IL-7 and CCL19 expression in CAR-T cells improves immune cell infiltration and CAR-T cell survival in the tumor

The Role of IL-7 and IL-7R in Cancer Pathophysiology and Immunotherapy

Interleukin-7 (IL-7) is a multipotent cytokine that maintains the homeostasis of the immune system. IL-7 plays a vital role in T-cell development, proliferation, and differentiation, as well as in B cell maturation through the activation of the IL-7 receptor (IL-7R). IL-7 is closely associated with tumor development and has been used in cancer clinical research and therapy. In this review, we first summarize the roles of IL-7 and IL-7Rα and their downstream signaling pathways in immunity and cancer. Furthermore, we summarize and discuss the recent advances in the use of IL-7 and IL-7Rα as cancer immunotherapy tools and highlight their potential for therapeutic applications. This review will help in the development of cancer immunotherapy regimens based on IL-7 and IL-7Rα, and will also advance their exploitation as more effective and safe immunotherapy tools.

Targeting glycans for CAR therapy: The advent of sweet CARs

Chimeric antigen receptor (CAR) T cell therapy has created a paradigm shift in the treatment of hematologic malignancies but has not been as effective toward solid tumors. For such tumors, the primary obstacles facing CAR T cells are scarcity of tumor-specific antigens and the hostile and complex tumor microenvironment. Glycosylation, the process by which sugars are post-translationally added to proteins or lipids, is profoundly dysregulated in cancer. Abnormally glycosylated glycoproteins expressed on cancer cells offer unique targets for CAR T therapy as they are specific to tumor cells. Tumor stromal cells also express abnormal glycoproteins and thus also have the potential to be targeted by glycan-binding CAR T cells. This review will discuss the state of CAR T cells in the therapy of solid tumors, the cancer glycoproteome and its potential for use as a therapeutic target, and the landscape and future of glycan-binding CAR T cell therapy.

Paving the Way to Solid Tumors: Challenges and Strategies for Adoptively Transferred Transgenic T Cells in the Tumor Microenvironment

T cells are important players in the antitumor immune response. Over the past few years, the adoptive transfer of genetically modified, autologous T cells-specifically redirected toward the tumor by expressing either a T cell receptor (TCR) or a chimeric antigen receptor (CAR)-has been adopted for use in the clinic. At the moment, the therapeutic application of CD19- and, increasingly, BCMA-targeting-engineered CAR-T cells have been approved and have yielded partly impressive results in hematologic malignancies. However, employing transgenic T cells for the treatment of solid tumors remains more troublesome, and numerous hurdles within the highly immunosuppressive tumor microenvironment (TME) need to be overcome to achieve tumor control. In this review, we focused on the challenges that these therapies must face on three different levels: infiltrating the tumor, exerting efficient antitumor activity, and overcoming T cell exhaustion and dysfunction. We aimed to discuss different options to pave the way for potent transgenic T cell-mediated tumor rejection by engineering either the TME or the transgenic T cell itself, which responds to the environment.

Secretory co-factors in next-generation cellular therapies for cancer

Since chimeric antigen receptor (CAR) T-cell therapies for hematologic malignancies were approved by the U.S. Food and Drug Administration, numerous "next-generation" CAR T cells have been developed to improve their safety, efficacy, and applicability. Although some of these novel therapeutic strategies are promising, it remains difficult to apply these therapies to solid tumors and to control adverse effects, such as cytokine release syndrome and neurotoxicity. CAR T cells are generated using highly scalable genetic engineering techniques. One of the major strategies for producing next-generation CAR T cells involves the integration of useful co-factor(s) into the artificial genetic design of the CAR gene, resulting in next-generation CAR T cells that express both CAR and the co-factor(s). Many soluble co-factors have been reported for CAR T cells and their therapeutic effects and toxicity have been tested by systemic injection; therefore, CAR T cells harnessing secretory co-factors could be close to clinical application. Here, we review the various secretory co-factors that have been reported to improve the therapeutic efficacy of CAR T cells and ameliorate adverse events. In addition, we discuss the different co-factor expression systems that have been used to optimize their beneficial effects. Altogether, we demonstrate that combining CAR T cells with secretory co-factors will lead to next-generation CAR T-cell therapies that can be used against broader types of cancers and might provide advanced tools for more complicated synthetic immunotherapies.

Induced expression of CCL19 promotes the anti-tumor ability of CAR-T cells by increasing their infiltration ability

Background

Chimeric antigen receptor-engineered T cell (CAR-T) therapy has shown promising potential for anti-cancer treatment. However, for pancreatic ductal adenocarcinoma (PDAC), the lack of infiltrative ability of these CAR-T cells leads to sub-optimal treatment outcome.

Methods

Chemokine (C-C motif) ligand 19 (CCL19), the expression of which is regulated by the nuclear factor of activated T cell pathway, was transfected into targeting mesothelin CAR-T cells (mesoCAR-N19) using NFAT regulating element. It was expressed in activated CAR-T cells by OKT3 or mesothelin+ tumor cells but not in inactive cells. The migratory ability of these CAR-T cells was then measured. Subsequently, functional identification of these CAR-T cells was performed in vivo. In addition, the tumor lytic activity and proliferation of the CAR-T cells were measured in vitro. The degree of CAR-T cell infiltration and distribution into the PDAC tumors was examined using the immunohistochemical staining of hCD3 and the detection of CAR gene copy number by quantitative PCR. Finally, the functional assessment of chemokine (C-C motif) receptor 7 knock-out was performed in the CAR-T cells.

Results

Through in vitro Transwell assays, it was demonstrated that mesoCAR-N19 can be specifically expressed in CAR-T cells activated by tumor cells compared with conventional mesothelin CAR-T (mesoCAR) cells. We also observed that upregulating the expression of CCL19 can increase the recruitment of additional T cells. In vivo studies subsequently revealed that this highly specific recruitment of T cell infiltration is associated with enhanced tumor-suppressive activities downstream.

Conclusion

Induced expression of CCL19 can promote the anti-tumor ability of CAR-T cells by increasing their infiltrative ability. This study potentially uncovered novel method of activating CAR-T cells to enhance their infiltrative capacities, which offers a novel direction for PDAC treatment.

EZH1 repression generates mature iPSC-derived CAR T cells with enhanced antitumor activity

Human induced pluripotent stem cells (iPSCs) provide a potentially unlimited resource for cell therapies, but the derivation of mature cell types remains challenging. The histone methyltransferase EZH1 is a negative regulator of lymphoid potential during embryonic hematopoiesis. Here, we demonstrate that EZH1 repression facilitates in vitro differentiation and maturation of T cells from iPSCs. Coupling a stroma-free T cell differentiation system with EZH1-knockdown-mediated epigenetic reprogramming, we generated iPSC-derived T cells, termed EZ-T cells, which display a highly diverse T cell receptor (TCR) repertoire and mature molecular signatures similar to those of TCRαβ T cells from peripheral blood. Upon activation, EZ-T cells give rise to effector and memory T cell subsets. When transduced with chimeric antigen receptors (CARs), EZ-T cells exhibit potent antitumor activities in vitro and in xenograft models. Epigenetic remodeling via EZH1 repression allows efficient production of developmentally mature T cells from iPSCs for applications in adoptive cell therapy.

