Leukemia-induced dysfunctional TIM-3+CD4+ bone marrow T cells increase risk of relapse in pediatric B-precursor ALL patients

Immune Microenvironment in Childhood Cancers: Characteristics and Therapeutic Challenges

The tumor immune microenvironment is pivotal in cancer initiation, advancement, and regulation. Its molecular and cellular composition is critical throughout the disease, as it can influence the balance between suppressive and cytotoxic immune responses within the tumor's vicinity. Studies on the tumor immune microenvironment have enriched our understanding of the intricate interplay between tumors and their immunological surroundings in various human cancers. These studies illuminate the role of significant components of the immune microenvironment, which have not been extensively explored in pediatric tumors before and may influence the responsiveness or resistance to therapeutic agents. Our deepening understanding of the pediatric tumor immune microenvironment is helping to overcome challenges related to the effectiveness of existing therapeutic strategies, including immunotherapies. Although in the early stages, targeted therapies that modulate the tumor immune microenvironment of pediatric solid tumors hold promise for improved outcomes. Focusing on various aspects of tumor immune biology in pediatric patients presents a therapeutic opportunity that could improve treatment outcomes. This review offers a comprehensive examination of recent literature concerning profiling the immune microenvironment in various pediatric tumors. It seeks to condense research findings on characterizing the immune microenvironment in pediatric tumors and its impact on tumor development, metastasis, and response to therapeutic modalities. It covers the immune microenvironment's role in tumor development, interactions with tumor cells, and its impact on the tumor's response to immunotherapy. The review also discusses challenges targeting the immune microenvironment for pediatric cancer therapies.

Contribution of the TIME in BCP-ALL: the basis for novel approaches therapeutics

The bone marrow (BM) niche is a microenvironment where both immune and non-immune cells functionally interact with hematopoietic stem cells (HSC) and more differentiated progenitors, contributing to the regulation of hematopoiesis. It is regulated by various signaling molecules such as cytokines, chemokines, and adhesion molecules in its microenvironment. However, despite the strict regulation of BM signals to maintain their steady state, accumulating evidence in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) indicates that leukemic cells can disrupt the physiological hematopoietic niche in the BM, creating a new leukemia-supportive microenvironment. This environment favors immunological evasion mechanisms and the interaction of these cells with the development and progression of BCP-ALL. With a growing understanding of the tumor immune microenvironment (TIME) in the development and progression of BCP-ALL, current strategies focused on "re-editing" TIME to promote antitumor immunity have been developed. In this review, we summarize how TIME cells are disrupted by the presence of leukemic cells, evading immunosurveillance mechanisms in the BCP-ALL model. We also explore the crosstalk between TIME and leukemic cells that leads to treatment resistance, along with the most promising immuno-therapy strategies. Understanding and further research into the role of the BM microenvironment in leukemia progression and relapse are crucial for developing more effective treatments and reducing patient mortality.

CRISPR/Cas9 Landscape: Current State and Future Perspectives

CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 is a unique genome editing tool that can be easily used in a wide range of applications, including functional genomics, transcriptomics, epigenetics, biotechnology, plant engineering, livestock breeding, gene therapy, diagnostics, and so on. This review is focused on the current CRISPR/Cas9 landscape, e.g., on Cas9 variants with improved properties, on Cas9-derived and fusion proteins, on Cas9 delivery methods, on pre-existing immunity against CRISPR/Cas9 proteins, anti-CRISPR proteins, and their possible roles in CRISPR/Cas9 function improvement. Moreover, this review presents a detailed outline of CRISPR/Cas9-based diagnostics and therapeutic approaches. Finally, the review addresses the future expansion of genome editors' toolbox with Cas9 orthologs and other CRISPR/Cas proteins.

