Enhancing CAR T-cell therapy through cellular imaging and radiotherapy

An Implantable Double-Layered Spherical Scaffold Depositing Gene and Cell Agents to Facilitate Collaborative Cancer Immunotherapy

Gene therapies and adoptive cell therapy (ACT) are promising strategies for cancer immunotherapy. Referring to their different mechanisms, the combination of these two might result in a strategy with potential collaborative and compensatory effects. However, it is challenging to combine gene therapies and ACT that work in a proper logical order. Here, we developed a double-layered spherical scaffold (DLS) to codeliver mRNA and T cells and constructed an implantable hydrogel formulation, named the GD-920 scaffold. With a diameter of 7 mm, this scaffold loaded primary T cells in the inner layer and the Bim mRNA nanocomplex in the outer layer. While maintaining their bioactivities, GD-920 released gene and cell payloads in a controllable and sequential manner. The mRNA complex from the outer layer was first released and induced immunogenic tumor cell death. The produced antigens then migrated into the scaffold with dendritic cells, triggering a tumor-specific immune response. Finally, activated T cells released by the inner layer attacked the tumor tissue via massive infiltration. We showed that in situ implantation of the GD-920 scaffold is capable of effectively inhibiting tumor growth and is far more potent than that of control scaffolds containing a single payload. Our results demonstrated the outstanding potential of this DLS in combining gene and cell therapeutic approaches to cancer immunotherapy.

Whole brain radiotherapy combined with CART-cell therapy for relapsed/refractory central nervous system B-cell lymphoma

Relapsed or refractory central nervous system B-cell lymphoma (r/r CNS-BL), including primary central nervous system lymphoma (PCNSL) and secondary central nervous system lymphoma (SCNSL), remains a significant therapeutic challenge with limited treatment options and poor prognosis. This study investigated the combination of whole-brain radiotherapy (WBRT) and chimeric antigen receptor T-cell (CAR-T) therapy in 27 r/r CNS-BL patients. Peripheral blood mononuclear cells were collected before radiotherapy to prepare CAR-T cells. Patients then received whole-brain radiotherapy (WBRT), with or without local boost, followed by CAR-T cell infusion at least one week after radiotherapy completion. Post-CAR-T therapy, the optimal objective response rate (ORR) increased to 88.9%, and the optimal CR rate reached 85.2%. With a median follow-up of 12 months, the median progression-free survival (PFS) and overall survival (OS) were not reached (NR), and the 1-year estimated PFS and OS rate were 61.3% and 56.6%, respectively. Cytokine release syndrome (CRS) occurred in 48.1% of patients. Immune effector cell-associated neurotoxicity syndrome (ICANS) was observed in 29.6% of patients, with only 3.7% on grade 4, all of whom recovered after treatment. This study demonstrates that the combination of WBRT and CAR-T therapy offers a promising therapeutic strategy for r/r CNS-BL patients, improving remission rates and providing a well-tolerated treatment option.

In Vivo Ultrasound and Photoacoustic Imaging of Nanoparticle-Engineered T Cells and Post-Treatment Assessment to Guide Adoptive Cell Immunotherapy

Despite great promise, adoptive cell therapy (ACT) continues to fail at treating a majority of cancers, especially solid tumors. To inform development and expedite the translation of more potent cellular immunotherapies, advanced immunoimaging tools are needed to better understand the in vivo requirements for generating a robust immune response. Even methods to evaluate the delivery, location, and status of transferred T cells at the tumor target are lacking. Therefore, a real-time, safe, noninvasive, longitudinal imaging method is critically needed to 1) monitor adoptive T cell location and status and 2) assess treatment progression and response through imaging biomarkers. Here, we developed a combined ultrasound (US) and photoacoustic (PA) imaging approach to enable T cell tracking following adoptive transfer for cancer immunotherapy. Our approach leverages highly photostable gold nanorods and cell surface engineering to tag the T cells without impacting effector functions, as well as generate PA contrast for imaging post-transfer. Our in vivo US/PA imaging approach detected nanoparticle-labeled T cell accumulation at the tumor, visualized changes in tumor volume, and conveyed accompanying changes in blood biomarkers. US/PA data also showed different trends according to a positive or negative antitumor response to T cell therapy over 7 days. Results highlight the potential of the approach and motivate future development to expand the platform for advanced, theranostic immunoimaging.

CAR-T therapy for endocrine neoplasms: novel targets and combination of therapies

Endocrine malignancies constitute a heterogeneous tumour group with diverse biological characteristics. While typically indolent, they encompass aggressive types and presence of any metastatic sign indicates a high probability of recurrence and a diminished response to conventional therapies. Chimeric antigen receptor (CAR)-T cell immunotherapy has constituted a revolutionary advance in cancer treatment and exhibited significant potential for application in endocrine cancer. However, limited effectiveness was displayed in clinical application, which necessitates the exploration of novel modalities. Identification of specific and safe targets for endocrine cancer is the initial stage towards establishing a successful CAR-T treatment. Various therapies under investigation offer potential enhancements to CAR T cell efficacy through diverse mechanisms. Herein, we summarize recent advances in identifying targets of endocrine cancer for CAR therapy and provide an overview of combinatorial approaches.

STING Agonist Delivered by Neutrophil Membrane-Coated Gold Nanoparticles Exerts Synergistic Tumor Inhibition with Radiotherapy

Radiotherapy (RT) is one of the major treatments for cancers and a promising initiator of immune response. Gold nanoparticles are a promising radiosensitizer. In this study, we sought to optimize the drug delivery efficiency of gold nanoparticles and explore their function in delivering stimulator of interferon genes (STING) agonists with or without RT. Gold nanoparticles covalent to MSA-2 (MSA-Au) were mixed with cRGD-modified neutrophil membranes to obtain M-Au@RGD-NM. We explored the treatment efficiency of M-Au@RGD-NM combined with RT. Immune cell regulation and STING pathway activation were detected. We successfully prepared M-Au@RGD-NM with significant tumor suppression by induction of ROS and the resulting DNA damage. In vivo dynamic imaging showed that M-Au@RGD-NM was mainly targeted to radiated tumors. Tumor-bearing mice showed significant tumor inhibition following a combination therapy. M-Au@RGD-NM significantly activated the STING pathway and regulated the whole-body immune response. Locally radiated tumors showed dendritic cells mature, CD8+ T cells upregulation, and M1 polarization, with systematic immune response demonstrated by CD8+ T cell infiltration in abscopal tumors. In this study, we synthesized M-Au@RGD-NM loading MSA-2. Following characterization, we found that RT-based M-Au@RGD-NM treatment achieved good antitumor effects, tumor RT enhancement, and induction of an immune response via STING activation.

Acidity-targeting transition-aided universal chimeric antigen receptor T-cell (ATT-CAR-T) therapy for the treatment of solid tumors

The use of CAR-T cells in treating solid tumors frequently faces significant challenges, mainly due to the heterogeneity of tumor antigens. This study assessed the efficacy of an acidity-targeting transition-aided universal chimeric antigen receptor T (ATT-CAR-T) cell strategy, which is facilitated by an acidity-targeted transition. Specifically, the EGFRvIII peptide was attached to the N-terminus of a pH-low insertion peptide. Triggered by the acidic conditions of the tumor microenvironment, this peptide alters its structure and selectively integrates into the membrane of solid tumor cells. The acidity-targeted transition component effectively relocated the EGFRvIII peptide across various tumor cell membranes; thus, allowing the direct destruction of these cells by EGFRvIII-specific CAR-T cells. This method was efficient even when endogenous antigens were absent. In vivo tests showed marked antigen modification within the acidic tumor microenvironment using this component. Integrating this component with CAR-T cell therapy showed high effectiveness in combating solid tumors. These results highlight the capability of ATT-CAR-T cell therapy to address the challenges presented by tumor heterogeneity and expand the utility of CAR-T cell therapy in the treatment of solid tumors.

