Harnessing the physiology of lymphopenia to support adoptive immunotherapy in lymphoreplete hosts

Chimeric Antigen Receptor T-Cells: An Overview of Concepts, Applications, Limitations, and Proposed Solutions

Adaptive immunity, orchestrated by B-cells and T-cells, plays a crucial role in protecting the body from pathogenic invaders and can be used as tools to enhance the body's defense mechanisms against cancer by genetically engineering these immune cells. Several strategies have been identified for cancer treatment and evaluated for their efficacy against other diseases such as autoimmune and infectious diseases. One of the most advanced technologies is chimeric antigen receptor (CAR) T-cell therapy, a pioneering therapy in the oncology field. Successful clinical trials have resulted in the approval of six CAR-T cell products by the Food and Drug Administration for the treatment of hematological malignancies. However, there have been various obstacles that limit the use of CAR T-cell therapy as the first line of defense mechanism against cancer. Various innovative CAR-T cell therapeutic designs have been evaluated in preclinical and clinical trial settings and have demonstrated much potential for development. Such trials testing the suitability of CARs against solid tumors and HIV are showing promising results. In addition, new solutions have been proposed to overcome the limitations of this therapy. This review provides an overview of the current knowledge regarding this novel technology, including CAR T-cell structure, different applications, limitations, and proposed solutions.

Time 2EVOLVE: predicting efficacy of engineered T-cells - how far is the bench from the bedside?

Immunotherapy with gene engineered CAR and TCR transgenic T-cells is a transformative treatment in cancer medicine. There is a rich pipeline with target antigens and sophisticated technologies that will enable establishing this novel treatment not only in rare hematological malignancies, but also in common solid tumors. The T2EVOLVE consortium is a public private partnership directed at accelerating the preclinical development of and increasing access to engineered T-cell immunotherapies for cancer patients. A key ambition in T2EVOLVE is to assess the currently available preclinical models for evaluating safety and efficacy of engineered T cell therapy and developing new models and test parameters with higher predictive value for clinical safety and efficacy in order to improve and accelerate the selection of lead T-cell products for clinical translation. Here, we review existing and emerging preclinical models that permit assessing CAR and TCR signaling and antigen binding, the access and function of engineered T-cells to primary and metastatic tumor ligands, as well as the impact of endogenous factors such as the host immune system and microbiome. Collectively, this review article presents a perspective on an accelerated translational development path that is based on innovative standardized preclinical test systems for CAR and TCR transgenic T-cell products.

Effectiveness and Safety of Anti-CD19 Chimeric Antigen Receptor-T Cell Immunotherapy in Patients With Relapsed/Refractory Large B-Cell Lymphoma: A Systematic Review and Meta-Analysis

Aim: To investigate the effectiveness and safety of using chimeric antigen receptor (CAR) T cell therapies targeting CD19 in patients with diffuse large B-cell lymphoma (DLBCL). Methods: PubMed, Embase, and the Cochrane Library were searched for reports published from database inception up to July 2021. The present meta-analysis included clinical response outcomes, survival outcomes, and safety analyses. For qualitative analysis that could not be combined, the data were presented in a tabular form. Subgroup analyses were also performed according to the costimulatory domains, generic names, and study designs. Results: Twenty-seven studies (1,687 patients) were included. The pooled 12-months overall survival (OS) rate was 63% (95%CI: 56-70%). The pooled best overall response (BOR) was 74.0% (95%CI: 67-79%), with a best complete response (BCR) of 48% (95%CI: 42-54%) and a 3-months CR rate (CRR) of 41% (95%CI: 35-47%). The subgroup analyses by costimulatory domain suggested statistically significant differences in BOR and BCR, whereas not in the 12-months OS rate and 3-months CRR. Among the patients evaluable for safety, 78% (95%CI: 68-87%), 6% (95%CI: 3-10%), 41% (95%CI: 31-52%), and 16% (95%CI: 10-24%) experienced cytokine release syndrome (CRS), severe CRS, neurotoxicity, and severe neurotoxicity, respectively. Compared with the CD28 costimulatory domain, the 4-1BB-based products showed a better safety profile on any-grade CRS (p < 0.01), severe CRS (p = 0.04), any-grade neurotoxicity (p < 0.01), and severe neurotoxicity (p < 0.01). Conclusion: Anti-CD19 CAR-T cell immunotherapy has promising effectiveness and tolerable severe AE profile in DLBCL patients. 4-1BB-based CAR-T cells have a similar 12-months OS rate and 3-months CRR with CD28-based products but a better safety profile. The costimulatory domain might not affect the survival outcomes.

Neutrophil-mediated clinical nanodrug for treatment of residual tumor after focused ultrasound ablation

Background

The risk of local recurrence after high-intensity focused ultrasound (HIFU) is relatively high, resulting in poor prognosis of malignant tumors. The combination of HIFU with traditional chemotherapy continues to have an unsatisfactory outcome because of off-site drug uptake.

Results

Herein, we propose a strategy of inflammation-tendency neutrophil-mediated clinical nanodrug targeted therapy for residual tumors after HIFU ablation. We selected neutrophils as carriers and PEGylated liposome doxorubicin (PLD) as a model chemotherapeutic nanodrug to form an innovative cell therapy drug (PLD@NEs). The produced PLD@NEs had a loading capacity of approximately 5 µg of PLD per 10⁶ cells and maintained the natural characteristics of neutrophils. The targeting performance and therapeutic potential of PLD@NEs were evaluated using Hepa1-6 cells and a corresponding tumor-bearing mouse model. After HIFU ablation, PLD@NEs were recruited to the tumor site by inflammation (most in 4 h) and released PLD with inflammatory stimuli, leading to targeted and localized postoperative chemotherapy.

Conclusions

This effective integrated method fully leverages the advantages of HIFU, chemotherapy and neutrophils to attract more focus on the practice of improving existing clinical therapies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01087-w.

