CD137 as a biomarker for tumor-reactive T cells: finding gold in the desert

ATOR-1017 (evunzekibart), an Fc-gamma receptor conditional 4-1BB agonist designed for optimal safety and efficacy, activates exhausted T cells in combination with anti-PD-1

BACKGROUND

4-1BB (CD137) is a co-stimulatory receptor highly expressed on tumor reactive effector T cells and NK cells, which upon stimulation prolongs persistence of tumor reactive effector T and NK cells within the tumor and induces long-lived memory T cells. 4-1BB agonistic antibodies have been shown to induce strong anti-tumor effects that synergize with immune checkpoint inhibitors. The first generation of 4-1BB agonists was, however, hampered by dose-limiting toxicities resulting in suboptimal dose levels or poor agonistic activity.

METHODS

ATOR-1017 (evunzekibart), a second-generation Fc-gamma receptor conditional 4-1BB agonist in IgG4 format, was designed to overcome the limitations of the first generation of 4-1BB agonists, providing strong agonistic effect while minimizing systemic immune activation and risk of hepatoxicity. The epitope of ATOR-1017 was determined by X-ray crystallography, and the functional activity was assessed in vitro and in vivo as monotherapy or in combination with anti-PD1.

RESULTS

ATOR-1017 binds to a unique epitope on 4-1BB enabling ATOR-1017 to activate T cells, including cells with an exhausted phenotype, and NK cells, in a cross-linking dependent, FcγR-conditional, manner. This translated into a tumor-directed and potent anti-tumor therapeutic effect in vivo, which was further enhanced with anti-PD-1 treatment.

CONCLUSIONS

These preclinical data demonstrate a strong safety profile of ATOR-1017, together with its potent therapeutic effect as monotherapy and in combination with anti-PD1, supporting further clinical development of ATOR-1017.

The Bispecific Tumor Antigen-Conditional 4-1BB x 5T4 Agonist, ALG.APV-527, Mediates Strong T-Cell Activation and Potent Antitumor Activity in Preclinical Studies

4-1BB (CD137) is an activation-induced costimulatory receptor that regulates immune responses of activated CD8 T and natural killer cells, by enhancing proliferation, survival, cytolytic activity, and IFNγ production. The ability to induce potent antitumor activity by stimulating 4-1BB on tumor-specific cytotoxic T cells makes 4-1BB an attractive target for designing novel immuno-oncology therapeutics. To minimize systemic immune toxicities and enhance activity at the tumor site, we have developed a novel bispecific antibody that stimulates 4-1BB function when co-engaged with the tumor-associated antigen 5T4. ALG.APV-527 was built on the basis of the ADAPTIR bispecific platform with optimized binding domains to 4-1BB and 5T4 originating from the ALLIGATOR-GOLD human single-chain variable fragment library. The epitope of ALG.APV-527 was determined to be located at domain 1 and 2 on 4-1BB using X-ray crystallography. As shown in reporter and primary cell assays in vitro, ALG.APV-527 triggers dose-dependent 4-1BB activity mediated only by 5T4 crosslinking. In vivo, ALG.APV-527 demonstrates robust antitumor responses, by inhibiting growth of established tumors expressing human 5T4 followed by a long-lasting memory immune response. ALG.APV-527 has an antibody-like half-life in cynomolgus macaques and was well tolerated at 50.5 mg/kg. ALG.APV-527 is uniquely designed for 5T4-conditional 4-1BB-mediated antitumor activity with potential to minimize systemic immune activation and hepatotoxicity while providing efficacious tumor-specific responses in a range of 5T4-expressing tumor indications as shown by robust activity in preclinical in vitro and in vivo models. On the basis of the combined preclinical dataset, ALG.APV-527 has potential as a promising anticancer therapeutic for the treatment of 5T4-expressing tumors.

Future Prospects of Immunotherapy in Non-Small-Cell Lung Cancer Patients: Is There Hope in Other Immune Checkpoints Targeting Molecules?

