A VHH-Based Anti-MUC1 Chimeric Antigen Receptor for Specific Retargeting of Human Primary T Cells to MUC1-Positive Cancer Cells

Comparative performance of scFv-based anti-BCMA CAR formats for improved T cell therapy in multiple myeloma

In multiple myeloma (MM), B cell maturation antigen (BCMA)-directed CAR T cells have emerged as a novel therapy with potential for long-term disease control. Anti-BCMA CAR T cells with a CD8-based transmembrane (TM) and CD137 (41BB) as intracellular costimulatory domain are in routine clinical use. As the CAR construct architecture can differentially impact performance and efficacy, the optimal construction of a BCMA-targeting CAR remains to be elucidated. Here, we hypothesized that varying the constituents of the CAR structure known to impact performance could shed light on how to improve established anti-BCMA CAR constructs. CD8TM.41BBIC-based anti-BCMA CAR vectors with either a long linker or a short linker between the light and heavy scFv chain, CD28TM.41BBIC-based and CD28TM.CD28IC-based anti-BCMA CAR vector systems were used in primary human T cells. MM cell lines were used as target cells. The short linker anti-BCMA CAR demonstrated higher cytokine production, whereas in vitro cytotoxicity, T cell differentiation upon activation and proliferation were superior for the CD28TM.CD28IC-based CAR. While CD28TM.CD28IC-based CAR T cells killed MM cells faster, the persistence of 41BBIC-based constructs was superior in vivo. While CD28 and 41BB costimulation come with different in vitro and in vivo advantages, this did not translate into a superior outcome for either tested model. In conclusion, this study showcases the need to study the influence of different CAR architectures based on an identical scFv individually. It indicates that current scFv-based anti-BCMA CAR with clinical utility may already be at their functional optimum regarding the known structural variations of the scFv linker.

MICA-specific nanobodies for diagnosis and immunotherapy of MICA+ tumors

MICA and MICB are Class I MHC-related glycoproteins that are upregulated on the surface of cells in response to stress, for instance due to infection or malignant transformation. MICA/B are ligands for NKG2D, an activating receptor on NK cells, CD8+ T cells, and γδ T cells. Upon engagement of MICA/B with NKG2D, these cytotoxic cells eradicate MICA/B-positive targets. MICA is frequently overexpressed on the surface of cancer cells of epithelial and hematopoietic origin. Here, we created nanobodies that recognize MICA. Nanobodies, or VHHs, are the recombinantly expressed variable regions of camelid heavy chain-only immunoglobulins. They retain the capacity of antigen recognition but are characterized by their stability and ease of production. The nanobodies described here detect surface-disposed MICA on cancer cells in vitro by flow cytometry and can be used therapeutically as nanobody-drug conjugates when fused to the Maytansine derivative DM1. The nanobody-DM1 conjugate selectively kills MICA positive tumor cells in vitro.

Humanized single-domain antibody targeting HER2 enhances function of chimeric antigen receptor T cells

Introduction

Chimeric antigen receptors (CARs) can redirect T cells against antigen-expressing tumors, and each component plays an important role in the function and anti-tumor efficacy. It has been reported that using human sequences or a low affinity of CAR single-chain variable fragments (scFvs) in the CAR binding domains is a potential way to enhance the function of CAR-T cells. However, it remains largely unknown how a lower affinity of CARs using humanized scFvs affects the function of CAR-T cells until recently.

Methods

We used different humanized anti-HER2 antibodies as the extracellular domain of CARs and further constructed a series of the CAR-T cells with different affinity.

Results

We have observed that moderately reducing the affinity of CARs (light chain variable domain (VL)-based CAR-T) could maintain the anti-tumor efficacy, and improved the safety of CAR therapy both in vitro and in vivo compared with high-affinity CAR-T cells. Moreover, T cells expressing the VL domain only antibody exhibited long-lasting tumor elimination capability after multiple challenges in vitro, longer persistence and lower cytokine levels in vivo.