The Role of TNFR2 and DR3 in the In Vivo Expansion of Tregs in T Cell Depleting Transplantation Regimens

Regulatory T cells (Tregs) are essential for the maintenance of tolerance to self and non-self through cell-intrinsic and cell-extrinsic mechanisms. Peripheral Tregs survival and clonal expansion largely depend on IL-2 and access to co-stimulatory signals such as CD28. Engagement of tumor necrosis factor receptor (TNFR) superfamily members, in particular TNFR2 and DR3, contribute to promote peripheral Tregs expansion and sustain their survival. This property can be leveraged to enhance tolerance to allogeneic transplants by tipping the balance of Tregs over conventional T cells during the course of immune reconstitution. This is of particular interest in peri-transplant tolerance induction protocols in which T cell depletion is applied to reduce the frequency of alloreactive T cells or in conditioning regimens that allow allogeneic bone marrow transplantation. These conditioning regimens are being implemented to limit long-term side effects of continuous immunosuppression and facilitate the establishment of a state of donor-specific tolerance. Lymphopenia-induced homeostatic proliferation in response to cytoreductive conditioning is a window of opportunity to enhance preferential expansion of Tregs during homeostatic proliferation that can be potentiated by agonist stimulation of TNFR.

CAR T Cell Therapy for Neuroblastoma

Patients with high risk neuroblastoma have a poor prognosis and survivors are often left with debilitating long term sequelae from treatment. Even after integration of anti-GD2 monoclonal antibody therapy into standard, upftont protocols, 5-year overall survival rates are only about 50%. The success of anti-GD2 therapy has proven that immunotherapy can be effective in neuroblastoma. Adoptive transfer of chimeric antigen receptor (CAR) T cells has the potential to build on this success. In early phase clinical trials, CAR T cell therapy for neuroblastoma has proven safe and feasible, but significant barriers to efficacy remain. These include lack of T cell persistence and potency, difficulty in target identification, and an immunosuppressive tumor microenvironment. With recent advances in CAR T cell engineering, many of these issues are being addressed in the laboratory. In this review, we summarize the clinical trials that have been completed or are underway for CAR T cell therapy in neuroblastoma, discuss the conclusions and open questions derived from these trials, and consider potential strategies to improve CAR T cell therapy for patients with neuroblastoma.

The efficacy and safety of anti-CD19/CD20 chimeric antigen receptor- T cells immunotherapy in relapsed or refractory B-cell malignancies:a meta-analysis

BACKGROUND

Chimeric antigen receptor T (CAR T) cells immunotherapy is rapidly developed in treating cancers, especially relapsed or refractory B-cell malignancies.

METHODS

To assess the efficacy and safety of CAR T therapy, we analyzed clinical trials from PUBMED and EMBASE.

RESULTS

Results showed that the pooled response rate, 6-months and 1-year progression-free survival (PFS) rate were 67%, 65.62% and 44.18%, respectively. We observed that received lymphodepletion (72% vs 44%, P = 0.0405) and high peak serum IL-2 level (85% vs 31%, P = 0.04) were positively associated with patients' response to CAR T cells. Similarly, costimulatory domains (CD28 vs CD137) in second generation CAR T was positively associated with PFS (52.69% vs 33.39%, P = 0.0489). The pooled risks of all grade adverse effects (AEs) and grade ≥ 3 AEs were 71% and 43%. Most common grade ≥ 3 AEs were fatigue (18%), night sweats (14%), hypotension (12%), injection site reaction (12%), leukopenia (10%), anemia (9%).

CONCLUSIONS

In conclusion, CAR T therapy has promising outcomes with tolerable AEs in relapsed or refractory B-cell malignancies. Further modifications of CAR structure and optimal therapy strategy in continued clinical trials are needed to obtain significant improvements.

Tumor Antigen Escape from CAR T-cell Therapy

Emerging data from chimeric antigen receptor (CAR) T-cell trials in B-cell malignancies demonstrate that a common mechanism of resistance to this novel class of therapeutics is the emergence of tumors with loss or downregulation of the target antigen. Antigen loss or antigen-low escape is likely to emerge as an even greater barrier to success in solid tumors, which manifest greater heterogeneity in target antigen expression. Potential approaches to overcome this challenge include engineering CAR T cells to achieve multispecificity and to respond to lower levels of target antigen and more efficient induction of natural antitumor immune responses as a result of CAR-induced inflammation. In this article, we review the evidence to date for antigen escape and downregulation and discuss approaches currently under study to overcome these obstacles.Significance: Antigen escape and downregulation have emerged as major issues impacting the durability of CAR T-cell therapy. Here, we explore their incidence and ways to overcome these obstacles in order to improve clinical outcomes. Cancer Discov; 8(10); 1219-26. ©2018 AACR.

IL-2 and Beyond in Cancer Immunotherapy

The development of the T- and natural killer (NK) cell growth factor IL-2 has been a sentinel force ushering in the era of immunotherapy in cancer. With the advent of clinical grade recombinant IL-2 in the mid-1980s, oncologists could for the first time directly manipulate lymphocyte populations with systemic therapy. By itself, recombinant IL-2 can induce clinical responses in up to 15% of patients with metastatic cancer or renal cell carcinoma. When administered with adoptively transferred tumor-reactive lymphocytes, IL-2 promotes T cell engraftment and response rates of up to 50% in metastatic melanoma patients. Importantly, these IL-2-driven responses can yield complete and durable responses in a subset of patients. However, the use of IL-2 is limited by toxicity and concern of the expansion of T regulatory cells. To overcome these limitations and improve response rates, other T cell growth factors, including IL-15 and modified forms of IL-2, are in clinical development. Administering T cell growth factors in combination with other agents, such as immune checkpoint pathway inhibitors, may also improve efficacy. In this study, we review the development of T- and NK cell growth factors and highlight current combinatorial approaches based on these reagents.

