Nonimmune cells equipped with T-cell-receptor-like signaling for cancer cell ablation

Small-Molecule Regulators for Gene Switches to Program Mammalian Cell Behaviour

Synthetic or natural small molecules have been extensively employed as trigger signals or inducers to regulate engineered gene circuits introduced into living cells in order to obtain desired outputs in a controlled and predictable manner. Here, we provide an overview of small molecules used to drive synthetic-biology-based gene circuits in mammalian cells, together with examples of applications at different levels of control, including regulation of DNA manipulation, RNA synthesis and editing, and protein synthesis, maturation, and trafficking. We also discuss the therapeutic potential of these small-molecule-responsive gene circuits, focusing on the advantages and disadvantages of using small molecules as triggers, the mechanisms involved, and the requirements for selecting suitable molecules, including efficiency, specificity, orthogonality, and safety. Finally, we explore potential future directions for translation of these devices to clinical medicine.

Applications of synthetic biology in medical and pharmaceutical fields

Synthetic biology aims to design or assemble existing bioparts or bio-components for useful bioproperties. During the past decades, progresses have been made to build delicate biocircuits, standardized biological building blocks and to develop various genomic/metabolic engineering tools and approaches. Medical and pharmaceutical demands have also pushed the development of synthetic biology, including integration of heterologous pathways into designer cells to efficiently produce medical agents, enhanced yields of natural products in cell growth media to equal or higher than that of the extracts from plants or fungi, constructions of novel genetic circuits for tumor targeting, controllable releases of therapeutic agents in response to specific biomarkers to fight diseases such as diabetes and cancers. Besides, new strategies are developed to treat complex immune diseases, infectious diseases and metabolic disorders that are hard to cure via traditional approaches. In general, synthetic biology brings new capabilities to medical and pharmaceutical researches. This review summarizes the timeline of synthetic biology developments, the past and present of synthetic biology for microbial productions of pharmaceutics, engineered cells equipped with synthetic DNA circuits for diagnosis and therapies, live and auto-assemblied biomaterials for medical treatments, cell-free synthetic biology in medical and pharmaceutical fields, and DNA engineering approaches with potentials for biomedical applications.

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.

Droplet Microfluidics Enables Tracing of Target Cells at the Single-Cell Transcriptome Resolution

The rapid promotion of single-cell omics in various fields has begun to help solve many problems encountered in research, including precision medicine, prenatal diagnosis, and embryo development. Meanwhile, single-cell techniques are also constantly updated with increasing demand. For some specific target cells, the workflow from droplet screening to single-cell sequencing is a preferred option and should reduce the impact of operation steps, such as demulsification and cell recovery. We developed an all-in-droplet method integrating cell encapsulation, target sorting, droplet picoinjection, and single-cell transcriptome profiling on chips to achieve labor-saving monitoring of TCR-T cells. As a proof of concept, in this research, TCR-T cells were encapsulated, sorted, and performed single-cell transcriptome sequencing (scRNA-seq) by injecting reagents into droplets. It avoided the tedious operation of droplet breakage and re-encapsulation between droplet sorting and scRNA-seq. Moreover, convenient device operation will accelerate the progress of chip marketization. The strategy achieved an excellent recovery performance of single-cell transcriptome with a median gene number over 4000 and a cross-contamination rate of 8.2 ± 2%. Furthermore, this strategy allows us to develop a device with high integrability to monitor infused TCR-T cells, which will promote the development of adoptive T cell immunotherapy and their clinical application.

Therapeutic cell engineering: designing programmable synthetic genetic circuits in mammalian cells

Cell therapy approaches that employ engineered mammalian cells for on-demand production of therapeutic agents in the patient's body are moving beyond proof-of-concept in translational medicine. The therapeutic cells can be customized to sense user-defined signals, process them, and respond in a programmable and predictable way. In this paper, we introduce the available tools and strategies employed to design therapeutic cells. Then, various approaches to control cell behaviors, including open-loop and closed-loop systems, are discussed. We also highlight therapeutic applications of engineered cells for early diagnosis and treatment of various diseases in the clinic and in experimental disease models. Finally, we consider emerging technologies such as digital devices and their potential for incorporation into future cell-based therapies.

