Effector function of human tumor-specific CD8 T cells in melanoma lesions: a state of local functional tolerance

Critical role of post-transcriptional regulation for IFN-γ in tumor-infiltrating T cells

Protective T cell responses against tumors require the production of Interferon gamma (IFN-γ). However, tumor-infiltrating T cells (TILs) gradually lose their capacity to produce IFN-γ and therefore fail to clear malignant cells. Dissecting the underlying mechanisms that block cytokine production is thus key for improving T cell products. Here we show that although TILs express substantial levels of Ifng mRNA, post-transcriptional mechanisms impede the production of IFN-γ protein due to loss of mRNA stability. CD28 triggering, but not PD1 blocking antibodies, effectively restores the stability of Ifng mRNA. Intriguingly, TILs devoid of AU-rich elements within the 3'untranslated region maintain stabilized Ifng mRNA and produce more IFN-γ protein than wild-type TILs. This sustained IFN-γ production translates into effective suppression of tumor outgrowth, which is almost exclusively mediated by direct effects on the tumor cells. We therefore conclude that post-transcriptional mechanisms could be modulated to potentiate effective T cell therapies in cancer.

Tumor Resident Memory T Cells: New Players in Immune Surveillance and Therapy

Tissue resident memory T cells (Trm) are a subset of memory T cells mainly described in inflammation and infection settings. Their location in peripheral tissues, such as lungs, gut, or skin, makes them the earliest T cell population to respond upon antigen recognition or under inflammatory conditions. The study of Trm cells in the field of cancer, and particularly in cancer immunotherapy, has recently gained considerable momentum. Different reports have shown that the vaccination route is critical to promote Trm generation in preclinical cancer models. Cancer vaccines administered directly at the mucosa, frequently result in enhanced Trm formation in mucosal cancers compared to vaccinations via intramuscular or subcutaneous routes. Moreover, the intratumoral presence of T cells expressing the integrin CD103 has been reported to strongly correlate with a favorable prognosis for cancer patients. In spite of recent progress, the full spectrum of Trm anti-tumoral functions still needs to be fully established, particularly in cancer patients, in different clinical contexts. In this mini-review we focus on the recent vaccination strategies aimed at generating Trm cells, as well as evidence supporting their association with patient survival in different cancer types. We believe that collectively, this information provides a strong rationale to target Trm for cancer immunotherapy.

A transcriptionally and functionally distinct PD-1+ CD8+ T cell pool with predictive potential in non-small-cell lung cancer treated with PD-1 blockade

Evidence from mouse chronic viral infection models suggests that CD8⁺ T cell subsets characterized by distinct expression levels of the receptor PD-1 diverge in their state of exhaustion and potential for reinvigoration by PD-1 blockade. However, it remains unknown whether T cells in human cancer adopt a similar spectrum of exhausted states based on PD-1 expression levels. We compared transcriptional, metabolic and functional signatures of intratumoral CD8⁺ T lymphocyte populations with high (PD-1^T), intermediate (PD-1^N) and no PD-1 expression (PD-1^-) from non-small-cell lung cancer patients. PD-1^T T cells showed a markedly different transcriptional and metabolic profile from PD-1^N and PD-1^- lymphocytes, as well as an intrinsically high capacity for tumor recognition. Furthermore, while PD-1^T lymphocytes were impaired in classical effector cytokine production, they produced CXCL13, which mediates immune cell recruitment to tertiary lymphoid structures. Strikingly, the presence of PD-1^T cells was strongly predictive for both response and survival in a small cohort of non-small-cell lung cancer patients treated with PD-1 blockade. The characterization of a distinct state of tumor-reactive, PD-1-bright lymphocytes in human cancer, which only partially resembles that seen in chronic infection, provides potential avenues for therapeutic intervention.

Perspectives on Chimeric Antigen Receptor T-Cell Immunotherapy for Solid Tumors

Chimeric antigen receptor (CAR) T-cell therapy entails the genetic engineering of a patient's T-cells to express membrane spanning fusion receptors with defined specificities for tumor-associated antigens. These CARs are capable of eliciting robust T-cell activation to initiate killing of the target tumor cells. This therapeutic approach has produced unprecedented clinical outcomes in the treatment of "liquid" hematologic cancers, but to date has not produced comparable responses in targeting solid malignancies. Advances in our understanding of the immunobiology of solid tumors have highlighted several hurdles which currently hinder the efficacy of this therapy. These barriers include the insufficient accumulation of CAR T-cells in the tumor due to poor trafficking or physical exclusion and the exposure of infiltrating CAR T-cells to a panoply of immune suppressive checkpoint molecules, cytokines, and metabolic stresses that are not conducive to efficient immune reactions and can thereby render these cells anergic, exhausted, or apoptotic. This mini-review summarizes these hurdles and describes some recent approaches and innovations to genetically re-engineer CAR T-cells to counter inhibitory influences found in the tumor microenvironment. Novel immunotherapy drug combinations to potentiate the activity of CAR T-cells are also discussed. As our understanding of the immune landscape of tumors improves and our repertoire of immunotherapeutic drugs expands, it is envisaged that the efficacy of CAR T-cells against solid tumors might be potentiated using combination therapies, which it is hoped may lead to meaningful improvements in clinical outcome for patients with refractory solid malignancies.

T Cell Dysfunction in Cancer

Therapeutic reinvigoration of tumor-specific T cells has greatly improved clinical outcome in cancer. Nevertheless, many patients still do not achieve durable benefit. Recent evidence from studies in murine and human cancer suggest that intratumoral T cells display a broad spectrum of (dys-)functional states, shaped by the multifaceted suppressive signals that occur within the tumor microenvironment. Here we discuss the current understanding of T cell dysfunction in cancer, the value of novel technologies to dissect such dysfunction at the single cell level, and how our emerging understanding of T cell dysfunction may be utilized to develop personalized strategies to restore antitumor immunity.

Combination Immunotherapy: Taking Cancer Vaccines to the Next Level

With the advent of checkpoint blockade therapies, immunotherapy is now a critical modality for the treatment of some cancers. While some patients respond well to checkpoint blockade, many do not, necessitating the need for other forms of therapy. Vaccination against malignancy has been a long sought goal of science. For cancers holding a microbial etiology, vaccination has been highly effective in reducing the incidence of disease. However, vaccination against established malignancy has been largely disappointing. In this review, we discuss efforts to develop diverse vaccine modalities in the treatment of cancer with a particular focus on melanoma. Recent work has suggested that vaccines targeting patient-specific tumor mutations may be more relevant than those targeting unmutated proteins. Nonetheless, tumor cells utilize many strategies to evade host immunity. It is likely that the full potential of cancer vaccination will only be realized when vaccines are combined with other therapies targeting tumor immunoevasive mechanisms. By modulating inhibitory molecules, regulatory immune cells, and the metabolic resources and demands of T cells, scientists and clinicians can ensure vaccine-stimulated T cells are fully functional within the immunosuppressive tumor microevironment.