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

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

CD38-Specific CAR Integrated into CD38 Locus Driven by Different Promoters Causes Distinct Antitumor Activities of T and NK Cells

The robust and stable expression of CD38 in T-cell acute lymphoblastic leukemia (T-ALL) blasts makes CD38 chimeric antigen receptor (CAR)-T/natural killer (NK) a potential therapy for T-ALL. However, CD38 expression in normal T/NK cells causes fratricide of CD38 CAR-T/NK cells. Here a "2-in-1" gene editing strategy is developed to generate fratricide-resistant locus-specific CAR-T/NK cells. CD38-specific CAR is integrated into the disrupted CD38 locus by CRISPR/Cas9, and CAR is placed under the control of either endogenous CD38 promoter (CD38KO/KI ) or exogenous EF1α promoter (CD38KO/KI EF1α). CD38 knockout reduces fratricide and allows the expansion of CAR-T cells. Meanwhile, CD38KO/KI EF1α results in higher CAR expression than CD38KO/KI in both CAR-T and CAR-NK cells. In a mouse T-ALL model, CD38KO/KI EF1α CAR-T cells eradicate tumors better than CD38KO/KI CAR-T cells. Surprisingly, CD38KO/KI CAR-NK cells show superior tumor control than CD38KO/KI EF1α CAR-NK cells. Further investigation reveals that endogenous regulatory elements in NK cells lead to higher expression of CD38 CAR than in T cells, and the expression levels of CAR affect the therapeutic outcome of CAR-T and CAR-NK cells differently. Therefore, these results support the efficacy of CD38 CAR-T/NK against T-ALL and demonstrate that the "2-in-1" strategy can resolve fratricide and enhance tumor eradication, paving the way for clinical translation.

Immunotherapy in Acute Leukemias: Past Success Paves the Way for Future Progress

Immunotherapy as a cancer treatment modality has undergone recent widespread proliferation across all cancer types, especially amongst patients with solid tumors. However, the longest tenured immunotherapy approach to cancer is allogeneic stem cell transplantation (allo-SCT) for two hematologic malignancies: acute myeloid and acute lymphoid leukemia (AML and ALL, respectively). While allo-SCT remains a standard of care for eligible patients, recent advances/applications of monoclonal antibodies, immune checkpoint inhibitors, bispecific T-cell engagers (BiTEs), and CAR T-cell therapy are changing the treatment landscape for these acute leukemias by either direct to tumor immune targeting or through decreased toxicities that expand patient eligibility. Pre-clinical data and clinical trials have shown promising results for novel immunotherapies in acute leukemia, and multiple ongoing trials are investigating these novel approaches. While there have been promising results with these approaches, particularly in the relapsed/refractory setting, there remain challenges in optimizing the use of these therapies, such as managing cytokine release syndrome and other immune-related toxicities. Immunotherapy is a rapidly evolving field in the treatment of acute leukemia and has the potential to significantly impact the management of both AML and ALL. This review highlights the history of immunotherapy in the treatment of acute leukemias, the evolution of immunotherapy into more targeted approaches, the potential benefits and limitations of different immune targeting approaches, and ongoing research and development in the field.

Prognostic Immune Effector Signature in Adult Acute Lymphoblastic Leukemia Patients Is Dominated by γδ T Cells

The success of immunotherapy has highlighted the critical role of the immune microenvironment in acute lymphoblastic leukemia (ALL); however, the immune landscape in ALL remains incompletely understood and most studies have focused on conventional T cells or NK cells. This study investigated the prognostic impact of circulating γδ T-cell alterations using high-dimensional analysis in a cohort of newly diagnosed adult ALL patients (10 B-ALL; 9 Philadelphia+ ALL; 9 T-ALL). Our analysis revealed common alterations in CD8+ T cells and γδ T cells of relapsed patients, including accumulation of early stage differentiation and increased expression of BTLA and CD73. We demonstrated that the circulating γδ T-cell signature was the most discriminating between relapsed and disease-free groups. In addition, Vδ2 T-cell alterations strongly discriminated patients by relapse status. Taken together, these data highlight the role of ɣδ T cells in adult ALL patients, among whom Vδ2 T cells may be a pivotal contributor to T-cell immunity in ALL. Our findings provide a strong rationale for further monitoring and potentiating Vδ2 T cells in ALL, including in the autologous setting.

Galectin-9 and myeloid-derived suppressor cell as prognostic indicators for chronic lymphocytic leukemia

BACKGROUND

Galectin-9 and myeloid-derived suppressor cells (MDSCs) have an important role in tumors, but their clinical values in chronic lymphocytic leukemia (CLL) have not been fully elucidated. This study aimed to analyze the prognosis values of Galectin-9 and MDSCs in CLL.