Currently, one of the leading treatments for non-small-cell lung cancer is immunotherapy involving immune checkpoint inhibitors. These monoclonal antibodies restore the anti-tumour immune response altered by negative immune checkpoint interactions. The most commonly used immunotherapeutics in monotherapy are anti-PD-1 and anti-PD-L1 antibodies. The effectiveness of both groups of antibodies has been proven in many clinical trials, which have translated into positive immunotherapeutic registrations for cancer patients worldwide. These antibodies are generally well tolerated, and certain patients achieve durable responses. However, given the resistance of some patients to this form of therapy, along with its other drawbacks, such as adverse events, alternatives are constantly being sought. Specifically, new drugs targeting already known molecules are being tested, and new potential targets are being explored. The aim of this paper is to provide an overview of the latest developments in this area.

The GPR171 pathway suppresses T cell activation and limits antitumor immunity

The recently identified G-protein-coupled receptor GPR171 and its ligand BigLEN are thought to regulate food uptake and anxiety. Though GPR171 is commonly used as a T cell signature gene in transcriptomic studies, its potential role in T cell immunity has not been explored. Here we show that GPR171 is transcribed in T cells and its protein expression is induced upon antigen stimulation. The neuropeptide ligand BigLEN interacts with GPR171 to suppress T cell receptor-mediated signalling pathways and to inhibit T cell proliferation. Loss of GPR171 in T cells leads to hyperactivity to antigen stimulation and GPR171 knockout mice exhibit enhanced antitumor immunity. Blockade of GPR171 signalling by an antagonist promotes antitumor T cell immunity and improves immune checkpoint blockade therapies. Together, our study identifies the GPR171/BigLEN axis as a T cell checkpoint pathway that can be modulated for cancer immunotherapy.

Oncolytic Adenovirus Coding for a Variant Interleukin 2 (vIL-2) Cytokine Re-Programs the Tumor Microenvironment and Confers Enhanced Tumor Control

The notion of developing variants of the classic interleukin 2 (IL-2) cytokine has emerged from the limitations observed with the systemic use of human IL-2 in the clinic: severe adverse events accompanied by low therapeutic response rate in treated patients. Modifications made in the IL-2 receptor-binding structure leads to preferential binding of IL-2 variant cytokine to receptors on effector anti-tumor lymphocytes over T regulatory (TReg) cells. Because of their inherent immunogenicity, oncolytic adenoviruses are useful for expression of immunomodulatory molecules in tumors, for induction of a pro-inflammatory state in the tumor microenvironment. In the present study, we constructed an adenovirus coding for an IL-2 variant (vIL-2) protein, Ad5/3-E2F-d24-vIL2. Functionality of the new virus was tested in vitro, and anti-tumor efficacy and mechanism of action studies were performed in immunocompetent hamsters bearing pancreatic tumors. Ad5/3-E2F-d24-vIL2 treatment elicited efficient anti-tumor response, with 62.5% monotherapy complete response. Moreover, it promoted substantial repression of genes associated with myeloid cells mediated immunosuppression (CD11b, ARG1, CD206). This was seen in conjunction with upregulation of genes associated with tumor-infiltrating lymphocyte (TIL) cytotoxicity (CD3G, SAP, PRF1, GZMM and GZMK). In summary, Ad5/3-E2F-d24-vIL2 demonstrates therapeutic potential by counteracting immunosuppression and in efficiently coordinating lymphocytes mediated anti-tumor response in immunosuppressive tumors. Thus, Ad5/3-E2F-d24-vIL2 is a promising candidate for translation into clinical trials in human immunosuppressive solid tumors.

CD137+ T-Cells: Protagonists of the Immunotherapy Revolution

Simple Summary

The CD137 receptor is expressed by activated antigen-specific T-cells. CD137⁺ T-cells were identified inside TILs and PBMCs of different tumor types and have proven to be the naturally occurring antitumor effector cells, capable of expressing a wide variability in terms of TCR specificity against both shared and neoantigenic tumor-derived peptides. The aim of this review is thus summarizing and highlighting their role as drivers of patients’ immune responses in anticancer therapies as well as their potential role in future and current strategies of immunotherapy.

