Characterization of circulating T cells specific for tumor-associated antigens in melanoma patients

Tissue-resident memory T cells: Harnessing their properties against infection for cancer treatment

We have rapidly gained insights into the presence and function of T lymphocytes in non-lymphoid tissues, the tissue-resident memory T (TRM) cells. The central pillar of adaptive immunity has been expanded from classic central memory T cells giving rise to progeny upon reinfection and effector memory cells circulating through the blood and patrolling the tissues to include TRM cells that reside and migrate inside solid organs and tissues. Their development and maintenance have been studied in detail, providing exciting clues on how their unique properties used to fight infections may benefit therapies against solid tumors. We provide an overview of CD8 TRM cells and the properties that make them of interest for vaccination and cancer therapies.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Syringeable Near-Infrared Light-Activated In Situ Immunogenic Hydrogel Boosts the Cancer-Immunity Cycle to Enhance Anticancer Immunity

Effective anticancer immunity depends on properly activating multiple stepwise events in the cancer-immunity cycle. An immunologically "cold" tumor microenvironment (TME) engenders immune evasion and refractoriness to conventional checkpoint blockade immunotherapy. Here, we combine nanoparticle formulations and an in situ formed hydrogel scaffold to treat accessible tumors locally and to stimulate systemic immunity against metastatic tumor lesions. The nanoparticles encapsulate poly(ε-caprolactone)-derived cytotoxic chemotherapy and adjuvant of Toll-like receptor 7/8 through a reactive oxygen species (ROS)-cleavable linker that can be self-activated by the coassembled neighboring photosensitizer following near-infrared (NIR) laser irradiation. Further development results in syringeable, NIR light-responsive, and immunogenic hydrogel (iGEL) that can be implanted peritumorally and deposited into the tumor surgical bed. Upon NIR laser irradiation, the generated ROS induces iGEL degradation and bond cleavage in the polymer-drug conjugates, triggering the immunogenic cell death cascade in cancer cells and spontaneously releasing encapsulated agents to rewire the cancer-immunity cycle. Notably, upon application in multiple preclinical models of melanoma and triple-negative breast cancer, which are aggressive and refractory to conventional immunotherapy, iGEL induces durable remission of established tumors, extends postsurgical tumor-free survival, and inhibits metastatic burden. The result of this study is a locally administrable immunogenic hydrogel for triggering host systemic immunity to improve immunotherapeutic efficacy with minimal off-target side effects.

The Deep Learning Framework iCanTCR Enables Early Cancer Detection Using the T-cell Receptor Repertoire in Peripheral Blood

T cells recognize tumor antigens and initiate an anticancer immune response in the very early stages of tumor development, and the antigen specificity of T cells is determined by the T-cell receptor (TCR). Therefore, monitoring changes in the TCR repertoire in peripheral blood may offer a strategy to detect various cancers at a relatively early stage. Here, we developed the deep learning framework iCanTCR to identify patients with cancer based on the TCR repertoire. The iCanTCR framework uses TCRβ sequences from an individual as an input and outputs the predicted cancer probability. The model was trained on over 2,000 publicly available TCR repertoires from 11 types of cancer and healthy controls. Analysis of several additional publicly available datasets validated the ability of iCanTCR to distinguish patients with cancer from noncancer individuals and demonstrated the capability of iCanTCR for the accurate classification of multiple cancers. Importantly, iCanTCR precisely identified individuals with early-stage cancer with an AUC of 86%. Altogether, this work provides a liquid biopsy approach to capture immune signals from peripheral blood for noninvasive cancer diagnosis.

SIGNIFICANCE

Development of a deep learning-based method for multicancer detection using the TCR repertoire in the peripheral blood establishes the potential of evaluating circulating immune signals for noninvasive early cancer detection.

Nanotechnology Applications in Breast Cancer Immunotherapy

Next-generation cancer treatments are expected not only to target cancer cells but also to simultaneously train immune cells to combat cancer while modulating the immune-suppressive environment of tumors and hosts to ensure a robust and lasting response. Achieving this requires carriers that can codeliver multiple therapeutics to the right cancer and/or immune cells while ensuring patient safety. Nanotechnology holds great potential for addressing these challenges. This article highlights the recent advances in nanoimmunotherapeutic development, with a focus on breast cancer. While immune checkpoint inhibitors (ICIs) have achieved remarkable success and lead to cures in some cancers, their response rate in breast cancer is low. The poor response rate in solid tumors is often associated with the low infiltration of anti-cancer T cells and an immunosuppressive tumor microenvironment (TME). To enhance anti-cancer T-cell responses, nanoparticles are employed to deliver ICIs, bispecific antibodies, cytokines, and agents that induce immunogenic cancer cell death (ICD). Additionally, nanoparticles are used to manipulate various components of the TME, such as immunosuppressive myeloid cells, macrophages, dendritic cells, and fibroblasts to improve T-cell activities. Finally, this article discusses the outlook, challenges, and future directions of nanoimmunotherapeutics.

Phenotypic signatures of circulating neoantigen-reactive CD8+ T cells in patients with metastatic cancers

Circulating T cells from peripheral blood (PBL) can provide a rich and noninvasive source for antitumor T cells. By single-cell transcriptomic profiling of 36 neoantigen-specific T cell clones from 6 metastatic cancer patients, we report the transcriptional and cell surface signatures of antitumor PBL-derived CD8+ T cells (NeoTCRPBL). Comparison of tumor-infiltrating lymphocyte (TIL)- and PBL-neoantigen-specific T cells revealed that NeoTCRPBL T cells are low in frequency and display less-dysfunctional memory phenotypes relative to their TIL counterparts. Analysis of 100 antitumor TCR clonotypes indicates that most NeoTCRPBL populations target the same neoantigens as TILs. However, NeoTCRPBL TCR repertoire is only partially shared with TIL. Prediction and testing of NeoTCRPBL signature-derived TCRs from PBL of 6 prospective patients demonstrate high enrichment of clonotypes targeting tumor mutations, a viral oncogene, and patient-derived tumor. Thus, the NeoTCRPBL signature provides an alternative source for identifying antitumor T cells from PBL of cancer patients, enabling immune monitoring and immunotherapies.

Tumor-infiltrating CCR2+ inflammatory monocytes counteract specific immunotherapy

Tumor development and progression is shaped by the tumor microenvironment (TME), a heterogeneous assembly of infiltrating and resident host cells, their secreted mediators and intercellular matrix. In this context, tumors are infiltrated by various immune cells with either pro-tumoral or anti-tumoral functions. Recently, we published our non-invasive immunization platform DIVA suitable as a therapeutic vaccination method, further optimized by repeated application (DIVA2). In our present work, we revealed the therapeutic effect of DIVA2 in an MC38 tumor model and specifically focused on the mechanisms induced in the TME after immunization. DIVA2 resulted in transient tumor control followed by an immune evasion phase within three weeks after the initial tumor inoculation. High-dimensional flow cytometry analysis and single-cell mRNA-sequencing of tumor-infiltrating leukocytes revealed cytotoxic CD8+ T cells as key players in the immune control phase. In the immune evasion phase, inflammatory CCR2+ PDL-1+ monocytes with immunosuppressive properties were recruited into the tumor leading to suppression of DIVA2-induced tumor-reactive T cells. Depletion of CCR2+ cells with specific antibodies resulted in prolonged survival revealing CCR2+ monocytes as important for tumor immune escape in the TME. In summary, the present work provides a platform for generating a strong antigen-specific primary and memory T cell immune response using the optimized transcutaneous immunization method DIVA2. This enables protection against tumors by therapeutic immune control of solid tumors and highlights the immunosuppressive influence of tumor infiltrating CCR2+ monocytes that need to be inactivated in addition for successful cancer immunotherapy.