Role of radiation in chimeric antigen receptor T-cell therapy for patients with relapsed/refractory non-Hodgkin lymphoma: Current studies and future prospects

Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment approach for patients with relapsed/refractory non-Hodgkin lymphoma (R/R NHL). However, the long-term prognosis has been discouraging. Moreover, the urgent resolution of two critical issues is necessary: minimize tumor burden before CAR-T infusion and control fatal toxicities post CAR-T therapy. By combining radiotherapy (RT), the safety and efficacy of CAR-T can be improved. RT can serve as bridging therapy, reducing the tumor burden before CAR-T infusion, thus enabling safe and successful CAR-T infusion, and as salvage therapy in cases of CAR-T therapy failure. This review aims to discuss the current evidence supporting the use of RT in CAR-T therapy for patients with R/R NHL. Although most studies have shown a positive role of RT in combined modality treatments for patients undergoing CAR-T therapy, the synergy gained from these remains uncertain. Furthermore, the optimal dose/fraction and radiation response require further investigation.

Efficient combination of radiotherapy and CAR-T - A systematic review

Chimeric antigen receptor T (CAR-T) cell therapy, a groundbreaking immunotherapy. However, it faces formidable challenges in treating solid tumors, grappling with issues like poor trafficking, limited penetration, and insufficient persistence within the tumor microenvironment (TME). CAR-T cells are engineered to express receptors that target specific cancer antigens, enhancing their ability to recognize and eliminate cancer cells. This review paper explores the intricate interplay between CAR-T therapy and radiotherapy (RT), investigating their synergistic potential. Radiotherapy, a standard cancer treatment, involves using high doses of radiation to target and damage cancer cells, disrupting their ability to grow and divide. We highlight that RT modulates the TME, augments antigen presentation, and promotes immune cell infiltration, bolstering CAR-T cell-mediated tumor eradication. Molecular insights shed light on RT-induced alterations in tumor stroma, T cell recruitment promotion, and induction of immunogenic cell death. Noteworthy, strategies, such as combining hypofractionated radiotherapy with myeloid-derived suppressor cell blockade, underscore innovative approaches to enhance CAR-T cell therapy in solid tumors. Bridging indications for RT and CAR-T cells in hematological malignancies are discussed, emphasizing scenarios where RT strategically enhances CAR-T cell efficacy. The paper critically evaluates the RT as a bridge compared to traditional chemotherapy, highlighting timing and dosage considerations crucial for optimizing CAR-T therapy outcomes. In summary, the paper provides valuable insights into the intricate molecular mechanisms activated by RT and innovative strategies to improve CAR-T cell therapy, fostering a deeper understanding of their combined potential in cancer treatment.

Noninvasive longitudinal PET/CT imaging of CAR T cells using PSMA reporter gene

PURPOSE

Chimeric antigen receptor (CAR) T cell therapy has achieved great success in treating hematologic malignancies. However, it is yet to prove effective in the treatment of solid tumors. Thus, it is necessary to develop appropriate methodology for the long-term, accurate, and quantitative evaluation of the distribution and activities of CAR T cells in solid tumors. In the present study, we engineered TfR ΔPSMA CAR (CAR-ΔPSMA) T cells, which targeted the transferrin receptor (TfR) expressed by tumor cells and could be tracked in vivo via a reporter gene encoding the truncated prostate specific membrane antigen (ΔPSMA). We then quantitatively monitored these CAR T cells in vitro and in vivo using [68Ga]Ga-PSMA-617 positron emission tomography (PET)/computed tomography (CT).

METHODS

The CAR-ΔPSMA T cells were genetically engineered by transducing T cells with a lentiviral vector encoding TfR41BBζ-T2A-ΔPSMA. Firstly, the target expression, activation, and cytotoxicity of CAR-ΔPSMA T cells were validated in vitro. Secondly, the minimum thresholds of CAR-ΔPSMA T cells detection for [68Ga]Ga-PSMA-617 PET/CT were also determined in vitro and in vivo respectively. Lastly, the feasibility of monitoring the biodistribution and infiltration of CAR-ΔPSMA T cells after systematic administration was evaluated in the breast cancer subcutaneous xenograft model.

RESULTS

The CAR-ΔPSMA T cells retained activation and tumor killing capacity after transduction of the ΔPSMA-encoding reporter gene. Next, the CAR-ΔPSMA T cells could be reliably tracked by [68Ga]Ga-PSMA-617 PET/CT, the detection sensitivity of which was 250 cells/mm3 in vitro and 100 cells/mm3 in vivo. Next, the sequential imaging assays revealed that [68Ga]Ga-PSMA-617 PET/CT could be used to specifically visualize ΔPSMA+ CAR T cells at the tumor site. The increase in the [68Ga]Ga-PSMA-617 signal intensity over time allowed us to effectively detect CAR T cells in vivo.

CONCLUSION

Our findings preliminarily confirmed that [68Ga]Ga-PSMA-617 PET/CT could reliably detect CAR-ΔPSMA T cells in vitro and in vivo in solid tumors, laying the foundation for the monitoring CAR T cell therapy in the future.

Construction of truncated PSMA as a PET reporter gene for CAR T cell trafficking

In solid tumors, there are multiple barriers for a chimeric antigen receptor (CAR) T cell to surmount in order to reach the tumor site. For better understanding whether CAR T cells effectively infiltrate into tumor site, and simultaneously, whether there are off-target effects, real-time monitoring technologies need to be established. Cell-based positron emission tomography reporter genes have been developed to monitor engineered cells in living subjects. In this study, we reported the construction of a novel reporter gene truncated prostate-specific membrane antigen (ΔPSMA) pending for monitoring CAR T cells using 68Ga-PSMA-617 and a method for tracking the distribution of CAR T cells in vivo was developed. Data were provided to demonstrate that ΔPSMA was predominantly localized on the plasma membrane and could take up 68Ga-PSMA-617 in vitro in a time-dependent manner. And the expression of ΔPSMA did not affect CAR expression and cytolytic capacity of CAR T cells. CAR-ΔPSMA T cell xenografts in nude mice were clearly imaged by positron emission tomography 60 min after injection of 68Ga-PSMA-617. PSMA paired with 68Ga-PSMA-617 was capable of identifying approximately 1 × 104 engineered CAR T cells. The ability to image small numbers of CAR T cells in vivo would be helpful to accelerate the translation of cell-based therapies into the clinic, and it may reinforce our understanding of treatment success, failure, and toxicity.

Evolving CAR-T-Cell Therapy for Cancer Treatment: From Scientific Discovery to Cures

In recent years, chimeric antigen receptor (CAR)-T-cell therapy has emerged as the most promising immunotherapy for cancer that typically uses patients' T cells and genetically engineered them to target cancer cells. Although recent improvements in CAR-T-cell therapy have shown remarkable success for treating hematological malignancies, the heterogeneity in tumor antigens and the immunosuppressive nature of the tumor microenvironment (TME) limits its efficacy in solid tumors. Despite the enormous efforts that have been made to make CAR-T-cell therapy more effective and have minimal side effects for treating hematological malignancies, more research needs to be conducted regarding its use in the clinic for treating various other types of cancer. The main concern for CAR-T-cell therapy is severe toxicities due to the cytokine release syndrome, whereas the other challenges are associated with complexity and immune-suppressing TME, tumor antigen heterogeneity, the difficulty of cell trafficking, CAR-T-cell exhaustion, and reduced cytotoxicity in the tumor site. This review discussed the latest discoveries in CAR-T-cell therapy strategies and combination therapies, as well as their effectiveness in different cancers. It also encompasses ongoing clinical trials; current challenges regarding the therapeutic use of CAR-T-cell therapy, especially for solid tumors; and evolving treatment strategies to improve the therapeutic application of CAR-T-cell therapy.