Abstract

The CD137 receptor (4-1BB, TNF RSF9) is an activation induced molecule expressed by antigen-specific T-cells. The engagement with its ligand, CD137L, is capable of increasing T-cell survival, proliferation, and cytokine production. This allowed to identify the CD137⁺ T-cells as the real tumor-specific activated T-cell population. In fact, these cells express various TCRs that are specific for a wide range of tumor-derived peptides, both shared and neoantigenic ones. Moreover, their prevalence in sites close to the tumor and their unicity in killing cancer cells both in vitro and in vivo, raised particular interest in studying their potential role in different strategies of immunotherapy. They indeed showed to be a reliable marker able to predict patient’s outcome to immune-based therapies as well as monitor their response. In addition, the possibility of isolating and expanding this population, turned promising in order to generate effector antitumor T-cells in the context of adoptive T-cell therapies. CD137-targeting monoclonal antibodies have already shown their antitumor efficacy in cancer patients and a number of clinical trials are thus ongoing to test their possible introduction in different combination approaches of immunotherapy. Finally, the intracellular domain of the CD137 receptor was introduced in the anti-CD19 CAR-T cells that were approved by FDA for the treatment of pediatric B-cell leukemia and refractory B-cell lymphoma.

Diverse immune environments in human lung tuberculosis granulomas assessed by quantitative multiplexed immunofluorescence

The precise nature of the local immune responses in lung tuberculosis (TB) granulomas requires a comprehensive understanding of their environmental complexities. At its most basic level, a granuloma is a compact, organized immune aggregate of macrophages surrounded by myeloid, B and T cells. We established two complementary multiplex immunolabeling panels to simultaneously evaluate the myeloid and lymphocytic contexture of 14 human lung TB granulomas in formalin-fixed paraffin-embedded tissue samples. We observed diverse CD3+ and CD8+ T-cell and CD20+ B lymphocyte compositions of the granuloma immune environment and a relatively homogeneous distribution of all myeloid cells. We also found significant associations between CD8+ T-cell densities and the myeloid marker CD11b and phagocytic cell marker CD68. In addition, significantly more CD68+ macrophages and CD8+ T cells were found in Mycobacterium tuberculosis-infected granulomas, as detected by Ziehl-Neelsen staining. FOXP3 expression was predominately found in a small subset of CD4+ T cells in different granulomas. As the success or failure of each granuloma is determined by the immune response within that granuloma at a local and not a systemic level, we attempted to identify the presence of reactive T cells based on expression of the T-cell activation marker CD137 (4-1BB) and programmed cell death-1 (PD-1). Only a small fraction of the CD4+ and CD8+ T cells expressed PD-1. CD137 expression was found only in a very small fraction of the CD4+ T cells in two granulomas. Our results also showed that multinucleated giant cells showed strong PD-L1 but not CTLA-4 membrane staining. This study offers new insights into the heterogeneity of immune cell infiltration in lung TB granulomas, suggesting that each TB granuloma represents a unique immune environment that might be independently influenced by the local adaptive immune response, bacterial state, and overall host disease status.

IgM-Rheumatoid factor confers primary resistance to anti-PD-1 immunotherapies in NSCLC patients by reducing CD137+T-cells

Background

ICIs have strongly improved the outcome of NSCLC patients. However, primary and secondary resistance occur during treatment in most of the patients, with several of them developing fast progressions. Autoantibodies can be related with a dysfunctional immune system, although their association with immune-based anti-cancer therapies has never been investigated. Moreover, so far no reliable predictive factor is currently available to aid in treatment selection. CD137⁺T-cells are largely known to be the anti-tumor activated effector cells, but they have never been associated with the response to immunotherapies.

Methods

Forty-two patients with metastatic NSCLC receiving anti-PD-1 ICIs at Sant'Andrea Hospital and Policlinico Umberto I, from June 2016 to September 2018 were enrolled. Circulating levels of IgM-Rheumatoid Factor were evaluated at baseline and correlated with patients clinical response following the anti-PD-1 treatment. IgM-RF interaction and effect on T-cells in vivo and in vitro were investigated.

Findings

IgM-RF in NSCLC patient sera strongly predicted the development of early progression to ICIs. Also, a significant reduction of progression-free survival rate in anti-PD-1 treated patients could be identified when patients were stratified based on IgM-RF positivity and titers. IgM-RF bound preferentially circulating naïve and central memory T-cells and a significant reduction of CD137⁺ anti-tumor T effector cells was found in IgM-RF positive patients. In addition, a higher percentage of CD137⁺T-cells in peripheral blood of NSCLC patients at baseline resulted as a strong independent prognostic factor for a better outcome in terms of PFS and OS after the anti-PD-1 treatment. Furthermore, T-cells exposed to IgM-RF showed a robust defect in their migratory ability in response to CCL19 chemokine.

