CD4 cells can be more efficient at tumor rejection than CD8 cells

Intratumoral immune triads are required for immunotherapy-mediated elimination of solid tumors

Tumor-specific CD8+ T cells are frequently dysfunctional and unable to halt tumor growth. We investigated whether tumor-specific CD4+ T cells can be enlisted to overcome CD8+ T cell dysfunction within tumors. We find that the spatial positioning and interactions of CD8+ and CD4+ T cells, but not their numbers, dictate anti-tumor responses in the context of adoptive T cell therapy as well as immune checkpoint blockade (ICB): CD4+ T cells must engage with CD8+ T cells on the same dendritic cell during the effector phase, forming a three-cell-type cluster (triad) to license CD8+ T cell cytotoxicity and cancer cell elimination. When intratumoral triad formation is disrupted, tumors progress despite equal numbers of tumor-specific CD8+ and CD4+ T cells. In patients with pleural mesothelioma treated with ICB, triads are associated with clinical responses. Thus, CD4+ T cells and triads are required for CD8+ T cell cytotoxicity during the effector phase and tumor elimination.

Evaluation of the activity of cardiac glycosides on RORγ and RORγT nuclear receptors

Cardiac glycosides, derived from plants and animals, have been recognized since ancient times. These substances hinder the function of the sodium-potassium pump within eukaryotic cells. Many reports have shown that these compounds influence the activity of nuclear receptors. Thus, we assessed the effects of various cardiac glycosides at nontoxic concentrations on RORγ and RORγT. RORγT is a crucial protein involved in the differentiation of Th17 lymphocytes. Sixteen analyzed cardiac glycosides exhibited varying toxicities in HepG2 cells, all of which demonstrated agonistic effects on RORγ, as confirmed in the RORγ-HepG2 reporter cell line. The overexpression of both the RORγ and RORγT isoforms intensified the effects of these compounds. Additionally, these glycosides induced the expression of G6PC, a gene regulated by RORγ, in HepG2 cells. Subsequently, the effects of two endogenous cardiac glycosides (marinobufagenin and ouabain) and the three most potent glycosides (bufalin, oleandrin, and telecinobufagenin) were evaluated in Th17 primary lymphocytes. All of these compounds increased the expression of the IL17A, IL17F, IFNG, and CXCL10 genes, but they exhibited varying effects on GZMB and CCL20 expression. Molecular docking analysis revealed the robust binding affinity of cardiac glycosides for the ligand binding domain of the RORγ/RORγT receptors. Thus, we demonstrated that at nontoxic concentrations, cardiac glycosides have agonistic effects on RORγ/RORγT nuclear receptors, augmenting their activity. This potential can be harnessed to modulate the phenotype of IL17-expressing cells (e.g., Th17 or Tc17 lymphocytes) in adoptive therapy for combating various types of cancer.

Pharmacodynamic changes in tumor and immune cells drive iberdomide's clinical mechanisms of activity in relapsed and refractory multiple myeloma

Iberdomide is a next-generation cereblon (CRBN)-modulating agent in the clinical development in multiple myeloma (MM). The analysis of biomarker samples from relapsed/refractory patients enrolled in CC-220-MM-001 (ClinicalTrials.gov: NCT02773030), a phase 1/2 study, shows that iberdomide treatment induces significant target substrate degradation in tumors, including in immunomodulatory agent (IMiD)-refractory patients or those with low CRBN levels. Additionally, some patients with CRBN genetic dysregulation who responded to iberdomide have a similar median progression-free survival (PFS) (10.9 months) and duration of response (DOR) (9.5 months) to those without CRBN dysregulation (11.2 month PFS, 9.4 month DOR). Iberdomide treatment promotes a cyclical pattern of immune stimulation without causing exhaustion, inducing a functional shift in T cells toward an activated/effector memory phenotype, including in triple-class refractory patients and those receiving IMiDs as a last line of therapy. This analysis demonstrates that iberdomide's clinical mechanisms of action are driven by both its cell-autonomous effects overcoming CRBN dysregulation in MM cells, and potent immune stimulation that augments anti-tumor immunity.

VISTA checkpoint inhibition by pH-selective antibody SNS-101 with optimized safety and pharmacokinetic profiles enhances PD-1 response

VISTA, an inhibitory myeloid-T-cell checkpoint, holds promise as a target for cancer immunotherapy. However, its effective targeting has been impeded by issues such as rapid clearance and cytokine release syndrome observed with previous VISTA antibodies. Here we demonstrate that SNS-101, a newly developed pH-selective VISTA antibody, addresses these challenges. Structural and biochemical analyses confirmed the pH-selectivity and unique epitope targeted by SNS-101. These properties confer favorable pharmacokinetic and safety profiles on SNS-101. In syngeneic tumor models utilizing human VISTA knock-in mice, SNS-101 shows in vivo efficacy when combined with a PD-1 inhibitor, modulates cytokine and chemokine signaling, and alters the tumor microenvironment. In summary, SNS-101, currently in Phase I clinical trials, emerges as a promising therapeutic biologic for a wide range of patients whose cancer is refractory to current immunotherapy regimens.

Challenges in developing personalized neoantigen cancer vaccines

The recent success of cancer immunotherapies has highlighted the benefit of harnessing the immune system for cancer treatment. Vaccines have a long history of promoting immunity to pathogens and, consequently, vaccines targeting cancer neoantigens have been championed as a tool to direct and amplify immune responses against tumours while sparing healthy tissue. In recent years, extensive preclinical research and more than one hundred clinical trials have tested different strategies of neoantigen discovery and vaccine formulations. However, despite the enthusiasm for neoantigen vaccines, proof of unequivocal efficacy has remained beyond reach for the majority of clinical trials. In this Review, we focus on the key obstacles pertaining to vaccine design and tumour environment that remain to be overcome in order to unleash the true potential of neoantigen vaccines in cancer therapy.

p21 Prevents the Exhaustion of CD4+ T Cells Within the Antitumor Immune Response Against Colorectal Cancer

BACKGROUND & AIMS

T cells are crucial for the antitumor response against colorectal cancer (CRC). T-cell reactivity to CRC is nevertheless limited by T-cell exhaustion. However, molecular mechanisms regulating T-cell exhaustion are only poorly understood.

METHODS

We investigated the functional role of cyclin-dependent kinase 1a (Cdkn1a or p21) in cluster of differentiation (CD) 4+ T cells using murine CRC models. Furthermore, we evaluated the expression of p21 in patients with stage I to IV CRC. In vitro coculture models were used to understand the effector function of p21-deficient CD4+ T cells.

RESULTS

We observed that the activation of cell cycle regulator p21 is crucial for CD4+ T-cell cytotoxic function and that p21 deficiency in type 1 helper T cells (Th1) leads to increased tumor growth in murine CRC. Similarly, low p21 expression in CD4+ T cells infiltrated into tumors of CRC patients is associated with reduced cancer-related survival. In mouse models of CRC, p21-deficient Th1 cells show signs of exhaustion, where an accumulation of effector/effector memory T cells and CD27/CD28 loss are predominant. Immune reconstitution of tumor-bearing Rag1-/- mice using ex vivo-treated p21-deficient T cells with palbociclib, an inhibitor of cyclin-dependent kinase 4/6, restored cytotoxic function and prevented exhaustion of p21-deficient CD4+ T cells as a possible concept for future immunotherapy of human disease.

CONCLUSIONS

Our data reveal the importance of p21 in controlling the cell cycle and preventing exhaustion of Th1 cells. Furthermore, we unveil the therapeutic potential of cyclin-dependent kinase inhibitors such as palbociclib to reduce T-cell exhaustion for future treatment of patients with colorectal cancer.

Recombinant Newcastle disease viruses expressing immunological checkpoint inhibitors induce a pro-inflammatory state and enhance tumor-specific immune responses in two murine models of cancer

Introduction

Tumor microenvironments are immunosuppressive due to progressive accumulation of mutations in cancer cells that can drive expression of a range of inhibitory ligands and cytokines, and recruitment of immunomodulatory cells, including myeloid-derived suppressor cells (MDSC), tumor-associated macrophages, and regulatory T cells (Tregs).

Methods

To reverse this immunosuppression, we engineered mesogenic Newcastle disease virus (NDV) to express immunological checkpoint inhibitors anti-cytotoxic T lymphocyte antigen-4 and soluble programmed death protein-1.

Results

Intratumoral administration of recombinant NDV (rNDV) to mice bearing intradermal B16-F10 melanomas or subcutaneous CT26LacZ colon carcinomas led to significant changes in the tumor-infiltrating lymphocyte profiles. Vectorizing immunological checkpoint inhibitors in NDV increased activation of intratumoral natural killer cells and cytotoxic T cells and decreased Tregs and MDSCs, suggesting induction of a pro-inflammatory state with greater infiltration of activated CD8+ T cells. These notable changes translated to higher ratios of activated effector/suppressor tumor-infiltrating lymphocytes in both cancer models, which is a promising prognostic marker. Whereas all rNDV-treated groups showed evidence of tumor regression and increased survival in the CT26LacZ and B16-F10, only treatment with NDV expressing immunological checkpoint blockades led to complete responses compared to tumors treated with NDV only.

