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28 result(s) for "Li, Guideng"
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T cell antigen discovery
T cells respond to threats in an antigen-specific manner using T cell receptors (TCRs) that recognize short peptide antigens presented on major histocompatibility complex (MHC) proteins. The TCR–peptide-MHC interaction mediated between a T cell and its target cell dictates its function and thereby influences its role in disease. A lack of approaches for antigen discovery has limited the fundamental understanding of the antigenic landscape of the overall T cell response. Recent advances in high-throughput sequencing, mass cytometry, microfluidics and computational biology have led to a surge in approaches to address the challenge of T cell antigen discovery. Here, we summarize the scope of this challenge, discuss in depth the recent exciting work and highlight the outstanding questions and remaining technical hurdles in this field.A review on recent method development for discovering T cell antigens.
Multi-omic single-cell snapshots reveal multiple independent trajectories to drug tolerance in a melanoma cell line
The determination of individual cell trajectories through a high-dimensional cell-state space is an outstanding challenge for understanding biological changes ranging from cellular differentiation to epigenetic responses of diseased cells upon drugging. We integrate experiments and theory to determine the trajectories that single BRAF V600E mutant melanoma cancer cells take between drug-naive and drug-tolerant states. Although single-cell omics tools can yield snapshots of the cell-state landscape, the determination of individual cell trajectories through that space can be confounded by stochastic cell-state switching. We assayed for a panel of signaling, phenotypic, and metabolic regulators at points across 5 days of drug treatment to uncover a cell-state landscape with two paths connecting drug-naive and drug-tolerant states. The trajectory a given cell takes depends upon the drug-naive level of a lineage-restricted transcription factor. Each trajectory exhibits unique druggable susceptibilities, thus updating the paradigm of adaptive resistance development in an isogenic cell population. Detailed understanding of how cancer cells transition from a drug sensitive to a tolerant state is lacking. Here, using single cell proteomic and metabolic data the authors uncover that isogenic BRAF mutant melanoma cells can take two distinct paths to become tolerant to BRAF inhibition.
Metabolic plasticity of T cell fate decision
Abstract The efficacy of adaptive immune responses in cancer treatment relies heavily on the state of the T cells. Upon antigen exposure, T cells undergo metabolic reprogramming, leading to the development of functional effectors or memory populations. However, within the tumor microenvironment (TME), metabolic stress impairs CD8+ T cell anti-tumor immunity, resulting in exhausted differentiation. Recent studies suggested that targeting T cell metabolism could offer promising therapeutic opportunities to enhance T cell immunotherapy. In this review, we provide a comprehensive summary of the intrinsic and extrinsic factors necessary for metabolic reprogramming during the development of effector and memory T cells in response to acute and chronic inflammatory conditions. Furthermore, we delved into the different metabolic switches that occur during T cell exhaustion, exploring how prolonged metabolic stress within the TME triggers alterations in cellular metabolism and the epigenetic landscape that contribute to T cell exhaustion, ultimately leading to a persistently exhausted state. Understanding the intricate relationship between T cell metabolism and cancer immunotherapy can lead to the development of novel approaches to improve the efficacy of T cell-based treatments against cancer.
Bi-directional metabolic reprogramming between cancer cells and T cells reshapes the anti-tumor immune response
Cancer cells and T cells engage in dynamic crosstalk within the tumor microenvironment (TME), shaping tumor progression and anti-tumor immunity. While cancer cells reprogram metabolism to support growth and immune evasion, T cells must adapt their metabolic states to maintain effector functions. Tumor-driven metabolic perturbations, such as nutrient depletion and accumulation of immunosuppressive metabolites, profoundly impair T cell function and fate. Conversely, metabolically reprogrammed T cells can modulate the TME and influence tumor growth. This reciprocal metabolic crosstalk represents both metabolic competition and intercellular communication, offering promising therapeutic targets.
T cell antigen discovery via signaling and antigen-presenting bifunctional receptors
CD8+ T cells recognize and eliminate tumors in an antigen-specific manner. Despite progress in characterizing the antitumor T cell repertoire and function, the identification of target antigens remains a challenge. Here we describe the use of chimeric receptors called signaling and antigen-presenting bifunctional receptors (SABRs) in a cell-based platform for T cell receptor (TCR) antigen discovery. SABRs present an extracellular complex comprising a peptide and major histocompatibility complex (MHC), and induce intracellular signaling via a TCR-like signal after binding with a cognate TCR. We devised a strategy for antigen discovery using SABR libraries to screen thousands of antigenic epitopes. We validated this platform by identifying the targets recognized by public TCRs of known specificities. Moreover, we extended this approach for personalized neoantigen discovery.Engineered, bifunctional receptors present antigens and initiate signaling in response to binding to the cognate T cell receptor. Libraries built with SABRs can screen thousands of epitopes for the discovery of T cell target antigens.
