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.

Therapeutic potential of co-signaling receptor modulation in hepatitis B.

Reversing CD8+ T cell dysfunction is crucial in treating chronic hepatitis B virus (HBV) infection, yet specific molecular targets remain unclear. Our study analyzed co-signaling receptors during hepatocellular priming and traced the trajectory and fate of dysfunctional HBV-specific CD8+ T cells. Early on, these cells upregulate PD-1, CTLA-4, LAG-3, OX40, 4-1BB, and ICOS. While blocking co-inhibitory receptors had minimal effect, activating 4-1BB and OX40 converted them into antiviral effectors. Prolonged stimulation led to a self-renewing, long-lived, heterogeneous population with a unique transcriptional profile. This includes dysfunctional progenitor/stem-like (TSL) cells and two distinct dysfunctional tissue-resident memory (TRM) populations. While 4-1BB expression is ubiquitously maintained, OX40 expression is limited to TSL. In chronic settings, only 4-1BB stimulation conferred antiviral activity. In HBeAg+ chronic patients, 4-1BB activation showed the highest potential to rejuvenate dysfunctional CD8+ T cells. Targeting all dysfunctional T cells, rather than only stem-like precursors, holds promise for treating chronic HBV infection.

Lasting differential gene expression of circulating CD8 T cells in chronic HCV infection with cirrhosis identifies a role for Hedgehog signaling in cellular hyperfunction.

Background: The impact of chronic hepatic infection on antigen non-specific immune cells in circulation remains poorly understood. We reported lasting global hyperfunction of peripheral CD8 T cells in HCV-infected individuals with cirrhosis. Whether gene expression patterns in bulk CD8 T cells are associated with the severity of liver fibrosis in HCV infection is not known. Methods: RNA sequencing of blood CD8 T cells from treatment naïve, HCV-infected individuals with minimal (Metavir F0-1 ≤ 7.0 kPa) or advanced fibrosis or cirrhosis (F4 ≥ 12.5 kPa), before and after direct-acting antiviral therapy, was performed. CD8 T cell function was assessed by flow cytometry. Results: In CD8 T cells from pre-DAA patients with advanced compared to minimal fibrosis, Gene Ontology analysis and Gene Set Enrichment Analysis identified differential gene expression related to cellular function and metabolism, including upregulated Hedgehog (Hh) signaling, IFN-α, -γ, TGF-ß response genes, apoptosis, apical surface pathways, phospholipase signaling, phosphatidyl-choline/inositol activity, and second-messenger-mediated signaling. In contrast, genes in pathways associated with nuclear processes, RNA transport, cytoskeletal dynamics, cMyc/E2F regulation, oxidative phosphorylation, and mTOR signaling, were reduced. Hh signaling pathway was the top featured gene set upregulated in cirrhotics, wherein hallmark genes GLI1 and PTCH1 ranked highly. Inhibition of Smo-dependent Hh signaling ablated the expression of IFN-γ and perforin in stimulated CD8 T cells from chronic HCV-infected patients with advanced compared to minimal fibrosis. CD8 T cell gene expression profiles post-DAA remained clustered with pre-DAA profiles and disparately between advanced and minimal fibrosis, suggesting a persistent perturbation of gene expression long after viral clearance. Conclusions: This analysis of bulk CD8 T cell gene expression in chronic HCV infection suggests considerable reprogramming of the CD8 T cell pool in the cirrhotic state. Increased Hh signaling in cirrhosis may contribute to generalized CD8 T cell hyperfunction observed in chronic HCV infection. Understanding the lasting nature of immune cell dysfunction may help mitigate remaining clinical challenges after HCV clearance and more generally, improve long term outcomes for individuals with severe liver disease.

