Liver myeloid-derived suppressor cells expand in response to liver metastases in mice and inhibit the anti-tumor efficacy of anti-CEA CAR-T

Role of cell-based therapies in digestive disorders: Obstacles and opportunities

Stem cell-based therapies have emerged as a promising frontier in the treatment of gastrointestinal disorders, offering potential solutions for challenges posed by conventional treatments. This review comprehensively examines recent advancements in cell-based therapeutic strategies, particularly focusing on stem cell applications, immunotherapy, and cellular therapies for digestive diseases. It highlights the successful differentiation of enteric neural progenitors from pluripotent stem cells and their application in animal models, such as Hirschsprung disease. Furthermore, the review evaluates clinical trials and experimental studies demonstrating the potential of stem cells in regenerating damaged tissues, modulating immune responses, and promoting healing in conditions like Crohn's disease and liver failure. By addressing challenges, such as scalability, immunogenicity, and ethical considerations, the review underscores the translational opportunities and obstacles in realizing the clinical potential of these therapies. Concluding with an emphasis on future directions, the study provides insights into optimizing therapeutic efficacy and fostering innovations in personalized medicine for digestive disorders.

Overcoming chimeric antigen receptor-T (CAR-T) resistance with checkpoint inhibitors: Existing methods, challenges, clinical success, and future prospects : A comprehensive review

Immune checkpoint blockade is, as of today, the most successful form of cancer immunotherapy, with more than 43 % of cancer patients in the US eligible to receive it; however, only up to 12.5 % of patients respond to it. Similarly, adoptive cell therapy using bioengineered chimeric antigen receptorT (CAR-T) cells and T-cell receptor (TCR) cells has provided excellent responses against liquid tumours, but both forms of immunotherapy have encountered challenges within a tumour microenvironment that is both lacking in tumour-specific T-cells and is strongly immunosuppressive toward externally administered CAR-T and TCR cells. This review focuses on understanding approved checkpoint blockade and adoptive cell therapy at both biological and clinical levels before delving into how and why their combination holds significant promise in overcoming their individual shortcomings. The advent of next-generation checkpoint inhibitors has further strengthened the immune checkpoint field, and a special section explores how these inhibitors can address existing hurdles in combining checkpoint blockade with adoptive cell therapy and homing in on our cancer target for long-term immunity.

Review of Adoptive Cellular Therapies for the Treatment of Sarcoma

Sarcomas are a heterogeneous group of malignancies with limited therapeutic options, particularly in the metastatic setting. Adoptive cellular therapies (ACTs), including tumor-infiltrating lymphocyte (TIL) therapy, chimeric antigen receptor (CAR) T-cell therapy, and T-cell receptor (TCR) gene-modified T-cell therapy, offer promising novel approaches for these refractory tumors. TIL-based therapy has demonstrated early efficacy in melanoma and myeloma, with ongoing trials exploring its role in sarcoma. CAR T-cell strategies targeting HER2, GD2, and B7-H3 antigens are in development, though challenges such as tumor microenvironment-mediated resistance and antigen escape remain significant. Engineered TCRs, particularly those targeting MAGE-A4 and NY-ESO-1, have shown promising clinical results in synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCLS), leading to the recent FDA approval of afamitresgene autoleucel (afami-cel) and letetresgene autoleucel (lete-cel). Despite encouraging preliminary data, ACT implementation faces barriers including limited antigen specificity, off-tumor toxicity, immune evasion, and manufacturing scalability. Future research will focus on optimizing lymphodepleting regimens, mitigating toxicity, enhancing in vivo persistence, and combining ACT with other therapeutic agents. As clinical trials expand, ACT holds the potential to revolutionize sarcoma treatment by offering durable, targeted therapies for previously refractory disease.

The Bidirectional Interplay between T Cell-Based Immunotherapies and the Tumor Microenvironment

T cell-based therapies, including tumor-infiltrating lymphocyte therapy, T-cell receptor-engineered T cells, and chimeric antigen receptor T cells, are powerful therapeutic approaches for cancer treatment. Whereas these therapies are primarily known for their direct cytotoxic effects on cancer cells, accumulating evidence indicates that they also influence the tumor microenvironment (TME) by altering the cytokine milieu and recruiting additional effector populations to help orchestrate the antitumor immune response. Conversely, the TME itself can modulate the behavior of these therapies within the host by either supporting or inhibiting their activity. In this review, we provide an overview of clinical and preclinical data on the bidirectional influences between T-cell therapies and the TME. Unraveling the interactions between T cell-based therapies and the TME is critical for a better understanding of their mechanisms of action, resistance, and toxicity, with the goal of optimizing efficacy and safety.

Myeloid-Derived Suppressor Cells: Implications in Cancer Immunology and Immunotherapy

Myeloid-derived suppressor cells (MDSCs) are believed to be key promoters of tumor development and are recognized as a hallmark of cancer cells' ability to evade the immune system evasion. MDSC levels often increase in peripheral blood and the tumor microenvironment (TME). These cells exert immunosuppressive functions, weakening the anticancer immune surveillance system, in part by repressing T-cell immunity. Moreover, MDSCs may promote tumor progression and interact with cancer cells, increasing MDSC expansion and favoring an immunotolerant TME. This review analyzes the primary roles of MDSCs in cancer and T-cell immunity, discusses the urgent need to develop effective MDSC-targeted therapies, and highlights the potential synergistic combination of MDSC targeting with chimeric antigen receptors and immune checkpoint inhibitors.

Unlocking the potential of chimeric antigen receptor T cell engineering immunotherapy: Long road to achieve precise targeted therapy for hepatobiliary pancreatic cancers

Innovative therapeutic strategies are urgently needed to address the ongoing global health concern of hepatobiliary pancreatic malignancies. This review summarizes the latest and most comprehensive research of chimeric antigen receptor (CAR-T) cell engineering immunotherapy for treating hepatobiliary pancreatic cancers. Commencing with an exploration of the distinct anatomical location and the immunosuppressive, hypoxic tumor microenvironment (TME), this review critically assesses the limitations of current CAR-T therapy in hepatobiliary pancreatic cancers and proposes corresponding solutions. Various studies aim at enhancing CAR-T cell efficacy in these cancers through improving T cell persistence, enhancing antigen specificity and reducing tumor heterogeneity, also modulating the immunosuppressive and hypoxic TME. Additionally, the review examines the application of emerging nanoparticles and biotechnologies utilized in CAR-T therapy for these cancers. The results suggest that constructing optimized CAR-T cells to overcome physical barrier, manipulating the TME to relieve immunosuppression and hypoxia, designing CAR-T combination therapies, and selecting the most suitable delivery strategies, all together could collectively enhance the safety of CAR-T engineering and advance the effectiveness of adaptive cell therapy for hepatobiliary pancreatic cancers.

