for Cancer Immunotherapy"

Recent clinical successes of immune checkpoint blockade (ICB) therapies represents a milestone as a novel anti-tumor strategy beyond surgery, radiotherapy, chemotherapy, and targeted therapy in cancer therapy. T cells, especially CD8+ T cells, play crucial roles in anti-tumor immune responses. However, most T cells in the tumor microenvironment express high inhibitory receptors, such as PD-1, TIM-3, and LAG-3, and decreased T cell response in response to stimuli. Applying ICB therapies, such as anti-PD-1, promotes T cell activation and increases cytotoxic T lymphocyte (CTL) response, leading to the enhanced anti-tumor immune response in patients with malignancy. Therefore, studies aimed to define novel targets that can restrain T cell terminal exhaustion are urgently required to provide new strategies for patients resistant to immunotherapy. The previously published study by Zhang et al. (An Injectable Hydrogel to Modulate T Cells for Cancer Immunotherapy, https://doi.org/10.1002/smll.202202663) introduces a new type of injectable hydrogel that can regulate the function of T cells, thereby improving their effectiveness in cancer immunotherapy. However, it remains to be discussed for its conclusion, as the flow cell assay of this article may not be proper.

TCF1-LEF1 co-expression identifies a multipotent progenitor cell (TH2-MPP) across human allergic diseases

Repetitive exposure to antigen in chronic infection and cancer drives T cell exhaustion, limiting adaptive immunity. In contrast, aberrant, sustained T cell responses can persist over decades in human allergic disease. To understand these divergent outcomes, we employed bioinformatic, immunophenotyping and functional approaches with human diseased tissues, identifying an abundant population of type 2 helper T (TH2) cells with co-expression of TCF7 and LEF1, and features of chronic activation. These cells, which we termed TH2-multipotent progenitors (TH2-MPP) could self-renew and differentiate into cytokine-producing effector cells, regulatory T (Treg) cells and follicular helper T (TFH) cells. Single-cell T-cell-receptor lineage tracing confirmed lineage relationships between TH2-MPP, TH2 effectors, Treg cells and TFH cells. TH2-MPP persisted despite in vivo IL-4 receptor blockade, while thymic stromal lymphopoietin (TSLP) drove selective expansion of progenitor cells and rendered them insensitive to glucocorticoid-induced apoptosis in vitro. Together, our data identify TH2-MPP as an aberrant T cell population with the potential to sustain type 2 inflammation and support the paradigm that chronic T cell responses can be coordinated over time by progenitor cells.

A dietary commensal microbe enhances antitumor immunity by activating tumor macrophages to sequester iron

Innate immune cells generate a multifaceted antitumor immune response, including the conservation of essential nutrients such as iron. These cells can be modulated by commensal bacteria; however, identifying and understanding how this occurs is a challenge. Here we show that the food commensal Lactiplantibacillus plantarum IMB19 augments antitumor immunity in syngeneic and xenograft mouse tumor models. Its capsular heteropolysaccharide is the major effector molecule, functioning as a ligand for TLR2. In a two-pronged manner, it skews tumor-associated macrophages to a classically active phenotype, leading to generation of a sustained CD8+ T cell response, and triggers macrophage 'nutritional immunity' to deploy the high-affinity iron transporter lipocalin-2 for capturing and sequestering iron in the tumor microenvironment. This process induces a cycle of tumor cell death, epitope expansion and subsequent tumor clearance. Together these data indicate that food commensals might be identified and developed into 'oncobiotics' for a multi-layered approach to cancer therapy.

Microbial metabolite enhances immunotherapy efficacy by modulating T cell stemness in pan-cancer

The immune checkpoint blockade (ICB) response in human cancers is closely linked to the gut microbiota. Here, we report that the abundance of commensal Lactobacillus johnsonii is positively correlated with the responsiveness of ICB. Supplementation with Lactobacillus johnsonii or tryptophan-derived metabolite indole-3-propionic acid (IPA) enhances the efficacy of CD8+ T cell-mediated αPD-1 immunotherapy. Mechanistically, Lactobacillus johnsonii collaborates with Clostridium sporogenes to produce IPA. IPA modulates the stemness program of CD8+ T cells and facilitates the generation of progenitor exhausted CD8+ T cells (Tpex) by increasing H3K27 acetylation at the super-enhancer region of Tcf7. IPA improves ICB responsiveness at the pan-cancer level, including melanoma, breast cancer, and colorectal cancer. Collectively, our findings identify a microbial metabolite-immune regulatory pathway and suggest a potential microbial-based adjuvant approach to improve the responsiveness of immunotherapy.

NR4a1/2 deletion promotes accumulation of TCF1+ stem-like precursors of exhausted CD8+ T cells in the tumor microenvironment

T cell exhaustion impairs tumor immunity and contributes to resistance against immune checkpoint inhibitors. The nuclear receptor subfamily 4 group A (NR4a) family of nuclear receptors plays a crucial role in driving T cell exhaustion. In this study, we observe that NR4a1 and NR4a2 deficiency in CD8+ tumor-infiltrating lymphocytes (TILs) results in potent tumor eradication and exhibits not only reduced exhaustion characteristics but also an increase in the precursors/progenitors of exhausted T (Pre-Tex) cell fraction. Serial transfers of NR4a1-/-NR4a2-/-CD8+ TILs into tumor-bearing mice result in the expansion of TCF1+ (Tcf7+) stem-like Pre-Tex cells, whereas wild-type TILs are depleted upon secondary transfer. NR4a1/2-deficient CD8+ T cells express higher levels of stemness/memory-related genes and illustrate potent mitochondrial oxidative phosphorylation. Collectively, these findings suggest that inhibiting NR4a in tumors represents a potent immuno-oncotherapy strategy by increasing stem-like Pre-Tex cells and reducing exhaustion of CD8+ T cells.