The complexities of T-cell dysfunction in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by profound alterations and defects in the T-cell compartment. This observation has gained renewed interest as T-cell treatment strategies, which are successfully applied in more aggressive B-cell malignancies, have yielded disappointing results in CLL. Despite ongoing efforts to understand and address the observed T-cell defects, the exact mechanisms and nature underlying this dysfunction remain largely unknown. In this review, we examine the supporting signals from T cells to CLL cells in the lymph node niche, summarize key findings on T-cell functional defects, delve into potential underlying causes, and explore novel strategies for reversing these deficiencies. Our goal is to identify strategies aimed at resolving CLL-induced T-cell dysfunction which, in the future, will enhance the efficacy of autologous T-cell-based therapies for CLL patients.

HBV DNA polymerase upregulates the transcription of PD-L1 and suppresses T cell activity in hepatocellular carcinoma.

BACKGROUND: In HBV-associated HCC, T cells often exhibit a state of functional exhaustion, which prevents the immune response from rejecting the tumor and allows HCC to progress. Moreover, polymerase-specific T cells exhibit more severe T-cell exhaustion compared to core-specific T cells. However, whether HBV DNA polymerase drives HBV-specific CD8+ T cell exhaustion in HBV-related HCC remains unclear. METHODS: We constructed a Huh7 cell line stably expressing HA-HBV-DNA-Pol and applied co-culture systems to clarify its effect on immune cell function. We also examined how HBV-DNA-Pol modulated PD-L1 expression in HCC cells. In addition, HBV-DNA-Pol transgenic mice were used to elucidate the underlying mechanism of HBV-DNA-Pol/PD-L1 axis-induced T cell exhaustion. RESULTS: Biochemical analysis showed that Huh7 cells overexpressing HBV-DNA-Pol inhibited the proliferation, activation, and cytokine secretion of Jurkat cells and that this effect was dependent on their direct contact. A similar inhibitory effect was observed in an HCC mouse model. PD-L1 was brought to our attention during screening. Our results showed that the overexpression of HBV-DNA-Pol upregulated PD-L1 mRNA and protein expression. PD-L1 antibody blockade reversed the inhibitory effect of Huh7 cells overexpressing HBV-DNA-Pol on Jurkat cells. Mechanistically, HBV-DNA-Pol interacts with PARP1, thereby inhibiting the nuclear translocation of PARP1 and further upregulating PD-L1 expression. CONCLUSIONS: Our findings suggest that HBV-DNA-Pol can act as a regulator of PD-L1 in HCC, thereby directing anti-cancer immune evasion, which further provides a new idea for the clinical treatment of liver cancer.

Identification of CD8 T-cell dysfunction associated with symptoms in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and Long COVID and treatment with a nebulized antioxidant/anti-pathogen agent in a retrospective case series.

