CAR T Cell Therapy for Solid Tumors: Bright Future or Dark Reality?

Locoregional delivery of CAR-T cells in the clinic

Cellular therapies utilizing T cells expressing chimeric antigen receptors (CARs) have garnered significant interest due to their clinical success in hematological malignancies. Unfortunately, this success has not been replicated in solid tumors, with only a small fraction of patients achieving complete responses. A number of obstacles to effective CAR-T cell therapy in solid tumors have been identified including tumor antigen heterogeneity, poor T cell fitness and persistence, inefficient trafficking and inability to penetrate into the tumor, immune-related adverse events due to on-target/off-tumor toxicity, and the immunosuppressive tumor microenvironment. Many preclinical studies have focused on improvements to CAR design to try to overcome some of these hurdles. However, a growing body of work has also focused on the use of local and/or regional delivery of CAR-T cells as a means to overcome poor T cell trafficking and inefficient T cell penetration into tumors. Most trials that incorporate locoregional delivery of CAR-T cells have targeted tumors of the central nervous system - repurposing an Ommaya/Rickham reservoir for repeated delivery of cells directly to the tumor cavity or ventricles. Hepatic artery infusion is another technique used for locoregional delivery to hepatic tumors. Locoregional delivery theoretically permits increased numbers of CAR-T cells within the tumor while reducing the risk of immune-related systemic toxicity. Studies to date have been almost exclusively phase I. The growing body of evidence indicates that locoregional delivery of CAR-T cells is both safe and feasible. This review focuses specifically on the use of locoregional delivery of CAR-T cells in clinical trials.

Novel CD19 chimeric antigen receptor T cells manufactured next-day for acute lymphoblastic leukemia

Chimeric antigen receptor-engineered T (CAR-T) cells have shown promising efficacy in patients with relapsed/refractory B cell acute lymphoblastic leukemia (R/R B-ALL). However, challenges remain including long manufacturing processes that need to be overcome. We presented the CD19-targeting CAR-T cell product GC007F manufactured next-day (FasTCAR-T cells) and administered to patients with R/R B-ALL. A total of 21 patients over 14 years of age with CD19⁺  R/R B-ALL were screened, enrolled and infused with a single infusion of GC007F CAR-T at three different dose levels. The primary objective of the study was to assess safety, secondary objectives included pharmacokinetics of GC007F cells in patients with R/R B-ALL and preliminary efficacy. We were able to demonstrate in preclinical studies that GC007F cells exhibited better proliferation and tumor killing than conventional CAR-T (C-CAR-T) cells. In this investigator-initiated study all 18 efficacy-evaluable patients achieved a complete remission (CR) (18/18, 100.00%) by day 28, with 17 of the patients (94.4%) achieving CR with minimal residual disease (MRD) negative. Fifteen (83.3%) remained disease free at the 3-month assessment, 14 patients (77.8%) maintaining MRD negative at month 3. Among all 21 enrolled patients, the median peak of CAR-T cell was on day 10, with a median peak copy number of 104899.5/µg DNA and a median persistence period of 56 days (range: 7–327 days). The incidence of cytokine release syndrome (CRS) was 95.2% (n = 20), with severe CRS occurring in 52.4% (n = 11) of the patients. Six patients (28.6%) developed neurotoxicity of any grade. GC007F demonstrated superior expansion capacity and a less exhausted phenotype as compared to (C-CAR-T) cells. Moreover, this first-in-human clinical study showed that the novel, next-day manufacturing FasTCAR-T cells was feasible with a manageable toxicity profile in patients with R/R B-ALL.

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.

CAR T cell therapy for solid tumors: Fatal attraction requires adhesion

Chimeric antigen receptor (CAR) T cell therapy has shown limited efficacy against solid tumors in clinical studies in contrast to hematological malignancies. In a paper recently published in Nature, Larson et al. report that CAR T cell activity against solid tumors depends on cell adhesion mediated by IFNγ signaling, opening the prospect of improving their clinical activity in the future.

Biomimetic Nanocarriers Guide Extracellular ATP Homeostasis to Remodel Energy Metabolism for Activating Innate and Adaptive Immunity System

Metabolic interventions via targeting intratumoral dysregulated metabolism pathways have shown promise in reinvigorating antitumor immunity. However, approved small molecule immunomodulators often suffer from ineffective response rates and severe off-target toxicity. ATP occupies a crucial role in energy metabolism of components that form the tumor microenvironment (TME) and influences cancer immunosurveillance. Here, a nanocarrier-assisted immunometabolic therapy strategy that targets the ATP-adenosine axis for metabolic reprogramming of TME is reported. An ecto-enzyme (CD39) antagonist POM1 and AMP-activated protein kinase (AMPK) agonist metformin are both encapsulated into cancer cell-derived exosomes and used as nanocarriers for tumor targeting delivery. This method increases the level of pro-inflammatory extracellular ATP (eATP) while preventing the accumulation of immunosuppressive adenosine and alleviating hypoxia. Elevated eATP triggers the activation of P2X7-NLRP3-inflammasome to drive macrophage pyroptosis, potentiates the maturation and antigen capacity of dendritic cells (DCs) to enhance the cytotoxic function of T cells and natural killer (NK) cells. As a result, synergistic antitumor immune responses are initiated to suppress tumor progress, inhibit tumor distant metastases, provide long-term immune memory that offers protection against tumor recurrence and overcome anti-PD1 resistance. Overall, this study provides an innovative strategy to advance eATP-driven antitumor immunity in cancer therapy.

Understanding Tricky Cellular and Molecular Interactions in Pancreatic Tumor Microenvironment: New Food for Thought

Pancreatic ductal adenocarcinoma (PDAC) represents 90% of all pancreatic cancer cases and shows a high mortality rate among all solid tumors. PDAC is often associated with poor prognosis, due to the late diagnosis that leads to metastasis development, and limited efficacy of available treatments. The tumor microenvironment (TME) represents a reliable source of novel targets for therapy, and even if many of the biological interactions among stromal, immune, and cancer cells that populate the TME have been studied, much more needs to be clarified. The great limitation in the efficacy of current standard chemoterapy is due to both the dense fibrotic inaccessible TME barrier surrounding cancer cells and the immunological evolution from a tumor-suppressor to an immunosuppressive environment. Nevertheless, combinatorial therapies may prove more effective at overcoming resistance mechanisms and achieving tumor cell killing. To achieve this result, a deeper understanding of the pathological mechanisms driving tumor progression and immune escape is required in order to design rationale-based therapeutic strategies. This review aims to summarize the present knowledge about cellular interactions in the TME, with much attention on immunosuppressive functioning and a specific focus on extracellular matrix (ECM) contribution.