CAR-T Therapy in Clinical Practice: Technical Advances and Current Challenges

Chimeric antigen receptors (CAR) redirect T cells to specifically recognize and eliminate tumor cells. CAR-T therapy has achieved successful clinical outcomes, and it has been transformed into commercially available products to treat acute lymphoblastic leukemia and B cell lymphoma. These breakthroughs have motivated hundreds of CAR-T clinical trials initiated each year, with ≈900 cases registered on the ClinicalTrials website till 2021. Accumulating clinical experiences have highlighted some limitations of this strategy, e.g., relapse after complete response, poor efficacy in solid tumors, on-target off-tumor toxicities, lack of persistence, and tumor resistance. These challenges limit the therapeutic application of CAR-T cells. Multidisciplinary approaches are actively investigated to address these issues. In this review, the antigens, CAR designs, and cell sources are summarized in clinical trials from 2020 to 2021. The innovative modular and programmable designs in CAR-T cells, including advances in signaling domains, antigen-recognition domains, T cell engineering, and cell resources, are further discussed. Integrative genetic and chemical engineering strategies are promising to improve the versatility, antitumor efficacy, persistence, and safety of CAR-T cells. In the future, the next generation of CAR-T cell therapies will offer more options for patients who are refractory to standard tumor therapies.

Immunotherapy: Reshape the Tumor Immune Microenvironment

Tumor immune microenvironment (TIME) include tumor cells, immune cells, cytokines, etc. The interactions between these components, which are divided into anti-tumor and pro-tumor, determine the trend of anti-tumor immunity. Although the immune system can eliminate tumor through the cancer-immune cycle, tumors appear to eventually evade from immune surveillance by shaping an immunosuppressive microenvironment. Immunotherapy reshapes the TIME and restores the tumor killing ability of anti-tumor immune cells. Herein, we review the function of immune cells within the TIME and discuss the contribution of current mainstream immunotherapeutic approaches to remolding the TIME. Changes in the immune microenvironment in different forms under the intervention of immunotherapy can shed light on better combination treatment strategies.

The landscape of chimeric antigen receptor T cell therapy in breast cancer: Perspectives and outlook

Chimeric antigen receptor-T (CAR-T) cell therapy is a revolutionary adoptive cell therapy, which could modify and redirect T cells to specific tumor cells. Since CAR-T cell therapy was first approved for B cell-derived malignancies in 2017, it has yielded unprecedented progress in hematological tumors and has dramatically reshaped the landscape of cancer therapy in recent years. Currently, cumulative evidence has demonstrated that CAR-T cell therapy could be a viable therapeutic strategy for solid cancers. However, owing to the immunosuppressive tumor microenvironment (TME) and heterogenous tumor antigens, the application of CAR-T cell therapy against solid cancers requires circumventing more challenging obstacles. Breast cancer is characterized by a high degree of invasiveness, malignancy, and poor prognosis. The review highlights the underlying targets of CAR-T cell therapy in breast cancer, summarizes the challenges associated with CAR-T cell therapy, and proposes the strategies to overcome these challenges, which provides a novel approach to breast cancer treatment.

Revolution of CAR Engineering For Next-Generation Immunotherapy In Solid Tumors

Chimeric antigen receptor (CAR)-T cells have enormous potentials for clinical therapies. The CAR-T therapy has been approved for treating hematological malignancies. However, their application is limited in solid tumors owing to antigen loss and mutation, physical barriers, and an immunosuppressive tumor microenvironment. To overcome the challenges of CAR-T, increasing efforts are put into developing CAR-T to expand its applied ranges. Varied receptors are utilized for recognizing tumor-associated antigens and relieving immunosuppression. Emerging co-stimulatory signaling is employed for CAR-T activation. Furthermore, other immune cells such as NK cells and macrophages have manifested potential for delivering CAR. Hence, we collected and summarized the last advancements of CAR engineering from three aspects, namely, the ectodomains, endogenous domains, and immune cells, aiming to inspire the design of next-generation adoptive immunotherapy for treating solid tumors.

CD8+ T-cell responses are boosted by dual PD-1/VEGFR2 blockade after EGFR inhibition in Egfr-mutant lung cancer

Epidermal growth factor receptor (EGFR) is the most frequently mutated driver oncogene in non-smoking-related, non-small-cell lung cancer (NSCLC). EGFR-mutant NSCLC has a non-inflamed tumor microenvironment (TME), with low infiltration by CD8+ T cells and, thus, immune checkpoint inhibitors, such as anti-programmed cell death-1 (anti-PD-1) have weak anti-tumor effects. Here, we showed that CD8+ T-cell responses were induced by an EGFR-tyrosine kinase inhibitor (TKI) in syngeneic Egfr-mutant NSCLC tumors, which was further pronounced by sequential dual blockade of PD-1 and vascular endothelial growth factor receptor 2 (VEGFR2). However, simultaneous triple blockade had no such effect. PD-1/VEGFR2 dual blockade did not exert tumor-inhibitory effects without pre-treatment with the EGFR-TKI, suggesting that treatment schedule is crucial for efficacy of the dual blockade therapy. Pre-treatment with EGFR-TKI increased the CD8+ T-cell/regulatory T-cell (Treg) ratio, while also increasing expression of immunosuppressive chemokines and chemokine receptors, as well as increasing the number of M2-like macrophages, in the TME. Discontinuing EGFR-TKI treatment reversed the transient increase of immunosuppressive factors in the TME. The subsequent PD-1/VEGFR2 inhibition maintained increased numbers of infiltrating CD8+ T cells and CD11c+ dendritic cells. Depletion of CD8+ T cells in vivo abolished tumor growth inhibition by EGFR-TKI alone and the sequential triple therapy, suggesting that EGFR inhibition is a prerequisite for the induction of CD8+ T-cell responses. Our findings could aid in developing an alternative immunotherapy strategy in patients with cancers that have driver mutations and a non-inflamed TME.

Challenges in the Treatment of Glioblastoma by Chimeric Antigen Receptor T-Cell Immunotherapy and Possible Solutions

Glioblastoma (GBM), one of the most lethal brain cancers in adults, accounts for 48.6% of all malignant primary CNS tumors diagnosed each year. The 5-year survival rate of GBM patients remains less than 10% even after they receive the standard-of-care treatment, including maximal safe resection, adjuvant radiation, and chemotherapy with temozolomide. Therefore, new therapeutic modalities are urgently needed for this deadly cancer. The last decade has witnessed great advances in chimeric antigen receptor T (CAR-T) cell immunotherapy for the treatment of hematological malignancies. Up to now, the US FDA has approved six CAR-T cell products in treating hematopoietic cancers including B-cell acute lymphoblastic leukemia, lymphoma, and multiple myeloma. Meanwhile, the number of clinical trials on CAR-T cell has increased significantly, with more than 80% from China and the United States. With its achievements in liquid cancers, the clinical efficacy of CAR-T cell therapy has also been explored in a variety of solid malignancies that include GBMs. However, attempts to expand CAR-T cell immunotherapy in GBMs have not yet presented promising results in hematopoietic malignancies. Like other solid tumors, CAR-T cell therapies against GBM still face several challenges, such as tumor heterogeneity, tumor immunosuppressive microenvironment, and CAR-T cell persistence. Hence, developing strategies to overcome these challenges will be necessary to accelerate the transition of CAR-T cell immunotherapy against GBMs from bench to bedside.

