Specific T helper cell requirement for optimal induction of cytotoxic T lymphocytes against major histocompatibility complex class II negative tumors

Endogenous viral elements constitute a complementary source of antigens for personalized cancer vaccines

Personalized cancer vaccines (PCVs) largely leverage neoantigens arising from somatic mutations, limiting their application to patients with relatively high tumor mutational burden (TMB). This underscores the need for alternative antigens to design PCVs for low TMB cancers. To this end, we substantiate endogenous retroviral elements (EVEs) as tumor antigens through large-scale genomic analyses of healthy tissues and solid cancers. These analyses revealed that the breadth of EVE expression in tumors stratify checkpoint inhibitor-treated melanoma patients into groups with differential overall and progression-free survival. To enable the design of PCVs containing EVE-derived epitopes with therapeutic potential, we developed a computational pipeline, ObsERV. We show that EVE-derived peptides are presented as epitopes on tumors and can be predicted by ObsERV. Preclinical testing of ObsERV demonstrates induction of sustained poly-functional CD4+ and CD8+ T-cell responses as well as long-term tumor protection. As such, EVEs may facilitate and improve PCVs, especially for low-TMB patients.

Vax-Innate: improving therapeutic cancer vaccines by modulating T cells and the tumour microenvironment

T cells have a critical role in mediating antitumour immunity. The success of immune checkpoint inhibitors (ICIs) for cancer treatment highlights how enhancing endogenous T cell responses can mediate tumour regression. However, mortality remains high for many cancers, especially in the metastatic setting. Based on advances in the genetic characterization of tumours and identification of tumour-specific antigens, individualized therapeutic cancer vaccines targeting mutated tumour antigens (neoantigens) are being developed to generate tumour-specific T cells for improved therapeutic responses. Early clinical trials using individualized neoantigen vaccines for patients with advanced disease had limited clinical efficacy despite demonstrated induction of T cell responses. Therefore, enhancing T cell activity by improving the magnitude, quality and breadth of T cell responses following vaccination is one current goal for improving outcome against metastatic tumours. Another major consideration is how T cells can be further optimized to function within the tumour microenvironment (TME). In this Perspective, we focus on neoantigen vaccines and propose a new approach, termed Vax-Innate, in which vaccination through intravenous delivery or in combination with tumour-targeting immune modulators may improve antitumour efficacy by simultaneously increasing the magnitude, quality and breadth of T cells while transforming the TME into a largely immunostimulatory environment for T cells.

Neoantigen-specific mRNA/DC vaccines for effective anticancer immunotherapy

The development of personalized anticancer vaccines based on neoantigens represents a new direction in cancer immunotherapy. The latest advancement in dendritic cell (DC) tumor vaccine construction involves loading DC with mRNA-encoding neoantigens, which allows for rapid production and is suitable for personalized preparation. Cell-penetrating peptides (CPPs) are emerging as biological delivery systems in which negatively charged nucleic acids can be wound onto the cationic CPP backbone to form nanoscale complexes. This preparation method facilitates standardization. If DC can express and present neoantigen mRNA at high levels, it holds promising application potential. In this study, we developed a neoantigen-mRNA/DC vaccine using candidate neoantigens from mouse colon cancer (MC38) and examined its immune and antitumor effects. The results demonstrated that neoantigen-mRNA/DC vaccines induced strong T cell immune responses and exhibited significant antitumor effects, effectively preventing tumor growth. Our study provides an experimental basis for further optimizing the preparation of DC vaccines and reducing their costs.

Modi-2 a vaccine stimulating CD4 responses to homocitrullinated self epitopes as therapy for solid cancers

Stresses within the tumour microenvironment can mediate post-translational modifications of self-proteins. Homocitrullination is the conversion of lysine to homocitrulline which generates neoepitopes and bypasses self-tolerance. In this study a vaccine targeting homocitrullinated antigens was assessed for stimulation of anti-tumour immunity. Peptides that bind HLA are often hydrophobic which can complicate large scale manufacture and solubility. Here we demonstrate the self-assembling nanoparticle technology (SNAPvaxTM) to co-deliver four homocitrullinated peptides and adjuvant in nanoparticles of a precise size and composition as a vaccine ("Modi-2") that is optimized for manufacturing ease and T cell induction. Strong T cell responses and anti-tumour immunity in mouse tumour models was stimulated against against B16 melanoma (p = 0.0113), CT26 colorectal cancer (p < 0.0001) and 4T1 breast cancer (p = 0.0090). We demonstrate that human lung, colorectal, breast and prostate tumours express the Modi-2 target antigens and propose the Modi-2 vaccine has potential for translation into clinic in several cancer indications.

Neoantigen architectures define immunogenicity and drive immune evasion of tumors with heterogenous neoantigen expression

BACKGROUND

Intratumoral heterogeneity (ITH) and subclonal antigen expression blunt antitumor immunity and are associated with poor responses to immune-checkpoint blockade immunotherapy (ICB) in patients with cancer. The underlying mechanisms however thus far remained elusive, preventing the design of novel treatment approaches for patients with high ITH tumors.

METHODS

We developed a mouse model of lung adenocarcinoma with defined expression of different neoantigens (NeoAg), enabling us to analyze how these impact antitumor T-cell immunity and to study underlying mechanisms. Data from a large cancer patient cohort was used to study whether NeoAg architecture characteristics found to define tumor immunogenicity in our mouse models are linked to ICB responses in patients with cancer.

RESULTS

We demonstrate that concurrent expression and clonality define NeoAg architectures which determine the immunogenicity of individual NeoAg and drive immune evasion of tumors with heterogenous NeoAg expression. Mechanistically, we identified concerted interplays between concurrent T-cell responses induced by cross-presenting dendritic cells (cDC1) mirroring the tumor NeoAg architecture during T-cell priming in the lymph node. Depending on the characteristics and clonality of respective NeoAg, this interplay mutually benefited concurrent T-cell responses or led to competition between T-cell responses to different NeoAg. In tumors with heterogenous NeoAg expression, NeoAg architecture-induced suppression of T-cell responses against branches of the tumor drove immune evasion and caused resistance to ICB. Therapeutic RNA-based vaccination targeting immune-suppressed T-cell responses synergized with ICB to enable control of tumors with subclonal NeoAg expression. A pan-cancer clinical data analysis indicated that competition and synergy between T-cell responses define responsiveness to ICB in patients with cancer.

CONCLUSIONS

NeoAg architectures modulate the immunogenicity of NeoAg and tumors by dictating the interplay between concurrent T-cell responses mediated by cDC1. Impaired induction of T-cell responses supports immune evasion in tumors with heterogenous NeoAg expression but is amenable to NeoAg architecture-informed vaccination, which in combination with ICB portrays a promising treatment approach for patients with tumors exhibiting high ITH.

MDM2 inhibitors in cancer immunotherapy: Current status and perspective

Murine double minute 2 (MDM2) plays an essential role in the cell cycle, apoptosis, DNA repair, and oncogene activation through p53-dependent and p53-independent signaling pathways. Several preclinical studies have shown that MDM2 is involved in tumor immune evasion. Therefore, MDM2-based regulation of tumor cell-intrinsic immunoregulation and the immune microenvironment has attracted increasing research attention. In recent years, immune checkpoint inhibitors targeting PD-1/PD-L1 have been widely used in the clinic. However, the effectiveness of a single agent is only approximately 20%-40%, which may be related to primary and secondary drug resistance caused by the dysregulation of oncoproteins. Here, we reviewed the role of MDM2 in regulating the immune microenvironment, tumor immune evasion, and hyperprogression during immunotherapy. In addition, we summarized preclinical and clinical findings on the use of MDM2 inhibitors in combination with immunotherapy in tumors with MDM2 overexpression or amplification. The results reveal that the inhibition of MDM2 could be a promising strategy for enhancing immunotherapy.

Neoantigen-specific T cell help outperforms non-specific help in multi-antigen DNA vaccination against cancer

CD4+ T helper antigens are essential components of cancer vaccines, but the relevance of the source of these MHC class II-restricted antigens remains underexplored. To compare the effectiveness of tumor-specific versus tumor-unrelated helper antigens, we designed three DNA vaccines for the murine MC-38 colon carcinoma, encoding CD8+ T cell neoantigens alone (noHELP) or in combination with either "universal" helper antigens (uniHELP) or helper neoantigens (neoHELP). Both types of helped vaccines increased the frequency of vaccine-induced CD8+ T cells, and particularly uniHELP increased the fraction of KLRG1+ and PD-1low effector cells. However, when mice were subsequently injected with MC-38 cells, only neoHELP vaccination resulted in significantly better tumor control than noHELP. In contrast to uniHELP, neoHELP-induced tumor control was dependent on the presence of CD4+ T cells, while both vaccines relied on CD8+ T cells. In line with this, neoHELP variants containing wild-type counterparts of the CD4+ or CD8+ T cell neoantigens displayed reduced tumor control. These data indicate that optimal personalized cancer vaccines should include MHC class II-restricted neoantigens to elicit tumor-specific CD4+ T cell help.