Recent advancements in improving the efficacy and safety of chimeric antigen receptor (CAR)-T cell therapy for hepatocellular carcinoma

The liver is one of the most frequent sites of primary malignancies in humans. Hepatocellular carcinoma (HCC) is one of the most prevalent solid tumors with poor prognosis. Current treatments showed limited efficacy in some patients, and, therefore, alternative strategies, such as immunotherapy, cancer vaccines, adoptive cell therapy (ACT), and recently chimeric antigen receptors (CAR)-T cells, are developed to offer better efficacy and safety profile in patients with HCC. Unlike other ACTs like tumor-infiltrating lymphocytes (TILs), CAR-T cells are equipped with engineered CAR receptors that effectively identify tumor antigens and eliminate cancer cells without major histocompatibility complex (MHC) restriction. This process induces intracellular signaling, leading to T lymphocyte recruitment and subsequent activation of other effector cells in the tumor microenvironment (TME). Until today, novel approaches have been used to develop more potent CAR-T cells with robust persistence, specificity, trafficking, and safety. However, the clinical application of CAR-T cells in solid tumors is still challenging. Therefore, this study aims to review the advancement, prospects, and possible avenues of CAR-T cell application in HCC following an outline of the CAR structure and function.

Adoptive cell therapy in acute myeloid leukemia: the current landscape and emerging strategies

Efforts to produce adoptive cell therapies in AML have been largely unfruitful, despite the success seen in lymphoid malignancies. Identifying targetable antigens on leukemic cells that are absent on normal progenitor cells remains a major obstacle, as is the hostile tumor microenvironment created by AML blasts. In this review, we summarize the challenges in the development of adoptive cell therapies such as CAR-T, CAR-NK, and TCR-T cells in AML, discussing both autologous and allogeneic therapies. We also discuss methods to address myelotoxicity associated with these therapies, including rapidly switchable CAR platforms and CRISPR-Cas9 genetic engineering of hematopoietic stem cells. Finally, we present the current clinical landscape in these areas, along with future directions in the field.

GPC-3 in hepatocellular carcinoma; A novel biomarker and molecular target

Hepatocellular carcinoma (HCC) is a global health issue due to its late diagnosis and high recurrence rate. The early detection and diagnosis of HCC with specific and sensitive biomarkers and using novel treatment approaches to improve patient outcomes are essential. Glypican-3 (GPC-3) is a cell surface proteoglycan that is overexpressed in many tumors, including HCC. GPC-3 could be used as a specific biomarker for HCC early detection and could be a potential target for precise therapeutic strategies. Effective identification of GPC-3 could improve both diagnosis and targeted therapy of HCC. Moreover, targeted therapy using GPC-3 could result in a better treatment outcome. Recently, GPC3-targeted therapies have been used in different investigational therapeutic approaches like bi-specific/monoclonal antibodies, peptide vaccines, and CAR T cell therapies. This study aims to highlight the theranostic potential of GPC-3 as a novel biomarker for early detection and as a potential molecular target for HCC treatment as well.

CAR T Cell Nanosymbionts: Revealing the Boundless Potential of a New Dyad

Cancer treatment has traditionally focused on eliminating tumor cells but faces challenges such as resistance and toxicity. A promising direction involves targeting the tumor microenvironment using CAR T cell immunotherapy, which has shown potential for treating relapsed and refractory cancers but is limited by high costs, resistance, and toxicity, especially in solid tumors. The integration of nanotechnology into ICAM cell therapy, a concept we have named "CAR T nanosymbiosis", offers new opportunities to overcome these challenges. Nanomaterials can enhance CAR T cell delivery, manufacturing, activity modulation, and targeting of the tumor microenvironment, providing better control and precision. This approach aims to improve the efficacy of CAR T cells against solid tumors, reduce associated toxicities, and ultimately enhance patient outcomes. Several studies have shown promising results, and developing this therapy further is essential for increasing its accessibility and effectiveness. Our "addition by subtraction model" synthesizes these multifaceted elements into a unified strategy to advance cancer treatment paradigms.

Chimeric Antigen Receptor (CAR)-T Cells: A New Era for Hepatocellular Carcinoma Treatment

Hepatocellular carcinoma (HCC) is one of the most common cancers and a worldwide health concern that requires novel treatment approaches. Tyrosine kinase inhibitors (TKIs) and immune checkpoint blockades (ICBs) are the current standard of care; however, their clinical benefits are limited in some advanced and metastatic patients. With the help of gene engineering techniques, a novel adoptive cellular therapy (ACT) called chimeric antigen receptor (CAR)-T cells was recently introduced for treating HCC. A plethora of current clinical and preclinical studies are attempting to improve the efficacy of CAR-T cells by dominating the immunosuppressive environment of HCC and finding the best tumor-specific antigens (TSAs). The future of care for HCC patients might be drastically improved due to the convergence of novel therapeutic methods and the continuous progress in ACT research. However, the clinical application of CAR-T cells in solid tumors is still facing several challenges. In this study, we provide an overview of the advancement and prospects of CAR-T cell immunotherapy in HCC, as well as an investigation of how cutting-edge engineering could improve CAR-T cell efficacy and safety profile.

CAR T cells in solid tumors and metastasis: paving the way forward

CAR T cell therapy, hailed as a breakthrough in cancer treatment due to its remarkable outcomes in hematological malignancies, encounters significant hurdles when applied to solid tumors. While notable responses to CAR T cells remain sporadic in these patients, challenges persist due to issues such as on-target off-tumor toxicity, difficulties in their trafficking and infiltration into the tumor, and the presence of a hostile and immunosuppressive microenvironment. This review aims to explore recent endeavors aimed at overcoming these obstacles in CAR T cell therapy for solid tumors. Specifically, we will delve into promising strategies for enhancing tumor specificity through antigen targeting, addressing tumor heterogeneity, overcoming physical barriers, and counteracting the immune-suppressive microenvironment.

Syngeneic Mouse Models for Pre-Clinical Evaluation of CAR T Cells

Chimeric antigen receptor (CAR) T cells have revolutionized the treatment of hematological malignancies. Unfortunately, this improvement has yet to be translated into the solid tumor field. Current immunodeficient models used in pre-clinical testing often overestimate the efficacy of CAR T cell therapy as they fail to recapitulate the immunosuppressive tumor microenvironment characteristic of solid tumors. As CAR T cell monotherapy is unlikely to be curative for many solid tumors, combination therapies must be investigated, for example, stromal remodeling agents and immunomodulators. The evaluation of these combination therapies requires a fully immunocompetent mouse model in order to recapitulate the interaction between the host's immune system and the CAR T cells. This review will discuss the need for improved immunocompetent murine models for the pre-clinical evaluation of CAR T cells, the current use of such models and future directions.

Harnessing the tumor microenvironment to boost adoptive T cell therapy with engineered lymphocytes for solid tumors

Adoptive cell therapy (ACT) using Chimeric Antigen Receptor (CAR) and T Cell Receptor (TCR) engineered T cells represents an innovative therapeutic approach for the treatment of hematological malignancies, yet its application for solid tumors is still suboptimal. The tumor microenvironment (TME) places several challenges to overcome for a satisfactory therapeutic effect, such as physical barriers (fibrotic capsule and stroma), and inhibitory signals impeding T cell function. Some of these obstacles can be faced by combining ACT with other anti-tumor approaches, such as chemo/radiotherapy and checkpoint inhibitors. On the other hand, cutting edge technological tools offer the opportunity to overcome and, in some cases, take advantage of TME intrinsic characteristics to boost ACT efficacy. These include: the exploitation of chemokine gradients and integrin expression for preferential T-cell homing and extravasation; metabolic changes that have direct or indirect effects on TCR-T and CAR-T cells by increasing antigen presentation and reshaping T cell phenotype; introduction of additional synthetic receptors on TCR-T and CAR-T cells with the aim of increasing T cells survival and fitness.