Insight into immune profile associated with vitiligo onset and anti-tumoral response in melanoma patients receiving anti-PD-1 immunotherapy

Introduction

Immunotherapy with checkpoint inhibitors is an efficient treatment for metastatic melanoma. Development of vitiligo upon immunotherapy represents a specific immune-related adverse event (irAE) diagnosed in 15% of patients and associated with a positive clinical response. Therefore, a detailed characterization of immune cells during vitiligo onset in melanoma patients would give insight into the immune mechanisms mediating both the irAE and the anti-tumor response.

Methods

To better understand these aspects, we analyzed T cell subsets from peripheral blood of metastatic melanoma patients undergoing treatment with anti-programmed cell death protein (PD)-1 antibodies. To deeply characterize the antitumoral T cell response concomitant to vitiligo onset, we analyzed T cell content in skin biopsies collected from melanoma patients who developed vitiligo. Moreover, to further characterize T cells in vitiligo skin lesion of melanoma patients, we sequenced T cell receptor (TCR) of cells derived from biopsies of vitiligo and primary melanoma of the same patient.

Results and discussion

Stratification of patients for developing or not developing vitiligo during anti-PD-1 therapy revealed an association between blood reduction of CD8-mucosal associated invariant T (MAIT), T helper (h) 17, natural killer (NK) CD56bright, and T regulatory (T-reg) cells and vitiligo onset. Consistently with the observed blood reduction of Th17 cells in melanoma patients developing vitiligo during immunotherapy, we found high amount of IL-17A expressing cells in the vitiligo skin biopsy, suggesting a possible migration of Th17 cells from the blood into the autoimmune lesion. Interestingly, except for a few cases, we found different TCR sequences between vitiligo and primary melanoma lesions. In contrast, shared TCR sequences were identified between vitiligo and metastatic tissues of the same patient. These data indicate that T cell response against normal melanocytes, which is involved in vitiligo onset, is not typically mediated by reactivation of specific T cell clones infiltrating primary melanoma but may be elicited by T cell clones targeting metastatic tissues. Altogether, our data indicate that anti-PD-1 therapy induces a de novo immune response, stimulated by the presence of metastatic cells, and composed of different T cell subtypes, which may trigger the development of vitiligo and the response against metastatic tumor.

The current state and future of T-cell exhaustion research

'Exhaustion' is a term used to describe a state of native and redirected T-cell hypo-responsiveness resulting from persistent antigen exposure during chronic viral infections or cancer. Although a well-established phenotype across mice and humans, exhaustion at the molecular level remains poorly defined and inconsistent across the literature. This is, in part, due to an overreliance on surface receptors to define these cells and explain exhaustive behaviours, an incomplete understanding of how exhaustion arises, and a lack of clarity over whether exhaustion is the same across contexts, e.g. chronic viral infections versus cancer. With the development of systems-based genetic approaches such as single-cell RNA-seq and CRISPR screens applied to in vivo data, we are moving closer to a consensus view of exhaustion, although understanding how it arises remains challenging given the difficulty in manipulating the in vivo setting. Accordingly, producing and studying exhausted T-cells ex vivo are burgeoning, allowing experiments to be conducted at scale up and with high throughput. Here, we first review what is currently known about T-cell exhaustion and how it's being studied. We then discuss how improvements in their method of isolation/production and examining the impact of different microenvironmental signals and cell interactions have now become an active area of research. Finally, we discuss what the future holds for the analysis of this physiological condition and, given the diversity of ways in which exhausted cells are now being generated, propose the adoption of a unified approach to clearly defining exhaustion using a set of metabolic-, epigenetic-, transcriptional-, and activation-based phenotypic markers, that we call 'M.E.T.A'.

Antigen-specific and cross-reactive T cells in protection and disease

Human T cells have a diverse T-cell receptor (TCR) repertoire that endows them with the ability to identify and defend against a broad spectrum of antigens. The universe of possible antigens that T cells may encounter, however, is even larger. To effectively surveil such a vast universe, the T-cell repertoire must adopt a high degree of cross-reactivity. Likewise, antigen-specific and cross-reactive T-cell responses play pivotal roles in both protective and pathological immune responses in numerous diseases. In this review, we explore the implications of these antigen-driven T-cell responses, with a particular focus on CD8+ T cells, using infection, neurodegeneration, and cancer as examples. We also summarize recent technological advances that facilitate high-throughput profiling of antigen-specific and cross-reactive T-cell responses experimentally, as well as computational biology approaches that predict these interactions.

Metformin as a booster of cancer immunotherapy

Metformin, a biguanide antidiabetic, has been studied for its repurposing effects in oncology. Although a modest effect was observed in a single-agent regimen, metformin can synergize the anti-tumor effects of other modalities. The promising combination for cancer treatment is with immunotherapy. Despite high efficacy for some cancers, immunotherapy could be limited by modulation of the tumor immune microenvironment and the immune exhaustion of cytotoxic immune cells. Combining immunotherapy with metformin, thus, exerted a rescuing effect of immunotherapy and potentiated the anti-tumor effects of each other. Although not fully understood, metformin shows promoting effects of immunotherapy by several mechanisms. Those proposed mechanisms have been partially proven and are suggested for possible therapeutic strategies for cancer treatment. In this review, a state-of-the-art of metformin's boosting effects on immunotherapy is reviewed and discussed. The future directions for metformin research in preclinical and clinical immunotherapy are also suggested.

Emerging hallmark of gliomas microenvironment in evading immunity: a basic concept

Background

Over the last decade, since clinical trials examining targeted therapeutics for gliomas have failed to demonstrate a meaningful increase in survival, the emphasis has recently been switched toward innovative techniques for modulating the immune response against tumors and their microenvironments (TME). Cancerous cells have eleven hallmarks which make it distinct from normal ones, among which is immune evasion. Immune evasion in glioblastoma helps it evade various treatment modalities.

Summary

Glioblastoma’s TME is composed of various array of cellular actors, ranging from peripherally derived immune cells to a variety of organ-resident specialized cell types. For example, the blood–brain barrier (BBB) serves as a selective barrier between the systemic circulation and the brain, which effectively separates it from other tissues. It is capable of blocking around 98% of molecules that transport different medications to the target tumor.

Objectives

The purpose of this paper is to offer a concise overview of fundamental immunology and how ‘clever’ gliomas avoid the immune system despite the discovery of immunotherapy for glioma.

Conclusions

Herein, we highlight the complex interplay of the tumor, the TME, and the nearby normal structures makes it difficult to grasp how to approach the tumor itself. Numerous researchers have found that the brain TME is a critical regulator of glioma growth and treatment efficacy.

Dissecting the immune suppressive human prostate tumor microenvironment via integrated single-cell and spatial transcriptomic analyses

The treatment of low-risk primary prostate cancer entails active surveillance only, while high-risk disease requires multimodal treatment including surgery, radiation therapy, and hormonal therapy. Recurrence and development of metastatic disease remains a clinical problem, without a clear understanding of what drives immune escape and tumor progression. Here, we comprehensively describe the tumor microenvironment of localized prostate cancer in comparison with adjacent normal samples and healthy controls. Single-cell RNA sequencing and high-resolution spatial transcriptomic analyses reveal tumor context dependent changes in gene expression. Our data indicate that an immune suppressive tumor microenvironment associates with suppressive myeloid populations and exhausted T-cells, in addition to high stromal angiogenic activity. We infer cell-to-cell relationships from high throughput ligand-receptor interaction measurements within undissociated tissue sections. Our work thus provides a highly detailed and comprehensive resource of the prostate tumor microenvironment as well as tumor-stromal cell interactions.