Neoantigen-specific cytotoxic Tr1 CD4 T cells suppress cancer immunotherapy

CD4+ T cells can either enhance or inhibit tumour immunity. Although regulatory T cells have long been known to impede antitumour responses1-5, other CD4+ T cells have recently been implicated in inhibiting this response6,7. Yet, the nature and function of the latter remain unclear. Here, using vaccines containing MHC class I (MHC-I) neoantigens (neoAgs) and different doses of tumour-derived MHC-II neoAgs, we discovered that whereas the inclusion of vaccines with low doses of MHC-II-restricted peptides (LDVax) promoted tumour rejection, vaccines containing high doses of the same MHC-II neoAgs (HDVax) inhibited rejection. Characterization of the inhibitory cells induced by HDVax identified them as type 1 regulatory T (Tr1) cells expressing IL-10, granzyme B, perforin, CCL5 and LILRB4. Tumour-specific Tr1 cells suppressed tumour rejection induced by anti-PD1, LDVax or adoptively transferred tumour-specific effector T cells. Mechanistically, HDVax-induced Tr1 cells selectively killed MHC-II tumour antigen-presenting type 1 conventional dendritic cells (cDC1s), leading to low numbers of cDC1s in tumours. We then documented modalities to overcome this inhibition, specifically via anti-LILRB4 blockade, using a CD8-directed IL-2 mutein, or targeted loss of cDC2/monocytes. Collectively, these data show that cytotoxic Tr1 cells, which maintain peripheral tolerance, also inhibit antitumour responses and thereby function to impede immune control of cancer.

Induction of antigen-specific immunity by mesoporous silica nanoparticles incorporating antigen peptides

Mesoporous silica nanoparticles (MSNs) are physically and chemically stable inorganic nanomaterials that have been attracting much attention as carriers for drug delivery systems in the field of nanomedicine. In the present study, we investigated the potential of MSN vaccines that incorporate antigen peptides for use in cancer immunotherapy. In vitro experiments demonstrated that fluorescently labeled MSNs accumulated in a line of mouse dendritic cells (DC2.4 cells), where the particles localized to the cytosol. These observations could suggest that MSNs have potential for use in delivering the loaded molecules into antigen-presenting cells, thereby stimulating the host acquired immune system. In vivo experiments demonstrated prolonged survival in mice implanted with ovalbumin (OVA)-expressing lymphoma cells (E.G7-OVA cells) following subcutaneous inoculation with MSNs incorporating OVA antigen peptides. Furthermore, OVA-specific immunoglobulin G antibodies and cytotoxic T lymphocytes were detected in the serum and the spleen cells, respectively, of mice inoculated with an MSN-OVA vaccine, indicating the induction of antigen-specific responses in both the humoral and cellular immune systems. These results suggested that the MSN therapies incorporating antigen peptides may serve as novel vaccines for cancer immunotherapy.

Immunotherapy-activated T cells recruit and skew late-stage activated M1-like macrophages that are critical for therapeutic efficacy

Total tumor clearance through immunotherapy is associated with a fully coordinated innate and adaptive immune response, but knowledge on the exact contribution of each immune cell subset is limited. We show that therapy-induced intratumoral CD8+ T cells recruited and skewed late-stage activated M1-like macrophages, which were critical for effective tumor control in two different murine models of cancer immunotherapy. The activated CD8+ T cells summon these macrophages into the tumor and their close vicinity via CCR5 signaling. Exposure of non-polarized macrophages to activated T cell supernatant and tumor lysate recapitulates the late-stage activated and tumoricidal phenotype in vitro. The transcriptomic signature of these macrophages is also detected in a similar macrophage population present in human tumors and coincides with clinical response to immune checkpoint inhibitors. The requirement of a functional co-operation between CD8+ T cells and effector macrophages for effective immunotherapy gives warning to combinations with broad macrophage-targeting strategies.

Antimelanoma Effects of Alchemilla vulgaris: A Comprehensive In Vitro and In Vivo Study

Due to the rich ethnobotanical and growing evidence-based medicine records, the Alchemillae herba, i.e., the upper parts of the Lady's mantle (Alchemilla vulgaris L.), was used for the assessment of antimelanoma activity. The ethanolic extract of A. vulgaris strongly suppressed the viability of B16F1, B16F10, 518A2, and Fem-X cell lines. In contrast to the in vitro study, where the B16F1 cells were more sensitive to the treatment than the more aggressive counterpart B16F10, the results obtained in vivo using the corresponding syngeneic murine model were quite the opposite. The higher sensitivity of B16F10 tumors in vivo may be attributed to a more complex response to the extract compared to one triggered in vitro. In addition, the strong immunosuppressive microenvironment in the B16F1 model is impaired by the treatment, as evidenced by enhanced antigen-presenting potential of dendritic cells, influx and activity of CD4+ T and CD8+ T lymphocytes, decreased presence of T regulatory lymphocytes, and attenuation of anti-inflammatory cytokine production. All these effects are supported by the absence of systemic toxicity. A. vulgaris extract treatment results in a sustained and enhanced ability to reduce melanoma growth, followed by the restoration of innate and adopted antitumor immunity without affecting the overall physiology of the host.

High production of IL-12 by human dendritic cells stimulated with combinations of pattern-recognition receptor agonists

The cytokine IL-12p70 is crucial for T helper 1 (Th1) polarization and the generation of type 1 immunity required to fight cancer and pathogens. Therefore, strategies to optimize the production of IL-12p70 by human dendritic cells (DCs) may significantly improve the efficacy of vaccines and immunotherapies. However, the rules governing the production of IL-12p70 remain obscure. Here, we stimulated pattern recognition receptors (PRRs) representing five families of PRRs, to evaluate their ability to elicit high production of IL-12p70 by monocyte-derived DCs. We used ten well-characterized agonists and stimulated DCs in vitro with either single agonists or 27 different combinations. We found that poly(I:C), which engages the RNA-sensing PRRs TLR3 and MDA5, and LPS which stimulates TLR4, were the only agonists that could elicit notable IL-12p70 production when used as single ligands. We identified six different combinations of PRR agonists, all containing either the TLR3/MDA5 agonist poly(I:C) or the TLR7/8 agonist R848, that could synergize to elicit high production of IL-12p70 by human DCs. Five of the six combinations also triggered high production of the antiviral and antitumor cytokine IFNβ. Overall, the tested PRR ligands could be divided into three groups depending on whether they triggered production of both IL-12p70 and IFNβ, only one of the two, or neither. Thus, combinations of PRR agonists were found to increase the production of IL-12p70 by human DCs in a synergistic manner, and we identified six PRR agonist combinations that may represent strong adjuvant candidates, in particular for therapeutic cancer vaccines.

Divergent HLA variations and heterogeneous expression but recurrent HLA loss-of- heterozygosity and common HLA-B and TAP transcriptional silencing across advanced pediatric solid cancers

The human leukocyte antigen (HLA) system is a major factor controlling cancer immunosurveillance and response to immunotherapy, yet its status in pediatric cancers remains fragmentary. We determined high-confidence HLA genotypes in 576 children, adolescents and young adults with recurrent/refractory solid tumors from the MOSCATO-01 and MAPPYACTS trials, using normal and tumor whole exome and RNA sequencing data and benchmarked algorithms. There was no evidence for narrowed HLA allelic diversity but discordant homozygosity and allele frequencies across tumor types and subtypes, such as in embryonal and alveolar rhabdomyosarcoma, neuroblastoma MYCN and 11q subtypes, and high-grade glioma, and several alleles may represent protective or susceptibility factors to specific pediatric solid cancers. There was a paucity of somatic mutations in HLA and antigen processing and presentation (APP) genes in most tumors, except in cases with mismatch repair deficiency or genetic instability. The prevalence of loss-of-heterozygosity (LOH) ranged from 5.9 to 7.7% in HLA class I and 8.0 to 16.7% in HLA class II genes, but was widely increased in osteosarcoma and glioblastoma (~15-25%), and for DRB1-DQA1-DQB1 in Ewing sarcoma (~23-28%) and low-grade glioma (~33-50%). HLA class I and HLA-DR antigen expression was assessed in 194 tumors and 44 patient-derived xenografts (PDXs) by immunochemistry, and class I and APP transcript levels quantified in PDXs by RT-qPCR. We confirmed that HLA class I antigen expression is heterogeneous in advanced pediatric solid tumors, with class I loss commonly associated with the transcriptional downregulation of HLA-B and transporter associated with antigen processing (TAP) genes, whereas class II antigen expression is scarce on tumor cells and occurs on immune infiltrating cells. Patients with tumors expressing sufficient HLA class I and TAP levels such as some glioma, osteosarcoma, Ewing sarcoma and non-rhabdomyosarcoma soft-tissue sarcoma cases may more likely benefit from T cell-based approaches, whereas strategies to upregulate HLA expression, to expand the immunopeptidome, and to target TAP-independent epitopes or possibly LOH might provide novel therapeutic opportunities in others. The consequences of HLA class II expression by immune cells remain to be established. Immunogenetic profiling should be implemented in routine to inform immunotherapy trials for precision medicine of pediatric cancers.