Deciphering the tumor immune microenvironment from a multidimensional omics perspective: insight into next-generation CAR-T cell immunotherapy and beyond

Tumor immune microenvironment (TIME) consists of intra-tumor immunological components and plays a significant role in tumor initiation, progression, metastasis, and response to therapy. Chimeric antigen receptor (CAR)-T cell immunotherapy has revolutionized the cancer treatment paradigm. Although CAR-T cell immunotherapy has emerged as a successful treatment for hematologic malignancies, it remains a conundrum for solid tumors. The heterogeneity of TIME is responsible for poor outcomes in CAR-T cell immunotherapy against solid tumors. The advancement of highly sophisticated technology enhances our exploration in TIME from a multi-omics perspective. In the era of machine learning, multi-omics studies could reveal the characteristics of TIME and its immune resistance mechanism. Therefore, the clinical efficacy of CAR-T cell immunotherapy in solid tumors could be further improved with strategies that target unfavorable conditions in TIME. Herein, this review seeks to investigate the factors influencing TIME formation and propose strategies for improving the effectiveness of CAR-T cell immunotherapy through a multi-omics perspective, with the ultimate goal of developing personalized therapeutic approaches.

CAR-T cell therapy: a game-changer in cancer treatment and beyond

In recent years, cancer has become one of the primary causes of mortality, approximately 10 million deaths worldwide each year. The most advanced, chimeric antigen receptor (CAR) T cell immunotherapy has turned out as a promising treatment for cancer. CAR-T cell therapy involves the genetic modification of T cells obtained from the patient's blood, and infusion back to the patients. CAR-T cell immunotherapy has led to a significant improvement in the remission rates of hematological cancers. CAR-T cell therapy presently limited to hematological cancers, there are ongoing efforts to develop additional CAR constructs such as bispecific CAR, tandem CAR, inhibitory CAR, combined antigens, CRISPR gene-editing, and nanoparticle delivery. With these advancements, CAR-T cell therapy holds promise concerning potential to improve upon traditional cancer treatments such as chemotherapy and radiation while reducing associated toxicities. This review covers recent advances and advantages of CAR-T cell immunotherapy.

Non-viral expression of chimeric antigen receptors with multiplex gene editing in primary T cells

Efficient engineering of T cells to express exogenous tumor-targeting receptors such as chimeric antigen receptors (CARs) or T-cell receptors (TCRs) is a key requirement of effective adoptive cell therapy for cancer. Genome editing technologies, such as CRISPR/Cas9, can further alter the functional characteristics of therapeutic T cells through the knockout of genes of interest while knocking in synthetic receptors that can recognize cancer cells. Performing multiple rounds of gene transfer with precise genome editing, termed multiplexing, remains a key challenge, especially for non-viral delivery platforms. Here, we demonstrate the efficient production of primary human T cells incorporating the knockout of three clinically relevant genes (B2M, TRAC, and PD1) along with the non-viral transfection of a CAR targeting disialoganglioside GD2. Multiplexed knockout results in high on-target deletion for all three genes, with low off-target editing and chromosome alterations. Incorporating non-viral delivery to knock in a GD2-CAR resulted in a TRAC-B2M-PD1-deficient GD2 CAR T-cell product with a central memory cell phenotype and high cytotoxicity against GD2-expressing neuroblastoma target cells. Multiplexed gene-editing with non-viral delivery by CRISPR/Cas9 is feasible and safe, with a high potential for rapid and efficient manufacturing of highly potent allogeneic CAR T-cell products.

Emerging therapeutic approaches for peritoneal metastases from gastrointestinal cancers

Peritoneal metastases from gastrointestinal malignancies present difficult management decisions, with options consisting primarily of systemic chemotherapy or major surgery with or without hyperthermic intraperitoneal chemotherapy. Current research is investigating expanding therapeutic modalities, and the aim of this review is to provide an overview of the existing and emerging therapies for the peritoneal metastases from gastrointestinal cancers, primarily through the recent literature (2015 and newer). These include the current data with systemic therapy and cytoreduction with hyperthermic intraperitoneal or pressurized intraperitoneal aerosol chemotherapy, as well as novel promising modalities under investigation, including dominating oncolytic viral therapy and adoptive cellular, biologic, and bacteria therapy, or nanotechnology. The novel diverse strategies, although preliminary and preclinical in murine models, individually and collectively contribute to the treatment of peritoneal metastases, offering hope for improved outcomes and quality of life. We foresee that these evolving treatment approaches will facilitate the transfer of knowledge and data among studies and advance discovery of new drugs and optimized treatments for patients with peritoneal metastases.

Chimeric Antigen Receptor T Cell Therapy for Hepatocellular Carcinoma: Where Do We Stand?

Hepatocellular carcinoma (HCC) remains a global health challenge that urgently calls for innovative therapeutic strategies. Chimeric antigen receptor T cell (CAR T) therapy has emerged as a promising avenue for HCC treatment. However, the therapeutic efficacy of CAR T immunotherapy in HCC patients is significantly compromised by some major issues including the immunosuppressive environment within the tumor, antigen heterogeneity, CAR T cell exhaustion, and the advanced risk for on-target/off-tumor toxicity. To overcome these challenges, many ongoing preclinical and clinical trials are underway focusing on the identification of optimal target antigens and the decryption of the immunosuppressive milieu of HCC. Moreover, limited tumor infiltration constitutes a significant obstacle of CAR T cell therapy that should be addressed. The continuous effort to design molecular targets for CAR cells highlights the importance for a more practical approach for CAR-modified cell manufacturing. This review critically examines the current landscape of CAR T cell therapy for HCC, shedding light on the changes in innate and adaptive immune responses in the context of HCC, identifying potential CAR T cell targets, and exploring approaches to overcome inherent challenges. Ongoing advancements in scientific research and convergence of diverse treatment modalities offer the potential to greatly enhance HCC patients' care in the future.

Modifying CAR-T cells with anti-checkpoints in cancer immunotherapy: A focus on anti PD-1/PD-L1 antibodies

Chimeric antigen receptor-modified T (CAR-T) are genetically engineered cells to express tumor-specific antigens revolutionizing the treatment of hematologic malignancies. The hostile tumor microenvironment (TME) remains a challenge for CAR-T cell therapy in solid tumors. As a solution, combinational therapy with immune checkpoint inhibitors (ICIs) is shown to improve the safety and efficacy of CAR-T cell therapy. To avoid side effects related to the application of ICIs in combinational therapy, engineering CARs to express tumor-specific antigens may help improvement of clinical outcomes. Those CARs expressing single chain variable fragments (scFvs) or nanobodies against immune checkpoint stimulatory or inhibitory molecules, such as the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling axis are being extensively studied in various clinical trials. In this review, we discuss the significance of anti-PD-(L)1 scFv-expressing CAR-T cells in the treatment of human cancers, describing current challenges and potential strategies to overcome such predicaments in the area of cancer immunotherapy.