Interpretation

In this study we showed that serum IgM-RF can be regarded as predictive factor for the development of early progression and prognostic factor of a reduced progression-free survival and overall-survival in anti-PD-1 treated NSCLC patients. The ability of IgM-RF to bind naïve and central memory T-cells and impair their migration could make account for the reduction of the tumor-reactive CD137⁺ T-cells population that may cause a non-effectiveness of these T-cells targeting drugs.

Fundings

AIRC, MIUR and Sapienza University of Rome.

Molecular Aspects and Future Perspectives of Cytokine-Based Anti-cancer Immunotherapy

Cytokine-based immunotherapy is a promising field in the cancer treatment, since cytokines, as proteins of the immune system, are able to modulate the host immune response toward cancer cell, as well as directly induce tumor cell death. Since a low dose monotherapy with some cytokines has no significant therapeutic results and a high dose treatment leads to a number of side effects caused by the pleiotropic effect of cytokines, the problem of understanding the influence of cytokines on the immune cells involved in the pro- and anti-tumor immune response remains a pressing one. Immune system cells carry CD makers on their surface which can be used to identify various populations of cells of the immune system that play different roles in pro- and anti-tumor immune responses. This review discusses the functions and specific CD markers of various immune cell populations which are reported to participate in the regulation of the immune response against the tumor. The results of research studies and clinical trials investigating the effect of cytokine therapy on the regulation of immune cell populations and their surface markers are also discussed. Current trends in the development of cancer immunotherapy, as well as the role of cytokines in combination with other therapeutic agents, are also discussed.

Unique T-Cell Populations Define Immune-Inflamed Hepatocellular Carcinoma

BACKGROUND & AIMS

The characterization of T cells infiltrating hepatocellular carcinoma (HCC) provides information on cancer immunity and also on selection of patients with precise indication of immunotherapy. The aim of the study was to characterize T-cell populations within tumor tissue and compare them with non-neoplastic liver tissue as well as circulating cells of the same patients.

METHODS

The presence of unique cell populations was investigated in 36 HCC patients by multidimensional flow cytometry followed by t-distributed stochastic neighbor embedding analysis. Functional activity of tumor-infiltrating T cells was determined after activation by phorbol 12-myristate 13-acetate and ionomycin.

RESULTS

Within the tumor there were more cells expressing CD137 and ICOS than in non-neoplastic liver tissue, possibly after recent antigenic activation. These cells contained several populations, including the following: (1) functionally impaired, proliferating CD4⁺ cells co-expressing Inducible T-cell costimulator (ICOS) and T cell immunoreceptor with Ig and ITIM domains (TIGIT); (2) functionally active CD8⁺ cells co-expressing CD38 and Programmed cell-death protein 1 (PD1); and (3) CD4-CD8 double-negative T-cell receptor αβ and γδ cells (both non-major histocompatibility complex-restricted T cells). When the identified clusters were compared with histologic classification performed on the same samples, an accumulation of activated T cells was observed in immune-inflamed HCC. The same analyses performed in 7 patients receiving nivolumab treatment showed a remarkable reduction in the functionally impaired CD4⁺ cells, which returned to almost normal activity over time.

CONCLUSIONS

Unique populations of activated T cells are present in HCC tissue, whose antigen specificity remains to be investigated. Some of these cell populations are functionally impaired and nivolumab treatment restores their responsiveness. The finding of ongoing immune response within the tumor shows which lymphocyte populations are impaired within the HCC and identifies the patients who might take benefit from immunotherapy.