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.

Bidirectional crosstalk between therapeutic cancer vaccines and the tumor microenvironment: Beyond tumor antigens

Immunotherapy has rejuvenated cancer therapy, especially after anti-PD-(L)1 came onto the scene. Among the many therapeutic options, therapeutic cancer vaccines are one of the most essential players. Although great progress has been made in research on tumor antigen vaccines, few phase III trials have shown clinical benefits. One of the reasons lies in obstruction from the tumor microenvironment (TME). Meanwhile, the therapeutic cancer vaccine reshapes the TME in an ambivalent way, leading to immune stimulation or immune escape. In this review, we summarize recent progress on the interaction between therapeutic cancer vaccines and the TME. With respect to vaccine resistance, innate immunosuppressive TME components and acquired resistance caused by vaccination are both involved. Understanding the underlying mechanism of this crosstalk provides insight into the treatment of cancer by directly targeting the TME or synergizing with other therapeutics.

Controlling Antigen Fate in Therapeutic Cancer Vaccines by Targeting Dendritic Cell Receptors

Antigen-presenting cells (APCs) orchestrate immune responses and are therefore of interest for the targeted delivery of therapeutic vaccines. Dendritic cells (DCs) are professional APCs that excel in presentation of exogenous antigens toward CD4+ T helper cells, as well as cytotoxic CD8+ T cells. DCs are highly heterogeneous and can be divided into subpopulations that differ in abundance, function, and phenotype, such as differential expression of endocytic receptor molecules. It is firmly established that targeting antigens to DC receptors enhances the efficacy of therapeutic vaccines. While most studies emphasize the importance of targeting a specific DC subset, we argue that the differential intracellular routing downstream of the targeted receptors within the DC subset should also be considered. Here, we review the mouse and human receptors studied as target for therapeutic vaccines, focusing on antibody and ligand conjugates and how their targeting affects antigen presentation. We aim to delineate how targeting distinct receptors affects antigen presentation and vaccine efficacy, which will guide target selection for future therapeutic vaccine development.

The role of CD4+ T cells in tumor and chronic viral immune responses

Immunotherapies are mainly aimed to promote a CD8+ T cell response rather than a CD4+ T cell response as cytotoxic T lymphocytes (CTLs) can directly kill target cells. Recently, CD4+ T cells have received more attention due to their diverse roles in tumors and chronic viral infections. In antitumor and antichronic viral responses, CD4+ T cells relay help signals through dendritic cells to indirectly regulate CD8+ T cell response, interact with B cells or macrophages to indirectly modulate humoral immunity or macrophage polarization, and inhibit tumor blood vessel formation. Additionally, CD4+ T cells can also exhibit direct cytotoxicity toward target cells. However, regulatory T cells exhibit immunosuppression and CD4+ T cells become exhausted, which promote tumor progression and chronic viral persistence. Finally, we also outline immunotherapies based on CD4+ T cells, including adoptive cell transfer, vaccines, and immune checkpoint blockade. Overall, this review summarizes diverse roles of CD4+ T cells in the antitumor or protumor and chronic viral responses, and also highlights the immunotherapies based on CD4+ T cells, giving a better understanding of their roles in tumors and chronic viral infections.

Improving the efficacy of peptide vaccines in cancer immunotherapy

Peptide vaccines have shown great potential in cancer immunotherapy by targeting tumor antigens and activating the patient's immune system to mount a specific response against cancer cells. However, the efficacy of peptide vaccines in inducing a sustained immune response and achieving clinical benefit remains a major challenge. In this review, we discuss the current status of peptide vaccines in cancer immunotherapy and strategies to improve their efficacy. We summarize the recent advancements in the development of peptide vaccines in pre-clinical and clinical settings, including the use of novel adjuvants, neoantigens, nano-delivery systems, and combination therapies. We also highlight the importance of personalized cancer vaccines, which consider the unique genetic and immunological profiles of individual patients. We also discuss the strategies to enhance the immunogenicity of peptide vaccines such as multivalent peptides, conjugated peptides, fusion proteins, and self-assembled peptides. Although, peptide vaccines alone are weak immunogens, combining peptide vaccines with other immunotherapeutic approaches and developing novel approaches such as personalized vaccines can be promising methods to significantly enhance their efficacy and improve the clinical outcomes for cancer patients.

Linked CD4+/CD8+ T cell neoantigen vaccination overcomes immune checkpoint blockade resistance and enables tumor regression

Therapeutic benefit to immune checkpoint blockade (ICB) is currently limited to the subset of cancers thought to possess a sufficient tumor mutational burden (TMB) to allow for the spontaneous recognition of neoantigens (NeoAg) by autologous T cells. We explored whether the response to ICB of an aggressive low-TMB squamous cell tumor could be improved through combination immunotherapy using functionally defined NeoAg as targets for endogenous CD4+ and CD8+ T cells. We found that, whereas vaccination with CD4+ or CD8+ NeoAg alone did not offer prophylactic or therapeutic immunity, vaccines containing NeoAg recognized by both subsets overcame ICB resistance and led to the eradication of large established tumors that contained a subset of PD-L1+ tumor-initiating cancer stem cells (tCSC), provided the relevant epitopes were physically linked. Therapeutic CD4+/CD8+ T cell NeoAg vaccination produced a modified tumor microenvironment (TME) with increased numbers of NeoAg-specific CD8+ T cells existing in progenitor and intermediate exhausted states enabled by combination ICB-mediated intermolecular epitope spreading. We believe that the concepts explored herein should be exploited for the development of more potent personalized cancer vaccines that can expand the range of tumors treatable with ICB.

Neutrophil extracellular traps-related signature predicts the prognosis and immune infiltration in gastric cancer

Introduction

Gastric cancer (GC) is the fifth most prevalent cancer globally, with the third highest case fatality rate. Neutrophil extracellular traps (NETs) are a reticulated structure of DNA, histones, and antimicrobial peptides produced by active neutrophils that trap pathogens. Even though NETs are associated with poorer recurrence-free survival (RFS) and overall survival (OS), the specifics of this interaction between NETs and cancer cells are yet unknown.

Methods

The keywords "neutrophil extracellular traps and gastric cancer" were used in the GEO database for retrieval, and the GSE188741 dataset was selected to obtain the NETs-related gene. 27 NETs-related genes were screened by univariate Cox regression analysis (p < 0.05). 27 NETs-related genes were employed to identify and categorize NETs-subgroups of GC patients under the Consensus clustering analysis. 808 GC patients in TCGA-STAD combined with GES84437 were randomly divided into a training group (n = 403) and a test group (n = 403) at a ratio of 1:1 to validate the NETs-related signature.

Results

Based on Multivariate Cox regression and LASSO regression analysis to develop a NETs-related prognosis model. We developed a very specific nomogram to improve the NETs-clinical score's usefulness. Similarly, we also performed a great result in pan-cancer study with NETs-score. Low NETs scores were linked to higher MSI-H (microsatellite instability-high), mutation load, and immune activity. The cancer stem cell (CSC) index and chemotherapeutic treatment sensitivity were also connected to the NET score. Our comprehensive analysis of NETs in GC suggests that NETs have a role in the tumor microenvironment, clinicopathological features, and prognosis.

Discussion

The NETs-score risk model provides a basis for better prognosis and therapy outcomes in GC patients.