Bioorthogonal Equipping CAR-T Cells with Hyaluronidase and Checkpoint Blocking Antibody for Enhanced Solid Tumor Immunotherapy

Adoptive cellular therapy utilizing chimeric antigen receptor redirected T (CAR-T) cells has shown impressive therapeutic effects on hematological malignancies. In contrast, the efficacy of CAR-T therapies in treating solid tumors is still poor, which is largely due to inefficient penetration into solid tumors and the immunosuppressive tumor microenvironment. Herein, we engineered hyaluronidase (HAase) and the checkpoint blocking antibody α-PDL1 on the CAR-T cell surface via highly efficient and biocompatible bioorthogonal click chemistry to improve their therapeutic effects on solid tumors. The modified HAase degrades hyaluronic acid and destroys the tumor extracellular matrix, allowing CAR-T cells to penetrate deeply into solid tumors, as evidenced by in vitro infiltration experiments and in vivo biodistribution studies. In addition, in vitro cytotoxicity studies showed stronger antitumor activity of α-PDL1-decorated cells than traditional CAR-T cells. Importantly, HAase- and α-PDL1-engineered CAR-T cells showed better therapeutic efficacy on two solid tumor models and did not cause significant systemic side effects. In this work, we provide a simple, efficient, and biologically safe chemical strategy to engineer traditional CAR-T cells for enhanced therapeutic efficacy on solid tumors, which can be extended to other adoptive cellular immunotherapies and holds great potential for clinical application.

Adoptive Cell Therapy in Pediatric and Young Adult Solid Tumors: Current Status and Future Directions

Advances from novel adoptive cellular therapies have yet to be fully realized for the treatment of children and young adults with solid tumors. This review discusses the strategies and preliminary results, including T-cell, NK-cell and myeloid cell-based therapies. While each of these approaches have shown some early promise, there remain challenges. These include poor trafficking to the tumor as well as a hostile tumor microenvironment with numerous immunosuppressive mechanisms which result in exhaustion of cellular therapies. We then turn our attention to new strategies proposed to address these challenges including novel clinical trials that are ongoing and in development.

Bibliometric Analysis of Chimeric Antigen Receptor-Based Immunotherapy in Cancers From 2001 to 2021

Background

Chimeric antigen receptor (CAR)-based immunotherapy has shown great potential for the treatment of both hematopoietic malignancies and solid tumors. Nevertheless, multiple obstacles still block the development of CAR-based immunotherapy in the clinical setting. In this study, we aimed to summarize the research landscape and highlight the front lines and trends of this field.

Methods

Literature published from 2001 to 2021 was searched in the Web of Science Core Collection database. Full records and cited references of all the documents were extracted and screened. Bibliometric analysis and visualization were conducted using CiteSpace, Microsoft Excel 2019, VOSviewer and R software.

Results

A total of 5981 articles and reviews were included. The publication and citation results exhibited increasing trends in the last 20 years. Frontiers in Immunology and Blood were the most productive and most co-cited journals, respectively. The United States was the country with the most productive organizations and publications in the comprehensive worldwide cooperation network, followed by China and Germany. June, C.H. published the most papers with the most citations, while Maude, S.L. ranked first among the co-cited authors. The hotspots in CAR-based therapy research were multiple myeloma, safety and toxicity, solid tumors, CAR-engineered immune cells beyond T cells, and gene editing.

Conclusion

CAR-based immunotherapy is a promising treatment for cancer patients, and there is an emerging movement toward using advanced gene modification technologies to overcome therapeutic challenges, especially in solid tumors, and to generate safer and more effective universal CAR-engineered cell products.

T-cell mediated targeted delivery of anti-PD-L1 nanobody overcomes poor antibody penetration and improves PD-L1 blocking at the tumor site

Monoclonal antibodies blocking immune checkpoints such as PD-L1 have yielded strong clinical benefits in many cancer types. Still, the current limitations are the lack of clinical response in a majority of patients and the development of immune-related adverse events in some. As an alternative to PD-L1-specific antibody injection, we have developed an approach based on the engineering of tumor-targeting T cells to deliver intratumorally an anti-PD-L1 nanobody. In the MC38-OVA model, our strategy enhanced tumor control as compared to injection of PD-L1-specific antibody combined with adoptive transfer of tumor-targeting T cells. As a possible explanation for this, we demonstrated that PD-L1-specific antibody massively occupied PD-L1 in the periphery but failed to penetrate to PD-L1-expressing cells at the tumor site. In sharp contrast, locally delivered anti-PD-L1 nanobody improved PD-L1 blocking at the tumor site while avoiding systemic exposure. Our approach appears promising to overcome the limitations of immunotherapy based on PD-L1-specific antibody treatment.

Oncolytic virus-mediated expansion of dual-specific CAR T cells improves efficacy against solid tumors in mice

Oncolytic viruses (OVs) encoding a variety of transgenes have been evaluated as therapeutic tools to increase the efficacy of chimeric antigen receptor (CAR)-modified T cells in the solid tumor microenvironment (TME). Here, using systemically delivered OVs and CAR T cells in immunocompetent mouse models, we have defined a mechanism by which OVs can potentiate CAR T cell efficacy against solid tumor models of melanoma and glioma. We show that stimulation of the native T cell receptor (TCR) with viral or virally encoded epitopes gives rise to enhanced proliferation, CAR-directed antitumor function, and distinct memory phenotypes. In vivo expansion of dual-specific (DS) CAR T cells was leveraged by in vitro preloading with oncolytic vesicular stomatitis virus (VSV) or reovirus, allowing for a further in vivo expansion and reactivation of T cells by homologous boosting. This treatment led to prolonged survival of mice with subcutaneous melanoma and intracranial glioma tumors. Human CD19 CAR T cells could also be expanded in vitro with TCR reactivity against viral or virally encoded antigens and was associated with greater CAR-directed cytokine production. Our data highlight the utility of combining OV and CAR T cell therapy and show that stimulation of the native TCR can be exploited to enhance CAR T cell activity and efficacy in mice.

Development of CAR T Cell Therapy in Children-A Comprehensive Overview

CAR T cell therapy has revolutionized immunotherapy in the last decade with the successful establishment of chimeric antigen receptor (CAR)-expressing cellular therapies as an alternative treatment in relapsed and refractory CD19-positive leukemias and lymphomas. There are fundamental reasons why CAR T cell therapy has been approved by the Food and Drug administration and the European Medicines Agency for pediatric and young adult patients first. Commonly, novel therapies are developed for adult patients and then adapted for pediatric use, due to regulatory and commercial reasons. Both strategic and biological factors have supported the success of CAR T cell therapy in children. Since there is an urgent need for more potent and specific therapies in childhood malignancies, efforts should also include the development of CAR therapeutics and expand applicability by introducing new technologies. Basic aspects, the evolution and the drawbacks of childhood CAR T cell therapy are discussed as along with the latest clinically relevant information.

Does the Microbiota Composition Influence the Efficacy of Colorectal Cancer Immunotherapy?

Colorectal cancer (CRC) is the second most common malignancy globally, and many people with CRC suffer the fate of death. Due to the importance of CRC and its negative impact on communities, treatment strategies to control it or increase patient survival are being studied. Traditional therapies, including surgery and chemotherapy, have treated CRC patients. However, with the advancement of science, we are witnessing the emergence of novel therapeutic approaches such as immunotherapy for CRC treatment, which have had relatively satisfactory clinical outcomes. Evidence shows that gastrointestinal (GI) microbiota, including various bacterial species, viruses, and fungi, can affect various biological events, regulate the immune system, and even treat diseases like human malignancies. CRC has recently shown that the gut microorganism pattern can alter both antitumor and pro-tumor responses, as well as cancer immunotherapy. Of course, this is also true of traditional therapies because it has been revealed that gut microbiota can also reduce the side effects of chemotherapy. Therefore, this review summarized the effects of gut microbiota on CRC immunotherapy.