Discussion

Our findings provide an alternative option for CAR-T optimization with the potential to widen the use of CAR T cells.

New cell sources for CAR-based immunotherapy

Chimeric antigen receptor (CAR) T cell therapy, in which a patient's own T lymphocytes are engineered to recognize and kill cancer cells, has achieved striking success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Despite impressive clinical outcomes, concerns about treatment failure associated with low efficacy or high cytotoxicity of CAR-T cells remain. While the main focus has been on improving CAR-T cells, exploring alternative cellular sources for CAR generation has garnered growing interest. In the current review, we comprehensively evaluated other cell sources rather than conventional T cells for CAR generation.

Nanobodies in cell-mediated immunotherapy: On the road to fight cancer

The immune system is essential in recognizing and eliminating tumor cells. The unique characteristics of the tumor microenvironment (TME), such as heterogeneity, reduced blood flow, hypoxia, and acidity, can reduce the efficacy of cell-mediated immunity. The primary goal of cancer immunotherapy is to modify the immune cells or the TME to enable the immune system to eliminate malignancies successfully. Nanobodies, known as single-domain antibodies, are light chain-free antibody fragments produced from Camelidae antibodies. The unique properties of nanobodies, including high stability, reduced immunogenicity, enhanced infiltration into the TME of solid tumors and facile genetic engineering have led to their promising application in cell-mediated immunotherapy. They can promote the cancer therapy either directly by bridging between tumor cells and immune cells and by targeting cancer cells using immune cell-bound nanobodies or indirectly by blocking the inhibitory ligands/receptors. The T-cell activation can be engaged through anti-CD3 and anti-4-1BB nanobodies in the bispecific (bispecific T-cell engagers (BiTEs)) and trispecific (trispecific T-cell engager (TriTEs)) manners. Also, nanobodies can be used as natural killer (NK) cell engagers (BiKEs, TriKEs, and TetraKEs) to create an immune synapse between the tumor and NK cells. Nanobodies can redirect immune cells to attack tumor cells through a chimeric antigen receptor (CAR) incorporating a nanobody against the target antigen. Various cancer antigens have been targeted by nanobody-based CAR-T and CAR-NK cells for treating both hematological and solid malignancies. They can also cause the continuation of immune surveillance against tumor cells by stopping inappropriate inhibition of immune checkpoints. Other roles of nanobodies in cell-mediated cancer immunotherapy include reprogramming macrophages to reduce metastasis and angiogenesis, as well as preventing the severe side effects occurring in cell-mediated immunotherapy. Here, we highlight the critical functions of various immune cells, including T cells, NK cells, and macrophages in the TME, and discuss newly developed immunotherapy methods based on the targeted manipulation of immune cells and TME with nanobodies.

Pan-Cancer Analysis Identifies Tumor Cell Surface Targets for CAR-T Cell Therapies and Antibody Drug Conjugates

Tumor cells can be recognized through tumor surface antigens by immune cells and antibodies, which therefore can be used as drug targets for chimeric antigen receptor-T (CAR-T) therapies and antibody drug conjugates (ADCs). In this study, we aimed to identify novel tumor-specific antigens as targets for more effective and safer CAR-T cell therapies and ADCs. Here, we performed differential expression analysis of pan-cancer data obtained from the Cancer Genome Atlas (TCGA), and then performed a series of conditional screenings including Cox regression analysis, Pearson correlation analysis, and risk-score calculation to find tumor-specific cell membrane genes. A tumor tissue-specific and highly expressed gene set containing 3919 genes from 17 cancer types was obtained. Moreover, the prognostic roles of these genes and the functions of these highly expressed membrane proteins were assessed. Notably, 427, 584, 431 and 578 genes were identified as risk factors for LIHC, KIRC, UCEC, and KIRP, respectively. Functional enrichment analysis indicated that these tumor-specific surface proteins might confer tumor cells the ability to invade and metastasize. Furthermore, correlation analysis displayed that most overexpressed membrane proteins were positively correlated to each other. In addition, 371 target membrane protein-coding genes were sifted out by excluding proteins expressed in normal tissues. Apart from the identification of well-validated genes such as GPC3, MSLN and EGFR in the literature, we further confirmed the differential protein expression of 23 proteins: ADD2, DEF6, DOK3, ENO2, FMNL1, MICALL2, PARVG, PSTPIP1, FERMT1, PLEK2, CD109, GNG4, MAPT, OSBPL3, PLXNA1, ROBO1, SLC16A3, SLC26A6, SRGAP2, and TMEM65 in four types of tumors. In summary, our findings reveal novel tumor-specific antigens, which could be potentially used for next-generation CAR-T cell therapies and ADC discovery.