METHODS

The concentrations of Galectin-9, argininase-1, and inducible nitric oxide synthase in serum were detected by enzyme-linked immune sorbent assay. The expression of Tim-3 protein in peripheral blood mononuclear cell was detected by Western blot. Flow cytometry was used to analyze the percentages of Tim-3 on T-cells (CD3⁺ T, CD4⁺ T, and CD8⁺ T cells) and MDSCs.

RESULTS

Our results showed that Galectin-9 and MDSCs significantly increased in CLL patients and were closely related to the disease progression. Patient's receiver operating characteristic, progression-free survival, and Cox regression analysis showed that Galectin9 and MDSCs were poor prognostic factors of CLL.

CONCLUSION

Galectin-9 and MDSCs were associated with clinical progression and could be important prognostic indicators for CLL.

Glycans as shapers of tumour microenvironment: A sweet driver of T-cell-mediated anti-tumour immune response

Essentially all cells are covered with a dense coat of different glycan structures/sugar chains, giving rise to the so-called glycocalyx. Changes in cellular glycosylation are a hallmark of cancer, affecting most of the pathophysiological processes associated with malignant transformation, including tumour immune responses. Glycans are chief macromolecules that define T-cell development, differentiation, fate, activation and signalling. Thus, the diversity of glycans expressed at the surface of T cells constitutes a fundamental molecular interface with the microenvironment by regulating the bilateral interactions between T-cells and cancer cells, fine-tuning the anti-tumour immune response. In this review, we will introduce the power of glycans as orchestrators of T-cell-mediated immune response in physiological conditions and in cancer. We discuss how glycans modulate the glyco-metabolic landscape in the tumour microenvironment, and whether glycans can synergize with immunotherapy as a way of rewiring T-cell effector functions against cancer cells.

B-cell acute lymphoblastic leukemia promotes an immune suppressive microenvironment that can be overcome by IL-12

Immunotherapies have revolutionized the treatment of B-cell acute lymphoblastic leukemia (B-ALL), but the duration of responses is still sub-optimal. We sought to identify mechanisms of immune suppression in B-ALL and strategies to overcome them. Plasma collected from children with B-ALL with measurable residual disease after induction chemotherapy showed differential cytokine expression, particularly IL-7, while single-cell RNA-sequencing revealed the expression of genes associated with immune exhaustion in immune cell subsets. We also found that the supernatant of leukemia cells suppressed T-cell function ex vivo. Modeling B-ALL in mice, we observed an altered tumor immune microenvironment, including compromised activation of T-cells and dendritic cells (DC). However, recombinant IL-12 (rIL-12) treatment of mice with B-ALL restored the levels of several pro-inflammatory cytokines and chemokines in the bone marrow and increased the number of splenic and bone marrow resident T-cells and DCs. RNA-sequencing of T-cells isolated from vehicle and rIL-12 treated mice with B-ALL revealed that the leukemia-induced increase in genes associated with exhaustion, including Lag3, Tigit, and Il10, was abrogated with rIL-12 treatment. In addition, the cytolytic capacity of T-cells co-cultured with B-ALL cells was enhanced when IL-12 and blinatumomab treatments were combined. Overall, these results demonstrate that the leukemia immune suppressive microenvironment can be restored with rIL-12 treatment which has direct therapeutic implications.

Immunotherapy for Pediatric Acute Lymphoblastic Leukemia: Recent Advances and Future Perspectives

Pediatric acute lymphoblastic leukemia (ALL) is the most common subtype of childhood leukemia, which is characterized by the abnormal proliferation and accumulation of immature lymphoid cell in the bone marrow. Although the long-term survival rate for pediatric ALL has made significant progress over years with the development of contemporary therapeutic regimens, patients are still suffered from relapse, leading to an unsatisfactory outcome. Since the immune system played an important role in the progression and relapse of ALL, immunotherapy including bispecific T-cell engagers and chimeric antigen receptor T cells has been demonstrated to be capable of enhancing the immune response in pediatric patients with refractory or relapsed B-cell ALL, and improving the cure rate of the disease and patients’ quality of life, thus receiving the authorization for market. Nevertheless, the resistance and toxicities associated with the current immunotherapy remains a huge challenge. Novel therapeutic options to overcome the above disadvantages should be further explored. In this review, we will thoroughly discuss the emerging immunotherapeutics for the treatment of pediatric ALL, as well as side-effects and new development.