Autonomous push button-controlled rapid insulin release from a piezoelectrically activated subcutaneous cell implant

Traceless physical cues are desirable for remote control of the in situ production and real-time dosing of biopharmaceuticals in cell-based therapies. However, current optogenetic, magnetogenetic, or electrogenetic devices require sophisticated electronics, complex artificial intelligence-assisted software, and external energy supplies for power and control. Here, we describe a self-sufficient subcutaneous push button-controlled cellular implant powered simply by repeated gentle finger pressure exerted on the overlying skin. Pushing the button causes transient percutaneous deformation of the implant's embedded piezoelectric membrane, which produces sufficient low-voltage energy inside a semi-permeable platinum-coated cell chamber to mediate rapid release of a biopharmaceutical from engineered electro-sensitive human cells. Release is fine-tuned by varying the frequency and duration of finger-pressing stimulation. As proof of concept, we show that finger-pressure activation of the subcutaneous implant can restore normoglycemia in a mouse model of type 1 diabetes. Self-sufficient push-button devices may provide a new level of convenience for patients to control their cell-based therapies.

The evolution of synthetic receptor systems

Receptors enable cells to detect, process and respond to information about their environments. Over the past two decades, synthetic biologists have repurposed physical parts and concepts from natural receptors to engineer synthetic receptors. These technologies implement customized sense-and-respond programs that link a cell's interaction with extracellular and intracellular cues to user-defined responses. When combined with tools for information processing, these advances enable programming of sophisticated customized functions. In recent years, the library of synthetic receptors and their capabilities has substantially evolved-a term we employ here to mean systematic improvement and expansion. Here, we survey the existing mammalian synthetic biology toolkit of protein-based receptors and signal-processing components, highlighting efforts to evolve and integrate some of the foundational synthetic receptor systems. We then propose a generalized strategy for engineering and improving receptor systems to meet defined functional objectives called a 'metric-enabled approach for synthetic receptor engineering' (MEASRE).

CelloSelect - A synthetic cellobiose metabolic pathway for selection of stable transgenic CHO cell lines

Current protocols for generating stable transgenic cell lines mostly rely on antibiotic selection or the use of specialized cell lines lacking an essential part of their metabolic machinery, but these approaches require working with either toxic chemicals or knockout cell lines, which can reduce productivity. Since most mammalian cells cannot utilize cellobiose, a disaccharide consisting of two β-1,4-linked glucose molecules, we designed an antibiotic-free selection system, CelloSelect, which consists of a selection cassette encoding Neurospora crassa cellodextrin transporter CDT1 and β-glucosidase GH1-1. When cultivated in glucose-free culture medium containing cellobiose, CelloSelect-transfected cells proliferate by metabolizing cellobiose as a primary energy source, and are protected from glucose starvation. We show that the combination of CelloSelect with a PiggyBac transposase-based integration strategy provides a platform for the swift and efficient generation of stable transgenic cell lines. Growth rate analysis of metabolically engineered cells in cellobiose medium confirmed the expansion of cells stably expressing high levels of a cargo fluorescent marker protein. We further validated this strategy by applying the CelloSelect system for stable integration of sequences encoding two biopharmaceutical proteins, erythropoietin and the monoclonal antibody rituximab, and confirmed that the proteins are efficiently produced in either cellobiose- or glucose-containing medium in suspension-adapted CHO cells cultured in chemically defined media. We believe coupling heterologous metabolic pathways additively to the endogenous metabolism of mammalian cells has the potential to complement or to replace current cell-line selection systems.

Emerging mammalian gene switches for controlling implantable cell therapies

Engineered cell-based therapies have emerged as a new paradigm in modern medicine, with several engineered T cell therapies currently approved to treat blood cancers and many more in clinical development. Tremendous progress in synthetic biology over the past two decades has allowed us to program cells with sophisticated sense-and-response modules that can effectively control therapeutic functions. In this review, we highlight recent advances in mammalian synthetic gene switches, focusing on devices designed for therapeutic applications. Although many gene switches responding to endogenous or exogenous molecular signals have been developed, the focus is shifting towards achieving remote-controlled production of therapeutic effectors by stimulating implanted engineered cells with traceless physical signals, such as light, electrical signals, magnetic fields, heat or ultrasound.

Engineering precision therapies: lessons and motivations from the clinic

In the past decade, gene- and cell-based therapies have been at the forefront of the biomedical revolution. Synthetic biology, the engineering discipline of building sophisticated ‘genetic software’ to enable precise regulation of gene activities in living cells, has been a decisive success factor of these new therapies. Here, we discuss the core technologies and treatment strategies that have already gained approval for therapeutic applications in humans. We also review promising preclinical work that could either enhance the efficacy of existing treatment strategies or pave the way for new precision medicines to treat currently intractable human conditions.