Loss of H3K27 trimethylation promotes radiotherapy resistance in medulloblastoma and induces an actionable vulnerability to BET inhibition

Medulloblastoma has been categorized into four subgroups based on genetic, epigenetic, and transcriptional profiling. Radiation is used for treating medulloblastoma regardless of the subgroup. A better understanding of the molecular pathways determining radiotherapy response could help improve medulloblastoma treatment. Here, we investigated the role of the EZH2-dependent histone H3K27 trimethylation in radiotherapy response in medulloblastoma. The tumors in 47.2% of group 3 and 4 medulloblastoma patients displayed H3K27me3 deficiency. Loss of H3K27me3 was associated with a radioresistant phenotype, high relapse rates, and poor overall survival. In H3K27me3-deficient medulloblastoma cells, an epigenetic switch from H3K27me3 to H3K27ac occurred at specific genomic loci, altering the transcriptional profile. The resulting upregulation of EPHA2 stimulated excessive activation of the pro-survival AKT signaling pathway, leading to radiotherapy resistance. BET inhibition overcame radiation resistance in H3K27me3-deficient medulloblastoma cells by suppressing H3K27ac levels, blunting EPHA2 overexpression, and mitigating excessive AKT signaling. Additionally, BET inhibition sensitized medulloblastoma cells to radiation by enhancing the apoptotic response through suppression of Bcl-xL and upregulation of Bim. This work demonstrates a novel mechanism of radiation resistance in medulloblastoma and identifies an epigenetic marker predictive of radiotherapy response. Based on these findings, we propose an epigenetically guided treatment approach targeting radiotherapy resistance in medulloblastoma patients.

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.

Cancer Therapy With TCR-Engineered T Cells: Current Strategies, Challenges, and Prospects

To redirect T cells against tumor cells, T cells can be engineered ex vivo to express cancer-antigen specific T cell receptors (TCRs), generating products known as TCR-engineered T cells (TCR T). Unlike chimeric antigen receptors (CARs), TCRs recognize HLA-presented peptides derived from proteins of all cellular compartments. The use of TCR T cells for adoptive cellular therapies (ACT) has gained increased attention, especially as efforts to treat solid cancers with ACTs have intensified. In this review, we describe the differing mechanisms of T cell antigen recognition and signal transduction mediated through CARs and TCRs. We describe the classes of cancer antigens recognized by current TCR T therapies and discuss both classical and emerging pre-clinical strategies for antigen-specific TCR discovery, enhancement, and validation. Finally, we review the current landscape of clinical trials for TCR T therapy and discuss what these current results indicate for the development of future engineered TCR approaches.

In-Vivo Induced CAR-T Cell for the Potential Breakthrough to Overcome the Barriers of Current CAR-T Cell Therapy

Chimeric antigen receptor T cell (CAR-T cell) therapy has shown impressive success in the treatment of hematological malignancies, but the systemic toxicity and complex manufacturing process of current autologous CAR-T cell therapy hinder its broader applications. Universal CAR-T cells have been developed to simplify the production process through isolation and editing of allogeneic T cells from healthy persons, but the allogeneic CAR-T cells have recently encountered safety concerns, and clinical trials have been halted by the FDA. Thus, there is an urgent need to seek new ways to overcome the barriers of current CAR-T cell therapy. In-vivo CAR-T cells induced by nanocarriers loaded with CAR-genes and gene-editing tools have shown efficiency for regressing leukemia and reducing systemic toxicity in a mouse model. The in-situ programming of autologous T-cells avoids the safety concerns of allogeneic T cells, and the manufacture of nanocarriers can be easily standardized. Therefore, the in-vivo induced CAR-T cells can potentially overcome the abovementioned limitations of current CAR-T cell therapy. Here, we provide a review on CAR structures, gene-editing tools, and gene delivery techniques applied in immunotherapy to help design and develop new in-vivo induced CAR-T cells.

Targeting of the alphav beta3 integrin complex by CAR-T cells leads to rapid regression of diffuse intrinsic pontine glioma and glioblastoma

Background

Diffuse intrinsic pontine glioma (DIPG) and glioblastoma (GBM) are two highly aggressive and generally incurable gliomas with little therapeutic advancements made in the past several decades. Despite immense initial success of chimeric antigen receptor (CAR) T cells for the treatment of leukemia and lymphoma, significant headway into the application of CAR-T cells against solid tumors, including gliomas, is still forthcoming. The integrin complex alpha_v beta₃ (α_vβ₃) is present on multiple and diverse solid tumor types and tumor vasculature with limited expression throughout most normal tissues, qualifying it as an appealing target for CAR-T cell-mediated immunotherapy.

Methods

Patient-derived DIPG and GBM cell lines were evaluated by flow cytometry for surface expression of α_vβ₃. Second-generation CAR-T cells expressing an anti-α_vβ₃ single-chain variable fragment were generated by retroviral transduction containing either a CD28 or 4-1BB costimulatory domain and CD3zeta. CAR-T cells were evaluated by flow cytometry for CAR expression, memory phenotype distribution, and inhibitory receptor profile. DIPG and GBM cell lines were orthotopically implanted into NSG mice via stereotactic injection and monitored with bioluminescent imaging to evaluate α_vβ₃ CAR-T cell-mediated antitumor responses.

Results

We found that patient-derived DIPG cells and GBM cell lines express high levels of surface α_vβ₃ by flow cytometry, while α_vβ₃ is minimally expressed on normal tissues by RNA sequencing and protein microarray. The manufactured CAR-T cells consisted of a substantial frequency of favorable early memory cells and a low inhibitory receptor profile. α_vβ₃ CAR-T cells demonstrated efficient, antigen-specific tumor cell killing in both cytotoxicity assays and in in vivo models of orthotopically and stereotactically implanted DIPG and GBM tumors into relevant locations in the brain of NSG mice. Tumor responses were rapid and robust with systemic CAR-T cell proliferation and long-lived persistence associated with long-term survival. Following tumor clearance, TCF-1⁺α_vβ₃ CAR-T cells were detectable, underscoring their ability to persist and undergo self-renewal.

Conclusions

These results highlight the potential of α_vβ₃ CAR-T cells for immunotherapeutic treatment of aggressive brain tumors with reduced risk of on-target, off-tumor mediated toxicity due to the restricted nature of α_vβ₃ expression in normal tissues.

The Road to CAR T-Cell Therapies for Pediatric CNS Tumors: Obstacles and New Avenues

Pediatric central nervous system (CNS) tumors are the most common solid tumors diagnosed in children and are the leading cause of pediatric cancer-related death. Those who do survive are faced with the long-term adverse effects of the current standard of care treatments of chemotherapy, radiation, and surgery. There is a pressing need for novel therapeutic strategies to treat pediatric CNS tumors more effectively while reducing toxicity - one of these novel modalities is chimeric antigen receptor (CAR) T-cell therapy. Currently approved for use in several hematological malignancies, there are promising pre-clinical and early clinical data that suggest CAR-T cells could transform the treatment of pediatric CNS tumors. There are, however, several challenges that must be overcome to develop safe and effective CAR T-cell therapies for CNS tumors. Herein, we detail these challenges, focusing on those unique to pediatric patients including antigen selection, tumor immunogenicity and toxicity. We also discuss our perspective on future avenues for CAR T-cell therapies and potential combinatorial treatment approaches.