CD38-RyR2 axis-mediated signaling impedes CD8+ T cell response to anti-PD1 therapy in cancer

PD1 blockade therapy, harnessing the cytotoxic potential of CD8+ T cells, has yielded clinical success in treating malignancies. However, its efficacy is often limited due to the progressive differentiation of intratumoral CD8+ T cells into a hypofunctional state known as terminal exhaustion. Despite identifying CD8+ T cell subsets associated with immunotherapy resistance, the molecular pathway triggering the resistance remains elusive. Given the clear association of CD38 with CD8+ T cell subsets resistant to anti-PD1 therapy, we investigated its role in inducing resistance. Phenotypic and functional characterization, along with single-cell RNA sequencing analysis of both in vitro chronically stimulated and intratumoral CD8+ T cells, revealed that CD38-expressing CD8+ T cells are terminally exhausted. Exploring the molecular mechanism, we found that CD38 expression was crucial in promoting terminal differentiation of CD8+ T cells by suppressing TCF1 expression, thereby rendering them unresponsive to anti-PD1 therapy. Genetic ablation of CD38 in tumor-reactive CD8+ T cells restored TCF1 levels and improved the responsiveness to anti-PD1 therapy in mice. Mechanistically, CD38 expression on exhausted CD8+ T cells elevated intracellular Ca2+ levels through RyR2 calcium channel activation. This, in turn, promoted chronic AKT activation, leading to TCF1 loss. Knockdown of RyR2 or inhibition of AKT in CD8+ T cells maintained TCF1 levels, induced a sustained anti-tumor response, and enhanced responsiveness to anti-PD1 therapy. Thus, targeting CD38 represents a potential strategy to improve the efficacy of anti-PD1 treatment in cancer.

Precursor exhausted CD8+T cells in colorectal cancer tissues associated with patient's survival and immunotherapy responsiveness

Exhausted CD8+T cells represent a distinct cellular lineage that emerges during both chronic infections and cancers. Recent studies have shown that persistent antigen exposure can drive the differentiation of precursor exhausted CD8+T cells, termed Tpex cells, which are characterized as TCF-1+PD-1+CD8+T cells. Elevated Tpex cell frequencies in the tumor microenvironment (TME) are associated with improved overall survival (OS) in cancer patients and heightened responsiveness to anti-PD-1 therapy. In our present study, we utilized multi-color immunohistochemistry (mIHC) to determine the localization and clinical implications of tumor-infiltrating Tpex cells within the TME of human colorectal cancer (CRC) tissues. We also conducted a multi-omics integrative analysis using single-cell RNA sequencing (scRNA-seq) data derived from both the murine MC38 tumor model and human CRC tissues. This analysis helped delineate the transcriptional and functional attributes of Tpex cells within the CRC TME. Furthermore, we employed spatial transcriptome sequencing data from CRC patients to investigate the interactions between Tpex cells and other immune cell subsets within the TME. In conclusion, our study not only established a method for Tpex cell detection using mIHC technology but also confirmed that assessing Tpex cells within the CRC TME could be indicative of patients' survival. We further uncovered the transcriptional and functional characteristics of Tpex cells in the TME and ascertained their pivotal role in the efficacy of immunotherapy against CRC.

Cell-intrinsic PD-L1 ablation sustains effector CD8+ T cell responses and promotes antitumor T cell therapy

Adoptive cell therapies are emerging forms of immunotherapy that reprogram T cells for enhanced antitumor responses. Although surface programmed cell death-ligand 1 (PD-L1)/programmed cell death protein 1 (PD-1) engagement inhibits antitumor immunity, the role of cell-intrinsic PD-L1 in adoptive T cell therapy remains unknown. Here, we found that intracellular PD-L1 was enriched in tumor-infiltrating CD8+ T cells of cancer patients. PD-L1 ablation promoted antitumor immune responses and the maintenance of an effector-like state of therapeutic CD8+ T cells, while blockade of surface PD-L1 was unable to impact on their expansion and function. Moreover, cell-intrinsic PD-L1 impeded CD8+ T cell activity, which partially relied on mTORC1 signaling. Furthermore, endogenous tumor-reactive CD8+ T cells were motivated by BATF3-driven dendritic cells after adoptive transfer of PD-L1-deficient therapeutic CD8+ T cells. This role of cell-intrinsic PD-L1 in therapeutic CD8+ T cell dysfunction highlights that disrupting cell-intrinsic PD-L1 in CD8+ T cells represents a viable approach to improving T cell-based cancer immunotherapy.

Signaling via a CD27-TRAF2-SHP-1 axis during naive T cell activation promotes memory-associated gene regulatory networks

The interaction of the tumor necrosis factor receptor (TNFR) family member CD27 on naive CD8+ T (Tn) cells with homotrimeric CD70 on antigen-presenting cells (APCs) is necessary for T cell memory fate determination. Here, we examined CD27 signaling during Tn cell activation and differentiation. In conjunction with T cell receptor (TCR) stimulation, ligation of CD27 by a synthetic trimeric CD70 ligand triggered CD27 internalization and degradation, suggesting active regulation of this signaling axis. Internalized CD27 recruited the signaling adaptor TRAF2 and the phosphatase SHP-1, thereby modulating TCR and CD28 signals. CD27-mediated modulation of TCR signals promoted transcription factor circuits that induced memory rather than effector associated gene programs, which are induced by CD28 costimulation. CD27-costimulated chimeric antigen receptor (CAR)-engineered T cells exhibited improved tumor control compared with CD28-costimulated CAR-T cells. Thus, CD27 signaling during Tn cell activation promotes memory properties with relevance to T cell immunotherapy.

Reversible, tunable epigenetic silencing of TCF1 generates flexibility in the T cell memory decision

The immune system encodes information about the severity of a pathogenic threat in the quantity and type of memory cells it forms. This encoding emerges from lymphocyte decisions to maintain or lose self-renewal and memory potential during a challenge. By tracking CD8+ T cells at the single-cell and clonal lineage level using time-resolved transcriptomics, quantitative live imaging, and an acute infection model, we find that T cells will maintain or lose memory potential early after antigen recognition. However, following pathogen clearance, T cells may regain memory potential if initially lost. Mechanistically, this flexibility is implemented by a stochastic cis-epigenetic switch that tunably and reversibly silences the memory regulator, TCF1, in response to stimulation. Mathematical modeling shows how this flexibility allows memory T cell numbers to scale robustly with pathogen virulence and immune response magnitudes. We propose that flexibility and stochasticity in cellular decisions ensure optimal immune responses against diverse threats.