Advances in Promoting the Efficacy of Chimeric Antigen Receptor T Cells in the Treatment of Hepatocellular Carcinoma

HCC, one of the most common and deadly cancers worldwide, develops from hepatocytes and accounts for more than 90% of primary liver cancers. The current widely used treatment modalities are far from meeting the needs of liver cancer patients. CAR-T cell therapy, which has recently emerged, has shown promising efficacy in lymphoma and hematologic cancers, but there are still many challenges to overcome in its application to the clinical treatment of HCC, including osmotic barriers, the inhibition of hepatocellular carcinoma microenvironment activity, the limited survival and killing ability of CAR-T cells, and inevitable side effects, among others. As a result, a number of studies have begun to address the suboptimal efficacy of CAR-T cells in HCC, and many of these schemes hold good promise. This review focuses on advances in the past five years aimed at promoting the efficacy of CAR-T cell therapy for treatment of HCC.

CAR T cells redirected against tumor-specific antigen glycoforms: can low-sugar antigens guarantee a sweet success?

Immune-based therapies have experienced a pronounced breakthrough in the past decades as they acquired multiple US Food and Drug Administration (FDA) approvals for various indications. To date, six chimeric antigen receptor T cell (CAR-T) therapies have been permitted for the treatment of certain patients with relapsed/refractory hematologic malignancies. However, several clinical trials of solid tumor CAR-T therapies were prematurely terminated, or they reported life-threatening treatment-related damages to healthy tissues. The simultaneous expression of target antigens by healthy organs and tumor cells is partly responsible for such toxicities. Alongside targeting tumor-specific antigens, targeting the aberrantly glycosylated glycoforms of tumor-associated antigens can also minimize the off-tumor effects of CAR-T therapies. Tn, T, and sialyl-Tn antigens have been reported to be involved in tumor progression and metastasis, and their expression results from the dysregulation of a series of glycosyltransferases and the endoplasmic reticulum protein chaperone, Cosmc. Moreover, these glycoforms have been associated with various types of cancers, including prostate, breast, colon, gastric, and lung cancers. Here, we discuss how underglycosylated antigens emerge and then detail the latest advances in the development of CAR-T-based immunotherapies that target some of such antigens.

A comprehensive comparison between camelid nanobodies and single chain variable fragments

By the emergence of recombinant DNA technology, many antibody fragments have been developed devoid of undesired properties of natural immunoglobulins. Among them, camelid heavy-chain variable domains (VHHs) and single-chain variable fragments (scFvs) are the most favored ones. While scFv is used widely in various applications, camelid antibodies (VHHs) can serve as an alternative because of their superior chemical and physical properties such as higher solubility, stability, smaller size, and lower production cost. Here, these two counterparts are compared in structure and properties to identify which one is more suitable for each of their various therapeutic, diagnosis, and research applications.

Spinoculation and retronectin highly enhance the gene transduction efficiency of Mucin-1-specific chimeric antigen receptor (CAR) in human primary T cells

Background

Producing an appropriate number of engineered cells is considered as one of the influential factors in the successful treatments with chimeric antigen receptor (CAR) T cells. To this aim, the transduction rate of the viral vectors can play a significant role. In addition, improving transduction rates can affect the success rate of this treatment due to hard-transduced T lymphocytes.