Current Status of CRISPR/Cas9 Application in Clinical Cancer Research: Opportunities and Challenges

Cancer is considered by not only multiple genetic but also epigenetic amendments that drive malignant cell propagation and consult chemo-resistance. The ability to correct or ablate such mutations holds enormous promise for battling cancer. Recently, because of its great efficiency and feasibility, the CRISPR-Cas9 advanced genome editing technique has been extensively considered for therapeutic investigations of cancers. Several studies have used the CRISPR-Cas9 technique for editing cancer cell genomic DNA in cells and animal cancer models and have shown therapeutic potential in intensifying anti-cancer protocols. Moreover, CRISPR-Cas9 may be used to correct oncogenic mutations, discover anticancer drugs, and engineer immune cells and oncolytic viruses for immunotherapeutic treatment of cancer. We herein discuss the challenges and opportunities for translating therapeutic methods with CRISPR-Cas9 for clinical use and suggest potential directions of the CRISPR-Cas9 system for future cancer therapy.

T-SIGn tumor reengineering therapy and CAR T cells synergize in combination therapy to clear human lung tumor xenografts and lung metastases in NSG mice

Although chimeric antigen receptor (CAR) T cells have emerged as highly effective treatments for patients with hematologic malignancies, similar efficacy has not been achieved in the context of solid tumors. There are several reasons for this disparity including a) fewer solid tumor target antigens, b) heterogenous target expression amongst tumor cells, c) poor trafficking of CAR T cells to the solid tumor and d) an immunosuppressive tumor microenvironment (TME). Oncolytic viruses have the potential to change this paradigm by a) directly lysing tumor cells and releasing tumor neoantigens, b) stimulating the local host innate immune response to release cytokines and recruit additional innate and adaptive immune cells, c) carrying virus-encoded transgenes to “re-program” the TME to a pro-inflammatory environment and d) promoting an adaptive immune response to the neoantigens in this newly permissive TME. Here we show that the Tumor-Specific Immuno-Gene (T-SIGn) virus NG-347 which encodes IFNα, MIP1α and CD80 synergizes with anti-EGFR CAR T cells as well as anti-HER-2 CAR T cells to clear A549 human tumor xenografts and their pulmonary metastases at doses which are subtherapeutic when each is used as a sole treatment. We show that NG-347 changes the TME to a pro-inflammatory environment resulting in the recruitment and activation of both CAR T cells and mouse innate immune cells. We also show that the transgenes encoded by the virus are critical as synergy is lost in their absence.

Advances in CAR-T Cell Genetic Engineering Strategies to Overcome Hurdles in Solid Tumors Treatment

During this last decade, adoptive transfer of T lymphocytes genetically modified to express chimeric antigen receptors (CARs) emerged as a valuable therapeutic strategy in hematological cancers. However, this immunotherapy has demonstrated limited efficacy in solid tumors. The main obstacle encountered by CAR-T cells in solid malignancies is the immunosuppressive tumor microenvironment (TME). The TME impedes tumor trafficking and penetration of T lymphocytes and installs an immunosuppressive milieu by producing suppressive soluble factors and by overexpressing negative immune checkpoints. In order to overcome these hurdles, new CAR-T cells engineering strategies were designed, to potentiate tumor recognition and infiltration and anti-cancer activity in the hostile TME. In this review, we provide an overview of the major mechanisms used by tumor cells to evade immune defenses and we critically expose the most optimistic engineering strategies to make CAR-T cell therapy a solid option for solid tumors.

Better by design: What to expect from novel CAR-engineered cell therapies?

Chimeric antigen receptor (CAR) technology, and CAR-T cells in particular, have emerged as a new and powerful tool in cancer immunotherapy since demonstrating efficacy against several hematological malignancies. However, despite encouraging clinical results of CAR-T cell therapy products, a significant proportion of patients do not achieve satisfactory responses, or relapse. In addition, CAR-T cell applications to solid tumors is still limited due to the tumor microenvironment and lack of specifically targetable tumor antigens. All current products on the market, as well as most investigational CAR-T cell therapies, are autologous, using the patient's own peripheral blood mononuclear cells as starting material to manufacture a patient-specific batch. Alternative cell sources are, therefore, under investigation (e.g. allogeneic cells from an at least partially human leukocyte antigen (HLA)-matched healthy donor, universal "third-party" cells from a non-HLA-matched donor, cord blood-derived cells, immortalized cell lines or cells differentiated from induced pluripotent stem cells). However, genetic modifications of CAR-engineered cells, bioprocesses used to expand cells, and improved supply chains are still complex and costly. To overcome drawbacks associated with CAR-T technologies, novel CAR designs have been used to genetically engineer cells derived from alpha beta (αβ) T cells, other immune cells such as natural killer (NK) cells, gamma delta (γδ) T cells, macrophages or dendritic cells. This review endeavours to trigger ideas on the next generation of CAR-engineered cell therapies beyond CAR-T cells and, thus, will enable effective, safe and affordable therapies for clinical management of cancer. To achieve this, we present a multidisciplinary overview, addressing a wide range of critical aspects: CAR design, development and manufacturing technologies, pharmacological concepts and clinical applications of CAR-engineered cell therapies. Each of these fields employs a large number of ground-breaking scientific advances, where coordinated and complex process and product development occur at their interfaces.

Overcoming tumor heterogeneity by ex vivo arming of T cells using multiple bispecific antibodies

BACKGROUND

Tumorous heterogeneity is a hallmark of tumor evolution and cancer progression, being a longstanding challenge to targeted immunotherapy. Ex vivo armed T cells (EATs) using IgG-(L)-scFv bispecific antibodies (BsAbs) are potent tumor-specific cytotoxic effectors. To improve the anti-tumor efficacy of EATs against heterogeneous solid tumors, we explored multi-antigen targeting approaches.

METHODS

Ex vivo expanded T cells were armed with BsAbs built on the IgG-(L)-scFv platform, where an anti-CD3 (huOKT3) scFv was attached to the carboxyl end of both light chains of a tumor specific IgG. Multispecificity was created by combining monospecific EATs, combining BsAbs on the same T cell, or combining specificities on the same antibody. Three multi-antigens targeting EAT strategies were tested: (1) pooled-EATs (EATs each with unique specificity administered simultaneously) or alternate-EATs (EATs each with unique specificity administered in an alternating schedule), (2) dual-EATs or multi-EATs (T cells simultaneously armed with ≥2 BsAbs), and (3) TriAb-EATs (T cells armed with BsAb specific for two targets besides CD3 (TriAb)). The properties and efficiencies of these three strategies were evaluated by flow cytometry, in vitro cytotoxicity, cytokine release assays, and in vivo studies performed in BALB-Rag2 ^-/-IL-2R-γc-KO (BRG) mice xenografted with cancer cell line (CDX) or patient-derived tumor (PDX).

RESULTS

Multi-EATs retained target antigen specificity and anti-tumor potency. Cytokine release with multi-EATs in the presence of tumor cells was substantially less than when multiple BsAbs were mixed with unarmed T cells. When tested against CDXs or PDXs, dual-EATs or multi-EATs effectively suppressed tumor growth without clinical toxicities. Most importantly, dual-EATs or multi-EATs were highly efficient in preventing clonal escape while mono-EATs or TriAb- EATs were not as effective.