Distinct profiles of proliferating CD8+/TCF1+ T cells and CD163+/PD-L1+ macrophages predict risk of relapse differently among treatment-naïve breast cancer subtypes

Immunophenotypic analysis of breast cancer microenvironment is gaining attraction as a clinical tool improving breast cancer patient stratification. The aim of this study is to evaluate proliferating CD8 + including CD8 + TCF1 + Τ cells along with PD-L1 expressing tissue-associated macrophages among different breast cancer subtypes. A well-characterized cohort of 791 treatment-naïve breast cancer patients was included. The analysis demonstrated a distinct expression pattern among breast cancer subtypes characterized by increased CD8 + , CD163 + and CD163 + PD-L1 + cells along with high PD-L1 status and decreased fraction of CD8 + Ki67 + T cells in triple negative (TNBC) and HER2 + compared to luminal tumors. Kaplan-Meier and Cox univariate survival analysis revealed that breast cancer patients with high CD8 + , CD8 + Ki67 + , CD8 + TCF1 + cells, PD-L1 score and CD163 + PD-L1 + cells are likely to have a prolonged relapse free survival, while patients with high CD163 + cells have a worse prognosis. A differential impact of high CD8 + , CD8 + Ki67 + , CD8 + TCF1 + T cells, CD163 + PD-L1 + macrophages and PD-L1 status on prognosis was identified among the various breast cancer subtypes since only TNBC patients experience an improved prognosis compared to patients with luminal A tumors. Conversely, high infiltration by CD163 + cells is associated with worse prognosis only in patients with luminal A but not in TNBC tumors. Multivariate Cox regression analysis in TNBC patients revealed that increased CD8 + [hazard ratio (HR) = 0.542; 95% confidence interval (CI) 0.309-0.950; p = 0.032), CD8 + TCF1 + (HR = 0.280; 95% CI 0.101-0.779; p = 0.015), CD163 + PD-L1 + (HR: 0.312; 95% CI 0.112-0.870; p = 0.026) cells along with PD-L1 status employing two different scoring methods (HR: 0.362; 95% CI 0.162-0.812; p = 0.014 and HR: 0.395; 95% CI 0.176-0.884; p = 0.024) were independently linked with a lower relapse rate. Multivariate analysis in Luminal type A patients revealed that increased CD163 + was independently associated with a higher relapse rate (HR = 2.360; 95% CI 1.077-5.170; p = 0.032). This study demonstrates that the evaluation of the functional status of CD8 + T cells in combination with the analysis of immunosuppressive elements could provide clinically relevant information in different breast cancer subtypes.

PD-1 or CTLA-4 blockade promotes CD86-driven Treg responses upon radiotherapy of lymphocyte-depleted cancer in mice

Radiotherapy (RT) is considered immunogenic, but clinical data demonstrating RT-induced T cell priming are scarce. Here, we show in a mouse tumor model representative of human lymphocyte-depleted cancer that RT enhanced spontaneous priming of thymus-derived (FOXP3+Helios+) Tregs by the tumor. These Tregs acquired an effector phenotype, populated the tumor, and impeded tumor control by a simultaneous, RT-induced CD8+ cytotoxic T cell (CTL) response. Combination of RT with CTLA-4 or PD-1 blockade, which enables CD28 costimulation, further increased this Treg response and failed to improve tumor control. We discovered that upon RT, the CD28 ligands CD86 and CD80 differentially affected the Treg response. CD86, but not CD80, blockade prevented the effector Treg response, enriched the tumor-draining lymph node migratory conventional DCs that were positive for PD-L1 and CD80 (PD-L1+CD80+), and promoted CTL priming. Blockade of CD86 alone or in combination with PD-1 enhanced intratumoral CTL accumulation, and the combination significantly increased RT-induced tumor regression and OS. We advise that combining RT with PD-1 and/or CTLA-4 blockade may be counterproductive in lymphocyte-depleted cancers, since these interventions drive Treg responses in this context. However, combining RT with CD86 blockade may promote the control of such tumors by enabling a CTL response.

The interaction between DNA methylation and tumor immune microenvironment: from the laboratory to clinical applications

DNA methylation is a pivotal epigenetic modification that affects gene expression. Tumor immune microenvironment (TIME) comprises diverse immune cells and stromal components, creating a complex landscape that can either promote or inhibit tumor progression. In the TIME, DNA methylation has been shown to play a critical role in influencing immune cell function and tumor immune evasion. DNA methylation regulates immune cell differentiation, immune responses, and TIME composition Targeting DNA methylation in TIME offers various potential avenues for enhancing immune cytotoxicity and reducing immunosuppression. Recent studies have demonstrated that modification of DNA methylation patterns can promote immune cell infiltration and function. However, challenges persist in understanding the precise mechanisms underlying DNA methylation in the TIME, developing selective epigenetic therapies, and effectively integrating these therapies with other antitumor strategies. In conclusion, DNA methylation of both tumor cells and immune cells interacts with the TIME, and thus affects clinical efficacy. The regulation of DNA methylation within the TIME holds significant promise for the advancement of tumor immunotherapy. Addressing these challenges is crucial for harnessing the full potential of epigenetic interventions to enhance antitumor immune responses and improve patient outcomes.