The Vast Universe of T Cell Diversity: Subsets of Memory Cells and Their Differentiation

The T cell receptor confers specificity for antigen recognition to T cells. By the first encounter with the cognate antigen, reactive T cells initiate a program of expansion and differentiation that will define not only the ultimate quantity of specific cells that will be generated, but more importantly their quality and functional heterogeneity. Recent achievements using mouse model infection systems have helped to shed light into the complex network of factors that dictate and sustain memory T cell differentiation, ranging from antigen load, TCR signal strength, metabolic fitness, transcriptional programs, and proliferative potential. The different models of memory T cell differentiation are discussed in this chapter, and key phenotypic and functional attributes of memory T cell subsets are presented, both for mouse and human cells. Therapeutic manipulation of memory T cell generation is expected to provide novel unique ways to optimize current immunotherapies, both in infection and cancer.

Non-genetic engineering of cytotoxic T cells to target IL-4 receptor enhances tumor homing and therapeutic efficacy against melanoma

Adoptive transfer of cytotoxic T lymphocytes (CTLs) has been used as an immunotherapy in melanoma. However, the tumor homing and therapeutic efficacy of transferred CTLs against melanoma remain unsatisfactory. Interleukin-4 receptor (IL-4R) is commonly up-regulated in tumors including melanoma. Here, we studied whether IL-4R-targeted CTLs exhibit enhanced tumor homing and therapeutic efficacy against melanoma. CTLs isolated from mice bearing melanomas were non-genetically engineered with IL4RPep-1, an IL-4R-binding peptide, using a membrane anchor composed of dioleylphosphatidylethanolamine. Compared to control CTLs, IL-4R-targeted CTLs showed higher binding to melanoma cells and in vivo tumor homing. They also exerted a more rapid and robust effector response, including increased cytokine secretion and cytotoxicity against melanoma cells and enhanced reprogramming of M2-type macrophages to M1-type macrophages. Moreover, IL-4R-targeted CTLs efficiently inhibited melanoma growth and reversed the immunosuppressive tumor microenvironment. These results suggest that non-genetically engineered CTLs targeting IL-4R have potential as an adoptive T cell therapy against melanoma.

CD68 and interleukin 13, prospective immune markers for esophageal squamous cell carcinoma prognosis prediction

Purpose

Oncology immunity was reported to play a key role in cancer development and progression, so we investigated the prediction role of several immune markers in esophageal squamous cell carcinoma (ESCC) patients after operation in this study.

Patients and Methods

66 primary ESCC tumor tissues and four sets of tissue microarrays including 705 primary ESCC tumor tissues from four centers were collected and analyzed. Expressions of several immune markers in ESCC tumor tissue were detected with immunohistochemistry staining. Their distribution densities were analyzed with InForm^™ 2.0.1 software. All statistic analyses were performed with SPSS16.0 and Stata version 10.0.

Results

Survival analyses assessed by Kaplan-Meier plots and log-rank tests demonstrated that densities of CD68 and interleukin 13 (IL-13) in tumor stroma were positively correlated with the overall survival of ESCC patients after operation (p < 0.01 for CD68, p < 0.001 for IL-13). Further, a model based on tumor stroma densities of CD68 and IL-13 was constructed and it could significantly classify patients with poor or good prognosis. This model could further identify high-risk group and low-risk group at the same Tumor lymph Nodes Metastases (TNM) stage. Lastly, a more accuracy model based on TNM stage, densities of CD68 and IL-13 was constructed to predict the prognosis of ESCC patient after operation.

Conclusion

Combining the TNM staging system and densities of CD68 and IL-13 could substantially improve the prognosis prediction accuracy of ESCC patient after operation, which might be an excellent tool for selecting patients for individualized therapy in future.

Transcriptional response to hypoxic stress in melanoma and prognostic potential of GBE1 and BNIP3

Gradients of hypoxia occur in most solid tumors and cells found in hypoxic regions are associated with the most aggressive and therapy-resistant fractions of the tumor. Despite the ubiquity and importance of hypoxia responses, little is known about the variation in the global transcriptional response to hypoxia in melanoma. Using microarray technology, whole genome gene expression profiling was first performed on established melanoma cell lines. From gene set enrichment analyses, we derived a robust 35 probes signature (hypomel for HYPOxia MELanoma) associated with hypoxia-response pathways, including 26 genes up regulated, and 9 genes down regulated. The microarray data were validated by RT-qPCR for the 35 transcripts. We then validated the signature in hypoxic zones from 8 patient specimens using laser microdissection or macrodissection of Formalin fixed-paraffin-embedded (FFPE) material, followed with RT-qPCR. Moreover, a similar hypoxia-associated gene expression profile was observed using NanoString technology to analyze RNAs from FFPE melanoma tissues of a cohort of 19 patients treated with anti-PD1. Analysis of NanoString data from validation sets using Non-Negative Matrix Factorization (NMF) analysis (26 genes up regulated in hypoxia) and dual clustering (samples and genes) further revealed that the increased level of BNIP3 (Bcl-2 adenovirus E1B 19 kDa-interacting protein 3)/GBE1 (glycogen branching enzyme1) differential pair correlates with the lack of response of melanoma patients to anti-PD1 (pembrolizumab) immunotherapy. These studies suggest that through elevated glycogenic flux and induction of autophagy, hypoxia is a critical molecular program that could be considered as a prognostic factor for melanoma.

In Vitro Modeling of Tumor-Immune System Interaction

Immunotherapy has emerged during the past two decades as an innovative and successful form of cancer treatment. However, frequently, mechanisms of actions are still unclear, predictive markers are insufficiently characterized, and preclinical assays for innovative treatments are poorly reliable. In this context, the analysis of tumor/immune system interaction plays key roles, but may be unreliably mirrored by in vivo experimental models and standard bidimensional culture systems. Tridimensional cultures of tumor cells have been developed to bridge the gap between in vitro and in vivo systems. Interestingly, defined aspects of the interaction of cells from adaptive and innate immune systems and tumor cells may also be mirrored by 3D cultures. Here we review in vitro models of cancer/immune cell interaction and we propose that updated technologies might help develop innovative treatments, identify biologicals of potential clinical relevance, and select patients eligible for immunotherapy treatments.

PD-1 and PD-L1 inhibitors in melanoma treatment: past success, present application and future challenges

Anti-programmed death (PD)-1 antibodies have now become the standard of care for advanced melanoma, with two drugs gaining US FDA approval in recent years: nivolumab and pembrolizumab. Both have demonstrated significant activity and durable response with a manageable toxicity profile. Despite initial success, ongoing challenges include patient selection and predictors of response, innate resistance and optimizing combination strategies. In this overview, we take a closer look at the history and development of therapeutic targets to the PD-1/PD-ligand (L)1 pathway, clinical evidence, availability of biomarkers and their limitations in clinical practice and future strategies to improve treatment outcomes.