Tumor-associated factors are enriched in lymphatic exudate compared to plasma in metastatic melanoma patients

Liquid biopsies allow monitoring of cancer progression and detection of relapse, but reliable biomarkers in melanoma are lacking. Because secreted factors preferentially drain to lymphatic vessels before dilution in the blood, we hypothesized that lymph should be vastly enriched in cancer biomarkers. We characterized postoperative lymphatic exudate and plasma of metastatic melanoma patients after lymphadenectomy and found a dramatic enrichment in lymphatic exudate of tumor-derived factors and especially extracellular vesicles containing melanoma-associated proteins and miRNAs, with unique protein signatures reflecting early versus advanced metastatic spread. Furthermore, lymphatic exudate was enriched in memory T cells, including tumor-reactive CD137+ and stem cell-like types. In mice, lymph vessels were the major route of extracellular vesicle transport from tumors to the systemic circulation. We suggest that lymphatic exudate provides a rich source of tumor-derived factors for enabling the discovery of novel biomarkers that may reflect disease stage and therapeutic response.

Neoantigens retention in patient derived xenograft models mediates autologous T cells activation in ovarian cancer

Ovarian cancer (OC) has an overall modest number of mutations that facilitate a functional immune infiltrate able to recognize tumor mutated antigens, or neoantigens. Although patient-derived xenografts (PDXs) can partially model the tumor mutational load and mimic response to chemotherapy, no study profiled a neoantigen-driven response in OC PDXs. Here we demonstrate that the genomic status of the primary tumor from an OC patient can be recapitulated in vivo in a PDX model, with the goal of defining autologous T cells activation by neoantigens using in silico, in vitro and in vivo approaches. By profiling the PDX mutanome we discovered three main clusters of mutations defining the expansion, retraction or conservation of tumor clones based on their variant allele frequencies (VAF). RNASeq analyses revealed a strong functional conservation between the primary tumor and PDXs, highlighted by the upregulation of antigen presenting pathways. We tested in vitro a set of 30 neoantigens for recognition by autologous T cells and identified a core of six neoantigens that define a potent T cell activation able to slow tumor growth in vivo. The pattern of recognition of these six neoantigens indicates the pre-existence of anti-tumor immunity in the patient. To evaluate the breadth of T cell activation, we performed single cell sequencing profiling the TCR repertoire upon stimulation with neoantigenic moieties and identified sequence motifs that define an oligoclonal and autologous T cell response. Overall, these results indicate that OC PDXs can be a valid tool to model OC response to immunotherapy.

Impaired enolase 1 glycolytic activity restrains effector functions of tumor-infiltrating CD8+ T cells

In the context of solid tumors, there is a positive correlation between the accumulation of cytotoxic CD8+ tumor-infiltrating lymphocytes (TILs) and favorable clinical outcomes. However, CD8+ TILs often exhibit a state of functional exhaustion, limiting their activity, and the underlying molecular basis of this dysfunction is not fully understood. Here, we show that TILs found in human and murine CD8+ melanomas are metabolically compromised with deficits in both glycolytic and oxidative metabolism. Although several studies have shown that tumors can outcompete T cells for glucose, thus limiting T cell metabolic activity, we report that a down-regulation in the activity of ENOLASE 1, a critical enzyme in the glycolytic pathway, represses glycolytic activity in CD8+ TILs. Provision of pyruvate, a downstream product of ENOLASE 1, bypasses this inactivity and promotes both glycolysis and oxidative phosphorylation, resulting in improved effector function of CD8+ TILs. We found high expression of both enolase 1 mRNA and protein in CD8+ TILs, indicating that the enzymatic activity of ENOLASE 1 is regulated posttranslationally. These studies provide a critical insight into the biochemical basis of CD8+ TIL dysfunction.

CD28H expression identifies resident memory CD8 + T cells with less cytotoxicity in human peripheral tissues and cancers

The CD28H/B7-H5 pathway is a newly identified pathway of the B7 family. In human peripheral blood, the receptor CD28H is preferentially expressed on naïve T cells and repetitive stimulation of T cells leads to the loss of CD28H expression. Here we examined the expression of the CD28H/B7-H5 pathway in human peripheral tissues, as well as in human cancers. We found that CD28H is preferentially expressed on T cells with tissue-resident phenotypes (T_RM). Supporting that, stimulation via IL-15 and TGF-β, presumably major cytokines essential for T_RM cell homeostasis, sustains CD28H expression on T cells. The ligand B7-H5 is constitutively expressed on normal epithelium of human oral-gastrointestinal tracts. In human cancers, CD28H is preferentially present on tumor infiltrating lymphocytes (TILs) with T_RM features and identifies a T_RM subset with less cytotoxicity. Taken together, our studies suggest that the CD28H/B7-H5 pathway involves the interactions between T_RM cells and epithelium, and could be important for human T_RM homeostasis and function.

