Photoswitchable CAR-T Cell Function In Vitro and In Vivo via a Cleavable Mediator

Challenges and strategies in relation to effective CAR-T cell immunotherapy for solid tumors

Chimeric Antigen Receptor T cell (CAR-T) therapy has revolutionized cancer treatment, but its application to solid tumors is limited. CAR-T cells have poor incapability of entering, surviving, proliferating, and finally exerting function in the tumor microenvironment. This review summarizes the main strategies related to enhancing the infiltration, efficacy, antigen recognition, and production of CAR-T in solid tumors. Additional applications of CAR-γδ T and macrophages are also discussed. We believe CAR-T will be a milestone in treating solid tumors once these problems are solved.

Enhancing the safety of CAR-T cell therapy: Synthetic genetic switch for spatiotemporal control

Chimeric antigen receptor T (CAR-T) cell therapy is a promising and precise targeted therapy for cancer that has demonstrated notable potential in clinical applications. However, severe adverse effects limit the clinical application of this therapy and are mainly caused by uncontrollable activation of CAR-T cells, including excessive immune response activation due to unregulated CAR-T cell action time, as well as toxicity resulting from improper spatial localization. Therefore, to enhance controllability and safety, a control module for CAR-T cells is proposed. Synthetic biology based on genetic engineering techniques is being used to construct artificial cells or organisms for specific purposes. This approach has been explored in recent years as a means of achieving controllability in CAR-T cell therapy. In this review, we summarize the recent advances in synthetic biology methods used to address the major adverse effects of CAR-T cell therapy in both the temporal and spatial dimensions.

Improving Photocleavage Efficiency of Photocleavable Protein for Antimicrobial Peptide Histatin 1 Expression

BACKGROUND

Antimicrobial peptides (AMPs) are promising alternative agents for antibiotics to overcome antibiotic resistance problems. But, it is difficult to produce large-scale antimicrobial research due to the toxicity towards expression hosts or degradation by peptidases in the host. Therefore, heterologous recombinant expression of antimicrobial peptides has always been a challenging issue.

OBJECTIVES

To overcome toxicity to the expression host and low expression level, a new photocleavable protein fusion expression method for antimicrobial peptides is provided.3 Methods: Through directed evolution and high throughput screening, a photocleavable protein mutant R6-2-6-4 with a higher photocleavage efficiency was obtained. The DNA coding sequence of antimicrobial peptide Histatin 1 was fused within the sequence of R6-2-6-4 gene. The fusion gene was successfully expressed in Escherichia coli expression system.

RESULTS

Antimicrobial peptide Histatin 1 could be successfully expressed and purified by fusing within PhoCl mutant R6-2-6-4. The antimicrobial activity was rarely affected, and the MIC value was 33 ug/mL, which was basically equivalent to 32 ug/mL of the chemically synthesized Histatin 1. After amplification in a 5 L fermenter, the expression of PhoCl mutant (R6-2-6-4)-Histatin1 improved up to 87.6 mg/L in fermenter, and Histatin1 obtained by photocleavage also could up to 11 mg/L. The prepared Histatin1 powder remained stable when stored at 4oC for up to 4 months without any degradation. In addition, the expression and photocleavage of β -Defensin105 and Lysostaphin verified the certain universality of the PhoCl mutant fusion expression system.

CONCLUSION

Antimicrobial peptides Histatin 1, β -Defensin 105 and Lysostaphin were successfully expressed and purified by photocleavable protein mutant. This may provide a novel strategy to express and purify antimicrobial peptides in the Escherichia coli expression system.

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.

Post-translational covalent assembly of CAR and synNotch receptors for programmable antigen targeting

Chimeric antigen receptors (CARs) and synthetic Notch (synNotch) receptors are engineered cell-surface receptors that sense a target antigen and respond by activating T cell receptor signaling or a customized gene program, respectively. Here, to expand the targeting capabilities of these receptors, we develop "universal" receptor systems for which receptor specificity can be directed post-translationally via covalent attachment of a co-administered antibody bearing a benzylguanine (BG) motif. A SNAPtag self-labeling enzyme is genetically fused to the receptor and reacts with BG-conjugated antibodies for covalent assembly, programming antigen recognition. We demonstrate that activation of SNAP-CAR and SNAP-synNotch receptors can be successfully targeted by clinically relevant BG-conjugated antibodies, including anti-tumor activity of SNAP-CAR T cells in vivo in a human tumor xenograft mouse model. Finally, we develop a mathematical model to better define the parameters affecting universal receptor signaling. SNAP receptors provide a powerful strategy to post-translationally reprogram the targeting specificity of engineered cells.