Ezh2 phosphorylation state determines its capacity to maintain CD8+ T memory precursors for antitumor immunity

Memory T cells sustain effector T-cell production while self-renewing in reaction to persistent antigen; yet, excessive expansion reduces memory potential and impairs antitumor immunity. Epigenetic mechanisms are thought to be important for balancing effector and memory differentiation; however, the epigenetic regulator(s) underpinning this process remains unknown. Herein, we show that the histone methyltransferase Ezh2 controls CD8⁺ T memory precursor formation and antitumor activity. Ezh2 activates Id3 while silencing Id2, Prdm1 and Eomes, promoting the expansion of memory precursor cells and their differentiation into functional memory cells. Akt activation phosphorylates Ezh2 and decreases its control of these transcriptional programs, causing enhanced effector differentiation at the expense of T memory precursors. Engineering T cells with an Akt-insensitive Ezh2 mutant markedly improves their memory potential and capability of controlling tumor growth compared to transiently inhibiting Akt. These findings establish Akt-mediated phosphorylation of Ezh2 as a critical target to potentiate antitumor immunotherapeutic strategies.

During an immune response naive CD8⁺ T cells can differentiate into either effector or memory T cells. Here the authors show that Akt-mediated phosphorylation of the epigenetic regulator Ezh2 is critical for the generation of an anti-tumor CD8 T cell response and promotes the expansion of memory-precursors.

Inducible Activation of MyD88 and CD40 in CAR T Cells Results in Controllable and Potent Antitumor Activity in Preclinical Solid Tumor Models

Adoptive immunotherapy with T cells expressing chimeric antigen receptors (CAR) has had limited success for solid tumors in early-phase clinical studies. We reasoned that introducing into CAR T cells an inducible costimulatory (iCO) molecule consisting of a chemical inducer of dimerization (CID)-binding domain and the MyD88 and CD40 signaling domains would improve and control CAR T-cell activation. In the presence of CID, T cells expressing HER2-CARζ and a MyD88/CD40-based iCO molecule (HER2ζ.iCO T cells) had superior T-cell proliferation, cytokine production, and ability to sequentially kill targets in vitro relative to HER2ζ.iCO T cells without CID and T cells expressing HER2-CAR.CD28ζ. HER2ζ.iCO T cells with CID also significantly improved survival in vivo in two xenograft models. Repeat injections of CID were able to further increase the antitumor activity of HER2ζ.iCO T cells in vivo Thus, expressing MyD88/CD40-based iCO molecules in CAR T cells has the potential to improve the efficacy of CAR T-cell therapy approaches for solid tumors.Significance: Inducible activation of MyD88 and CD40 in CAR T cells with a small-molecule drug not only enhances their effector function, resulting in potent antitumor activity in preclinical solid tumors, but also enables their remote control post infusion. Cancer Discov; 7(11); 1306-19. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 1201.

When the guardian sleeps: Reactivation of the p53 pathway in cancer

The p53 tumor suppressor is inactivated in most cancers, thus suggesting that loss of p53 is a prerequisite for tumor growth. Therefore, its reintroduction through different means bears great clinical potential. After a brief introduction to current knowledge of p53 and its regulation by the ubiquitin-ligases MDM2/MDMX and post-translational modifications, we will discuss small molecules that are able to reactivate specific, frequently observed mutant forms of p53 and their applicability for clinical purposes. Many malignancies display amplification of MDM genes encoding negative regulators of p53 and therefore much effort to date has concentrated on the development of molecules that inhibit MDM2, the most advanced of which are being tested in clinical trials for sarcoma, glioblastoma, bladder cancer and lung adenocarcinoma. These will be discussed as will recent findings of MDMX inhibitors: these are of special importance as it has been shown that cancers that become resistant to MDM2 inhibitors often amplify MDM4. Finally, we will also touch on gene therapy and vaccination approaches; the former of which aims to replace mutated TP53 and the latter whose goal is to activate the body's immune system toward mutant p53 expressing cells. Besides the obvious importance of MDM2 and MDMX expression for regulation of p53, other regulatory factors should not be underestimated and are also described. Despite the beauty of the concept, the past years have shown that many obstacles have to be overcome to bring p53 reactivation to the clinic on a broad scale, and it is likely that in most cases it will be part of a combined therapeutic approach. However, improving current p53 targeted molecules and finding the best therapy partners will clearly impact the future of cancer therapy.

Making Better Chimeric Antigen Receptors for Adoptive T-cell Therapy

Chimeric antigen receptors (CAR) are engineered fusion proteins constructed from antigen recognition, signaling, and costimulatory domains that can be expressed in cytotoxic T cells with the purpose of reprograming the T cells to specifically target tumor cells. CAR T-cell therapy uses gene transfer technology to reprogram a patient's own T cells to stably express CARs, thereby combining the specificity of an antibody with the potent cytotoxic and memory functions of a T cell. In early-phase clinical trials, CAR T cells targeting CD19 have resulted in sustained complete responses within a population of otherwise refractory patients with B-cell malignancies and, more specifically, have shown complete response rates of approximately 90% in patients with relapsed or refractory acute lymphoblastic leukemia. Given this clinical efficacy, preclinical development of CAR T-cell therapy for a number of cancer indications has been actively investigated, and the future of the CAR T-cell field is extensive and dynamic. Several approaches to increase the feasibility and safety of CAR T cells are currently being explored, including investigation into the mechanisms regulating the persistence of CAR T cells. In addition, numerous early-phase clinical trials are now investigating CAR T-cell therapy beyond targeting CD19, especially in solid tumors. Trials investigating combinations of CAR T cells with immune checkpoint blockade therapies are now beginning and results are eagerly awaited. This review evaluates several of the ongoing and future directions of CAR T-cell therapy.