Insight into Cancer Immunity: MHCs, Immune Cells and Commensal Microbiota

Cancer cells circumvent immune surveillance via diverse strategies. In accordance, a large number of complex studies of the immune system focusing on tumor cell recognition have revealed new insights and strategies developed, largely through major histocompatibility complexes (MHCs). As one of them, tumor-specific MHC-II expression (tsMHC-II) can facilitate immune surveillance to detect tumor antigens, and thereby has been used in immunotherapy, including superior cancer prognosis, clinical sensitivity to immune checkpoint inhibition (ICI) therapy and tumor-bearing rejection in mice. NK cells play a unique role in enhancing innate immune responses, accounting for part of the response including immunosurveillance and immunoregulation. NK cells are also capable of initiating the response of the adaptive immune system to cancer immunotherapy independent of cytotoxic T cells, clearly demonstrating a link between NK cell function and the efficacy of cancer immunotherapies. Eosinophils were shown to feature pleiotropic activities against a variety of solid tumor types, including direct interactions with tumor cells, and accessorily affect immunotherapeutic response through intricating cross-talk with lymphocytes. Additionally, microbial sequencing and reconstitution revealed that commensal microbiota might be involved in the modulation of cancer progression, including positive and negative regulatory bacteria. They may play functional roles in not only mucosal modulation, but also systemic immune responses. Here, we present a panorama of the cancer immune network mediated by MHCI/II molecules, immune cells and commensal microbiota and a discussion of prospective relevant intervening mechanisms involved in cancer immunotherapies.

Principles of Molecular Utility for CMS Classification in Colorectal Cancer Management

Colorectal cancer (CRC) is the second cause of cancer-related deaths in both sexes globally and presents different clinical outcomes that are described by a range of genomic and epigenomic alterations. Despite the advancements in CRC screening plans and treatment strategies, the prognosis of CRC is dismal. In the last two decades, molecular biomarkers predictive of prognosis have been identified in CRC, although biomarkers predictive of treatment response are only available for specific biological drugs used in stage IV CRC. Translational clinical trials mainly based on "omic" strategies allowed a better understanding of the biological heterogeneity of CRCs. These studies were able to classify CRCs into subtypes mainly related to prognosis, recurrence risk, and, to some extent, also to treatment response. Accordingly, the comprehensive molecular characterizations of CRCs, including The Cancer Genome Atlas (TCGA) and consensus molecular subtype (CMS) classifications, were presented to improve the comprehension of the genomic and epigenomic landscapes of CRCs for a better patient management. The CMS classification obtained by the CRC subtyping consortium categorizes CRC into four consensus molecular subtypes (CMS1-4) characterized by different prognoses. In this review, we discussed the CMS classification in different settings with a focus on its relationships with precursor lesions, tumor immunophenotype, and gut microbiota, as well as on its role in predicting prognosis and/or response to pharmacological treatments, as a crucial step towards precision medicine.

Linked CD4 + /CD8 + T cell neoantigen vaccination overcomes immune checkpoint blockade resistance and enables tumor regression

Therapeutic benefit to immune checkpoint blockade (ICB) is currently limited to the subset of cancers thought to possess a sufficient tumor mutational burden (TMB) to allow for the spontaneous recognition of neoantigens (NeoAg) by autologous T cells. We explored whether the response of an aggressive low TMB squamous cell tumor to ICB could be improved through combination immunotherapy using functionally defined NeoAg as targets for endogenous CD4 + and CD8 + T cells. We found that, whereas vaccination with CD4 + or CD8 + NeoAg alone did not offer prophylactic or therapeutic immunity, vaccines containing NeoAg recognized by both subsets overcame ICB resistance and led to the eradication of large established tumors that contained a subset of PD-L1 + tumor-initiating cancer stem cells (tCSC), provided the relevant epitopes were physically linked. Therapeutic CD4 + /CD8 + T cell NeoAg vaccination produced a modified tumor microenvironment (TME) with increased numbers of NeoAg-specific CD8 + T cells existing in progenitor and intermediate exhausted states enabled by combination ICB-mediated intermolecular epitope spreading. The concepts explored herein should be exploited for the development of more potent personalized cancer vaccines that can expand the range of tumors treatable with ICB.

Chlorin e6-associated photodynamic therapy enhances abscopal antitumor effects via inhibition of PD-1/PD-L1 immune checkpoint

We hypothesized that photodynamic therapy (PDT) with Chlorin e6 (Ce6) enhances antitumor abscopal effects via inhibition of the programmed cell death-1/programmed death-ligand 1 (PD-1/PD-L1) immune checkpoint. By using syngeneic melanoma and pancreatic tumor mouse models, we studied the Ce6-PDT-induced immune responses in local and distant tumor microenvironments. In addition, the Ce6-PDT's target in the PD-1/PD-L1 interaction was analyzed in MC38-hPD-L1 colon cancer and PD-1 expressing Jurkat T cell coculture. The tumors in the irradiated and non-irradiated sites in the abscopal effective (Abs_eff) group of both mouse models were regressed, proving the abscopal effect. The immunogenic effect in the Abs_eff group was associated with an expansion of T cell and other immune cells infiltration without changes in the CD39⁺ population in either the right or left tumors compared to control group. Furthermore, the abscopal ineffective (Abs_ineff) group demonstrated lesser increase of T cells, decreased immune cell infiltration, and increased CD39-expressing Treg cells without suppression of tumor growth. In the coculture with PD-1-expressing Jurkat T cell, Ce6-PDT efficiently suppressed the PD-1/PD-L1 interactions by increasing the proliferation and cytotoxic activity of CD8⁺ T cells while decreasing CD39-expressing Treg cells in a dose-dependent manner. Likewise, the inhibition of PD-1/PD-L1 interactions was also correlated with the increased production of IL-2 and Granzyme B. Our findings imply that Ce6-PDT is a promising immunotherapy with the potential to improve the abscopal effect.

The impact of microbiome dysbiosis on T cell function within the tumor microenvironment (TME)

Insights into the effect of the microbiome’s composition on immune cell function have recently been discerned and further characterized. Microbiome dysbiosis can result in functional alterations across immune cells, including those required for innate and adaptive immune responses to malignancies and immunotherapy treatment. Dysbiosis can yield changes in or elimination of metabolite secretions, such as short-chain fatty acids (SCFAs), from certain bacterial species that are believed to impact proper immune cell function. Such alterations within the tumor microenvironment (TME) can significantly affect T cell function and survival necessary for eliminating cancerous cells. Understanding these effects is essential to improve the immune system’s ability to fight malignancies and the subsequent efficacy of immunotherapies that rely on T cells. In this review, we assess typical T cell response to malignancies, classify the known impact of the microbiome and particular metabolites on T cells, discuss how dysbiosis can affect their function in the TME then further describe the impact of the microbiome on T cell-based immunotherapy treatment, with an emphasis on recent developments in the field. Understanding the impact of dysbiosis on T cell function within the TME can carry substantial implications for the design of immunotherapy treatments and further our understanding of factors that could impact how the immune system combats malignancies.

Citrullinated glucose-regulated protein 78 is a candidate target for melanoma immunotherapy

Introduction

Post translational modification of proteins plays a significant role in immune recognition. In particular the modification of arginine to citrulline which is mediated by PAD enzymes is increased during cellular stress (autophagy) which permits the presentation of modified epitopes upon MHC class II molecules for recognition by CD4 T cells. Citrullination also occurs in tumour cells as a result of continuous environmental stresses and increased autophagy. We have shown in animal models the efficient stimulation of citrullinated epitope specific CD4 T cells resulting in dramatic elimination/regression of tumours. The ER chaperone glucose-regulated protein 78 (GRP78) is known to also be required for stress-induced autophagy and is directly linked to autophagosome formation. GRP78 is known to be highly expressed by many tumour types. In this study we investigate the potential of targeting citrullinated GRP78 for cancer therapy.

Methods

A citrullinated GRP78 specific antibody was used to assess citrullinated GRP78 expression in murine and human tumour cells by flow cytometry. Five peptides were selected and used to vaccinate HLA transgenic mice and immune responses were characterised by ex vivo cytokine ELISpot assay. T cell repertoire in humans was assessed through proliferation assays and cytokine ELISpot assay. Citrullinated peptide was identified in murine B16 melanoma by mass spectrometry and the peptide vaccine was assessed for tumour therapy in a mouse melanoma model.