Design and Evaluation of TIM-3-CD28 Checkpoint Fusion Proteins to Improve Anti-CD19 CAR T-Cell Function

Therapeutic targeting of inhibitory checkpoint molecules in combination with chimeric antigen receptor (CAR) T cells is currently investigated in a variety of clinical studies for treatment of hematologic and solid malignancies. However, the impact of co-inhibitory axes and their therapeutic implication remains understudied for the majority of acute leukemias due to their low immunogenicity/mutational load. The inhibitory exhaustion molecule TIM-3 is an important marker for the interaction of T cells with leukemic cells. Moreover, inhibitory signals from malignant cells could be transformed into stimulatory signals by synthetic fusion molecules with extracellular inhibitory receptors fused to an intracellular stimulatory domain. Here, we designed a variety of different TIM-3-CD28 fusion proteins to turn inhibitory signals derived by TIM-3 engagement into T-cell activation through CD28. In the absence of anti-CD19 CAR, two TIM-3-CD28 fusion receptors with large parts of CD28 showed strongest responses in terms of cytokine secretion and proliferation upon stimulation with anti-CD3 antibodies compared to controls. We then combined these two novel TIM-3-CD28 fusion proteins with first- and second-generation anti-CD19 CAR T cells and found that the fusion receptor can increase proliferation, activation, and cytotoxic capacity of conventional anti-CD19 CAR T cells. These additionally armed CAR T cells showed excellent effector function. In terms of safety considerations, the fusion receptors showed exclusively increased cytokine release, when the CAR target CD19 was present. We conclude that combining checkpoint fusion proteins with anti-CD19 CARs has the potential to increase T-cell proliferation capacity with the intention to overcome inhibitory signals during the response against malignant cells.

TIM-3 Expression Level on AML Blasts Correlates With Presence of Core Binding Factor Translocations Rather Than Clinical Outcomes

Background

T-cell immunoglobulin and mucin domain-containing molecule 3 (TIM-3) expresses on leukemic stem and progenitor populations of non-M3 acute myeloid leukemia (AML) as well as T lymphocytes. TIM-3 is thought to be involved in the self-renewal of leukemic stem cells and the immune escape of AML cells, however its correlation with AML prognosis is still controversial and worthy of further investigation.

Methods

we simultaneously assessed TIM-3 expression levels of leukemic blasts and T lymphocytes in the bone marrow of de novo AML patients using flow cytometry. The correlations of TIM-3 expression between leukemic blasts and T lymphocytes and the correlations of TIM-3 expression with various patient parameters were analyzed. In addition, the Cancer Genome Atlas (TCGA) data of AML patients were acquired and analyzed to verify the results.

Results

TIM-3 expression of CD34⁺ leukemic blasts (R² = 0.95, p<0.0001) and CD34⁺CD38^- leukemic stem cells (R² = 0.75, p<0.0001) were significantly and positively correlated with that of the whole population of leukemic blasts. In addition, TIM-3 expression level of leukemic blasts correlated significantly and positively with that of CD8⁺ (R² = 0.44, p<0.0001) and CD4⁺ (R² = 0.16, p=0.0181) lymphocytes, and higher TIM-3 expression of leukemic blasts was significantly associated with a greater proportion of peripheral CD8⁺ T lymphocytes (R² = 0.24, p=0.0092), indicating that TIM-3 on leukemic blasts might alter adaptive immunity of AML patients. Regarding clinical data, the presence of core binding factor (CBF) translocations was significantly correlated with higher TIM-3 expression of leukemic blasts (CBF versus non-CBF, median 22.78% versus 1.28%, p=0.0012), while TIM-3 expression levels of leukemic blasts were not significantly associated with the remission status after induction chemotherapy (p=0.9799), overall survival (p=0.4201) or event-free survival (p=0.9873). Similar to our results, TCGA data showed that patients with CBF translocations had significantly higher mRNA expression level of HAVCR2 (the gene encoding TIM-3) (median, 9.81 versus 8.69, p<0.0001), and as all patients in the cohort were divided into two groups based on the median HAVCR2 expression level, 5-year overall survivals were not significantly different (low versus high, 24.95% versus 24.54%, p=0.6660).

Conclusion

TIM-3 expression level on AML blasts correlates with presence of CBF translocations rather than clinical outcomes.