Development of Molecular Mechanisms and Their Application on Oncolytic Newcastle Disease Virus in Cancer Therapy

Cancer is caused by the destruction or mutation of cellular genetic materials induced by environmental or genetic factors. It is defined by uncontrolled cell proliferation and abnormality of the apoptotic pathways. The majority of human malignancies are characterized by distant metastasis and dissemination. Currently, the most common means of cancer treatment include surgery, radiotherapy, and chemotherapy, which usually damage healthy cells and cause toxicity in patients. Targeted therapy is an effective tumor treatment method with few side effects. At present, some targeted therapeutic drugs have achieved encouraging results in clinical studies, but finding an effective solution to improve the targeting and delivery efficiency of these drugs remains a challenge. In recent years, oncolytic viruses (OVs) have been used to direct the tumor-targeted therapy or immunotherapy. Newcastle disease virus (NDV) is a solid oncolytic agent capable of directly killing tumor cells and increasing tumor antigen exposure. Simultaneously, NDV can trigger the proliferation of tumor-specific immune cells and thus improve the therapeutic efficacy of NDV in cancer. Based on NDV’s inherent oncolytic activity and the stimulation of antitumor immune responses, the combination of NDV and other tumor therapy approaches can improve the antitumor efficacy while reducing drug toxicity, indicating a broad application potential. We discussed the biological properties of NDV, the antitumor molecular mechanisms of oncolytic NDV, and its application in the field of tumor therapy in this review. Furthermore, we presented new insights into the challenges that NDV will confront and suggestions for increasing NDV’s therapeutic efficacy in cancer.

CAR-T Cells in the Treatment of Urologic Neoplasms: Present and Future

In recent years, with the breakthrough of CAR-T cells in the treatment of hematological tumors, they are increasingly being used to treat solid tumors, including urologic neoplasms. There are many relatively specific targets for urologic neoplasms, especially prostate cancer. Besides, urologic neoplasms tend to progress more slowly than tumors in other organs of the body, providing ample time for CAR-T cell application. Therefore, CAR-T cells technology has inherent advantages in urologic neoplasms. CAR-T cells in the treatment of urologic neoplasms have been extensively studied and preliminary achievements have been made. However, no breakthrough has been made due to the problems of targeting extra-tumor cytotoxicity and poor anti-tumor activity. we systematacially summarized the research actuality of CAR-T cells in urologic neoplasms, discussed the potential value and difficulties of the research. The application of CAR-T cells in the treatment of urologic neoplasms requires improvement of function through screening for better targets, modification of CAR structures, or in combination with other antitumor approaches.

Anti-HER2 scFv-CCL19-IL7 recombinant protein inhibited gastric tumor growth in vivo

HER-2 targeted therapies, such as monoclonal antibodies (mAbs) and CAR-T cell therapy have been applied in the treatment of various of cancers. However, the anti-HER2 CAR-T cell therapy are limited by its expensive production procedure and fatal side effects such as cytokine storm or “On target, off tumor”. The application of anti-HER2 mAbs to the soild tumor are also plagued by the patients resistant with different mechanisms. Thus, the recombinant protein technology can be presented as an attractive methods in advantage its less toxic and lower cost. In this study, we produced a HER-2-targeting recombinant protein, which is the fusion of the anti-HER-2 single chain fragment variable domain, CCL19 and IL7 (HCI fusion protein). Our results showed that the recombinant protein can induce the specific lysis effects of immune cells on HER-2-positive gastric tumor cells and can suppress gastric tumor growth in a xenograft model by chemotactic autoimmune cell infiltration into tumor tissues and activated T cells. Taken together, our results revealed that the HCI fusion protein can be applied as a subsequent clinical drug in treating HER-2 positive gastric tumors.

CAR T Cell Locomotion in Solid Tumor Microenvironment

The promising outcomes of chimeric antigen receptor (CAR) T cell therapy in hematologic malignancies potentiates its capability in the fight against many cancers. Nevertheless, this immunotherapy modality needs significant improvements for the treatment of solid tumors. Researchers have incrementally identified limitations and constantly pursued better CAR designs. However, even if CAR T cells are armed with optimal killer functions, they must overcome and survive suppressive barriers imposed by the tumor microenvironment (TME). In this review, we will discuss in detail the important role of TME in CAR T cell trafficking and how the intrinsic barriers contribute to an immunosuppressive phenotype and cancer progression. It is of critical importance that preclinical models can closely recapitulate the in vivo TME to better predict CAR T activity. Animal models have contributed immensely to our understanding of human diseases, but the intensive care for the animals and unreliable representation of human biology suggest in vivo models cannot be the sole approach to CAR T cell therapy. On the other hand, in vitro models for CAR T cytotoxic assessment offer valuable insights to mechanistic studies at the single cell level, but they often lack in vivo complexities, inter-individual heterogeneity, or physiologically relevant spatial dimension. Understanding the advantages and limitations of preclinical models and their applications would enable more reliable prediction of better clinical outcomes.

Identification of Immune-Related Gene Signature in Stanford Type A Aortic Dissection

Background: Stanford type A aortic dissection (ATAAD) is a common life-threatening event in the aorta. Recently, immune disorder has been linked to the risk factors that cause ATAAD at the molecular level. However, the specific immune-related gene signature during the progression is unclear.

Methods: The GSE52093 and GSE98770 datasets related to ATAAD from the Gene Expression Omnibus (GEO) database were acquired. The immune gene expression levels were analyzed by single sample gene set enrichment analysis (ssGSEA). The correlations between gene networks and immune scores were determined by weighted gene correlation network analysis (WGCNA). The different immune subgroups were finally divided by consensus clustering. The differentially expressed genes (DEGs) were identified and subsequent functional enrichment analyses were conducted. The hub genes were identified by protein–protein interaction (PPI) network and functional similarities analyses. The immune cell infiltration proportion was determined by the CIBERSORT algorithm.

Results: According to the ssGSEA results, the 13 ATAAD samples from the GEO database were divided into high- and low-immune subgroups according to the ssGSEA, WGCNA, and consensus clustering analysis results. Sixty-eight immune-related DEGs (IRDEGs) between the two subgroups were enriched in inflammatory-immune response biological processes, including leukocyte cell–cell adhesion, mononuclear cell migration, and myeloid leukocyte migration. Among these IRDEGs, 8 genes (CXCR4, LYN, CCL19, CCL3L3, SELL, F11R, DPP4, and VAV3) were identified as hub genes that represented immune-related signatures in ATAAD after the PPI and functional similarities analyses. The proportions of infiltrating CD8 T cells and M1 macrophages were significantly higher in ATAAD patients in the immune-high group than the immune-low group.

Conclusion: Eight immune-related genes were identified as hub genes representing potential biomarkers and therapeutic targets linked to the immune response in ATAAD patients.