Platelet-derived TLT-1 promotes tumor progression by suppressing CD8+ T cells

Current understanding of tumor immunosuppressive mechanisms forms the basis for modern day immunotherapies. Immunoregulatory role of platelets in cancer remains largely elusive. Platelets from non-small cell lung cancer (NSCLC) patients revealed a distinct activation phenotype. TREM-like transcript 1 (TLT-1), a platelet protein, was increased along with enhanced extracellular release from NSCLC platelets. The increased platelet TLT-1 was also evident in humanized mice with patient-derived tumors. In immunocompetent mice with syngeneic tumors, TLT-1 binding to T cells, in vivo, led to suppression of CD8 T cells, promoting tumor growth. We identified direct interaction between TLT-1 and CD3ε on T cells, implicating the NF-κB pathway in CD8 T cell suppression. Anti-TLT-1 antibody rescued patients' T cells from platelet-induced suppression ex vivo and reduced tumors in mice in vivo. Clinically, higher TLT-1 correlated with reduced survival of NSCLC patients. Our findings thus identify TLT-1 as a platelet-derived immunosuppressor that suppresses CD8 T cells and demonstrate its therapeutic and prognostic significance in cancer.

Multiple instance neural networks based on sparse attention for cancer detection using T-cell receptor sequences

Early detection of cancers has been much explored due to its paramount importance in biomedical fields. Among different types of data used to answer this biological question, studies based on T cell receptors (TCRs) are under recent spotlight due to the growing appreciation of the roles of the host immunity system in tumor biology. However, the one-to-many correspondence between a patient and multiple TCR sequences hinders researchers from simply adopting classical statistical/machine learning methods. There were recent attempts to model this type of data in the context of multiple instance learning (MIL). Despite the novel application of MIL to cancer detection using TCR sequences and the demonstrated adequate performance in several tumor types, there is still room for improvement, especially for certain cancer types. Furthermore, explainable neural network models are not fully investigated for this application. In this article, we propose multiple instance neural networks based on sparse attention (MINN-SA) to enhance the performance in cancer detection and explainability. The sparse attention structure drops out uninformative instances in each bag, achieving both interpretability and better predictive performance in combination with the skip connection. Our experiments show that MINN-SA yields the highest area under the ROC curve scores on average measured across 10 different types of cancers, compared to existing MIL approaches. Moreover, we observe from the estimated attentions that MINN-SA can identify the TCRs that are specific for tumor antigens in the same T cell repertoire.

Peripheral T cell cytotoxicity predicts the efficacy of anti-PD-1 therapy for advanced non-small cell lung cancer patients

Anti-programmed cell death-1 (PD-1) therapy exerts beneficial effects in a limited population of cancer patients. Therefore, more accurate diagnostics to predict the efficacy of anti-PD-1 therapy are desired. The present study investigated whether peripheral T cell cytotoxicity predicts the efficacy of anti-PD-1 therapy for advanced non-small cell lung cancer (NSCLC) patients. Advanced NSCLC patients treated with anti-PD-1 monotherapy (nivolumab or pembrolizumab) were consecutively enrolled in the present study. Peripheral blood samples were subjected to an analysis of peripheral T cell cytotoxicity and flow cytometry prior to the initiation of anti-PD-1 therapy. Peripheral T cell cytotoxicity was assessed using bispecific T-cell engager (BiTE) technology. We found that progression-free survival was significantly longer in patients with high peripheral T cell cytotoxicity (p = 0.0094). In the multivariate analysis, treatment line and peripheral T cell cytotoxicity were independent prognostic factors for progression-free survival. The analysis of T cell profiles revealed that peripheral T cell cytotoxicity correlated with the ratio of the effector memory population in CD4+ or CD8+ T cells. Furthermore, the results of flow cytometry showed that the peripheral CD45RA+CD25+/CD4+ T cell ratio was higher in patients with than in those without severe adverse events (p = 0.0076). These results indicated that the peripheral T cell cytotoxicity predicted the efficacy of anti-PD-1 therapy for advanced NSCLC patients.

Loss of CD47 alters CD8+ T cell activation in vitro and immunodynamics in mice

CD47 has established roles in the immune system for regulating macrophage phagocytosis and lymphocyte activation, with growing evidence of its cell-intrinsic regulatory roles in natural killer and CD8+ T cells. CD47 limits antigen-dependent cytotoxic activities of human and murine CD8+ T cells, but its role in T cell activation kinetics remains unclear. Using in vitro and in vivo models, we show here that CD47 differentially regulates CD8+ T cell responses to short- versus long-term activation. Although CD47 was not required for T cell development in mice and early activation in vitro, short-term stimuli elevated pathogen-reactive gene expression and enhanced proliferation and the effector phenotypes of Cd47-deficient relative to Cd47-sufficient CD8+ T cells. In contrast, persistent TCR stimulation limited the effector phenotypes of Cd47 -/- CD8+ T cells and enhanced their apoptosis signature. CD8+ T cell expansion and activation in vivo induced by acute lymphocytic choriomeningitis virus (LCMV) infection did not differ in the absence of CD47. However, the frequency and effector phenotypes of Cd47-/- CD8+ T cells were constrained in chronic LCMV-infected as well as in mice bearing B16 melanoma tumors. Therefore, CD47 regulates CD8+ T cell activation, proliferation, and fitness in a context-dependent manner.

Evaluation of clonality from multiple anatomic sites in canine epitheliotropic T cell lymphoma

BACKGROUND

Canine epitheliotropic cutaneous T-cell lymphoma (eCTCL) is thought to represent a disease homologue to human mycosis fungoides (MF). In human MF, neoplastic cells are phenotypically consistent with resident effector memory T cells, a population that remains for an extended period within tissue without circulating. Dogs with eCTCL often present with lesions in multiple locations, raising the question of whether the neoplasm is of the same T-cell subpopulation or not.

OBJECTIVES

To characterize the antigen receptor gene rearrangements of lymphocytes from skin and blood of dogs with eCTCL to determine if neoplastic clones are identical.

ANIMALS

Fourteen dogs with eCTCL.

MATERIALS AND METHODS

Histological and immunohistochemical examination, and PCR for antigen receptor rearrangement (PARR) for T-cell receptor gamma (TRG) performed on multiple cutaneous biopsy samples and blood.

RESULTS

All skin biopsies contained cluster of differentiation (CD)3-positive neoplastic lymphocytes. Within individual dogs, all skin biopsies revealed identical TRG clonality profiles, suggesting that the same neoplastic clone was present in all sites. In the blood, a matching clone was found in six of 14 dogs, a unique clone was observed in nine of 14 dogs, and no clone was detected in two of 14 dogs.

CONCLUSIONS

These findings show that canine eCTCL lesions in multiple locations harbour the same neoplastic clone, neoplastic lymphocytes do not remain fixed to the skin and instead can circulate via blood, differing clones can be identified in skin versus blood, and circulating neoplastic cells can be detected without lymphocytosis.

A Highly Effective System for Predicting MHC-II Epitopes With Immunogenicity

In the past decade, the substantial achievements of therapeutic cancer vaccines have shed a new light on cancer immunotherapy. The major challenge for designing potent therapeutic cancer vaccines is to identify neoantigens capable of inducing sufficient immune responses, especially involving major histocompatibility complex (MHC)-II epitopes. However, most previous studies on T-cell epitopes were focused on either ligand binding or antigen presentation by MHC rather than the immunogenicity of T-cell epitopes. In order to better facilitate a therapeutic vaccine design, in this study, we propose a revolutionary new tool: a convolutional neural network model named FIONA (Flexible Immunogenicity Optimization Neural-network Architecture) trained on IEDB datasets. FIONA could accurately predict the epitopes presented by the given specific MHC-II subtypes, as well as their immunogenicity. By leveraging the human leukocyte antigen allele hierarchical encoding model together with peptide dense embedding fusion encoding, FIONA (with AUC = 0.94) outperforms several other tools in predicting epitopes presented by MHC-II subtypes in head-to-head comparison; moreover, FIONA has unprecedentedly incorporated the capacity to predict the immunogenicity of epitopes with MHC-II subtype specificity. Therefore, we developed a reliable pipeline to effectively predict CD4+ T-cell immune responses against cancer and infectious diseases.