Results

We show the identification CD4 T cell responses to one citrullinated GRP78 epitope that are restricted through HLA DP*0401 and HLA-DR*0101 alleles. This peptide is detected by mass spectrometry in B16 melanoma grown in vivo and citrulline specific CD4 responses to two peptides spanning this epitope mediate efficient therapy of established B16 melanoma tumours in HHDII/DP4 (p<0.0001) transgenic mouse model. Finally, we demonstrate the existence of a repertoire of responses to the citrullinated GRP78 peptide in healthy individuals (p=0.0023) with 13/17 (76%) individuals showing a response to this peptide.

Conclusion

We propose that citrullinated GRP78 is a candidate tumour antigen and vaccination against citrullinated GRP78 may provide a promising tumour therapy approach.

Arginase-2-specific cytotoxic T cells specifically recognize functional regulatory T cells

Background

High expression of the metabolic enzyme arginase-2 (ARG2) by cancer cells, regulatory immune cells, or cells of the tumor stroma can reduce the availability of arginine (L-Arg) in the tumor microenvironment (TME). Depletion of L-Arg has detrimental consequences for T cells and leads to T-cell dysfunction and suppression of anticancer immune responses. Previous work from our group has demonstrated the presence of proinflammatory ARG2-specific CD4 T cells that inhibited tumor growth in murine models on activation with ARG2-derived peptides. In this study, we investigated the natural occurrence of ARG2-specific CD8 T cells in both healthy donors (HDs) and patients with cancer, along with their immunomodulatory capabilities in the context of the TME.

Materials and methods

A library of 15 major histocompatibility complex (MHC) class I-restricted ARG2-derived peptides were screened in HD peripheral blood mononuclear cells using interferon gamma (IFN-γ) ELISPOT. ARG2-specific CD8 T-cell responses were identified using intracellular cytokine staining and ARG2-specific CD8 T-cell cultures were established by enrichment and rapid expansion following in vitro peptide stimulation. The reactivity of the cultures toward ARG2-expressing cells, including cancer cell lines and activated regulatory T cells (Tregs), was assessed using IFN-γ ELISPOT and a chromium release assay. The Treg signature was validated based on proliferation suppression assays, flow cytometry and quantitative reverse transcription PCR (RT-qPCR). In addition, vaccinations with ARG2-derived epitopes were performed in the murine Pan02 tumor model, and induction of ARG2-specific T-cell responses was evaluated with IFN-γ ELISPOT. RNAseq and subsequent GO-term and ImmuCC analysis was performed on the tumor tissue.

Results

We describe the existence of ARG2-specific CD8⁺ T cells and demonstrate these CD8⁺ T-cell responses in both HDs and patients with cancer. ARG2-specific T cells recognize and react to an ARG2-derived peptide presented in the context of HLA-B8 and exert their cytotoxic function against cancer cells with endogenous ARG2 expression. We demonstrate that ARG2-specific T cells can specifically recognize and react to activated Tregs with high ARG2 expression. Finally, we observe tumor growth suppression and antitumorigenic immunomodulation following ARG2 vaccination in an in vivo setting.

Conclusion

These findings highlight the ability of ARG2-specific T cells to modulate the immunosuppressive TME and suggest that ARG2-based immunomodulatory vaccines may be an interesting option for cancer immunotherapy.

Peptide emulsions in incomplete Freund's adjuvant create effective nurseries promoting egress of systemic CD4+ and CD8+ T cells for immunotherapy of cancer

Water-in-oil emulsion incomplete Freund's adjuvant (IFA) has been used as an adjuvant in preventive and therapeutic vaccines since its development. New generation, highly purified modulations of the adjuvant, Montanide incomplete seppic adjuvant (ISA)-51 and Montanide ISA-720, were developed to reduce toxicity. Montanide adjuvants are generally considered to be safe, with adverse events largely consisting of antigen and adjuvant dose-dependent injection site reactions (ISRs). Peptide vaccines in Montanide ISA-51 or ISA-720 are capable of inducing both high antibody titers and durable effector T cell responses. However, an efficient T cell response depends on the affinity of the peptide to the presenting major histocompatibility complex class I molecule, CD4⁺ T cell help and/or the level of co-stimulation. In fact, in the therapeutic cancer vaccine setting, presence of a CD4⁺ T cell epitope seems crucial to elicit a robust and durable systemic T cell response. Additional inclusion of a Toll-like receptor ligand can further increase the magnitude and durability of the response. Use of extended peptides that need a processing step only accomplished effectively by dendritic cells (DCs) can help to avoid antigen presentation by nucleated cells other than DC. Based on recent clinical trial results, therapeutic peptide-based cancer vaccines using emulsions in adjuvant Montanide ISA-51 can elicit robust antitumor immune responses, provided that sufficient tumor-specific CD4⁺ T cell help is given in addition to CD8⁺ T cell epitopes. Co-treatment with PD-1 T cell checkpoint inhibitor, chemotherapy or other immunomodulatory drugs may address local and systemic immunosuppressive mechanisms, and further enhance efficacy of therapeutic cancer peptide vaccines in IFA and its modern variants. Blinded randomized placebo-controlled trials are critical to definitively prove clinical efficacy. Mineral oil-based adjuvants for preventive vaccines, to tackle spread and severity of infectious disease, induce immune responses, but require more studies to reduce toxicity.

Lipid A analog CRX-527 conjugated to synthetic peptides enhances vaccination efficacy and tumor control

Adjuvants play a determinant role in cancer vaccination by optimally activating APCs and shaping the T cell response. Bacterial-derived lipid A is one of the most potent immune-stimulators known, and is recognized via Toll-like receptor 4 (TLR4). In this study, we explore the use of the synthetic, non-toxic, lipid A analog CRX-527 as an adjuvant for peptide cancer vaccines. This well-defined adjuvant was covalently conjugated to antigenic peptides as a strategy to improve vaccine efficacy. We show that coupling of this TLR4 agonist to peptide antigens improves vaccine uptake by dendritic cells (DCs), maturation of DCs and T cell activation in vitro, and stimulates DC migration and functional T cell priming in vivo. This translates into enhanced tumor protection upon prophylactic and therapeutic vaccination via intradermal injection against B16-OVA melanoma and HPV-related TC1 tumors. These results highlight the potential of CRX-527 as an adjuvant for molecularly defined cancer vaccines, and support the design of adjuvant-peptide conjugates as a strategy to optimize vaccine formulation.

High GILT Expression Is Associated with Improved Survival in Metastatic Melanoma Patients Treated with Immune Checkpoint Inhibition

Simple Summary

Skin cancer is the most common type of cancer, with melanoma being among the deadliest of skin cancers due to its propensity to metastasize. Immune checkpoint inhibitors (ICI) generate anti-tumor immune responses resulting in improved outcomes in patients with metastatic melanoma. However, only a subset of melanoma patients responds to these therapies, which are costly and come with a risk of adverse effects. Therefore, there is a need for biomarkers to predict which patients will respond to ICI. We found that ICI-treated metastatic melanoma patients with high GILT mRNA expression in bulk tumor samples had improved survival. Additionally, high GILT protein expression within metastatic melanoma cells was associated with improved survival in patients treated with ICI. This study suggests that GILT may serve as a biomarker to predict which patients will respond to ICI, which could improve patient care, reduce healthcare costs, and facilitate appropriate selection of therapies for patients with metastatic melanoma.

Abstract

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is critical for MHC class II restricted presentation of multiple melanoma antigens. There is variable GILT protein expression in malignant melanocytes in melanoma specimens. High GILT mRNA expression in melanoma specimens is associated with improved overall survival, before the advent of immune checkpoint inhibitors (ICI). However, the association of GILT in metastatic melanoma with survival in patients treated with ICI and the cell type expressing GILT associated with survival have not been determined. Using RNA sequencing datasets, high GILT mRNA expression in metastatic melanoma specimens was associated with improved progression-free and overall survival in patients treated with ICI. A clinical dataset of metastatic melanoma specimens was generated and annotated with clinical information. Positive GILT immunohistochemical staining in antigen presenting cells and melanoma cells was observed in 100% and 65% of metastatic melanoma specimens, respectively. In the subset of patients treated with ICI in the clinical dataset, high GILT protein expression within melanoma cells was associated with improved overall survival. The association of GILT mRNA and protein expression with survival was independent of cancer stage. These studies support that high GILT mRNA expression in bulk tumor samples and high GILT protein expression in melanoma cells is associated with improved survival in ICI-treated patients. These findings support further investigation of GILT as a biomarker to predict the response to ICI.