Discussion

These data demonstrated that NDV expressing immunological checkpoint inhibitors could reverse the immunosuppressive state of tumor microenvironments and enhance tumor-specific T cell responses.

CD4+ T cell immunity against cutaneous melanoma encompasses multifaceted MHC II-dependent responses

Whereas CD4+ T cells conventionally mediate antitumor immunity by providing help to CD8+ T cells, recent clinical studies have implied an important role for cytotoxic CD4+ T cells in cancer immunity. Using an orthotopic melanoma model, we provide a detailed account of antitumoral CD4+ T cell responses and their regulation by major histocompatibility complex class II (MHC II) in the skin. Intravital imaging revealed prominent interactions of CD4+ T cells with tumor debris-laden MHC II+ host antigen-presenting cells that accumulated around tumor cell nests, although direct recognition of MHC II+ melanoma cells alone could also promote CD4+ T cell control. CD4+ T cells stably suppressed or eradicated tumors even in the absence of other lymphocytes by using tumor necrosis factor-α and Fas ligand (FasL) but not perforin-mediated cytotoxicity. Interferon-γ was critical for protection, acting both directly on melanoma cells and via induction of nitric oxide synthase in myeloid cells. Our results illustrate multifaceted and context-specific aspects of MHC II-dependent CD4+ T cell immunity against cutaneous melanoma, emphasizing modulation of this axis as a potential avenue for immunotherapies.

RORγT agonists as immune modulators in anticancer therapy

RORγT is a transcription factor that directs the development of Th17 lymphocytes and other IL-17-expressing cells (e.g., Tc17 and ILC3 cells). These cells are involved in the body's defense against pathogenic bacteria and fungi, but they also participate in maintaining the proinflammatory environment in some autoimmune diseases and play a role in the immune system's response to cancer. Similar to other members of the nuclear receptor superfamily, the activity of RORγT is regulated by low-molecular-weight ligands. Therefore, extensive efforts have been dedicated to identifying inverse agonists that diminish the activity of this receptor and subsequently inhibit the development of autoimmune diseases. Unfortunately, in the pursuit of an ideal inverse agonist, the development of agonists has been overlooked. It is important to remember that these types of compounds, by stimulating lymphocytes expressing RORγT (Th17 and Tc17), can enhance the immune system's response to tumors. In this review, we present recent advancements in the biology of RORγT agonists and their potential application in anticancer therapy.

Low Pretreatment CD4+:CD8+ T Cell Ratios and CD39+CD73+CD19+ B Cell Proportions Are Associated with Improved Relapse-Free Survival in Head and Neck Squamous Cell Carcinoma

The ectonucleotidases CD39 and CD73 are present on immune cells and play important roles in cancer progression by suppressing antitumour immunity. As such, CD39 and CD73 on peripheral blood mononuclear cells (PBMCs) are emerging as potential biomarkers to predict disease outcomes and treatment responses in cancer patients. This study aimed to examine T and B cells, including CD39 and CD73 expressing subsets, by flow cytometry in PBMCs from 28 patients with head and neck squamous cell carcinoma (HNSCC) and to assess the correlation with the treatment modality, human papillomavirus (HPV) status, and relapse-free survival (RFS). The PBMCs were examined pre-, mid-, and post-radiotherapy with concurrent cisplatin chemotherapy or anti-epidermal growth factor receptor antibody (cetuximab) therapy. Combination radiotherapy caused changes to T and B cell populations, including CD39 and CD73 expressing subsets, but no such differences were observed between concurrent chemotherapy and cetuximab. Pretreatment PBMCs from HPV+ patients contained increased proportions of CD39-CD73-CD4+ T cells and reduced proportions of CD39-/+CD73+CD4+ T cells compared to the equivalent cells from HPV- patients. Notably, the pretreatment CD4+:CD8+ T cell ratios and CD39+CD73+CD19+ B cell proportions below the respective cohort medians corresponded with an improved RFS. Collectively, this study supports the notion that CD39 and CD73 may contribute to disease outcomes in HNSCC patients and may assist as biomarkers, either alone or as part of immune signatures, in HNSCC. Further studies of CD39 and CD73 on PBMCs from larger cohorts of HNSCC patients are warranted.

Murine cytotoxic CD4+ T cells in the tumor microenvironment are at a hyper-maturation stage of Th1 CD4+ T cells sustained by IL-12

The roles of tumor-infiltrating CD4+Foxp3- T cells are not well characterized due to their plasticity of differentiation, and varying levels of activation or exhaustion. To further clarify this issue, we used a model featuring subcutaneous murine colon cancer and analyzed the dynamic changes of phenotype and function of the tumor-associated CD4+ T-cell response. We found that, even at a late stage of tumor growth, the tumor-infiltrating CD4+Foxp3- T cells still expressed effector molecules, inflammatory cytokines and molecules that are expressed at reduced levels in exhausted cells. We used microarrays to examine the gene-expression profiles of different subsets of CD4+ T cells and revealed that the tumor-infiltrating CD4+Foxp3- T cells expressed not only type 1 helper (Th1) cytokines, but also cytolytic granules such as those encoded by Gzmb and Prf1. In contrast to CD4+ regulatory T cells, these cells exclusively co-expressed natural killer receptor markers and cytolytic molecules as shown by flow-cytometry studies. We used an ex vivo killing assay and proved that they could directly suppress CT26 tumor cells through granzyme B and perforin. Finally, we used pathway analysis and ex vivo stimulation to confirm that the CD4+Foxp3- T cells expressed higher levels of IL12rb1 genes and were activated by the IL-12/IL-27 pathway. In conclusion, this work finds that, in late-stage tumors, the tumor-infiltrating lymphocyte population of CD4+ cells harbored a sustained, hyper-maturated Th1 status with cytotoxic function supported by IL-12.

Advanced Oxidation Nanoprocessing Boosts Immunogenicity of Whole Tumor Cells

Whole tumor cells expressing a wide array of tumor antigens are considered as a highly promising source of antigens for cancer vaccines. However, simultaneously preserving the antigen diversity, improving immunogenicity, and eliminating the potential tumorigenic risk of whole tumor cells are highly challenging. Inspired by the recent progress in sulfate radical-based environmental technology, herein, an advanced oxidation nanoprocessing (AONP) strategy is developed for boosting the immunogenicity of whole tumor cells. The AONP is based on the activation of peroxymonosulfate by ZIF-67 nanocatalysts to produce SO4 -∙ radicals continuously, leading to sustained oxidative damage to tumor cells and consequently extensive cell death. Importantly, AONP causes immunogenic apoptosis as evidenced by the release of a series of characteristic damage associated molecular patterns and at the same time maintains the integrity of cancer cells, which is critical to preserve the cellular components and thus maximize the diversity of antigens. Finally, the immunogenicity of AONP-treated whole tumor cells is evaluated in a prophylactic vaccination model, demonstrating significantly delayed tumor growth and increased survival rate of live tumor-cell-challenged mice. It is expected that the developed AONP strategy would pave the way to develop effective personalized whole tumor cell vaccines in future.

CD4 T cells in chronic myeloid leukemia present MHC class II-dependent and IFN-γ-dependent cytotoxic capacity

At present, many therapeutic schemes have been used to improve the prognosis of patients with chronic myeloid leukemia (CML), but response remains poor in a small group of patients. CD4 T cell-mediated cytotoxicity has been found in various autoimmune diseases. This study analyzed the characteristics of CD4 T cell mediated cytotoxicity in CML patients and healthy people. The cytotoxicity of CD4 T cells was tested in using two CML cell lines, including the MHC class II-deficient K562 cells and the MHC class II-expressing KU812 cells. CD4 T cell-mediated lysis was minimal in K562 cells but was much higher in KU812 cells. In CML patients, the level of CD4 T cell-mediated lysis was limited to a certain level. Interestingly, pre-treating KU812 cells with IFN-γ could significantly elevate the expression of MHC class II and elevate the level of CD4 T cell-mediated lysis. Overall, these data indicated CD4 T cells could become a potential candidate for cytotoxic elimination of CML cells.

Intratumoral immune triads are required for adoptive T cell therapy-mediated elimination of solid tumors

Tumor-reactive CD8 T cells found in cancer patients are frequently dysfunctional, unable to halt tumor growth. Adoptive T cell transfer (ACT), the administration of large numbers of in vitro-generated cytolytic tumor-reactive CD8 T cells, is an important cancer immune therapy being pursued. However, a limitation of ACT is that transferred CD8 T cells often rapidly lose effector function, and despite exciting results in certain malignancies, few ACT clinical trials have shown responses in solid tumors. Here, we developed preclinical cancer mouse models to investigate if and how tumor-specific CD4 T cells can be enlisted to overcome CD8 T cell dysfunction in the setting of ACT. In situ confocal microscopy of color-coded cancer cells, tumor-specific CD8 and CD4 T cells, and antigen presenting cells (APC), combined with functional studies, revealed that the spatial positioning and interactions of CD8 and CD4 T cells, but not their numbers, dictates ACT efficacy and anti-tumor responses. We uncover a new role of antigen-specific CD4 T cells in addition to the known requirement for CD4 T cells during priming/activation of naïve CD8 T cells. CD4 T cells must co-engage with CD8 T cells and APC cross-presenting CD8- and CD4-tumor antigens during the effector phase, forming a three-cell-cluster (triad), to license CD8 T cell cytotoxicity and mediate cancer cell elimination. Triad formation transcriptionally and epigenetically reprogram CD8 T cells, prevent T cell dysfunction/exhaustion, and ultimately lead to the elimination of large established tumors and confer long-term protection from recurrence. When intratumoral triad formation was disrupted, adoptively transferred CD8 T cells could not be reprogrammed, and tumors progressed despite equal numbers of tumor-infiltrating CD8 and CD4 T cells. Strikingly, the formation of CD4 T cell::CD8 T cell::APC triads in tumors of patients with lung cancers treated with immune checkpoint blockade was associated with clinical responses, but not CD4::APC dyads or overall numbers of CD8 or CD4 T cells, demonstrating the importance of triads in non-ACT settings in humans. Our work uncovers intratumoral triads as a key requirement for anti-tumor immunity and a new role for CD4 T cells in CD8 T cell cytotoxicity and cancer cell eradication.