Nanomodified Switch Induced Precise and Moderate Activation of CAR-T Cells for Solid Tumors

Chimeric antigen receptor (CAR)-T cell therapy is a transformative treatment against advanced malignancies. Unfortunately, once administrated in vivo, CAR-T cells become out of artificial control, and fierce response to CAR-T therapy may cause severe adverse events, represented by cytokine-release syndrome and on-target/off-tumor effects. Here, a nanomodified switch strategy is developed, leading to sustained and precise "on-tumor only" activation of CAR-T cells. Here, original gelatinase-responsive nanoparticles (NPs) are used to selectively deliver the heterodimerizing switch, which is the key component of switchable CAR with separated activation modules. The "NanoSwitch" is tumor-specific, thus inactivated switchable CAR-T cells do little harm to normal cells, even if the normal cells express the target of CAR-T. Owing to the sustained-release effect of NPs, the CAR-T cells are activated smoothly, avoiding sudden release of cytokine. These data introduce NanoSwitch as a universal and applicable solution to safety problems of CAR-T therapy regardless of the target.

Tuning CARs: recent advances in modulating chimeric antigen receptor (CAR) T cell activity for improved safety, efficacy, and flexibility

Cancer immunotherapies utilizing genetically engineered T cells have emerged as powerful personalized therapeutic agents showing dramatic preclinical and clinical results, particularly in hematological malignancies. Ectopically expressed chimeric antigen receptors (CARs) reprogram immune cells to target and eliminate cancer. However, CAR T cell therapy's success depends on the balance between effective anti-tumor activity and minimizing harmful side effects. To improve CAR T cell therapy outcomes and mitigate associated toxicities, scientists from different fields are cooperating in developing next-generation products using the latest molecular cell biology and synthetic biology tools and technologies. The immunotherapy field is rapidly evolving, with new approaches and strategies being reported at a fast pace. This comprehensive literature review aims to provide an up-to-date overview of the latest developments in controlling CAR T cell activity for improved safety, efficacy, and flexibility.

Application and Design of Switches Used in CAR

Among the many oncology therapies, few have generated as much excitement as CAR-T. The success of CAR therapy would not have been possible without the many discoveries that preceded it, most notably, the Nobel Prize-winning breakthroughs in cellular immunity. However, despite the fact that CAR-T already offers not only hope for development, but measurable results in the treatment of hematological malignancies, CAR-T still cannot be safely applied to solid tumors. The reason for this is, among other things, the lack of tumor-specific antigens which, in therapy, threatens to cause a lethal attack of lymphocytes on healthy cells. In the case of hematological malignancies, dangerous complications such as cytokine release syndrome may occur. Scientists have responded to these clinical challenges with molecular switches. They make it possible to remotely control CAR lymphocytes after they have already been administered to the patient. Moreover, they offer many additional capabilities. For example, they can be used to switch CAR antigenic specificity, create logic gates, or produce local activation under heat or light. They can also be coupled with costimulatory domains, used for the regulation of interleukin secretion, or to prevent CAR exhaustion. More complex modifications will probably require a combination of reprogramming (iPSc) technology with genome editing (CRISPR) and allogenic (off the shelf) CAR-T production.

A novel photocaged B-RafV600E inhibitor toward precise melanoma treatment

Photoinduced drug release can reduce systemic side effects by releasing active drugs with high spatiotemporal accuracy, representing a promising strategy for precise cancer therapy. Here we designed and synthesized a novel photocaged B-Raf^V600E inhibitor 2, which, upon UV irradiation, could release a potent B-Raf^V600E inhibitor 1. Accordingly, once activated by the UV light, compound 2 could potently inhibit the proliferation of melanoma cells bearing B-Raf^V600E mutant while sparing melanoma cells expressing wild-type B-Raf, and could dose-dependently suppress the activation of the MAPK signaling pathway. Notably, the UV-mediated active component release and the resulting antiproliferative effects of compound 2 could be recapitulated when exposed to the sunlight, greatly enhancing its practicality. This photocaged B-Raf^V600E inhibitor 2 might serve as a novel therapeutic agent toward precise melanoma treatment.

Porous Silicon Nanocarriers with Stimulus-Cleavable Linkers for Effective Cancer Therapy

Porous silicon nanoparticles (pSiNPs) are widely utilized as drug carriers due to their excellent biocompatibility, large surface area, and versatile surface chemistry. However, the dispersion in pore size and biodegradability of pSiNPs arguably have hindered the application of pSiNPs for controlled drug release. Here, a step-changing solution to this problem is described involving the design, synthesis, and application of three different linker-drug conjugates comprising anticancer drug doxorubicin (DOX) and different stimulus-cleavable linkers (SCLs) including the photocleavable linker (ortho-nitrobenzyl), pH-cleavable linker (hydrazone), and enzyme-cleavable linker (β-glucuronide). These SCL-DOX conjugates are covalently attached to the surface of pSiNP via copper (I)-catalyzed alkyne-azide cycloaddition (CuAAC, i.e., click reaction) to afford pSiNP-SCL-DOXs. The mass loading of the covalent conjugation approach for pSiNP-SCL-DOX reaches over 250 µg of DOX per mg of pSiNPs, which is notably twice the mass loading achieved by noncovalent loading. Moreover, the covalent conjugation between SCL-DOX and pSiNPs endows the pSiNPs with excellent stability and highly controlled release behavior. When tested in both in vitro and in vivo tumor models, the pSiNP-SCL-DOXs induces excellent tumor growth inhibition.