Heterodimeric IL15 Treatment Enhances Tumor Infiltration, Persistence, and Effector Functions of Adoptively Transferred Tumor-specific T Cells in the Absence of Lymphodepletion

Purpose: Adoptive cell transfer (ACT) is a promising immunotherapeutic approach for cancer. Host lymphodepletion is associated with favorable ACT therapy outcomes, but it may cause detrimental effects in humans. We tested the hypothesis that IL15 administration enhances ACT in the absence of lymphodepletion. We previously showed that bioactive IL15 in vivo comprises a stable complex of the IL15 chain with the IL15 receptor alpha chain (IL15Rα), termed heterodimeric IL15 (hetIL15).Experimental Design: We evaluated the effects of the combination regimen ACT + hetIL15 in the absence of lymphodepletion by transferring melanoma-specific Pmel-1 T cells into B16 melanoma-bearing mice.Results: hetIL15 treatment delayed tumor growth by promoting infiltration and persistence of both adoptively transferred Pmel-1 cells and endogenous CD8⁺ T cells into the tumor. In contrast, persistence of Pmel-1 cells was severely reduced following irradiation in comparison with mice treated with hetIL15. Importantly, we found that hetIL15 treatment led to the preferential enrichment of Pmel-1 cells in B16 tumor sites in an antigen-dependent manner. Upon hetIL15 administration, tumor-infiltrating Pmel-1 cells showed a "nonexhausted" effector phenotype, characterized by increased IFNγ secretion, proliferation, and cytotoxic potential and low level of PD-1. hetIL15 treatment also resulted in an improved ratio of Pmel-1 to Treg in the tumor.Conclusions: hetIL15 administration improves the outcome of ACT in lymphoreplete hosts, a finding with significant implications for improving cell-based cancer immunotherapy strategies. Clin Cancer Res; 23(11); 2817-30. ©2016 AACR.

Efficiency of CD19 chimeric antigen receptor-modified T cells for treatment of B cell malignancies in phase I clinical trials: a meta-analysis

Chimeric antigen receptor (CAR) modified T cells targeted CD19 showed promising clinical outcomes in treatment of B cell malignances such as chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia (ALL) and other indolent lymphomas. However, the clinical benefit varies tremendously among different trials. This meta-analysis investigated the efficacy (response rates and survival time) of CD19-CAR T cells in refractory B cell malignances in Phase I clinical trials. We searched publications between 1991 and 2014 from PubMed and Web of Science. Pooled response rates were calculated using random-effects models. Heterogeneity was investigated by subgroup analysis and meta-regression. Fourteen clinical trials including 119 patients were eligible for response rate evaluation, 62 patients in 12 clinical trials were eligible for progression-free survival analysis. The overall pooled response rate of CD19-CAR T cells was 73% (95% confidence interval [CI]: 46-94%). Significant heterogeneity across estimates of response rates was observed (p < 0.001, I2=88.3%). ALL patients have higher response rate (93%, 95% CI: 65-100%) than CLL (62%, 95% CI: 27-93%) and lymphoma patients (36%, 95% CI: 1-83%). Meta-regression analysis identified lymphodepletion and no IL-2 administrated T cells as two key factors associated with better clinical response. Lymphodepletion and higher infused CAR T cell number were associated with better prognosis. In conclusion, this meta-analysis showed a high clinical response rate of CD19-CAR T cell-based immunotherapy in treatment of refractory B cell malignancies. Lymphodepletion and increasing number of infused CD19-CAR T cells have positive correlations with the clinical efficiency, on the contrary, IL-2 administration to T cells is not recommended.

Interleukin-7 Modulates Anti-Tumor CD8+ T Cell Responses via Its Action on Host Cells

The adoptive transfer of antigen-specific CD8+ T cells is a promising approach for the treatment of chronic viral and malignant diseases. In order to improve adoptive T cell therapy (ATT) of cancer, recent strategies aim at the antibody-based blockade of immunosuppressive signaling pathways in CD8+ T cells. Alternatively, adjuvant effects of immunostimulatory cytokines might be exploited to improve therapeutic CD8+ T cell responses. For example, Interleukin-7 (IL-7) is a potent growth, activation and survival factor for CD8+ T cells that can be used to improve virus- and tumor-specific CD8+ T cell responses. Although direct IL-7 effects on CD8+ T cells were studied extensively in numerous models, the contribution of IL-7 receptor-competent (IL-7R+) host cells remained unclear. In the current study we provide evidence that CD8+ T cell-mediated tumor rejection in response to recombinant IL-7 (rIL-7) therapy is strictly dependent on IL-7R+ host cells. On the contrary, CD8+ T cell expansion is independent of host IL-7R expression. If, however, rIL-7 therapy and peptide vaccination are combined, host IL-7R signaling is crucial for CD8+ T cell expansion. Unexpectedly, maximum CD8+ T cell expansion relies mainly on IL-7R signaling in non-hematopoietic host cells, similar to the massive accumulation of dendritic cells and granulocytes. In summary, we provide evidence that IL-7R+ host cells are major targets of rIL-7 that modulate therapeutic CD8+ T cell responses and the outcome of rIL-7-assisted ATT. This knowledge may have important implications for the design and optimization of clinical ATT protocols.

T-cell receptor gene therapy--ready to go viral?

T lymphocytes can be redirected to recognize a tumor target and harnessed to combat cancer by genetic introduction of T-cell receptors of a defined specificity. This approach has recently mediated encouraging clinical responses in patients with cancers previously regarded as incurable. However, despite the great promise, T-cell receptor gene therapy still faces a multitude of obstacles. Identification of epitopes that enable effective targeting of all the cells in a heterogeneous tumor while sparing normal tissues remains perhaps the most demanding challenge. Experience from clinical trials has revealed the dangers associated with T-cell receptor gene therapy and highlighted the need for reliable preclinical methods to identify potentially hazardous recognition of both intended and unintended epitopes in healthy tissues. Procedures for manufacturing large and highly potent T-cell populations can be optimized to enhance their antitumor efficacy. Here, we review the current knowledge gained from preclinical models and clinical trials using adoptive transfer of T-cell receptor-engineered T lymphocytes, discuss the major challenges involved and highlight potential strategies to increase the safety and efficacy to make T-cell receptor gene therapy a standard-of-care for large patient groups.