CAR T cell therapy and the tumor microenvironment: Current challenges and opportunities

Chimeric antigen receptor (CAR) T cell therapy has demonstrated remarkable outcomes in individuals with hematological malignancies, but its success has been hindered by barriers intrinsic to the tumor microenvironment (TME), particularly for solid tumors, where it has yet to make its mark. In this article, we provide an updated review and future perspectives on features of the TME that represent barriers to CART cell therapy efficacy, including competition for metabolic fuels, physical barriers to infiltration, and immunosuppressive factors. We then discuss novel and promising strategies to overcome these obstacles that are in preclinical development or under clinical investigation.

Chimeric anti-GPC3 sFv-CD3ε receptor-modified T cells with IL7 co-expression for the treatment of solid tumors

Chimeric antigen receptor (CAR) T cells targeting glypican-3 (GPC3) demonstrated early signs of therapeutic efficacy to hepatocellular carcinoma patients with a risk of cytokine release syndrome (CRS). Several adoptive cell therapies (ACTs) with T cells using the natural T cell receptor (TCR) signaling induced more efficient antitumor function and reduced cytokine production relative to CARs in solid tumors. To improve the efficacy and safety of GPC3-targeted ACTs, T cells were modified with anti-GPC3 single-chain fragment variable(sFv) linked to CD3ε, which could be incorporated into the entire TCR/CD3 complex to form chimeric sFv-CD3ε receptor (sFv-ε). sFv-ε T cells showed competitive antitumor activity and lower cytokine release compared to 28ζ or BBζ CAR T cells, which may be ascribed to moderately less activated Ca²⁺-calcineurin-NFAT signaling pathway. We further generated murine sFv-ε T cells with interleukin-7 co-expression (7sFv-ε) to promote T cell survival and to mobilize the endogenous immune system. In immunocompetent mouse models, 7sFv-ε T cells showed superior persistence, antitumor efficacy, and immunological memory while preserving the low production of cytokines associated with CRS compared to conventional sFv-ε T cells. These results indicate that GPC3-specific 7sFv-ε T cells could serve as a promising therapeutic strategy for solid tumors.

A long-acting interleukin-7, rhIL-7-hyFc, enhances CAR T cell expansion, persistence, and anti-tumor activity

Chimeric antigen receptor (CAR) T cell therapy is routinely used to treat patients with refractory hematologic malignancies. However, a significant proportion of patients experience suboptimal CAR T cell cytotoxicity and persistence that can permit tumor cell escape and disease relapse. Here we show that a prototype pro-lymphoid growth factor is able to enhance CAR T cell efficacy. We demonstrate that a long-acting form of recombinant human interleukin-7 (IL-7) fused with hybrid Fc (rhIL-7-hyFc) promotes proliferation, persistence and cytotoxicity of human CAR T cells in xenogeneic mouse models, and murine CAR T cells in syngeneic mouse models, resulting in long-term tumor-free survival. Thus, rhIL-7-hyFc represents a tunable clinic-ready adjuvant for improving suboptimal CAR T cell activity.

Engineering Next-Generation CAR-T Cells: Overcoming Tumor Hypoxia and Metabolism

T cells engineered to express chimeric antigen receptors (CARs) have shown remarkable success in treating B-cell malignancies, reflected by multiple US Food and Drug Administration-approved CAR-T cell products currently on the market. However, various obstacles have thus far limited the use of approved products and constrained the efficacy of CAR-T cell therapy against solid tumors. Overcoming these obstacles will necessitate multidimensional CAR-T cell engineering approaches and better understanding of the intricate tumor microenvironment (TME). Key challenges include treatment-related toxicity, antigen escape and heterogeneity, and the highly immunosuppressive profile of the TME. Notably, the hypoxic and nutrient-deprived nature of the TME severely attenuates CAR-T cell fitness and efficacy, highlighting the need for more sophisticated engineering strategies. In this review, we examine recent advances in protein- and cell-engineering strategies to improve CAR-T cell safety and efficacy, with an emphasis on overcoming immunosuppression induced by tumor metabolism and hypoxia.

Recent Advances in Solid Tumor CAR-T Cell Therapy: Driving Tumor Cells From Hero to Zero?

Chimeric antigen receptor T-cells (CAR-Ts) are known as revolutionary living drugs that have turned the tables of conventional cancer treatments in certain hematologic malignancies such as B-cell acute lymphoblastic leukemia (B-ALL) and diffuse large B-cell lymphoma (DLBCL) by achieving US Food and Drug Administration (FDA) approval based on their successful clinical outcomes. However, this type of therapy has not seen the light of victory in the fight against solid tumors because of various restricting caveats including heterogeneous tumor antigen expression and the immunosuppressive tumor microenvironments (TME) that negatively affect the tumor-site accessibility, infiltration, stimulation, activation, and persistence of CAR-Ts. In this review, we explore strategic twists including boosting vaccines and designing implementations that can support CAR-T expansion, proliferation, and tumoricidal capacity. We also step further by underscoring novel strategies for triggering endogenous antitumor responses and overcoming the limitation of poor CAR-T tumor-tissue infiltration and the lack of definitive tumor-specific antigens. Ultimately, we highlight how these approaches can address the mentioned arduous hurdles.

Modulating tumor physical microenvironment for fueling CAR-T cell therapy

Chimeric antigen receptor (CAR) T cell therapy has achieved unprecedented clinical success against hematologic malignancies. However, the transition of CAR-T cell therapies for solid tumors is limited by heterogenous antigen expression, immunosuppressive microenvironment (TME), immune adaptation of tumor cells and impeded CAR-T-cell infiltration/transportation. Recent studies increasingly reveal that tumor physical microenvironment could affect various aspects of tumor biology and impose profound impacts on the antitumor efficacy of CAR-T therapy. In this review, we discuss the critical roles of four physical cues in solid tumors for regulating the immune responses of CAR-T cells, which include solid stress, interstitial fluid pressure, stiffness and microarchitecture. We highlight new strategies exploiting these features to enhance the therapeutic potency of CAR-T cells in solid tumors by correlating with the state-of-the-art technologies in this field. A perspective on the future directions for developing new CAR-T therapies for solid tumor treatment is also provided.

Current and future perspectives of chimeric antigen receptors against glioblastoma

Glioblastoma multiforme (GBM) is the most malignant form of cancer in the central nervous system; even with treatment, it has a 5-year survival rate of 7.2%. The adoptive cell transfer (ACT) of T cells expressing chimeric antigen receptors (CARs) has shown a remarkable success against hematological malignancies, namely leukemia and multiple myeloma. However, CAR T cell therapy against solid tumors, and more specifically GBM, is still riddled with challenges preventing its widespread adoption. Here, we first establish the obstacles in ACT against GBM, including on-target/off-tumor toxicity, antigen modulation, tumor heterogeneity, and the immunosuppressive tumor microenvironment. We then present recent preclinical and clinical studies targeting well-characterized GBM antigens, which include the interleukin-13 receptor α2 and the epidermal growth factor receptor. Afterward, we turn our attention to alternative targets in GBM, including less-explored antigens such as B7-H3 (CD276), carbonic anhydrase IX, and the GD2 ganglioside. We also discuss additional target ligands, namely CD70, and natural killer group 2 member D ligands. Finally, we present the possibilities afforded by novel CAR architectures. In particular, we examine the use of armored CARs to improve the survival and proliferation of CAR T cells. We conclude by discussing the advantages of tandem and synNotch CARs when targeting multiple GBM antigens.