Novel Mouse Models for Cancer Immunology

Mouse models for the study of cancer immunology provide excellent systems in which to test biological mechanisms of the immune response against cancer. Historically, these models have been designed to have different strengths based on the current major research questions at the time. As such, many mouse models of immunology used today were not originally developed to study questions currently plaguing the relatively new field of cancer immunology, but instead have been adapted for such purposes. In this review, we discuss various mouse model of cancer immunology in a historical context as a means to provide a fuller perspective of each model's strengths. From this outlook, we discuss the current state of the art and strategies for tackling future modeling challenges.

T-cell Exhaustion in Organ Transplantation

Exhaustion of T cells occurs in response to long-term exposure to self and foreign antigens. It limits T cell capacity to proliferate and produce cytokines, leading to an impaired ability to clear chronic infections or eradicate tumors. T-cell exhaustion is associated with a specific transcriptional, epigenetic, and metabolic program and characteristic cell surface markers' expression. Recent studies have begun to elucidate the role of T-cell exhaustion in transplant. Higher levels of exhausted T cells have been associated with better graft function in kidney transplant recipients. In contrast, reinvigorating exhausted T cells by immune checkpoint blockade therapies, while promoting tumor clearance, increases the risk of acute rejection. Lymphocyte depletion and high alloantigen load have been identified as major drivers of T-cell exhaustion. This could account, at least in part, for the reduced rates of acute rejection in organ transplant recipients induced with thymoglobulin and for the pro-tolerogenic effects of a large organ such as the liver. Among the drugs that are widely used for maintenance immunosuppression, calcineurin inhibitors have a contrasting inhibitory effect on exhaustion of T cells, while the influence of mTOR inhibitors is still unclear. Harnessing or encouraging the natural processes of exhaustion may provide a novel strategy to promote graft survival and transplantation tolerance.

An In Vivo Screen to Identify Short Peptide Mimotopes with Enhanced Antitumor Immunogenicity

Tumor-associated self-antigens are potential cancer vaccine targets but suffer from limited immunogenicity. There are examples of mutated, short self-peptides inducing epitope-specific CD8⁺ T cells more efficiently than the wild-type epitope, but current approaches cannot yet reliably identify such epitopes, which are referred to as enhanced mimotopes ("e-mimotopes"). Here, we present a generalized strategy to develop e-mimotopes, using the tyrosinase-related protein 2 (Trp2) peptide Trp2180-188, which is a murine major histocompatibility complex class I (MHC-I) epitope, as a test case. Using a vaccine adjuvant that induces peptide particle formation and strong cellular responses with nanogram antigen doses, a two-step method systematically identified e-mimotope candidates with murine immunization. First, position-scanning peptide micro libraries were generated in which each position of the wild-type epitope sequence was randomized. Randomization of only one specific residue of the Trp2 epitope increased antitumor immunogenicity. Second, all 20 amino acids were individually substituted and tested at that position, enabling the identification of two e-mimotopes with single amino-acid mutations. Despite similar MHC-I affinity compared to the wild-type epitope, e-mimotope immunization elicited improved Trp2-specific cytotoxic T-cell phenotypes and improved T-cell receptor affinity for both the e-mimotopes and the native epitope, resulting in better outcomes in multiple prophylactic and therapeutic tumor models. The screening method was also applied to other targets with other murine MHC-I restriction elements, including epitopes within glycoprotein 70 and Wilms' Tumor Gene 1, to identify additional e-mimotopes with enhanced potency.

A high OXPHOS CD8 T cell subset is predictive of immunotherapy resistance in melanoma patients

Immune checkpoint inhibitor (ICI) therapy continues to revolutionize melanoma treatment, but only a subset of patients respond. Major efforts are underway to develop minimally invasive predictive assays of ICI response. Using single-cell transcriptomics, we discovered a unique CD8 T cell blood/tumor-shared subpopulation in melanoma patients with high levels of oxidative phosphorylation (OXPHOS), the ectonucleotidases CD38 and CD39, and both exhaustion and cytotoxicity markers. We called this population with high levels of OXPHOS “CD8⁺ T_OXPHOS cells.” We validated that higher levels of OXPHOS in tumor- and peripheral blood–derived CD8⁺ T_OXPHOS cells correlated with ICI resistance in melanoma patients. We then developed an ICI therapy response predictive model using a transcriptomic profile of CD8⁺ T_OXPHOS cells. This model is capable of discerning responders from nonresponders using either tumor or peripheral blood CD8 T cells with high accuracy in multiple validation cohorts. In sum, CD8⁺ T_OXPHOS cells represent a critical immune population to assess ICI response with the potential to be a new target to improve outcomes in melanoma patients.

Molecular characterization of hypoxanthine guanine phosphoribosyltransferase mutant T cells in human blood: The concept of surrogate selection for immunologically relevant cells

Somatic cell gene mutations arise in vivo due to replication errors during DNA synthesis occurring spontaneously during normal DNA synthesis or as a result of replication on a DNA template damaged by endogenous or exogenous mutagens. In principle, changes in the frequencies of mutant cells in vivo in humans reflect changes in exposures to exogenous or endogenous DNA damaging insults, other factors being equal. It is becoming increasingly evident however, that somatic mutations in humans have a far greater range of interpretations. For example, mutations in lymphocytes provide invaluable probes for in vivo cellular and molecular processes, providing identification of clonal amplifications of these cells in autoimmune and infectious diseases, transplantation recipients, paroxysmal nocturnal hemoglobinuria (PNH), and cancer. The assay for mutations of the X-chromosomal hypoxanthine guanine phosphoribosyltransferase (HPRT) gene has gained popular acceptance for this purpose since viable mutant cells can be recovered for molecular and other analyses. Although the major application of the HPRT T cell assay remains human population monitoring, the enrichment of activated T cells in the mutant fraction in individuals with ongoing immunological processes has demonstrated the utility of surrogate selection, a method that uses somatic mutation as a surrogate marker for the in vivo T cell proliferation that underlies immunological processes to investigate clinical disorders with immunological features. Studies encompassing a wide range of clinical conditions are reviewed. Despite the historical importance of the HPRT mutation system in validating surrogate selection, there are now additional mutational and other methods for identifying immunologically active T cells. These methods are reviewed and provide insights for strategies to extend surrogate selection in future studies.

Reversing T-cell Exhaustion in Cancer: Lessons Learned from PD-1/PD-L1 Immune Checkpoint Blockade

Anti-PD-1/PD-L1 immune checkpoint blockade (ICB) therapy has revolutionized the treatment of many types of cancer over the past decade. The initial therapeutic hypothesis underlying the mechanism of anti-PD-1/PD-L1 ICB was built around the premise that it acts locally in the tumor, reversing the exhaustion of PD-1^hiCD8⁺ T cells by "releasing the brakes." However, recent studies have provided unprecedented insight into the complexity within the CD8⁺ T-cell pool in the tumor microenvironment (TME). Single-cell RNA sequencing and epigenetic profiling studies have identified novel cell surface markers, revealing heterogeneity within CD8⁺ T-cell states classified as unique. Moreover, these studies highlighted that following ICB, CD8⁺ T-cell states within and outside the TME possess a differential capacity to respond, mobilize to the TME, and seed an effective antitumor immune response. In aggregate, these recent developments have led to a reevaluation of our understanding of both the underlying mechanisms and the sites of action of ICB therapy. Here, we discuss the evidence for the reversibility of CD8⁺ T-cell exhaustion after ICB treatment and its implication for the further development of cancer immunotherapy.