A novel signature incorporating lipid metabolism- and immune-related genes to predict the prognosis and immune landscape in hepatocellular carcinoma

Background

Liver hepatocellular carcinoma (LIHC) is a highly malignant tumor with high metastasis and recurrence rates. Due to the relation between lipid metabolism and the tumor immune microenvironment is constantly being elucidated, this work is carried out to produce a new prognostic gene signature that incorporates immune profiles and lipid metabolism of LIHC patients.

Methods

We used the "DEseq2" R package and the "Venn" R package to identify differentially expressed genes related to lipid metabolism (LRDGs) in LIHC. Additionally, we performed unsupervised clustering of LIHC patients based on LRDGs to identify their subgroups and immuno-infiltration and Gene Ontology (GO) enrichment analysis on the subgroups. Next, we employed multivariate, LASSO and univariate Cox regression analyses to determine variables and to create a prognostic profile on the basis of immune- and lipid metabolism-related differential genes (IRDGs and LRDGs). We separated patients into low- and high-risk groups in accordance with the best cut-off value of risk score. We conducted Decision Curve Analysis (DCA), Receiver Operating Characteristic curve analysis as a function of time as well as Survival Analysis to evaluate this signature's prognostic value. We incorporated the clinical characteristics of patients into the risk model to obtain a nomogram prognostic model. GEO14520 and ICGC-LIRI JP datasets were employed to externally confirm the accuracy and robustness of signature. The gene set variation analysis (GSVA) and gene set enrichment analysis (GSEA) were applied for investigating the underlying mechanisms. Immune infiltration analysis was implemented to examine the differences in immune between both risk groups. Single-cell RNA sequencing (scRNA-SEQ) was utilized to characterize the genes that were involved in the distribution of signature and expression characteristics of different LIHC cell types. The patients' sensitivity in both risk groups to commonly used chemotherapeutic agents and semi-inhibitory concentrations (IC50) of the drugs was assessed using the GDSC database. On the basis of the differentially expressed genes (DEGs) in the two groups, the CMAP database was adopted for the prediction of potential small-molecule compounds. Small-molecule compounds were molecularly docked with prognostic markers. Lastly, we investigated the prognostic gene expression levels in normal and LIHC tissues with immunohistochemistry (IHC) and quantitative reverse transcription polymerase chain reaction(qRT-PCR).

Results

We built and verified a prognostic signature with seven genes that incorporated immune profiles and lipid metabolism. Patients were classified as low- and high-risk groups depending on their prognostic profiles. The overall survival (OS) was markedly lower in the high-risk group as compared to low-risk group. Time-dependent ROC curves more precisely predicted patients' survival at 1, 3 and 5 years; the area under the ROC curve was 0.81 (1 year), 0.75 (3 years) and 0.77 (5 years). The DCA curves showed the value of the prognostic genes in this signature for clinical applications. We included the patients' clinical characteristics in the risk model for both multivariate and univariate Cox regression analyses, and the findings revealed that the risk model represents an independent factor that influences OS in LIHC patients. With immune analysis, GSVA and GSEA, we identified that there are remarkable differences between the two risk groups in immune pathways, lipid metabolism, tumor development, immune cell infiltration and immune microenvironment, response to immunotherapy, and sensitivity to chemotherapy. Moreover, those with higher risk scores presented greater sensitivity to the chemotherapeutic agents. Experiments in vitro further elucidated the roles of SPP1 and FLT3 in the LIHC immune microenvironment. Furthermore, four small-molecule drugs that could target LIHC were screened. In vitro qRT-PCR , IHC revealed that the SPP1,KIF18A expressions were raised in LIHC in tumor samples, whereas FLT3,SOCS2 showed the opposite trend.

Conclusions

We developed and verified a new signature comprising immune- and lipid metabolism-associated markers and to assess the prognosis and the immune status of LIHC patients. This signature can be applied to survival prediction, individualized chemotherapy, and immunotherapeutic guidance for patients with liver cancer. This study also provides potential targeted therapeutics and novel ideas for the immune evasion and progression of LIHC.

Both CD8 and CD4 T cells contribute to immunosurveillance preventing the development of neoantigen-expressing autochthonous sarcomas

The adaptive immune system plays an essential anti-tumor role through immunosurveillance and response to immunotherapies. Characterizing phenotypic features and mechanisms of dysfunction of tumor-specific T cell populations may uncover novel immunotherapeutic targets and biomarkers of response. To study tumor-specific T cell responses in vivo, a tumor model must express a known neoantigen. While transplant models with known neoantigen expression are widely available, autochthonous tumor models in which the tumor coevolves with the immune system are limited. In this study, we combined CRISPR/Cas9 and sleeping beauty transposase technology to develop an autochthonous orthotopic murine sarcoma model with oncogenic KrasG12D, functionally impaired p53, and expression of known MHCI and MHCII sarcoma neoantigens. Using MHC tetramer flow cytometry, we identified a tumor-specific immune response in the peripheral blood as early as 10 days after tumor induction leading to tumor clearance. Tumors developed at high penetrance after co-depletion of CD8 and CD4 T cells, but depletion of either CD8 or CD4 T cells alone was insufficient to permit tumor growth. These results suggest that CD8 and CD4 T cells can independently contribute to immunosurveillance leading to clearance of sarcomas expressing MHCI and MHCII neoantigens.

Intratumor childhood vaccine-specific CD4+ T-cell recall coordinates antitumor CD8+ T cells and eosinophils

BACKGROUND

Antitumor mechanisms of CD4⁺ T cells remain crudely defined, and means to effectively harness CD4⁺ T-cell help for cancer immunotherapy are lacking. Pre-existing memory CD4⁺ T cells hold potential to be leveraged for this purpose. Moreover, the role of pre-existing immunity in virotherapy, particularly recombinant poliovirus immunotherapy where childhood polio vaccine specific immunity is ubiquitous, remains unclear. Here we tested the hypothesis that childhood vaccine-specific memory T cells mediate antitumor immunotherapy and contribute to the antitumor efficacy of polio virotherapy.

METHODS

The impact of polio immunization on polio virotherapy, and the antitumor effects of polio and tetanus recall were tested in syngeneic murine melanoma and breast cancer models. CD8⁺ T-cell and B-cell knockout, CD4⁺ T-cell depletion, CD4⁺ T-cell adoptive transfer, CD40L blockade, assessments of antitumor T-cell immunity, and eosinophil depletion defined antitumor mechanisms of recall antigens. Pan-cancer transcriptome data sets and polio virotherapy clinical trial correlates were used to assess the relevance of these findings in humans.

RESULTS

Prior vaccination against poliovirus substantially bolstered the antitumor efficacy of polio virotherapy in mice, and intratumor recall of poliovirus or tetanus immunity delayed tumor growth. Intratumor recall antigens augmented antitumor T-cell function, caused marked tumor infiltration of type 2 innate lymphoid cells and eosinophils, and decreased proportions of regulatory T cells (Tregs). Antitumor effects of recall antigens were mediated by CD4⁺ T cells, limited by B cells, independent of CD40L, and dependent on eosinophils and CD8⁺ T cells. An inverse relationship between eosinophil and Treg signatures was observed across The Cancer Genome Atlas (TCGA) cancer types, and eosinophil depletion prevented Treg reductions after polio recall. Pretreatment polio neutralizing antibody titers were higher in patients living longer, and eosinophil levels increased in the majority of patients, after polio virotherapy.

CONCLUSION

Pre-existing anti-polio immunity contributes to the antitumor efficacy of polio virotherapy. This work defines cancer immunotherapy potential of childhood vaccines, reveals their utility to engage CD4⁺ T-cell help for antitumor CD8⁺ T cells, and implicates eosinophils as antitumor effectors of CD4⁺ T cells.