The Role of Chemokine IL-7 in Tumor and Its Potential Antitumor Immunity

Interleukin-7 (IL-7) is a cytokine belonging to the chemokine family. It plays a key role in the differentiation, development, and maturation of T lymphocytes and B lymphocytes, which is pivotal to adaptive immunity. In addition to its role in lymphocyte development, recent studies have indicated the antitumor functions of IL-7 in the tumor microenvironment. In this review, we discuss the role of IL-7 in tumors and summarize its antitumor potential and clinical application in lymphoma, leukemia, breast cancer, colon cancer, and so on. Furthermore, the combinational strategies of IL-7 and other antitumor drugs have been also discussed.

CAR-T cells for cancer immunotherapy-the barriers ahead and the paths through

This review discusses the major concerns and changes emerged during the rapidly extended clinical application of chimeric antigen receptor (CAR) T therapy based on our experience and understanding. In the past decades, the CAR-T cells have been questioned, sequentially, about their capability of inducing initial remission, their safety profile, their ability to sustain long-term persistence and response, and their potential to be industrialized. Significant advances, novel targeting strategies, innovative molecular structure, fine tuning of both CAR-T and host immune system, combination with other therapies, streamlined manufacturing, and etc., have been made to overcome these challenges. Although not perfectly resolved, rational pathways have been proposed to pass through the barriers. Here, we present the recent achievements on these pathways, and look into the possible future directions.

A novel multimeric sCD19-streptavidin fusion protein for functional detection and selective expansion of CD19-targeted CAR-T cells

Background

CARs are engineered receptors comprising an immunoglobulin single‐chain variable fragment (scFv) that identifies and binds to the target antigen, a transmembrane domain, and an intracellular T‐cell signaling domain. CD19 is a B lineage‐specific transmembrane glycoprotein and is expressed in more than 95% of B‐cell malignancies. Streptavidin (SA) is a homo‐tetrameric protein derived from Streptomyces avidinii, which can bind four biotin molecules with an extremely high affinity at a Kd value of 10^‐15 M.

Aims

The aim of the study is to generate a novel soluble multimeric fusion protein, sCD19‐streptavidin (sCD19‐SA) for functional detection and selective expansion of CD19‐targeted CAR‐T cells.

Methods

The fusion proteins CD19‐SA was expressed in CHO cells and purified by use of Ni‐nitrilotriacetic acid agarose beads.

Results

A novel fusion protein (sCD19‐SA) was generated, consisting of the extracellular domain of human CD19 and the core region of SA, and could be used to functionally detect CD19‐targeted CAR‐T cells. Furthermore, this protein was demonstrated to form multimers to activate CAR‐T cells to induce their selective expansion. Importantly, sCD19‐SA‐stimulated CD19‐targeted CAR‐T cells could improve antitumor effects in vivo.

Conclusions

Our study has highlighted the potential of utilizing antigen‐SA fusion proteins such as sCD19‐SA for CAR‐T therapy for the functional detection of CAR expression and selective expansion of CAR‐T cells.

The Single-Cell Level Perspective of the Tumor Microenvironment and Its Remodeling by CAR-T Cells

The tumor microenvironment (TME) is a complex milieu consisting of lymphoid cells, myeloid cells, fibroblasts, and multiple molecules, which play a key role in tumor progression and immunotherapy. TME is characterized by immune-suppressive features, which release anti-inflammatory cytokines such as IL-4 and TGFβ to skew the T cells to a Th2 state as well to polarize tumor-associated macrophages (TAMs) to an anti-inflammatory phenotype to curb the immunotherapy. Considering the heterogeneity of the TME and its role in determining response to chimeric antigen receptor (CAR)-T cells, delineating TME at a single-cell level will provide useful information for cancer treatment. First, we discuss cellular and molecular features that curb the response to CAR-T cells, for example, high expression of immune checkpoint molecules (PD-1, LAG3) and anti-inflammatory cytokines (IL-4, TGFb) that block CAR-T cell function. Then, we summarize how newly invented single-cell technologies such as spatial multi-omics would benefit the understanding of cancer immunotherapy. Finally, we will further describe recent attempts of CAR-T to remodel TME by arming the CAR-T with anti-PD-1 single-chain variants or Th1 triggering cytokines (such as IL-7, IL-12) to remodel TME into a pro-inflammatory state. Herein, we review the single-cell-level signatures of TME and the strategies of CAR-T to remodel TME.

CCL19 has potential to be a potential prognostic biomarker and a modulator of tumor immune microenvironment (TIME) of breast cancer: a comprehensive analysis based on TCGA database

The development of cancer was determined by not only the intrinsic properties of cancer cells, but also the communication between cancer cells and tumor microenvironment (TME). We applied ESTIMATE and CIBERSORT algorithms to calculate the immune/stromal component and tumor-infiltrating immune cells (TICs) in TME of BC. The results showed that immune component in TME predicted patients’ survival and associated with progression of BC. Differentially expressed genes (DEGs) were primarily enriched in immune-related activities. Finally, CCL19 was acquired which shared the leading nodes in PPI network and was associated with patients’ survival. High expression of CCL19 predicted better prognosis and participated in progression of BC. Genes in CCL19 up-regulated group were enriched in immune-related activities and these functions might depend on the communications between CCL19 and multiple TICs in TIME. In conclusion, CCL19 functioned as a potential prognostic biomarker and a modulator of TIME in BC through communicating with various TICs.

Enhanced safety and efficacy of protease-regulated CAR-T cell receptors

Regulatable CAR platforms could circumvent toxicities associated with CAR-T therapy, but existing systems have shortcomings including leakiness and attenuated activity. Here, we present SNIP CARs, a protease-based platform for regulating CAR activity using an FDA-approved small molecule. Design iterations yielded CAR-T cells that manifest full functional capacity with drug and no leaky activity in the absence of drug. In numerous models, SNIP CAR-T cells were more potent than constitutive CAR-T cells and showed diminished T cell exhaustion and greater stemness. In a ROR1-based CAR lethality model, drug cessation following toxicity onset reversed toxicity, thereby credentialing the platform as a safety switch. In the same model, reduced drug dosing opened a therapeutic window that resulted in tumor eradication in the absence of toxicity. SNIP CARs enable remote tuning of CAR activity, which provides solutions to safety and efficacy barriers that are currently limiting progress in using CAR-T cells to treat solid tumors.

Time to evolve: predicting engineered T cell-associated toxicity with next-generation models

Despite promising clinical results in a small subset of malignancies, therapies based on engineered chimeric antigen receptor and T-cell receptor T cells are associated with serious adverse events, including cytokine release syndrome and neurotoxicity. These toxicities are sometimes so severe that they significantly hinder the implementation of this therapeutic strategy. For a long time, existing preclinical models failed to predict severe toxicities seen in human clinical trials after engineered T-cell infusion. However, in recent years, there has been a concerted effort to develop models, including humanized mouse models, which can better recapitulate toxicities observed in patients. The Accelerating Development and Improving Access to CAR and TCR-engineered T cell therapy (T2EVOLVE) consortium is a public–private partnership directed at accelerating the preclinical development and increasing access to engineered T-cell therapy for patients with cancer. A key ambition in T2EVOLVE is to design new models and tools 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. Herein, we review existing preclinical models that are used to test the safety of engineered T cells. We will also highlight limitations of these models and propose potential measures to improve them.