Single-Cell Transcriptome Analysis Reveals RGS1 as a New Marker and Promoting Factor for T-Cell Exhaustion in Multiple Cancers

T-cell exhaustion is one of the main reasons of tumor immune escape. Using single-cell transcriptome data of CD8+ T cells in multiple cancers, we identified different cell types, in which Pre_exhaust and exhausted T cells participated in negative regulation of immune system process. By analyzing the coexpression network patterns and differentially expressed genes of Pre_exhaust, exhausted, and effector T cells, we identified 35 genes related to T-cell exhaustion, whose high GSVA scores were associated with significantly poor prognosis in various cancers. In the differentially expressed genes, RGS1 showed the greatest fold change in Pre_exhaust and exhausted cells of three cancers compared with effector T cells, and high expression of RGS1 was also associated with poor prognosis in various cancers. Additionally, RGS1 protein was upregulated significantly in tumor tissues in the immunohistochemistry verification. Furthermore, RGS1 displayed positive correlation with the 35 genes, especially highly correlated with PDCD1, CTLA4, HAVCR2, and TNFRSF9 in CD8+ T cells and cancer tissues, indicating the important roles of RGS1 in CD8+ T-cell exhaustion. Considering the GTP-hydrolysis activity of RGS1 and significantly high mRNA and protein expression in cancer tissues, we speculated that RGS1 potentially mediate the T-cell retention to lead to the persistent antigen stimulation, resulting in T-cell exhaustion. In conclusion, our findings suggest that RGS1 is a new marker and promoting factor for CD8+ T-cell exhaustion and provide theoretical basis for research and immunotherapy of exhausted cells.

Defective interferon-gamma production is common in chronic pulmonary aspergillosis

BACKGROUND

Immune defects in chronic pulmonary aspergillosis (CPA) are poorly characterised. We compared peripheral blood cytokine profiles in patients with CPA vs healthy controls and explored the relationship with disease severity.

METHODS

Interferon-gamma (IFNγ), IL-17, TNFα, IL-6, IL-12 and IL-10 were measured after in vitro stimulation of whole blood with lipopolysaccharide (LPS), phytohaemagglutinin (PHA), β-glucan, zymosan (ZYM), IL-12 or IL-18, and combinations. Clinical parameters and mortality were correlated with cytokine production.

RESULTS

Cytokine profiles were evaluated in 133 patients (57.1% male, mean age 61 years). In comparison to controls, patients with CPA had significantly reduced production of IFNγ in response to stimulation with β-glucan+IL-12 (312 vs 988 pg/ml), LPS+IL-12 (252 vs 1033 pg/ml), ZYM+IL-12 (996 vs 2347 pg/ml), and IL-18+IL-12 (7193 vs 12330 pg/ml). Age >60 (p=0.05, HR 1.71, 95%CI 1.00-2.91) and COPD (p=0.039, HR 1.69, 95%CI 1.03-2.78) were associated with worse survival, whereas high IFNγ production in response to beta-glucan+IL-12 stimulation (p=0.026, HR 0.48, 95%CI 0.25-0.92) was associated with reduced mortality.

CONCLUSION

Patients with CPA show impaired IFNγ production in peripheral blood in response to stimuli. Defective IFNγ production ability correlates with worse outcomes. Immunotherapy with IFNγ could be beneficial for patients showing impaired IFNγ production in CPA.

Is There a Role for Immunotherapy in Central Nervous System Cancers?

Glioblastoma has emerged as an immunotherapy-refractory tumor based on negative phase III studies of anti-programmed cell death-1 therapy among newly diagnosed as well as recurrent patients. In addition, although much work on vaccine and cellular approaches is ongoing, therapeutic benefit with these approaches has been underwhelming. Much scientific insight into the multitiered layers of immunosuppression exploited by glioblastoma tumors is emerging that sheds light on the explanation for the disappointing results to date and highlights possible therapeutic avenues that may offer a better likelihood of therapeutic benefit for immune-based therapies.

Proteogenomic discovery of neoantigens facilitates personalized multi-antigen targeted T cell immunotherapy for brain tumors

Neoantigen discovery in pediatric brain tumors is hampered by their low mutational burden and scant tissue availability. Here we develop a proteogenomic approach combining tumor DNA/RNA sequencing and mass spectrometry proteomics to identify tumor-restricted (neoantigen) peptides arising from multiple genomic aberrations to generate a highly target-specific, autologous, personalized T cell immunotherapy. Our data indicate that aberrant splice junctions are the primary source of neoantigens in medulloblastoma, a common pediatric brain tumor. Proteogenomically identified tumor-specific peptides are immunogenic and generate MHC II-based T cell responses. Moreover, polyclonal and polyfunctional T cells specific for tumor-specific peptides effectively eliminate tumor cells in vitro. Targeting tumor-specific antigens obviates the issue of central immune tolerance while potentially providing a safety margin favoring combination with other immune-activating therapies. These findings demonstrate the proteogenomic discovery of immunogenic tumor-specific peptides and lay the groundwork for personalized targeted T cell therapies for children with brain tumors.

Targeting tumor-associated antigens in paediatric medulloblastomas (MB) is challenging due to their low mutational burden. Here, the authors develop a sensitive proteogenomic approach to identify tumour specific neoantigens, which may enable personalised T cell immunotherapy in paediatric MB.

Anti-PD-1 Checkpoint Therapy Can Promote the Function and Survival of Regulatory T Cells

We have previously shown in a model of claudin-low breast cancer that regulatory T cells (T_regs) are increased in the tumor microenvironment (TME) and express high levels of PD-1. In mouse models and patients with triple-negative breast cancer, it is postulated that one cause for the lack of activity of anti-PD-1 therapy is the activation of PD-1-expressing T_regs in the TME. We hypothesized that the expression of PD-1 on T_regs would lead to enhanced suppressive function of T_regs and worsen antitumor immunity during PD-1 blockade. To evaluate this, we isolated T_regs from claudin-low tumors and functionally evaluated them ex vivo. We compared transcriptional profiles of T_regs isolated from tumor-bearing mice with or without anti-PD-1 therapy using RNA sequencing. We found several genes associated with survival and proliferation pathways; for example, Jun, Fos, and Bcl2 were significantly upregulated in T_regs exposed to anti-PD-1 treatment. Based on these data, we hypothesized that anti-PD-1 treatment on T_regs results in a prosurvival phenotype. Indeed, T_regs exposed to PD-1 blockade had significantly higher levels of Bcl-2 expression, and this led to increased protection from glucocorticoid-induced apoptosis. In addition, we found in vitro and in vivo that T_regs in the presence of anti-PD-1 proliferated more than control T_regs PD-1 blockade significantly increased the suppressive activity of T_regs at biologically relevant T_reg/T_naive cell ratios. Altogether, we show that this immunotherapy blockade increases proliferation, protection from apoptosis, and suppressive capabilities of T_regs, thus leading to enhanced immunosuppression in the TME.