A synthetic notch (synNotch) system linking intratumoral immune-cancer cell communication to a synthetic blood biomarker assay

Introduction: Cellular immunotherapy has greatly improved cancer treatment in recent years. For instance, chimeric antigen receptor (CAR) T cell therapy has been proven highly effective in treating hematological malignancies, and many CAR cell designs are being explored for solid tumors. However, many questions remain why responses differ across patients and some tumor types are resistant. Improved and relatively inexpensive ways to monitor these cells could provide some answers. Clinically, blood tests are regularly used to monitor these therapies, but blood signals often do not reflect the activity of immune cells within the tumor(s). Here, using the synthetic Notch (synNotch) receptor that tethers antigen binding to customized transgene expression, we linked intratumoral immune-cancer cell communication to a simple secreted reporter blood test. Specifically, we engineered immune cells with a CD19-targeted synNotch receptor and demonstrated that binding to CD19 on cancer cells in vivo resulted in the production of secreted embryonic alkaline phosphatase (SEAP) at levels that are readily detected in the blood. Methods and Results: Jurkat T cells were engineered via sequential lentiviral transduction of two components: an anti-CD19 synNotch receptor and a synNotch response element encoding SEAP. Co-culture of engineered cells with CD19+, but not CD19-, Nalm6 cells, resulted in significantly elevated SEAP in media. Nod-scid-gamma (NSG) mice were subcutaneously injected with either CD19+ or CD19- Nalm6 cells. Intratumoral injection of engineered T cells (1x107) resulted in significantly elevated blood SEAP activity in mice bearing CD19+ tumors (n = 7), but not CD19- tumors (n = 5). Discussion: Our synNotch reporter system allows for the monitoring of antigen-dependent intratumoral immune-cancer cell interactions through a simple and convenient blood test. Continued development of this system for different target antigens of interest should provide a broadly applicable platform for improved monitoring of many cell-based immunotherapies during their initial development and clinical translation, ultimately improving our understanding of design considerations and patient-specific responses.

Noncanonical MAVS signaling restrains dendritic cell-driven antitumor immunity by inhibiting IL-12

Mitochondrial antiviral signaling protein (MAVS)-mediated cytosolic RNA sensing plays a central role in tumor immunogenicity. However, the effects of host MAVS signaling on antitumor immunity remain unclear. Here, we demonstrate that the host MAVS pathway supports tumor growth and impairs antitumor immunity, whereas MAVS deficiency in dendritic cells (DCs) promotes tumor-reactive CD8+ T cell responses. Specifically, CD8+ T cell priming capacity was enhanced by MAVS ablation in a type I interferon-independent, but IL-12-dependent, manner. Mechanistically, loss of the RIG-I/MAVS cascade activated the noncanonical NF-κB pathway and in turn induced IL-12 production by DCs. MAVS-restrained IL-12 promoted cross-talk between CD8+ T cells and DCs, which was licensed by IFN-γ. Moreover, ablation of host MAVS sensitized tumors to immunotherapy and attenuated radiation resistance, thereby facilitating the maintenance of effector CD8+ T cells. These findings demonstrate that the host MAVS pathway acts as an immune regulator of DC-driven antitumor immunity and support the development of immunotherapies that antagonize MAVS signaling in DCs.

Chimeric antigen receptor-modified T cells therapy in prostate cancer: A comprehensive review on the current state and prospects

Recent immunotherapy research has focused on chimeric antigen receptor-modified T cells (CAR-Ts). CAR-T therapies have been clinically applied to manage hematologic malignancies with satisfactory effectiveness. However, the application of CAR-T immunotherapy in solid tumors remains challenging. Even so, current CAR-T immunotherapies for prostate cancer (PCa) have shown some promise, giving hope to patients with advanced metastatic PCa. This review aimed to elucidate different types of prostate tumor-associated antigen targets, such as prostate-specific membrane antigen and prostate stem cell antigen, and their effects. The current status of the corresponding targets in clinical research through their applications was also discussed. To improve the efficacy of CAR-T immunotherapy, we addressed the possible applications of multimodal immunotherapy, chemotherapy, and CAR-T combined therapies. The obstacles of solid tumors were concisely elaborated. Further studies should aim to discover novel potential targets and establish new models by overcoming the inherent barriers of solid tumors, such as tumor heterogeneity and the immunosuppressive nature of the tumor microenvironment.

Optimized CAR-T therapy based on spatiotemporal changes and chemotactic mechanisms of MDSCs induced by hypofractionated radiotherapy

Poor intratumoral infiltration is the major challenge for chimeric antigen receptor (CAR)-T cell therapy in solid tumors. Hypofractionated radiotherapy (HFRT) has been reported to induce immune cell infiltration and reshape the tumor immune microenvironment. Here, we showed that HFRT (5 × 5 Gy) mediated an early accumulation of intratumoral myeloid-derived suppressor cells (MDSCs) and decreased infiltration of T cells in the tumor microenvironment (TME) of immunocompetent mice bearing triple-negative breast cancer (TNBC) or colon cancer, which was further confirmed in tumors from patients. RNA sequencing (RNA-seq) and cytokine profiling analysis revealed that HFRT induced the activation and proliferation of tumor-infiltrated MDSCs, which was mediated by the interactions of multiple chemokines and chemokine receptors. Further investigation showed that when combined with HFRT, CXCR2 blockade significantly inhibited MDSCs trafficking to tumors and effectively enhanced the intratumoral infiltration and treatment efficacy of CAR-T cells. Our study demonstrates that MDSCs blockade combined with HFRT is promising for CAR-T cell therapy optimization in solid tumors.

Combination of CAR‑T cell therapy and radiotherapy: Opportunities and challenges in solid tumors (Review)

Chimeric antigen receptor (CAR) T cell therapy has emerged as a new and breakthrough cancer immunotherapy. Although CAR-T cell therapy has made significant progress clinically in patients with refractory or drug-resistant hematological malignancies, there are numerous challenges in its application to solid tumor therapy, including antigen escape, severe toxic reactions, abnormal vascularization, tumor hypoxia, insufficient infiltration of CAR-T cells and immunosuppression. As a conventional mode of anti-tumor therapy, radiotherapy has shown promising effects in combination with CAR-T cell therapy by enhancing the specific immunity of endogenous target antigens, which promoted the infiltration and expansion of CAR-T cells and improved the hypoxic tumor microenvironment. This review focuses on the obstacles to the application of CAR-T technology in solid tumor therapy, the potential opportunities and challenges of combined radiotherapy and CAR-T cell therapy, and the review of recent literature to evaluate the best combination for the treatment of solid tumors.

Current and potential roles of immuno-PET/-SPECT in CAR T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapies have evolved as breakthrough treatment options for the management of hematological malignancies and are also being developed as therapeutics for solid tumors. However, despite the impressive patient responses from CD19-directed CAR T-cell therapies, ~ 40%-60% of these patients' cancers eventually relapse, with variable prognosis. Such relapses may occur due to a combination of molecular resistance mechanisms, including antigen loss or mutations, T-cell exhaustion, and progression of the immunosuppressive tumor microenvironment. This class of therapeutics is also associated with certain unique toxicities, such as cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and other "on-target, off-tumor" toxicities, as well as anaphylactic effects. Furthermore, manufacturing limitations and challenges associated with solid tumor infiltration have delayed extensive applications. The molecular imaging modalities of immunological positron emission tomography and single-photon emission computed tomography (immuno-PET/-SPECT) offer a target-specific and highly sensitive, quantitative, non-invasive platform for longitudinal detection of dynamic variations in target antigen expression in the body. Leveraging these imaging strategies as guidance tools for use with CAR T-cell therapies may enable the timely identification of resistance mechanisms and/or toxic events when they occur, permitting effective therapeutic interventions. In addition, the utilization of these approaches in tracking the CAR T-cell pharmacokinetics during product development and optimization may help to assess their efficacy and accordingly to predict treatment outcomes. In this review, we focus on current challenges and potential opportunities in the application of immuno-PET/-SPECT imaging strategies to address the challenges encountered with CAR T-cell therapies.

Nuclear Imaging of CAR T Immunotherapy to Solid Tumors: In Terms of Biodistribution, Viability, and Cytotoxic Effect

Immunotherapy has become a mainstay of cancer therapy. Since chimeric antigen receptor (CAR) T immunotherapy achieves unprecedented success in curing hematological malignancies, the possibility of it revolutionizing the paradigm of solid tumors has aroused increasing attention. However, the restricted accessibility to tumor parenchyma, the immunosuppressive tumor microenvironment, and antigen heterogeneity of solid tumors make it difficult to replicate its success. Therefore, dynamic evaluation of CAR T cells' tumor accessibility, intratumoral viability, and anti-tumor cytotoxicity is necessary to facilitate its translation to solid tumors. Besides, real-timely imaging above events in vivo can help evaluate therapeutic responses and optimize CAR T immunotherapy for solid tumors. Nuclear imaging, including positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging, is frequently applied for evaluating adoptive cell therapies owing to its excellent sensitivity, high tissue penetration, and great translation potential. In addition, quantitative analysis can be performed in dynamic and noninvasive patterns. This review focuses on recent advances in PET/SPECT technologies and imaging probes in monitoring CAR T cells' migration, viability, and cytotoxicity to solid tumors post-administration. Prospects of what should be done in the next stage to promote CAR T therapy's application in solid tumors are also discussed.