Elucidation and refinement of synthetic receptor mechanisms

Synthetic receptors are powerful tools for engineering mammalian cell-based devices. These biosensors enable cell-based therapies to perform complex tasks such as regulating therapeutic gene expression in response to sensing physiological cues. Although multiple synthetic receptor systems now exist, many aspects of receptor performance are poorly understood. In general, it would be useful to understand how receptor design choices influence performance characteristics. In this study, we examined the modular extracellular sensor architecture (MESA) and systematically evaluated previously unexamined design choices, yielding substantially improved receptors. A key finding that might extend to other receptor systems is that the choice of transmembrane domain (TMD) is important for generating high-performing receptors. To provide mechanistic insights, we adopted and employed a Förster resonance energy transfer-based assay to elucidate how TMDs affect receptor complex formation and connected these observations to functional performance. To build further insight into these phenomena, we developed a library of new MESA receptors that sense an expanded set of ligands. Based upon these explorations, we conclude that TMDs affect signaling primarily by modulating intracellular domain geometry. Finally, to guide the design of future receptors, we propose general principles for linking design choices to biophysical mechanisms and performance characteristics.

Building sophisticated sensors of extracellular cues that enable mammalian cells to work as "doctors" in the body

Mammalian cells are inherently capable of sensing extracellular environmental signals and activating complex biological functions on demand. Advances in synthetic biology have made it possible to install additional capabilities, which can allow cells to sense the presence of custom biological molecules and provide defined outputs on demand. When implanted/infused in patients, such engineered cells can work as intrabody "doctors" that diagnose disease states and produce and deliver therapeutic molecules when and where necessary. The key to construction of such theranostic cells is the development of a range of sensor systems for detecting various extracellular environmental cues that can be rewired to custom outputs. In this review, we introduce the state-of-art engineering principles utilized in the design of sensor systems to detect soluble factors and also to detect specific cell contact, and we discuss their potential role in treating intractable diseases by delivering appropriate therapeutic functions on demand. We also discuss the challenges facing these emerging technologies.

The Role of Protein Engineering in Biomedical Applications of Mammalian Synthetic Biology

Engineered proteins with enhanced or altered functionality, generated for example by mutation or domain fusion, are at the core of nearly all synthetic biology endeavors in the context of precision medicine, also known as personalized medicine. From designer receptors sensing elevated blood markers to effectors rerouting signaling pathways to synthetic transcription factors and the customized therapeutics they regulate, engineered proteins play a crucial role at every step of novel therapeutic approaches using synthetic biology. Here, recent developments in protein engineering aided by advances in directed evolution, de novo design, and machine learning are discussed. Building on clinical successes already achieved with chimeric antigen receptor (CAR-) T cells and other cell-based therapies, these developments are expected to further enhance the capabilities of mammalian synthetic biology in biomedical and other applications.

Programmable Synthetic Protein Circuits for the Identification and Suppression of Hepatocellular Carcinoma

Precisely identifying and killing tumor cells are diligent pursuits in oncotherapy. Synthesized gene circuits have emerged as an intelligent weapon to solve these problems. Gene circuits based on post-transcriptional regulation enable a faster response than systems based on transcriptional regulation, which requires transcription and translation, showing superior safety. In this study, synthetic-promoter-free gene circuits possessing two control layers were constructed to improve the specific recognition of tumor cells. Using split-TEV, we designed and verified the basic control layer of protein-protein interaction (PPI) sensing. Another orthogonal control layer was built to sense specific proteins. Two layers were integrated to generate gene circuits sensing both PPI and specific proteins, forming 10 logic gates. To demonstrate the utility of this system, the circuit was engineered to sense alpha-fetoprotein (AFP) expression and the PPI between YAP and 14-3-3σ, the matching profile of hepatocellular carcinoma (HCC). Gene-circuit-loaded cells distinguished HCC from other cells and released therapeutic antibodies, exhibiting in vitro and in vivo therapeutic effects.

Synthetic biology in various cellular and molecular fields: applications, limitations, and perspective

Synthetic biology breakthroughs have facilitated genetic circuit engineering to program cells through novel biological functions, dynamic gene expressions, as well as logic controls. SynBio can also participate in the rapid development of new treatments required for the human lifestyle. Moreover, these technologies are applied in the development of innovative therapeutic, diagnostic, as well as discovery-related methods within a wide range of cellular and molecular applications. In the present review study, SynBio applications in various cellular and molecular fields such as novel strategies for cancer therapy, biosensing, metabolic engineering, protein engineering, and tissue engineering were highlighted and summarized. The major safety and regulatory concerns about synthetic biology will be the environmental release, legal concerns, and risks of the engineered organisms. The final sections focused on limitations to SynBio.

