Lack of MHC class II molecules favors CD8+ T-cell infiltration into tumors associated with an increased control of tumor growth

MHC-II presentation by oral Langerhans cells impacts intraepithelial Tc17 abundance and Candida albicans oral infection via CD4 T cells

In a murine model (LCΔMHC-II) designed to abolish MHC-II expression in Langerhans cells (LCs), ∼18% of oral LCs retain MHC-II, yet oral mucosal CD4 T cells numbers are unaffected. In LCΔMHC-II mice, we now show that oral intraepithelial conventional CD8αβ T cell numbers expand 30-fold. Antibody-mediated ablation of CD4 T cells in wild-type mice also resulted in CD8αβ T cell expansion in the oral mucosa. Therefore, we hypothesize that MHC class II molecules uniquely expressed on Langerhans cells mediate the suppression of intraepithelial resident-memory CD8 T cell numbers via a CD4 T cell-dependent mechanism. The expanded oral CD8 T cells co-expressed CD69 and CD103 and the majority produced IL-17A [CD8 T cytotoxic (Tc)17 cells] with a minority expressing IFN-γ (Tc1 cells). These oral CD8 T cells showed broad T cell receptor Vβ gene usage indicating responsiveness to diverse oral antigens. Generally supporting Tc17 cells, transforming growth factor-β1 (TGF-β1) increased 4-fold in the oral mucosa. Surprisingly, blocking TGF-β1 signaling with the TGF-R1 kinase inhibitor, LY364947, did not reduce Tc17 or Tc1 numbers. Nonetheless, LY364947 increased γδ T cell numbers and decreased CD49a expression on Tc1 cells. Although IL-17A-expressing γδ T cells were reduced by 30%, LCΔMHC-II mice displayed greater resistance to Candida albicans in early stages of oral infection. These findings suggest that modulating MHC-II expression in oral LC may be an effective strategy against fungal infections at mucosal surfaces counteracted by IL-17A-dependent mechanisms.

FLT3L-dependent dendritic cells control tumor immunity by modulating Treg and NK cell homeostasis

FLT3-L-dependent classical dendritic cells (cDCs) recruit anti-tumor and tumor-protecting lymphocytes. We evaluate cancer growth in mice with low, normal, or high levels of cDCs. Paradoxically, both low or high numbers of cDCs improve survival in mice with melanoma. In low cDC context, tumors are restrained by the adaptive immune system through influx of effector T cells and depletion of Tregs and NK cells. High cDC numbers favor the innate anti-tumor response, with massive recruitment of activated NK cells, despite high Treg infiltration. Anti CTLA-4 but not anti PD-1 therapy synergizes with FLT3-L therapy in the cDCHi but not in the cDCLo context. A combination of cDC boost and Treg depletion dramatically improves survival of tumor-bearing mice. Transcriptomic data confirm the paradoxical effect of cDC levels on survival in several human tumor types. cDCHi-TregLo state in such patients predicts best survival. Modulating cDC numbers via FLT3 signaling may have therapeutic potential in human cancer.

Single-cell sequencing highlights heterogeneity and malignant progression in actinic keratosis and cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent of the keratinocyte-derived malignancies with actinic keratosis (AK) as a precancerous lesion. To comprehensively delineate the underlying mechanisms for the whole progression from normal skin to AK to invasive cSCC, we performed single-cell RNA sequencing (scRNA-seq) to acquire the transcriptomes of 138,982 cells from 13 samples of six patients including AK, squamous cell carcinoma in situ (SCCIS), cSCC, and their matched normal tissues, covering comprehensive clinical courses of cSCC. We identified diverse cell types, including important subtypes with different gene expression profiles and functions in major keratinocytes. In SCCIS, we discovered the malignant subtypes of basal cells with differential proliferative and migration potential. Differentially expressed genes (DEGs) analysis screened out multiple key driver genes including transcription factors along AK to cSCC progression. Immunohistochemistry (IHC)/immunofluorescence (IF) experiments and single-cell ATAC sequencing (scATAC-seq) data verified the expression changes of these genes. The functional experiments confirmed the important roles of these genes in regulating cell proliferation, apoptosis, migration, and invasion in cSCC tumor. Furthermore, we comprehensively described the tumor microenvironment (TME) landscape and potential keratinocyte-TME crosstalk in cSCC providing theoretical basis for immunotherapy. Together, our findings provide a valuable resource for deciphering the progression from AK to cSCC and identifying potential targets for anticancer treatment of cSCC.