Integrative multi-omics and drug response profiling of childhood acute lymphoblastic leukemia cell lines

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Although standard-of-care chemotherapeutics are sufficient for most ALL cases, there are subsets of patients with poor response who relapse in disease. The biology underlying differences between subtypes and their response to therapy has only partially been explained by genetic and transcriptomic profiling. Here, we perform comprehensive multi-omic analyses of 49 readily available childhood ALL cell lines, using proteomics, transcriptomics, and pharmacoproteomic characterization. We connect the molecular phenotypes with drug responses to 528 oncology drugs, identifying drug correlations as well as lineage-dependent correlations. We also identify the diacylglycerol-analog bryostatin-1 as a therapeutic candidate in the MEF2D-HNRNPUL1 fusion high-risk subtype, for which this drug activates pro-apoptotic ERK signaling associated with molecular mediators of pre-B cell negative selection. Our data is the foundation for the interactive online Functional Omics Resource of ALL (FORALL) with navigable proteomics, transcriptomics, and drug sensitivity profiles at https://proteomics.se/forall.

Childhood acute lymphoblastic leukemia is characterised by a range of genetic aberrations. Here, the authors use multi-omics profiling of ALL cell lines to connect molecular phenotypes and drug responses to provide an interactive resource of drug sensitivity.

Antibiotics in early life and childhood pre-B-ALL. Reasons to analyze a possible new piece in the puzzle

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer with precursor B-cell ALL (pB-ALL) accounting for ~ 85% of the cases. Childhood pB-ALL development is influenced by genetic susceptibility and host immune responses. The role of the intestinal microbiome in leukemogenesis is gaining increasing attention since Vicente-Dueñas' seminal work demonstrated that the gut microbiome is distinct in mice genetically predisposed to ALL and that the alteration of this microbiome by antibiotics is able to trigger pB-ALL in Pax5 heterozygous mice in the absence of infectious stimuli. In this review we provide an overview on novel insights on the role of the microbiome in normal and preleukemic hematopoiesis, inflammation, the effect of dysbiosis on hematopoietic stem cells and the emerging importance of the innate immune responses in the conversion from preleukemic to leukemic state in childhood ALL. Since antibiotics, which represent one of the most widely used medical interventions, alter the gut microbial composition and can cause a state of dysbiosis, this raises exciting epidemiological questions regarding the implications for antibiotic use in early life, especially in infants with a a preleukemic "first hit". Sheading light through a rigorous study on this piece of the puzzle may have broad implications for clinical practice.

CD4 T-Cell Exhaustion: Does It Exist and What Are Its Roles in Cancer?

In chronic infections and in cancer, persistent antigen stimulation under suboptimal conditions can lead to the induction of T-cell exhaustion. Exhausted T cells are characterized by an increased expression of inhibitory markers and a progressive and hierarchical loss of function. Although cancer-induced exhaustion in CD8 T cells has been well-characterized and identified as a therapeutic target (i.e., via checkpoint inhibition), in-depth analyses of exhaustion in other immune cell types, including CD4 T cells, is wanting. While perhaps attributable to the contextual discovery of exhaustion amidst chronic viral infection, the lack of thorough inquiry into CD4 T-cell exhaustion is particularly surprising given their important role in orchestrating immune responses through T-helper and direct cytotoxic functions. Current work suggests that CD4 T-cell exhaustion may indeed be prevalent, and as CD4 T cells have been implicated in various disease pathologies, such exhaustion is likely to be clinically relevant. Defining phenotypic exhaustion in the various CD4 T-cell subsets and how it influences immune responses and disease severity will be crucial to understanding collective immune dysfunction in a variety of pathologies. In this review, we will discuss mechanistic and clinical evidence for CD4 T-cell exhaustion in cancer. Further insight into the derivation and manifestation of exhaustive processes in CD4 T cells could reveal novel therapeutic targets to abrogate CD4 T-cell exhaustion in cancer and induce a robust antitumor immune response.