Neoantigen-specific CD4+ T cells in human melanoma have diverse differentiation states and correlate with CD8+ T cell, macrophage, and B cell function

CD4⁺ T cells that recognize tumor antigens are required for immune checkpoint inhibitor efficacy in murine models, but their contributions in human cancer are unclear. We used single-cell RNA sequencing and T cell receptor sequences to identify signatures and functional correlates of tumor-specific CD4⁺ T cells infiltrating human melanoma. Conventional CD4⁺ T cells that recognize tumor neoantigens express CXCL13 and are subdivided into clusters expressing memory and T follicular helper markers, and those expressing cytolytic markers, inhibitory receptors, and IFN-γ. The frequency of CXCL13⁺ CD4⁺ T cells in the tumor correlated with the transcriptional states of CD8⁺ T cells and macrophages, maturation of B cells, and patient survival. Similar correlations were observed in a breast cancer cohort. These results identify phenotypes and functional correlates of tumor-specific CD4⁺ T cells in melanoma and suggest the possibility of using such cells to modify the tumor microenvironment.

NeoScore Integrates Characteristics of the Neoantigen:MHC Class I Interaction and Expression to Accurately Prioritize Immunogenic Neoantigens

Accurate prioritization of immunogenic neoantigens is key to developing personalized cancer vaccines and distinguishing those patients likely to respond to immune checkpoint inhibition. However, there is no consensus regarding which characteristics best predict neoantigen immunogenicity, and no model to date has both high sensitivity and specificity and a significant association with survival in response to immunotherapy. We address these challenges in the prioritization of immunogenic neoantigens by (1) identifying which neoantigen characteristics best predict immunogenicity; (2) integrating these characteristics into an immunogenicity score, the NeoScore; and (3) demonstrating a significant association of the NeoScore with survival in response to immune checkpoint inhibition. One thousand random and evenly split combinations of immunogenic and nonimmunogenic neoantigens from a validated dataset were analyzed using a regularized regression model for characteristic selection. The selected characteristics, the dissociation constant and binding stability of the neoantigen:MHC class I complex and expression of the mutated gene in the tumor, were integrated into the NeoScore. A web application is provided for calculation of the NeoScore. The NeoScore results in improved, or equivalent, performance in four test datasets as measured by sensitivity, specificity, and area under the receiver operator characteristics curve compared with previous models. Among cutaneous melanoma patients treated with immune checkpoint inhibition, a high maximum NeoScore was associated with improved survival. Overall, the NeoScore has the potential to improve neoantigen prioritization for the development of personalized vaccines and contribute to the determination of which patients are likely to respond to immunotherapy.

Peptides for Vaccine Development

This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.

Neoantigen vaccine-induced CD4 T cells confer protective immunity in a mouse model of multiple myeloma through activation of CD8 T cells against non-vaccine, tumor-associated antigens

Background

Cancer-associated neoantigens (neoAg) derived from tumor genomic sequencing and predictive algorithms for mutated peptides are a promising basis for therapeutic vaccines under investigation. Although these are generally designed to bind major histocompatibility complex class I and induce CD8 cytolytic T lymphocyte (CTL) activity, results from preclinical and clinical studies demonstrate that the majority of neoAg vaccines efficiently induce CD4 T helper (Th) responses but not CTL. Despite this, these vaccines have demonstrated clinical efficacy. Therefore, understanding the mechanisms of CD4 + T cell-mediated tumor protection is critical to optimizing this immunotherapeutic strategy.

Methods

We investigated this phenomenon in the mineral oil-induced plasmacytoma (MOPC).315.BM (MOPC315) mouse model of multiple myeloma, a malignancy of plasma cells. MOPC315 cells express in their lambda chain a unique tumor-specific neoAg, an idiotypic (Id) peptide. We generated a vaccine formulated with this Id peptide fused to a heat shock protein HSC70 binding (HSB) motif co-delivered with poly (I:C). The immunogenicity of the Id-vaccine was measured in splenocytes by ELISpot. Mice were challenged with MOPC315 cells and antitumor immunity was assessed by co-incubating splenocytes and bone marrow mononuclear cells derived from vaccinated mice and controls, with the Id antigen and irradiated MOPC315 cells. The frequency of activated CD4 and CD8 T cells and their phenotype were characterized by flow cytometry.

Results

Id-vaccine efficiently induced antigen-specific CD4 Th activity and antitumor immunity, protecting mice from MOPC315 tumor growth. CD4 cytolytic activity was not detected under these conditions. Polyfunctional CD8 T cells homed to the bone marrow microenvironment of protected mice and preferentially expanded only when restimulated ex vivo with both Id peptide and MOPC315 cells. Protective activity was abrogated by depletion of either CD4 or CD8 lymphocytes.

Conclusion

These results demonstrate that Id-HSB +poly (I:C) vaccine protects against MOPC315 growth by priming Id-specific CD4 Th cells that confer protection against tumor but are not directly cytotoxic. These data indicate that activation of CD8 CTL against MOPC315-associated antigens not present in the vaccine is one of the major mechanisms of tumor immunity.

T-cell Receptor Therapy Targeting Mutant Capicua Transcriptional Repressor in Experimental Gliomas

PURPOSE

Gliomas are intrinsic brain tumors with a high degree of constitutive and acquired resistance to standard therapeutic modalities such as radiotherapy and alkylating chemotherapy. Glioma subtypes are recognized by characteristic mutations. Some of these characteristic mutations have shown to generate immunogenic neoepitopes suitable for targeted immunotherapy.

EXPERIMENTAL DESIGN

Using peptide-based ELISpot assays, we screened for potential recurrent glioma neoepitopes in MHC-humanized mice. Following vaccination, droplet-based single-cell T-cell receptor (TCR) sequencing from established T-cell lines was applied for neoepitope-specific TCR discovery. Efficacy of intraventricular TCR-transgenic T-cell therapy was assessed in a newly developed glioma model in MHC-humanized mice induced by CRISPR-based delivery of tumor suppressor-targeting guide RNAs.

RESULTS

We identify recurrent capicua transcriptional repressor (CIC) inactivating hotspot mutations at position 215 CICR215W/Q as immunogenic MHC class II (MHCII)-restricted neoepitopes. Vaccination of MHC-humanized mice resulted in the generation of robust MHCII-restricted mutation-specific T-cell responses against CICR215W/Q. Adoptive intraventricular transfer of CICR215W-specific TCR-transgenic T cells exert antitumor responses against CICR215W-expressing syngeneic gliomas.

CONCLUSIONS

The integration of immunocompetent MHC-humanized orthotopic glioma models in the discovery of shared immunogenic glioma neoepitopes facilitates the identification and preclinical testing of human leukocyte antigen (HLA)-restricted neoepitope-specific TCRs for locoregional TCR-transgenic T-cell adoptive therapy.

The Immune Landscape of Human Primary Lung Tumors Is Th2 Skewed

Tumor-specific T helper (Th) cells have a central role in the immune response against cancer. However, there exist distinct Th cell subsets with very different and antagonizing properties. Some Th subsets such as Th1 protect against cancer, while others (Th2, T regulatory/Treg) are considered detrimental or of unknown significance (T follicular helper/Tfh, Th17). The Th composition of human solid tumors remains poorly characterized. Therefore, we established a four-color multiplex chromogenic immunohistochemical assay for detection of Th1, Th2, Th17, Tfh and Treg cells in human tumor sections. The method was used to analyze resected primary lung tumors from 11 patients with non-small cell lung cancer (NSCLC). Four microanatomical regions were investigated: tumor epithelium, tumor stroma, peritumoral tertiary lymphoid structures (TLS) and non-cancerous distal lung tissue. In tumor epithelium and stroma, most CD4⁺ T cells identified had either a Th2 (GATA-3⁺CD3⁺CD8^-) or Treg (FOXP3⁺CD3⁺CD8^-) phenotype, whereas only low numbers of Th1, Th17, and Tfh cells were observed. Similarly, Th2 was the most abundant Th subset in TLS, followed by Treg cells. In sharp contrast, Th1 was the most frequently detected Th subset in non-cancerous lung tissue from the same patients. A higher Th1:Th2 ratio in tumor stroma was found to be associated with increased numbers of intratumoral CD8⁺ T cells. The predominance of Th2 and Treg cells in both tumor stroma and tumor epithelium was consistent for all the 11 patients investigated. We conclude that human primary NSCLC tumors are Th2-skewed and contain numerous Treg cells. If human tumors are Th2-skewed, as our data in NSCLC suggest, reprogramming the type of immune response from a detrimental Th2 to a beneficial Th1 may be critical to increase the response rate of immunotherapy.