EBV-induced T-cell responses in EBV-specific and nonspecific cancers

Epstein-Barr virus (EBV) is a ubiquitous human tumor virus associated with various malignancies, including B-lymphoma, NK and T-lymphoma, and epithelial carcinoma. It infects B lymphocytes and epithelial cells within the oropharynx and establishes persistent infection in memory B cells. With a balanced virus-host interaction, most individuals carry EBV asymptomatically because of the lifelong surveillance by T cell immunity against EBV. A stable anti-EBV T cell repertoire is maintained in memory at high frequency in the blood throughout persistent EBV infection. Patients with impaired T cell immunity are more likely to develop life-threatening lymphoproliferative disorders, highlighting the critical role of T cells in achieving the EBV-host balance. Recent studies reveal that the EBV protein, LMP1, triggers robust T-cell responses against multiple tumor-associated antigens (TAAs) in B cells. Additionally, EBV-specific T cells have been identified in EBV-unrelated cancers, raising questions about their role in antitumor immunity. Herein, we summarize T-cell responses in EBV-related cancers, considering latency patterns, host immune status, and factors like human leukocyte antigen (HLA) susceptibility, which may affect immune outcomes. We discuss EBV-induced TAA-specific T cell responses and explore the potential roles of EBV-specific T cell subsets in tumor microenvironments. We also describe T-cell immunotherapy strategies that harness EBV antigens, ranging from EBV-specific T cells to T cell receptor-engineered T cells. Lastly, we discuss the involvement of γδ T-cells in EBV infection and associated diseases, aiming to elucidate the comprehensive interplay between EBV and T-cell immunity.

Single-Cell Transcriptomic Analysis of Primary and Metastatic Tumor Ecosystems in Esophageal Squamous Cell Carcinoma

Lymph node metastasis, the leading cause of mortality in esophageal squamous carcinoma (ESCC) with a highly complex tumor microenvironment, remains underexplored. Here, the transcriptomes of 85 263 single cells are analyzed from four ESCC patients with lymph node metastases. Strikingly, it is observed that the metastatic microenvironment undergoes the emergence or expansion of interferon induced IFIT3+ T, B cells, and immunosuppressive cells such as APOC1+ APOE+ macrophages and myofibroblasts with highly expression of immunoglobulin genes (IGKC) and extracellular matrix component and matrix metallopeptidase genes. A poor-prognostic epithelial-immune dual expression program regulating immune effector processes, whose activity is significantly enhanced in metastatic malignant epithelial cells and enriched in CD74+ CXCR4+ and major histocompatibility complex (MHC) class II genes upregulated malignant epithelia cells is discovered. Comparing with primary tumor, differential intercellular communications of metastatic ESCC microenvironment are revealed and furtherly validated via multiplexed immunofluorescence and immunohistochemistry staining, which mainly rely on the crosstalk of APOC1+ APOE+ macrophages with tumor and stromal cell. The data highlight potential molecular mechanisms that shape the lymph-node metastatic microenvironment and may inform drug discovery and the development of new strategies to target these prometastatic nontumor components for inhibiting tumor growth and overcoming metastasis to improve clinical outcomes.

Hypoxia-inducible factors: master regulators of hypoxic tumor immune escape

Hypoxia, a common feature of the tumor microenvironment in various types of cancers, weakens cytotoxic T cell function and causes recruitment of regulatory T cells, thereby reducing tumoral immunogenicity. Studies have demonstrated that hypoxia and hypoxia-inducible factors (HIFs) 1 and 2 alpha (HIF1A and HIF2A) are involved in tumor immune escape. Under hypoxia, activation of HIF1A induces a series of signaling events, including through programmed death receptor-1/programmed death ligand-1. Moreover, hypoxia triggers shedding of complex class I chain-associated molecules through nitric oxide signaling impairment to disrupt immune surveillance by natural killer cells. The HIF-1-galactose-3-O-sulfotransferase 1-sulfatide axis enhances tumor immune escape via increased tumor cell-platelet binding. HIF2A upregulates stem cell factor expression to recruit tumor-infiltrating mast cells and increase levels of cytokines interleukin-10 and transforming growth factor-β, resulting in an immunosuppressive tumor microenvironment. Additionally, HIF1A upregulates expression of tumor-associated long noncoding RNAs and suppresses immune cell function, enabling tumor immune escape. Overall, elucidating the underlying mechanisms by which HIFs promote evasion of tumor immune surveillance will allow for targeting HIF in tumor treatment. This review discusses the current knowledge of how hypoxia and HIFs facilitate tumor immune escape, with evidence to date implicating HIF1A as a molecular target in such immune escape. This review provides further insight into the mechanism of tumor immune escape, and strategies for tumor immunotherapy are suggested.