The dynamic shifts of IL-10-producing Th17 and IL-17-producing Treg in health and disease: a crosstalk between ancient "Yin-Yang" theory and modern immunology

The changes in T regulatory cell (Treg) and T helper cell (Th) 17 ratios holds paramount importance in ensuring internal homeostasis and disease progression. Recently, novel subsets of Treg and Th17, namely IL-17-producing Treg and IL-10-producing Th17 have been identified. IL-17-producing Treg and IL-10-producing Th17 are widely considered as the intermediates during Treg/Th17 transformation. These "bi-functional" cells exhibit plasticity and have been demonstrated with important roles in multiple physiological functions and disease processes. Yin and Yang represent opposing aspects of phenomena according to the ancient Chinese philosophy "Yin-Yang" theory. Furthermore, Yin can transform into Yang, and vice versa, under specific conditions. This theory has been widely used to describe the contrasting functions of immune cells and molecules. Therefore, immune-activating populations (Th17, M1 macrophage, etc.) and immune overreaction (inflammation, autoimmunity) can be considered Yang, while immunosuppressive populations (Treg, M2 macrophage, etc.) and immunosuppression (tumor, immunodeficiency) can be considered Yin. However, another important connotation of "Yin-Yang" theory, the conversion between Yin and Yang, has been rarely documented in immune studies. The discovery of IL-17-producing Treg and IL-10-producing Th17 enriches the meaning of "Yin-Yang" theory and further promotes the relationship between ancient "Yin-Yang" theory and modern immunology. Besides, illustrating the functions of IL-17-producing Treg and IL-10-producing Th17 and mechanisms governing their differentiation provides valuable insights into the mechanisms underlying the dynamically changing statement of immune statement in health and diseases.

The transcriptional cofactor Tle3 reciprocally controls effector and central memory CD8+ T cell fates

Antigen-experienced CD8+ T cells form effector and central memory T cells (TEM and TCM cells, respectively); however, the mechanism(s) controlling their lineage plasticity remains incompletely understood. Here we show that the transcription cofactor Tle3 critically regulates TEM and TCM cell fates and lineage stability through dynamic redistribution in antigen-responding CD8+ T cell genome. Genetic ablation of Tle3 promoted CD8+ TCM cell formation at the expense of CD8+ TEM cells. Lineage tracing showed that Tle3-deficient CD8+ TEM cells underwent accelerated conversion into CD8+ TCM cells while retaining robust recall capacity. Tle3 acted as a coactivator for Tbet to increase chromatin opening at CD8+ TEM cell-characteristic sites and to activate CD8+ TEM cell signature gene transcription, while engaging Runx3 and Tcf1 to limit CD8+ TCM cell-characteristic molecular features. Thus, Tle3 integrated functions of multiple transcription factors to guard lineage fidelity of CD8+ TEM cells, and manipulation of Tle3 activity could favor CD8+ TCM cell production.

Neoadjuvant atezolizumab plus chemotherapy in gastric and gastroesophageal junction adenocarcinoma: the phase 2 PANDA trial

Gastric and gastroesophageal junction (G/GEJ) cancers carry a poor prognosis, and despite recent advancements, most patients die of their disease. Although immune checkpoint blockade became part of the standard-of-care for patients with metastatic G/GEJ cancers, its efficacy and impact on the tumor microenvironment (TME) in early disease remain largely unknown. We hypothesized higher efficacy of neoadjuvant immunotherapy plus chemotherapy in patients with nonmetastatic G/GEJ cancer. In the phase 2 PANDA trial, patients with previously untreated resectable G/GEJ tumors (n = 21) received neoadjuvant treatment with one cycle of atezolizumab monotherapy followed by four cycles of atezolizumab plus docetaxel, oxaliplatin and capecitabine. Treatment was well tolerated. There were grade 3 immune-related adverse events in two of 20 patients (10%) but no grade 4 or 5 immune-related adverse events, and all patients underwent resection without treatment-related delays, meeting the primary endpoint of safety and feasibility. Tissue was obtained at multiple time points, allowing analysis of the effects of single-agent anti-programmed cell death ligand 1 (PD-L1) and the subsequent combination with chemotherapy on the TME. Twenty of 21 patients underwent surgery and were evaluable for secondary pathologic response and survival endpoints, and 19 were evaluable for exploratory translational analyses. A major pathologic response (≤10% residual viable tumor) was observed in 14 of 20 (70%, 95% confidence interval 46-88%) patients, including 9 (45%, 95% confidence interval 23-68%) pathologic complete responses. At a median follow-up of 47 months, 13 of 14 responders were alive and disease-free, and five of six nonresponders had died as a result of recurrence. Notably, baseline anti-programmed cell death protein 1 (PD-1)+CD8+ T cell infiltration was significantly higher in responders versus nonresponders, and comparison of TME alterations following anti-PD-L1 monotherapy versus the subsequent combination with chemotherapy showed an increased immune activation on single-agent PD-1/L1 axis blockade. On the basis of these data, monotherapy anti-PD-L1 before its combination with chemotherapy warrants further exploration and validation in a larger cohort of patients with nonmetastatic G/GEJ cancer. ClinicalTrials.gov registration: NCT03448835 .

LRP11 promotes stem-like T cells via MAPK13-mediated TCF1 phosphorylation, enhancing anti-PD1 immunotherapy

BACKGROUND

Tumor-infiltrating T cells enter an exhausted or dysfunctional state, which limits antitumor immunity. Among exhausted T cells, a subset of cells with features of progenitor or stem-like cells has been identified as TCF1+ CD8+ T cells that respond to immunotherapy. In contrast to the finding that TCF1 controls epigenetic and transcriptional reprogramming in tumor-infiltrating stem-like T cells, little is known about the regulation of TCF1. Emerging data show that elevated body mass index is associated with outcomes of immunotherapy. However, the mechanism has not been clarified.

METHODS

We investigated the proliferation of splenic lymphocytes or CD8+ T cells induced by CD3/CD28 stimulation in vitro. We evaluated the effects of low-density lipoprotein (LDL) and LRP11 inhibitors, as well as MAPK13 inhibitors. Additionally, we used shRNA technology to validate the roles of LRP11 and MAPK13. In an in vivo setting, we employed male C57BL/6J injected with B16 cells or MC38 cells to build a tumor model to assess the effects of LDL and LRP11 inhibitors, LRP11 activators, MAPK13 inhibitors on tumor growth. Flow cytometry was used to measure cell proportions and activation status. Molecular interactions and TCF1 status were examined using Western blotting. Moreover, we employed RNA sequencing to investigate the effects of LDL stimulation and MAPK13 inhibition in CD8+ T cells.