Results

In this study, activated T cells were transduced using different transduction methods such as spinoculation, retronectin, polybrene, spinoculation + retronectin, and spinoculation + polybrene after selecting the most efficient transfection method to produce recombinant viral particles containing MUC1 CAR. PEI and lipofectamine with the amount of 73.72 and 72.53%, respectively, showed the highest transfection rates with respect to calcium phosphate (14.13%) for producing lentiviral particles. However, the cytotoxicity of transfection methods was not significantly different. Based on the results, spinoculation + retronectin leads to the highest transduction rates of T cells (63.19 ± 4.45%) relative to spinoculation + polybrene (34.6 ± 4.44%), polybrene (10.23 ± 0.79%), retronectin (10.37 ± 1.85%), and spinoculation (21.11 ± 1.55%). Further, the polybrene (40.02%) and spinoculation + polybrene (48.83% ± 4.83) increased cytotoxicity significantly compared to other groups.

Conclusion

Improving transduction conditions such as using spinoculation with retronectin can ameliorate the production of CAR-T cells by increasing the rate of transduction, as well as the success rate of treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00397-z.

CAR-T cell therapy in T-cell malignancies: Is success a low-hanging fruit?

Chimeric antigen receptor T-cell (CAR-T) therapy has been prosperous in the treatment of patients with various types of relapsed/refractory (R/R) B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), B-cell acute lymphoblastic leukemia (B-ALL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and multiple myeloma (MM). However, this type of therapy has faced serious hindrances in combating T-cell neoplasms. R/R T-cell malignancies are generally associated with poor clinical outcomes, and the available effective treatment approaches are very limited. CAR-T therapy of T-cell malignancies has unique impediments in comparison with that of B-cell malignancies. Fratricide, T-cell aplasia, and product contamination with malignant T cells when producing autologous CAR-Ts are the most important challenges of CAR-T therapy in T-cell malignancies necessitating in-depth investigations. Herein, we highlight the preclinical and clinical efforts made for addressing these drawbacks and also review additional potent stratagems that could improve CAR-T therapy in T-cell malignancies.

Characterization of the Therapeutic Effects of Novel Chimeric Antigen Receptor T Cells Targeting CD38 on Multiple Myeloma

Multiple myeloma (MM) is a tumor type characterized by the unregulated proliferation of clonal plasma cells in the bone marrow. Immunotherapy based on chimeric antigen receptor T cell (CAR-T) therapy has achieved exciting success in the treatment of hematological malignant tumors. CD38 is highly and evenly expressed in MM and is an attractive target for MM treatment. Here, we successfully constructed two novel second-generation CAR-T cells targeting CD38 by retroviral vector transduction. CD38 CAR-T cells could be activated effectively after stimulation with CD38-positive tumor cells and secrete cytokines such as IFN-γ and TNF-α to promote tumor cell apoptosis in in vitro experiments. Real-time fluorescence monitoring experiments, luciferase detection experiments and flow cytometry experiments revealed the efficient and specific killing abilities of CD38 CAR-T cells against CD38-positive tumor cells. The proliferation ability of CD38 CAR-T cells in vitro was higher than that of untransduced T cells. Further antitumor experiments in vivo showed that CD38 CAR-T cells could be quickly activated to secrete IFN-γ and eliminate tumors. Thus, novel CD38-targeted second-generation CAR-T cells have efficient and specific antitumor activity and may become a novel therapy for the clinical treatment of MM.

Fully human antibody VH domains to generate mono and bispecific CAR to target solid tumors

BACKGROUND

Chimeric antigen receptor (CAR) T cells are effective in B-cell malignancies. However, heterogeneous antigen expression and antigen loss remain important limitations of targeted immunotherapy in solid tumors. Therefore, targeting multiple tumor-associated antigens simultaneously is expected to improve the outcome of CAR-T cell therapies. Due to the instability of single-chain variable fragments, it remains challenging to develop the simultaneous targeting of multiple antigens using traditional single-chain fragment variable (scFv)-based CARs.