Multilevel mechanism of immune checkpoint inhibitor action in solid tumors: History, present issues and future development (Review)

Immunotherapy with checkpoint inhibitors (antibodies that target and block immune checkpoints in the tumor microenvironment) is included in the standard of care for patients with different types of malignancy, such as melanoma, renal cell and urothelial carcinoma, lung cancer etc. The introduction of this new immunotherapy has altered the view on potential targets for treatment of solid tumors from tumor cells themselves to their immune microenvironment; this has led to a reconsideration of the mechanisms of tumor-associated immunity. However, only a subset of patients benefit from immunotherapy and patient response is often unpredictable, even with known initial levels of prognostic markers; the biomarkers for favorable response are still being investigated. Mechanisms of immune checkpoint inhibitors efficiency, as well as the origins of treatment failure, require further investigation. From a clinical standpoint, discrepancies between the theoretical explanation of inhibitors of immune checkpoint actions at the cellular level and their deployment at a tissue/organ level impede the effective clinical implementation of novel immune therapy. The present review assessed existing experimental and clinical data on functional activity of inhibitors of immune checkpoints to provide a more comprehensive picture of their mechanisms of action on a cellular and higher levels of biological organization.

Bioengineering of Bordetella pertussis Adenylate Cyclase Toxin for Vaccine Development and Other Biotechnological Purposes

The adenylate cyclase toxin, CyaA, is one of the key virulent factors produced by Bordetella pertussis, the causative agent of whooping cough. This toxin primarily targets innate immunity to facilitate bacterial colonization of the respiratory tract. CyaA exhibits several remarkable characteristics that have been exploited for various applications in vaccinology and other biotechnological purposes. CyaA has been engineered as a potent vaccine vehicle to deliver antigens into antigen-presenting cells, while the adenylate cyclase catalytic domain has been used to design a robust genetic assay for monitoring protein-protein interactions in bacteria. These two biotechnological applications are briefly summarized in this chapter.

Single-cell transcriptomic analysis defines the interplay between tumor cells, viral infection, and the microenvironment in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy with a complex tumor ecosystem. How the interplay between tumor cells, EBV, and the microenvironment contributes to NPC progression and immune evasion remains unclear. Here we performed single-cell RNA sequencing on ~104,000 cells from 19 EBV⁺ NPCs and 7 nonmalignant nasopharyngeal biopsies, simultaneously profiling the transcriptomes of malignant cells, EBV, stromal and immune cells. Overall, we identified global upregulation of interferon responses in the multicellular ecosystem of NPC. Notably, an epithelial-immune dual feature of malignant cells was discovered and associated with poor prognosis. Functional experiments revealed that tumor cells with this dual feature exhibited a higher capacity for tumorigenesis. Further characterization of the cellular components of the tumor microenvironment (TME) and their interactions with tumor cells revealed that the dual feature of tumor cells was positively correlated with the expression of co-inhibitory receptors on CD8⁺ tumor-infiltrating T cells. In addition, tumor cells with the dual feature were found to repress IFN-γ production by T cells, demonstrating their capacity for immune suppression. Our results provide new insights into the multicellular ecosystem of NPC and offer important clinical implications.

Adipose tissue dendritic cell signals are required to maintain T cell homeostasis and obesity-induced expansion

Adipose tissue derived chronic inflammation is a critical component of obesity induced type II diabetes. Major histocompatibility complex II (MHCII) mediated T cell activation within adipose tissue is one mechanism that contributes to this phenotype. However, the contribution of dendritic cells as professional antigen presenting cells in adipose issue has not previously been explored. Using Itgax^Cre x MHCII^fl/fl (M11cKO) mice we observed adipose tissue specific changes in adipose tissue leukocytes. While there was a complete knockout of MHCII in dendritic cells, MHCII was also absent on the majority of macrophages. This resulted in reduction of TCR expression in CD4⁺ T cells in obese adipose tissue, and an increase in CD8⁺ and CD4⁺ CD8⁺ double positive T cells with decreased CD4⁺ T cells independent of diet type. Increased CD8⁺ cells were not observed in the spleen, suggesting adipose tissue T cell regulation is tissue specific. In vitro studies demonstrated more potent antigen presentation function in adipose tissue dendritic cells compared to macrophages. Obese M11cKO mice had decreased CD11c⁺ adipose tissue macrophages. Despite the changes of immune cellularity in adipose tissue, M11cKO largely did not change inflammatory gene expression in adipose tissue and did not demonstrate differences in glucose and insulin intolerance. Overall MHCII expression on CD11c⁺ cells is important for maintaining CD4⁺ and CD8⁺ adipose tissue T cells, but these cellular changes fail to alter inflammatory output and systemic metabolism.