Innate immune signaling and regulation in cancer immunotherapy

A pre-existing T cell-inflamed tumor microenvironment has prognostic utility and also can be predictive for response to contemporary cancer immunotherapies. The generation of a spontaneous T cell response against tumor-associated antigens depends on innate immune activation, which drives type I interferon (IFN) production. Recent work has revealed a major role for the STING pathway of cytosolic DNA sensing in this process. This cascade of events contributes to the activation of Batf3-lineage dendritic cells (DCs), which appear to be central to anti-tumor immunity. Non-T cell-inflamed tumors lack chemokines for Batf3 DC recruitment, have few Batf3 DCs, and lack a type I IFN gene signature, suggesting that failed innate immune activation may be the ultimate cause for lack of spontaneous T cell activation and accumulation. With this information in hand, new strategies for triggering innate immune activation and Batf3 DC recruitment are being developed, including novel STING agonists for de novo immune priming. Ultimately, the successful development of effective innate immune activators should expand the fraction of patients that can respond to immunotherapies, such as with checkpoint blockade antibodies.

Cancer Immunotherapy Targets Based on Understanding the T Cell-Inflamed Versus Non-T Cell-Inflamed Tumor Microenvironment

Most cancers express tumor antigens that can be recognized by T cells of the host. The fact that cancers become clinically evident nonetheless implies that immune escape must occur. Two major subsets of human melanoma metastases have been identified based on gene expression profiling. One subgroup has a T cell-inflamed phenotype that includes expression of chemokines, T cell markers, and a type I IFN signature. In contrast, the other major subset lacks this phenotype and has been designated as non-T cell-inflamed. The mechanisms of immune escape are likely distinct in these two phenotypes, and therefore the optimal immunotherapeutic interventions necessary to promote clinical responses may be different. The T cell-inflamed tumor microenvironment subset shows the highest expression of negative regulatory factors, including PD-L1, IDO, FoxP3+ Tregs, and evidence for T cell-intrinsic anergy. Therapeutic strategies to overcome these inhibitory mechanisms are being pursued, and anti-PD-1 mAbs have been FDA approved. The presence of multiple inhibitory mechanisms in the same tumor microenvironment argues that combination therapies may be advantageous, several of which are in clinical testing. A new paradigm may be needed to promote de novo inflammation in cases of the non-T cell-infiltrated tumor microenvironment. Natural innate immune sensing of tumors appears to occur via the host STING pathway, type I IFN production, and cross-priming of T cells via CD8α+ DCs. New strategies are being developed to engage this pathway therapeutically, such as through STING agonists. The molecular mechanisms that mediate the presence or absence of the T cell-inflamed tumor microenvironment are being elucidated using parallel genomics platforms. The first oncogene pathway identified that mediates immune exclusion is the Wnt/β-catenin pathway, suggesting that new pharmacologic strategies to target this pathway should be developed to restore immune access to the tumor microenvironment.

The Role of the Tumor Vasculature in the Host Immune Response: Implications for Therapeutic Strategies Targeting the Tumor Microenvironment

Recently developed cancer immunotherapy approaches including immune checkpoint inhibitors and chimeric antigen receptor T cell transfer are showing promising results both in trials and in clinical practice. These approaches reflect increasing recognition of the crucial role of the tumor microenvironment in cancer development and progression. Cancer cells do not act alone, but develop a complex relationship with the environment in which they reside. The host immune response to tumors is critical to the success of immunotherapy; however, the determinants of this response are incompletely understood. The immune cell infiltrate in tumors varies widely in density, composition, and clinical significance. The tumor vasculature is a key component of the microenvironment that can influence tumor behavior and treatment response and can be targeted through the use of antiangiogenic drugs. Blood vascular and lymphatic endothelial cells have important roles in the trafficking of immune cells, controlling the microenvironment, and modulating the immune response. Improving access to the tumor through vascular alteration with antiangiogenic drugs may prove an effective combinatorial strategy with immunotherapy approaches and might be applicable to many tumor types. In this review, we briefly discuss the host's immune response to cancer and the treatment strategies utilizing this response, before focusing on the pathological features of tumor blood and lymphatic vessels and the contribution these might make to tumor immune evasion.

Long-term intravital imaging of the multicolor-coded tumor microenvironment during combination immunotherapy

The combined-immunotherapy of adoptive cell therapy (ACT) and cyclophosphamide (CTX) is one of the most efficient treatments for melanoma patients. However, no synergistic effects of CTX and ACT on the spatio-temporal dynamics of immunocytes in vivo have been described. Here, we visualized key cell events in immunotherapy-elicited immunoreactions in a multicolor-coded tumor microenvironment, and then established an optimal strategy of metronomic combined-immunotherapy to enhance anti-tumor efficacy. Intravital imaging data indicated that regulatory T cells formed an 'immunosuppressive ring' around a solid tumor. The CTX-ACT combined-treatment elicited synergistic immunoreactions in tumor areas, which included relieving the immune suppression, triggering the transient activation of endogenous tumor-infiltrating immunocytes, increasing the accumulation of adoptive cytotoxic T lymphocytes, and accelerating the infiltration of dendritic cells. These insights into the spatio-temporal dynamics of immunocytes are beneficial for optimizing immunotherapy and provide new approaches for elucidating the mechanisms underlying the involvement of immunocytes in cancer immunotherapy.

DOI:http://dx.doi.org/10.7554/eLife.14756.001

Melanoma is a form of skin cancer that is particularly difficult to treat. A new approach that has shown a lot of promise in treating many different cancers, including melanoma, is called “immunotherapy”. This technique harnesses the immune system – the body’s natural defences that help to protect against infections and disease – to combat cancer.

One powerful type of immunotherapy involves injecting patients with cells called lymphocytes, which form part of the immune system. This is known as adoptive cell therapy and can activate the immune system to fight cancer, helping to shrink tumors. This treatment can be made even more powerful by combining it with a drug called cyclophosphamide and this combination, known as CTX-ACT, is currently one of the most efficient treatments for melanoma. Yet, little information is available to indicate why this treatment is so effective.

Using mice implanted with melanoma cells, Qi, Li et al. sought to understand how CTX-ACT treatment works, with the goal of optimising it to increase its success. The results showed that a protective barrier of immune cells that suppresses the anti-tumor immune response – called an “immunosuppressive ring” – surrounds untreated tumors. CTX-ACT treatment can breakdown these rings, helping to reactivate the anti-tumor immune reaction in the tumors. This allows both the injected and mouse’s own immune cells to move into the tumor and destroy cancer cells.

Qi, Li et al. used their findings to optimise treatment and succeeded in controlling tumor growth in the mice for several weeks. These new insights could be used to improve current immunotherapies, and offer new approaches for investigating the involvement of immune cells in the treatment of a wide range of different cancers.

DOI:http://dx.doi.org/10.7554/eLife.14756.002

Recent Advances in Immunotherapy in Metastatic NSCLC

Non-small cell lung cancer (NSCLC) is one of most common malignancies and the leading cause of cancer deaths worldwide. Despite advances in targeted therapies, majority of NSCLC patients do not have targetable genomic alterations. Nevertheless, recent discovery that NSCLC is an immunogenic tumor type, and several breakthroughs in immunotherapies have led to rapid expansion of this new treatment modality in NSCLC with recent FDA approvals of programed death receptor-1 inhibitors, such as nivolumab and pembrolizumab. Here, we review promising immunotherapeutic approaches in metastatic NSCLC, including checkpoint inhibitors, agents with other mechanisms of action, and immunotherapy combinations with other drugs. With advent of immunotherapy, therapeutic options in metastatic NSCLC are rapidly expanding with the hope to further expand life expectancy in metastatic lung cancer.