PD-1 checkpoint inhibition enhances the antilymphoma activity of CD19-CAR-iNKT cells that retain their ability to prevent alloreactivity

BACKGROUND

Relapse and graft-versus-host disease (GVHD) are the main causes of death after allogeneic hematopoietic cell transplantation (HCT). Preclinical murine models and clinical data suggest that invariant natural killer T (iNKT) cells prevent acute and chronic GVHD. In addition, iNKT cells are crucial for efficient immune responses against malignancies and contribute to reduced relapse rates after transplantation. Chimeric antigen receptors (CAR) redirect effector cells to cell surface antigens and enhance killing of target cells. With this study, we aimed to combine enhanced cytotoxicity of CD19-CAR-iNKT cells against lymphoma cells with their tolerogenic properties.

METHODS

iNKT cells were isolated from peripheral blood mononuclear cells and transduced with an anti-CD19-CAR retrovirus. After in vitro expansion, the functionality of CD19-CAR-iNKT cells was assessed by flow cytometry, image stream analysis and multiplex analysis in single-stimulation or repeated-stimulation assays. Moreover, the immunoregulatory properties of CD19-CAR-iNKT cells were analyzed in apoptosis assays and in mixed lymphocyte reactions. The effect of checkpoint inhibition through nivolumab was analyzed in these settings.

RESULTS

In this study, we could show that the cytotoxicity of CD19-CAR-iNKT cells was mediated either through engagement of their CAR or their invariant T-cell receptor, which may circumvent loss of response through antigen escape. However, encounter of CD19-CAR-iNKT cells with their target induced a phenotype of exhaustion. Consequently, checkpoint inhibition increased cytokine release, cytotoxicity and survival of CD19-CAR-iNKT cells. Additionally, they showed robust suppression of alloreactive immune responses.

CONCLUSION

In this work, we demonstrate that CAR-iNKT cells are a powerful cytotherapeutic option to prevent or treat relapse while potentially reducing the risk of GVHD after allogeneic HCT.

Application of adoptive cell therapy in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains a global health challenge. Novel treatment modalities are urgently needed to extend the overall survival of patients. The liver plays an immunomodulatory function due to its unique physiological structural characteristics. Therefore, following surgical resection and radiotherapy, immunotherapy regimens have shown great potential in the treatment of hepatocellular carcinoma. Adoptive cell immunotherapy is rapidly developing in the treatment of hepatocellular carcinoma. In this review, we summarize the latest research on adoptive immunotherapy for hepatocellular carcinoma. The focus is on chimeric antigen receptor (CAR)-T cells and T cell receptor (TCR) engineered T cells. Then tumour-infiltrating lymphocytes (TILs), natural killer (NK) cells, cytokine-induced killer (CIK) cells, and macrophages are briefly discussed. The main overview of the application and challenges of adoptive immunotherapy in hepatocellular carcinoma. It aims to provide the reader with a comprehensive understanding of the current status of HCC adoptive immunotherapy and offers some strategies. We hope to provide new ideas for the clinical treatment of hepatocellular carcinoma.

Synthetic manipulation of the cancer-immunity cycle: CAR-T cell therapy

Synthetic immunity to cancer has been pioneered by the application of chimeric antigen receptor (CAR) engineering into autologous T cells. CAR T cell therapy is highly amenable to molecular engineering to bypass barriers of the cancer immunity cycle, such as endogenous antigen presentation, immune priming, and natural checkpoints that constrain immune responses. Here, we review CAR T cell design and the mechanisms that drive sustained CAR T cell effector activity and anti-tumor function. We discuss engineering approaches aimed at improving anti-tumor function through a variety of mechanistic interventions for both hematologic and solid tumors. The ability to engineer T cells in such a variety of ways, including by modifying their trafficking, antigen recognition, costimulation, and addition of synthetic genes, circuits, knockouts and base edits to finely tune complex functions, is arguably the most powerful way to manipulate the cancer immunity cycle in patients.

The prognostic value of COX-2 in predicting metastasis of patients with colorectal cancer: A systematic review and meta analysis

Introduction

COX-2 is overexpressed in colorectal tumour tissue relative to the healthy colonic mucosa, thus we investigated the prognostic significance of COX-2 in determining the metastasis of patients with colorectal cancer.

Methods

PubMed, EMBASE, and Cochrane Library were searched using the following terms colorectal cancer, colon cancer, rectal cancer, colorectal carcinoma, Cyclooxygenase-2, and prognosis to identify articles providing information on the prognostic importance of COX-2 in adult patients with metastatic colorectal cancer. Review papers, non-research letters, comments, case reports, animal studies, original research with sample sizes of fewer than 20, case reports and series, non-English language articles, and pediatric studies (those under the age of 17) were excluded. The Newcastle Ottawa Scale (NOS) was used to assess the credibility of the included studies. The full texts were evaluated and this study complied with the terms of the local protocol and the Helsinki Declaration.

Results

Eight relevant studies were included in this review involving 937 patients. The meta-analysis revealed that COX-2 expression is associated with lymph node invasion (RR 1.85 [1.21, 2.83], P = 0.005, I2 = 88 %) and liver metastasis (RR 4.90 [1.12, 21.57], P = 0.04, I2 = 42 %), but not with venous dissemination (RR 1.48 [0.72, 3.03], P = 0.28, I2 = 87 %).

Conclusion

COX-2 expression is associated with lymph node invasion in colorectal cancer but further studies are required to determine the prognostic significance of COX-2 expression in determining metastasis status for colorectal cancer patients.

Natural killer cells modified with a Gpc3 aptamer enhance adoptive immunotherapy for hepatocellular carcinoma

INTRODUCTION

Natural killer cells can attack cancer cells without prior sensitization, but their clinical benefit is limited owing to their poor selectivity that is caused by the lack of specific receptors to target tumor cells. In this study, we aimed to endow NK cells with the ability to specifically target glypican-3+ tumor cells without producing cell damage or genetic alterations, and further evaluated their therapeutic efficiency.

METHODS

NK cells were modified with a Gpc3 DNA aptamer on the cell surface via metabolic glycoengineering to endow NK cells with specific targeting ability. Then, the G-NK cells were evaluated for their specific targeting properties, cytotoxicity and secretion of cytokines in vitro. Finally, we investigated the therapeutic efficiency of G-NK cells against glypican-3+ tumor cells in vivo.

RESULTS

Compared with NK cells modified with a random aptamer mutation and unmodified NK cells, G-NK cells induced significant apoptosis/necrosis of GPC3+ tumor cells and secreted cytokines to preserve the intense cytotoxic activities. Moreover, G-NK cells significantly suppressed tumor growth in HepG2 tumor-bearing mice due to the enhanced enrichment of G-NK cells at the tumor site.

CONCLUSIONS

The proposed strategy endows NK cells with a tumor-specific targeting ability to enhance adoptive therapeutic efficiency in GPC3+ hepatocellular carcinoma.

Pressure-Enabled Drug Delivery (PEDD) of a class C TLR9 agonist in combination with checkpoint inhibitor therapy in a murine pancreatic cancer model

BACKGROUND

Systemic immunotherapy has had limited clinical benefit in pancreatic ductal adenocarcinoma. This is thought to be due to its desmoplastic immunosuppressive tumor microenvironment in addition to high intratumoral pressures that limit drug delivery. Recent preclinical cancer models and early-phase clinical trials have demonstrated the potential of toll-like receptor 9 agonists, including the synthetic CpG oligonucleotide SD-101, to stimulate a wide range of immune cells and eliminate suppressive myeloid cells. We hypothesized that Pressure-Enabled Drug Delivery via Pancreatic Retrograde Venous Infusion of toll-like receptor 9 agonist would improve responsiveness to systemic anti-programmed death receptor-1 checkpoint inhibitor therapy in a murine orthotopic pancreatic ductal adenocarcinoma model.