Background: Patients with post-acute sequelae of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection (PASC, i.e., Long COVID) have a symptom complex highly analogous to many features of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), suggesting they may share some aspects of pathogenesis in these similar disorders. ME/CFS is a complex disease affecting numerous organ systems and biological processes and is often preceded by an infection-like episode. It is postulated that the chronic manifestations of illness may result from an altered host response to infection or inability to resolve inflammation, as is being reported in Long COVID. The immunopathogenesis of both disorders is still poorly understood. Here, we show data that suggest Long COVID and ME/CFS may be due to an aberrant response to an immunological trigger-like infection, resulting in a dysregulated immune system with CD8 T-cell dysfunction reminiscent of some aspects of T-cell clonal exhaustion, a phenomenon associated with oxidative stress. As there is an urgent need for diagnostic tools and treatment strategies for these two related disabling disorders, here, in a retrospective case series, we have also identified a potential nebulized antioxidant/anti-pathogen treatment that has evidence of a good safety profile. This nebulized agent is comprised of five ingredients previously reported individually to relieve oxidative stress, attenuate NF-κB signaling, and/or to act directly to inhibit pathogens, including viruses. Administration of this treatment by nebulizer results in rapid access of small doses of well-studied antioxidants and agents with anti-pathogen potential to the lungs; components of this nebulized agent are also likely to be distributed systemically, with potential to enter the central nervous system. Methods: and Findings: We conducted an analysis of CD8 T-cell function and severity of symptoms by self-report questionnaires in ME/CFS, Long COVID and healthy controls. We developed a CD8 T-cell functional assay, assessing CD8 T-cell dysfunction by intracellular cytokine staining (ICS) in a group of ME/CFS (n = 12) and Long COVID patients (n = 8), comparing to healthy controls (HC) with similar age and sex (n = 10). Magnet-enriched fresh CD8 T-cells in both patient groups had a significantly diminished capacity to produce both cytokines, IFNγ or TNFα, after PMA stimulation when compared to HC. The symptom severity questionnaire showed similar symptom profiles for the two disorders. Fortuitously, through a retrospective case series, we were able to examine the ICS and questionnaire data of 4 ME/CFS and 4 Long COVID patients in conjunction with their treatment (3-15 months). In parallel with the treatment pursued electively by participants in this retrospective case series, there was an increase in CD8 T-cell IFNγ and TNFα production and a decrease in overall self-reported symptom severity score by 54%. No serious treatment-associated side effects or laboratory anomalies were noted in these patients. Conclusions: Here, in this small study, we present two observations that appear potentially fundamental to the pathogenesis and treatment of Long COVID and ME/CFS. The first is that both disorders appear to be characterized by dysfunctional CD8 T-cells with severe deficiencies in their abilities to produce IFNγ and TNFα. The second is that in a small retrospective Long COVID and ME/CFS case series, this immune dysfunction and patient health improved in parallel with treatment with an immunomodulatory, antioxidant pharmacological treatment with anticipated anti-pathogen activity. This work provides evidence of the potential utility of a biomarker, CD8 T-cell dysfunction, and suggests the potential for benefit from a new nebulized antioxidant/anti-pathogen treatment. These immune biomarker data may help build capacity for improved diagnosis and tracking of treatment outcomes during clinical trials for both Long COVID and ME/CFS while providing clues to new treatment avenues that suggest potential efficacy for both conditions.

Examining Chronic Inflammation, Immune Metabolism, and T Cell Dysfunction in HIV Infection.

Chronic Human Immunodeficiency Virus (HIV) infection remains a significant challenge to global public health. Despite advances in antiretroviral therapy (ART), which has transformed HIV infection from a fatal disease into a manageable chronic condition, a definitive cure remains elusive. One of the key features of HIV infection is chronic immune activation and inflammation, which are strongly associated with, and predictive of, HIV disease progression, even in patients successfully treated with suppressive ART. Chronic inflammation is characterized by persistent inflammation, immune cell metabolic dysregulation, and cellular exhaustion and dysfunction. This review aims to summarize current knowledge of the interplay between chronic inflammation, immune metabolism, and T cell dysfunction in HIV infection, and also discusses the use of humanized mice models to study HIV immune pathogenesis and develop novel therapeutic strategies.

Inflammatory dendritic cells restrain CD11b+CD4+ CTLs via CD200R in human NSCLC.

CD4+ cytotoxic T lymphocytes (CD4+ CTLs) are suggested to play a crucial role in inflammatory diseases, including cancer, but their characteristics in human non-small cell lung cancer (NSCLC) remain unknown. Here, using the cell surface marker CD11b, we identify CD11b+CD4+ CTLs as a cytotoxic subset of CD4+ T cells in multiple tissues of NSCLC patients. In addition, tumor-infiltrating CD11b+CD4+ CTLs show a dysfunctional phenotype with elevated expression of CD200 receptor (CD200R), a negatively immunomodulatory receptor. CD4+ regulatory T (Treg) cells restrain the anti-tumor role of CD11b+CD4+ CTLs via CD200. Mechanistically, inflammatory dendritic cells promote the CD200R expression of CD11b+CD4+ CTLs by secreting interleukin-1ß (IL-1ß). Finally, we demonstrate that CD200 blockade can revive the tumor-killing role of CD11b+CD4+ CTLs and prolong the survival of tumor-bearing mice. Taken together, our study identifies CD11b+CD4+ CTLs in NSCLC with decreased cytotoxicity that can be reinvigorated by CD200 blockade, suggesting that targeting CD200 is a promising immunotherapy strategy in NSCLC.