A novel adoptive synthetic TCR and antigen receptor (STAR) T-Cell therapy for B-Cell acute lymphoblastic leukemia

We developed a T-cell-receptor (TCR) complex-based chimeric antigen receptor (CAR) named Synthetic TCR and Antigen Receptor (STAR). Here, we report pre-clinical and phase I clinical trial data (NCT03953599) of this T-cell therapy for refractory and relapsed (R/R) B-cell acute lymphoblastic leukemia (B-ALL) patients. STAR consists of two protein modules each containing an antibody light or heavy chain variable region and TCR α or β chain constant region fused to the co-stimulatory domain of OX40. T-cells were transduced with a STAR-OX40 lentiviral vector. A leukemia xenograft mouse model was used to assess the STAR/STAR-OX40 T cell antitumor activity. Eighteen patients with R/R B-ALL were enrolled into the clinical trial. In a xenograft mouse model, STAR-T-cells exhibited superior tumor-specific cytotoxicity compared with conventional CAR-T cells. Incorporating OX40 into STAR further improved the proliferation and persistence of tumor-targeting T-cells. In our clinical trial, 100% of patients achieved complete remission 4 weeks post-STAR-OX40 T-cell infusion and 16/18 (88.9%) patients pursued consolidative allogeneic hematopoietic stem cell transplantation (allo-HSCT). Twelve of 16 patients (75%) remained leukemia-free after a median follow-up of 545 (433-665) days. The two patients without consolidative allo-HSCT relapsed on Day 58 and Day 186. Mild cytokine release syndrome occurred in 10/18 (55.6%) patients, and 2 patients experienced grade III neurotoxicity. Our preclinical studies demonstrate super anti-tumor potency of STAR-OX40 T-cells compared with conventional CAR-T cells. The first-in-human clinical trial shows that STAR-OX40 T-cells are tolerable and an effective therapeutic platform for treating R/R B-ALL.

Emerging Strategies in TCR-Engineered T Cells

Immunotherapy of cancer has made tremendous progress in recent years, as demonstrated by the remarkable clinical responses obtained from adoptive cell transfer (ACT) of patient-derived tumor infiltrating lymphocytes, chimeric antigen receptor (CAR)-modified T cells (CAR-T) and T cell receptor (TCR)-engineered T cells (TCR-T). TCR-T uses specific TCRS optimized for tumor engagement and can recognize epitopes derived from both cell-surface and intracellular targets, including tumor-associated antigens, cancer germline antigens, viral oncoproteins, and tumor-specific neoantigens (neoAgs) that are largely sequestered in the cytoplasm and nucleus of tumor cells. Moreover, as TCRS are naturally developed for sensitive antigen detection, they are able to recognize epitopes at far lower concentrations than required for CAR-T activation. Therefore, TCR-T holds great promise for the treatment of human cancers. In this focused review, we summarize basic, translational, and clinical insights into the challenges and opportunities of TCR-T. We review emerging strategies used in current ACT, point out limitations, and propose possible solutions. We highlight the importance of targeting tumor-specific neoAgs and outline a strategy of combining neoAg vaccines, checkpoint blockade therapy, and adoptive transfer of neoAg-specific TCR-T to produce a truly tumor-specific therapy, which is able to penetrate into solid tumors and resist the immunosuppressive tumor microenvironment. We believe such a combination approach should lead to a significant improvement in cancer immunotherapies, especially for solid tumors, and may provide a general strategy for the eradication of multiple cancers.

Reprogramming the tumor microenvironment by genome editing for precision cancer therapy

The tumor microenvironment (TME) is essential for immune escape by tumor cells. It plays essential roles in tumor development and metastasis. The clinical outcomes of tumors are often closely related to individual differences in the patient TME. Therefore, reprogramming TME cells and their intercellular communication is an attractive and promising strategy for cancer therapy. TME cells consist of immune and nonimmune cells. These cells need to be manipulated precisely and safely to improve cancer therapy. Furthermore, it is encouraging that this field has rapidly developed in recent years with the advent and development of gene editing technologies. In this review, we briefly introduce gene editing technologies and systematically summarize their applications in the TME for precision cancer therapy, including the reprogramming of TME cells and their intercellular communication. TME cell reprogramming can regulate cell differentiation, proliferation, and function. Moreover, reprogramming the intercellular communication of TME cells can optimize immune infiltration and the specific recognition of tumor cells by immune cells. Thus, gene editing will pave the way for further breakthroughs in precision cancer therapy.

Special Chimeric Antigen Receptor (CAR) Modifications of T Cells: A Review

Chimeric antigen receptor (CAR) -T cell therapy has become one of the hot topics in tumor immunity research in recent years. Although CAR-T cell therapy is highly effective in treating hematological malignancies, there are numerous obstacles that prevent CAR-T cells from having anti-tumor effects. Traditional CARs, from the first to the fourth generation, are incapable of completely overcoming these challenges. Therefore, identifying ways to boost the efficacy of CAR-T cells by utilizing the limited tumor surface antigens has become an urgent area of research. Certain special CARs that have special structures, special systems, or are greatly improved on the basis of traditional CARs, such as tandem CAR, dual-signaling CARs, AND-gate CARs, inhibitory CAR, AND-NOT CARs, CARs with three scFvs, ON/OFF-switch CARs, and universal CARs have been introduced. This study aims to use these special CARs to improve the anti-tumor ability, accuracy, and safety of CAR-T cells. In addition to summarizing various special CARs of T cells, this paper also expounds some of our own conjectures, aiming to provide reference and inspiration for CARs researchers.

Multipurposing CARs: Same engine, different vehicles

T cells genetically engineered to recognize and eliminate tumor cells through synthetic chimeric antigen receptors (CARs) have demonstrated remarkable clinical efficacy against B cell leukemia over the past decade. This therapy is a form of highly personalized medicine that involves genetically modifying a patient's T cells to recognize and kill cancer cells. With the FDA approval of 5 CAR T cell products, this approach has been validated as a powerful new drug in the therapeutic armamentarium against cancer. Researchers are now studying how to expand this technology beyond its use in conventional polyclonal αβ T cells to address limitations to the current therapy in cancer and applications beyond it. Considering the specific characteristics of immune cell from diverse lineages, several preclinical and clinical studies are under way to assess the advantages of CAR-redirected function in these cells and apply the lessons learned from CAR T cell therapy in cancer to other diseases.