PTPN22 contributes to exhaustion of T lymphocytes during chronic viral infection

The protein encoded by the autoimmune-associated protein tyrosine phosphatase nonreceptor type 22 gene, PTPN22, has wide-ranging effects in immune cells including suppression of T-cell receptor signaling and promoting efficient production of type I interferons (IFN-I) by myeloid cells. Here we show that mice deficient in PTPN22 resist chronic viral infection with lymphocytic choriomeningitis virus clone 13 (LCMV cl13). The numbers and function of viral-specific CD4 T lymphocytes is greatly enhanced, whereas expression of the IFNβ-induced IL-2 repressor, cAMP-responsive element modulator (CREM) is reduced. Reduction of CREM expression in wild-type CD4 T lymphocytes prevents the loss of IL-2 production by CD4 T lymphocytes during infection with LCMV cl13. These findings implicate the IFNβ/CREM/IL-2 axis in regulating T-lymphocyte function during chronic viral infection.

Dysregulation of TGFβ1 Activity in Cancer and Its Influence on the Quality of Anti-Tumor Immunity

TGFβ1 is a pleiotropic cytokine that exhibits a variety of physiologic and immune regulatory functions. Although its influence on multiple cell types is critical for the regulation of numerous biologic processes in the host, dysregulation of both TGFβ1 expression and activity is frequently observed in cancer and contributes to various aspects of cancer progression. This review focuses on TGFβ1’s contribution to tumor immune suppression and escape, with emphasis on the influence of this regulatory cytokine on the differentiation and function of dendritic cells and T cells. Clinical trials targeting TGFβ1 in cancer patients are also reviewed, and strategies for future therapeutic interventions that build on our current understanding of immune regulation by TGFβ1 are discussed.

Regulatory circuits of T cell function in cancer

Recent progress in cancer immunotherapy emphasizes the importance of understanding immune-regulatory pathways in tumours. Dysfunction of antitumour T cells may be due to mechanisms that are evolutionarily conserved or acquired by somatic mutations. The dysfunctional state of T cells has been termed 'exhaustion', on the basis of similarities to dysfunctional T cells in chronic infections. However, despite shared properties, recent studies have identified marked differences between T cell dysfunction in cancer and chronic infection. In this Review, we discuss T cell-intrinsic molecular alterations and metabolic communication in the tumour microenvironment. Identification of the underlying molecular drivers of T cell dysfunction is essential for the continued progress of cancer research and therapy.

Tumor-Specific T Cell Dysfunction Is a Dynamic Antigen-Driven Differentiation Program Initiated Early during Tumorigenesis

CD8(+) T cells recognizing tumor-specific antigens are detected in cancer patients but are dysfunctional. Here we developed a tamoxifen-inducible liver cancer mouse model with a defined oncogenic driver antigen (SV40 large T-antigen) to follow the activation and differentiation of naive tumor-specific CD8(+) T (TST) cells after tumor initiation. Early during the pre-malignant phase of tumorigenesis, TST cells became dysfunctional, exhibiting phenotypic, functional, and transcriptional features similar to dysfunctional T cells isolated from late-stage human tumors. Thus, T cell dysfunction seen in advanced human cancers may already be established early during tumorigenesis. Although the TST cell dysfunctional state was initially therapeutically reversible, it ultimately evolved into a fixed state. Persistent antigen exposure rather than factors associated with the tumor microenvironment drove dysfunction. Moreover, the TST cell differentiation and dysfunction program exhibited features distinct from T cell exhaustion in chronic infections. Strategies to overcome this antigen-driven, cell-intrinsic dysfunction may be required to improve cancer immunotherapy.

Tumor-Infiltrating T Cells and the PD-1 Checkpoint Pathway in Advanced Differentiated and Anaplastic Thyroid Cancer

CONTEXT

Five to 10% of patients with differentiated thyroid cancers (DTC) develop invasive and/or distant metastatic disease that is marginally improved with standard therapies. Prognosis is poor for patients with anaplastic thyroid cancer, with a median survival of 3-5 months. We suggest that a paradigm shift is necessary in the treatment of advanced cases.

OBJECTIVE

We hypothesized that a T-cell response is generated in advanced thyroid cancer and may be a viable therapeutic target.

DESIGN

Primary DTCs were analyzed by quantitative RT-PCR (n = 92) for expression of CD3, CD8, forkhead box (Fox)-P3, programmed death (PD)-1, PD-1 ligand-1, and PD-1 ligand-2 and biopsied for cellular analysis by flow cytometry (n = 11). Advanced pT4 cases (n = 22) and metastases (n = 5) were analyzed by immunohistochemistry.

SETTING

The study was conducted at the University of Colorado Hospital.

PATIENTS

Thyroid cancer patients undergoing thyroidectomy or completion surgery for advanced disease between 2002 and 2013 participated in the study.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURE

Immune markers were analyzed for association with disease severity.

RESULTS

Immune markers were commonly expressed at the RNA level. PD-L1 was higher (P = .0443) in patients with nodal metastases. FoxP3(+) (P < .0001), PD-1(+)CD8(+) (P = .0058), and PD-1(+)CD4(+) (P = .0104) T cells were enriched in DTC biopsies. CD8(+) and FoxP3(+) T cells were detected by immunohistochemistry in all pT4 tumors and a subset of metastases. PD-1(+) lymphocytes were found in 50% of DTCs. PD-L1 was expressed by tumor and associated leukocytes in 13 of 22 cases, and expression was more diffuse in anaplastic thyroid cancer (P = .0373). BRAF(V600E) mutation was associated with higher frequencies of tumor-associated lymphocytes (P = .0095) but not PD-L1 expression.

CONCLUSIONS

PD-1 checkpoint blockades may have therapeutic efficacy in patients with aggressive forms of thyroid cancer.

Ret mouse very large tumors (VLTs) display altered ratios of infiltrating memory to naive T cells: Roles in tumor expansion

Melanoma is an aggressive skin cancer, however it is immunogenic. The size of the primary tumor is associated with the nodal metastases. Our goals were to characterize melanoma-associated antigens (MAAs) and tumor-infiltrating T-lymphocytes (TILs) subsets in the few very large tumors (VLTs) developing in ret transgenic mice of melanoma. Tumors >700mg (VLTs) were investigated for MAAs and subsets of TILs. Immunohistochemistry and flow cytometry-based studies were performed to determine the infiltration patterns of T-lymphocytes in VLTs. It was observed that zinc fixative restores the antigenicity of the cell-surface markers of lymphocyte subpopulations without the need of antigen retrieval, whereas formalin-based fixative fails to restore the antigenicity in the presence of antigen retrieval in the immunohistochemistry. VLTs from ret mice express MAAs, such as Tyrosinase, TRP-1, TRP-2 and gp-100. The mean±standard deviation (S.D.) T-cell infiltration per 400 times-high power field in VLTs; CD4(+) (2.33±1.3), CD8(+) (2.00±1.0), and CD4(+) Foxp3(+) (2.5±0.5) regulatory T cells infiltration was exclusively restricted to the tumor stroma. Moreover, our flow cytometry-based data reveal that % mean±S.D. naive CD3(+) CD4(+) T cell infiltration (32.8±4.0%) was significantly larger than effector (25.8±2.8%, p<0.01) and central memory cells (16.1±3.7%, p<0.001) in VLTs. Similarly, between CD3(+) CD8(+) T cells, naive cells infiltrate (57.7±2.3%) in a significantly larger frequency than effector (5.0±0.4%, p<0.0001) and central memory cell (4.8±1.7%, p<0.0001) subsets. These results suggest that the VLTs from ret mice display lowered infiltration ratios between memory and naive T cells, which could be associated with the relatively large growth of VLTs.