Optogenetic regulation of endogenous proteins

Techniques of protein regulation, such as conditional gene expression, RNA interference, knock-in and knock-out, lack sufficient spatiotemporal accuracy, while optogenetic tools suffer from non-physiological response due to overexpression artifacts. Here we present a near-infrared light-activatable optogenetic system, which combines the specificity and orthogonality of intrabodies with the spatiotemporal precision of optogenetics. We engineer optically-controlled intrabodies to regulate genomically expressed protein targets and validate the possibility to further multiplex protein regulation via dual-wavelength optogenetic control. We apply this system to regulate cytoskeletal and enzymatic functions of two non-tagged endogenous proteins, actin and RAS GTPase, involved in complex functional networks sensitive to perturbations. The optogenetically-enhanced intrabodies allow fast and reversible regulation of both proteins, as well as simultaneous monitoring of RAS signaling with visible-light biosensors, enabling all-optical approach. Growing number of intrabodies should make their incorporation into optogenetic tools the versatile technology to regulate endogenous targets.

The ST2/Interleukin-33 Axis in Hematologic Malignancies: The IL-33 Paradox

Interleukin (IL)-33 is a chromatin-related nuclear interleukin that is a component of IL-1 family. IL-33 production augments the course of inflammation after cell damage or death. It is discharged into the extracellular space. IL-33 is regarded as an “alarmin” able to stimulate several effectors of the immune system, regulating numerous immune responses comprising cancer immune reactions. IL-33 has been demonstrated to influence tumorigenesis. However, as far as this cytokine is concerned, we are faced with what has sometimes been defined as the IL-33 paradox. Several studies have demonstrated a relevant role of IL-33 to numerous malignancies, where it may have pro- and—less frequently—antitumorigenic actions. In the field of hematological malignancies, the role of IL-33 seems even more complex. Although we can affirm the existence of a negative role of IL-33 in Chronic myelogenos leukemia (CML) and in lymphoproliferative diseases and a positive role in pathologies such as Acute myeloid leukemia (AML), the action of IL-33 seems to be multiple and sometimes contradictory within the same pathology. In the future, we will have to learn to govern the negative aspects of activating the IL-33/ST2 axis and exploit the positive ones.

Designing cell function: assembly of synthetic gene circuits for cell biology applications

Synthetic biology is the discipline of engineering application-driven biological functionalities that were not evolved by nature. Early breakthroughs of cell engineering, which were based on ectopic (over)expression of single sets of transgenes, have already had a revolutionary impact on the biotechnology industry, regenerative medicine and blood transfusion therapies. Now, we require larger-scale, rationally assembled genetic circuits engineered to programme and control various human cell functions with high spatiotemporal precision in order to solve more complex problems in applied life sciences, biomedicine and environmental sciences. This will open new possibilities for employing synthetic biology to advance personalized medicine by converting cells into living therapeutics to combat hitherto intractable diseases.

A cell topography-based mechanism for ligand discrimination by the T cell receptor

The T cell receptor (TCR) initiates the elimination of pathogens and tumors by T cells. To avoid damage to the host, the receptor must be capable of discriminating between wild-type and mutated self and nonself peptide ligands presented by host cells. Exactly how the TCR does this is unknown. In resting T cells, the TCR is largely unphosphorylated due to the dominance of phosphatases over the kinases expressed at the cell surface. However, when agonist peptides are presented to the TCR by major histocompatibility complex proteins expressed by antigen-presenting cells (APCs), very fast receptor triggering, i.e., TCR phosphorylation, occurs. Recent work suggests that this depends on the local exclusion of the phosphatases from regions of contact of the T cells with the APCs. Here, we developed and tested a quantitative treatment of receptor triggering reliant only on TCR dwell time in phosphatase-depleted cell contacts constrained in area by cell topography. Using the model and experimentally derived parameters, we found that ligand discrimination likely depends crucially on individual contacts being ∼200 nm in radius, matching the dimensions of the surface protrusions used by T cells to interrogate their targets. The model not only correctly predicted the relative signaling potencies of known agonists and nonagonists but also achieved this in the absence of kinetic proofreading. Our work provides a simple, quantitative, and predictive molecular framework for understanding why TCR triggering is so selective and fast and reveals that, for some receptors, cell topography likely influences signaling outcomes.