Astragalus polysaccharide ameliorates CD8+ T cell dysfunction through STAT3/Gal-3/LAG3 pathway in inflammation-induced colorectal cancer.

Chronic inflammation can promote cancer development as observed in inflammation-induced colorectal cancer (CRC). However, the poor treatment outcomes emphasize the need for effective treatment. Astragalus polysaccharide (APS), a vital component of the natural drug Astragalus, has anti-tumor effects by inhibiting cancer cell proliferation and enhancing immune function. In this study, we found that APS effectively suppressed CRC development through activating CD8+ T cells and reversing its inhibitory state in the tumor microenvironment (TME) of AOM/DSS inflammation-induced CRC mice. Network pharmacology and clinical databases suggested that the STAT3/ Galectin-3(Gal-3)/LAG3 pathway might be APS's potential target for treating CRC and associated with CD8+ T cell dysfunction. In vivo experiments showed that APS significantly reduced phosphorylated STAT3 and Gal-3 levels in tumor cells, as well as LAG3 in CD8+ T cells. Co-culture experiments with MC38 and CD8+ T cells demonstrated that APS decreased the expression of co-inhibitory receptor LAG3 in CD8+ T cells by targeting STAT3/Gal-3 in MC38 cells. Mechanism investigations revealed that APS specifically improved CD8+ T cell function through modulation of the STAT3/Gal-3/LAG3 pathway to inhibit CRC development, providing insights for future clinical development of natural anti-tumor drugs and immunotherapies as a novel strategy combined with immune checkpoint inhibitors (ICIs).

CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing hemodialysis.

BACKGROUND: T cell dysfunction observed in patients undergoing hemodialysis (HD) has been linked to an extremely high morbidity of cardiovascular events (CVEs) and infections. The cell-surface 5'-nucleotidase CD73 sets the balance between pro-inflammatory nucleotides and anti-inflammatory adenosine. METHODS: A total of 395 patients who had been receiving HD for at least six months were evaluated for proportions of CD73+ cells in both the CD4+ T cell and CD8+ T cell compartment and followed for one year to document CVEs and infections. Differences in the proportions of CD73-expressingT cells between healthy controls and patients undergoing HD were compared. The relationship between CD73+ T cells and clinical outcomes was analyzed using the Kaplan-Meier curve and Cox regression. RESULTS: HD was significantly related to a lower fraction of CD4+CD73+ T cells. In patients on HD, lower proportions of CD4+ CD73+T cells and CD8+ CD73+T cells were both associated with systemic inflammation and T cell terminal differentiation. More importantly, a lower CD4+CD73+T cell ratio independently predicted CVEs and infection in these patients. CONCLUSION: We identified CD73 as a T cell dysfunction marker predicting cardiovascular and infection events in patients undergoing HD, which provides a potential target in future studies of uremia-related immune dysfunction.

PD1+TIGIT+2B4+KLRG1+ Cells Might Underlie T Cell Dysfunction in Patients Treated with BCMA-Directed Chimeric Antigen Receptor T Cell Therapy.

Chimeric antigen receptor T cell (CAR-T) therapy has shown rapid, frequent, and deep responses in patients with relapsed/refractory multiple myeloma (RRMM). However, relapse frequently occurs following CAR-T therapy, and the cause of this resistance is not well defined. Among the potential mechanisms of resistance, T cell intrinsic factors may be an important source of failure. Here we used spectral flow cytometry to identify the changes in T cell phenotypes in bone marrow aspirates at different stages of multiple myeloma progression, including cases that relapsed after anti-BCMA CAR-T therapy. We identified completely different T cell phenotypes in RRMM and post CAR-T relapse cases compared to healthy donors and earlier stages of multiple myeloma, novel double-negative CD3+ T cells in RRMM and CAR-T relapsed cases, and differences in CD8 T cell phenotype at the baseline between peripheral blood and bone marrow from healthy donors. We found that the majority of T cells in RRMM patients and significant T cell subsets in post-CAR-T relapsed patients expressed multiple coinhibitory markers, including PD1, TIGIT, 2B4, and KLRG1.