Exploring the Interactions of Oncolytic Viral Therapy and Immunotherapy of Anti-CTLA-4 for Malignant Melanoma Mice Model

Oncolytic ability to direct target and lyse tumor cells makes oncolytic virus therapy (OVT) a promising approach to treating cancer. Despite its therapeutic potential to stimulate anti-tumor immune responses, it also has immunosuppressive effects. The efficacy of OVTs as monotherapies can be enhanced by appropriate adjuvant therapy such as anti-CTLA-4. In this paper, we propose a mathematical model to explore the interactions of combined therapy of oncolytic viruses and a checkpoint inhibitor, anti-CTLA-4. The model incorporates both the susceptible and infected tumor populations, natural killer cell population, virus population, tumor-specific immune populations, virus-specific immune populations, tumor suppressive cytokine IFN-g, and the effect of immune checkpoint inhibitor CTLA-4. In particular, we distinguish the tumor-specific immune abilities of CD8⁺ T, NK cells, and CD4⁺ T cells and describe the destructive ability of cytokine on tumor cells as well as the inhibitory capacity of CTLA-4 on various components. Our model is validated through the experimental results. We also investigate various dosing strategies to improve treatment outcomes. Our study reveals that tumor killing rate by cytokines, cytokine decay rate, and tumor growth rate play important roles on both the OVT monotherapy and the combination therapy. Moreover, parameters related to CD8⁺ T cell killing have a large impact on treatment outcomes with OVT alone, whereas parameters associated with IFN-g strongly influence treatment responses for the combined therapy. We also found that virus killing by NK cells may halt the desired spread of OVs and enhance the probability of tumor escape during the treatment. Our study reveals that it is the activation of host anti-tumor immune system responses rather than its direct destruction of the tumor cells plays a major biological function of the combined therapy.

Selective STING stimulation in dendritic cells primes antitumor T cell responses

T cells that recognize tumor antigens are crucial for mounting antitumor immune responses. Induction of antitumor T cells in immunogenic tumors depends on STING, the intracellular innate immune receptor for cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) and related cyclic dinucleotides (CDNs). However, the optimal way to leverage STING activation in nonimmunogenic tumors is still unclear. Here, we show that cGAMP delivery by intratumoral injection of virus-like particles (cGAMP-VLP) led to differentiation of circulating tumor-specific T cells, decreased tumor regulatory T cells (T_regs), and antitumoral responses that synergized with PD1 blockade. By contrast, intratumoral injection of the synthetic CDN ADU-S100 led to tumor necrosis and systemic T cell activation but simultaneously depleted immune cells from injected tumors and induced minimal priming of circulating tumor-specific T cells. The antitumor effects of cGAMP-VLP required type 1 conventional dendritic cells (cDC1), whereas ADU-S100 eliminated cDC1 from injected tumors. cGAMP-VLP preferentially targeted STING in dendritic cells at a 1000-fold smaller dose than ADU-S100. Subcutaneous administration of cGAMP-VLP showed synergy when combined with PD1 blockade or a tumor T_reg-depleting antibody to elicit systemic tumor-specific T cells and antitumor activity, leading to complete and durable tumor eradication in the case of tumor T_reg depletion. These findings show that cell targeting of STING stimulation shapes the antitumor T cell response and identify a therapeutic strategy to enhance T cell-targeted immunotherapy.

Mass Cytometry Reveals Classical Monocytes, NK Cells, and ICOS+ CD4+ T Cells Associated with Pembrolizumab Efficacy in Patients with Lung Cancer

PURPOSE

Immune checkpoint inhibitors (ICI) have revolutionized the treatment of non-small cell lung cancer (NSCLC), but predictive biomarkers of their efficacy are imperfect. The primary objective is to evaluate circulating immune predictors of pembrolizumab efficacy in patients with advanced NSCLC.

EXPERIMENTAL DESIGN

We used high-dimensional mass cytometry (CyTOF) in baseline blood samples of patients with advanced NSCLC treated with pembrolizumab. CyTOF data were analyzed by machine-learning algorithms (Citrus, tSNE) and confirmed by manual gating followed by principal component analysis (between-group analysis).

RESULTS

We analyzed 27 patients from the seminal KEYNOTE-001 study (median follow-up of 60.6 months). We demonstrate that blood baseline frequencies of classical monocytes, natural killer (NK) cells, and ICOS+ CD4+ T cells are significantly associated with improved objective response rates, progression-free survival, and overall survival (OS). In addition, we report that a baseline immune peripheral score combining these three populations strongly predicts pembrolizumab efficacy (OS: HR = 0.25; 95% confidence interval = 0.12-0.51; P < 0.0001).

CONCLUSIONS

As this immune monitoring is easy in routine practice, we anticipate our findings may improve prediction of ICI benefit in patients with advanced NSCLC.

Facts and Hopes in the Relationship of EBV with Cancer Immunity and Immunotherapy

Epstein-Barr virus (EBV), the first identified human tumor virus, infects and takes up residency in almost every human. However, EBV genome-positive tumors arise in only a tiny minority of infected people, presumably when the virus-carrying tumor cells are able to evade immune surveillance. Traditional views regard viral antigens as the principal targets of host immune surveillance against virus-infected cells. However, recent findings indicate that EBV-infected/-transformed B cells elicit both cytotoxic CD8+ and CD4+ T-cell responses against a wide range of overexpressed cellular antigens known to function as tumor-associated antigens (TAA), in addition to various EBV-encoded antigens. This not only broadens the ways by which the immune system controls EBV infection and prevents it from causing cancers, but also potentially extends immune protection toward EBV-unrelated cancers by targeting shared TAAs. The goal of this review is to incorporate these new findings with literature data and discuss future directions for improved understanding of EBV-induced antitumor immunity, as well as the hopes for rational immune strategies for cancer prevention and therapy.

Comprehensive Molecular Analyses of an SLC Family-Based Model in Stomach Adenocarcinoma

Background: Solute carrier (SLC) family members are crucial in transporting amino acids across membranes. Amino acids are indispensable for both cancer and immune cells. However, the clinical significance of amino acid transporting SLC members in stomach adenocarcinoma (STAD) remains unclear. This study aimed to develop an SLC family-based model to predict the prognosis and the response of STAD patients to immunotherapy.

Methods: A total of 1239 tumor cases were obtained from online databases. The training set (n = 371) consisted of RNA sequencing profiles obtained from The Cancer Genome Atlas (TCGA), while those from Gene Expression Omnibus (GEO) were used as the test set. Subsequently, the clinical characteristics and immune profiles were investigated, and potential immunotherapy response prediction values of the model were assessed.

Results: Based on the TCGA cohort, an SLC family-based model was developed using multivariate Cox analysis. All tumor cases were stratified into high- and low-risk groups considering the SLC model. High-risk patients had a worse overall survival (OS) than low-risk patients, consistent with the results of GEO cohorts. Comprehensive analyses revealed that the high-risk group was correlated with aggressiveness-related pathways, whereas the low-risk group had better T helper cell infiltration and stronger immunotherapy response. Compared to the high-risk group, the low-risk group presented increased PD-L1 and tumor mutation burden.

Conclusion: This SLC family-based model has the potential to predict the prognosis and immunotherapy outcomes of STAD patients. The survival of patients in the low-risk group was greatly prolonged, and the patients may benefit more from immunotherapy.

A synthetic DNA template for fast manufacturing of versatile single epitope mRNA

A flexible, affordable, and rapid vaccine platform is necessary to unlock the potential of personalized cancer vaccines in order to achieve full clinical efficiency. mRNA cancer vaccine manufacture relies on the rigid sequence design of multiepitope constructs produced by laborious bacterial cloning and time-consuming plasmid preparation. Here, we introduce a synthetic DNA template (SDT) assembly process, which allows cost- and time-efficient manufacturing of single (neo)epitope mRNA. We benchmarked SDT-derived mRNA against mRNA derived from a plasmid DNA template (PDT), showing that monocyte-derived dendritic cells (moDCs) electroporated with SDT-mRNA or PDT-mRNA, encoding HLA-I- or HLA-II-restricted (neo)epitopes, equally activated T cells that were modified to express the cognate T cell receptors. Furthermore, we validated the SDT-mRNA platform for neoepitope immunogenicity screening using the characterized HLA-A2-restricted neoepitope DHX40B and four new candidate HLA-A2-restricted melanoma neoepitopes. Finally, we compared SDT-mRNA with PDT-mRNA for vaccine development purposes. moDCs electroporated with mRNA encoding the HLA-A2-restricted, mutated Melan-A/Mart-1 epitope together with TriMix mRNA-generated high levels of functional Melan-A/Mart-1-specific CD8⁺ T cells. In conclusion, SDT single epitope mRNA can be manufactured in a more flexible, cost-efficient, and time-efficient way compared with PDT-mRNA, allowing prompt neoepitope immunogenicity screening, and might be exploited for the development of personalized cancer vaccines.

Immune Biomarkers in Blood from Sarcoma Patients: A Pilot Study

The main role of the host immune system is to identify and eliminate cancer cells, which is a complex process, but it is not a fail-safe mechanism. Many sarcoma patients succumb to this disease despite treatments rendered. The aim of this pilot study was to compare the levels of CD4+ T-cells, T-regulatory (Treg) cells, and cytokines such as tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ), interleukin-17A (IL-17A), and transforming growth factor-beta-1 (TGF-β1) in peripheral blood leukocytes of sarcoma patients and healthy controls. For gene expression studies, total ribonucleic acid (RNA) was extracted from peripheral blood leukocytes and genes that were differentially regulated in peripheral blood leukocytes of sarcoma patients compared with healthy controls were determined using a commercial T-helper cell differentiation quantitative polymerase chain reaction (qPCR) array. Flow cytometer analysis was performed on blood samples from 26 sarcoma patients and 10 healthy controls to identify the levels of CD4+ T-cells and T-reg cells. The level of cytokines in plasma and culture supernatant were quantified using commercial enzyme-linked immunosorbent assay (ELISA) kits. A marked reduction in the percentage of CD4+ T-cells (p = 0.037) and levels of TNF-α (p = 0.004) and IFN-γ (0.010) was observed in sarcoma patients. Gene expression analysis showed five genes (homeobox A10 (HOXA10), GATA binding protein 3 (GATA3), prostaglandin D2 receptor 2 (PTGDR2), thymocyte selection associated high mobility group box (TOX), and C-C motif chemokine receptor 3 (CCR3)) were dysregulated (p < 0.05) in sarcoma patients. This study suggests that T-helper-1 immune responses are reduced in sarcoma patients.