Engineering CAR T cells for enhanced efficacy and safety

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

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.

Advances in Universal CAR-T Cell Therapy

Chimeric antigen receptor T (CAR-T) cell therapy achieved extraordinary achievements results in antitumor treatments, especially against hematological malignancies, where it leads to remarkable, long-term antineoplastic effects with higher target specificity. Nevertheless, some limitations persist in autologous CAR-T cell therapy, such as high costs, long manufacturing periods, and restricted cell sources. The development of a universal CAR-T (UCAR-T) cell therapy is an attractive breakthrough point that may overcome most of these drawbacks. Here, we review the progress and challenges in CAR-T cell therapy, especially focusing on comprehensive comparison in UCAR-T cell therapy to original CAR-T cell therapy. Furthermore, we summarize the developments and concerns about the safety and efficiency of UCAR-T cell therapy. Finally, we address other immune cells, which might be promising candidates as a complement for UCAR-T cells. Through a detailed overview, we describe the current landscape and explore the prospect of UCAR-T cell therapy.

Engineering genetic devices for in vivo control of therapeutic T cell activity triggered by the dietary molecule resveratrol

Chimeric antigen receptor (CAR)-engineered T cell therapies have been recognized as powerful strategies in cancer immunotherapy; however, the clinical application of CAR-T is currently constrained by severe adverse effects in patients, caused by excessive cytotoxic activity and poor T cell control. Herein, we harnessed a dietary molecule resveratrol (RES)-responsive transactivator and a transrepressor to develop a repressible transgene expression (RESrep) device and an inducible transgene expression (RESind) device, respectively. After optimization, these tools enabled the control of CAR expression and CAR-mediated antitumor function in engineered human cells. We demonstrated that a resveratrol-repressible CAR expression (RESrep-CAR) device can effectively inhibit T cell activation upon resveratrol administration in primary T cells and a xenograft tumor mouse model. Additionally, we exhibit how a resveratrol-inducible CAR expression (RESind-CAR) device can achieve fine-tuned and reversible control over T cell activation via a resveratrol-titratable mechanism. Furthermore, our results revealed that the presence of RES can activate RESind-CAR T cells with strong anticancer cytotoxicity against cells in vitro and in vivo. Our study demonstrates the utility of RESrep and RESind devices as effective tools for transgene expression and illustrates the potential of RESrep-CAR and RESind-CAR devices to enhance patient safety in precision cancer immunotherapies.

Quantifying persistence in the T-cell signaling network using an optically controllable antigen receptor

T cells discriminate between healthy and infected cells with remarkable sensitivity when mounting an immune response, which is hypothesized to depend on T cells combining stimuli from multiple antigen-presenting cell interactions into a more potent response. To quantify the capacity for T cells to accomplish this, we have developed an antigen receptor that is optically tunable within cell conjugates, providing control over the duration, and intensity of intracellular T-cell signaling. We observe limited persistence within the T-cell intracellular network on disruption of receptor input, with signals dissipating entirely in ~15 min, and directly show sustained proximal receptor signaling is required to maintain gene transcription. T cells thus primarily accumulate the outputs of gene expression rather than integrate discrete intracellular signals. Engineering optical control in a clinically relevant chimeric antigen receptor (CAR), we show that this limited signal persistence can be exploited to increase CAR-T cell activation threefold using pulsatile stimulation. Our results are likely to apply more generally to the signaling dynamics of other cellular networks.

Design, Synthesis, and Biological Evaluation of a Novel Photocaged PI3K Inhibitor toward Precise Cancer Treatment

Aberrant activation of the PI3K pathway has been intensively targeted for cancer therapeutics for decades, leading to more than 40 PI3K inhibitors advanced into clinical trials. However, it is increasingly noticed that PI3K inhibitors often showed limited efficacy as well as a number of serious on-target adverse effects during the clinical development. In this work, we designed and synthesized a novel photocaged PI3K inhibitor 1, which could be readily activated by UV irradiation to release a highly potent PI3K inhibitor 2. Upon UV irradiation, the photocaged inhibitor 1 demonstrated remarkably enhanced antiproliferative activity against multiple cancer cell lines and significant efficacy in the patient-derived tumor organoid model. Furthermore, 1 also showed favorable anticancer activity in an in vivo zebrafish xenograft model. Taken together, the photocaged PI3K inhibitor 1 represents a promising avenue for novel therapeutics toward precise cancer treatment.