Alteration of the immune environment in bone marrow from children with recurrent B cell precursor acute lymphoblastic leukemia

Due to the considerable success of cancer immunotherapy for leukemia, the tumor immune environment has become a focus of intense research; however, there are few reports on the dynamics of the tumor immune environment in leukemia. Here, we analyzed the tumor immune environment in pediatric B cell precursor acute lymphoblastic leukemia by analyzing serial bone marrow samples from nine patients with primary and recurrent disease by mass cytometry using 39 immunophenotype markers, and transcriptome analysis. High‐dimensional single‐cell mass cytometry analysis elucidated a dynamic shift of T cells from naïve to effector subsets, and clarified that, during relapse, the tumor immune environment comprised a T helper 1‐polarized immune profile, together with an increased number of effector regulatory T cells. These results were confirmed in a validation cohort using conventional flow cytometry. Furthermore, RNA transcriptome analysis identified the upregulation of immune‐related pathways in B cell precursor acute lymphoblastic leukemia cells during relapse, suggesting interaction with the surrounding environment. In conclusion, a tumor immune environment characterized by a T helper 1‐polarized immune profile, with an increased number of effector regulatory T cells, could contribute to the pathophysiology of recurrent B cell precursor acute lymphoblastic leukemia. This information could contribute to the development of effective immunotherapeutic approaches against B cell precursor acute lymphoblastic leukemia relapse.

TIM-3 in Leukemia; Immune Response and Beyond

T cell immunoglobulin and mucin domain 3 (TIM-3) expression on malignant cells has been reported in some leukemias. In myelodysplastic syndrome (MDS), increased TIM-3 expression on TH1 cells, regulatory T cells, CD8+ T cells, and hematopoietic stem cells (HSCs), which play a role in the proliferation of blasts and induction of immune escape, has been reported. In AML, several studies have reported overexpression of TIM-3 on leukemia stem cells (LSCs) but not on healthy HSCs. Overexpression of TIM-3 on exhausted CD4+ and CD8+ T cells and leukemic cells in CML, ALL, and CLL patients could be a prognostic risk factor for poor therapeutic response and relapse in patients. Currently, several TIM-3 inhibitors are used in clinical trials for leukemias, and some have shown encouraging response rates for MDS and AML treatment. For AML immunotherapy, blockade TIM-3 may have dual effects: directly inhibiting AML cell proliferation and restoring T cell function. However, blockade of PD-1 and TIM-3 fails to restore the function of exhausted CD8+ T cells in the early clinical stages of CLL, indicating that the effects of TIM-3 blockade may be different in AML and other leukemias. Thus, further studies are required to evaluate the efficacy of TIM-3 inhibitors in different types and stages of leukemia. In this review, we summarize the biological functions of TIM-3 and its contribution as it relates to leukemias. We also discuss the effects of TIM-3 blockade in hematological malignancies and clinical trials of TIM-3 for leukemia therapy.

Safety and Efficacy of Immune Checkpoint Inhibitors in Children and Young Adults with Haematological Malignancies: Review and Future Perspectives

Despite the marked improvement in overall survival rates of paediatric patients with haematological malignancies that has been achieved during the last decades, there is still a pressing need for novel therapeutic approaches for the subset of patients with relapsed or refractory disease. Immune checkpoint inhibitors aim to induce potent anti-tumour immune responses by targeted blockade of inhibitory receptors and have shown great promise in preclinical models and studies in the adult population. However, paediatric malignancies present unique features and so far, experience with these agents remains limited. In the current review we present an overview of efficacy and safety data from case reports, case series and clinical trials employing the use of immune checkpoint inhibitors in children, adolescents and young adults with haematological malignancies. We also discuss new possibilities involving novel targets and combination treatments and provide a summary of the currently registered clinical trials.

Mechanisms of Immune Evasion in Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) results from a clonal expansion of abnormal lymphoid progenitors of B cell (BCP-ALL) or T cell (T-ALL) origin that invade bone marrow, peripheral blood, and extramedullary sites. Leukemic cells, apart from their oncogene-driven ability to proliferate and avoid differentiation, also change the phenotype and function of innate and adaptive immune cells, leading to escape from the immune surveillance. In this review, we provide an overview of the genetic heterogeneity and treatment of BCP- and T-ALL. We outline the interactions of leukemic cells in the bone marrow microenvironment, mainly with mesenchymal stem cells and immune cells. We describe the mechanisms by which ALL cells escape from immune recognition and elimination by the immune system. We focus on the alterations in ALL cells, such as overexpression of ligands for various inhibitory receptors, including anti-phagocytic receptors on macrophages, NK cell inhibitory receptors, as well as T cell immune checkpoints. In addition, we describe how developing leukemia shapes the bone marrow microenvironment and alters the function of immune cells. Finally, we emphasize that an immunosuppressive microenvironment can reduce the efficacy of chemo- and immunotherapy and provide examples of preclinical studies showing strategies for improving ALL treatment by targeting these immunosuppressive interactions.