Harnessing cytokines and chemokines for cancer therapy

During the past 40 years, cytokines and cytokine receptors have been extensively investigated as either cancer targets or cancer treatments. A strong preclinical rationale supports therapeutic strategies to enhance the growth inhibitory and immunostimulatory effects of interferons and interleukins, including IL-2, IL-7, IL-12 and IL-15, or to inhibit the inflammatory and tumour-promoting actions of cytokines such as TNF, IL-1β and IL-6. This rationale is underscored by the discovery of altered and dysregulated cytokine expression in all human cancers. These findings prompted clinical trials of several cytokines or cytokine antagonists, revealing relevant biological activity but limited therapeutic efficacy. However, most trials involved patients with advanced-stage disease, which might not be the optimal setting for cytokine-based therapy. The advent of more effective immunotherapies and an increased understanding of the tumour microenvironment have presented new approaches to harnessing cytokine networks in the treatment of cancer, which include using cytokine-based therapies to enhance the activity or alleviate the immune-related toxicities of other treatments as well as to target early stage cancers. Many challenges remain, especially concerning delivery methods, context dependencies, and the pleiotropic, redundant and often conflicting actions of many cytokines. Herein, we discuss the lessons learnt from the initial trials of single-agent cytokine-based therapies and subsequent efforts to better exploit such agents for the treatment of solid tumours.

CXCL9-modified CAR T cells improve immune cell infiltration and antitumor efficacy

Chimeric antigen receptor (CAR) T cells remain unsatisfactory in treating solid tumors. The frequency of tumor-infiltrating T cells is closely related to the good prognosis of patients. Augmenting T cell accumulation in the tumor microenvironment is essential for tumor clearance. To overcome insufficient immune cell infiltration, innovative CAR designs need to be developed immediately. CXCL9 plays a pivotal role in regulating T cell migration and inhibiting tumor angiogenesis. Therefore, we engineered CAR T cells expressing CXCL9 (CART-CXCL9). The addition of CXCL9 enhanced cytokine secretion and cytotoxicity of CAR T cells and endowed CAR T cells with the ability to recruit activated T cells and antiangiogenic effect. In tumor-bearing mice, CART-CXCL9 cells attracted more T cell trafficking to the tumor site and inhibited angiogenesis than conventional CAR T cells. Additionally, CART-CXCL9 cell therapy slowed tumor growth and prolonged mouse survival, displaying superior antitumor activity. Briefly, modifying CAR T cells to express CXCL9 could effectively improve CAR T cell efficacy against solid tumors.

Development of a TCR-like antibody and chimeric antigen receptor against NY-ESO-1/HLA-A2 for cancer immunotherapy

Background

The current therapeutic antibodies and chimeric antigen receptor (CAR) T cells are capable of recognizing surface antigens, but not of intracellular proteins, thus limiting the target coverage for drug development. To mimic the feature of T-cell receptor (TCR) that recognizes the complex of major histocompatibility class I and peptide on the cell surface derived from the processed intracellular antigen, we used NY-ESO-1, a cancer-testis antigen, to develop a TCR-like fully human IgG1 antibody and its derivative, CAR-T cells, for cancer immunotherapy.

Methods

Human single-chain variable antibody fragment (scFv) phage library (~10^∧11) was screened against HLA-A2/NY-ESO-1 (peptide 157–165) complex to obtain target-specific antibodies. The specificity and affinity of those antibodies were characterized by flow cytometry, ELISA, biolayer interferometry, and confocal imaging. The biological functions of CAR-T cells were evaluated against target tumor cells in vitro. In vivo antitumor activity was investigated in a triple-negative breast cancer (TNBC) model and primary melanoma tumor model in immunocompromised mice.

Results

Monoclonal antibody 2D2 identified from phage-displayed library specifically bound to NY-ESO-1_157-165 in the context of human leukocyte antigen HLA-A*02:01 but not to non-A2 or NY-ESO-1 negative cells. The second-generation CAR-T cells engineered from 2D2 specifically recognized and eliminated A2+/NY-ESO-1+tumor cells in vitro, inhibited tumor growth, and prolonged the overall survival of mice in TNBC and primary melanoma tumor model in vivo.

Conclusions

This study showed the specificity of the antibody identified from human scFv phage library and demonstrated the potential antitumor activity by TCR-like CAR-T cells both in vitro and in vivo, warranting further preclinical and clinical evaluation of the TCR-like antibody in patients. The generation of TCR-like antibody and its CAR-T cells provides the state-of-the-art platform and proof-of-concept validation to broaden the scope of target antigen recognition and sheds light on the development of novel therapeutics for cancer immunotherapy.

Human induced-T-to-natural killer cells have potent anti-tumour activities

BACKGROUND

Adoptive cell therapy (ACT) is a particularly promising area of cancer immunotherapy, engineered T and NK cells that express chimeric antigen receptors (CAR) are being explored for treating hematopoietic malignancies but exhibit limited clinical benefits for solid tumour patients, successful cellular immunotherapy of solid tumors demands new strategies.

METHODS

Inactivation of BCL11B were performed by CRISPR/Cas9 in human T cells. Immunophenotypic and transcriptional profiles of sgBCL11B T cells were characterized by cytometer and transcriptomics, respectively. sgBCL11B T cells are further engineered with chimeric antigen receptor. Anti-tumor activity of ITNK or CAR-ITNK cells were evaluated in preclinical and clinical studies.

RESULTS

We report that inactivation of BCL11B in human CD8⁺ and CD4⁺ T cells induced their reprogramming into induced T-to-natural killer cells (ITNKs). ITNKs contained a diverse TCR repertoire; downregulated T cell-associated genes such as TCF7 and LEF1; and expressed high levels of NK cell lineage-associated genes. ITNKs and chimeric antigen receptor (CAR)-transduced ITNKs selectively lysed a variety of cancer cells in culture and suppressed the growth of solid tumors in xenograft models. In a preliminary clinical study, autologous administration of ITNKs in patients with advanced solid tumors was well tolerated, and tumor stabilization was seen in six out nine patients, with one partial remission.

CONCLUSIONS

The novel ITNKs thus may be a promising novel cell source for cancer immunotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03882840 . Registered 20 March 2019-Retrospectively registered.

The next wave of cellular immunotherapies in pancreatic cancer

Pancreatic cancer is an aggressive disease that is predicted to become the second leading cause of cancer-related death worldwide by 2030. The overall 5-year survival rate is around 10%. Pancreatic cancer typically presents late with locally advanced or metastatic disease, and there are limited effective treatments available. Cellular immunotherapy, such as chimeric antigen receptor (CAR) T cell therapy, has had significant success in treating hematological malignancies. However, CAR T cell therapy efficacy in pancreatic cancer has been limited. This review provides an overview of current and ongoing CAR T cell clinical studies of pancreatic cancer and the major challenges and strategies to improve CAR T cell efficacy. These strategies include arming CAR T cells; developing off-the-shelf allogeneic CAR T cells; using other immune CAR cells, like natural killer cells and tumor-infiltrating lymphocytes; and combination therapy. Careful incorporation of preclinical models will enhance management of affected individuals, assisting incorporation of cellular immunotherapies. A multifaceted, personalized approach involving cellular immunotherapy treatment is required to improve pancreatic cancer outcomes.

Harnessing the chemokine system to home CAR-T cells into solid tumors

CAR-T cell therapy has been heralded as a breakthrough in the field of immunotherapy, but to date, this success has been limited to hematological malignancies. By harnessing the chemokine system and taking into consideration the chemokine expression profile in the tumor microenvironment, CAR-T cells may be homed into tumors to facilitate direct tumor cell cytolysis and overcome a major hurdle in generating effective CAR-T cell responses to solid cancers.