Immune-based therapies for childhood cancer

After decades of research, immunotherapies for cancer are demonstrating increasing success. These agents can amplify existent antitumour immunity or induce durable antitumour immune responses in a wide array of cancers. The spectrum of immunotherapeutics is broad, spanning monoclonal antibodies and their derivatives, tumour vaccines, and adoptive therapies using T cells and natural killer cells. Only a small number of immunotherapies have been tested in paediatric cancers, but impressive antitumour effects have already been observed. Mononclonal antibodies targeting GD2 that induce antibody-dependent cell-mediated cytotoxicity improve survival in high-risk neuroblastoma. Bi-specific monoclonal antibodies that simultaneously target CD19 and activate T cells can induce remission in acute B-cell lymphoblastic leukaemia (B-ALL) and adoptive immunotherapy using T cells genetically engineered to express chimeric antigen receptors targeting CD19 induce impressive responses in B-ALL. Efforts are underway to generate and test new immunotherapies in a wider array of paediatric cancers. Major challenges include a need to identify immunotherapy targets on the most lethal childhood cancers, to expand availability of technology-intense platforms, such as adoptive cell therapy, to optimize management of novel toxicities associated with this new class of cancer therapies and to determine how best to incorporate these therapies into standard treatment paradigms.

Identification of the genomic insertion site of Pmel-1 TCR α and β transgenes by next-generation sequencing

The pmel-1 T cell receptor transgenic mouse has been extensively employed as an ideal model system to study the mechanisms of tumor immunology, CD8⁺ T cell differentiation, autoimmunity and adoptive immunotherapy. The ‘zygosity’ of the transgene affects the transgene expression levels and may compromise optimal breeding scheme design. However, the integration sites for the pmel-1 mouse have remained uncharacterized. This is also true for many other commonly used transgenic mice created before the modern era of rapid and inexpensive next-generation sequencing. Here, we show that whole genome sequencing can be used to determine the exact pmel-1 genomic integration site, even with relatively ‘shallow’ (8X) coverage. The results were used to develop a validated polymerase chain reaction-based genotyping assay. For the first time, we provide a quick and convenient polymerase chain reaction method to determine the dosage of pmel-1 transgene for this freely and publically available mouse resource. We also demonstrate that next-generation sequencing provides a feasible approach for mapping foreign DNA integration sites, even when information of the original vector sequences is only partially known.

A pan-inhibitor of DASH family enzymes induces immune-mediated regression of murine sarcoma and is a potent adjuvant to dendritic cell vaccination and adoptive T-cell therapy

Multimodality therapy consisting of surgery, chemotherapy, and radiation will fail in approximately 40% of patients with pediatric sarcomas and result in substantial long-term morbidity in those who are cured. Immunotherapeutic regimens for the treatment of solid tumors typically generate antigen-specific responses too weak to overcome considerable tumor burden and tumor suppressive mechanisms and are in need of adjuvant assistance. Previous work suggests that inhibitors of DASH (dipeptidyl peptidase IV activity and/or structural homologs) enzymes can mediate tumor regression by immune-mediated mechanisms. Herein, we demonstrate that the DASH inhibitor, ARI-4175, can induce regression and eradication of well-established solid tumors, both as a single agent and as an adjuvant to a dendritic cell (DC) vaccine and adoptive cell therapy (ACT) in mice implanted with the M3-9-M rhabdomyosarcoma cell line. Treatment with effective doses of ARI-4175 correlated with recruitment of myeloid (CD11b) cells, particularly myeloid DCs, to secondary lymphoid tissues and with reduced frequency of intratumoral monocytic (CD11bLy6-CLy6-G) myeloid-derived suppressor cells. In immunocompetent mice, combining ARI-4175 with a DC vaccine or ACT with tumor-primed T cells produced significant improvements in tumor responses against well-established M3-9-M tumors. In M3-9-M-bearing immunodeficient (Rag1) mice, ACT combined with ARI-4175 produced greater tumor responses and significantly improved survival compared with either treatment alone. These studies warrant the clinical investigation of ARI-4175 for treatment of sarcomas and other malignancies, particularly as an adjuvant to tumor vaccines and ACT.

Current vaccine trials in glioblastoma: a review

Glioblastoma (GBM) is the most common primary brain tumor, and despite aggressive therapy with surgery, radiation, and chemotherapy, average survival remains at about 1.5 years. The highly infiltrative and invasive nature of GBM requires that alternative treatments for this disease be widespread and targeted to tumor cells. Immunotherapy in the form of tumor vaccines has the potential to meet this need. Vaccines against GBM hold the promise of triggering specific and systemic antitumor immune responses that may be the key to eradicating this unrelenting cancer. In this review, we will discuss past and present clinical trials of various GBM vaccines and their potential impact on the future care of GBM patients. There have been many promising phase I and phase II GBM vaccine studies that have led to ongoing and upcoming phase III trials. If the results of these randomized trials show a survival benefit, immunotherapy will become a standard part of the treatment of this devastating disease.

Regimen-specific effects of RNA-modified chimeric antigen receptor T cells in mice with advanced leukemia

Cytotoxic T lymphocytes modified with chimeric antigen receptors (CARs) for adoptive immunotherapy of hematologic malignancies have demonstrated activity in early phase clinical trials. While T cells bearing stably expressed CARs are efficacious and have potential long-term persistence, temporary expression of a CAR via RNA electroporation is also potentially efficacious in preclinical models. Temporary CAR expression using RNA presents a method of testing CARs clinically with additional safety where there may be concerns about possible chronic "on-target, off-tumor" toxic effects, as the degradation of RNA ensures complete removal of the CAR over time without relying on suicide induction systems. CD19-directed RNA CAR T cells were tested in vivo for efficacy and comparison to lentiviral vector (LV)-generated stable CAR T cells. We tested the hypothesis that multiple infusions of RNA CAR T cells preceded by lymphodepleting chemotherapy could mediate improved survival and sustained antitumor responses in a robust leukemia xenograft model. The saturation strategy using rationally designed multiple infusions of RNA CARs based on multiple model iterations approached the efficacy of a stable LV expression method. Two-color imaging revealed that relapse was a locoregional phenomenon in both the temporary and the stable expression models. In marked contrast to stably expressed CARs with retroviral or LV technology, the efficacy of RNA CARs appears independent of the costimulatory signaling endodomains likely because they more influence proliferation and persistence rather than short-term efficacy. The efficacy of the RNA CAR infusions may approach that of stably expressed CARs, offer theoretically safer initial clinical testing in addition to suicide systems, and allow for rapid and effective iterative preclinical modeling for the testing of new targets.