METHODS

We used Humabody VH domains derived from a transgenic mouse to obtain fully human prostate-specific membrane antigen (PSMA) VH and mesothelin (MSLN) VH sequences and redirect T cell with VH based-CAR. The antitumor activity and mode of action of PSMA VH and MSLN VH were evaluated in vitro and in vivo compared with the traditional scFv-based CARs.

RESULTS

Human VH domain-based CAR targeting PSMA and MSLN are stable and functional both in vitro and in vivo. VH modules in the bispecific format are capable of binding their specific target with similar affinity as their monovalent counterparts. Bispecific CARs generated by joining two human antibody VH domains can prevent tumor escape in tumor with heterogeneous antigen expression.

CONCLUSIONS

Fully human antibody VH domains can be used to generate functional CAR molecules, and redirected T cells elicit antitumoral responses in solid tumors at least as well as conventional scFv-based CARs. In addition, VH domains can be used to generate bispecific CAR-T cells to simultaneously target two different antigens expressed by tumor cells, and therefore, achieve better tumor control in solid tumors.

Strategies for Dodging the Obstacles in CAR T Cell Therapy

Chimeric antigen receptor (CAR) T cell therapy has offered cancer patients a new alternative therapeutic choice in recent years. This novel type of therapy holds tremendous promise for the treatment of various hematologic malignancies including B-cell acute lymphoblastic leukemia (B-ALL) and lymphoma. However, CAR T cell therapy has experienced its ups and downs in terms of toxicities and efficacy shortcomings. Adverse events such as cytokine release syndrome (CRS), neurotoxicity, graft rejection, on-target off-tumor toxicities, and tumor relapse have tied the rescuing hands of CAR T cell therapies. Moreover, in the case of solid tumor treatment, CAR T cell therapies have not yielded encouraging results mainly due to challenges such as the formidable network of the tumor microenvironments (TME) that operates in a suppressive fashion resulting in CAR T cell dysfunction. In this review, we tend to shine a light on emerging strategies and solutions for addressing the mentioned barriers. These solutions might dramatically help shorten the gap between a successful clinical outcome and the hope for it.

Recent advances and discoveries in the mechanisms and functions of CAR T cells

This Review discusses the major advances and changes made over the past 3 years to our understanding of chimeric antigen receptor (CAR) T cell efficacy and safety. Recently, the field has gained insight into how various molecular modules of the CAR influence signalling and function. We report on mechanisms of toxicity and resistance as well as novel engineering and pharmaceutical interventions to overcome these challenges. Looking forward, we discuss new targets and indications for CAR T cell therapy expected to reach the clinic in the next 1-2 years. We also consider some new studies that have implications for the future of CAR T cell therapies, including changes to manufacturing, allogeneic products and drug-regulatable CAR T cells.

Strategies for having a more effective and less toxic CAR T-cell therapy for acute lymphoblastic leukemia

In the recent years, using genetically modified T cells has been known as a rapid developing therapeutic approach due to the heartwarming results of clinical trials with patients suffering from relapsed or refractory (R/R) hematologic malignancies such as R/R Acute Lymphoblastic Leukemia (R/R ALL). One of these renowned approaches is Chimeric antigen receptors (CARs). CARs are synthetic receptors with the ability to be expressed on the surface of T lymphocytes and are specifically designed to target a tumor-associated antigen (TAA) of interest. CAR-expressing T cells have the capability of proliferating and maintaining their immunological functionality in the recipient body but like any other therapeutic approach, the safety, effectiveness, and specificity enhancement of CAR T cells still lingers in the ambiguity arena. Genetic manipulation methods, expansion protocols, infusion dosage, and conditioning regimens are all among crucial factors which can affect the efficacy of CAR T cell-based cancer therapy. In this article, we discuss the studies that have focused on various aspects that affect the efficacy and persistence of CAR T-cell therapy for ALL treatment and provide a widespread overview regarding the practical approaches capable of elevating the effectiveness and lessening the relative toxicities attributed to it.