Novel intravesical bacterial immunotherapy induces rejection of BCG-unresponsive established bladder tumors

Background

Intravesical BCG is the gold-standard therapy for non-muscle invasive bladder cancer (NMIBC); however, it still fails in a significant proportion of patients, so improved treatment options are urgently needed.

Methods

Here, we compared BCG antitumoral efficacy with another live attenuated mycobacteria, MTBVAC, in an orthotopic mouse model of bladder cancer (BC). We aimed to identify both bacterial and host immunological factors to understand the antitumoral mechanisms behind effective bacterial immunotherapy for BC.

Results

We found that the expression of the BCG-absent proteins ESAT6/CFP10 by MTBVAC was determinant in mediating bladder colonization by the bacteria, which correlated with augmented antitumoral efficacy. We further analyzed the mechanism of action of bacterial immunotherapy and found that it critically relied on the adaptive cytotoxic response. MTBVAC enhanced both tumor antigen-specific CD4⁺ and CD8⁺ T-cell responses, in a process dependent on stimulation of type 1 conventional dendritic cells. Importantly, improved intravesical bacterial immunotherapy using MBTVAC induced eradication of fully established bladder tumors, both as a monotherapy and specially in combination with the immune checkpoint inhibitor antiprogrammed cell death ligand 1 (anti PD-L1).

Conclusion

These results contribute to the understanding of the mechanisms behind successful bacterial immunotherapy against BC and characterize a novel therapeutic approach for BCG-unresponsive NMIBC cases.

Tissue-Resident Memory CD4+ T Cells Play a Dominant Role in the Initiation of Antitumor Immunity

Tumor immunology has been studied extensively. Tumor immunology-based cancer immunotherapy has become one of the most promising approaches for cancer treatment. However, one of the fundamental aspects of tumor immunology-the initiation of antitumor immunity-is not fully understood. Compared to that of CD8⁺ T cells, the effect of CD4⁺ T cells on antitumor immunity has not been fully appreciated. Using a gene knockout mouse model, the mice of which are deficient in the TCRα repertoire, specifically lacking invariant NKT and mucosal-associated invariant T cells, we found that the deficiency in TCRα repertoire diversity did not affect the antitumor immunity, at least to B16BL6 melanoma and EO771 breast cancer. However, after acquiring thymocytes or splenocytes from wild-type mice, these knockout mice exhibited greatly enhanced and long-lasting antitumor immunity. This enhanced antitumor immunity depended on CD4⁺ T cells, especially CD4⁺ tissue-resident memory T (T_RM) cells, but not invariant NKT or CD8⁺ T cells. We also present evidence that CD4⁺ T_RM cells initiate antitumor immunity through IFN-γ, and the process is dependent on NK cells. The CD4⁺ T_RM/NK axis appears to control tumor formation and development by eliminating tumor cells and modulating the tumor microenvironment. Taken together, our results demonstrated that CD4⁺ T_RM cells play a dominant role in the initiation of antitumor immunity.

Development of Cancer Immunotherapies

Cancer immunotherapy, or the utilization of components of the immune system to target and eliminate cancer, has become a highly active area of research in the past several decades and a common treatment strategy for several cancer types. The concept of harnessing the immune system for this purpose originated over 100 years ago when a physician by the name of William Coley successfully treated several of his cancer patients with a combination of live and attenuated bacteria, later known as "Coley's Toxins", after observing a subset of prior patients enter remission following their diagnosis with the common bacterial infection, erysipelas. However, it was not until late in the twentieth century that cancer immunotherapies were developed for widespread use, thereby transforming the treatment landscape of numerous cancer types. Pivotal studies elucidating molecular and cellular functions of immune cells, such as the discovery of IL-2 and production of monoclonal antibodies, fostered the development of novel techniques for studying the immune system and ultimately the development and approval of several cancer immunotherapies by the United States Food and Drug Association in the 1980s and 1990s, including the tuberculosis vaccine-Bacillus Calmette-Guérin, IL-2, and the CD20-targeting monoclonal antibody. Approval of the first therapeutic cancer vaccine, Sipuleucel-T, for the treatment of metastatic castration-resistant prostate cancer and the groundbreaking success and approval of immune checkpoint inhibitors and chimeric antigen receptor T cell therapy in the last decade, have driven an explosion of interest in and pursuit of novel cancer immunotherapy strategies. A broad range of modalities ranging from antibodies to adoptive T cell therapies is under investigation for the generalized treatment of a broad spectrum of cancers as well as personalized medicine. This chapter will focus on the recent advances, current strategies, and future outlook of immunotherapy development for the treatment of cancer.

CD4+ Cytotoxic T cells - Phenotype, Function and Transcriptional Networks Controlling Their Differentiation Pathways

The two major subsets of peripheral T cells are classically divided into the CD4⁺ T helper cells and the cytotoxic CD8⁺ T cell lineage. However, the appearance of some effector CD4⁺ T cell populations displaying cytotoxic activity, in particular during viral infections, has been observed, thus breaking the functional dichotomy of CD4⁺ and CD8⁺ T lymphocytes. The strong association of the appearance of CD4⁺ cytotoxic T lymphocytes (CD4 CTLs) with viral infections suggests an important role of this subset in antiviral immunity by controlling viral replication and infection. Moreover, CD4 CTLs have been linked with anti-tumor activity and might also cause immunopathology in autoimmune diseases. This raises interest into the molecular mechanisms regulating CD4 CTL differentiation, which are poorly understood in comparison to differentiation pathways of other Th subsets. In this review, we provide a brief overview about key features of CD4 CTLs, including their role in viral infections and cancer immunity, and about the link between CD4 CTLs and immune-mediated diseases. Subsequently, we will discuss the current knowledge about transcriptional and epigenetic networks controlling CD4 CTL differentiation and highlight recent data suggesting a role for histone deacetylases in the generation of CD4 CTLs.

Prognostic value of CD4+ T lymphopenia in non-small cell lung Cancer

BACKGROUND

There is a paucity of data regarding the prognostic influence of peripheral blood CD4+ T lymphopenia in non-small cell lung cancer (NSCLC). Therefore, we investigated the prognostic value of T lymphopenia in NSCLC.

MATERIALS

Treatment-naive patients with a pathological diagnosis of NSCLC, at clinical stage I to IV were included in the prospective TELOCAP1 study. Lymphocytes count was evaluated in peripheral blood by flow cytometry. CD4+ and CD8+ T lymphopenia were defined as an absolute count of < 500/μL and < 224/μL respectively. The prognostic value of T lymphopenia was analyzed in the whole population, in local/loco-regional (stage I-IIIB) and in advanced (stage IV) NSCLC disease, using the Kaplan-Meier method and Cox regression models for survival curves and multivariate analysis, respectively.

RESULTS

Between July 2010 and January 2014, 169 evaluable patients with clinical stage I to IV NSCLC were prospectively enrolled. The prevalence of CD4+ and CD8+ T lymphopenia was similar in the study population (around 29%). Patients with CD4+ T lymphopenia showed lower overall survival than those with CD4+ T lymphocytes count > 500/μL (median overall survival (OS) 16.1 versus 21.7 months, hazard ratio (HR): 1.616 [95% CI: 1.1-2.36], p = 0.012). This association with OS was especially marked in local/loco-regional NSCLC stages (median OS, 21.8 versus 72 months, respectively, HR: 1.88 [95% CI: 0.9-3.8], p = 0.035). Multivariate analysis confirmed the worse prognosis associated with CD4+ T lymphopenia in local/loco-regional NSCLC, but not in metastatic patients (HR 2.028 [95% CI = 1.065-3.817] p = 0.02). Restricted cubic spline analysis showed that patients with CD4+ T lymphocytes count ≤500/μL displayed a high risk of death regardless of NSCLC clinical stage. There was no obvious relationship between CD8+ T lymphopenia and clinical outcome.

CONCLUSION

We identified CD4+ T lymphopenia as an independent prognostic factor in local/loco-regional stages of NSCLC and CD4+ T lymphopenia is also associated with a high risk of death, regardless of NSCLC clinical stage.

TRIAL REGISTRATION

EUDRACT: 2009-A00642-55.