CARs in chronic lymphocytic leukemia -- ready to drive

Adoptive transfer of antigen-specific T cells has been adapted by investigators for treatment of chronic lymphocytic leukemia (CLL). To overcome issues of immune tolerance which limits the endogenous adaptive immune response to tumor-associated antigens (TAAs), robust systems for the genetic modification and characterization of T cells expressing chimeric antigen receptors (CARs) to redirect specificity have been produced. Refinements with regards to persistence and trafficking of the genetically modified T cells are underway to help improve potency. Clinical trials utilizing this technology demonstrate feasibility, and increasingly, these early-phase trials are demonstrating impressive anti-tumor effects, particularly for CLL patients, paving the way for multi-center trials to establish the efficacy of CAR(+) T cell therapy.

HDAC inhibition suppresses primary immune responses, enhances secondary immune responses, and abrogates autoimmunity during tumor immunotherapy

Histone deacetylase inhibitors (HDACi) can modulate innate antiviral responses and render tumors more susceptible to oncolytic viruses (OVs); however, their effects on adaptive immunity in this context are largely unknown. Our present study reveals an unexpected property of the HDACi MS-275 that enhances viral vector-induced lymphopenia leading to selective depletion of bystander lymphocytes and regulatory T cells while allowing expansion of antigen-specific secondary responses. Coadministration of vaccine plus drug during the boosting phase focuses the immune response on the tumor by suppressing the primary immune response against the vaccine vector and enhancing the secondary response against the tumor antigen. Furthermore, improvement of T cell functionality was evident suggesting that MS-275 can orchestrate a complex array of effects that synergize immunotherapy and viral oncolysis. Surprisingly, while MS-275 dramatically enhanced efficacy, it suppressed autoimmune pathology, profoundly improving the therapeutic index.

Immunologic privilege in the central nervous system and the blood-brain barrier

The brain is in many ways an immunologically and pharmacologically privileged site. The blood-brain barrier (BBB) of the cerebrovascular endothelium and its participation in the complex structure of the neurovascular unit (NVU) restrict access of immune cells and immune mediators to the central nervous system (CNS). In pathologic conditions, very well-organized immunologic responses can develop within the CNS, raising important questions about the real nature and the intrinsic and extrinsic regulation of this immune privilege. We assess the interactions of immune cells and immune mediators with the BBB and NVU in neurologic disease, cerebrovascular disease, and intracerebral tumors. The goals of this review are to outline key scientific advances and the status of the science central to both the neuroinflammation and CNS barriers fields, and highlight the opportunities and priorities in advancing brain barriers research in the context of the larger immunology and neuroscience disciplines. This review article was developed from reports presented at the 2011 Annual Blood-Brain Barrier Consortium Meeting.

Efficacy and safety of adoptive immunotherapy using anti-CD19 chimeric antigen receptor transduced T-cells: a systematic review of phase I clinical trials

There remain some key questions regarding the adoptive infusion of chimeric antigen receptor (CAR) transduced T-cells in the clinical setting. This article systematically reviews the phase I clinical trials using CARs targeting CD19 in B-lineage malignancies. Twenty-nine patients were enrolled and the 6-month progression free survival for this cohort was 50.0 ± 9.9%. Univariate analysis showed that patients benefited from lymphodepletion before CAR+T-cell infusion and the administration of interleukin-2 (IL-2). Longer-term persistence (≥ 4 weeks) and stronger expansion of CAR+ T-cells in the blood and higher peak serum interferon-γ (IFN-γ) level (≥ 200 pg/mL) were also related to superior outcome. Regarding treatment-related adverse events, the most prominent toxicities were fever, rigors, chills, acute renal failure, hypotension and capillary leak syndrome. In conclusion, anti-CD19 CAR+ T-cells have shown some benefits in patients with B-lineage malignancies and are well tolerated in most patients. Preconditioning and cytokine supplement are required to improve the clinical outcome.

Immunotherapy for B-Cell Neoplasms using T Cells expressing Chimeric Antigen Receptors: From antigen choice to clinical implementation

Immunotherapy with T cells expressing chimeric antigen receptors (CAR) is being evaluated as a potential treatment for B-cell neoplasms. In recent clinical trials it has shown promising results. As the number of potential candidate antigens expands, the choice of suitable target antigens becomes more challenging to design studies and to assess optimal efficacy of CAR. Careful evaluation of candidate target antigens is required to ensure that T cells expressing CAR will preferentially kill malignant cells with a minimal toxicity against normal tissues. B cells express specific surface antigens that can theoretically act as targets for CAR design. Although many of these antigens can stimulate effective cellular immune responses in vivo, their implementation in clinical settings remains a challenge. Only targeted B-cell antigens CD19 and CD20 have been tested in clinical trials. This article reviews exploitable B cell surface antigens for CAR design and examines obstacles that could interfere with the identification of potentially useful cellular targets.

The future is now: chimeric antigen receptors as new targeted therapies for childhood cancer

Improved outcomes for children with cancer hinge on the development of new targeted therapies with acceptable short-term and long-term toxicity. Progress in basic, preclinical, and clinical arenas spanning cellular immunology, gene therapy, and cell-processing technologies have paved the way for clinical applications of chimeric antigen receptor-based therapies. This is a new form of targeted immunotherapy that merges the exquisite targeting specificity of monoclonal antibodies with the potent cytotoxicity, potential for expansion, and long-term persistence provided by cytotoxic T cells. Although this field is still in its infancy, clinical trials have already shown clinically significant antitumor activity in neuroblastoma, chronic lymphocytic leukemia, and B-cell lymphoma, and trials targeting a variety of other adult and pediatric malignancies are under way. Ongoing work is focused on identifying optimal tumor targets and elucidating and manipulating both cell- and host-associated factors to support expansion and persistence of the genetically engineered cells in vivo. In pediatric oncology, CD19 and GD2 are compelling antigens that have already been identified for targeting pre-B acute lymphoblastic leukemia and neuroblastoma, respectively, with this approach, but it is likely that other antigens expressed in a variety of childhood cancers will also soon be targeted using this therapy. The potential to target essentially any tumor-associated cell-surface antigen for which a monoclonal antibody can be made opens up an entirely new arena for targeted therapy of childhood cancer.