Trial watch: chemotherapy-induced immunogenic cell death in immuno-oncology

The term ‘immunogenic cell death’ (ICD) denotes an immunologically unique type of regulated cell death that enables, rather than suppresses, T cell-driven immune responses that are specific for antigens derived from the dying cells. The ability of ICD to elicit adaptive immunity heavily relies on the immunogenicity of dying cells, implying that such cells must encode and present antigens not covered by central tolerance (antigenicity), and deliver immunostimulatory molecules such as damage-associated molecular patterns and cytokines (adjuvanticity). Moreover, the host immune system must be equipped to detect the antigenicity and adjuvanticity of dying cells. As cancer (but not normal) cells express several antigens not covered by central tolerance, they can be driven into ICD by some therapeutic agents, including (but not limited to) chemotherapeutics of the anthracycline family, oxaliplatin and bortezomib, as well as radiation therapy. In this Trial Watch, we describe current trends in the preclinical and clinical development of ICD-eliciting chemotherapy as partner for immunotherapy, with a focus on trials assessing efficacy in the context of immunomonitoring.

Trial watch: Peptide-based vaccines in anticancer therapy

Peptide-based anticancer vaccination aims at stimulating an immune response against one or multiple tumor-associated antigens (TAAs) following immunization with purified, recombinant or synthetically engineered epitopes. Despite high expectations, the peptide-based vaccines that have been explored in the clinic so far had limited therapeutic activity, largely due to cancer cell-intrinsic alterations that minimize antigenicity and/or changes in the tumor microenvironment that foster immunosuppression. Several strategies have been developed to overcome such limitations, including the use of immunostimulatory adjuvants, the co-treatment with cytotoxic anticancer therapies that enable the coordinated release of damage-associated molecular patterns, and the concomitant blockade of immune checkpoints. Personalized peptide-based vaccines are also being explored for therapeutic activity in the clinic. Here, we review recent preclinical and clinical progress in the use of peptide-based vaccines as anticancer therapeutics.Abbreviations: CMP: carbohydrate-mimetic peptide; CMV: cytomegalovirus; DC: dendritic cell; FDA: Food and Drug Administration; HPV: human papillomavirus; MDS: myelodysplastic syndrome; MHP: melanoma helper vaccine; NSCLC: non-small cell lung carcinoma; ODD: orphan drug designation; PPV: personalized peptide vaccination; SLP: synthetic long peptide; TAA: tumor-associated antigen; TNA: tumor neoantigen

Therapeutic cancer vaccine: building the future from lessons of the past

Anti-cancer vaccines have raised many hopes from the start of immunotherapy but have not yet been clinically successful. The few positive results of anti-cancer vaccines have been observed in clinical situations of low tumor burden or preneoplastic lesions. Several new concepts and new results reposition this therapeutic approach in the field of immunotherapy. Indeed, cancers that respond to anti-PD-1/PD-L1 (20-30%) are those that are infiltrated by anti-tumor T cells with an inflammatory infiltrate. However, 70% of cancers do not appear to have an anti-tumor immune reaction in the tumor microenvironment. To induce this anti-tumor immunity, therapeutic combinations between vaccines and anti-PD-1/PD-L1 are being evaluated. In addition, the identification of neoepitopes against which the immune system is less tolerated is giving rise to a new enthusiasm by the first clinical results of the vaccine including these neoepitopes in humans. The ability of anti-cancer vaccines to induce a population of anti-tumor T cells called memory resident T cells that play an important role in immunosurveillance is also a new criterion to consider in the design of therapeutic vaccines.

Tumor-Derived TGFβ Alters the Ability of Plasmacytoid Dendritic Cells to Respond to Innate Immune Signaling

A growing number of observations has suggested that plasmacytoid dendritic cells (pDC) play a critical role in tumor biology. In patients, infiltration of tumors by pDCs generally correlates with a poor prognosis, suggesting that pDCs may play an important role in the host-tumor relationship. Here, we analyze the influence of pDCs in solid tumor development using two different tumor models: TC-1 and B16-OVA. Phenotypic and functional gene profiling analysis of tumor-associated pDCs showed that the tumor microenvironment affected their activation status and ability to produce cytokines and chemokines. In addition, tumor cells secreted factors that inhibit the ability of pDCs to produce type I IFN. Among the various cytokines and chemokines produced by the tumor cells, we demonstrate that TGFβ is the main factor responsible for this inhibition. Using a mouse model deficient for pDCs, we also show that pDCs promote TC-1 tumor growth and that natural killer (NK) cells and regulatory T cells are involved in the protumoral effect of pDCs. Overall, our results evidence the cross-talk among pDCs, NK, and regulatory T cells in the promotion of tumor growth and their role in the development of antitumor immune responses.Significance: These findings highlight the importance of pDCs in the cross-talk between tumor cells and the immune system. Cancer Res; 78(11); 3014-26. ©2018 AACR.