Nanomedicine embraces cancer radio-immunotherapy: mechanism, design, recent advances, and clinical translation

Cancer radio-immunotherapy, integrating external/internal radiation therapy with immuno-oncology treatments, emerges in the current management of cancer. A growing number of pre-clinical studies and clinical trials have recently validated the synergistic antitumor effect of radio-immunotherapy, far beyond the "abscopal effect", but it suffers from a low response rate and toxicity issues. To this end, nanomedicines with an optimized design have been introduced to improve cancer radio-immunotherapy. Specifically, these nanomedicines are elegantly prepared by incorporating tumor antigens, immuno- or radio-regulators, or biomarker-specific imaging agents into the corresponding optimized nanoformulations. Moreover, they contribute to inducing various biological effects, such as generating in situ vaccination, promoting immunogenic cell death, overcoming radiation resistance, reversing immunosuppression, as well as pre-stratifying patients and assessing therapeutic response or therapy-induced toxicity. Overall, this review aims to provide a comprehensive landscape of nanomedicine-assisted radio-immunotherapy. The underlying working principles and the corresponding design strategies for these nanomedicines are elaborated by following the concept of "from bench to clinic". Their state-of-the-art applications, concerns over their clinical translation, along with perspectives are covered.

Radiotherapy as a means to increase the efficacy of T-cell therapy in solid tumors

Chimeric antigen receptor (CAR)-T cells have demonstrated significant improvements in the treatment of refractory B-cell malignancies that previously showed limited survival. In contrast, early-phase clinical studies targeting solid tumors have been disappointing. This may be due to both a lack of specific and homogeneously expressed targets at the surface of tumor cells, as well as intrinsic properties of the solid tumor microenvironment that limit homing and activation of adoptive T cells. Faced with these antagonistic conditions, radiotherapy (RT) has the potential to change the overall tumor landscape, from depleting tumor cells to reshaping the tumor microenvironment. In this article, we describe the current landscape and discuss how RT may play a pivotal role for enhancing the efficacy of adoptive T-cell therapies in solid tumors. Indeed, by improving homing, expansion and activation of infused T cells while reducing tumor volume and heterogeneity, the use of RT could help the implementation of engineered T cells in the treatment of solid tumors.

CAR-T cell combination therapy: the next revolution in cancer treatment

In recent decades, the advent of immune-based therapies, most notably Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment. The promising results of numerous studies indicate that CAR-T cell therapy has had a remarkable ability and successful performance in treating blood cancers. However, the heterogeneity and immunosuppressive tumor microenvironment (TME) of solid tumors have challenged the effectiveness of these anti-tumor fighters by creating various barriers. Despite the promising results of this therapeutic approach, including tumor degradation and patient improvement, there are some concerns about the efficacy and safety of the widespread use of this treatment in the clinic. Complex and suppressing tumor microenvironment, tumor antigen heterogeneity, the difficulty of cell trafficking, CAR-T cell exhaustion, and reduced cytotoxicity in the tumor site limit the applicability of CAR-T cell therapy and highlights the requiring to improve the performance of this treatment. With this in mind, in the last decade, many efforts have been made to use other treatments for cancer in combination with tuberculosis to increase the effectiveness of CAR-T cell therapy, especially in solid tumors. The combination therapy results have promising consequences for tumor regression and better cancer control compared to single therapies. Therefore, this study aimed to comprehensively discuss different cancer treatment methods in combination with CAR-T cell therapy and their therapeutic outcomes, which can be a helpful perspective for improving cancer treatment in the near future.

Updates in combined approaches of radiotherapy and immune checkpoint inhibitors for the treatment of breast cancer

Breast cancer is the most prevalent non-skin cancer diagnosed in females and developing novel therapeutic strategies to improve patient outcomes is crucial. The immune system plays an integral role in the body’s response to breast cancer and modulating this immune response through immunotherapy is a promising therapeutic option. Although immune checkpoint inhibitors were recently approved for the treatment of breast cancer patients, not all patients respond to immune checkpoint inhibitors as a monotherapy, highlighting the need to better understand the biology underlying patient response. Additionally, as radiotherapy is a critical component of breast cancer treatment, understanding the interplay of radiation and immune checkpoint inhibitors will be vital as recent studies suggest that combined therapies may induce synergistic effects in preclinical models of breast cancer. This review will discuss the mechanisms supporting combined approaches with radiotherapy and immune checkpoint inhibitors for the treatment of breast cancer. Moreover, this review will analyze the current clinical trials examining combined approaches of radiotherapy, immunotherapy, chemotherapy, and targeted therapy. Finally, this review will evaluate data regarding treatment tolerance and potential biomarkers for these emerging therapies aimed at improving breast cancer outcomes.

Clinical utility of CAR T cell therapy in brain tumors: Lessons learned from the past, current evidence and the future stakes

The unprecedented clinical success of Chimeric Antigen Receptor (CAR) T cell therapy in hematological malignancies has led researchers to study its role in solid tumors. Although, its utility in solid tumors especially in neuroblastoma has begun to emerge, preclinical studies of its efficacy in other solid tumors like osteosarcomas or gliomas has caught the attention of oncologist to be tried in clinical trials. Malignant high-grade brain tumors like glioblastomas or midline gliomas in children represent some of the most difficult malignancies to be managed with conventionally available therapeutics, while relapsed gliomas continue to have the most dismal prognosis due to limited therapeutic options. Innovative therapies such as CAR T cells could give an additional leverage to the treating oncologists by potentially improving outcomes and ameliorating the toxicity of the currently available therapies. Moreover, CAR T cell therapy has the potential to be integrated into the therapeutic paradigm for aggressive gliomas in the near future. In this review we discuss the challenges in using CAR T cell therapy in brain tumors, enumerate the completed and ongoing clinical trials of different types of CAR T cell therapy for different brain tumors with special emphasis on glioblastoma and also discuss the future role of CAR T cells in Brain tumors.

Efficacy and safety of CD19-specific CAR-T cell-based therapy in secondary central nervous system lymphoma

Encouraging response has been achieved in relapsed/refractory (R/R) B-cell lymphoma treated by chimeric antigen receptor T (CAR-T) cells. The efficacy and safety of CAR-T cells in central nervous system lymphoma (CNSL) are still elusive. Here, we retrospectively analyzed 15 patients with R/R secondary CNSL receiving CD19-specific CAR-T cell-based therapy. The patients were infused with CD19, CD19/CD20 or CD19/CD22 CAR-T cells following a conditioning regimen of cyclophosphamide and fludarabine. The overall response rate was 73.3% (11/15), including 9 (60%) with complete remission (CR) and 2 (13.3%) with partial remission (PR). During a median follow-up of 12 months, the median progression-free survival (PFS) was 4 months, and the median overall survival (OS) was 9 months. Of 12 patients with systemic tumor infiltration, 7 (58.3%) achieved CR in CNS, and 5 (41.7%) achieved CR both systemically and in CNS. Median DOR for CNS and systemic disease were 8 and 4 months, respectively. At the end point of observation, of the 7 patients achieved CNS disease CR, one was still alive with sustained CR of CNS disease and systemic disease. The other 6 died of systemic progression. Of the 15 patients, 11 (73.3%) experienced grades 1-2 CRS, and no patient had grades 3-4 CRS. Immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 3 (20%) patients, including 1 (6.6%) with grade 4 ICANS. All the CRS or ICANS were manageable. The CD19-specific CAR-T cell-based therapy appeared to be a promising therapeutic approach in secondary CNSL, based on its antitumor effects and an acceptable side effect profile, meanwhile more strategies are needed to maintain the response.