RESULTS

By using a tumor-bearing mouse model, we found that LDL-induced tumor-infiltrating TCF1+PD1+CD8+ T cells. Using a cell-based chimeric receptor screening system, we showed that LRP11 interacted with LDL and activated TCF1. LRP11 activation enhanced TCF1+PD1+CD8+ T-cell-mediated antitumor immunity, consistent with LRP11 blocking impaired T-cell function. Mechanistically, LRP11 activation induces MAPK13 activation. Then, MAPK13 phosphorylates TCF1, leading to increase of stem-like T cells.

CONCLUSIONS

LRP11-MAPK13-TCF1 enhanced antitumor immunity and induced tumor-infiltrating stem-like T cells.

Disruption of SUV39H1-Mediated H3K9 Methylation Sustains CAR T-cell Function

Suboptimal functional persistence limits the efficacy of adoptive T-cell therapies. CD28-based chimeric antigen receptors (CAR) impart potent effector function to T cells but with a limited lifespan. We show here that the genetic disruption of SUV39H1, which encodes a histone-3, lysine-9 methyl-transferase, enhances the early expansion, long-term persistence, and overall antitumor efficacy of human CAR T cells in leukemia and prostate cancer models. Persisting SUV39H1-edited CAR T cells demonstrate improved expansion and tumor rejection upon multiple rechallenges. Transcriptional and genome accessibility profiling of repeatedly challenged CAR T cells shows improved expression and accessibility of memory transcription factors in SUV39H1-edited CAR T cells. SUV39H1 editing also reduces expression of inhibitory receptors and limits exhaustion in CAR T cells that have undergone multiple rechallenges. Our findings thus demonstrate the potential of epigenetic programming of CAR T cells to balance their function and persistence for improved adoptive cell therapies.

SIGNIFICANCE

T cells engineered with CD28-based CARs possess robust effector function and antigen sensitivity but are hampered by limited persistence, which may result in tumor relapse. We report an epigenetic strategy involving disruption of the SUV39H1-mediated histone-silencing program that promotes the functional persistence of CD28-based CAR T cells. See related article by López-Cobo et al., p. 120. This article is featured in Selected Articles from This Issue, p. 5.

Dysfunctional states of unconventional T-cell subsets in cancer

Unconventional T cells represent a promising therapeutic agent to overcome the current limitations of immunotherapies due to their universal T-cell receptors, ability to respond directly to cytokine stimulation, and capacity to recruit and modulate conventional immune cells in the tumor microenvironment. Like conventional T cells, unconventional T cells can enter a dysfunctional state, and the functional differences associated with this state may provide insight into the discrepancies observed in their role in antitumor immunity in various cancers. The exhaustive signature of unconventional T cells differs from conventional αβ T cells, and understanding the differences in the mechanisms underlying exhaustive differentiation in these cell types may aid in the discovery of new treatments to improve sustained antitumor responses. Ongoing clinical trials investigating therapies that leverage unconventional T-cell populations have shown success in treating hematologic malignancies and reducing the immunosuppressive tumor environment. However, several hurdles remain to extend these promising results into solid tumors. Here we discuss the current knowledge on unconventional T-cell function/dysfunction and consider how the incorporation of therapies that modulate unconventional T-cell exhaustion may aid in overcoming the current limitations of immunotherapy. Additionally, we discuss how components of the tumor microenvironment alter the functions of unconventional T cells and how these changes can affect tumor infiltration by lymphocytes and alter conventional T-cell responses.

SLC7A2-Mediated Lysine Catabolism Inhibits Immunosuppression in Triple Negative Breast Cancer

Breast cancer is one of the most common malignant tumors worldwide. SLC7A2 is abnormally expressed in multiple cancers. However, its potential in triple negative breast cancer (TNBC) is still unclear. The purpose of this study was to investigate the roles of SLC7A2 and its underlying molecular mechanisms in TNBC. mRNA expression was detected by RT-qPCR. Protein expression was detected by western blot. Co-localization of ACOX1 and TCF1 was determined using FISH assay. Histone crotonylation was performed using in vitro histone crotonylation assay. Functional analysis was performed using CCK-8 and flow cytometry assays. Xenograft assay was conducted to further verify the role of SLC7A2 in TNBC. CD8A expression was detected using immunohistochemistry. We found that SLC7A2 is downregulated in TNBC tumors. Low levels are associated with advanced stages and lymph node metastasis. SLC7A2 expression is positively correlated with CD8A. SLC7A2-mediated lysine catabolism drives the activation of CD8+ T cells. Moreover, SLC7A2 promotes histone crotonylation via upregulating ACOX1. It also promotes interaction between ACOX1 and TCF1, thus promoting antitumor T cell immunity. Additionally, overexpression of SLC7A2 activates CD8+ T cells and enhances the chemosensitivity of anti-PD-1 therapies in vivo. In conclusion, SLC7A2 may function as an antitumor gene in TNBC by activating antitumor immunity, suggesting SLC7A2/ACOX1/TCF1 signaling as a promising therapeutic strategy.

Regulation of the WNT-CTNNB1 signaling pathway by severe fever with thrombocytopenia syndrome virus in a cap-snatching manner

IMPORTANCE

One of the conserved mechanisms at the stage of genome transcription of segmented negative-strand RNA viruses (sNSVs) is the cap-snatching process, which is vital for sNSVs transcription and provides drugable targets for the development of antivirals. However, the specificity of RNAs snatched by sNSV is still unclear. By transcriptomics analysis of whole blood samples from SFTS patients, we found WNT-CTNNB1 signaling pathway was regulated according to the course of the disease. We then demonstrated that L protein of severe fever with thrombocytopenia syndrome virus (SFTSV) could interact with mRNAs of WNT-CTNNB1 signaling pathway-related gene, thus affecting WNT-CTNNB1 signaling pathway through its cap-snatching activity. Activation of WNT-CTNNB1 signaling pathway enhanced SFTSV replication, while inhibition of this pathway decreased SFTSV replication in vitro and in vivo. These findings suggest that WNT-associated genes may be the substrate for SFTSV "cap-snatching", and indicate a conserved sNSVs replication mechanism involving WNT-CTNNB1 signaling.