Effector, Memory, and Dysfunctional CD8(+) T Cell Fates in the Antitumor Immune Response

The adaptive immune system plays a pivotal role in the host's ability to mount an effective, antigen-specific immune response against tumors. CD8(+) tumor-infiltrating lymphocytes (TILs) mediate tumor rejection through recognition of tumor antigens and direct killing of transformed cells. In growing tumors, TILs are often functionally impaired as a result of interaction with, or signals from, transformed cells and the tumor microenvironment. These interactions and signals can lead to transcriptional, functional, and phenotypic changes in TILs that diminish the host's ability to eradicate the tumor. In addition to effector and memory CD8(+) T cells, populations described as exhausted, anergic, senescent, and regulatory CD8(+) T cells have been observed in clinical and basic studies of antitumor immune responses. In the context of antitumor immunity, these CD8(+) T cell subsets remain poorly characterized in terms of fate-specific biomarkers and transcription factor profiles. Here we discuss the current characterization of CD8(+) T cell fates in antitumor immune responses and discuss recent insights into how signals in the tumor microenvironment influence TIL transcriptional networks to promote CD8(+) T cell dysfunction.

Cutting Edge: Engineering Active IKKβ in T Cells Drives Tumor Rejection

Acquired dysfunction of tumor-reactive T cells is one mechanism by which tumors can evade the immune system. Identifying and correcting pathways that contribute to such dysfunction should enable novel anticancer therapy design. During cancer growth, T cells show reduced NF-κB activity, which is required for tumor rejection. Impaired T cell-intrinsic NF-κB may create a vicious cycle conducive to tumor progression and further T cell dysfunction. We hypothesized that forcing T cell-intrinsic NF-κB activation might break this cycle and induce tumor elimination. NF-κB was activated in T cells by inducing the expression of a constitutively active form of the upstream activator IκB kinase β (IKKβ). T cell-restricted constitutively active IKKβ augmented the frequency of functional tumor-specific CD8(+) T cells and improved tumor control. Transfer of constitutively active IKKβ-transduced T cells also boosted endogenous T cell responses that controlled pre-established tumors. Our results demonstrate that driving T cell-intrinsic NF-κB can result in tumor control, thus identifying a pathway with potential clinical applicability.

Human Cytotoxic T Lymphocytes Form Dysfunctional Immune Synapses with B Cells Characterized by Non-Polarized Lytic Granule Release

Suppression of the cytotoxic T cell (CTL) immune response has been proposed as one mechanism for immune evasion in cancer. In this study, we have explored the underlying basis for CTL suppression in the context of B cell malignancies. We document that human B cells have an intrinsic ability to resist killing by freshly isolated cytotoxic T cells (CTLs), but are susceptible to lysis by IL-2 activated CTL blasts and CTLs isolated from immunotherapy-treated patients with chronic lymphocytic leukemia (CLL). Impaired killing was associated with the formation of dysfunctional non-lytic immune synapses characterized by the presence of defective linker for activation of T cells (LAT) signaling and non-polarized release of the lytic granules transported by ADP-ribosylation factor-like protein 8 (Arl8). We propose that non-lytic degranulation of CTLs are a key regulatory mechanism of evasion through which B cells may interfere with the formation of functional immune synapses by CTLs.

Phase I study with ONCOS-102 for the treatment of solid tumors - an evaluation of clinical response and exploratory analyses of immune markers

Background

We conducted a phase I study with a granulocyte macrophage colony stimulating factor (GMCSF)-expressing oncolytic adenovirus, ONCOS-102, in patients with solid tumors refractory to available treatments. The objectives of the study were to determine the optimal dose for further use and to assess the safety, tolerability and adverse event (AE) profile of ONCOS-102. Further, the response rate and overall survival were evaluated as well as preliminary evidence of disease control. As an exploratory endpoint, the effect of ONCOS 102 on biological correlates was examined.

Methods

The study was conducted using a classic 3 + 3 dose escalation study design involving 12 patients. Patients were repeatedly treated intratumorally with ONCOS-102 plus daily low-dose oral cyclophosphamide (CPO). Tumor response was evaluated with diagnostic positron emission tomography (PET) and computed tomography (CT). Tumor biopsies were collected at baseline and after treatment initiation for analysis of immunological correlates. Peripheral blood mononuclear cells (PBMCs) were collected at baseline and during the study to assess antigen specificity of CD8+ T cells by interferon gamma (IFNγ) enzyme linked immunospot assay (ELISPOT).

Results

No dose limiting toxicity (DLT) or maximum tolerated dose (MTD) was identified for ONCOS-102. Four out of ten (40 %) evaluable patients had disease control based on PET/CT scan at 3 months and median overall survival was 9.3 months. A short-term increase in systemic pro-inflammatory cytokines and a prominent infiltration of TILs to tumors was seen post-treatment in 11 out of 12 patients. Two patients showed marked infiltration of CD8+ T cells to tumors and concomitant systemic induction of tumor-specific CD8+ T cells. Interestingly, high expression levels of genes associated with activated T_H1 cells and T_H1 type immune profile were observed in the post-treatment biopsies of these two patients.

Conclusions

ONCOS-102 is safe and well tolerated at the tested doses. All three examined doses may be used in further development. There was evidence of antitumor immunity and signals of clinical efficacy. Importantly, treatment resulted in infiltration of CD8+ T cells to tumors and up-regulation of PD-L1, highlighting the potential of ONCOS-102 as an immunosensitizing agent for combinatory therapies with checkpoint inhibitors.

Trial registration

NCT01598129. Registered 19/04/2012

PD-L1 Negative Status is Associated with Lower Mutation Burden, Differential Expression of Immune-Related Genes, and Worse Survival in Stage III Melanoma

PURPOSE

Understanding why some melanomas test negative for PD-L1 by IHC may have implications for the application of anti-PD-1 therapies in melanoma management. This study sought to determine somatic mutation and gene expression patterns associated with tumor cell PD-L1 expression, or lack thereof, in stage III metastatic melanoma to better define therapeutically relevant patient subgroups.

EXPERIMENTAL DESIGN

IHC for PD-L1 was assessed in 52 American Joint Committee on Cancer stage III melanoma lymph node specimens and compared with specimen-matched comprehensive clinicopathologic, genomic, and transcriptomic data.