METHODS

Murine pancreatic ductal adenocarcinoma (KPC4580P) tumors were implanted into the pancreatic tails of C57BL/6J mice and treated 8 days after implantation. Mice were assigned to one of the following treatment groups: Pancreatic Retrograde Venous Infusion delivery of saline, Pancreatic Retrograde Venous Infusion delivery of toll-like receptor 9 agonist, systemic anti-programmed death receptor-1, systemic toll-like receptor 9 agonist, or the combination of Pancreatic Retrograde Venous Infusion delivery of toll-like receptor 9 agonist and systemic anti-programmed death receptor-1 (Combo). Fluorescently labeled toll-like receptor 9 agonist (radiant efficiency) was used to measure uptake of the drug on day 1. Changes in tumor burden were evaluated by necropsy at 2 different time points, 7 and 10 days after toll-like receptor 9 agonist treatment. Blood and tumors were collected at necropsy 10 days after toll-like receptor 9 agonist treatment for flow cytometric analysis of tumor-infiltrating leukocytes and plasma cytokines.

RESULTS

All mice analyzed survived to necropsy. Site of tumor fluorescence measurements revealed 3-fold higher intensity fluorescence in Pancreatic Retrograde Venous Infusion delivery of toll-like receptor 9 agonist compared to systemic toll-like receptor 9 agonist mice. Tumor weights were significantly lower in the Combo group compared to Pancreatic Retrograde Venous Infusion delivery of saline. Flow cytometry of the Combo group demonstrated significantly increased overall T-cell number, specifically CD4+ T-cells, and a trend toward increased CD8+ T-cells. Cytokine analysis showed significantly decreased IL-6 and CXCL1.

CONCLUSION

Pressure-Enabled Drug Delivery of toll-like receptor 9 agonist by Pancreatic Retrograde Venous Infusion with systemic anti-programmed death receptor-1 demonstrated improved pancreatic ductal adenocarcinoma tumor control in a murine pancreatic ductal adenocarcinoma model. These results support study of this combination therapy in pancreatic ductal adenocarcinoma patients and expansion of ongoing Pressure-Enabled Drug Delivery clinical trials.

Challenges and new technologies in adoptive cell therapy

Adoptive cell therapies (ACTs) have existed for decades. From the initial infusion of tumor-infiltrating lymphocytes to the subsequent specific enhanced T cell receptor (TCR)-T and chimeric antigen receptor (CAR)-T cell therapies, many novel strategies for cancer treatment have been developed. Owing to its promising outcomes, CAR-T cell therapy has revolutionized the field of ACTs, particularly for hematologic malignancies. Despite these advances, CAR-T cell therapy still has limitations in both autologous and allogeneic settings, including practicality and toxicity issues. To overcome these challenges, researchers have focused on the application of CAR engineering technology to other types of immune cell engineering. Consequently, several new cell therapies based on CAR technology have been developed, including CAR-NK, CAR-macrophage, CAR-γδT, and CAR-NKT. In this review, we describe the development, advantages, and possible challenges of the aforementioned ACTs and discuss current strategies aimed at maximizing the therapeutic potential of ACTs. We also provide an overview of the various gene transduction strategies employed in immunotherapy given their importance in immune cell engineering. Furthermore, we discuss the possibility that strategies capable of creating a positive feedback immune circuit, as healthy immune systems do, could address the flaw of a single type of ACT, and thus serve as key players in future cancer immunotherapy.

Updated Clinical Perspectives and Challenges of Chimeric Antigen Receptor-T Cell Therapy in Colorectal Cancer and Invasive Breast Cancer

In recent years, the incidence of colorectal cancer (CRC) and breast cancer (BC) has increased worldwide and caused a higher mortality rate due to the lack of selective anti-tumor therapies. Current chemotherapies and surgical interventions are significantly preferred modalities to treat CRC or BC in advanced stages but the prognosis for patients with advanced CRC and BC remains dismal. The immunotherapy technique of chimeric antigen receptor (CAR)-T cells has resulted in significant clinical outcomes when treating hematologic malignancies. The novel CAR-T therapy target antigens include GUCY2C, CLEC14A, CD26, TEM8/ANTXR1, PDPN, PTK7, PODXL, CD44, CD19, CD20, CD22, BCMA, GD2, Mesothelin, TAG-72, CEA, EGFR, B7H3, HER2, IL13Ra2, MUC1, EpCAM, PSMA, PSCA, NKG2D. The significant aim of this review is to explore the recently updated information pertinent to several novel targets of CAR-T for CRC, and BC. We vividly described the challenges of CAR-T therapies when treating CRC or BC. The immunosuppressive microenvironment of solid tumors, the shortage of tumor-specific antigens, and post-treatment side effects are the major hindrances to promoting the development of CAR-T cells. Several clinical trials related to CAR-T immunotherapy against CRC or BC have already been in progress. This review benefits academicians, clinicians, and clinical oncologists to explore more about the novel CAR-T targets and overcome the challenges during this therapy.

Promise and Challenges of T Cell Immunotherapy for Osteosarcoma

The cure rate for metastatic or relapsed osteosarcoma has not substantially improved over the past decades despite the exploitation of multimodal treatment approaches, allowing long-term survival in less than 30% of cases. Patients with osteosarcoma often develop resistance to chemotherapeutic agents, where personalized targeted therapies should offer new hope. T cell immunotherapy as a complementary or alternative treatment modality is advancing rapidly in general, but its potential against osteosarcoma remains largely unexplored. Strategies incorporating immune checkpoint inhibitors (ICIs), chimeric antigen receptor (CAR) modified T cells, and T cell engaging bispecific antibodies (BsAbs) are being explored to tackle relapsed or refractory osteosarcoma. However, osteosarcoma is an inherently heterogeneous tumor, both at the intra- and inter-tumor level, with no identical driver mutations. It has a pro-tumoral microenvironment, where bone cells, stromal cells, neovasculature, suppressive immune cells, and a mineralized extracellular matrix (ECM) combine to derail T cell infiltration and its anti-tumor function. To realize the potential of T cell immunotherapy in osteosarcoma, an integrated approach targeting this complex ecosystem needs smart planning and execution. Herein, we review the current status of T cell immunotherapies for osteosarcoma, summarize the challenges encountered, and explore combination strategies to overcome these hurdles, with the ultimate goal of curing osteosarcoma with less acute and long-term side effects.

Modulation of Myeloid-Derived Suppressor Cells in the Tumor Microenvironment by Natural Products

During carcinogenesis, the microenvironment plays a fundamental role in tumor progression and resistance. This tumor microenvironment (TME) is characterized by being highly immunosuppressive in most cases, which makes it an important target for the development of new therapies. One of the most important groups of cells that orchestrate immunosuppression in TME is myeloid-derived suppressor cells (MDSCs), which have multiple mechanisms to suppress the immune response mediated by T lymphocytes and thus protect the tumor. In this review, we will discuss the importance of modulating MDSCs as a therapeutic target and how the use of natural products, due to their multiple mechanisms of action, can be a key alternative for modulating these cells and thus improve response to therapy in cancer patients.