Blockade of C5a receptor unleashes tumor-associated macrophage antitumor response and enhances CXCL9-dependent CD8+ T cell activity.

Macrophages play a crucial role in shaping the immune state within the tumor microenvironment (TME) and are often influenced by tumors to hinder antitumor immunity. However, the underlying mechanisms are still elusive. Here, we observed abnormal expression of complement 5a receptor (C5aR) in human ovarian cancer (OC), and identified high levels of C5aR expression on tumor-associated macrophages (TAMs), which led to the polarization of TAMs toward an immunosuppressive phenotype. C5aR knockout or inhibitor treatment restored TAM antitumor response and attenuated tumor progression. Mechanistically, C5aR deficiency reprogrammed macrophages from a protumor state to an antitumor state, associating with the upregulation of immune response and stimulation pathways, which in turn resulted in the enhanced antitumor response of cytotoxic T cells in a manner dependent on chemokine (C-X-C motif) ligand 9 (CXCL9). The pharmacological inhibition of C5aR also improved the efficacy of immune checkpoint blockade therapy. In patients, C5aR expression associated with CXCL9 production and infiltration of CD8+ T cells, and a high C5aR level predicted poor clinical outcomes and worse benefits from anti-PD-1 therapy. Thus, our study sheds light on the mechanisms underlying the modulation of TAM antitumor immune response by the C5a-C5aR axis and highlights the potential of targeting C5aR for clinical applications.

Expansion of CD4+ cytotoxic T lymphocytes with specific gene expression patterns may contribute to suppression of tumor immunity in oral squamous cell carcinoma: single-cell analysis and in vitro experiments.

Background: Cancer immunotherapy targeting CD8+ T cells has made remarkable progress, even for oral squamous cell carcinoma (OSCC), a heterogeneous epithelial tumor without a substantial increase in the overall survival rate over the past decade. However, the therapeutic effects remain limited due to therapy resistance. Thus, a more comprehensive understanding of the roles of CD4+ T cells and B cells is crucial for more robust development of cancer immunotherapy. Methods: In this study, we examined immune responses and effector functions of CD4+ T cells, CD8+ T cells and B cells infiltrating in OSCC lesions using single-cell RNA sequencing analysis, T cell receptor (TCR) and B cell receptor (BCR) repertoire sequencing analysis, and multi-color immunofluorescence staining. Finally, two Kaplan-Meier curves and several Cox proportional hazards models were constructed for the survival analysis. Results: We observed expansion of CD4+ cytotoxic T lymphocytes (CTLs) expressing granzymes, which are reported to induce cell apoptosis, with a unique gene expression patterns. CD4+ CTLs also expressed CXCL13, which is a B cell chemoattractant. Cell-cell communication analysis and multi-color immunofluorescence staining demonstrated potential interactions between CD4+ CTLs and B cells, particularly IgD- CD27- double negative (DN) B cells. Expansion of CD4+ CTLs, DN B cells, and their contacts has been reported in T and B cell-activated diseases, including IgG4-related disease and COVID-19. Notably, we observed upregulation of several inhibitory receptor genes including CTLA-4 in CD4+ CTLs, which possibly dampened T and B cell activity. We next demonstrated comprehensive delineation of the potential for CD8+ T cell differentiation towards dysfunctional states. Furthermore, prognostic analysis revealed unfavorable outcomes of patients with a high proportion of CD4+ CTLs in OSCC lesions. Conclusion: Our study provides a dynamic landscape of lymphocytes and demonstrates a systemic investigation of CD4+ CTL effects infiltrating into OSCC lesions, which may share some pathogenesis reported in severe T and B cell-activated diseases such as autoimmune and infectious diseases.