Human prostate cancer bone metastases have an actionable immunosuppressive microenvironment

Bone metastases are devastating complications of cancer. They are particularly common in prostate cancer (PCa), represent incurable disease, and are refractory to immunotherapy. We seek to define distinct features of the bone marrow (BM) microenvironment by analyzing single cells from bone metastatic prostate tumors, involved BM, uninvolved BM, and BM from cancer-free, orthopedic patients, and healthy individuals. Metastatic PCa is associated with multifaceted immune distortion, specifically exhaustion of distinct T cell subsets, appearance of macrophages with states specific to PCa bone metastases. The chemokine CCL20 is notably overexpressed by myeloid cells, as is its cognate CCR6 receptor on T cells. Disruption of the CCL20-CCR6 axis in mice with syngeneic PCa bone metastases restores T cell reactivity and significantly prolongs animal survival. Comparative high-resolution analysis of PCa bone metastases shows a targeted approach for relieving local immunosuppression for therapeutic effect.

HLA-DRB1∗16:01 and HLA-DQB1∗05:02 Alleles Influence the Susceptibility and Progression of Cutaneous Malignant Melanoma

Background

The influence of HLA class I and II loci on the susceptibility to melanoma remains an area of intense debate. This study aimed to examine whether the HLA system was related to melanoma susceptibility and prognosis in a southern Spanish population.

Methods

In this study, HLA class I and class II genotyping were performed using polymerase chain reaction sequence-specific oligonucleotides (PCR-SSO) in 237 Spanish melanoma patients and 636 ethnically matched controls. Data were analyzed according to the clinical characteristics of the defined subgroups.

Results

Compared to the control group, DRB1∗16:01 (4% vs. 1.3%, p=0.001, Pc = 0.035, OR = 3.28) and DQB1∗05:02 (4.9% vs. 2%, p=0.001, Pc = 0.017, OR = 2.54) were positivity associated with the susceptibility to melanoma. Both DRB1∗16:01 (5.4% vs. 1.3%, p=0.001, Pc = 0.035, OR = 4.46) and DQB1∗05:02 (6.5% vs. 2%, p=0.001, Pc = 0.017, OR = 3.44) also showed a positive correlation with Breslow thickness >1.5 mm, most notably at an early age of diagnosis (≤58 years), DRB1∗16:01 (4.2% vs. 1.3%, p=0.001, Pc = 0.035, OR = 3.41) and DQB1∗05:02 (5.4% vs. 2%, p=0.002, Pc = 0.034, OR = 2.86).

Conclusion

These findings established HLA-DRB1∗16:01 and HLA-DQB1∗05:02 loci as melanoma risk factors in the southern Spanish population.

CD8+ TILs in NSCLC differentiate into TEMRA via a bifurcated trajectory: deciphering immunogenicity of tumor antigens

Background

CD8⁺ tumor-infiltrating lymphocytes (TILs) comprise phenotypically and functionally heterogeneous subpopulations. Of these, effector memory CD45RA re-expressing CD8⁺ T cells (Temra) have been discovered and characterized as the most terminally differentiated subset. However, their exact ontogeny and physiological importance in association with tumor progression remain poorly understood.

Methods

We analyzed primary tumors and peripheral blood samples from 26 patients with non-small cell lung cancer and analyzed their phenotypes and functional characteristics using flow cytometry, RNA-sequencing, and bioinformatics.

Results

We found that tumor-infiltrating Temra (tilTemra) cells largely differ from peripheral blood Temra (pTemra), with distinct transcriptomes and functional properties. Notably, although majority of the pTemra was CD27⁻CD28⁻ double-negative (DN), a large fraction of tilTemra population was CD27⁺CD28⁺ double-positive (DP), a characteristic of early-stage, less differentiated effector cells. Trajectory analysis revealed that CD8⁺ TILs undergo a divergent sequence of events for differentiation into either DP or DN tilTemra. Such a differentiation toward DP tilTemra relied on persistent expression of CD27 and CD28 and was associated with weak T cell receptor engagement. Thus, a higher proportion of DP Temra was correlated with lower immunogenicity of tumor antigens and consequently lower accumulation of CD8⁺ TILs.

Conclusions

These data suggest a complex interplay between CD8⁺ T cells and tumors and define DP Temra as a unique subset of tumor-specific CD8⁺ TILs that are produced in patients with relatively low immunogenic cancer types, predicting immunogenicity of tumor antigens and CD8⁺ TIL counts, a reliable biomarker for successful cancer immunotherapy.

A NEW MATHEMATICAL MODELING AND SUB-OPTIMAL CHEMOTHERAPY OF CANCER

The development of more accurate cancer mathematical models leads to present more realistic treatment protocols, especially in model-based treatment protocol design. Hence, a cancer mathematical model is presented by considering tumor cells, immune cells, interleukins, macrophages polarization, and chemotherapy based on biological concepts. Both local and global sensitivity analyses are done to examine the effect of changing the parameters on the final tumor population. Then, the tumor-free equilibrium points of the system are derived, and their stabilities are studied. The main target of chemotherapy is to eliminate the tumor while limiting drug toxicity. The SDRE method is used to construct a sub-optimal control strategy by using the developed nonlinear cancer model. For simulation, three patients are considered: a young patient, an old patient, and a pregnant patient. These cases have different immune system strengths. Also, three initial tumor sizes are regarded for each case. So, different treatment strategies are suggested. Eradication of tumor cells in a finite duration with a desired amount of chemo-drug is shown in the simulation results. The results confirmed that the immune system’s ability plays an important role in treatment success. It is shown that there are different treatment protocols for different patients, and the SDRE method is more flexible and effective than the others.

Pharmacologic and genetic inhibition of cholesterol esterification enzymes reduces tumour burden: A systematic review and meta-analysis of preclinical models

Cholesterol esterification proteins Sterol-O acyltransferases (SOAT) 1 and 2 are emerging prognostic markers in many cancers. These enzymes utilise fatty acids conjugated to coenzyme A to esterify cholesterol. Cholesterol esterification is tightly regulated and enables formation of lipid droplets that act as storage organelles for lipid soluble vitamins and minerals, and as cholesterol reservoirs. In cancer, this provides rapid access to cholesterol to maintain continual synthesis of the plasma membrane. In this systematic review and meta-analysis, we summarise the current depth of understanding of the role of this metabolic pathway in pan-cancer development. A systematic search of PubMed, Scopus, Web of Science, and Cochrane Library for preclinical studies identified eight studies where cholesteryl ester concentrations were compared between tumour and adjacent-normal tissue, and 24 studies where cholesterol esterification was blocked by pharmacological or genetic approaches. Tumour tissue had a significantly greater concentration of cholesteryl esters than non-tumour tissue (p < 0.0001). Pharmacological or genetic inhibition of SOAT was associated with significantly smaller tumours of all types (p ≤ 0.002). SOAT inhibition increased tumour apoptosis (p = 0.007), CD8 + lymphocyte infiltration and cytotoxicity (p ≤ 0.05), and reduced proliferation (p = 0.0003) and metastasis (p < 0.0001). Significant risk of publication bias was found and may have contributed to a 32% overestimation of the meta-analysed effect size. Avasimibe, the most frequently used SOAT inhibitor, was effective at doses equivalent to those previously reported to be safe and tolerable in humans. This work indicates that SOAT inhibition should be explored in clinical trials as an adjunct to existing anti-neoplastic agents.