Emerging Novel Combined CAR-T Cell Therapies

Simple Summary

As a result of FDA approval of CAR-T cell treatments in the last few years, this immunotherapy has provided further direction to precision medicine through its combination with other therapeutic approaches. In the past year, several review articles have been published focusing on advances in this fast-developing field, especially with respect to efforts to overcome hurdles associated with applying CAR-T cells in solid tumors. This review paper focuses on combining CAR-T cell therapy with small molecule drugs, up-to-date progress in CAR-T cell therapy research, and advances in combined CAR-T immunotherapy with other treatments targeting solid tumors.

Abstract

Chimeric antigen receptors (CAR) T cells are T cells engineered to express membrane receptors with high specificity to recognize specific target antigens presented by cancer cells and are co-stimulated with intracellular signals to increase the T cell response. CAR-T cell therapy is emerging as a novel therapeutic approach to improve T cell specificity that will lead to advances in precision medicine. CAR-T cells have had impressive outcomes in hematological malignancies. However, there continue to be significant limitations of these therapeutic responses in targeting solid malignancies such as heterogeneous antigens in solid tumors, tumor immunosuppressive microenvironment, risk of on-target/off-tumor, infiltrating CAR-T cells, immunosuppressive checkpoint molecules, and cytokines. This review paper summarizes recent approaches and innovations through combination therapies of CAR-T cells and other immunotherapy or small molecule drugs to counter the above disadvantages to potentiate the activity of CAR-T cells.

Folate Receptor-Alpha Targeted 7x19 CAR-γδT Suppressed Triple-Negative Breast Cancer Xenograft Model in Mice

Background

Triple-negative breast cancer (TNBC) is the worst prognosis subtype of breast cancer due to lack of specific targets. Recent studies have shown that immunotherapy may solve that problem by targeting folate receptor-alpha (FRα).

Methods

Gene modified γδ T cells were manufactured to express FRa specific chimeric antigen receptor (FRa CAR) and secrete interleukin-7 (IL-7) and chemokine C–C motif ligand 19 (CCL19). CAR-γδT cells that secrete IL-7 and CCL19 (7 × 19 CAR-γδT) were evaluated for their antitumor activity both in vitro and in vivo.

Results

7 × 19 CAR-γδT showed remarkable antitumor activity in vitro. Combined with PBMC, 7 × 19 CAR-γδT inhibited TNBC xenograft model growth superiorly compared with single-application or conventional CAR-γδT cells. Histopathological analyses showed increased DC or T cells infiltration to tumor tissues.

Conclusion

Taken together, our results showed that 7 × 19 CAR-γδT have remarkable anti-TNBC tumor activity and showed a broad application prospect in the treatment of incurable TNBC patients.

Reversing chemokine/chemokine receptor mismatch to enhance the antitumor efficacy of CAR-T cells

Currently, the antitumor efficacy of chimeric antigen receptor T cells in solid tumors is modest. Both chemokines and their receptors play a key role in the proliferation of cancer cells, tumor angiogenesis, organ-selective metastasis and migration of immune cells to solid tumors. Unfortunately, frequent chemokine/chemokine receptor 'mismatch' between effector cells and the tumor microenvironment results in inefficient T-cell infiltration and antitumor efficacy. Thus, reversing the 'mismatch' of chemokines and chemokine receptors appears to be a promising method for promoting T-cell infiltration into the tumor and enhancing their antitumor efficacy. In this review, we discuss functions of the chemokine/chemokine receptor axis in cancer immunity and the current understanding, challenges and prospects for improving the effect of chimeric antigen receptor T cells by reversing the mismatch between chemokines and chemokine receptors.

Engineering CAR T cells for enhanced efficacy and safety

Despite its success in treating hematologic malignancies, chimeric antigen receptor (CAR) T cell therapy faces two major challenges which hinder its broader applications: the limited effectiveness against solid tumors and the nonspecific toxicities. To address these concerns, researchers have used synthetic biology approaches to develop optimization strategies. In this review, we discuss recent improvements on the CAR and other non-CAR molecules aimed to enhance CAR T cell efficacy and safety. We also highlight the development of different types of inducible CAR T cells that can be controlled by environmental cues and/or external stimuli. These advancements are bringing CAR T therapy one step closer to safer and wider applications, especially for solid tumors.

Engineering interferons and interleukins for cancer immunotherapy

Cytokines are a class of potent immunoregulatory proteins that are secreted in response to various stimuli and act locally to regulate many aspects of human physiology and disease. Cytokines play important roles in cancer initiation, progression, and elimination, and thus, there is a long clinical history associated with the use of recombinant cytokines to treat cancer. However, the use of cytokines as therapeutics has been limited by cytokine pleiotropy, complex biology, poor drug-like properties, and severe dose-limiting toxicities. Nevertheless, cytokines are crucial mediators of innate and adaptive antitumor immunity and have the potential to enhance immunotherapeutic approaches to treat cancer. Development of immune checkpoint inhibitors and combination immunotherapies has reinvigorated interest in cytokines as therapeutics, and a variety of engineering approaches are emerging to improve the safety and effectiveness of cytokine immunotherapy. In this review we highlight recent advances in cytokine biology and engineering for cancer immunotherapy.

Chimeric antigen receptor T cell therapy: challenges and opportunities in lung cancer

Chimeric antigen receptor (CAR) T-cell therapy has revolutionized the paradigm in hematological malignancies treatment, driving an ever-expanding number of basic research and clinical trials of genetically engineering T cells to treat solid tumors. CAR T-cell therapies based on the antibodies targeting Mesothelin, CEA, EGFR, EGFR, MUC1, DLL3, and emerging novel targets provide promising efficacy for lung cancer patients. However, clinical application of CAR T-cell therapy against lung cancer remains limited on account of physical and immune barriers, antigen escape and heterogeneity, on-target off-tumor toxicity, and many other reasons. Understanding the evolution of CAR structure and the generalizable requirements for manufacturing CAR T cells as well as the interplay between lung tumor immunology and CAR T cells will improve clinical translation of this therapeutic modality in lung cancer. In this review, we systematically summarize the latest advances in CAR T-cell therapy in lung cancer, focusing on the CAR structure, target antigens, challenges, and corresponding new strategies.

Controlling Cell Trafficking: Addressing Failures in CAR T and NK Cell Therapy of Solid Tumours

The precision guiding of endogenous or adoptively transferred lymphocytes to the solid tumour mass is obligatory for optimal anti-tumour effects and will improve patient safety. The recognition and elimination of the tumour is best achieved when anti-tumour lymphocytes are proximal to the malignant cells. For example, the regional secretion of soluble factors, cytotoxic granules, and cell-surface molecule interactions are required for the death of tumour cells and the suppression of neovasculature formation, tumour-associated suppressor, or stromal cells. The resistance of individual tumour cell clones to cellular therapy and the hostile environment of the solid tumours is a major challenge to adoptive cell therapy. We review the strategies that could be useful to overcoming insufficient immune cell migration to the tumour cell mass. We argue that existing 'competitive' approaches should now be revisited as complementary approaches to improve CAR T and NK cell therapy.