Neoantigen Presentation and IFNγ Signaling on the Same Tumor-associated Macrophage are Necessary for CD4 T Cell-mediated Antitumor Activity in Mice

Tumor Associated Macrophages (TAMs) promote tumor survival, angiogenesis and metastases. Although they express MHC Class II molecules, little is known about their ability to present tumor antigens to tumor infiltrating CD4 T cells, nor what are the consequences of such presentation. To answer these questions, we used a C57/BL10 mouse tumor model where we subcutaneously implant a bladder carcinoma cell line naturally expressing the H-Y male antigen into female mice, making the H-Y antigen a de facto neoantigen. We found that TAMs indeed present tumor antigens to effector CD4 T cells and that such presentation is necessary for tumor rejection. As consequence of this interaction TAMs are re-educated to produce lower amounts of tumor promoting proteins and greater amounts of inflammatory proteins. The re-education process of the TAMs is transcriptionally characterized by an IFN-γ signature, including genes of known anti-viral and anti-bacterial functions. CD4 production of IFN-γ, and not TNF-α or CD40L, is required for the re-education process and tumor rejection. Furthermore, IFN-γ signaling on antigen presenting TAMs and not on bystander TAMs, is necessary for the anti-tumor effect. These data identify critical mechanisms of tumor rejection by CD4 T cells and underscores the importance of effector CD4 T cell-tissue macrophage interactions not only at the tumors site but potentially in other tissues.

HLA-DR Presentation of the Tumor Antigen MSLN Associates with Clinical Outcome of Ovarian Cancer Patients

Simple Summary

The immunopeptidome represents the entirety of peptides that are presented on the surface of cells on human leukocyte antigen (HLA) molecules and are recognized by the T-cell receptors of CD4⁺ and CD8⁺ T-cells. Malignant cells present tumor-associated antigens essential for tumor immune surveillance, which can be targeted by T-cell-based immunotherapy approaches. For ovarian carcinomas, various tumor-associated antigens, such as Mucin-16 and Mesothelin, have been described. The aim of our study is to analyze immunopeptidome-defined tumor antigen presentation in ovarian carcinoma patients in relation to clinical characteristics and disease outcomes to define potential biomarkers. Our work demonstrates the central role of HLA-DR-restricted peptide presentation of the tumor antigen Mesothelin and of CD4⁺ T-cell responses for tumor immune surveillance, and underlines Mesothelin as a prime target antigen for novel immunotherapeutic approaches for ovarian carcinoma patients.

Abstract

T-cell recognition of HLA-presented antigens is central for the immunological surveillance of malignant disease and key for the development of novel T-cell-based immunotherapy approaches. In recent years, large-scale immunopeptidome studies identified naturally presented tumor-associated antigens for several malignancies. Regarding ovarian carcinoma (OvCa), Mucin-16 (MUC16) and Mesothelin (MSLN) were recently described as the top HLA class I- and HLA class II-presented tumor antigens, respectively. Here, we investigate the role and impact of immunopeptidome-presented tumor antigens on the clinical outcomes of 39 OvCa patients with a follow-up time of up to 50 months after surgery. Patients with a HLA-restricted presentation of high numbers of different MSLN-derived peptides on their tumors exhibited significantly prolonged progression-free (PFS) and overall survival (OS), whereas the presentation of MUC16-derived HLA class I-restricted peptides had no impact. Furthermore, a high HLA-DRB gene expression was associated with increased PFS and OS. In line, in silico prediction revealed that MSLN-derived HLA class II-presented peptides are predominantly presented on HLA-DR allotypes. In conclusion, the correlation of MSLN tumor antigen presentation and HLA-DRB gene expression with prolonged survival indicates a central role of CD4⁺ T-cell responses for tumor immune surveillance in OvCa, and highlights the importance of immunopeptidome-guided tumor antigen discovery.

A variety of 'exhausted' T cells in the tumor microenvironment

In T cell biology, 'exhaustion' was initially described as a hyporesponsive state in CD8 + T cells during chronic infections. Recently, exhaustion has been recognized as a T-cell dysfunctional state in the tumor microenvironment (TME). The term 'exhaustion' is used mainly to refer to effector T cells with a reduced capacity to secrete cytokines and an increased expression of inhibitory receptors. The upregulation of exhaustion-related inhibitory receptors, including programmed cell death protein 1 (PD-1), in such T cells has been associated with the development of tumors, prompting the development of immune checkpoint inhibitors. In addition to CD8 + T cells, CD4 + T cells, including the regulatory T (Treg) cell subset, perform a wide variety of functions within the adaptive immune system. Upregulation of the same inhibitory receptors that are associated with CD8 + T-cell exhaustion has also been identified in CD4 + T cells in chronic infections and cancers, suggesting a similar CD4 + T-cell exhaustion phenotype. For instance, high expression of PD-1 has been observed in Treg cells in the TME, and such Treg cells can play an important role in the resistance to PD-1 blockade therapies. Furthermore, recent progress in single-cell RNA sequencing has shown that CD4 + T cells with cytotoxic activity are also vulnerable to exhaustion. In this review, we will discuss novel insights into various exhausted T-cell subsets, which could reveal novel therapeutic targets and strategies to induce a robust antitumor immune response.

Immunomodulatory and Direct Activities of Ropeginterferon Alfa-2b on Cancer Cells in Mouse Models of Leukemia

Although ropeginterferon alfa‐2b has recently been clinically applied to myeloproliferative neoplasms with promising results, its antitumor mechanism has not been thoroughly investigated. Using a leukemia model developed in immunocompetent mice, we evaluated the direct cytotoxic effects and indirect effects induced by ropeginterferon alfa‐2b in tumor cells. Ropeginterferon alfa‐2b therapy significantly prolonged the survival of mice bearing leukemia cells and led to long‐term remission in some mice. Alternatively, conventional interferon‐alpha treatment slightly extended the survival and all mice died. When ropeginterferon alfa‐2b was administered to interferon‐alpha receptor 1–knockout mice after the development of leukemia to verify the direct effect on the tumor, the survival of these mice was slightly prolonged; nevertheless, all of them died. In vivo CD4⁺ or CD8⁺ T‐cell depletion resulted in a significant loss of therapeutic efficacy in mice. These results indicate that the host adoptive immunostimulatory effect of ropeginterferon alfa‐2b is the dominant mechanism through which tumor cells are suppressed. Moreover, mice in long‐term remission did not develop leukemia, even after tumor rechallenge. Rejection of rechallenge tumors was canceled only when both CD4⁺ and CD8⁺ T cells were removed in vivo, which indicates that each T‐cell group functions independently in immunological memory. We show that ropeginterferon alfa‐2b induces excellent antitumor immunomodulation in hosts. Our finding serves in devising therapeutic strategies with ropeginterferon alfa‐2b.

The Role of Type-2 Conventional Dendritic Cells in the Regulation of Tumor Immunity

Simple Summary

Recent studies revealed that type-2 conventional dendritic cells (cDC2s) play an important role in antitumor immunity by promoting cytotoxic T-cell responses and helper T-cell differentiation. This review outlines the role of cDC2s in tumor immunity and summarizes the latest progress regarding their potential in cancer vaccination and cDC2-targeted cancer immunotherapy.

Abstract

Conventional dendritic cells (cDCs) orchestrate immune responses to cancer and comprise two major subsets: type-1 cDCs (cDC1s) and type-2 cDCs (cDC2s). Compared with cDC1s, which are dedicated to the activation of CD8⁺ T cells, cDC2s are ontogenically and functionally heterogeneous, with their main function being the presentation of exogenous antigens to CD4⁺ T cells for the initiation of T helper cell differentiation. cDC1s play an important role in tumor-specific immune responses through cross-presentation of tumor-derived antigens for the priming of CD8⁺ T cells, whereas little is known of the role of cDC2s in tumor immunity. Recent studies have indicated that human cDC2s can be divided into at least two subsets and have implicated these cells in both anti- and pro-tumoral immune responses. Furthermore, the efficacy of cDC2-based vaccines as well as cDC2-targeted therapeutics has been demonstrated in both mouse models and human patients. Here we summarize current knowledge about the role of cDC2s in tumor immunity and address whether these cells are beneficial in the context of antitumor immune responses.

New Developments in T Cell Immunometabolism and Implications for Cancer Immunotherapy

Despite rapid advances in the field of immunotherapy, the elimination of established tumors has not been achieved. Many promising new treatments such as adoptive cell therapy (ACT) fall short, primarily due to the loss of T cell effector function or the failure of long-term T cell persistence. With the availability of new tools and advancements in technology, our understanding of metabolic processes has increased enormously in the last decade. Redundancy in metabolic pathways and overlapping targets that could address the plasticity and heterogenous phenotypes of various T cell subsets have illuminated the need for understanding immunometabolism in the context of multiple disease states, including cancer immunology. Herein, we discuss the developing field of T cell immunometabolism and its crucial relevance to improving immunotherapeutic approaches. This in-depth review details the metabolic pathways and preferences of the antitumor immune system and the state of various metabolism-targeting therapeutic approaches.

cPLA2 blockade attenuates S100A7-mediated breast tumorigenicity by inhibiting the immunosuppressive tumor microenvironment

BACKGROUND

Molecular mechanisms underlying inflammation-associated breast tumor growth are poorly studied. S100A7, a pro-inflammatory molecule has been shown to enhance breast cancer growth and metastasis. However, the S100A7-mediated molecular mechanisms in enhancing tumor growth and metastasis are unclear.