Rapid generation of genetically engineered T cells for the treatment of virus-related cancers

Adoptive transfer of T cell receptor (TCR) engineered T cells targeting viral epitopes represents a promising approach for treating virus-related cancers. However, efficient identification of epitopes for T cells and corresponding TCR remains challenging. Here, we report a workflow permitting rapid generation of human papillomavirus (HPV)-specific TCR-T cells. Six epitopes of viral proteins belonged to HPV16 or HPV18 were predicted of high affinity to A11:01 according to bioinformatic analysis. Subsequently, cytotoxic T cells (CTLs) induction were performed with these six antigen peptides separately, and antigen-specific T cells were sorted by FACS. TCR clonotypes of these virus-specific T cells were determined by next-generation sequencing. To improve the efficiency of TCRαβ pairs validation, a lentiviral vector library containing 116 TCR constructs was generated, which was consisted of predominant TCRs according to TCR repoertire analysis. Later, TCR library transduced T cells were simulated with peptide pool-pulsed antigen presenting cells, then CD137-positive cells were sorted and subjected to TCR repoertire analysis. The top-hit TCRs and corresponding antigen peptides were deduced and validated. Through this workflow, a TCR targeting the E6_92-101 of HPV16 was identified. This HPV16-specific TCR-T cells showed high activities to HPV16-positive human cervical cancer cells in vitro and efficiently repressed tumor growth in murine model. This study provides a HPV16-specific TCR fitted to HLA-A11:01 population, and exemplifies an efficient approach which can be applied in large-scale screen of virus-specific TCRs, further encouraging researchers to exploit the therapeutic potential of TCR-T cell technique in treating virus-related cancers.

Cellular kinetics: A clinical and computational review of CAR-T cell pharmacology

To the extent that pharmacokinetics influence the effectiveness of nonliving therapeutics, so too do cellular kinetics influence the efficacy of Chimeric Antigen Receptor (CAR) -T cell therapy. Like conventional therapeutics, CAR-T cell therapies undergo a distribution phase upon administration. Unlike other therapeutics, however, this distribution phase is followed by subsequent phases of expansion, contraction, and persistence. The magnitude and duration of these phases unequivocally influence clinical outcomes. Furthermore, the "pharmacodynamics" of CAR-T cells is truly dynamic, as cells can rapidly become exhausted and lose their therapeutic efficacy. Mathematical models are among the translational tools commonly applied to assess, characterize, and predict the complex cellular kinetics and dynamics of CAR-T cells. Here, we provide a focused review of the cellular kinetics of CAR-T cells, the mechanisms underpinning their complexity, and the mathematical modeling approaches used to interrogate them.

Overcome tumor relapse in CAR T cell therapy

Chimeric antigen receptor (CAR) T cell therapy is a novel therapeutic approach that uses gene editing techniques and lentiviral transduction to engineer T cells so that they can effectively kill tumors. However, CAR T cell therapy still has some drawbacks: many patients who received CAR T cell therapy and achieve remission, still had tumor relapse and treatment resistance, which may be due to tumor immune escape and CAR T cell dysfunction. To overcome tumor relapse, more researches are being done to optimize CAR T cell therapy to make it more precise and personalized, including screening for more specific tumor antigens, developing novel CAR T cells, and combinatorial treatment approaches. In this review, we will discuss the mechanisms as well as the progress of research on overcoming plans.

Development and Functional Characterization of a Versatile Radio-/Immunotheranostic Tool for Prostate Cancer Management

Simple Summary

In previous studies, we described a modular Chimeric Antigen Receptor (CAR) T cell platform which we termed UniCAR. In contrast to conventional CARs, the interaction of UniCAR T cells does not occur directly between the CAR T cell and the tumor cell but is mediated via bispecific adaptor molecules so-called target modules (TMs). Here we present the development and functional characterization of a novel IgG4-based TM, directed to the tumor-associated antigen (TAA) prostate stem cell antigen (PSCA), which is overexpressed in prostate cancer (PCa). We show that this anti-PSCA IgG4-TM cannot only be used for (i) redirection of UniCAR T cells to PCa cells but also for (ii) positron emission tomography (PET) imaging, and (iii) alpha particle-based endoradiotherapy. For radiolabeling, the anti-PSCA IgG4-TM was conjugated with the chelator DOTAGA. PET imaging was performed using the ⁶⁴Cu-labeled anti-PSCA IgG4-TM. According to PET imaging, the anti-PSCA IgG4-TM accumulates with high contrast in the PSCA-positive tumors of experimental mice without visible uptake in other organs. For endoradiotherapy the anti-PSCA IgG4-TM-DOTAGA conjugate was labeled with ²²⁵Ac³⁺. Targeted alpha therapy resulted in tumor control over 60 days after a single injection of the ²²⁵Ac-labeled TM. The favorable pharmacological profile of the anti-PSCA IgG4-TM, and its usage for (i) imaging, (ii) targeted alpha therapy, and (iii) UniCAR T cell immunotherapy underlines the promising radio-/immunotheranostic capabilities for the diagnostic imaging and treatment of PCa.

Abstract

Due to its overexpression on the surface of prostate cancer (PCa) cells, the prostate stem cell antigen (PSCA) is a potential target for PCa diagnosis and therapy. Here we describe the development and functional characterization of a novel IgG4-based anti-PSCA antibody (Ab) derivative (anti-PSCA IgG4-TM) that is conjugated with the chelator DOTAGA. The anti-PSCA IgG4-TM represents a multimodal immunotheranostic compound that can be used (i) as a target module (TM) for UniCAR T cell-based immunotherapy, (ii) for diagnostic positron emission tomography (PET) imaging, and (iii) targeted alpha therapy. Cross-linkage of UniCAR T cells and PSCA-positive tumor cells via the anti-PSCA IgG4-TM results in efficient tumor cell lysis both in vitro and in vivo. After radiolabeling with ⁶⁴Cu²⁺, the anti-PSCA IgG4-TM was successfully applied for high contrast PET imaging. In a PCa mouse model, it showed specific accumulation in PSCA-expressing tumors, while no uptake in other organs was observed. Additionally, the DOTAGA-conjugated anti-PSCA IgG4-TM was radiolabeled with ²²⁵Ac³⁺ and applied for targeted alpha therapy. A single injection of the ²²⁵Ac-labeled anti-PSCA IgG4-TM was able to significantly control tumor growth in experimental mice. Overall, the novel anti-PSCA IgG4-TM represents an attractive first member of a novel group of radio-/immunotheranostics that allows diagnostic imaging, endoradiotherapy, and CAR T cell immunotherapy.

Visualizing CAR-T cell Immunotherapy Using 3 Tesla Fluorine-19 MRI

PURPOSE

Chimeric antigen receptor (CAR) T cell cancer immunotherapies have shown remarkable results in patients with hematological malignancies and represent the first approved genetically modified cellular therapies. However, not all blood cancer patients respond favorably, serious side effects have been reported, and the treatment of solid tumors has been a challenge. An imaging tool for visualizing the variety of CAR-T cell products in use and being explored could provide important patient-specific data on CAR-T cell location to inform on potential success or failure of treatment as well as off-target toxicities. Fluorine-19 (19F) magnetic resonance imaging (MRI) allows for the noninvasive detection of 19F perfluorocarbon (PFC) labeled cells. Our objective was to visualize PFC-labeled (PFC +) CAR-T cells in a mouse model of leukemia using clinical field strength (3 Tesla) 19F MRI and compare the cytotoxicity of PFC + versus unlabeled CAR-T cells.

PROCEDURES

NSG mice (n = 17) received subcutaneous injections of CD19 + human B cell leukemia cells (NALM6) expressing firefly luciferase in their left hind flank (1 × 106). Twenty-one days later, each mouse received an intratumoral injection of 10 × 106 PFC + CD19-targeted CAR-T cells (n = 6), unlabeled CD19-targeted CAR-T cells (n = 3), PFC + untransduced T cells (n = 5), or an equivalent volume of saline (n = 3). 19F MRI was performed on mice treated with PFC + CAR-T cells days 1, 3, and 7 post-treatment. Bioluminescence imaging (BLI) was performed on all mice days - 1, 5, 10, and 14 post-treatment to monitor tumor response.

RESULTS

PFC + CAR-T cells were successfully detected in tumors using 19F MRI on days 1, 3, and 7 post-injection. In vivo BLI data revealed that mice treated with PFC + or PFC - CAR-T cells had significantly lower tumor burden by day 14 compared to untreated mice and mice treated with PFC + untransduced T cells (p < 0.05). Importantly, mice treated with PFC + CAR-T cells showed equivalent cytotoxicity compared to mice receiving PFC - CAR-T cells.