Murine rhabdomyosarcoma is immunogenic and responsive to T-cell-based immunotherapy

BACKGROUND

Immunotherapies targeting cellular immunity are currently approved for treatment of melanoma, renal cell carcinoma, and prostate cancer. Studies on the immunogenicity and immune responsiveness of pediatric tumors are limited, therefore, it remains unclear to what extent T-cell-based immunotherapy holds promise for pediatric solid tumors.

PROCEDURE

A new rhabdomyosarcoma cell line (M3-9-M) was derived from an embryonal rhabdomyosarcoma (ERMS) occurring in a C57BL/6 mouse transgenic for hepatocyte growth factor and heterozygous for mutated p53. Primary tumors and metastases derived from M3-9-M were studied for similarities to human ERMS, and for immunogenicity and immune responsiveness.

RESULTS

Primary and metastatic tumors develop after orthotopic injection of M3-9-M into immunocompetent C57BL/6 mice, which mirror human ERMS with regard to histology, gene expression, and metastatic behavior. Whole cell vaccination using irradiated M3-9-M cells or M3-9-M-pulsed dendritic cells (DC)-induced tumor-specific T-cell responses that prevent tumor growth following low-dose tumor injection, and slow tumor growth following higher doses. Administration of anti-CD25 moAbs to deplete CD4(+)CD25(+)FOXP3(+) regulatory T cells prior to tumor vaccination enhanced the potency of the ERMS tumor vaccine. Adoptive immunotherapy with M3-9-M primed T cells plus DC-based vaccination resulted in complete eradication of day 10 M3-9-M derived tumors.

CONCLUSIONS

M3-9-M derived murine ERMS is immunogenic and immunoresponsive; regulatory T cells contribute to immune evasion by murine rhabdomyosarcoma. Adoptive immunotherapy with DC vaccination can eradicate low tumor burdens. Future work will seek to identify the tumor-associated antigens that mediate protective and therapeutic immunity in this model.

Highlights of the second international conference on "Immunotherapy in Pediatric Oncology"

The Second International Conference on Immunotherapy in Pediatric Oncology was held in Houston, Texas, USA, October 11-12, 2010, to discuss the progress and challenges that have occurred in cutting edge immunotherapeutic strategies currently being developed for pediatric oncology. Major topics included immune targeting of acute lymphoblastic leukemia and pediatric solid tumors, chimeric antigen receptors (CARs) for hematologic malignancies and solid tumors, enhancing graft-versus-leukemia for pediatric cancers, overcoming hurdles of immunotherapy, strategies to active the innate immune system, and moving immunotherapy beyond phase I studies. Significant progress has been made in the last 2 years both in the development of novel immunobiologics such as CARs, and in establishing survival benefits of an anti-GD2 monoclonal antibody in randomized studies. Although there is much excitement going forward, a great deal of laboratory and regulatory challenges lie ahead in improving the efficacy of each of these modalities as well as getting them to patients in a timely and cost-effective fashion. The resulting discussions will hopefully lead to new collaborations and insight for further translational and clinical studies.

Engineered T cells for the adoptive therapy of B-cell chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (B-CLL) remains an incurable disease due to the high risk of relapse, even after complete remission, raising the need to control and eliminate residual tumor cells in long term. Adoptive T cell therapy with genetically engineered specificity is thought to fulfil expectations, and clinical trials for the treatment of CLL are initiated. Cytolytic T cells from patients are redirected towards CLL cells by ex vivo engineering with a chimeric antigen receptor (CAR) which binds to CD19 on CLL cells through an antibody-derived domain and triggers T cell activation through CD3ζ upon tumor cell engagement. Redirected T cells thereby target CLL cells in an MHC-unrestricted fashion, secret proinflammatory cytokines, and eliminate CD19(+) leukaemia cells with high efficiency. Cytolysis of autologous CLL cells by patient's engineered T cells is effective, however, accompanied by lasting elimination of healthy CD19(+) B-cells. In this paper we discuss the potential of the strategy in the treatment of CLL, the currently ongoing trials, and the future challenges in the adoptive therapy with CAR-engineered T cells.

Monoclonal antibody blockade of IL-2 receptor α during lymphopenia selectively depletes regulatory T cells in mice and humans

Lymphodepletion augments adoptive cell transfer during antitumor immunotherapy, producing dramatic clinical responses in patients with malignant melanoma. We report that the lymphopenia induced by the chemotherapeutic agent temozolomide (TMZ) enhances vaccine-driven immune responses and significantly reduces malignant growth in an established model of murine tumorigenesis. Unexpectedly, despite the improved antitumor efficacy engendered by TMZ-induced lymphopenia, there was a treatment related increase in the frequency of immunosuppressive regulatory T cells (T(Regs); P = .0006). Monoclonal antibody (mAb)-mediated inhibition of the high-affinity IL-2 receptor α (IL-2Rα/CD25) during immunotherapy in normal mice depleted T(Regs) (73% reduction; P = .0154) but also abolished vaccine-induced immune responses. However, during lymphodepletion, IL-2Rα blockade decreased T(Regs) (93% reduction; P = .0001) without impairing effector T-cell responses, to augment therapeutic antitumor efficacy (66% reduction in tumor growth; P = .0024). Of clinical relevance, we also demonstrate that anti-IL-2Rα mAb administration during recovery from lymphodepletive TMZ in patients with glioblastoma reduced T(Reg) frequency (48% reduction; P = .0061) while permitting vaccine-stimulated antitumor effector cell expansion. To our knowledge, this is the first report of systemic antibody-mediated T(Reg) depletion during lymphopenia and the consequent synergistic enhancement of vaccine-driven cellular responses, as well as the first demonstration that anti-IL-2Rα mAbs function differentially in nonlymphopenic versus lymphopenic contexts.

Homeostatic proliferation of NK cells: friend or foe in cellular immunotherapy?