CONCLUSIONS

Multi-EATs have the potential to increase potency, reduce toxicity, and overcome tumor heterogeneity without excessive cytokine release. Arming T cells with multiple BsAbs deserves further exploration to prevent or to treat cancer resistance.

Chimeric Antigen Receptor T-Cell Therapy in Metastatic Castrate-Resistant Prostate Cancer

Simple Summary

Prostate cancer is one of the most frequently diagnosed cancers amongst men worldwide. Treatment for metastatic disease is often in the form of androgen deprivation therapy. However, over the course of treatment affected men may become castrate-resistant. Options for men with metastatic castrate-resistant cancer are limited. This review focuses on the role of chimeric antigen receptor T-cell therapy (CAR-T) in men with metastatic castrate-resistant prostate cancer. This review is a contemporary appraisal of preclinical and clinical studies conducted in this emerging form of immunotherapy. A thorough evaluation of the role of CAR-T therapy in prostate cancer is provided, as well as the obstacles we must overcome to clinically translate this therapy for men affected with this rapidly fatal disease.

Abstract

Prostate cancer is the most commonly diagnosed solid-organ cancer amongst males worldwide. Metastatic castrate-resistant prostate cancer (mCRPC) is a rapidly fatal end-sequelae of prostate cancer. Therapeutic options for men with mCRPC are limited and are not curative in nature. The recent development of chimeric antigen receptor T-cell (CAR-T) therapy has revolutionised the treatment of treatment-resistant haematological malignancies, and several studies are underway investigating the utility of this technology in the treatment of solid tumours. In this review, we evaluate the current treatment options for men with mCRPC as well as the current landscape of preclinical and clinical trials of CAR-T cell therapy against prostate cancer. We also appraise the various prostate cancer-specific tumour-associated antigens that may be targeted by CAR-T cell technology. Finally, we examine the potential translational barriers of CAR-T cell therapy in solid tumours. Despite preclinical success, preliminary clinical trials in men with prostate cancer have had limited efficacy. Therefore, further clinically translatable preclinical models are required to enhance the understanding of the role of this investigational therapeutic in men with mCRPC. In the era of precision medicine, tailored immunotherapy administered to men in a tumour-agnostic approach provides hope to a group of men who otherwise have few treatment options available.

Vectorized Treg-depleting αCTLA-4 elicits antigen cross-presentation and CD8+ T cell immunity to reject ‘cold’ tumors

Background

Immune checkpoint blockade (ICB) is a clinically proven concept to treat cancer. Still, a majority of patients with cancer including those with poorly immune infiltrated ‘cold’ tumors are resistant to currently available ICB therapies. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of few clinically validated targets for ICB, but toxicities linked to efficacy in approved αCTLA-4 regimens have restricted their use and precluded full therapeutic dosing. At a mechanistic level, accumulating preclinical and clinical data indicate dual mechanisms for αCTLA-4; ICB and regulatory T cell (Treg) depletion are both thought to contribute efficacy and toxicity in available, systemic, αCTLA-4 regimens. Accordingly, strategies to deliver highly effective, yet safe αCTLA-4 therapies have been lacking. Here we assess and identify spatially restricted exposure to a novel strongly Treg-depleting, checkpoint-blocking, vectorized αCTLA-4, as a highly efficacious and potentially safe strategy to target CTLA-4.

Methods

A novel human IgG1 CTLA-4 antibody (4-E03) was identified using function-first screening for monoclonal antibodies (mAbs) and targets associated with superior Treg-depleting activity. A tumor-selective oncolytic vaccinia vector was then engineered to encode this novel, strongly Treg-depleting, checkpoint-blocking, αCTLA-4 antibody or a matching surrogate antibody, and Granulocyte-macrophage colony-stimulating factor (GM-CSF) (VVGM-αCTLA-4).

Results

The identified 4-E03 antibody showed significantly stronger Treg depletion, but equipotent checkpoint blockade, compared with clinically validated αCTLA-4 ipilimumab against CTLA-4-expressing Treg cells in a humanized mouse model in vivo. Intratumoral administration of VVGM-αCTLA-4 achieved tumor-restricted CTLA-4 receptor saturation and Treg depletion, which elicited antigen cross-presentation and stronger systemic expansion of tumor-specific CD8+ T cells and antitumor immunity compared with systemic αCTLA-4 antibody therapy. Efficacy correlated with FcγR-mediated intratumoral Treg depletion. Remarkably, in a clinically relevant mouse model resistant to systemic ICB, intratumoral VVGM-αCTLA-4 synergized with αPD-1 to reject cold tumors.

Conclusion

Our findings demonstrate in vivo proof of concept for spatial restriction of Treg depletion-optimized immune checkpoint blocking, vectorized αCTLA-4 as a highly effective and safe strategy to target CTLA-4. A clinical trial evaluating intratumoral VVGM-αhCTLA-4 (BT-001) alone and in combination with αPD-1 in metastatic or advanced solid tumors has commenced.

Targeting the undruggable oncogenic KRAS: the dawn of hope

KRAS mutations are the drivers of various cancers, including non-small cell lung cancer, colon cancer, and pancreatic cancer. Over the last 30 years, immense efforts have been made to inhibit KRAS mutants and oncogenic KRAS signaling using inhibitors. Recently, specific targeting of KRAS mutants with small molecules revived the hopes for successful therapies for lung, pancreatic, and colorectal cancer patients. Moreover, advances in gene editing, protein engineering, and drug delivery formulations have revolutionized cancer therapy regimens. New therapies aim to improve immune surveillance and enhance antitumor immunity by precisely targeting cancer cells harboring oncogenic KRAS. Here, we review recent KRAS-targeting strategies, their therapeutic potential, and remaining challenges to overcome. We also highlight the potential synergistic effects of various combinatorial therapies in preclinical and clinical trials.

CRISPR/Cas9: A revolutionary genome editing tool for human cancers treatment

Cancer is a genetic disease stemming from genetic and epigenetic mutations and is the second most common cause of death across the globe. Clustered regularly interspaced short palindromic repeats (CRISPR) is an emerging gene-editing tool, acting as a defense system in bacteria and archaea. CRISPR/Cas9 technology holds immense potential in cancer diagnosis and treatment and has been utilized to develop cancer disease models such as medulloblastoma and glioblastoma mice models. In diagnostics, CRISPR can be used to quickly and efficiently detect genes involved in various cancer development, proliferation, metastasis, and drug resistance. CRISPR/Cas9 mediated cancer immunotherapy is a well-known treatment option after surgery, chemotherapy, and radiation therapy. It has marked a turning point in cancer treatment. However, despite its advantages and tremendous potential, there are many challenges such as off-target effects, editing efficiency of CRISPR/Cas9, efficient delivery of CRISPR/Cas9 components into the target cells and tissues, and low efficiency of HDR, which are some of the main issues and need further research and development for completely clinical application of this novel gene editing tool. Here, we present a CRISPR/Cas9 mediated cancer treatment method, its role and applications in various cancer treatments, its challenges, and possible solution to counter these challenges.