TK Inhibitor Pazopanib Primes DCs by Downregulation of the β-Catenin Pathway

Tyrosine kinase inhibitors (TKIs) target angiogenesis by affecting, for example, the VEGF receptors in tumors and have improved outcomes for patients with metastatic renal cell carcinoma (mRCC). Immune checkpoint inhibitors (ICIs) have also been proposed for treatment of mRCC with encouraging results. A better understanding of the activity of immune cells in mRCC, the immunomodulatory effects of TKIs, and the characteristics defining patients most likely to benefit from various therapies will help optimize immunotherapeutic approaches. In this study, we investigated the influence of the TKI pazopanib on dendritic cell (DC) performance and immune priming. Pazopanib improved DC differentiation and performance by promoting upregulation of the maturation markers HLA-DR, CD40, and CCR7; decreasing IL10 production and endocytosis; and increasing T-cell proliferation. PD-L1 expression was also downregulated. Our results demonstrate that pazopanib inhibits the Erk/β-catenin pathway, suggesting this pathway might be involved in increased DC activation. Similar results were confirmed in DCs differentiated from mRCC patients during pazopanib treatment. In treated patients pazopanib appeared to enhance a circulating CD4⁺ T-cell population that expresses CD137 (4-1BB). These results suggest that a potentially exploitable immunomodulatory effect induced by pazopanib could improve responses of patients with mRCC in customized protocols combining TKIs with ICI immunotherapy. Cancer Immunol Res; 6(6); 711-22. ©2018 AACR.

A kinetic investigation of interacting, stimulated T cells identifies conditions for rapid functional enhancement, minimal phenotype differentiation, and improved adoptive cell transfer tumor eradication

For adoptive cell transfer (ACT) immunotherapy of tumor-reactive T cells, an effective therapeutic outcome depends upon cell dose, cell expansion in vivo through a minimally differentiated phenotype, long term persistence, and strong cytolytic effector function. An incomplete understanding of the biological coupling between T cell expansion, differentiation, and response to stimulation hinders the co-optimization of these factors. We report on a biophysical investigation of how the short-term kinetics of T cell functional activation, through molecular stimulation and cell-cell interactions, competes with phenotype differentiation. T cells receive molecular stimulation for a few minutes to a few hours in bulk culture. Following this priming period, the cells are then analyzed at the transcriptional level, or isolated as single cells, with continuing molecular stimulation, within microchambers for analysis via 11-plex secreted protein assays. We resolve a rapid feedback mechanism, promoted by T cell—T cell contact interactions, which strongly amplifies T cell functional performance while yielding only minimal phenotype differentiation. When tested in mouse models of ACT, optimally primed T cells lead to complete tumor eradication. A similar kinetic process is identified in CD8⁺ and CD4⁺ T cells collected from a patient with metastatic melanoma.

CD137 is a Useful Marker for Identifying CD4+ T Cell Responses to Mycobacterium tuberculosis

Upregulation of CD137 on recently activated CD8⁺ T cells has been used to identify rare viral and tumour antigen-specific T cells from the peripheral blood. We aimed to evaluate the accuracy of CD137 for identifying Mycobacterium tuberculosis (Mtb)-reactive CD4⁺ T cells in the peripheral blood of infected individuals by flow cytometry and to investigate the characteristics of these CD137⁺ CD4⁺ T cells. We initially enrolled 31 active tuberculosis (TB) patients, 31 individuals with latent TB infection (LTBI) and 25 healthy donors. The intracellular CD137 and interferon-γ (IFN-γ) production by CD4⁺ T cells was simultaneously detected under unstimulated and CFP10-stimulated (culture filtrate protein 10, a Mtb-specific antigen) conditions. In unstimulated CD4⁺ T cells, we found that the CD137 expression in the TB group was significantly higher than that in the LTBI group. Stimulation with CFP10 largely increased the CD4⁺ T cell CD137 expression in both the TB and LTBI groups. After CFP10 stimulation, the frequency of CD137⁺ CD4⁺ T cells was higher than that of IFN-γ⁺ CD4⁺ T cells in both the TB and LTBI groups. Most of the CFP10-activated IFN-γ-secreting cells were CD137-positive, but only a small fraction of the CD137-positive cells expressed IFN-γ. An additional 20 patients with TB were enrolled to characterize the CD45RO⁺ CCR7⁺ , CD45RO⁺ CCR7^- and CD45RO^- subsets in the CD137⁺ CD4⁺ T cell populations. The Mtb-specific CD137⁺ CD4⁺ T cells were mainly identified as having an effector memory phenotype. In conclusion, CD137 is a useful marker that can be used for identifying Mtb-reactive CD4⁺ T cells by flow cytometry.