T Cell Exhaustion and CAR-T Immunotherapy in Hematological Malignancies

T cell exhaustion has been recognized to play an immunosuppressive role in malignant diseases. Persistent tumor antigen stimulation, the presence of inhibitory immune cells and cytokines in tumor microenvironment (TME), upregulated expression of inhibitory receptors, changes in T cell-related transcription factors, and metabolic factors can all result in T cell exhaustion. Strategies dedicated to preventing or reversing T cell exhaustion are required to reduce the morbidity from cancer and enhance the effectiveness of adoptive cellular immunotherapy. Here, we summarize the current findings of T cell exhaustion in hematological malignancies and chimeric antigen receptor T (CAR-T) immunotherapy, as well as the value of novel technologies, to inverse such dysfunction. Our emerging understanding of T cell exhaustion may be utilized to develop personalized strategies to restore antitumor immunity.

TIM-3 pathway dysregulation and targeting in cancer

INTRODUCTION

Dysfunction of the immune system is a hallmark of cancer. Through increased understanding of the complex interactions between immunity and cancer, immunotherapy has emerged as a treatment modality for different types of cancer. Promising activity with immunotherapy has been reported in numerous malignancies, but challenges such as limited response rates and treatment resistance remain. Furthermore, outcomes with this therapeutic approach in hematologic malignancies are even more limited than in solid tumors. T-cell immunoglobulin domain and mucin domain 3 (TIM-3) has emerged as a potential immune checkpoint target in both solid tumors and hematologic malignancies. TIM-3 has been shown to promote immune tolerance, and overexpression of TIM-3 is associated with more aggressive or advanced disease and poor prognosis.

AREAS COVERED

This review examines what is currently known regarding the biology of TIM-3 and clinical implications of targeting TIM-3 in cancer. Particular focus is given to myeloid malignancies.

EXPERT OPINION

The targeting of TIM-3 is a promising therapeutic approach in cancers, including hematologic cancers such as myeloid malignancies which have not benefited much from current immunotherapeutic treatment approaches. We anticipate that with further clinical evaluation, TIM-3 blockade will emerge as an important treatment strategy in myeloid malignancies.

Hematopoietic versus Solid Cancers and T Cell Dysfunction: Looking for Similarities and Distinctions

Simple Summary

Dysfunction of the immune T cell compartment occurs in many hematopoietic as well as solid cancers and hampers successful application of new immunotherapeutic approaches. A complete understanding of T cell dysfunction might improve the outcome of such therapies, but an overview in the various cancers is still lacking. We aim to map areas of similarities and differences in solid versus hematopoietic malignancies, providing a high-level rather than a detailed perspective on T cell dysfunction in those tumors.

Abstract

Cancer cells escape, suppress and exploit the host immune system to sustain themselves, and the tumor microenvironment (TME) actively dampens T cell function by various mechanisms. Over the last years, new immunotherapeutic approaches, such as adoptive chimeric antigen receptor (CAR) T cell therapy and immune checkpoint inhibitors, have been successfully applied for refractory malignancies that could only be treated in a palliative manner previously. Engaging the anti-tumor activity of the immune system, including CAR T cell therapy to target the CD19 B cell antigen, proved to be effective in acute lymphocytic leukemia. In low-grade hematopoietic B cell malignancies, such as chronic lymphocytic leukemia, clinical outcomes have been tempered by cancer-induced T cell dysfunction characterized in part by a state of metabolic lethargy. In multiple myeloma, novel antigens such as BCMA and CD38 are being explored for CAR T cells. In solid cancers, T cell-based immunotherapies have been applied successfully to melanoma and lung cancers, whereas application in e.g., breast cancer lags behind and is modestly effective as yet. The main hurdles for CAR T cell immunotherapy in solid tumors are the lack of suitable antigens, anatomical inaccessibility, and T cell anergy due to immunosuppressive TME. Given the wide range of success and failure of immunotherapies in various cancer types, it is crucial to comprehend the underlying similarities and distinctions in T cell dysfunction. Hence, this review aims at comparing selected, distinct B cell-derived versus solid cancer types and at describing means by which malignant cells and TME might dampen T cell anti-tumor activity, with special focus on immunometabolism. Drawing a meaningful parallel between the efficacy of immunotherapy and the extent of T cell dysfunction will shed light on areas where we can improve immune function to battle cancer.