Resveratrol attenuates TNBC lung metastasis by down-regulating PD-1 expression on pulmonary T cells and converting macrophages to M1 phenotype in a murine tumor model

Triple-negative breast cancer (TNBC) is an invasive breast cancer with the characteristics of easy to develop distant metastasis. Immune escape is one of the main reasons for TNBC growth and metastasis. Enhancement of T cell-mediated anti-tumor activity may benefit to inhibit tumor metastasis and improve the efficacy of cancer therapy. As a natural bioactive substance, resveratrol shows potential capability to prevent or suppress the development of a variety of cancers through direct or indirect effects, including immunoregulatory effect. However, whether resveratrol might affect lung metastasis of TNBC, and whether the effect of resveratrol might be associated with resveratrol-regulated immune responses in tumor microenvironment is still unknown. In this study, by using an experimental metastatic mouse 4 T1 tumor model, we identified that resveratrol may suppress TNBC lung metastasis by elevating local anti-tumor immunity. Indeed, an increase in the cytotoxic activity of CD8⁺T cells as well as the levels of type 1 cytokine IFN-γ and IL-2 in the lungs of resveratrol-treated tumor bearing mice were observed. The enhanced CD8⁺T cell activity and Th1 immune responses by resveratrol administration might be related to the down-regulated PD-1 expression on pulmonary CD8⁺T cells and CD4⁺T cells. Resveratrol may also convert macrophages to M1 phenotype in the lungs of tumor bearing mice. However, it seems likely resveratrol has no effect on pulmonary myeloid-derived suppressor cell activation. Our results provide an evidence that resveratrol might be a promising candidate agent for adjuvant therapy in the process of TNBC metastasis.

Inflammatory signals are sufficient to elicit TOX expression in mouse and human CD8+ T cells

T cell receptor (TCR) stimulation leads to the expression of the transcription factor thymocyte selection–associated high-mobility group box (TOX). Prolonged TCR signaling, such as encountered during chronic infections or in tumors, leads to sustained TOX expression, which is required for the induction of a state of exhaustion or dysfunction. Although CD8⁺ memory T (Tmem) cells in mice typically do not express TOX at steady state, some human Tmem cells express TOX but appear fully functional. This seeming discrepancy between mouse and human T cells has led to the speculation that TOX is differentially regulated between these species, which could complicate the interpretation of preclinical mouse model studies. We report here that, similar to TCR-mediated signals, inflammatory cytokines are also sufficient to increase TOX expression in human and mouse Tmem cells. Thus, TOX expression is controlled by the environment, which provides an explanation for the different TOX expression patterns encountered in T cells isolated from specific pathogen–free laboratory mice versus humans. Finally, we report that TOX is not necessary for cytokine-driven expression of programmed cell death 1. Overall, our data highlight that the mechanisms regulating TOX expression are conserved across species and indicate that TOX expression reflects a T cell’s activation state and does not necessarily correlate with T cell dysfunction.

Fibroblasts Influence the Efficacy, Resistance, and Future Use of Vaccines and Immunotherapy in Cancer Treatment

Tumors are composed of not only epithelial cells but also many other cell types that contribute to the tumor microenvironment (TME). Within this space, cancer-associated fibroblasts (CAFs) are a prominent cell type, and these cells are connected to an increase in tumor progression as well as alteration of the immune landscape present in and around the tumor. This is accomplished in part by their ability to alter the presence of both innate and adaptive immune cells as well as the release of various chemokines and cytokines, together leading to a more immunosuppressive TME. Furthermore, new research implicates CAFs as players in immunotherapy response in many different tumor types, typically by blunting their efficacy. Fibroblast activation protein (FAP) and transforming growth factor β (TGF-β), two major CAF proteins, are associated with the outcome of different immunotherapies and, additionally, have become new targets themselves for immune-based strategies directed at CAFs. This review will focus on CAFs and how they alter the immune landscape within tumors, how this affects response to current immunotherapy treatments, and how immune-based treatments are currently being harnessed to target the CAF population itself.

In situ injection of dual-delivery PEG based MMP-2 sensitive hydrogels for enhanced tumor penetration and chemo-immune combination therapy

Improving the deep penetration of nanoparticles and realizing the combination of chemotherapy and immunotherapy have become a promising strategy for cancer treatment. Herein, a nuclear-targeted tetrahedral DNA nanostructure (NLS-TDNs, NT) was synthesized to construct matrix metalloproteinase (MMP-2) sensitive hydrogels as delivery vehicles with co-loaded disulfide cross-linked polyethyleneimine (PSP)/nuclear-targeted tetrahedral DNA (NLS-TDNs, NT)/doxorubicin (DOX) nanoparticles (NPs) (PSP/NT/DOX NPs and PNT/DOX NPs) and an immune adjuvant imiquimod (R837) to realize a combination of chemotherapy and immunization for metastatic breast cancer. Due to the membrane-breaking ability of the PNT/DOX NPs, the nanoparticles could effectively achieve deep penetration into tumor tissues, and the in situ generation of tumor-associated antigens by PNT/DOX elicited a strong immune response in the presence of R837, achieving a chemo-immune combination therapy of breast cancer, inducing the maturation of dendritic cells (DCs) and secretion of related cytokines, such as interleukin-6 (IL-6), interleukin-12 (IL-12p70) and tumor necrosis factor (TNF-α) in vitro. The combination significantly promoted the proportions of cytotoxic T cells (CD8+ CTL) and cytotoxic T cells/regulatory T cells (CD8+ CTL/Treg) (5.52% and 11.46%, respectively) and the secretion of cytokines, which cooperatively eradicated primary tumor growth (the tumor growth inhibition (TGI) value was 78.3%) and inhibited the tumor from metastasizing effectively in vivo. Our study provided the basis for activating the antitumor immune system to realize chemo-immunotherapy and tumor metastasis therapy.

Nanoparticle-enabled innate immune stimulation activates endogenous tumor-infiltrating T cells with broad antigen specificities

Tumors are often infiltrated by T lymphocytes recognizing either self- or mutated antigens but are generally inactive, although they often show signs of prior clonal expansion. Hypothesizing that this may be due to peripheral tolerance, we formulated nanoparticles containing innate immune stimulants that we found were sufficient to activate self-specific CD8+ T cells and injected them into two different mouse tumor models, B16F10 and MC38. These nanoparticles robustly activated and/or expanded antigen-specific CD8+ tumor-infiltrating T cells, along with a decrease in regulatory CD4+ T cells and an increase in Interleukin-17 producers, resulting in significant tumor growth retardation or elimination and the establishment of immune memory in surviving mice. Furthermore, nanoparticles with modification of stimulating human T cells enabled the robust activation of endogenous T cells in patient-derived tumor organoids. These results indicate that breaking peripheral tolerance without regard to the antigen specificity creates a promising pathway for cancer immunotherapy.

Pan-cancer analysis reveals tumor-associated macrophage communication in the tumor microenvironment

BACKGROUND

Tumor-associated macrophages (TAMs) are abundant in the tumor microenvironment (TME). However, their contribution to the immunosuppressive status of the TME remains unclear.

METHODS

We integrated single-cell sequencing and transcriptome data from different tumor types to uncover the molecular features of TAMs. In vitro experiments and prospective clinical tests confirmed the results of these analysis.

RESULTS

We first detected intra- and inter-tumoral heterogeneities between TAM subpopulations and their functions, with CD86⁺ TAMs playing a crucial role in tumor progression. Next, we focused on the ligand-receptor interactions between TAMs and tumor cells in different TME phenotypes and discovered that aberrant expressions of six hub genes, including FLI1, are involved in this process. A TAM-tumor cell co-culture experiment proved that FLI1 was involved in tumor cell invasion, and FLI1 also showed a unique pattern in patients. Finally, TAMs were discovered to communicate with immune and stromal cells.

CONCLUSION

We determined the role of TAMs in the TME by focusing on their communication pattern with other TME components. Additionally, the screening of hub genes revealed potential therapeutic targets.