CONCLUSIONS

Our studies demonstrate that clinical field strength 19F MRI can be used to visualize PFC + CAR-T cells for up to 7 days post-intratumoral injection. Importantly, PFC labeling did not significantly affect in vivo CAR-T cell cytotoxicity. These imaging tools may have broad applications for tracking emerging CAR-T cell therapies in preclinical models and may eventually be useful for the detection of CAR-T cells in patients where localized injection of CAR-T cells is being pursued.

Application of Noninvasive Imaging to Combined Immune Checkpoint Inhibitors for Breast Cancer: Facts and Future

With the application of mono-immunotherapy in cancer, particularly immune checkpoint inhibitors, improved outcomes have been achieved. However, there are several limitations to immunotherapy, such as a poor response to the drugs, immune resistance, and immune-related adverse events. In recent years, studies of preclinical animal models and clinical trials have demonstrated that immune checkpoint inhibitors for breast cancer can significantly prolong the overall survival and quality of patients' lives. Meanwhile, combined immune checkpoint inhibitor treatment has attracted researchers' attention and showed great potential in the comprehensive treatment of breast cancer patients. Additionally, noninvasive imaging enables physicians to predict response to combined immunotherapeutic drugs, achieve treatment efficacy, and lead to better clinical management. Herein, we review the background of combined immune checkpoint inhibitor therapy and summarize its targeted imaging as well as progress in noninvasive imaging aimed at evaluating therapeutic outcomes. Finally, we describe several factors that may influence the outcome of this combined immunotherapy, the future direction of medical imaging, and the potential application of artificial intelligence in breast cancer. With further development of noninvasive imaging for the guidance of combined immune checkpoint inhibitors, cures for this disease may be achieved.

Validation of CD98hc as a Therapeutic Target for a Combination of Radiation and Immunotherapies in Head and Neck Squamous Cell Carcinoma

Most patients with head and neck squamous cell carcinomas (HNSCC) are diagnosed at a locally advanced stage and show heterogeneous treatment responses. Low SLC3A2 (solute carrier family 3 member 2) mRNA and protein (CD98hc) expression levels are associated with higher locoregional control in HNSCC patients treated with primary radiochemotherapy or postoperative radiochemotherapy, suggesting that CD98hc could be a target for HNSCC radiosensitization. One of the targeted strategies for tumor radiosensitization is precision immunotherapy, e.g., the use of chimeric antigen receptor (CAR) T cells. This study aimed to define the potential clinical value of new treatment approaches combining conventional radiotherapy with CD98hc-targeted immunotherapy. To address this question, we analyzed the antitumor activity of the combination of fractionated irradiation and switchable universal CAR (UniCAR) system against radioresistant HNSCC cells in 3D culture. CD98hc-redirected UniCAR T cells showed the ability to destroy radioresistant HNSCC spheroids. Also, the infiltration rate of the UniCAR T cells was enhanced in the presence of the CD98hc target module. Furthermore, sequential treatment with fractionated irradiation followed by CD98hc-redirected UniCAR T treatment showed a synergistic effect. Taken together, our obtained data underline the improved antitumor effect of the combination of radiotherapy with CD98hc-targeted immunotherapy. Such a combination presents an attractive approach for the treatment of high-risk HNSCC patients.

A Bibliometric and Knowledge-Map Analysis of CAR-T Cells From 2009 to 2021

Objectives

A bibliometric and knowledge-map analysis is used to explore hotspots’ evolution and development trends in the CAR-T cell field. By looking for research hotspots and new topics, we can provide new clues and ideas for researchers in this field.

Methods

The articles and reviews regarding CAR-T cells were retrieved and obtained from the Web of Science Core Collection (WOSCC) on October 28th, 2021. CtieSpace [version 5.8.R3 (64-bit)] and VOSviewer (version 1.6.17) were used to conduct the bibliometric and knowledge-map analysis.

Results

660 authors from 488 institutions in 104 countries/regions published 6,867 papers in 1,212 academic journals. The United States was absolutely in the leading position in this research field. The institution that contributed the most publications was the University of Pennsylvania. Carl H June published the most articles, while Shannon L Maude had the most co-citations. However, there was little cooperation between countries. After 2012, cooperation among various institutions was also small. The journals that published the most CAR-T cell-related papers were Frontiers in immunology and Cancers. Nevertheless, Blood and The New England Journal of Medicine were the most commonly co-cited journals. The most influential research hotspots were the research of CAR-T cells in hematological malignancies, the related research of cytokine release syndrome (CRS), CD19, and the anti-tumor activity and efficacy of CAR-T cells. The latest hotspots and topics included the study of CAR-T cells in solid tumors, universal CAR-T cells, CAR-NK cells, CD22, and anakinra (the IL-1 receptor antagonist). The research of CAR-T cells in solid tumors was a rapidly developing hot field. Emerging topics in this field mainly included the study of CAR-T cells in glioblastoma (related targets: IL13Rα2, EGFRvIII, and HER2), neuroblastoma (related target: GD2), sarcoma (related target: HER2), and pancreatic cancer (related target: mesothelin), especially glioblastoma.

Conclusion

As an anti-tumor therapy with great potential and clinical application prospects, CAR-T cell therapy is still in a stage of rapid development. The related field of CAR-T cells will remain a research hotspot in the future.

Radiation and Chimeric Antigen Receptor T-cell Therapy in B-cell Non-Hodgkin Lymphomas

OPINION STATEMENT

Chimeric antigen receptor T-cell therapy (CAR-T) is a revolutionary advancement in the management of chemotherapy refractory B-cell non-Hodgkin lymphomas representing a potentially curative therapy in scenarios that were previously only palliative. CAR-T cell therapy is associated with unique toxicities as well as practical challenges. One of those challenges is how to manage active lymphoma during the weeks-long CAR-T manufacturing process. Radiation therapy, steroids, and systemic therapy have all been used for what would be considered "bridging therapy" during this time frame. Radiation therapy is a particularly attractive strategy given its proven efficacy in chemotherapy refractory lymphomas; ability to stabilize patients, debulk disease, and palliate symptoms; as well as its potential to enhance the expansion and activity of CAR-T cells. Optimal dose, timing, and method of delivery are yet to be established though there is consensus that it should occur after apheresis if being used as a pre-treatment bridge. Another practical challenge is the management of patients in whom CAR-T cells fail. There is a potential emerging role for salvage radiation therapy, in select patients, for either palliation or as a means to get patients another potentially curative therapy. Collaborative well-designed prospective clinical trials are needed to definitively establish the role for radiation therapy (before or after CAR-T therapy) as well as define the impact on CAR-T cell activity/persistence and associated toxicity.

Synthetic Biology in Chimeric Antigen Receptor T (CAR T) Cell Engineering

Synthetic biology is a novel interdisciplinary research area following engineering principles to redesign and construct biological systems for useful purposes. As one of the most notable clinically relevant application of synthetic biology, chimeric antigen receptor (CAR) T cells have demonstrated tremendous success for the treatment of advanced hematological malignancies in recent years. However, various unsolved obstacles limit the widespread application of CAR T cell therapies, including treatment-associated toxicities, antigen heterogeneity, antigen escape, poor CAR T cell persistence and expansion, and particularly inefficient homing, infiltrating into, and surviving within solid tumors. Accordingly, to improve therapeutic efficacy and minimize side effects, innovative CAR design becomes urgently necessary, and researchers are developing numerous methods to overcome the limitations. Here we summarize currently available bioengineering strategies and discuss the future development from a viewpoint of synthetic biology.

Gut microbiota: impacts on gastrointestinal cancer immunotherapy

The association of gut microbiota with gastrointestinal carcinogenesis has been heavily investigated since the recent advance in sequencing technology. Accumulating evidence has revealed the critical roles of commensal microbes in cancer progression. Given by its importance, emerging studies have focussed on targeting microbiota to ameliorate therapeutic effectiveness. It is now clear that the microbial community is closely related to the efficacy of chemotherapy, while the correlation of microbiota with immunotherapy is much less studied. Herein, we review the up-to-date findings on the influence of gut microbiota on three common immunotherapies including adoptive cell transfer, immune checkpoint blockade, and CpG-oligodeoxynucleotide therapy. We then explore three microbiota-targeted strategies that may improve treatment efficacy, involving dietary intervention, probiotics supplementation, and fecal microbiota transplantation.