RESULTS

PD-L1-negative status was associated with lower nonsynonymous mutation (NSM) burden (P = 0.017) and worse melanoma-specific survival [HR = 0.28 (0.12-0.66), P = 0.002] in stage III melanoma. Gene set enrichment analysis identified an immune-related gene expression signature in PD-L1-positive tumors. There was a marked increase in cytotoxic T-cell and macrophage-specific genes in PD-L1-positive melanomas. CD8A(high) gene expression was associated with better melanoma-specific survival [HR = 0.2 (0.05-0.87), P = 0.017] and restricted to PD-L1-positive stage III specimens. NF1 mutations were restricted to PD-L1-positive tumors (P = 0.041).

CONCLUSIONS

Tumor negative PD-L1 status in stage III melanoma lymph node metastasis is a marker of worse patient survival and is associated with a poor immune response gene signature. Lower NSM levels were associated with PD-L1-negative status suggesting differences in somatic mutation profiles are a determinant of PD-L1-associated antitumor immunity in stage III melanoma. Clin Cancer Res; 22(15); 3915-23. ©2016 AACR.

The Lymphatic System in Disease Processes and Cancer Progression

Advances in our understanding of the structure and function of the lymphatic system have made it possible to identify its role in a variety of disease processes. Because it is involved not only in fluid homeostasis but also in immune cell trafficking, the lymphatic system can mediate and ultimately alter immune responses. Our rapidly increasing knowledge of the molecular control of the lymphatic system will inevitably lead to new and effective therapies for patients with lymphatic dysfunction. In this review, we discuss the molecular and physiological control of lymphatic vessel function and explore how the lymphatic system contributes to many disease processes, including cancer and lymphedema.

T Cells and Cancer: How Metabolism Shapes Immunity

Tumor microenvironment is characterized by a consistent reduction in oxygen and blood-borne nutrients that significantly affects the metabolism of distinct cell subsets. Immune cells populating malignant lesions need to activate alternative pathways to overcome tumor-prolonged nutrient deprivation. In particular, the metabolic switch occurring in transforming tissues dramatically impacts on tumor-infiltrating T cell biology. Remarkably, the recruitment and activation of T cell within cancers are instrumental for effective antitumor response. Therefore, T cell metabolic adaptation acts as crucial checkpoint hijacked by tumors to dampen antitumor immunity.

Cish actively silences TCR signaling in CD8+ T cells to maintain tumor tolerance

Palmer et al. find that Cish, a member of the SOCS family, is induced by TCR stimulation in CD8⁺ T cells and inhibits their functional avidity against tumor. The authors uncover a novel mechanism of suppression for a SOCS member.

Improving the functional avidity of effector T cells is critical in overcoming inhibitory factors within the tumor microenvironment and eliciting tumor regression. We have found that Cish, a member of the suppressor of cytokine signaling (SOCS) family, is induced by TCR stimulation in CD8⁺ T cells and inhibits their functional avidity against tumors. Genetic deletion of Cish in CD8⁺ T cells enhances their expansion, functional avidity, and cytokine polyfunctionality, resulting in pronounced and durable regression of established tumors. Although Cish is commonly thought to block STAT5 activation, we found that the primary molecular basis of Cish suppression is through inhibition of TCR signaling. Cish physically interacts with the TCR intermediate PLC-γ1, targeting it for proteasomal degradation after TCR stimulation. These findings establish a novel targetable interaction that regulates the functional avidity of tumor-specific CD8⁺ T cells and can be manipulated to improve adoptive cancer immunotherapy.

Melanoma: oncogenic drivers and the immune system

Advances and in-depth understanding of the biology of melanoma over the past 30 years have contributed to a change in the consideration of melanoma as one of the most therapy-resistant malignancies. The finding that oncogenic BRAF mutations drive tumor growth in up to 50% of melanomas led to a molecular therapy revolution for unresectable and metastatic disease. Moving beyond BRAF, inactivation of immune regulatory checkpoints that limit T cell responses to melanoma has provided targets for cancer immunotherapy. In this review, we discuss the molecular biology of melanoma and we focus on the recent advances of molecularly targeted and immunotherapeutic approaches.

Progression of Lung Cancer Is Associated with Increased Dysfunction of T Cells Defined by Coexpression of Multiple Inhibitory Receptors

Dysfunctional T cells present in malignant lesions are characterized by a sustained and highly diverse expression of inhibitory receptors, also referred to as immune checkpoints. Yet, their relative functional significance in different cancer types remains incompletely understood. In this study, we provide a comprehensive characterization of the diversity and expression patterns of inhibitory receptors on tumor-infiltrating T cells from patients with non-small cell lung cancer. In spite of the large heterogeneity observed in the amount of PD-1, Tim-3, CTLA-4, LAG-3, and BTLA expressed on intratumoral CD8(+) T cells from 32 patients, a clear correlation was established between increased expression of these inhibitory coreceptors and progression of the disease. Notably, the latter was accompanied by a progressively impaired capacity of T cells to respond to polyclonal activation. Coexpression of several inhibitory receptors was gradually acquired, with early PD-1 and late LAG-3/BTLA expression. PD-1 blockade was able to restore T-cell function only in a subset of patients. A high percentage of PD-1(hi) T cells was correlated with poor restoration of T-cell function upon PD-1 blockade. Of note, PD-1(hi) expression marked a particularly dysfunctional T-cell subset characterized by coexpression of multiple inhibitory receptors and thus may assist in identifying patients likely to respond to inhibitory receptor-specific antibodies. Overall, these data may provide a framework for future personalized T-cell-based therapies aiming at restoration of tumor-infiltrating lymphocyte effector functions.

Systemic neutrophil-to-lymphocyte ratio in colorectal cancer: the relationship to patient survival, tumour biology and local lymphocytic response to tumour

Background:

Colorectal cancer (CRC) is a major cause of mortality and morbidity. The impact of inflammatory biomarkers (C-reactive protein etc.) on CRC is increasingly studied including systemic neutrophil-to-lymphocyte ratio (NLR) as they seem to predict outcome.

Methods:

All patients who underwent curative resection for CRC from 2000 to 2004 at Leeds Teaching Hospitals NHS Trust had pre-operative NLR calculated. Demographic, histopathological and survival data were collected. Tissue microarrays were created and stained to determine the mismatch repair (MMR) protein status of each tumour. Local lymphocytic response to the tumour was assessed and graded.

Results:

About 358 patients were eligible. Of these 88 had an NLR ⩾5, which predicted lower overall survival and greater disease recurrence. A high NLR is associated with higher pT- and pN-stage and a greater incidence of extramural venous invasion. MMR protein status was not associated with NLR. A pronounced lymphocytic reaction at the invasive margin (IM) indicated a better prognosis and was associated with a lower NLR.

Conclusion:

Neutrophil-to-lymphocyte ratio predicts disease-free and overall survival and is associated with a more aggressive tumour phenotype. The lymphocytic response to tumour at the IM is associated with NLR however dMMR is not. Neutrophil-to-lymphocyte ratio is a cheap, easy-to-access test that predicts outcome in CRC.