Leukemia escape in immune desert: intraocular relapse of pediatric pro-B-ALL during systemic control by CD19-CAR T cells

Background

Relapsed/refractory B-precursor acute lymphoblastic leukemia (BCP-ALL) remains a major therapeutic challenge in pediatric hematology. Chimeric antigen receptor (CAR) T cells targeting CD19 have shown remarkable initial response rates in BCP-ALL patients, while long-term leukemia control rate is only about 50%. So far, main mechanisms of BCP-ALL relapse after CD19-CAR T-cell therapy have been either insufficient CAR T-cell persistence in vivo or loss of surface CD19.

Case Report

Here, we report an exceptional presentation of BCP-ALL relapse in the eye during the systemic control through CAR T-cell therapy. We report a case of fatal intraocular relapse in a pediatric patient with pro-B-ALL after initial response to CD19-CAR T-cell therapy. One month after CD19-CAR T-cell therapy, remission was documented by bone marrow aspirate analysis with absence of CD19⁺ cells and CD19-CAR T cells could be detected in both peripheral blood and bone marrow. At the same time, however, the patient presented with progressive visual disturbance and CD19⁺ cells were found within the anterior chamber of the eye. Despite local and systemic therapy, ocular relapse led to BCP-ALL dissemination and systemic relapse within weeks. The eye represents a rare site for local manifestation of BCP-ALL, but isolated intraocular relapse is a clinically unreckoned presentation of BCP-ALL in the era of CD19-CAR T cells.

Conclusion

During systemic control of BCP-ALL through CD19-CAR T cells, relapse can emerge in the eye as an immune-privileged organ. Ocular symptoms after CD19-CAR T-cell therapy should guide the clinician to elucidate the etiology in a timely fashion in order to adjust leukemia treatment strategy. Both, local immune escape as well as insufficient CAR T-cell persistence may have contributed to relapse in the reported patient. Mechanisms of relapse in an immune desert under CAR T-cell therapy require future clinical and experimental attention. In particular, ocular symptoms after CAR T-cell therapy should be considered a potentially early sign of leukemia relapse.

CRISPR-Cas, a robust gene-editing technology in the era of modern cancer immunotherapy

Cancer immunotherapy has been emerged as a promising strategy for treatment of a broad spectrum of malignancies ranging from hematological to solid tumors. One of the principal approaches of cancer immunotherapy is transfer of natural or engineered tumor-specific T-cells into patients, a so called "adoptive cell transfer", or ACT, process. Construction of allogeneic T-cells is dependent on the employment of a gene-editing tool to modify donor-extracted T-cells and prepare them to specifically act against tumor cells with enhanced function and durability and least side-effects. In this context, CRISPR technology can be used to produce universal T-cells, equipped with recombinant T cell receptor (TCR) or chimeric antigen receptor (CAR), through multiplex genome engineering using Cas nucleases. The robust potential of CRISPR-Cas in preparing the building blocks of ACT immunotherapy has broaden the application of such therapies and some of them have gotten FDA approvals. Here, we have collected the last investigations in the field of immuno-oncology conducted in partnership with CRISPR technology. In addition, studies that have addressed the challenges in the path of CRISPR-mediated cancer immunotherapy, as well as pre-treatment applications of CRISPR-Cas have been mentioned in detail.

The potentials of immune checkpoints for the treatment of blood malignancies

Immune checkpoints are the regulators of the immune system, which include stimulatory and inhibitory receptors. They play substantial roles in the maintenance of immune system homeostasis and the prevention of autoimmunity and cancer. In the current review, immune checkpoints roles are surveyed in the initiation, progression, and treatment of blood malignancies. The significant roles of immune checkpoints are discussed as clinical markers in the diagnosis and prognosis of a plethora of blood malignancies and also as potential targets for the treatment of these malignancies. It could be concluded that the regulation of immune checkpoints in various blood cancers can be employed as a novel strategy to obtain effective results in leukemia treatment and introduce immune checkpoint inhibitors as sufficient weapons against blood cancers in the future.