Adjuvant Scrotal Radiation Therapy As Bridging Therapy to Chimeric Antigen Receptor T-Cell Following Extramedullary Relapse in B-Cell Acute Lymphoblastic Leukemia

Chimeric antigen T-cell (CAR T) therapy is a promising emerging treatment option for patients with relapsed/refractory acute lymphoma. The role of bridging radiotherapy prior to CAR T infusion is an area of increasing interest with a sizable body of literature regarding its use in non-Hodgkin lymphoma, but reports of its use in leukemia are limited. Furthermore, available literature on bridging radiotherapy is limited to the treatment of bulky, often symptomatic disease, as opposed to its role in treating high-risk regions and sanctuary sites. Here, we present an adult male with multiply relapsed B-cell acute lymphoblastic leukemia (B-ALL) who presented with bone marrow relapse and extramedullary relapse in the right testicle. He was successfully treated with right orchiectomy followed by adjuvant bridging radiotherapy to the left testicle and scrotum, followed by CAR T infusion. Under this treatment paradigm, he tolerated the CAR T infusion with minimal toxicity and was without evidence of disease 100 days post-infusion, with normal testosterone levels. This is the first reported case of bridging radiation being used in the adjuvant setting in a patient with hematologic malignancy. This case adds to the growing body of literature that bridging radiation is well-tolerated and can potentially decrease the risk of relapse in high-risk areas following CAR T infusion.

Engineered CAR-T and novel CAR-based therapies to fight the immune evasion of glioblastoma: gutta cavat lapidem

INTRODUCTION

The field of cancer immunotherapy has achieved great advancements through the application of genetically engineered T cells with chimeric antigen receptors (CAR), that have shown exciting success in eradicating hematologic malignancies and have proved to be safe with promising early signs of antitumoral activity in the treatment of glioblastoma (GBM).

AREAS COVERED

We discuss the use of CAR T cells in GBM, focusing on limitations and obstacles to advancement, mostly related to toxicities, hostile tumor microenvironment, limited CAR T cells infiltration and persistence, target antigen loss/heterogeneity and inadequate trafficking. Furthermore, we introduce the refined strategies aimed at strengthening CAR T activity and offer insights in to novel immunotherapeutic approaches, such as the potential use of CAR NK or CAR M to optimize anti-tumor effects for GBM management.

EXPERT OPINION

With the progressive wide use of CAR T cell therapy, significant challenges in treating solid tumors, including central nervous system (CNS) tumors, are emerging, highlighting early disease relapse and cancer cell resistance issues, owing to hostile immunosuppressive microenvironment and tumor antigen heterogeneity. In addition to CAR T cells, there is great interest in utilizing other types of CAR-based therapies, such as CAR natural killer (CAR NK) or CAR macrophages (CAR M) cells for CNS tumors.

Combining the past and present to advance immuno-radiotherapy of cancer

Since its first clinical application, 120 years ago, radiotherapy evolved into a major anti-cancer treatment modality, offering high cure rates in many human malignancies. During the past ten years, the establishment of immune checkpoint inhibitors (ICIs) in cancer therapeutics has vigorously reintroduced the immune system's role in the outcome of radiotherapy and, conversely, the role of radio-vaccination in the efficacy of immunotherapy. The knowledge and clinical experience that founded the current era of immuno-radiotherapy started alongside with the birth of radiotherapy, and evolved through exhaustive experimental work, clinical trials on active specific immunotherapy, frustrating attempts to validate the importance of cytokine administration with radiotherapy, and, finally, the encouraging ICI-based clinical trials that opened the door to a far more encouraging perspective; radio-vaccination, through its old and new methods, is rising as a research field that promises to cure, previously incurable, disease. In this critical review, we focus on the scientific knowledge gathered through more than a century of research on radiotherapy interactions with the immune system. Understanding the origins of this promising therapeutic approach will substantially contribute to developing new immuno-radiotherapy policies in the fight against cancer.

'Le Roi est mort, vive le Roi': New Roles of Radiotherapy in the Treatment of Lymphomas in Combination With Immunotherapy

BACKGROUND

immunotherapy (IT), including checkpoint inhibitors (CIs) and Chimeric Antigen Receptor T cell therapy (CAR-T) revolutionized the treatment of relapsing or refractory (r/r) lymphoma. Several preliminary experiences evaluated concomitant administration of radiotherapy and IT.

METHODS

we performed a systematic review of current literature as of March 30, 2020. A total of 1090 records was retrieved, 42 articles were selected on the basis of title and abstract and, after the removal of analyses with no original data or insufficient clinical information, 28 papers were included in the review.

RESULTS

previous studies were mostly represented by case reports/series or small cohorts. Nonetheless, combination of radiotherapy and CIs or CAR-T led to promising outcomes, resulting in extremely high rates of complete response and improving progression free and overall survival compared with data from recent clinical trials. Combination of RT and CIs had a fair toxicity profile with no reports of severe side effects. Within the limits of the small cohorts retrieved, RT seems a superior option compared with systemic treatment as a 'bridge' to CAR-T and could as well reduce severe complications rates. Radiotherapy could elicit immune response against lymphoma, as demonstrated by multiple cases of abscopal effect and its inclusion in anti-neoplastic vaccines protocols.

CONCLUSION

The results of this review warrant the evaluation of combination of RT and immunotherapy in larger and preferably prospective and randomized cohorts to confirm these preliminary impressive outcomes. The optimal dose, fractionation and timing of RT still have to be clarified.

Hydrogel-Induced Cell Membrane Disruptions Enable Direct Cytosolic Delivery of Membrane-Impermeable Cargo

Intracellular delivery of membrane-impermeable cargo offers unique opportunities for biological research and the development of cell-based therapies. Despite the breadth of available intracellular delivery tools, existing protocols are often suboptimal and alternative approaches that merge delivery efficiency with both biocompatibility, as well as applicability, remain highly sought after. Here, a comprehensive platform is presented that exploits the unique property of cationic hydrogel nanoparticles to transiently disrupt the plasma membrane of cells, allowing direct cytosolic delivery of uncomplexed membrane-impermeable cargo. Using this platform, which is termed Hydrogel-enabled nanoPoration or HyPore, the delivery of fluorescein isothiocyanate (FITC)-dextran macromolecules in various cancer cell lines and primary bovine corneal epithelial cells is convincingly demonstrated. Of note, HyPore demonstrates efficient FITC-dextran delivery in primary human T cells, outperforming state-of-the-art electroporation-mediated delivery. Moreover, the HyPore platform enables cytosolic delivery of functional proteins, including a histone-binding nanobody as well as the enzymes granzyme A and Cre-recombinase. Finally, HyPore-mediated delivery of the MRI contrast agent gadobutrol in primary human T cells significantly improves their T₁ -weighted MRI signal intensities compared to electroporation. Taken together, HyPore is proposed as a straightforward, highly versatile, and cost-effective technique for high-throughput, ex vivo manipulation of primary cells and cell lines.

Metabolic radiolabeling and in vivo PET imaging of cytotoxic T lymphocytes to guide combination adoptive cell transfer cancer therapy

BACKGROUND

Adoptive T cell transfer-based immunotherapy yields unsatisfactory results in the treatment of solid tumors, partially owing to limited tumor infiltration and the immunosuppressive microenvironment in solid tumors. Therefore, strategies for the noninvasive tracking of adoptive T cells are critical for monitoring tumor infiltration and for guiding the development of novel combination therapies.

METHODS

We developed a radiolabeling method for cytotoxic T lymphocytes (CTLs) that comprises metabolically labeling the cell surface glycans with azidosugars and then covalently conjugating them with ⁶⁴Cu-1,4,7-triazacyclononanetriacetic acid-dibenzo-cyclooctyne (⁶⁴Cu-NOTA-DBCO) using bioorthogonal chemistry. ⁶⁴Cu-labeled control-CTLs and ovalbumin-specific CTLs (OVA-CTLs) were tracked using positron emission tomography (PET) in B16-OVA tumor-bearing mice. We also investigated the effects of focal adhesion kinase (FAK) inhibition on the antitumor efficacy of OVA-CTLs using a poly(lactic-co-glycolic) acid (PLGA)-encapsulated nanodrug (PLGA-FAKi).