From T cell "exhaustion" to anti-cancer immunity

The immune system has the potential to protect from malignant diseases for extended periods of time. Unfortunately, spontaneous immune responses are often inefficient. Significant effort is required to develop reliable, broadly applicable immunotherapies for cancer patients. A major innovation was transplantation with hematopoietic stem cells from genetically distinct donors for patients with hematologic malignancies. In this setting, donor T cells induce long-term remission by keeping cancer cells in check through powerful allogeneic graft-versus-leukemia effects. More recently, a long awaited breakthrough for patients with solid tissue cancers was achieved, by means of therapeutic blockade of T cell inhibitory receptors. In untreated cancer patients, T cells are dysfunctional and remain in a state of T cell "exhaustion". Nonetheless, they often retain a high potential for successful defense against cancer, indicating that many T cells are not entirely and irreversibly exhausted but can be mobilized to become highly functional. Novel antibody therapies that block inhibitory receptors can lead to strong activation of anti-tumor T cells, mediating clinically significant anti-cancer immunity for many years. Here we review these new treatments and the current knowledge on tumor antigen-specific T cells.

Inhibitory Receptors Beyond T Cell Exhaustion

Inhibitory receptors (iRs) are frequently associated with "T cell exhaustion". However, the expression of iRs is also dependent on T cell differentiation and activation. Therapeutic blockade of various iRs, also referred to as "checkpoint blockade", is showing -unprecedented results in the treatment of cancer patients. Consequently, the clinical potential in this field is broad, calling for increased research efforts and rapid refinements in the understanding of iR function. In this review, we provide an overview on the significance of iR expression for the interpretation of T cell functionality. We summarize how iRs have been strongly associated with "T cell exhaustion" and illustrate the parallel evidence on the importance of T cell differentiation and activation for the expression of iRs. The differentiation subsets of CD8 T cells (naïve, effector, and memory cells) show broad and inherent differences in iR expression, while activation leads to strong upregulation of iRs. Therefore, changes in iR expression during an immune response are often concomitant with T cell differentiation and activation. Sustained expression of iRs in chronic infection and in the tumor microenvironment likely reflects a specialized T cell differentiation. In these situations of prolonged antigen exposure and chronic inflammation, T cells are "downtuned" in order to limit tissue damage. Furthermore, we review the novel "checkpoint blockade" treatments and the potential of iRs as biomarkers. Finally, we provide recommendations for the immune monitoring of patients to interpret iR expression data combined with parameters of activation and differentiation of T cells.

Expression of inhibitory receptors on intratumoral T cells modulates the activity of a T cell-bispecific antibody targeting folate receptor

T-cell bispecific antibodies (TCBs) are a novel therapeutic tool designed to selectively recruit T-cells to tumor cells and simultaneously activate them. However, it is currently unknown whether the dysfunctional state of T-cells, embedded into the tumor microenvironment, imprints on the therapeutic activity of TCBs. We performed a comprehensive analysis of activation and effector functions of tumor-infiltrating T-cells (TILs) in different tumor types, upon stimulation by a TCB targeting folate receptor 1 and CD3 (FolR1-TCB). We observed a considerable heterogeneity in T-cell activation, cytokine production and tumor cell killing upon exposure to FolR1-TCB among different FolR1-expressing tumors. Of note, tumors presenting with a high frequency of PD-1^hi TILs displayed significantly impaired tumor cell killing and T-cell function. Further characterization of additional T-cell inhibitory receptors revealed that PD-1^hi TILs defined a T-cell subset with particularly high levels of multiple inhibitory receptors compared with PD-1^int and PD-1^neg T-cells. PD-1 blockade could restore cytokine secretion but not cytotoxicity of TILs in a subset of patients with scarce PD-1^hi expressing cells; in contrast, patients with abundance of PD-1^hi expressing T-cells did not benefit from PD-1 blockade. Our data highlight that FolR1-TCB is a promising novel immunotherapeutic treatment option which is capable of activating intratumoral T-cells in different carcinomas. However, its therapeutic efficacy may be substantially hampered by a pre-existing dysfunctional state of T-cells, reflected by abundance of intratumoral PD-1^hi T-cells. These findings present a rationale for combinatorial approaches of TCBs with other therapeutic strategies targeting T-cell dysfunction.

The Next Hurdle in Cancer Immunotherapy: Overcoming the Non-T-Cell-Inflamed Tumor Microenvironment

A growing body of evidence suggests that a major subset of patients with advanced solid tumors shows evidence for a T-cell-inflamed tumor microenvironment. This phenotype has positive prognostic value for several types of early stage cancer, suggesting that the attempt by the host to generate an anti-tumor immune response reflects a biologic process associated with improved patient outcomes. In metastatic disease, the presence of this phenotype appears to be associated with clinical response to several immunotherapies, including cancer vaccines, checkpoint blockade, and adoptive T-cell transfer. With the high rate of clinical response to several of these therapies, along with early data indicating that combination immunotherapies may be even more potent, it seems likely that effective immune-based therapies will become a reality for patients with a range of different cancers that physiologically support the T-cell-inflamed tumor microenvironment in a subset of individuals. Therefore, one of the next significant hurdles will be to develop new therapeutic interventions that will enable these immunotherapies to be effective in patients with the non-T-cell-inflamed phenotype. Rational development of such interventions will benefit from a detailed molecular understanding of the mechanisms that explain the presence or absence of the T-cell-inflamed tumor microenvironment, which in turn will benefit from focused interrogation of patient samples. This iterative "reverse-translational" research strategy has already identified new candidate therapeutic targets and approaches. It is envisioned that the end result of these investigations will be an expanded array of interventions that will broaden the fraction of patients benefitting from immunotherapies in the clinic.

Impaired T-Cell Function in B-Cell Lymphoma: A Direct Consequence of Events at the Immunological Synapse?

Tumors can escape immune destruction through the development of antigen loss variants and loss of antigen processing/presentation pathways, thereby rendering them invisible to T cells. Alternatively, mechanisms of peripheral T-cell tolerance that would normally be important for protection from the development of autoimmunity may also be co-opted to (i) generate an immuno-inhibitory tumor environment, (ii) promote development of regulatory cell populations, or (iii) cell-intrinsically inactivate tumor-specific T cells. Emerging evidence suggests that T-cell function is impaired in hematological malignancies, which may manifest from cognate interactions between T cells and the tumor. The immunological synapse forms the cognate T-cell and antigen-presenting cell interaction and is the site where key signalling events, including those delivered by co-inhibitory receptors, that determine the fate of T cells occur. Here, we review evidence that events at the immune synapse between T cells and malignant B cells and alterations in immune synapse function may contribute to loss of T-cell function in B-cell malignancies.