Protein-based parts and devices that respond to intracellular and extracellular signals in mammalian cells

Synthetic biology aims to rewire cellular activities and functionality by implementing genetic circuits with high biocomputing capabilities. Recent efforts led to the development of smart sensing interfaces which integrate multiple inputs to activate desired outputs in a highly specific and sensitive manner. In this review, we highlight protein-based interfaces that sense intracellular or extracellular cues providing information about dynamic environmental changes and cellular state. We will also discuss different mechanisms of regulation of gene expression connected to the sensors to develop diagnostic and therapeutic devices. We conclude discussing challenges and opportunities for biomedical applications of synthetic mammalian protein-based devices.

Engineering advanced cancer therapies with synthetic biology

Engineered immune-cell-based cancer therapies have demonstrated robust efficacy in B cell malignancies, but challenges such as the lack of ideal targetable tumour antigens, tumour-mediated immunosuppression and severe toxicity still hinder their therapeutic efficacy and broad applicability. Synthetic biology can be used to overcome these challenges and create more robust, effective adaptive therapies that enable the specific targeting of cancer cells while sparing healthy cells. In this Progress article, we review recently developed gene circuit therapies for cancer using immune cells, nucleic acids and bacteria as chassis. We conclude by discussing outstanding challenges and future directions for realizing these gene circuit therapies in the clinic.

From synthetic biology to human therapy: engineered mammalian cells

Mammalian synthetic biology has evolved to become a key driver of biomedical innovation in the area of cell therapy. Advances in receptor engineering, immunotherapy and cell implants promise new treatment options for complex diseases. Synthetic receptors have already found applications in cellular immunotherapy for cancer treatment, and are being introduced into the field of cell implants. Here, we discuss prospects for the next generation of engineered mammalian cells for human therapy, highlighting selected recent studies.

Synthetic Biology: Engineering Mammalian Cells To Control Cell-to-Cell Communication at Will

Cell-to-cell communication plays a key role in the regulation of many natural biological processes. Recent advances in mammalian synthetic biology are making it possible to rationally engineer cell-to-cell communication for therapeutic and other purposes. Here, we review state-of-the-art engineering principles to control cell-to-cell communication, focusing on communication between mammalian cells with diffusible factors (e.g., small molecules or exosomes) or direct cell contact, and on interkingdom communication between mammalian cells and bacteria. Potential applications include construction of artificial tissues able to perform complex computations, sophisticated cell-based cancer therapies, use of mammalian cells as a new class of cargo delivery modality, development of design principles to control pattern formation of cell populations, and treatment of infectious diseases. We also discuss the challenges facing practical applications, and possible enabling technologies to overcome them.

Engineered Cell-Based Therapeutics: Synthetic Biology Meets Immunology

Synthetic Biology has enabled new approaches to several medical applications including the development of immunotherapies based on bioengineered cells, and most notably the engineering of T-cells with tumor-targeting receptors, the Chimeric Antigen Receptor (CAR)-T cells. CAR-T-cells have successfully treated blood tumors such as large B-cell lymphoma and promise a new scenario of therapeutic interventions also for solid tumors. Learning the lesson from CAR-T cells, we can foster the reprogramming of T lymphocytes with enhanced survival and functional activity in depressing tumor microenvironment, or to challenge diseases such as infections, autoimmune and chronic inflammatory disorders. This review will focus on the most updated bioengineering approaches to increase control, and safety of T-cell activity and to immunomodulate the extracellular microenvironment to augment immune responses. We will also discuss on applications beyond cancer treatment with implications toward the understanding and cure of a broader range of diseases by means of mammalian cells engineering.

Engineering Precision Medicine

Advances in genomic sequencing and bioinformatics have led to the prospect of precision medicine where therapeutics can be advised by the genetic background of individuals. For example, mapping cancer genomics has revealed numerous genes that affect the therapeutic outcome of a drug. Through materials and cell engineering, many opportunities exist for engineers to contribute to precision medicine, such as engineering biosensors for diagnosis and health status monitoring, developing smart formulations for the controlled release of drugs, programming immune cells for targeted cancer therapy, differentiating pluripotent stem cells into desired lineages, fabricating bioscaffolds that support cell growth, or constructing "organs-on-chips" that can screen the effects of drugs. Collective engineering efforts will help transform precision medicine into a more personalized and effective healthcare approach. As continuous progress is made in engineering techniques, more tools will be available to fully realize precision medicine's potential.