Time to abandon CAR-T monotherapy for solid tumors

In recent decades, chimeric antigen receptor T (CAR-T) cell therapy has achieved dramatic success in patients with hematological malignancies. However, CAR-T cell therapy failed to effectively treat solid tumors as a monotherapy. By summarizing the challenges of CAR-T cell monotherapy for solid tumors and analyzing the underlying mechanisms of combinatorial strategies to counteract these hurdles, we found that complementary therapeutics are needed to improve the scant and transient responses of CAR-T cell monotherapy in solid tumors. Further data, especially data from multicenter clinical trials regarding efficacy, toxicity, and predictive biomarkers are required before the CAR-T combination therapy can be translated into clinical settings.

Preclinical evaluation of chimeric antigen receptor T cells targeting the carcinoembryonic antigen as a potential immunotherapy for gallbladder cancer

Gallbladder cancer (GBC) is commonly diagnosed at late stages when conventional treatments achieve only modest clinical benefit. Therefore, effective treatments for advanced GBC are needed. In this context, the administration of T cells genetically engineered with chimeric antigen receptors (CAR) has shown remarkable results in hematological cancers and is being extensively studied for solid tumors. Interestingly, GBC tumors express canonical tumor-associated antigens, including the carcinoembryonic antigen (CEA). However, the potential of CEA as a relevant antigen in GBC to be targeted by CAR-T cell-based immunotherapy has not been addressed. Here we show that CEA was expressed in 88% of GBC tumors, with higher levels associated with advanced disease stages. CAR-T cells specifically recognized plate-bound CEA as evidenced by up-regulation of 4-1BB, CD69 and PD-1, and production of effector cytokines IFN-γ and TNF-α. In addition, CD8+ CAR-T cells up-regulated the cytotoxic molecules granzyme B and perforin. Interestingly, CAR-T cell activation occurred even in the presence of PD-L1. Consistent with these results, CAR-T cells efficiently recognized GBC cell lines expressing CEA and PD-L1, but not a CEA-negative cell line. Furthermore, CAR-T cells exhibited in vitro cytotoxicity and reduced in vivo tumor growth of GB-d1 cells. In summary, we demonstrate that CEA represents a relevant antigen for GBC that can be targeted by CAR-T cells at the preclinical level. This study warrants further development of the adoptive transfer of CEA-specific CAR-T cells as a potential immunotherapy for GBC.

Comprehensive clinical evaluation of CAR-T cell immunotherapy for solid tumors: a path moving forward or a dead end?

INTRODUCTION

Chimeric Antigen Receptor (CAR)-T cell therapy is a form of adoptive cell therapy that has demonstrated tremendous results in the treatment of hematopoietic malignancies, leading to the US Food and Drug Administration (FDA) approval of four CD19-targeted CAR-T cell products. With the unprecedented success of CAR-T cell therapy in hematological malignancies, hundreds of preclinical studies and clinical trials are currently undergoing to explore the translation of this treatment to solid tumors. However, the clinical experience in non-hematologic malignancies has been less encouraging, with only a few patients achieving complete responses. Tumor-associated antigen heterogeneity, inefficient CAR-T cell trafficking and the immunosuppressive tumor microenvironment are considered as the most pivotal roadblocks in solid tumor CAR-T cell therapy.

MATERIALS AND METHODS

We reviewed the relevant literature/clinical trials for CAR-T cell immunotherapy for solid tumors from Pubmed and ClinicalTrials.gov.

CONCLUSION

Herein, we provide an update on solid tumor CAR-T cell clinical trials, focusing on the studies with published results. We further discuss some of the key hurdles that CAR-T cell therapy is encountering for solid tumor treatment as well as the strategies that are exploited to overcome these obstacles.

Leveraging immune resistance archetypes in solid cancer to inform next-generation anticancer therapies

Anticancer immunotherapies, such as immune checkpoint inhibitors, bispecific antibodies, and chimeric antigen receptor T cells, have improved outcomes for patients with a variety of malignancies. However, most patients either do not initially respond or do not exhibit durable responses due to primary or adaptive/acquired immune resistance mechanisms of the tumor microenvironment. These suppressive programs are myriad, different between patients with ostensibly the same cancer type, and can harness multiple cell types to reinforce their stability. Consequently, the overall benefit of monotherapies remains limited. Cutting-edge technologies now allow for extensive tumor profiling, which can be used to define tumor cell intrinsic and extrinsic pathways of primary and/or acquired immune resistance, herein referred to as features or feature sets of immune resistance to current therapies. We propose that cancers can be characterized by immune resistance archetypes, comprised of five feature sets encompassing known immune resistance mechanisms. Archetypes of resistance may inform new therapeutic strategies that concurrently address multiple cell axes and/or suppressive mechanisms, and clinicians may consequently be able to prioritize targeted therapy combinations for individual patients to improve overall efficacy and outcomes.

Strategies for Reducing Toxicity and Enhancing Efficacy of Chimeric Antigen Receptor T Cell Therapy in Hematological Malignancies

Chimeric antigen receptor T cell (CAR-T) therapy in hematologic malignancies has made great progress, but there are still some problems. First, T cells from tumor patients show an exhaustion phenotype; thus, the persistence and function of the CAR-Ts are poor, and achieving a satisfactory curative effect is difficult. Second, some patients initially respond well but quickly develop antigen-negative tumor recurrence. Thirdly, CAR-T treatment is not effective in some patients and is accompanied by severe side effects, such as cytokine release syndrome (CRS) and neurotoxicity. The solution to these problems is to reduce the toxicity and enhance the efficacy of CAR-T therapy. In this paper, we describe various strategies for reducing the toxicity and enhancing the efficacy of CAR-T therapy in hematological malignancies. In the first section, strategies for modifying CAR-Ts using gene-editing technologies or combining them with other anti-tumor drugs to enhance the efficacy of CAR-T therapy are introduced. The second section describes some methods in which the design and construction of CAR-Ts differ from the conventional process. The aim of these methods is to enhance the anti-tumor activity of CAR-Ts and prevent tumor recurrence. The third section describes modifying the CAR structure or installing safety switches to radically reduce CAR-T toxicity or regulating inflammatory cytokines to control the symptoms of CAR-T-associated toxicity. Together, the knowledge summarized herein will aid in designing better-suited and safer CAR-T treatment strategies.

CX3CR1 deficiency-induced TIL tumor restriction as a novel addition for CAR-T design in solid malignancies

Advances in the understanding of the tumor microenvironment have led to development of immunotherapeutic strategies, such as chimeric antigen receptor T cells (CAR-Ts). However, despite success in blood malignancies, CAR-T therapies in solid tumors have been hampered by their restricted infiltration. Here, we used our understanding of early cytotoxic lymphocyte infiltration of human lymphocytes in solid tumors in vivo to investigate the receptors in normal, adjacent, and tumor tissues of primary non-small-cell lung cancer specimens. We found that CX3CL1-CX3CR1 reduction restricts cytotoxic cells from the solid-tumor bed, contributing to tumor escape. Based on this, we designed a CAR-T construct using the well-established natural killer group 2, member D (NKG2D) CAR-T expression together with overexpression of CX3CR1 to promote their infiltration. These CAR-Ts infiltrate tumors at higher rates than control-activated T cells or IL-15-overexpressing NKG2D CAR-Ts. This construct also had similar functionality in a liver-cancer model, demonstrating potential efficacy in other solid malignancies.