Pancreatic cancer cell/fibroblast co-culture induces M2 like macrophages that influence therapeutic response in a 3D model

Pancreatic cancer (PC) remains one of the most challenging solid tumors to treat with a high unmet medical need as patients poorly respond to standard-of-care-therapies. Prominent desmoplastic reaction involving cancer-associated fibroblasts (CAFs) and the immune cells in the tumor microenvironment (TME) and their cross-talk play a significant role in tumor immune escape and progression. To identify the key cellular mechanisms induce an immunosuppressive tumor microenvironment, we established 3D co-culture model with pancreatic cancer cells, CAFs and monocytes. Using this model, we analyzed the influence of tumor cells and fibroblasts on monocytes and their immune suppressive phenotype. Phenotypic characterization of the monocytes after 3D co-culture with tumor/fibroblast spheroids was performed by analyzing the expression of defined cell surface markers and soluble factors. Functionality of these monocytes and their ability to influence T cell phenotype and proliferation was investigated. 3D co-culture of monocytes with pancreatic cancer cells and fibroblasts induced the production of immunosuppressive cytokines which are known to promote polarization of M2 like macrophages and myeloid derived suppressive cells (MDSCs). These co-culture spheroid polarized monocyte derived macrophages (MDMs) were poorly differentiated and had an M2 phenotype. The immunosuppressive function of these co-culture spheroids polarized MDMs was demonstrated by their ability to inhibit CD4+ and CD8+ T cell activation and proliferation in vitro, which we could partially reverse by 3D co-culture spheroid treatment with therapeutic molecules that are able to re-activated spheroid polarized MDMs or block immune suppressive factors such as Arginase-I.

A phase I trial combining decitabine/dendritic cell vaccine targeting MAGE-A1, MAGE-A3 and NY-ESO-1 for children with relapsed or therapy-refractory neuroblastoma and sarcoma

Antigen-specific immunotherapy was studied in a multi-institutional phase 1/2 study by combining decitabine (DAC) followed by an autologous dendritic cell (DC)/MAGE-A1, MAGE-A3 and NY-ESO-1 peptide vaccine in children with relapsed/refractory solid tumors. Patients aged 2.5-15 years with relapsed neuroblastoma, Ewing's sarcoma, osteosarcoma and rhabdomyosarcoma were eligible to receive DAC followed by DC pulsed with overlapping peptides derived from full-length MAGE-A1, MAGE-A3 and NY-ESO-1. The primary endpoints were to assess the feasibility and tolerability of this regimen. Each of four cycles consisted of week 1: DAC 10 mg/m(2)/day for 5 days and weeks 2 and 3: DC vaccine once weekly. Fifteen patients were enrolled in the study, of which 10 were evaluable. Generation of DC was highly feasible for all enrolled patients. The treatment regimen was generally well tolerated, with the major toxicity being DAC-related myelosuppression in 5/10 patients. Six of nine patients developed a response to MAGE-A1, MAGE-A3 or NY-ESO-1 peptides post-vaccine. Due to limitations in number of cells available for analysis, controls infected with a virus encoding relevant genes have not been performed. Objective responses were documented in 1/10 patients who had a complete response. Of the two patients who had no evidence of disease at the time of treatment, one remains disease-free 2 years post-therapy, while the other experienced a relapse 10 months post-therapy. The chemoimmunotherapy approach using DAC/DC-CT vaccine is feasible, well tolerated and results in antitumor activity in some patients. Future trials to maximize the likelihood of T cell responses post-vaccine are warranted.