Immune Checkpoint Inhibitors in pMMR/MSS Colorectal Cancer

BACKGROUND

Immune checkpoint inhibitors have recently replaced over chemotherapy as the first-line treatment for microsatellite instability-high or mismatch repair deficient (dMMR/MSI-H) stage 4 colorectal cancers. Considering this success, many studies have tried to replicate the use of immune checkpoint inhibitors, either as a single agent or in combination with other therapeutic agents, in the treatment of proficient mismatch repair (pMMR/MSS) stage 4 colorectal cancers. This review summarizes the seminal clinical data about the immune checkpoint inhibitors used in pMMR/MSS colorectal cancers and some future directions.

RESULTS

Studies concerning the use of immune checkpoint inhibitors as a single agent or in combination with other immune checkpoint inhibitors, targeted therapy, chemotherapy, or radiotherapy have proven inefficient in the treatment of pMMR/MSS colorectal cancer. However, a small subset of patients with pMMR/MSS colorectal cancer who has a mutation in POLE and POLD1 enzymes may respond to immunotherapy. Moreover, patients without liver metastasis appear to have a better chance of response. New immune checkpoint targets are being identified, such as VISTA, TIGIT, LAG3, STING signal pathway, and BTLA, and studies are ongoing to determine their efficiency in this disease type.

CONCLUSION

Immune checkpoint inhibitor-based regimens have not yet shown any meaningful positive outcomes for most pMMR/MSS colorectal cancers. A beneficial effect among a minority of these patients has been observed, but concrete biomarkers of response are lacking. Understanding the underlying mechanisms of immune resistance should guide further research for overcoming these obstacles.

Identification of Cellular Interactions in the Tumor Immune Microenvironment Underlying CD8 T Cell Exhaustion

While immune checkpoint inhibitors show success in treating a subset of patients with certain late-stage cancers, these treatments fail in many other patients as a result of mechanisms that have yet to be fully characterized. The process of CD8 T cell exhaustion, by which T cells become dysfunctional in response to prolonged antigen exposure, has been implicated in immunotherapy resistance. Single-cell RNA sequencing (scRNA-seq) produces an abundance of data to analyze this process; however, due to the complexity of the process, contributions of other cell types to a process within a single cell type cannot be simply inferred. We constructed an analysis framework to first rank human skin tumor samples by degree of exhaustion in tumor-infiltrating CD8 T cells and then identify immune cell type-specific gene-regulatory network patterns significantly associated with T cell exhaustion. Using this framework, we further analyzed scRNA-seq data from human tumor and chronic viral infection samples to compare the T cell exhaustion process between these two contexts. In doing so, we identified transcription factor activity in the macrophages of both tissue types associated with this process. Our framework can be applied beyond the tumor immune microenvironment to any system involving cell-cell communication, facilitating insights into key biological processes that underpin the effective treatment of cancer and other complicated diseases.

TCF7 and LEF-1 downregulation in sepsis promotes immune suppression by inhibiting CD4+ T cell proliferation

BACKGROUND

Previous studies have shown that sepsis is implicated in a reduction in the number and function of CD4+ T cells. TCF7 and LEF-1 facilitate early T cell development and lineage selection of CD4+ T cells. However, the function and mechanism of TCF7 and LEF-1 in sepsis are uncharacterized. This study intended to delineate effect of TCF7 and LEF-1 on sepsis and the impact on proliferation of CD4+ T cells in sepsis.

METHODS

A mouse sepsis model was constructed by cecal ligation and puncture (CLP) method. Expression of TCF7 and LEF-1 in sepsis was investigated using bioinformatics analysis and molecular experiments. We then constructed TCF7 and LEF-1 overexpression cell lines to investigate their effects on proliferation, apoptosis, effector activation, and immunosuppressive molecules of CD4+ T cells in sepsis.

RESULTS

TCF7 and LEF-1 were downregulated in sepsis. As the duration of sepsis induction increased, the levels of TCF7 and LEF-1 gradually decreased, as did the number of CD4+ T cells. Cell experiments showed that overexpression of TCF7 and LEF-1 enhanced proliferation and effector activation of CD4+ T cells, reduced apoptosis, decreased PD-1 and LAG3 expression, and promoted immune response in sepsis.

CONCLUSION

In conclusion, this study confirmed that downregulation of TCF7 and LEF-1 expression in sepsis inhibited proliferation of CD4+ T cells, leading to immune suppression. This finding suggested that TCF7 and LEF-1 were potential biological targets for sepsis and indicated that immunotherapy aimed at improving CD4+ T cell proliferation may be a new strategy for immune therapy in sepsis patients.

Peritumoral Immune-suppressive Mechanisms Impede Intratumoral Lymphocyte Infiltration into Colorectal Cancer Liver versus Lung Metastases

Patients with microsatellite stable (MSS) colorectal cancer with liver metastases are resistant to immune checkpoint inhibitor (ICI) therapy, while about one-third of patients with colorectal cancer without liver metastases, particularly those with lung-only metastases, respond to ICI. We analyzed primary colorectal cancer tumors and major metastatic sites (liver, lung, peritoneal) using multiplex immunofluorescence and whole-slide spatial analyses to identify variations in immune contexture and regional localization within the tumor microenvironment. While levels of T and B cells within peritumoral regions were similar, their levels were significantly lower within the tumor core of liver and peritoneal metastases compared with lung metastases. In contrast, antigen-presenting cells (APC) and APC-T cell interactions were more abundant in all regions of lung metastases. We also identified an abundance of lymphoid aggregates throughout lung metastases, but these were present only within peritumoral regions of liver and peritoneal metastases. Larger lymphoid aggregates consistent with features of tertiary lymphoid structures were observed within or adjacent to primary tumors, but not metastatic lesions. Our findings were validated using NanoString GeoMx DSP, which further showed that liver metastases had higher expression of immune-suppressive markers, while lung metastases showed higher proinflammatory activity and T-cell activation markers. Peritoneal metastases demonstrated higher expression of cancer-associated fibroblast-related proteins and upregulated PD-1/PD-L1 signaling molecules. Our results demonstrate that functional status and spatial distribution of immune cells vary significantly across different metastatic sites. These findings suggest that metastatic site-dependent immune contexture may underlie discordant responses to ICI therapy in patients with MSS colorectal cancer.