Engineered CAR-Macrophages as Adoptive Immunotherapies for Solid Tumors

Cellular immunotherapies represent a promising approach for the treatment of cancer. Engineered adoptive cell therapies redirect and augment a leukocyte’s inherent ability to mount an immune response by introducing novel anti-tumor capabilities and targeting moieties. A prominent example of this approach is the use of T cells engineered to express chimeric antigen receptors (CARs), which have demonstrated significant efficacy against some hematologic malignancies. Despite increasingly sophisticated strategies to harness immune cell function, efficacy against solid tumors has remained elusive for adoptive cell therapies. Amongst cell types used in immunotherapies, however, macrophages have recently emerged as prominent candidates for the treatment of solid tumors. In this review, we discuss the use of monocytes and macrophages as adoptive cell therapies. Macrophages are innate immune cells that are intrinsically equipped with broad therapeutic effector functions, including active trafficking to tumor sites, direct tumor phagocytosis, activation of the tumor microenvironment and professional antigen presentation. We focus on engineering strategies for manipulating macrophages, with a specific focus on CAR macrophages (CAR-M). We highlight CAR design for macrophages, the production of CAR-M for adoptive cell transfer, and clinical considerations for their use in treating solid malignancies. We then outline recent progress and results in applying CAR-M as immunotherapies. The recent development of engineered macrophage-based therapies holds promise as a key weapon in the immune cell therapy armamentarium.

B7-H3 as a Target for CAR-T Cell Therapy in Skull Base Chordoma

Objective

chordomas are rare bone tumors with few therapeutic options. Skull base and sacrum are the two most common origin sites. Immunotherapies are emerging as the most promising approaches to fight various cancers. This study tends to identify new cell surface targets for immunotherapeutic options of skull base chordomas.

Methods

we profiled 45 skull base chordoma clinical samples by immunohistochemistry for the expression of six CAR-Targets (PD-L1, B7-H3, B7-H4, VISTA, HER2 and HER3). In addition, we generated B7-H3 targeted CAR-T-cells and evaluated their antitumor activities in vitro.

Results

We found that B7-H3 was positively stained in 7 out of 45 (16%) chordoma samples and established an expression hierarchy for these antigens (B7-H3 > HER3 > PD-L1 > HER2 = VISTA = B7-H4). We then generated a B7-H3 targeted CAR vector and demonstrated that B7-H3-CAR-T-cells recognized antigen positive cells and exhibited significant antitumor effects, including suppression of tumor spheroid formation, CAR-T-cell activation and cytokine secretion.

Conclusions

Our results support B7-H3 might serve as a promising target for CAR-T-cell therapies against chordomas.

Improvement of mRNA Delivery Efficiency to a T Cell Line by Modulating PEG-Lipid Content and Phospholipid Components of Lipid Nanoparticles

(1) Background: T cells are important target cells, since they exert direct cytotoxic effects on infected/malignant cells, and affect the regulatory functions of other immune cells in a target antigen-specific manner. One of the current approaches for modifying the function of T cells is gene transfection by viral vectors. However, the insertion of the exogenous DNA molecules into the genome is attended by the risk of mutagenesis, especially when a transposon-based gene cassette is used. Based on this scenario, the transient expression of proteins by an in vitro-transcribed messenger RNA (IVT-mRNA) has become a subject of interest. The use of lipid nanoparticles (LNPs) for the transfection of IVT-mRNA is one of the more promising strategies for introducing exogenous genes. In this study, we report on the development of LNPs with transfection efficiencies that are comparable to that for electroporation in a T cell line (Jurkat cells). (2) Methods: Transfection efficiency was improved by optimizing the phospholipids and polyethylene glycol (PEG)-conjugated lipid components. (3) Results: Modification of the lipid composition resulted in the 221-fold increase in luciferase activity compared to a previously optimized formulation. Such a high transfection activity was due to the efficient uptake by clathrin/dynamin-dependent endocytosis and the relatively efficient escape into the cytoplasm at an early stage of endocytosis.

Antigen-Multimers: Specific, Sensitive, Precise, and Multifunctional High-Avidity CAR-Staining Reagents

Although chimeric antigen receptor (CAR) T-cell therapy has transformed cancer treatment, high-quality and universal CAR-staining reagents are urgently required to manufacture CAR T cells, predict therapy response, decipher CAR biology, and engineer new CARs. Here, we developed tetrameric and dodecameric forms of a multifunctional and extensible category of high-avidity CAR-staining reagents: antigen-multimers. Antigen-multimers detected CARs against CD19, HER2, and Tn-glycoside with significantly higher specificity, sensitivity, and precision than existing reagents. In addition to accurate CAR T-cell detection by flow cytometry, antigen-multimers also enabled ≥100-fold magnetic enrichment of rare CAR T cells, selective CAR T-cell stimulation, and high-dimensional CAR T-cell profiling by single-cell multi-omics analyses. Finally, antigen-multimers accurately captured clinical anti-CD19 CAR T cells from patients' cellular infusion products, post-infusion peripheral blood, and tumor biopsies. Antigen-multimers can be readily extended to other CAR systems by switching its antigen ligand. As such, antigen-multimers have broad clinical and research applications.

Hypoxia as a driver of resistance to immunotherapy

Hypoxia, a hallmark of solid tumors, determines the selection of invasive and aggressive malignant clones displaying resistance to radiotherapy, conventional chemotherapy or targeted therapy. The recent introduction of immunotherapy, based on immune checkpoint inhibitors (ICPIs) and chimeric antigen receptor (CAR) T-cells, has markedly transformed the prognosis in some tumors but also revealed the existence of intrinsic or acquired drug resistance. In the current review we highlight hypoxia as a culprit of immunotherapy failure. Indeed, multiple metabolic cross talks between tumor and stromal cells determine the prevalence of immunosuppressive populations within the hypoxic tumor microenvironment and confer upon tumor cells resistance to ICPIs and CAR T-cells. Notably, hypoxia-triggered angiogenesis causes immunosuppression, adding another piece to the puzzle of hypoxia-induced immunoresistance. If these factors concurrently contribute to the resistance to immunotherapy, they also unveil an unexpected Achille's heel of hypoxic tumors, providing the basis for innovative combination therapies that may rescue the efficacy of ICPIs and CAR T-cells. Although these treatments reveal both a bright side and a dark side in terms of efficacy and safety in clinical trials, they represent the future solution to enhance the efficacy of immunotherapy against hypoxic and therapy-resistant solid tumors.

Emerging Approaches for Solid Tumor Treatment Using CAR-T Cell Therapy

Cancer immunotherapy is becoming more important in the clinical setting, especially for cancers resistant to conventional chemotherapy, including targeted therapy. Chimeric antigen receptor (CAR)-T cell therapy, which uses patient’s autologous T cells, combined with engineered T cell receptors, has shown remarkable results, with five US Food and Drug Administration (FDA) approvals to date. CAR-T cells have been very effective in hematologic malignancies, such as diffuse large B cell lymphoma (DLBCL), B cell acute lymphoblastic leukemia (B-ALL), and multiple myeloma (MM); however, its effectiveness in treating solid tumors has not been evaluated clearly. Therefore, many studies and clinical investigations are emerging to improve the CAR-T cell efficacy in solid tumors. The novel therapeutic approaches include modifying CARs in multiple ways or developing a combination therapy with immune checkpoint inhibitors and chemotherapies. In this review, we focus on the challenges and recent advancements in CAR-T cell therapy for solid tumors.