METHODS

Human breast cancer tissue and plasma samples were used to analyze the expression of S100A7, cPLA2, and PGE2. S100A7-overexpressing or downregulated human metastatic breast cancer cells were used to evaluate the S100A7-mediated downstream signaling mechanisms. Bi-transgenic mS100a7a15 overexpression, TNBC C3 (1)/Tag transgenic, and humanized patient-derived xenograft mouse models and cPLA2 inhibitor (AACOCF3) were used to investigate the role of S100A7/cPLA2/PGE2 signaling in tumor growth and metastasis. Additionally, CODEX, a highly advanced multiplexed imaging was employed to delineate the effects of S100A7/cPLA2 inhibition on the recruitment of various immune cells.

RESULTS

In this study, we found that S100A7 and cPLA2 are highly expressed and correlate with decreased overall survival in breast cancer patients. Further mechanistic studies revealed that S100A7/RAGE signaling promotes the expression of cPLA2 to mediate its oncogenic effects. Pharmacological inhibition of cPLA2 suppressed S100A7-mediated tumor growth and metastasis in multiple pre-clinical models including transgenic and humanized patient-derived xenograft (PDX) mouse models. The attenuation of cPLA2 signaling reduced S100A7-mediated recruitment of immune-suppressive myeloid cells in the tumor microenvironment (TME). Interestingly, we discovered that the S100A7/cPLA2 axis enhances the immunosuppressive microenvironment by increasing prostaglandin E2 (PGE2). Furthermore, CO-Detection by indEXing (CODEX) imaging-based analyses revealed that cPLA2 inhibition increased the infiltration of activated and proliferating CD4⁺ and CD8⁺ T cells in the TME. In addition, CD163⁺ tumor associated-macrophages were positively associated with S100A7 and cPLA2 expression in malignant breast cancer patients.

CONCLUSIONS

Our study provides new mechanistic insights on the cross-talk between S100A7/cPLA2 in enhancing breast tumor growth and metastasis by generating an immunosuppressive TME that inhibits the infiltration of cytotoxic T cells. Furthermore, our studies indicate that S100A7/cPLA2 could be used as novel prognostic marker and cPLA2 inhibitors as promising drugs against S100A7-overexpressing aggressive breast cancer.

DNA-double strand breaks enhance the expression of major histocompatibility complex class II through the ATM-NF-κΒ-IRF1-CIITA pathway

Major histocompatibility complex class II (MHC II) is important for the adaptive immune response because MHC II presents processed antigens to a cluster of differentiation 4 (CD4)-positive T-cells. Conventional doses of chemotherapeutic agents induce tumor cell death by causing DNA double-strand breaks (DSBs). However, cellular responses caused by sub-lethal doses of chemotherapeutic agents are poorly understood. In this study, using low doses of chemotherapeutic agents, we showed that DSBs enhanced the expression of MHC II on cells that originate from antigen-presenting cells (APCs). These agents induced the MHC class II transactivator (CIITA), the master regulator of MHC II, and interferon regulatory factor 1 (IRF1), a transcription factor for CIITA. Short hairpin RNA against IRF1 suppressed chemotherapeutic agent-induced CIITA expression, whereas exogenous expression of IRF1 induced CIITA. Inhibition of ataxia-telangiectasia mutated (ATM), a DSB-activated kinase, suppressed induction of IRF1, CIITA, and MHC II. Similar results were observed by inhibiting NF-κB, a downstream target of ATM. These results suggest that DSBs induce MHC II activity via the ATM-NF-κB-IRF1-CIITA pathway in cells that intrinsically present antigens. Additionally, chemotherapeutic agents induced T-cell regulatory molecules. Our findings suggest that chemotherapeutic agents enhance the antigen presentation activity of APCs for T-cell activation.

What Happens to the Immune Microenvironment After PD-1 Inhibitor Therapy?

The fruitful results of tumor immunotherapy establish its indispensable status in the regulation of the tumorous immune context. It seems that the treatment of programmed cell death receptor 1 (PD-1) blockade is one of the most promising approaches for cancer control. The significant efficacy of PD-1 inhibitor therapy has been made in several cancer types, such as breast cancer, lung cancer, and multiple myeloma. Even so, the mechanisms of how anti-PD-1 therapy takes effect by impacting the immune microenvironment and how partial patients acquire the resistance to PD-1 blockade have yet to be studied. In this review, we discuss the cross talk between immune cells and how they promote PD-1 blockade efficacy. In addition, we also depict factors that may underlie tumor resistance to PD-1 blockade and feasible solutions in combination with it.

Antitumor Peptide-Based Vaccine in the Limelight

The success of the immune checkpoint blockade has provided a proof of concept that immune cells are capable of attacking tumors in the clinic. However, clinical benefit is only observed in less than 20% of the patients due to the non-specific activation of immune cells by the immune checkpoint blockade. Developing tumor-specific immune responses is a challenging task that can be achieved by targeting tumor antigens to generate tumor-specific T-cell responses. The recent advancements in peptide-based immunotherapy have encouraged clinicians and patients who are struggling with cancer that is otherwise non-treatable with current therapeutics. By selecting appropriate epitopes from tumor antigens with suitable adjuvants, peptides can elicit robust antitumor responses in both mice and humans. Although recent experimental data and clinical trials suggest the potency of tumor reduction by peptide-based vaccines, earlier clinical trials based on the inadequate hypothesis have misled that peptide vaccines are not efficient in eliminating tumor cells. In this review, we highlighted the recent evidence that supports the rationale of peptide-based antitumor vaccines. We also discussed the strategies to select the optimal epitope for vaccines and the mechanism of how adjuvants increase the efficacy of this promising approach to treat cancer.

Bystander CD4+ T cells infiltrate human tumors and are phenotypically distinct

Tumor-specific T cells likely underpin effective immune checkpoint-blockade therapies. Yet, most studies focus on Treg cells and CD8⁺ tumor-infiltrating lymphocytes (TILs). Here, we study CD4⁺ TILs in human lung and colorectal cancers and observe that non-Treg CD4⁺ TILs average more than 70% of total CD4⁺ TILs in both cancer types. Leveraging high dimensional analyses including mass cytometry, we reveal that CD4⁺ TILs are phenotypically heterogeneous, within each tumor and across patients. Consistently, we find different subsets of CD4⁺ TILs showing characteristics of effectors, tissue resident memory (Trm) or exhausted cells (expressing PD-1, CTLA-4 and CD39). In both cancer types, the frequencies of CD39^- non-Treg CD4⁺ TILs strongly correlate with frequencies of CD39^- CD8⁺ TILs, which we and others have previously shown to be enriched for cells specific for cancer-unrelated antigens (bystanders). Ex-vivo, we demonstrate that CD39^- CD4⁺ TILs can be specific for cancer-unrelated antigens, such as HCMV epitopes. Overall, our findings highlight that CD4⁺ TILs can also recognize cancer-unrelated antigens and suggest measuring CD39 expression as a straightforward way to quantify or isolate bystander CD4⁺ T cells.

Roles of CD4+ T cells as mediators of antitumor immunity

It has been well established that CD8+ T cells serve as effector cells of the adaptive immune response against tumors, whereas CD4+ T cells either help or suppress the generation of CD8+ cytotoxic T cells. However, in several experimental models as well as in cancer patients, it has been shown that CD4+ T cells can also mediate antitumor immunity either directly by killing tumor cells or indirectly by activating innate immune cells or by reducing tumor angiogenesis. In this review, we discuss the growing evidence of this underappreciated role of CD4+ T cells as mediators of antitumor immunity.

CD4 T-Cell Exhaustion: Does It Exist and What Are Its Roles in Cancer?

In chronic infections and in cancer, persistent antigen stimulation under suboptimal conditions can lead to the induction of T-cell exhaustion. Exhausted T cells are characterized by an increased expression of inhibitory markers and a progressive and hierarchical loss of function. Although cancer-induced exhaustion in CD8 T cells has been well-characterized and identified as a therapeutic target (i.e., via checkpoint inhibition), in-depth analyses of exhaustion in other immune cell types, including CD4 T cells, is wanting. While perhaps attributable to the contextual discovery of exhaustion amidst chronic viral infection, the lack of thorough inquiry into CD4 T-cell exhaustion is particularly surprising given their important role in orchestrating immune responses through T-helper and direct cytotoxic functions. Current work suggests that CD4 T-cell exhaustion may indeed be prevalent, and as CD4 T cells have been implicated in various disease pathologies, such exhaustion is likely to be clinically relevant. Defining phenotypic exhaustion in the various CD4 T-cell subsets and how it influences immune responses and disease severity will be crucial to understanding collective immune dysfunction in a variety of pathologies. In this review, we will discuss mechanistic and clinical evidence for CD4 T-cell exhaustion in cancer. Further insight into the derivation and manifestation of exhaustive processes in CD4 T cells could reveal novel therapeutic targets to abrogate CD4 T-cell exhaustion in cancer and induce a robust antitumor immune response.

The role of CD4 T cells in rejection of solid tumors

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Versatility of CD4 T cells enables different attack modes towards cancer cells.

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Cooperation of CD4 and CD8 T cells renders anti-tumor responses most efficient.

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Integrating CD4 T cells in cancer therapy will improve clinical outcome.