Phenotypic and functional heterogeneity of monocytes in health and cancer in the era of high dimensional technologies

Monocytes have been traditionally classified in three discrete subsets, which can participate in the immune responses as effector cells or as precursors of myeloid-derived cells in circulation and tissues. However, recent advances in single-cell omics have revealed unprecedented phenotypic and functional heterogeneity that goes well beyond the three conventional monocytic subsets and propose a more fluid differentiation model. This novel concept does not only apply to the monocytes in circulation but also at the tissue site. Consequently, the binary model proposed for differentiating monocyte into M1 and M2 macrophages has been recently challenged by a spectrum model that more realistically mirrors the heterogeneous cues in inflammatory conditions. This review describes the latest results on the high dimensional characterization of monocytes and monocyte-derived myeloid cells in steady state and cancer. We discuss how environmental cues and monocyte-intrinsic properties may affect their differentiation toward specific functional and phenotypic subsets, the causes of monocyte expansion and reduction in cancer, their metabolic requirements, and the potential effect on tumor immunity.

Blockade of interleukin 10 potentiates antitumour immune function in human colorectal cancer liver metastases

OBJECTIVE

Programmed cell death protein 1 (PD-1) checkpoint inhibition and adoptive cellular therapy have had limited success in patients with microsatellite stable colorectal cancer liver metastases (CRLM). We sought to evaluate the effect of interleukin 10 (IL-10) blockade on endogenous T cell and chimeric antigen receptor T (CAR-T) cell antitumour function in CRLM slice cultures.

DESIGN

We created organotypic slice cultures from human CRLM (n=38 patients' tumours) and tested the antitumour effects of a neutralising antibody against IL-10 (αIL-10) both alone as treatment and in combination with exogenously administered carcinoembryonic antigen (CEA)-specific CAR-T cells. We evaluated slice cultures with single and multiplex immunohistochemistry, in situ hybridisation, single-cell RNA sequencing, reverse-phase protein arrays and time-lapse fluorescent microscopy.

RESULTS

αIL-10 generated a 1.8-fold increase in T cell-mediated carcinoma cell death in human CRLM slice cultures. αIL-10 significantly increased proportions of CD8⁺ T cells without exhaustion transcription changes, and increased human leukocyte antigen - DR isotype (HLA-DR) expression of macrophages. The antitumour effects of αIL-10 were reversed by major histocompatibility complex class I or II (MHC-I or MHC-II) blockade, confirming the essential role of antigen presenting cells. Interrupting IL-10 signalling also rescued murine CAR-T cell proliferation and cytotoxicity from myeloid cell-mediated immunosuppression. In human CRLM slices, αIL-10 increased CEA-specific CAR-T cell activation and CAR-T cell-mediated cytotoxicity, with nearly 70% carcinoma cell apoptosis across multiple human tumours. Pretreatment with an IL-10 receptor blocking antibody also potentiated CAR-T function.

CONCLUSION

Neutralising the effects of IL-10 in human CRLM has therapeutic potential as a stand-alone treatment and to augment the function of adoptively transferred CAR-T cells.

Current advances and challenges in CAR T-Cell therapy for solid tumors: tumor-associated antigens and the tumor microenvironment

The past decade has witnessed ongoing progress in immune therapy to ameliorate human health. As an emerging technique, chimeric antigen receptor (CAR) T-cell therapy has the advantages of specific killing of cancer cells, a high remission rate of cancer-induced symptoms, rapid tumor eradication, and long-lasting tumor immunity, opening a new window for tumor treatment. However, challenges remain in CAR T-cell therapy for solid tumors due to target diversity, tumor heterogeneity, and the complex microenvironment. In this review, we have outlined the development of the CAR T-cell technique, summarized the current advances in tumor-associated antigens (TAAs), and highlighted the importance of tumor-specific antigens (TSAs) or neoantigens for solid tumors. We also addressed the challenge of the TAA binding domain in CARs to overcome off-tumor toxicity. Moreover, we illustrated the dominant tumor microenvironment (TME)-induced challenges and new strategies based on TME-associated antigens (TMAs) for solid tumor CAR T-cell therapy.

Bright future or blind alley? CAR-T cell therapy for solid tumors

Chimeric antigen receptor (CAR) T cells therapy has emerged as a significant breakthrough in adoptive immunotherapy for hematological malignancies with FDA approval. However, the application of CAR-T cell therapy in solid tumors remains challenging, mostly due to lack of suitable CAR-T target antigens, insufficient trafficking and extravasation to tumor sites, and limited CAR-T survival in the hostile tumor microenvironment (TME). Herein, we reviewed the development of CARs and the clinical trials in solid tumors. Meanwhile, a "key-and-lock" relationship was used to describe the recognition of tumor antigen via CAR T cells. Some strategies, including dual-targets and receptor system switches or filter, have been explored to help CAR T cells matching targets specifically and to minimize on-target/off-tumor toxicities in normal tissues. Furthermore, the complex TME restricts CAT T cells activity through dense extracellular matrix, suppressive immune cells and cytokines. Recent innovations in engineered CARs to shield the inhibitory signaling molecules were also discussed, which efficiently promote CAR T functions in terms of expansion and survival to overcome the hurdles in the TME of solid tumors.

Insights into the tumor microenvironment of B cell lymphoma

The standard therapies in lymphoma have predominantly focused on targeting tumor cells with less of a focus on the tumor microenvironment (TME), which plays a critical role in favoring tumor growth and survival. Such an approach may result in increasingly refractory disease with progressively reduced responses to subsequent treatments. To overcome this hurdle, targeting the TME has emerged as a new therapeutic strategy. The TME consists of T and B lymphocytes, tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), cancer-associated fibroblasts (CAFs), and other components. Understanding the TME can lead to a comprehensive approach to managing lymphoma, resulting in therapeutic strategies that target not only cancer cells, but also the supportive environment and thereby ultimately improve survival of lymphoma patients. Here, we review the normal function of different components of the TME, the impact of their aberrant behavior in B cell lymphoma and the current TME-direct therapeutic avenues.

Overcoming biophysical barriers with innovative therapeutic delivery approaches

Cancer is often conceptualized as principally a cellular process, one initiated by genetic mutations in a progenitor cell that result in dysregulated cell proliferation. Accordingly, investigations into mechanisms of treatment resistance to cancer therapies often revolve around the biologic barriers to the therapies. However, there is a growing appreciation for the unique biomechanical properties for tumors and the role they play in treatment resistance for conventional, molecularly targeted, and immune-mediated cancer therapies. This understanding has inspired the development of pharmacologic and interventional approaches to overcome these barriers. Of particular promise are perfusion-enhanced drug delivery (PEDD) approaches that potentially allow for comprehensive tumor coverage with increased delivery pressure and prevention of reflux to drive therapeutics into the tumor parenchyma. In this review, we summarize the key features of the tumor microenvironment that drive tumor progression and impose barriers to anti-cancer therapies. We highlight the rationale and application of pharmacologic approaches and interventional drug delivery devices designed to overcome these impediments. We additionally contextualize these concepts by illustrating their application to the treatment of uveal melanoma liver metastases.