Multi-omics analysis reveals interferon-stimulated gene OAS1 as a prognostic and immunological biomarker in pan-cancer.

Introduction: OAS1(2'-5'-oligoadenylate synthetase 1) is a member of the Interferon-Stimulated Genes which plays an important role in the antiviral process. In recent years, the role of OAS1 in tumors has attracted attention, and it was found to be associated with prognosis in several tumors. However, the mechanism by which OAS1 affects tumors is unclear and pan-cancer study of OAS1 is necessary to better understand its implication in cancers. Methods: The expression, prognostic value, genetic alteration, alternative splicing events of OAS1 in pan-cancers were analyzed using TCGA, GTEx, HPA, GEPIA and OncoSplicing databases. OAS1 associated immune cell infiltration was evaluated using the ESTIMATE, xCell, CIBERSORT and QUANTISEQ algorithm. Single cell transcriptome data download using TISH database. Finally, the roles of the OAS1 on apoptosis, migration and invasion were investigated in two pancreatic cancer cells. Results: Our results revealed significant differences in OAS1 expression among various tumors, which had prognostic implications. In addition, we investigated the impact of OAS1 on genomic stability, methylation status, and other factors across different types of cancer, and the effects of these factors on prognosis. Notably, our study also demonstrated that OAS1 overexpression can contribute to CTL dysfunction and macrophage M2 polarization. In addition, cell experiments showed that the knockdown of OAS1 could reduce the invasive ability and increased the apoptosis rate of PAAD cells. Discussion: These results confirmed that OAS1 could be a prognostic biomarker and therapeutic target for its potential role in CTL dysfunction and macrophage M2 polarization.

Systematic investigation of mitochondrial transfer between cancer cells and T cells at single-cell resolution.

Mitochondria (MT) participate in most metabolic activities of mammalian cells. A near-unidirectional mitochondrial transfer from T cells to cancer cells was recently observed to "metabolically empower" cancer cells while "depleting immune cells," providing new insights into tumor-T cell interaction and immune evasion. Here, we leverage single-cell RNA-seq technology and introduce MERCI, a statistical deconvolution method for tracing and quantifying mitochondrial trafficking between cancer and T cells. Through rigorous benchmarking and validation, MERCI accurately predicts the recipient cells and their relative mitochondrial compositions. Application of MERCI to human cancer samples identifies a reproducible MT transfer phenotype, with its signature genes involved in cytoskeleton remodeling, energy production, and TNF-α signaling pathways. Moreover, MT transfer is associated with increased cell cycle activity and poor clinical outcome across different cancer types. In summary, MERCI enables systematic investigation of an understudied aspect of tumor-T cell interactions that may lead to the development of therapeutic opportunities.

The paradox of aging: Aging-related shifts in T cell function and metabolism.

T cell survival, differentiation after stimulation, and function are intrinsically linked to distinct cellular metabolic states. The ability of T cells to readily transition between metabolic states enables flexibility to meet the changing energy demands defined by distinct effector states or T cell lineages. Immune aging is characterized, in part, by the loss of naïve T cells, accumulation of senescent T cells, severe dysfunction in memory phenotype T cells in particular, and elevated levels of inflammatory cytokines, or 'inflammaging'. Here, we review our current understanding of the phenotypic and functional changes that occur with aging in T cells, and how they relate to metabolic changes in the steady state and after T cell activation. We discuss the apparent contradictions in the aging T cell phenotype - where enhanced differentiation states and metabolic profiles in the steady state can correspond to a diminished capacity to adapt metabolically and functionally after T cell activation. Finally, we discuss key recent studies that indicate the enormous potential for aged T cell metabolism to induce systemic inflammaging and organism-wide multimorbidity, resulting in premature death.

Tumor immunogenicity dictates reliance on TCF1 in CD8+ T cells for response to immunotherapy.