MS-Based HLA-II Peptidomics Combined With Multiomics Will Aid the Development of Future Immunotherapies

Immunotherapies have emerged to treat diseases by selectively modulating a patient's immune response. Although the roles of T and B cells in adaptive immunity have been well studied, it remains difficult to select targets for immunotherapeutic strategies. Because human leukocyte antigen class II (HLA-II) peptides activate CD4+ T cells and regulate B cell activation, proliferation, and differentiation, these peptide antigens represent a class of potential immunotherapy targets and biomarkers. To better understand the molecular basis of how HLA-II antigen presentation is involved in disease progression and treatment, systematic HLA-II peptidomics combined with multiomic analyses of diverse cell types in healthy and diseased states is required. For this reason, MS-based innovations that facilitate investigations into the interplay between disease pathologies and the presentation of HLA-II peptides to CD4+ T cells will aid in the development of patient-focused immunotherapies.

Therapeutic cancer vaccines

Therapeutic cancer vaccines have undergone a resurgence in the past decade. A better understanding of the breadth of tumour-associated antigens, the native immune response and development of novel technologies for antigen delivery has facilitated improved vaccine design. The goal of therapeutic cancer vaccines is to induce tumour regression, eradicate minimal residual disease, establish lasting antitumour memory and avoid non-specific or adverse reactions. However, tumour-induced immunosuppression and immunoresistance pose significant challenges to achieving this goal. In this Review, we deliberate on how to improve and expand the antigen repertoire for vaccines, consider developments in vaccine platforms and explore antigen-agnostic in situ vaccines. Furthermore, we summarize the reasons for failure of cancer vaccines in the past and provide an overview of various mechanisms of resistance posed by the tumour. Finally, we propose strategies for combining suitable vaccine platforms with novel immunomodulatory approaches and standard-of-care treatments for overcoming tumour resistance and enhancing clinical efficacy.

Safety and Efficacy of Personalized Cancer Vaccines in Combination With Immune Checkpoint Inhibitors in Cancer Treatment

Cancer immunotherapy can induce sustained responses in patients with cancers in a broad range of tissues, however, these treatments require the optimized combined therapeutic strategies. Despite immune checkpoint inhibitors (ICIs) have lasting clinical benefit, researchers are trying to combine them with other treatment modalities, and among them the combination with personalized cancer vaccines is attractive. Neoantigens, arising from mutations in cancer cells, can elicit strong immune response without central tolerance and out-target effects, which is a truly personalized method. Growing studies show that the combination can elevate the antitumor efficacy with acceptable safety and minimal additional toxicity compared with single agent vaccine or ICI. Herein, we have searched these preclinical and clinical trials and summarized safety and efficacy of personalized cancer vaccines combined with ICIs in several malignancies. Meanwhile, we discuss the rationale of the combination and future challenges.

Combination vaccine based on citrullinated vimentin and enolase peptides induces potent CD4-mediated anti-tumor responses

BACKGROUND

Stress-induced post-translational modifications occur during autophagy and can result in generation of new epitopes and immune recognition. One such modification is the conversion of arginine to citrulline by peptidylarginine deiminase enzymes.

METHODS

We used Human leukocyte antigen (HLA) transgenic mouse models to assess the immunogenicity of citrullinated peptide vaccine by cytokine Enzyme linked immunosorbant spot (ELISpot) assay. Vaccine efficacy was assessed in tumor therapy studies using HLA-matched B16 melanoma and ID8 ovarian models expressing either constitutive or interferon-gamma (IFNγ) inducible Major Histocompatibility Complex (MHC) class II (MHC-II) as represented by most human tumors. To determine the importance of CD4 T cells in tumor therapy, we analyzed the immune cell infiltrate into murine tumors using flow cytometry and performed therapy studies in the presence of CD4 and CD8 T cell depletion. We assessed the T cell repertoire to citrullinated peptides in ovarian cancer patients and healthy donors using flow cytometry.

RESULTS

The combination of citrullinated vimentin and enolase peptides (Modi-1) stimulated strong CD4 T cell responses in mice. Responses resulted in a potent anti-tumor therapy against established tumors and generated immunological memory which protected against tumor rechallenge. Depletion of CD4, but not CD8 T cells, abrogated the primary anti-tumor response as well as the memory response to tumor rechallenge. This was further reinforced by successful tumor regression being associated with an increase in tumor-infiltrating CD4 T cells and a reduction in tumor-associated myeloid suppressor cells. The anti-tumor response also relied on direct CD4 T cell recognition as only tumors expressing MHC-II were rejected. A comparison of different Toll-like receptor (TLR)-stimulating adjuvants showed that Modi-1 induced strong Th1 responses when combined with granulocyte-macrophage colony-stimulating factor (GMCSF), TLR9/TLR4, TLR9, TLR3, TLR1/2 and TLR7 agonists. Direct linkage of the TLR1/2 agonist to the peptides allowed the vaccine dose to be reduced by 10-fold to 100-fold without loss of anti-tumor activity. Furthermore, a CD4 Th1 response to the citrullinated peptides was seen in ovarian cancer patients.

CONCLUSIONS

Modi-1 citrullinated peptide vaccine induces potent CD4-mediated anti-tumor responses in mouse models and a CD4 T cell repertoire is present in ovarian cancer patients to the citrullinated peptides suggesting that Modi-1 could be an effective vaccine for ovarian cancer patients.

Development of new therapeutic options for the treatment of uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. Important cytogenetic and genetic risk factors for the development of UM include chromosome 3 monosomy, mutations in the guanine nucleotide-binding proteins GNAQ/GNA11, and loss of the BRACA1-associated protein 1 (BAP 1). Most primary UMs are treated conservatively with radiotherapy, but enucleation is necessary for large tumours. Despite the effectiveness of local control, up to 50% of UM patients develop metastasis for which there are no effective therapies. Attempts to utilise the targeted therapies that have been developed for the treatment of other cancers, including a range of signal transduction pathway inhibitors, have rarely produced significant outcomes in UM. Similarly, the application of immunotherapies that are effective in cutaneous melanoma to treat UM have also been disappointing. Other approaches that have been initiated involve proteasomal inhibitors and histone deacetylase inhibitors which are approved for the treatment of other cancers. Nevertheless, there have been occasional positive outcomes from these treatments in UM. Moreover, combination approaches in UM have also yielded some positive developments. It would be valuable to identify how to apply such therapies efficiently in UM, potentially via individualised tumour profiling. It would also be important to characterise UM tumours to differentiate the potential drivers of progression from those in other types of cancers. The recent identification of novel kinases and metastatic genes in UM tumours makes the development of new UM-specific treatments feasible.

GILT in tumor cells improves T cell-mediated anti-tumor immune surveillance

The lysosomal thiol reductase GILT catalyzes the reduction of disulfide bonds of protein antigens, facilitating antigen-presenting cells (APCs) to present antigen to T cells. However, whether GILT expression in tumor cells can be associated with improved T cell-mediated anti-tumor responses remains unknown. Here, we identify that GILT is able to facilitate anti-tumor immune surveillance via promoting MHC class I mediated-antigen presentation in colon carcinoma. By using mice model bearing colon tumors, we find that GILT inhibites tumor growth in vivo with more leucocytes infiltration but has no effect on tumor cell development in vitro in terms of proliferation, cell cycle and migration. Furthermore, by using transgenic OT-I mice, we recognize the tumor-expressing OVA peptide, a surrogate tumor antigen, we find that GILT is capable of enhancing MHC class I mediated antigen presentation and improving specific CD8⁺ T cell anti-tumor responses in murine colon carcinoma. These findings propose the boost of GILT-MHC-I axis in tumors as a viable option for immune system against cancer.

Advances in the development of personalized neoantigen-based therapeutic cancer vaccines

Within the past decade, the field of immunotherapy has revolutionized the treatment of many cancers with the development and regulatory approval of various immune-checkpoint inhibitors and chimeric antigen receptor T cell therapies in diverse indications. Another promising approach to cancer immunotherapy involves the use of personalized vaccines designed to trigger de novo T cell responses against neoantigens, which are highly specific to tumours of individual patients, in order to amplify and broaden the endogenous repertoire of tumour-specific T cells. Results from initial clinical studies of personalized neoantigen-based vaccines, enabled by the availability of rapid and cost-effective sequencing and bioinformatics technologies, have demonstrated robust tumour-specific immunogenicity and preliminary evidence of antitumour activity in patients with melanoma and other cancers. Herein, we provide an overview of the complex process that is necessary to generate a personalized neoantigen vaccine, review the types of vaccine-induced T cells that are found within tumours and outline strategies to enhance the T cell responses. In addition, we discuss the current status of clinical studies testing personalized neoantigen vaccines in patients with cancer and considerations for future clinical investigation of this novel, individualized approach to immunotherapy.