Melanoma-derived factors alter the maturation and activation of differentiated tissue-resident dendritic cells

Dendritic cells (DCs) are key regulators of host immunity that are capable of inducing either immune tolerance or activation. In addition to their well-characterized role in shaping immune responses to foreign pathogens, DCs are also known to be critical for the induction and maintenance of anti-tumor immune responses. Therefore, it is important to understand how tumors influence the function of DCs and the quality of immune responses they elicit. Although the majority of studies in this field to date have utilized either immortalized DC lines or DC populations that have been generated under artificial conditions from hematopoietic precursors in vitro, we wished to investigate how tumors impact the function of already differentiated, tissue-resident DCs. Therefore, we used both an ex vivo and in vivo model system to assess the influence of melanoma-derived factors on DC maturation and activation. In ex vivo studies with freshly isolated splenic DCs, we demonstrate that the extent to which DC maturation and activation are altered by these factors correlates with melanoma tumorigenicity, and we identify partial roles for tumor-derived transforming growth factor (TGF)β1 and vascular endothelial growth factor (VEGF)-A in the altered functionality of DCs. In vivo studies using a lung metastasis model of melanoma also demonstrate tumorigenicity-dependent alterations to the function of lung-resident DCs, and skewed production of proinflammatory cytokines and chemokines by these tumor-altered cells is associated with recruitment of an immune infiltrate that may ultimately favor tumor immune escape and outgrowth.

Human tumor infiltrating lymphocytes cooperatively regulate prostate tumor growth in a humanized mouse model

Background

The complex interactions that occur between human tumors, tumor infiltrating lymphocytes (TIL) and the systemic immune system are likely to define critical factors in the host response to cancer. While conventional animal models have identified an array of potential anti-tumor therapies, mouse models often fail to translate into effective human treatments. Our goal is to establish a humanized tumor model as a more effective pre-clinical platform for understanding and manipulating TIL.

Methods

The immune system in NOD/SCID/IL-2Rγnull (NSG) mice was reconstituted by the co-administration of human peripheral blood lymphocytes (PBL) or subsets (CD4+ or CD8+) and autologous human dendritic cells (DC), and animals simultaneously challenged by implanting human prostate cancer cells (PC3 line). Tumor growth was evaluated over time and the phenotype of recovered splenocytes and TIL characterized by flow cytometry and immunohistochemistry (IHC). Serum levels of circulating cytokines and chemokines were also assessed.

Results

A tumor-bearing huPBL-NSG model was established in which human leukocytes reconstituted secondary lymphoid organs and promoted the accumulation of TIL. These TIL exhibited a unique phenotype when compared to splenocytes with a predominance of CD8+ T cells that exhibited increased expression of CD69, CD56, and an effector memory phenotype. TIL from huPBL-NSG animals closely matched the features of TIL recovered from primary human prostate cancers. Human cytokines were readily detectible in the serum and exhibited a different profile in animals implanted with PBL alone, tumor alone, and those reconstituted with both. Immune reconstitution slowed but could not eliminate tumor growth and this effect required the presence of CD4+ T cell help.

Conclusions

Simultaneous implantation of human PBL, DC and tumor results in a huPBL-NSG model that recapitulates the development of human TIL and allows an assessment of tumor and immune system interaction that cannot be carried out in humans. Furthermore, the capacity to manipulate individual features and cell populations provides an opportunity for hypothesis testing and outcome monitoring in a humanized system that may be more relevant than conventional mouse models.

An exhaustion-like phenotype constrains the activity of CD4+ T cells specific for a self and melanoma antigen

While the immune system has the capacity to recognize and destroy melanoma, tolerance mechanisms often hinder the development of effective anti-tumor immune responses. Since many melanoma antigens are self proteins expressed in normal melanocytes, self antigen exposure before tumor development can negatively impact the function of T cells specific for these self/tumor antigens. However, the contribution of self tolerance to anti-melanoma T cell dysfunction remains largely unexplored. We have previously described a TCR transgenic (Tg) mouse model in which T cells specific for the self/melanoma antigen, tyrosinase-related protein 1 (TRP1), develop in the presence of endogenous TRP1 expression (Ag+) and diminished antigen presentation due to the absence of gamma-interferon-inducible lysosomal thiol reductase (GILT-/-). We show that TRP1-specific T cells from these Ag+GILT-/-Tg mice do not protect from melanoma tumor growth, fail to induce autoimmune vitiligo, and undergo diminished proliferation compared to T cells from Ag-GILT+/+Tg mice. Despite an increased frequency of TRP1-specific Treg cells in Ag+GILT-/-Tg mice compared to Ag-GILT+/+Tg animals, Treg cell depletion only partially rescues the proliferative capacity of T cells from TRP1-expressing mice, suggesting the involvement of additional suppressive mechanisms. An increased percentage of melanoma-specific T cells from Ag+GILT-/-Tg animals express PD-1, an inhibitory receptor associated with the maintenance of T cell exhaustion. Antibody blockade of PD-1 partially improves the ability of TRP1-specific T cells from Ag+GILT-/-Tg mice to produce IL-2. These findings demonstrate that melanoma-specific T cells exposed to a self/melanoma antigen in healthy tissue develop an exhaustion-like phenotype characterized by PD-1-mediated immunosuppression prior to encounter with tumor.

The STING pathway and the T cell-inflamed tumor microenvironment

A major subset of patients with advanced solid tumors show a spontaneous T cell-inflamed tumor microenvironment, which has prognostic import and is associated with clinical response to immunotherapies. As such, understanding the mechanisms governing the generation of spontaneous T cell responses in only a subset of patients is critical for advancing immunotherapeutic approaches further. Here, we discuss the characteristics of T cell-inflamed versus non-inflamed tumors, including a type I interferon (IFN) signature associated with T cell priming against tumor antigens. We review recent findings that have pointed towards the STING (stimulator of interferon genes) pathway of cytosolic DNA sensing as an important innate immune sensing mechanism driving type I IFN production in the tumor context. Knowledge of this pathway is guiding the further development of novel immunotherapeutic strategies.

Blockade of PD-1/PD-L1 promotes adoptive T-cell immunotherapy in a tolerogenic environment

Adoptive cellular immunotherapy using in vitro expanded CD8+ T cells shows promise for tumour immunotherapy but is limited by eventual loss of function of the transferred T cells through factors that likely include inactivation by tolerogenic dendritic cells (DC). The co-inhibitory receptor programmed death-1 (PD-1), in addition to controlling T-cell responsiveness at effector sites in malignancies and chronic viral diseases is an important modulator of dendritic cell-induced tolerance in naive T cell populations. The most potent therapeutic capacity amongst CD8+ T cells appears to lie within Tcm or Tcm-like cells but memory T cells express elevated levels of PD-1. Based on established trafficking patterns for Tcm it is likely Tcm-like cells interact with lymphoid-tissue DC that present tumour-derived antigens and may be inherently tolerogenic to develop therapeutic effector function. As little is understood of the effect of PD-1/PD-L1 blockade on Tcm-like CD8+ T cells, particularly in relation to inactivation by DC, we explored the effects of PD-1/PD-L1 blockade in a mouse model where resting DC tolerise effector and memory CD8+ T cells. Blockade of PD-1/PD-L1 promoted effector differentiation of adoptively-transferred Tcm-phenotype cells interacting with tolerising DC. In tumour-bearing mice with tolerising DC, effector activity was increased in both lymphoid tissues and the tumour-site and anti-tumour activity was promoted. Our findings suggest PD-1/PD-L1 blockade may be a useful adjunct for adoptive immunotherapy by promoting effector differentiation in the host of transferred Tcm-like cells.