Targeting the immune checkpoint B7-H3 for next-generation cancer immunotherapy

Immune checkpoint inhibitors (ICIs) for programmed death-1 (PD-1) and programmed cell death-ligand 1 (PD-L1) have become preferred treatment strategies for several advanced cancers. However, response rates for these treatments are limited, which encourages the search for new ICI candidates. Recent reports have underscored significant roles of B7 homolog 3 protein (B7-H3) in tumor immunity and disease progression. While its multifaceted roles are being elucidated, B7-H3 has already entered clinical trials as a therapeutic target. In this review, we overview the recent results of clinical trials evaluating the antitumor activity and safety of B7-H3 targeting drugs. On this basis, we also discuss the challenges and opportunities arising from the application of these drugs. Finally, we point out current gaps to address in the understanding of B7-H3 function and regulation in order to fully unleash the future clinical utility of B7-H3-based therapies for the treatment of cancer.

Quantitative contributions of TNF receptor superfamily members to CD8+ T-cell responses

T-cell responses to infections and cancers are regulated by co-signalling receptors grouped into the binary categories of co-stimulation or co-inhibition. The co-stimulation TNF receptor superfamily (TNFRSF) members 4-1BB, CD27, GITR and OX40 have similar signalling mechanisms raising the question of whether they have similar impacts on T-cell responses. Here, we screened for the quantitative impact of these TNFRSFs on primary human CD8+ T-cell cytokine production. Although both 4-1BB and CD27 increased production, only 4-1BB was able to prolong the duration over which cytokine was produced, and both had only modest effects on antigen sensitivity. An operational model explained these different phenotypes using shared signalling based on the surface expression of 4-1BB being regulated through signalling feedback. The model predicted and experiments confirmed that CD27 co-stimulation increases 4-1BB expression and subsequent 4-1BB co-stimulation. GITR and OX40 displayed only minor effects on their own but, like 4-1BB, CD27 could enhance GITR expression and subsequent GITR co-stimulation. Thus, different co-stimulation receptors can have different quantitative effects allowing for synergy and fine-tuning of T-cell responses.

A Systematic Review and Meta-Analysis on the Significance of TIGIT in Solid Cancers: Dual TIGIT/PD-1 Blockade to Overcome Immune-Resistance in Solid Cancers

Preclinical studies have indicated that T-cell immunoglobulin and ITIM domain (TIGIT) can substantially attenuate anti-tumoral immune responses. Although multiple clinical studies have evaluated the significance of TIGIT in patients with solid cancers, their results remain inconclusive. Thus, we conducted the current systematic review and meta-analysis based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) to determine its significance in patients with solid cancers. We systematically searched the Web of Science, Embase, PubMed, and Scopus databases to obtain peer-reviewed studies published before September 20, 2020. Our results have shown that increased TIGIT expression has been significantly associated with inferior overall survival (OS) (HR = 1.42, 95% CI: 1.11–1.82, and p-value = 0.01). Besides, the level of tumor-infiltrating TIGIT⁺CD8⁺ T-cells have been remarkably associated inferior OS and relapse-free survival (RFS) of affected patients (HR = 2.17, 95% CI: 1.43–3.29, and p-value < 0.001, and HR = 1.89, 95% CI: 1.36–2.63, and p-value < 0.001, respectively). Also, there is a strong positive association between TIGIT expression with programmed cell death-1 (PD-1) expression in these patients (OR = 1.71, 95% CI: 1.10–2.68, and p-value = 0.02). In summary, increased TIGIT expression and increased infiltration of TIGIT⁺CD8⁺ T-cells can substantially worsen the prognosis of patients with solid cancers. Besides, concerning the observed strong association between TIGIT and PD-1, ongoing clinical trials, and promising preclinical results, PD-1/TIGIT dual blockade can potentially help overcome the immune-resistance state seen following monotherapy with a single immune checkpoint inhibitor in patients with solid cancers.

Effectiveness of 4-1BB-costimulated HER2-targeted chimeric antigen receptor T cell therapy for synovial sarcoma

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HER2-targeted/4-1BB costimulated CAR T cells recognized synovial sarcoma cells.

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HER2-targeted CAR T cells secrete interferon gamma and tumor necrosis factor alpha.

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HER2-targeted CAR T cells exert cytotoxic effects in synovial sarcoma cells.

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HER2-targeted CAR T cell therapy for chemo-refractory or relapsed synovial sarcoma.

Background

Synovial sarcoma is a rare malignant soft-tissue tumor that is prevalent in adolescents and young adults, and poor prognosis has been reported in patients with metastatic lesions. Chimeric antigen receptor (CAR) T-cell therapy is an emerging novel therapy for solid tumors; however, its application in synovial sarcoma has not yet been explored.

Methods

A novel human epidermal growth factor receptor 2 (HER2)-targeted CAR containing scFv-FRP5, CD8α hinge and transmembrane domains as well as 4-1BB costimulatory and CD3ζ signaling domains was developed. Three synovial sarcoma cell lines that expressed the fusion transcript SS18-SSX1/2/4 were used in the study. Cytokine secretion assay, cytotoxicity assay, and real-time cell analysis experiments were conducted to confirm the function of T cells transduced with the CAR gene.

Results

High cell-surface expression of HER2 was observed in all the cell lines. HER2-targeted/4-1BB-costimulated CAR T cells specifically recognized the synovial sarcoma cells, secreted interferon gamma and tumor necrosis factor alpha, and exerted cytotoxic effects in these cells.

Conclusion

To the best of our knowledge, this is the first study to indicate that HER2-targeted CAR T cells are directly effective against molecularly defined synovial sarcoma cells. Furthermore, our findings might set the basis for developing improved CAR T cell-based therapies for chemo-refractory or relapsed synovial sarcoma.

Identifying and managing CAR T-cell-mediated toxicities: on behalf of an Italian CAR-T multidisciplinary team

INTRODUCTION

Chimeric antigen receptor (CAR)-T-cell therapy is a new treatment for patients with hematologic malignancies in which other therapies have failed.

AREAS COVERED

The review provides an overview for recognizing and managing the most acute toxicities related to CAR-T cells.

EXPERT OPINION

The development of immune-mediated toxicities is a common challenge of CAR-T therapy. The mechanism that determines this toxicity is still unclear, although an unfavorable tumor microenvironment and a pro-inflammatory state put patients at risk. The monitoring, diagnosis, and treatment of post-CAR-T toxicities must be determined and based on international guidelines and internal clinical practice. It is urgent to identify biomarkers that can identify patients at greater risk of developing complications. The adoption of consistent grading criteria is necessary to improve toxicity management strategies continually. The first-line therapy consists of supportive care and treatment with tocilizumab or corticosteroids. An early start of cytokine blockade therapies could mitigate toxicity. The plan will include cytokine release prophylaxis, a risk-adapted treatment, prevention of on-target/off-tumor effect, and a switch on/off CAR-T approach.