RESULTS

CTLs can be stably radiolabeled with ⁶⁴Cu with a minimal effect on cell viability. PET imaging of ⁶⁴Cu-OVA-CTLs enables noninvasive mapping of their in vivo behavior. Moreover, ⁶⁴Cu-OVA-CTLs PET imaging revealed that PLGA-FAKi induced a significant increase in OVA-CTL infiltration into tumors, suggesting the potential for a combined therapy comprising OVA-CTLs and PLGA-FAKi. Further combination therapy studies confirmed that the PLGA-FAKi nanodrug markedly improved the antitumor effects of adoptive OVA-CTLs transfer by multiple mechanisms.

CONCLUSION

These findings demonstrated that metabolic radiolabeling followed by PET imaging can be used to sensitively profile the early-stage migration and tumor-targeting efficiency of adoptive T cells in vivo. This strategy presents opportunities for predicting the efficacy of cell-based adoptive therapies and for guiding combination regimens.

CAR T Cell-Based Immunotherapy for the Treatment of Glioblastoma

Glioblastoma multiforme (GBM) is the most common and aggressive malignant primary brain tumor in adults. Current treatment options typically consist of surgery followed by chemotherapy or more frequently radiotherapy, however, median patient survival remains at just over 1 year. Therefore, the need for novel curative therapies for GBM is vital. Characterization of GBM cells has contributed to identify several molecules as targets for immunotherapy-based treatments such as EGFR/EGFRvIII, IL13Rα2, B7-H3, and CSPG4. Cytotoxic T lymphocytes collected from a patient can be genetically modified to express a chimeric antigen receptor (CAR) specific for an identified tumor antigen (TA). These CAR T cells can then be re-administered to the patient to identify and eliminate cancer cells. The impressive clinical responses to TA-specific CAR T cell-based therapies in patients with hematological malignancies have generated a lot of interest in the application of this strategy with solid tumors including GBM. Several clinical trials are evaluating TA-specific CAR T cells to treat GBM. Unfortunately, the efficacy of CAR T cells against solid tumors has been limited due to several factors. These include the immunosuppressive tumor microenvironment, inadequate trafficking and infiltration of CAR T cells and their lack of persistence and activity. In particular, GBM has specific limitations to overcome including acquired resistance to therapy, limited diffusion across the blood brain barrier and risks of central nervous system toxicity. Here we review current CAR T cell-based approaches for the treatment of GBM and summarize the mechanisms being explored in pre-clinical, as well as clinical studies to improve their anti-tumor activity.

Obstacles and Coping Strategies of CAR-T Cell Immunotherapy in Solid Tumors

Chimeric antigen receptor (CAR) T-cell immunotherapy refers to an adoptive immunotherapy that has rapidly developed in recent years. It is a novel type of treatment that enables T cells to express specific CARs on their surface, then returns these T cells to tumor patients to kill the corresponding tumor cells. Significant strides in CAR-T cell immunotherapy against hematologic malignancies have elicited research interest among scholars in the treatment of solid tumors. Nonetheless, in contrast with the efficacy of CAR-T cell immunotherapy in the treatment of hematologic malignancies, its general efficacy against solid tumors is insignificant. This has been attributed to the complex biological characteristics of solid tumors. CAR-T cells play a better role in solid tumors, for instance by addressing obstacles including the lack of specific targets, inhibition of tumor microenvironment (TME), homing barriers of CAR-T cells, differentiation and depletion of CAR-T cells, inhibition of immune checkpoints, trogocytosis of CAR-T cells, tumor antigen heterogeneity, etc. This paper reviews the obstacles influencing the efficacy of CAR-T cell immunotherapy in solid tumors, their mechanism, and coping strategies, as well as economic restriction of CAR-T cell immunotherapy and its solutions. It aims to provide some references for researchers to better overcome the obstacles that affect the efficacy of CAR-T cells in solid tumors.

Radionuclide-based molecular imaging allows CAR-T cellular visualization and therapeutic monitoring

Chimeric antigen receptor T cell (CAR-T) therapy is a new and effective form of adoptive cell therapy that is rapidly entering the mainstream for the treatment of CD19-positive hematological cancers because of its impressive effect and durable responses. Huge challenges remain in achieving similar success in patients with solid tumors. The current methods of monitoring CAR-T, including morphological imaging (CT and MRI), blood tests, and biopsy, have limitations to assess whether CAR-T cells are homing to tumor sites and infiltrating into tumor bed, or to assess the survival, proliferation, and persistence of CAR-T cells in solid tumors associated with an immunosuppressive microenvironment. Radionuclide-based molecular imaging affords improved CAR-T cellular visualization and therapeutic monitoring through either a direct cellular radiolabeling approach or a reporter gene imaging strategy, and endogenous cell imaging is beneficial to reflect functional information and immune status of T cells. Focusing on the dynamic monitoring and precise assessment of CAR-T therapy, this review summarizes the current applications of radionuclide-based noninvasive imaging in CAR-T cells visualization and monitoring and presents current challenges and strategic choices.

Cytosolic delivery of gadolinium via photoporation enables improved in vivo magnetic resonance imaging of cancer cells

Longitudinal in vivo monitoring of transplanted cells is crucial to perform cancer research or to assess the treatment outcome of cell-based therapies. While several bio-imaging techniques can be used, magnetic resonance imaging (MRI) clearly stands out in terms of high spatial resolution and excellent soft-tissue contrast. However, MRI suffers from low sensitivity, requiring cells to be labeled with high concentrations of contrast agents. An interesting option is to label cells with clinically approved gadolinium chelates which generate a hyperintense MR signal. However, spontaneous uptake of the label via pinocytosis results in its endosomal sequestration, leading to quenching of the T₁-weighted relaxation. To avoid this quenching effect, delivery of gadolinium chelates directly into the cytosol via electroporation or hypotonic cell swelling have been proposed. However, these methods are also accompanied by several drawbacks such as a high cytotoxicity, and changes in gene expression and phenotype. Here, we demonstrate that nanoparticle-sensitized laser induced photoporation forms an attractive alternative to efficiently deliver the contrast agent gadobutrol into the cytosol of both HeLa and SK-OV-3 IP1 cells. After intracellular delivery by photoporation the quenching effect is clearly avoided, leading to a strong increase in the hyperintense T₁-weighted MR signal. Moreover, when compared to nucleofection as a state-of-the-art electroporation platform, photoporation has much less impact on cell viability, which is extremely important for reliable cell tracking studies. Additional experiments confirm that photoporation does not induce any change in the long-term viability or the migratory capacity of the cells. Finally, we show that gadolinium 'labeled' SK-OV-3 IP1 cells can be imaged in vivo by MRI with high soft-tissue contrast and spatial resolution, revealing indications of potential tumor invasion or angiogenesis.

Physiological Imaging Methods for Evaluating Response to Immunotherapies in Glioblastomas

Glioblastoma (GBM) is the most malignant brain tumor in adults, with a dismal prognosis despite aggressive multi-modal therapy. Immunotherapy is currently being evaluated as an alternate treatment modality for recurrent GBMs in clinical trials. These immunotherapeutic approaches harness the patient's immune response to fight and eliminate tumor cells. Standard MR imaging is not adequate for response assessment to immunotherapy in GBM patients even after using refined response assessment criteria secondary to amplified immune response. Thus, there is an urgent need for the development of effective and alternative neuroimaging techniques for accurate response assessment. To this end, some groups have reported the potential of diffusion and perfusion MR imaging and amino acid-based positron emission tomography techniques in evaluating treatment response to different immunotherapeutic regimens in GBMs. The main goal of these techniques is to provide definitive metrics of treatment response at earlier time points for making informed decisions on future therapeutic interventions. This review provides an overview of available immunotherapeutic approaches used to treat GBMs. It discusses the limitations of conventional imaging and potential utilities of physiologic imaging techniques in the response assessment to immunotherapies. It also describes challenges associated with these imaging methods and potential solutions to avoid them.