SIGNIFICANCE

Our results demonstrate that functional status and spatial distribution of immune cells vary significantly across different metastatic sites in MSS colorectal cancer. These findings suggest that metastatic site-dependent immune contexture may underlie discordant responses to ICI therapy in patients with MSS colorectal cancer.

Full eradication of pre-clinical human papilloma virus-induced tumors by a lentiviral vaccine

Human papillomavirus (HPV) infections are the cause of all cervical and numerous oropharyngeal and anogenital cancers. The currently available HPV vaccines, which induce neutralizing antibodies, have no therapeutic effect on established tumors. Here, we developed an immuno-oncotherapy against HPV-induced tumors based on a non-integrative lentiviral vector encoding detoxified forms of the Early E6 and E7 oncoproteins of HPV16 and 18 genotypes, namely, "Lenti-HPV-07". A single intramuscular injection of Lenti-HPV-07 into mice bearing established HPV-induced tumors resulted in complete tumor eradication in 100% of the animals and was also effective against lung metastases. This effect correlated with CD8+ T-cell induction and profound remodeling of the tumor microenvironment. In the intra-tumoral infiltrates of vaccinated mice, the presence of large amounts of activated effector, resident memory, and transcription factor T cell factor-1 (TCF-1)+ "stem-like" CD8+ T cells was associated with full tumor eradication. The Lenti-HPV-07-induced immunity was long-lasting and prevented tumor growth after a late re-challenge, mimicking tumor relapse. Lenti-HPV-07 therapy synergizes with an anti-checkpoint inhibitory treatment and therefore shows promise as an immuno-oncotherapy against established HPV-mediated malignancies.

An oncolytic virus-delivered TGFβ inhibitor overcomes the immunosuppressive tumor microenvironment

While checkpoint blockade immunotherapies have widespread success, they rely on a responsive immune infiltrate; as such, treatments enhancing immune infiltration and preventing immunosuppression are of critical need. We previously generated αPD-1 resistant variants of the murine HNSCC model MEER. While entirely αPD-1 resistant, these tumors regress after single dose of oncolytic vaccinia virus (VV). We then generated a VV-resistant MEER line to dissect the immunologic features of sensitive and resistant tumors. While treatment of both tumor types induced immune infiltration and IFNγ, we found a defining feature of resistance was elevation of immunosuppressive cytokines like TGFβ, which blunted IFNγ signaling, especially in regulatory T cells. We engineered VV to express a genetically encoded TGFβRII inhibitor. Inhibitor-expressing VV produced regressions in resistant tumor models and showed impressive synergy with checkpoint blockade. Importantly, tumor-specific, viral delivery of TGFβ inhibition had no toxicities associated with systemic TGFβ/TGFβR inhibition. Our data suggest that aside from stimulating immune infiltration, oncolytic viruses are attractive means to deliver agents to limit immunosuppression in cancer.

Single-cell dissection of tumor microenvironmental response and resistance to cancer therapy

Cancer treatment strategies have evolved significantly over the years, with chemotherapy, targeted therapy, and immunotherapy as major pillars. Each modality leads to unique treatment outcomes by interacting with the tumor microenvironment (TME), which imposes a fundamental selective pressure on cancer progression. The advent of single-cell profiling technologies has revolutionized our understanding of the intricate and heterogeneous nature of the TME at an unprecedented resolution. This review delves into the commonalities and differential manifestations of how cancer therapies reshape the microenvironment in diverse cancer types. We highlight how groundbreaking immune checkpoint blockade (ICB) strategies alone or in combination with tumor-targeting treatments are endowed with comprehensive mechanistic insights when decoded at the single-cell level, aiming to drive forward future research directions on personalized treatments.

Intrinsically disordered domain of transcription factor TCF-1 is required for T cell developmental fidelity

In development, pioneer transcription factors access silent chromatin to reveal lineage-specific gene programs. The structured DNA-binding domains of pioneer factors have been well characterized, but whether and how intrinsically disordered regions affect chromatin and control cell fate is unclear. Here, we report that deletion of an intrinsically disordered region of the pioneer factor TCF-1 (termed L1) leads to an early developmental block in T cells. The few T cells that develop from progenitors expressing TCF-1 lacking L1 exhibit lineage infidelity distinct from the lineage diversion of TCF-1-deficient cells. Mechanistically, L1 is required for activation of T cell genes and repression of GATA2-driven genes, normally reserved to the mast cell and dendritic cell lineages. Underlying this lineage diversion, L1 mediates binding of TCF-1 to its earliest target genes, which are subject to repression as T cells develop. These data suggest that the intrinsically disordered N terminus of TCF-1 maintains T cell lineage fidelity.

Tracing immune cells around biomaterials with spatial anchors during large-scale wound regeneration

Skin scarring devoid of dermal appendages after severe trauma has unfavorable effects on aesthetic and physiological functions. Here we present a method for large-area wound regeneration using biodegradable aligned extracellular matrix scaffolds. We show that the implantation of these scaffolds accelerates wound coverage and enhances hair follicle neogenesis. We perform multimodal analysis, in combination with single-cell RNA sequencing and spatial transcriptomics, to explore the immune responses around biomaterials, highlighting the potential role of regulatory T cells in mitigating tissue fibrous by suppressing excessive type 2 inflammation. We find that immunodeficient mice lacking mature T lymphocytes show the typical characteristic of tissue fibrous driven by type 2 macrophage inflammation, validating the potential therapeutic effect of the adaptive immune system activated by biomaterials. These findings contribute to our understanding of the coordination of immune systems in wound regeneration and facilitate the design of immunoregulatory biomaterials in the future.