Role of nuclear localization in the regulation and function of T-bet and Eomes in exhausted CD8 T cells

The transcription factors T-bet and Eomesodermin (Eomes) regulate CD8 T cell exhaustion through undefined mechanisms. Here, we show that the subcellular localization of T-bet and Eomes dictate their regulatory activity in exhausted T cells (T_EXs). T_EXs had a higher ratio of nuclear Eomes:T-bet than memory T cells (T_MEMs) during chronic lymphocytic choriomeningitis virus (LCMV) infection in preclinical cancer models and in human tumors. Biochemically, T-bet and Eomes compete for the same DNA sequences, including the Pdcd1 T-box. High nuclear T-bet strongly represses Pdcd1 transcription in T_MEM, whereas low nuclear T-bet in T_EX leads to a dominant effect of Eomes that acts as a weaker repressor of Pdcd1. Blocking PD-1 signaling in T_EXs increases nuclear T-bet, restoring stronger repression of Pdcd1, and driving T-bet-associated gene expression programs of chemotaxis, homing, and activation. These data identify a mechanism whereby the T-bet-Eomes axis regulates exhaustion through their nuclear localization, providing insights into how these transcription factors regulate T_EX biology.

McLane et al. demonstrate that T-bet and Eomes expression contributes to exhaustion, but also their nuclear localization, and therefore functional activity, plays a key role. PD-1 blockade restores nuclear T-bet and promotes T cell homing and activation through direct competition with Eomes at gene promoters, such as Pdcd1.

Photosynthetic Microorganisms-Based Biophotothermal Therapy with Enhanced Immune Response

The production of oxygen by photosynthetic microorganisms (PSMs) has recently attracted interest concerning the in vivo treatment of multiple diseases for their photosynthetic oxygen production in vivo, since PSMs have good biological safety. Here, the first evidence that PSMs can be used as a photothermal source to perform biophotothermal therapy (bio-PTT) is provided. In vitro and in vivo experiments proved that PSMs can generate heat for the direct elimination of tumors and release a series of pathogen-associated molecular patterns and adjuvants for immune stimulation under light irradiation. Bio-PTT enabled a local tumor inhibition rate exceeding 90% and an abscopal tumor inhibition rate exceeding 75%. This strategy also produced a stronger antitumor immune memory effect to prevent tumor recurrence. The bio-PTT strategy provides a novel direction for photothermal therapy as it simultaneously produces local and abscopal antitumor effects.

Metabolic barriers to cancer immunotherapy

Several non-redundant features of the tumour microenvironment facilitate immunosuppression and limit anticancer immune responses. These include physical barriers to immune infiltration, the recruitment of suppressive immune cells and the upregulation of ligands on tumour cells that bind to inhibitory receptors on immune cells. Recent insights into the importance of the metabolic restrictions imposed by the tumour microenvironment on antitumour T cells have begun to inform immunotherapeutic anticancer strategies. Therapeutics that target metabolic restrictions, such as low glucose levels, a low pH, hypoxia and the generation of suppressive metabolites, have shown promise as combination therapies for different types of cancer. In this Review, we discuss the metabolic aspects of the antitumour T cell response in the context of immune checkpoint blockade, adoptive cell therapy and treatment with oncolytic viruses, and discuss emerging combination strategies.

The tumor microenvironment shapes the molecular characteristics of exhausted CD8+ T cells

The persistent antigen stimulation during chronic infections and cancer results in CD8⁺ T cell exhaustion. The exhausted T (Tex) cells within the tumor microenvironment (TME) are characterized by increased expression of multiple co-inhibitory receptors simultaneously, progressive loss of effector function, poor proliferation and self-renewal capacity, and dysregulated metabolic activity. Emerging insights into molecular mechanisms underlying T cell exhaustion have proposed potential approaches to improve the efficacy of cancer immunotherapy via restoring the effector function of Tex cells. In this review, we summarize the fundamental characteristics (e.g., inhibitory receptors and transcriptional factors) regarding Tex cell differentiation and discuss in particular how those exhaustion features are acquired and shaped by key factors within the TME. Additionally, we discuss the progress and limitations of current cancer immunotherapeutic strategies targeting Tex cells in clinical setting.

Tgf-β1 produced by activated CD4(+) T Cells Antagonizes T Cell Surveillance of Tumor Development

TGFβ1 is a regulatory cytokine with a crucial function in the control of T cell tolerance to tumors. Our recent study revealed that T cell-produced TGFβ1 is essential for inhibiting cytotoxic T cell responses to tumors. However, the exact TGFβ1-producing T cell subset required for tumor immune evasion remains unknown. Here we showed that deletion of TGFβ1 from CD8⁺ T cells or Foxp3⁺ regulatory T (Treg) cells did not protect mice against transplanted tumors. However, absence of TGFβ1 produced by activated CD4⁺ T cells and Treg cells inhibited tumor growth, and protected mice from spontaneous prostate cancer. These findings suggest that TGFβ1 produced by activated CD4⁺ T cells is a necessary requirement for tumor evasion from immunosurveillance.

Exhausted CD8+T Cells in the Tumor Immune Microenvironment: New Pathways to Therapy

Tumor-specific CD8⁺T cells are exposed to persistent antigenic stimulation which induces a dysfunctional state called "exhaustion." Though functioning to limit damage caused by immune response, T cell exhaustion leads to attenuated effector function whereby cytotoxic CD8⁺T cells fail to control tumor progression in the late stage. This pathway is a dynamic process from activation to "progenitor exhaustion" through to "terminally exhaustion" with distinct properties. With the rapid development of immunotherapy via enhancing T cell function, new studies are dissecting the mechanisms and identifying specific biomarkers of dynamic differentiation during the process of exhaustion. Further, although immune checkpoint inhibitors (ICIs) have achieved great success in clinical practice, most patients still show limited efficacy to ICIs. The expansion and differentiation of progenitor exhausted T cells explained the success of ICIs while the depletion of the progenitor T cell pool and the transient effector function of terminally exhausted T cells accounted for the failure of immune monotherapy in the context of exorbitant tumor burden. Thus, combination strategies are urgent to be utilized based on the reduction of tumor burden or the expansion of the progenitor T cell pool. In this review, we aim to introduce the concept of homeostasis of the activated and exhausted status of CD8⁺T cells in the tumor immune microenvironment, and present recent findings on dynamic differentiation process during T cell exhaustion and the implications for combination strategies in immune therapy.

Inefficient boosting of antitumor CD8(+) T cells by dendritic-cell vaccines is rescued by restricting T-cell cytotoxic functions

Dendritic cells (DCs) are powerful activators of primary and secondary immune responses and have promising activity as anticancer vaccines. However, various populations of immune cells, including natural killer cells, regulatory T cells and especially cytotoxic T lymphocytes (CTLs), can inhibit DC function through cytotoxic clearance. Spontaneous tumor-specific CTL responses are frequently observed in patients before immunotherapy, and it is unclear how such pre-existing responses may affect DC vaccines. We used an adoptive transfer model to show that DC vaccination fail to induce the expansion of pre-existing CTLs or increase their production of interferon γ (IFNγ). The expansion and effector differentiation of naïve host CD8⁺ T cells was also suppressed in the presence of CTLs of the same specificity. Suppression was caused by the cytotoxic functions of the adoptively transferred CTLs, as perforin-deficient CTLs could respond to DC vaccination by expanding and increasing IFNγ production. Proliferation and effector differentiation of host CD8⁺ T cells as well as resistance to tumor challenge were also significantly increased. Expression of perforin by antitumor CTLs was critical in regulating the survival of vaccine DCs, while FAS/FASL and TRAIL/DR5 had a significant, but comparatively smaller, effect. We conclude that perforin-expressing CTLs can suppress the activity of DC-based vaccines and prevent the expansion of naïve and memory CD8⁺ T cells as well as antitumor immune responses. We suggest that, paradoxically, temporarily blocking the cytotoxic functions of CTLs at the time of DC vaccination should result in improved vaccine efficiency and enhanced antitumor immunity.