NK cells are an important tool in cellular immunotherapy owing to their role in infections and antitumor immunity. Until recently, these cells have been thought to be short-lived cytotoxic effectors that are cleared from the body soon after resolution of an immune response. In the commented study, Sun et al. confirmed that, similar to T cells, NK cells sensed the space in the immune system and underwent homeostatic proliferation in order to provide necessary protection to the body. Moreover, homeostatically driven NK cells persisted in the tissues for a long time without loss of activity. These findings have important consequences for immunotherapy, suggesting that the mechanisms of homeostatic expansion can be deployed in order to expand NK cells for therapeutic purposes in vivo. As homeostatically driven NK cells are long-lived effectors, such therapies can exert prolonged effects for the immunity of the patients.

Chimeric Antigen Receptor Therapy for B-cell Malignancies

We presented data showing that the CART-19 cells expressing the 4-1BB signaling domain can have unprecedented and massive in-vivo expansion, traffic to tumor sites, persist long term in vivo, and induce rapid and potent anti-tumor activity in chemotherapy refractory CLL patients.

Tumor-infiltrating immune cells and prognosis: the potential link between conventional cancer therapy and immunity

Numerous studies have now documented a link between the immune infiltrate in several human carcinoma types and prognosis and response to therapy. The most comprehensive of these studies were in colorectal cancer with similar conclusions by numerous groups. Analyses of immune infiltrate of several other carcinoma types also showed general correlations between immune infiltrate and prognosis, but with some conflicting results. This review will attempt to summarize the current state of this field and point out what factors may be responsible for some of the conflicting findings. Nonetheless, the breadth of reports drawing similar conclusions for some cancer cell types leads one to more seriously consider the link between immune cell infiltrate and tumor prognosis and/or response to therapy, and the potential for combining conventional cancer therapy with active immunotherapy employing therapeutic cancer vaccines.

Targeted Therapy of Ewing's Sarcoma

Refractory and/or recurrent Ewing's sarcoma (EWS) remains a clinical challenge because the disease's resistance to therapy makes it difficult to achieve durable results with standard treatments that include chemotherapy, radiation, and surgery. Recently, insulin-like-growth-factor-1-receptor (IGF1R) antibodies have been shown to have a modest single-agent activity in EWS. Patient selection using biomarkers and understanding response and resistance mechanisms in relation to IGF1R and mammalian target of rapamycin pathways are areas of active research. Since EWS has a unique tumor-specific EWS-FLI1 t(11;22) translocation and oncogenic fusion protein, inhibition of EWS-FLI1 transcription, translation, and/or protein function may be key to eradicating EWS at the stem-cell level. Recently, a small molecule that blocks the protein-protein interaction of EWS-FLI1 with RNA helicase A has been shown in preclinical models to inhibit EWS growth. The successful application of this first-in-class protein-protein inhibitor in the clinic could become a model system for translocation-associated cancers such as EWS.

T cell receptor (TCR) gene therapy to treat melanoma: lessons from clinical and preclinical studies

IMPORTANCE OF THE FIELD

Adoptive T cell therapy (ACT) with tumour infiltrating lymphocytes is currently the best treatment option for metastatic melanoma. Despite its clinical successes, ACT has limitations in availability and generation of therapeutic T cells for a larger group of patients. Introduction of tumour-specific T cell receptors into T cells, termed TCR gene therapy, can provide an alternative for ACT that is more widely applicable and might be extended to other types of cancer.

AREAS COVERED IN THIS REVIEW

The current status of TCR gene therapy studies including clinical challenges, such as on-target toxicity, compromised anti-tumour T cell responses, compromised T cell persistence and potential immunogenicity of receptor transgenes. Strategies to address these challenges are covered.

WHAT THE READER WILL GAIN

A listing and discussion of strategies that aim at improving the efficacy and safety of TCR gene therapy. Such strategies address antigen choice, TCR mis-pairing, functional avidity and persistence of T cells, immune responses towards receptor transgenes, and combination of ACT with other therapies.

TAKE HOME MESSAGE

To ensure further clinical development of TCR gene therapy, it is necessary to choose safe T cell target antigens, and implement (combinations of) strategies that enhance the correct pairing of TCR transgenes and the functional avidity and persistence of T cells.

Program death-1 signaling and regulatory T cells collaborate to resist the function of adoptively transferred cytotoxic T lymphocytes in advanced acute myeloid leukemia

Tumor-induced immune defects can weaken host immune response and permit tumor cell growth. In a systemic model of murine acute myeloid leukemia (AML), tumor progression resulted in increased regulatory T cells (Treg) and elevation of program death-1 (PD-1) expression on CD8(+) cytotoxic T cells (CTLs) at the tumor site. PD-1 knockout mice were more resistant to AML despite the presence of similar percentage of Tregs compared with wild type. In vitro, intact Treg suppression of CD8(+) T-cell responses was dependent on PD-1 expression by T cells and Tregs and PD-L1 expression by antigen-presenting cells. In vivo, the function of adoptively transferred AML-reactive CTLs was reduced by AML-associated Tregs. Anti-PD-L1 monoclonal antibody treatment increased the proliferation and function of CTLs at tumor sites, reduced AML tumor burden, and resulted in long-term survivors. Treg depletion followed by PD-1/PD-L1 blockade showed superior efficacy for eradication of established AML. These data demonstrated that interaction between PD-1 and PD-L1 can facilitate Treg-induced suppression of T-effector cells and dampen the antitumor immune response. PD-1/PD-L1 blockade coupled with Treg depletion represents an important new approach that can be readily translated into the clinic to improve the therapeutic efficacy of adoptive AML-reactive CTLs in advanced AML disease.

T-cell-based therapies for malignancy and infection in childhood

One major advance in T-cell-based immunotherapy in the last 20 years has been the molecular definition of numerous viral and tumor antigens. Adoptive T-cell transfer has shown definite clinical benefit in the prophylaxis and treatment of viral infections that develop in pediatric patients after allogeneic transplant and in posttransplant lymphoproliferative disease associated with the Epstein-Barr virus. Developing adoptive T-cell therapies for other malignancies presents additional challenges. This article describes the recent advances in T-cell-based therapies for malignancy and infection in childhood and strategies to enhance the effector functions of T cells and optimize the cellular product, including gene modification and modulation of the host environment.