T cell fate decisions during memory cell generation with aging

The defense against infectious diseases, either through natural immunity or after vaccinations, relies on the generation and maintenance of protective T cell memory. Naïve T cells are at the center of memory T cell generation during primary responses. Upon activation, they undergo a complex, highly regulated differentiation process towards different functional states. Naïve T cells maintained into older age have undergone epigenetic adaptations that influence their fate decisions during differentiation. We review age-sensitive, molecular pathways and gene regulatory networks that bias naïve T cell differentiation towards effector cell generation at the expense of memory and Tfh cells. As a result, T cell differentiation in older adults is associated with release of bioactive waste products into the microenvironment, higher stress sensitivity as well as skewing towards pro-inflammatory signatures and shorter life spans. These maladaptations not only contribute to poor vaccine responses in older adults but also fuel a more inflammatory state.

Clonal haematopoiesis and dysregulation of the immune system

Age-related diseases are frequently linked to pathological immune dysfunction, including excessive inflammation, autoreactivity and immunodeficiency. Recent analyses of human genetic data have revealed that somatic mutations and mosaic chromosomal alterations in blood cells - a condition known as clonal haematopoiesis (CH) - are associated with ageing and pathological immune dysfunction. Indeed, large-scale epidemiological studies and experimental mouse models have demonstrated that CH can promote cardiovascular disease, chronic obstructive pulmonary disease, chronic liver disease, osteoporosis and gout. The genes most frequently mutated in CH, the epigenetic regulators TET2 and DNMT3A, implicate increased chemokine expression and inflammasome hyperactivation in myeloid cells as a possible mechanistic connection between CH and age-related diseases. In addition, TET2 and DNMT3A mutations in lymphoid cells have been shown to drive methylation-dependent alterations in differentiation and function. Here we review the observational and mechanistic studies describing the connection between CH and pathological immune dysfunction, the effects of CH-associated genetic alterations on the function of myeloid and lymphoid cells, and the clinical and therapeutic implications of CH as a target for immunomodulation.

PD1 is transcriptionally regulated by LEF1 in mature T cells

The role of programmed cell death 1 (PD1) in cancer immune evasion is of considerable importance, prompting the development of monoclonal antibodies that specifically target PD-1 to enhance the immune system for cancer therapy. Nevertheless, the efficacy of PD1/programmed cell death-Ligand 1 (PD-L1) blocking antibodies is limited to certain patients or tumor types. Although researchers have demonstrated the influence of PD-1 on the positive selection of T cells, its effect on the T-cell repertoire remains uncertain. Lymphoid enhancer binding factor 1 (LEF1) has been known to play a critical role as a transcription factor in the development and maturation of T cells. Despite the greater focus on the study of its homologous protein, T cell factor 1 (TCF1), we discovered that LEF1 had a positive regulatory effect on the transcription of PD1 in mature T cells, including CD4+ T cells, CD8+ T cells, and Treg cells. This finding was observed in LEF1 knockout and LEF1-stimulated mice models. Additionally, we confirmed the direct regulation of PD1 by LEF1 in tumor-infiltrating lymphocytes through tumor-implantation experiments. The direct regulation of PD1 by LEF1 was further validated in the LEF1 knockout cell line. The results of our study provide novel perspectives on the regulation of PD1 in immune responses and investigate potential approaches for clinical anti-PD1 therapy.

Single-cell RNA sequencing reveals the effects of anti-PD-L1 therapy on 3LL lung cancer model and its tumor microenvironment

PD-L1 is expressed on antigen-presenting cells and tumor cells, thus allows tumor cells to escape immune surveillance. Moreover, targeting PD-L1 was also recommended and selected as important immune checkpoint inhibitors (ICIs) strategy in the treatment of advanced cancers due to the safety and activity. However, the detailed alteration of tumor microenvironment (TME) upon anti-PD-L1 therapy in lung cancer tumor model still needs to be resolved. In our present study, first, we characterized PD-L1 expression in human lung adenocarcinoma tissues by using public data, then we established the subcutaneous tumor-bearing model by using murine lung cancer cell line 3LL to perform the anti-PD-L1 therapy and the single-cell RNA sequencing (scRNA-seq) to reveal the remodeling of TME. We confirmed that PD-L1 blockade significantly inhibited tumor progression in 3LL mouse lung cancer model. The scRNA-seq depicted the detailed TME landscape of 3LL tumor model upon anti-PD-L1 treatment. Five major populations according to the marker genes were identified, including tumor cells, stromal cells, myeloid cells, T cells, and NK cells. In addition, we found that anti-PD-L1 treatment enhanced tumor immunogenicity and promoted inflammation in TME and promoted cancer-associated fibroblasts (CAFs)-mediated T-cell migration and infiltration. We also found that anti-PD-L1 treatment can increase dendritic cells (DCs) population and enhance the antigen-presenting ability to CD8+T cells and promote the transition of monocytes to macrophages and tumor-associated macrophages 2 (TAM2) to TAM1. We also revealed that Nfatc1 was up-regulated in the anti-PD-L1 treatment group, the frequencies of effector CD8+T cells, exhausted CD8+T cells, cycling T cells, and NKT were increased, and the frequencies of conventional CD4+T cells, Treg, IFN-induced T cells, and γδT cells were decreased. Therefore, our scRNA-seq data of the lung cancer tumor model upon anti-PD-L1 treatment made a comprehensive presentation and description about the remodeling of TME and will benefit us to understand the underlying mechanisms and to design combinational therapeutic strategies based on anti-PD-L1 therapy against lung cancer.