Extracellular Vesicles Derived from Chimeric Antigen Receptor-T Cells: A Potential Therapy for Cancer

Chimeric antigen receptor (CAR)-T cells are genetically engineered T cells, directed against a tumor-associated antigen. Extracellular vesicles (EVs) derived from CAR-T cells (CAR-T EVs) may preserve CAR-T activity and overcome one of the major obstacles responsible for CAR-T cell failure in patients with solid tumors. This study aimed to compare CAR-T EVs with their parental cells and explore their cell penetration and cytotoxic activity. Anti-HER-2 CARs were stimulated with specific target cells. EVs were isolated from the cell media and characterized for their content and functions. We found that CAR-T EVs contained a mixture of small and large EVs. Stimulated anti-HER-2⁺ CAR-T EVs expressed lower cytokine levels compared with their parental CAR-T cells (such as interferon gamma). Higher levels of granzyme B were found in CAR-T EVs (≥20 × ) compared with EVs from unstimulated cells (p < 0.001). Anti-HER-2⁺ CAR-T EVs bound and penetrated specifically into HER-2 expressing target cells. Similar cytotoxic effects measured by caspase-3/7 activity were found in CAR-T cells and their derived EVs. However, while the CAR-T cells induced massive apoptosis during the first 24 h, CAR-T EVs required 60 - 90 h. In summary, CAR-T EVs provide a novel potent immunotherapy approach that may be effective against solid tumors.

CARs and beyond: tailoring macrophage-based cell therapeutics to combat solid malignancies

Recent understanding of the role and contribution of immune cells in disease onset and progression has pioneered the field of immunotherapies. Use of genetic engineering to deliver, correct or enhance immune cells has been clinically successful, especially in the field of cancer immunotherapy. Indeed, one of the most attractive approaches is the introduction of chimeric antigen receptors (CARs) to immune cells, such as T cells. Recent studies revealed that adapting this platform for use in macrophages may widen the spectrum of CAR applications for better control of solid tumors and, thus, extend this treatment strategy to more patients with cancer. Given the novel insights into tumor-associated macrophages and new targeting strategies to boost anticancer therapy, this review aims to provide an overview of the current status of the role of macrophages in cancer therapy. The various genetic engineering approaches that can be used to optimize macrophages for use in oncology are discussed, with special attention dedicated to the implication of the CAR platform on macrophages for anticancer therapy. The current clinical status, challenges and future perspective of macrophage-based drugs are highlighted.

CRISPR/Cas9 revitalizes adoptive T-cell therapy for cancer immunotherapy

Cancer immunotherapy has gained attention as the supreme therapeutic modality for the treatment of various malignancies. Adoptive T-cell therapy (ACT) is one of the most distinctive modalities of this therapeutic approach, which seeks to harness the potential of combating cancer cells by using autologous or allogenic tumor-specific T-cells. However, a plethora of circumstances must be optimized to produce functional, durable, and efficient T-cells. Recently, the potential of ACT has been further realized by the introduction of novel gene-editing platforms such as the CRISPR/Cas9 system; this technique has been utilized to create T-cells furnished with recombinant T-cell receptor (TCR) or chimeric antigen receptor (CAR) that have precise tumor antigen recognition, minimal side effects and treatment-related toxicities, robust proliferation and cytotoxicity, and nominal exhaustion. Here, we aim to review and categorize the recent breakthroughs of genetically modified TCR/CAR T-cells through CRISPR/Cas9 technology and address the pearls and pitfalls of each method. In addition, we investigate the latest ongoing clinical trials that are applying CRISPR-associated TCR/CAR T-cells for the treatment of cancers.

Nanocarriers as a Tool for the Treatment of Colorectal Cancer

Nanotechnology is a promising tool for the treatment of cancer. In the past decades, major steps have been made to bring nanotechnology into the clinic in the form of nanoparticle-based drug delivery systems. The great hope of drug delivery systems is to reduce the side effects of chemotherapeutics while simultaneously increasing the efficiency of the therapy. An increased treatment efficiency would greatly benefit the quality of life as well as the life expectancy of cancer patients. However, besides its many advantages, nanomedicines have to face several challenges and hurdles before they can be used for the effective treatment of tumors. Here, we give an overview of the hallmarks of cancer, especially colorectal cancer, and discuss biological barriers as well as how drug delivery systems can be utilized for the effective treatment of tumors and metastases.

Next-Generation Immunotherapy Approaches in Melanoma

PURPOSE OF REVIEW

For patients with metastatic melanoma, immune checkpoint inhibition has drastically changed outcomes. Here, we review the current and next generations of immune-based anti-cancer therapeutics for patients with metastatic melanoma.

RECENT FINDINGS

The need for new anti-cancer therapeutics in patients with metastatic melanoma who have progression of disease despite immune checkpoint blockade is evident. Several novel agents are expected to have FDA approval within the next few years, as they have yielded impressive responses. Despite these optimistic agents, the field of immuno-oncology continues to expand and produce agents with novel mechanisms of action. The next generation of immunotherapy is based upon years of thoroughly researched immuno-oncology. Many of these agents are currently being evaluated in early phase clinical trials, and much of the preliminary data looks promising.

CAR T cells: Building on the CD19 paradigm

Spearheaded by the therapeutic use of chimeric antigen receptors (CARs) targeting CD19, synthetic immunology has entered the clinical arena. CARs are recombinant receptors for antigen that engage cell surface molecules through the variable region of an antibody and signal through arrayed T-cell activating and costimulatory domains. CARs allow redirection of T-cell cytotoxicity against any antigen of choice, independent of MHC expression. Patient T cells engineered to express CARs specific for CD19 have yielded remarkable outcomes in subjects with relapsed/refractory B- cell malignancies, setting off unprecedented interest in T-cell engineering and cell-based cancer immunotherapy. In this review, we present the challenges to extend the use of CAR T cells to solid tumors and other pathologies. We further highlight progress in CAR design, cell manufacturing, and genome editing, which in aggregate hold the promise of generating safer and more effective genetically instructed immunity. Novel engineered cell types, including innate T-cell types, natural killer (NK) cells, macrophages, and induced pluripotent stem cell-derived immune cells, are on the horizon, as are applications of CAR T cells to treat autoimmunity, severe infections, and senescence-associated pathologies.

Ecology of Fear: Spines, Armor and Noxious Chemicals Deter Predators in Cancer and in Nature

In nature, many multicellular and unicellular organisms use constitutive defenses such as armor, spines, and noxious chemicals to keep predators at bay. These defenses render the prey difficult and/or dangerous to subdue and handle, which confers a strong deterrent for predators. The distinct benefit of this mode of defense is that prey can defend in place and continue activities such as foraging even under imminent threat of predation. The same qualitative types of armor-like, spine-like, and noxious defenses have evolved independently and repeatedly in nature, and we present evidence that cancer is no exception. Cancer cells exist in environments inundated with predator-like immune cells, so the ability of cancer cells to defend in place while foraging and proliferating would clearly be advantageous. We argue that these defenses repeatedly evolve in cancers and may be among the most advanced and important adaptations of cancers. By drawing parallels between several taxa exhibiting armor-like, spine-like, and noxious defenses, we present an overview of different ways these defenses can appear and emphasize how phenotypes that appear vastly different can nevertheless have the same essential functions. This cross-taxa comparison reveals how cancer phenotypes can be interpreted as anti-predator defenses, which can facilitate therapy approaches which aim to give the predators (the immune system) the upper hand. This cross-taxa comparison is also informative for evolutionary ecology. Cancer provides an opportunity to observe how prey evolve in the context of a unique predatory threat (the immune system) and varied environments.