The focus in cancer immunotherapy has mainly been on CD8 T cells, as they can directly recognize cancer cells. CD4 T cells have largely been neglected, because most cancers lack MHC II expression and cannot directly be recognized by CD4 T cells. Yet, tumor antigens can be captured and cross-presented by MHC II-expressing tumor stromal cells. Recent data suggest that CD4 T cells act as a swiss army knife against tumors. They can kill cancer cells, if they express MHC II, induce tumoricidal macrophages, induces cellular senescence of cancer cells, destroy the tumor vasculature through cytokine release and help CD8 T cells in the effector phase. We foresee a great future for CD4 T cells in the clinic, grafted with tumor antigen specificity by T cell receptor gene transfer, either alone or in combination with engineered CD8 T cells.

Vaccination against RhoC induces long-lasting immune responses in patients with prostate cancer: results from a phase I/II clinical trial

Background

Peptide-based vaccination is a rational option for immunotherapy of prostate cancer. In this first-in-man phase I/II study, we assessed the safety, tolerability and immunological impact of a synthetic long peptide vaccine targeting Ras homolog gene family member C (RhoC) in patients with prostate cancer. RhoC is a small GTPase overexpressed in advanced solid cancers, metastases and cancer stem cells.

Methods

Twenty-two patients who had previously undergone radical prostatectomy received subcutaneous injections of 0.1 mg of a single RhoC-derived 20mer peptide emulsified in Montanide ISA-51 every 2 weeks for the first six times, then five times every 4 weeks for a total treatment time of 30 weeks. The drug safety and vaccine-specific immune responses were assessed during treatment and thereafter within a 13-month follow-up period. Serum level of prostate-specific antigen was measured up to 26 months postvaccination.

Results

Most patients (18 of 21 evaluable) developed a strong CD4 T cell response against the vaccine, which lasted at least 10 months following the last vaccination. Three promiscuouslypresented HLA-class II epitopes were identified. Vaccine-specific CD4 T cells were polyfunctional and effector memory T cells that stably expressed PD-1 (CD279) and OX-40 (CD134), but not LAG-3 (CD223). One CD8 T cell response was detected in addition. The vaccine was well tolerated and no treatment-related adverse events of grade ≥3 were observed.

Conclusion

Targeting of RhoC induced a potent and long-lasting T cell immunity in the majority of the patients. The study demonstrates an excellent safety and tolerability profile. Vaccination against RhoC could potentially delay or prevent tumor recurrence and metastasis formation.

Trial registration number

NCT03199872.

PD-L1 Overexpression, SWI/SNF Complex Deregulation, and Profound Transcriptomic Changes Characterize Cancer-Dependent Exhaustion of Persistently Activated CD4+ T Cells

Simple Summary

Growing tumors induce an immune response. For proper immune response, both CD8⁺ and CD4⁺ effector T cells are required. Tumors avoid attacks from tumor-infiltrating lymphocytes (TILs) via induction of several inhibitory signals, such as PD-L1/2, which bind to the PD-1 receptor, consequently leading to T cell dysfunction, exhaustion, and apoptosis. The mechanism of T cell exhaustion has been studied mostly in CD8+ T cells, although some results suggest that CD4⁺ effector T cells also undergo exhaustion. In this study, we analyze global transcript profiling, PD-1 and PD-L1 expression, and chromatin status on the PD-L1 locus. We find that in exhausted CD4⁺ T cells, the levels of PD-L1 are increased at both the transcript and protein levels, while PD-L1 expression depends on SWI/SNF chromatin remodeling and PRC2-repressive complexes. The expression of PD-L1 in exhausted CD4⁺ T cells can be reversible.

Abstract

Growing tumors avoid recognition and destruction by the immune system. During continuous stimulation of tumor-infiltrating lymphocytes (TILs) by tumors, TILs become functionally exhausted; thus, they become unable to kill tumor cells and to produce certain cytokines and lose their ability to proliferate. This collectively results in the immune escape of cancer cells. Here, we show that breast cancer cells expressing PD-L1 can accelerate exhaustion of persistently activated human effector CD4⁺ T cells, manifesting in high PD-1 and PD-L1 expression level son T cell surfaces, decreased glucose metabolism genes, strong downregulation of SWI/SNF chromatin remodeling complex subunits, and p21 cell cycle inhibitor upregulation. This results in inhibition of T cell proliferation and reduction of T cell numbers. The RNAseq analysis on exhausted CD4⁺ T cells indicated strong overexpression of IDO1 and genes encoding pro-inflammatory cytokines and chemokines. Some interleukins were also detected in media from CD4⁺ T cells co-cultured with cancer cells. The PD-L1 overexpression was also observed in CD4⁺ T cells after co-cultivation with other cell lines overexpressing PD-L1, which suggested the existence of a general mechanism of CD4⁺ T cell exhaustion induced by cancer cells. The ChIP analysis on the PD-L1 promoter region indicated that the BRM recruitment in control CD4⁺ T cells was replaced by BRG1 and EZH2 in CD4⁺ T cells strongly exhausted by cancer cells. These findings suggest that epi-drugs such as EZH2 inhibitors may be used as immunomodulators in cancer treatment.

Immunity beyond cancer cells: perspective from tumor tissue

Investigation of cancer as a cell-level disease has led to the development of cancer cell-directed therapies including cytotoxic T lymphocyte (CTL)-based immunotherapy; yet, many patients are refractory to these modalities of cancer treatment and acquired resistance frequently occurs. Of note, cancer environment controls the manifestation of cancerous cell phenotype. Helper T (Th) cells orchestrate immune defense responses targeting cancer cells as well as the tumor microenvironment. Recent studies have shown that in addition to interferon (IFN)-γ-producing Th1 cells, interleukin (IL)-4-producing Th2 cells function as potent anticancer effectors in part by promoting tumor stroma reconfiguration and tumor tissue repair. Such Th cell-mediated tissue-level immunity may be harnessed for novel modalities of cancer environment immunotherapy.

Default polyfunctional T helper 1 response to ample signal 1 alone

CD4+ T cells integrate well-defined signals from the T-cell receptor (TCR) (signal 1) and a host of costimulatory molecules (signal 2) to initiate clonal expansion and differentiation into diverse functional T helper (Th) subsets. However, our ability to guide the expansion of context-appropriate Th subsets by deploying these signals in vaccination remains limited. Using cell-based vaccines, we selectively amplified signal 1 by exclusive presentation of an optimized peptide:MHC II (pMHC II) complex in the absence of classic costimulation. Contrary to expectations, amplified signal 1 alone was strongly immunogenic and selectively expanded high-affinity TCR clonotypes, despite delivering intense TCR signals. In contrast to natural infection or standard vaccines, amplified signal 1, presented by a variety of professional and nonprofessional antigen-presenting cells (APCs), induced exclusively polyfunctional Th1 effector and memory cells, which protected against retroviral infection and tumor challenge, and expanded tumor-reactive CD4+ T cells otherwise rendered unresponsive in tumor-bearing hosts. Together, our findings uncover a default Th1 response to ample signal 1 and offer a means to selectively prime such protective responses by vaccination.

cIAP1/2 antagonism eliminates MHC class I-negative tumors through T cell-dependent reprogramming of mononuclear phagocytes

Loss of major histocompatibility complex (MHC) class I and interferon-γ (IFN-γ) sensing are major causes of primary and acquired resistance to checkpoint blockade immunotherapy. Thus, additional treatment options are needed for tumors that lose expression of MHC class I. The cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1/2) regulate classical and alternative nuclear factor κB (NF-κB) signaling. Induction of noncanonical NF-κB signaling with cIAP1/2 antagonists mimics costimulatory signaling, augmenting antitumor immunity. We show that induction of noncanonical NF-κB signaling induces T cell-dependent immune responses, even in β2-microglobulin (β2M)-deficient tumors, demonstrating that direct CD8 T cell recognition of tumor cell-expressed MHC class I is not required. Instead, T cell-produced lymphotoxin reprograms both mouse and human macrophages to be tumoricidal. In wild-type mice, but not mice incapable of antigen-specific T cell responses, cIAP1/2 antagonism reduces tumor burden by increasing phagocytosis of live tumor cells. Efficacy is augmented by combination with CD47 blockade. Thus, activation of noncanonical NF-κB stimulates a T cell-macrophage axis that curtails growth of tumors that are resistant to checkpoint blockade because of loss of MHC class I or IFN-γ sensing. These findings provide a potential mechanism for controlling checkpoint blockade refractory tumors.

CD4+ T-cell killing of multiple myeloma cells is mediated by resident bone marrow macrophages

CD4+ T cells may induce potent antitumor immune responses through interaction with antigen-presenting cells within the tumor microenvironment. Using a murine model of multiple myeloma, we demonstrated that adoptive transfer of idiotype-specific CD4+ T cells may elicit curative responses against established multifocal myeloma in bone marrow. This finding indicates that the myeloma bone marrow niche contains antigen-presenting cells that may be rendered tumoricidal. Given the complexity of the bone marrow microenvironment, the mechanistic basis of such immunotherapeutic responses is not known. Through a functional characterization of antitumor CD4+ T-cell responses within the bone marrow microenvironment, we found that killing of myeloma cells is orchestrated by a population of bone marrow-resident CD11b+F4/80+MHC-IIHigh macrophages that have taken up and present secreted myeloma protein. The present results demonstrate the potential of resident macrophages as powerful mediators of tumor killing within the bone marrow and provide a basis for novel therapeutic strategies against multiple myeloma and other malignancies that affect the bone marrow.