A Simply Modified Lymphocyte for Systematic Cancer Therapy

Cytotherapy has received considerable attention in the field of cancer therapy, and various chemical or genetic methods have been applied to remold natural cells for improved therapeutic outcome of cytotherapy. A simple method to modify lymphocytes for cancer treatment by using a clinically used molecule, δ-aminolevulinic acid (δ-ALA), is reported here. After incubation with this molecule, tumor-targeted lymphocytes spontaneously synthesize anti-neoplastic drug protoporphyrin X (PpIX), and specifically accumulate in cancer tissue. Under periodic 630 nm laser irradiation, lymphocytes generate vesicle-like apoptotic body (Ab) containing the above-produced PpIX, and the facilitated delivery of PpIX from Ab makes an excellent therapeutic effect for Ras-mutated cancer cells under a second irradiation. Importantly, a microfluidic device is further fabricated to simplify cell sorting and drug synthesis with a one-step operation, which could promote generalization of this strategy. In vitro and in vivo studies confirm the success of such an easy-operated and global-regulated strategy for cancer therapy.

Engineering Whole Mammalian Cells for Target-Cell-Specific Invasion/Fusion

Live mammalian cells are equipped with a synthetic cell invasion system that enables their target-specific insertion into other live mammalian cells. By conjugating RhoA activator to a transmembrane protein that is segregated from cell-cell interface when specific cell contact occurs, polarization of RhoA activity is synthetically induced inside the cells in response to specific cell contact. This polarization is a sufficient condition for invader cells to selectively penetrate cells expressing a target antigen. Further, when an acid-responsive fusogenic protein is expressed on invader cells, invader/receiver cell fusion occurs after invasion, and the invader's intracellular contents are released into the recipient's cytosol. It is shown that this system can be used for specific cell ablation. This synthetic-biology-inspired cell invasion/fusion system might open the door to using whole mammalian cells for cargo delivery purposes or for ablation of a specific cell type.

Synthetic gene circuits for the detection, elimination and prevention of disease

In living organisms, naturally evolved sensors that constantly monitor and process environmental cues trigger corrective actions that enable the organisms to cope with changing conditions. Such natural processes have inspired biologists to construct synthetic living sensors and signalling pathways, by repurposing naturally occurring proteins and by designing molecular building blocks de novo, for customized diagnostics and therapeutics. In particular, designer cells that employ user-defined synthetic gene circuits to survey disease biomarkers and to autonomously re-adjust unbalanced pathological states can coordinate the production of therapeutics, with controlled timing and dosage. Furthermore, tailored genetic networks operating in bacterial or human cells have led to cancer remission in experimental animal models, owing to the network's unprecedented specificity. Other applications of designer cells in infectious, metabolic and autoimmune diseases are also being explored. In this Review, we describe the biomedical applications of synthetic gene circuits in major disease areas, and discuss how the first genetically engineered devices developed on the basis of synthetic-biology principles made the leap from the laboratory to the clinic.

Interleukin-33 in Malignancies: Friends or Foes?

The human Interleukin-33 (IL-33), a member of the IL-1 family, is the cytokine as a cell endogenous alarmin, released by damaged or necrotic barrier cells (endothelial and epithelial cells). The signal transduction of IL-33 relies on recognition and interaction with specific receptor ST2, mainly expressed in immune cells. In both innate and adoptive immunity, IL-33 regulates the homeostasis in response to stress from within/out the microenvironment. Various, even negative biofunctions of IL-33 pathways have now been widely verified in pathogenesis among immunological mechanisms, like Th2-related immune-stimuli, inflammation/infection-induced tissue protectors. A larger versatility in studies of IL-33 on malignancies now focuses on: (1) promoting myeloid-derived suppressor cells (MDSC), (2) intervention toward CD8⁺ T, Natural Killer (NK) cell infiltration, group 2 innate lymphoid cells (ILC2) proliferation, dendritic cells (DC) activation, and (3) inhibiting tumor growth and/or further metastasis as an immunoadjuvant. Although IL-33 functioned pro-tumorigenically in various cancers, for some cancer types the findings so far are controversial. This review begins from a summarized introduction of IL-33, to its remarkable implications and molecular transduction pathway in malignant neoplasms, ends with latest inspiration for IL-33 in treatment.