Stem-like CD8+ T cells are regulated by T cell factor 1 (TCF1) and are considered requisite for immune checkpoint blockade (ICB) response. However, recent findings indicate that reliance on TCF1+CD8+ T cells for ICB efficacy may differ across tumor contexts. We find that TCF1 is essential for optimal priming of tumor antigen-specific CD8+ T cells and ICB response in poorly immunogenic tumors that accumulate TOX+ dysfunctional T cells, but is dispensable for T cell priming and therapy response in highly immunogenic tumors that efficiently expand transitory effectors. Importantly, improving T cell priming by vaccination or by enhancing antigen presentation on tumors rescues the defective responses of TCF1-deficient CD8+ T cells upon ICB in poorly immunogenic tumors. Our study highlights TCF1's role during the early stages of anti-tumor CD8+ T cell responses with important implications for guiding optimal therapeutic interventions in cancers with low TCF1+CD8+ T cells and low-neo-antigen expression.

Effects of PYCR1 on prognosis and immunotherapy plus tyrosine kinase inhibition responsiveness in metastatic renal cell carcinoma patients.

BACKGROUND: Immunotherapy plus tyrosine kinase inhibitor (IO-TKI) has become the first-line management for metastatic renal cell carcinoma (RCC), despite the absence of biomarkers. Recently, pyrroline-5-carboxylate reductase 1 (PYCR1) and proline metabolism have been reported regulatory roles in the anti-tumor response. METHODS: There were three cohorts enrolled: two from our institution (ZS-MRCC and ZS-HRRCC) and one from a clinical trial (JAVELIN-101). The PYCR1expression in each sample was evaluated by RNA sequencing. Flow cytometry and immunohistochemistry were performed to assess immune infiltration. Single-cell RNA-seq (scRNA-seq) data was used for cluster analysis of T cells and macrophages. Primary endpoints were set as response and progression-free survival (PFS). RESULTS: Patients in the low-PYCR1 group had greater objective response rate (52.2% vs 18.2%) and longer PFS in both cohorts (ZS-MRCC cohort, P=0.01, HR=2.80; JAVELIN-101 cohort, P<0.001, HR=1.85). In responders, PYCR1 expression was decreased (P<0.05). In the high PYCR1 group, CD8+ T cells exhibited an exhausted phenotype with decreased GZMB (Spearman's ρ=-0.36, P=0.02). scRNA-seq revealed tissue-resident memory T (Trm) (P<0.05) and tissue-resident macrophage (P<0.01) were decreased in samples with high PYCR1 expression. A machine learning score was further built by random forest, involving PYCR1 and Trm markers. Only in the subgroup with the lower RFscore did IO+TKI show a favorable outcome, compared to TKI monotherapy. CONCLUSIONS: Immunosuppression and IO+TKI resistance were correlated with high PYCR1 expression. T cell exhaustion and dysfunction were also related with the expression of PYCR1. PYCR1 has the potential to be employed as a biomarker to discriminate between IO+TKI and TKI monotherapy as the optimal patient treatment strategy.

Exhausted T cells hijacking the cancer-immunity cycle: Assets and liabilities.

T cell exhaustion is an alternative differentiation path of T cells, sometimes described as a dysfunction. During the last decade, insights of T cell exhaustion acting as a bottle neck in the field of cancer immunotherapy have undoubtedly provoked attention. One of the main drivers of T cell exhaustion is prolonged antigen presentation, a prerequisite in the cancer-immunity cycle. The umbrella term "T cell exhaustion" comprises various stages of T cell functionalities, describing the dynamic, one-way exhaustion process. Together these qualities of T cells at the exhaustion continuum can enable tumor clearance, but if the exhaustion acquired timeframe is exceeded, tumor cells have increased possibilities of escaping immune system surveillance. This could be considered a tipping point where exhausted T cells switch from an asset to a liability. In this review, the contrary role of exhausted T cells is discussed.