Advances and Hurdles in CAR T Cell Immune Therapy for Solid Tumors

Chimeric antigen receptor (CAR) T cells in solid tumors have so far yielded limited results, in terms of therapeutic effects, as compared to the dramatic results observed for hematological malignancies. Many factors involve both the tumor cells and the microenvironment. The lack of specific target antigens and severe, potentially fatal, toxicities caused by on-target off-tumor toxicities constitute major hurdles. Furthermore, the tumor microenvironment is usually characterized by chronic inflammation, the presence of immunosuppressive molecules, and immune cells that can reduce CAR T cell efficacy and facilitate antigen escape. Nonetheless, solid tumors are under investigation as possible targets despite their complexity, which represents a significant challenge. In preclinical mouse models, CAR T cells are able to efficiently recognize and kill several tumor xenografts. Overall, in the next few years, there will be intensive research into optimizing novel cell therapies to improve their effector functions and keep untoward effects in check. In this review, we provide an update on the state-of-the-art CAR T cell therapies in solid tumors, focusing on the preclinical studies and preliminary clinical findings aimed at developing optimal strategies to reduce toxicity and improve efficacy.

The tumor microenvironment of hepatocellular carcinoma and its targeting strategy by CAR-T cell immunotherapy

Hepatocellular carcinoma (HCC) is the major subtype of liver cancer, which ranks sixth in cancer incidence and third in mortality. Although great strides have been made in novel therapy for HCC, such as immunotherapy, the prognosis remains less than satisfactory. Increasing evidence demonstrates that the tumor immune microenvironment (TME) exerts a significant role in the evolution of HCC and has a non-negligible impact on the efficacy of HCC treatment. In the past two decades, the success in hematological malignancies made by chimeric antigen receptor-modified T (CAR-T) cell therapy leveraging it holds great promise for cancer treatment. However, in the face of a hostile TME in solid tumors like HCC, the efficacy of CAR-T cells will be greatly compromised. Here, we provide an overview of TME features in HCC, discuss recent advances and challenges of CAR-T immunotherapy in HCC.

Understanding CAR T cell-tumor interactions: Paving the way for successful clinical outcomes

Since their approval 5 years ago, chimeric antigen receptor (CAR) T cells have gained great importance in the daily clinical practice and treatment of hematological malignancies, although many challenges to their use remain, such as limited long-term CAR T cell efficacy due to disease resistance or recurrence. After a brief overview of CAR T cells, their approval, therapeutic successes, and ongoing limitations, this review discusses what is known about CAR T cell activation, their expansion and persistence, their mechanisms of cytotoxicity, and how the CAR design and/or tumor-intrinsic factors influence these functions. This review also examines the role of cytokines in CAR T cell-associated toxicity and their effects on CAR T cell function. Furthermore, we discuss several resistance mechanisms, including obstacles associated with CAR treatment of solid tumors. Finally, we provide a future outlook on next-generation strategies to further optimize CARs and improve clinical outcomes.

Engineered Microphysiological Systems for Testing Effectiveness of Cell-Based Cancer Immunotherapies

Cell therapies, including adoptive immune cell therapies and genetically engineered chimeric antigen receptor (CAR) T or NK cells, have shown promise in treating hematologic malignancies. Yet, immune cell infiltration and expansion has proven challenging in solid tumors due to immune cell exclusion and exhaustion and the presence of vascular barriers. Testing next-generation immune therapies remains challenging in animals, motivating sophisticated ex vivo models of human tumor biology and prognostic assays to predict treatment response in real-time while comprehensively recapitulating the human tumor immune microenvironment (TIME). This review examines current strategies for testing cell-based cancer immunotherapies using ex vivo microphysiological systems and microfluidic technologies. Insights into the multicellular interactions of the TIME will identify novel therapeutic strategies to help patients whose tumors are refractory or resistant to current immunotherapies. Altogether, these microphysiological systems (MPS) have the capability to predict therapeutic vulnerabilities and biological barriers while studying immune cell infiltration and killing in a more physiologically relevant context, thereby providing important insights into fundamental biologic mechanisms to expand our understanding of and treatments for currently incurable malignancies.

Orthotopic and Heterotopic Murine Models of Pancreatic Cancer Exhibit Different Immunological Microenvironments and Different Responses to Immunotherapy

For decades, tumor-bearing murine models established using tumor cell lines have been the most commonly used models to study human cancers. Even though there are several studies reported that implant sites caused disparities in tumor behaviors, few of them illuminated the positional effect on immunotherapy. Herein, we describe surgical techniques for a novel orthotopic implantation of syngeneic pancreatic ductal adenocarcinoma (PDAC) tissue slices. This method has a high success modeling rate and stable growth kinetics, which makes it useful for testing novel therapeutics. Pathological examination indicated that the orthotopic tumor displayed poor vascularization, desmoplastic stromal reaction, and a highly immunosuppressive tumor microenvironment. This unique microenvironment resulted in limited response to PD1/CTLA4 blockade therapy and anti-MUC1 (αMUC1) CAR-T transfer treatment. To reverse the suppressive tumor microenvironment, we developed gene modified T-cells bearing a chimeric receptor in which activating receptor NKG2D fused to intracellular domains of 4-1BB and CD3ζ (NKG2D CAR). The NKG2D CAR-T cells target myeloid-derived suppressor cells (MDSCs), which overexpress Rae1 (NKG2D ligands) within the TME. Results indicated that NKG2D CAR-T cells eliminated MDSCs and improved antitumor activity of subsequently infused CAR-T cells. Moreover, we generated a bicistronic CAR-T, including αMUC1 CAR and NKG2D CAR separated by a P2A element. Treatment with the dual targeted bicistronic CAR-T cells also resulted in prolonged survival of orthotopic model mice. In summary, this study describes construction of a novel orthotopic PDAC model through implantation of tissue slices and discusses resistance to immunotherapy from the perspective of a PDAC microenvironment. Based on the obtained results, it is evident that elimination MDSCs by NKG2D CAR could rescue the impaired CAR-T cell activity.

Current State of Cell Therapies for Gastrointestinal Cancers

ABSTRACT

Adoptive cell therapies include multiple cell-based therapies to harness the immune system's power to mount a robust anticancer effect. Early successes in solid tumors with checkpoint inhibition have increased the research and development of immunotherapy. The utilization of cell-based therapy for gastrointestinal malignancies is still in its infancy because of challenges of antigen specificity and access to the tumor microenvironment. In this review, we discuss the current state of adoptive cell therapies in terms of challenges and early successes in preclinical and clinical studies.

CAR T Cell Therapy in Hematological Malignancies: Implications of the Tumor Microenvironment and Biomarkers on Efficacy and Toxicity

Chimeric antigen receptor (CAR) T cell therapy has ushered in a new era in cancer treatment. Remarkable outcomes have been demonstrated in patients with previously untreatable relapsed/refractory hematological malignancies. However, optimizing efficacy and reducing the risk of toxicities have posed major challenges, limiting the success of this therapy. The tumor microenvironment (TME) plays an important role in CAR T cell therapy’s effectiveness and the risk of toxicities. Increasing research studies have also identified various biomarkers that can predict its effectiveness and risk of toxicities. In this review, we discuss the various aspects of the TME and biomarkers that have been implicated thus far and discuss the role of creating scoring systems that can aid in further refining clinical applications of CAR T cell therapy and establishing a safe and efficacious personalised medicine for individuals.