Advances in the development of personalized neoantigen-based therapeutic cancer vaccines

Within the past decade, the field of immunotherapy has revolutionized the treatment of many cancers with the development and regulatory approval of various immune-checkpoint inhibitors and chimeric antigen receptor T cell therapies in diverse indications. Another promising approach to cancer immunotherapy involves the use of personalized vaccines designed to trigger de novo T cell responses against neoantigens, which are highly specific to tumours of individual patients, in order to amplify and broaden the endogenous repertoire of tumour-specific T cells. Results from initial clinical studies of personalized neoantigen-based vaccines, enabled by the availability of rapid and cost-effective sequencing and bioinformatics technologies, have demonstrated robust tumour-specific immunogenicity and preliminary evidence of antitumour activity in patients with melanoma and other cancers. Herein, we provide an overview of the complex process that is necessary to generate a personalized neoantigen vaccine, review the types of vaccine-induced T cells that are found within tumours and outline strategies to enhance the T cell responses. In addition, we discuss the current status of clinical studies testing personalized neoantigen vaccines in patients with cancer and considerations for future clinical investigation of this novel, individualized approach to immunotherapy.

Interplay between glucocorticoids and tumor-infiltrating lymphocytes on the prognosis of adrenocortical carcinoma

Background

Adrenocortical carcinoma (ACC) is a rare endocrine malignancy. Tumor-related glucocorticoid excess is present in ~60% of patients and associated with particularly poor prognosis. Results of first clinical trials using immune checkpoint inhibitors were heterogeneous. Here we characterize tumor-infiltrating T lymphocytes (TILs) in ACC in association with glucocorticoids as potential explanation for resistance to immunotherapy.

Methods

We performed immunofluorescence analysis to visualize tumor-infiltrating T cells (CD3⁺), T helper cells (CD3⁺CD4⁺), cytotoxic T cells (CD3⁺CD8⁺) and regulatory T cells (Tregs; CD3⁺CD4⁺FoxP3⁺) in 146 ACC tissue specimens (107 primary tumors, 16 local recurrences, 23 metastases). Quantitative data of immune cell infiltration were correlated with clinical data (including glucocorticoid excess).

Results

86.3% of ACC specimens showed tumor infiltrating T cells (7.7 cells/high power field (HPF)), including T helper (74.0%, 6.7 cells/HPF), cytotoxic T cells (84.3%, 5.7 cells/HPF) and Tregs (49.3%, 0.8 cells/HPF). The number of TILs was associated with better overall survival (HR for death: 0.47, 95% CI 0.25 to 0.87), which was true for CD4⁺− and CD8⁺ subpopulations as well. In localized, non-metastatic ACC, the favorable impact of TILs on overall and recurrence-free survival was manifested even independently of ENSAT (European Network for the Study of Adrenal Tumors) stage, resection status and Ki67 index. T helper cells were negatively correlated with glucocorticoid excess (Phi=−0.290, p=0.009). Patients with glucocorticoid excess and low TILs had a particularly poor overall survival (27 vs. 121 months in patients with TILs without glucocorticoid excess).

Conclusion

Glucocorticoid excess is associated with T cell depletion and unfavorable prognosis. To reactivate the immune system in ACC by checkpoint inhibitors, an inhibition of adrenal steroidogenesis might be pivotal and should be tested in prospective studies.

Cancer Immunoprevention: Current Status and Future Directions

Cancer is one of the most serious diseases affecting health and the second leading cause of death worldwide. Despite the development of various therapeutic modalities to deal with cancer, limited improvement in overall survival of patients has been yielded. Since there is no certain cure for cancer, detection of premalignant lesions, and prevention of their progression are vital to the decline of high morbidity and mortality of cancer. Among approaches to cancer prevention, immunoprevention has gained further attention in recent years. Deep understanding of the tumor/immune system interplay and successful prevention of virally-induced malignancies by vaccines have paved the way toward broadening cancer immunoprevention application. The identification of tumor antigens in premalignant lesions was the turning point in cancer immunoprevention that led to designing preventive vaccines for various malignancies including multiple myeloma, colorectal, and breast cancer. In addition to vaccines, immune checkpoint inhibitors are also being tested for the prevention of oral squamous cell carcinoma (SCC), and imiquimod which is an established drug for the prevention of skin SCC, is a non-specific immunomodulator. Herein, to provide a bench-to-bedside understanding of cancer immunoprevention, we will review the role of the immune system in suppression and promotion of tumors, immunoprevention of virally-induced cancers, identification of tumor antigens in premalignant lesions, and clinical advances of cancer immunoprevention.

Engineering CD4+ T Cells to Enhance Cancer Immunity

This review presents key advances in combining T cell receptor (TCR) gene transfer to redirect T-cell specificity with gene engineering in order to enhance cancer-protective immune function. We discuss how emerging insights might be applied to CD4+ T cells. Although much attention has been paid to the role of CD8+ cytotoxic T cells in tumour protection, we provide convincing evidence that CD4+ helper T cells play a critical role in cancer immune responses in animal models and also in patients. We demonstrate that genetic engineering technologies provide exciting opportunities to extend the specificity range of CD4+ T cells from MHC class-II-presented epitopes to include peptides presented by MHC class I molecules. Functional enhancement of tumour immunity can improve the sensitivity of T cells to cancer antigens, promote survival in a hostile tumour microenvironment, boost cancer-protective effector mechanisms and enable the formation of T-cell memory. Engineered cancer-specific CD4+ T cells may contribute to protective immunity by a direct pathway involving cancer cell killing, and by an indirect pathway that boosts the function, persistence and memory formation of CD8+ T cells.

Revisiting the role of CD4+ T cells in cancer immunotherapy-new insights into old paradigms

Cancer immunotherapy has revolutionised cancer treatment, with immune checkpoint blockade (ICB) therapy and adoptive cell therapy (ACT) increasingly becoming standard of care across a growing number of cancer indications. While the majority of cancer immunotherapies focus on harnessing the anti-tumour CD8⁺ cytotoxic T cell response, the potential role of CD4⁺ 'helper' T cells has largely remained in the background. In this review, we give an overview of the multifaceted role of CD4⁺ T cells in the anti-tumour immune response, with an emphasis on recent evidence that CD4⁺ T cells play a bigger role than previously thought. We illustrate their direct anti-tumour potency and their role in directing a sustained immune response against tumours. We further highlight the emerging observation that CD4⁺ T cell responses against tumours tend to be against self-derived epitopes. These recent trends raise vital questions and considerations that will profoundly affect the rational design of immunotherapies to leverage on the full potential of the immune system against cancer.

Induced pluripotent stem cell-derived myeloid cells expressing OX40 ligand amplify antigen-specific T cells in advanced melanoma

Immune checkpoint inhibitors improved the survival rate of patients with unresectable melanoma. However, some patients do not respond, and variable immune-related adverse events have been reported. Therefore, more effective and antigen-specific immune therapies are urgently needed. We previously reported the efficacy of an immune cell therapy with immortalized myeloid cells derived from induced pluripotent stem cells (iPS-ML). In this study, we generated OX40L-overexpressing iPS-ML (iPS-ML-Zsgreen-OX40L) and investigated their characteristics and in vivo efficacy against mouse melanoma. We found that iPS-ML-Zsgreen-OX40L suppressed the progression of B16-BL6 melanoma, and prolonged survival of mice with ovalbumin (OVA)-expressing B16 melanoma (MO4). The number of antigen-specific CD8⁺ T cells was higher in spleen cells treated with OVA peptide-pulsed iPS-ML-Zsgreen-OX40L than in those without OX40L. The OVA peptide-pulsed iPS-ML-Zsgreen-OX40L significantly increased the number of tumor-infiltrating T lymphocytes (TILs) in MO4 tumor. Flow cytometry showed decreased regulatory T cells but increased effector and effector memory T cells among the TILs. Although we plan to use allogeneic iPS-ML in the clinical applications, iPS-ML showed the tumorgenicity in the syngeneic mice model. Incorporating the suicide gene is necessary to ensure the safety in the future study. Collectively, these results indicate that iPS-ML-Zsgreen-OX40L therapy might be a new method for antigen-specific cancer immunotherapy.