T cell antigen discovery via trogocytosis
T cell receptor (TCR) ligand discovery is essential for understanding and manipulating immune responses to tumors. We developed a cell-based selection platform for TCR ligand discovery that exploits a membrane transfer phenomenon called trogocytosis. We discovered that T cell membrane proteins are transferred specifically to target cells that present cognate peptide–major histocompatibility complex (MHC) molecules. Co-incubation of T cells expressing an orphan TCR with target cells collectively presenting a library of peptide–MHCs led to specific labeling of cognate target cells, enabling isolation of these target cells and sequencing of the cognate TCR ligand. We validated this method for two clinically employed TCRs and further used the platform to identify the cognate neoepitope for a subject-derived neoantigen-specific TCR. Thus, target cell trogocytosis is a robust tool for TCR ligand discovery that will be useful for studying basic tumor immunology and identifying new targets for immunotherapy.Trogocytosis, the uptake of membrane proteins by an antigen-presenting cell from its cognate T cell, allows the identification of neoepitopes targeted by T cell receptors with high sensitivity.
Alternative mRNA splicing in cancer immunotherapy
Immunotherapies are yielding effective treatments for several previously untreatable cancers. Still, the identification of suitable antigens specific to the tumour that can be targets for cancer vaccines and T cell therapies is a challenge. Alternative processing of mRNA, a phenomenon that has been shown to alter the proteomic diversity of many cancers, may offer the potential of a broadened target space. Here, we discuss the promise of analysing mRNA processing events in cancer cells, with an emphasis on mRNA splicing, for the identification of potential new targets for cancer immunotherapy. Further, we highlight the challenges that must be overcome for this new avenue to have clinical applicability.
Cytosporone B is an agonist for nuclear orphan receptor Nur77
Nuclear orphan receptor Nur77 has important roles in many biological processes. However, a physiological ligand for Nur77 has not been identified. Here, we report that the octaketide cytosporone B (Csn-B) is a naturally occurring agonist for Nur77. Csn-B specifically binds to the ligand-binding domain of Nur77 and stimulates Nur77-dependent transactivational activity towards target genes including Nr4a1 ( Nur77 ) itself, which contains multiple consensus response elements allowing positive autoregulation in a Csn-B–dependent manner. Csn-B also elevates blood glucose levels in fasting C57 mice, an effect that is accompanied by induction of multiple genes involved in gluconeogenesis. These biological effects were not observed in Nur77-null ( Nr4a1 −/− ) mice, which indicates that Csn-B regulates gluconeogenesis through Nur77. Moreover, Csn-B induced apoptosis and retarded xenograft tumor growth by inducing Nur77 expression, translocating Nur77 to mitochondria to cause cytochrome c release. Thus, Csn-B may represent a promising therapeutic drug for cancers and hypoglycemia, and it may also be useful as a reagent to increase understanding of Nur77 biological function.
Deciphering Membrane‐Protein Interactions and High‐Throughput Antigen Identification with Cell Doublets
Deciphering cellular interactions is essential to both understand the mechanisms underlying a broad range of human diseases, but also to manipulate therapies targeting these diseases. Here, the formation of cell doublets resulting from specific membrane ligand‐receptor interactions is discovered. Based on this phenomenon, the study developed DoubletSeeker, a novel high‐throughput method for the reliable identification of ligand‐receptor interactions. The study shows that DoubletSeeker can accurately identify T cell receptor (TCR)‐antigen interactions with high sensitivity and specificity. Notably, DoubletSeeker effectively captured paired TCR‐peptide major histocompatibility complex (pMHC) information during a highly complex library‐on‐library screening and successfully identified three mutant TCRs that specifically recognize the MART‐1 epitope. In turn, DoubletSeeker can act as an antigen discovery platform that allows for the development of novel immunotherapy targets, making it valuable for investigating fundamental tumor immunology. This study introduces DoubletSeeker, an innovative method to screen ligand‐receptor interactions by examining the formation of cell doublets from membrane protein interactions. DoubletSeeker demonstrates efficiency in identifying various ligand‐receptor interactions, such as TCRs and pMHCs, with high sensitivity and specificity. Notably, when coupled with single‐doublet sequencing technology, DoubletSeeker enables the decoding of paired TCR‐pMHC information in a library‐on‐library screening approach.
A novel small molecule RAD51 inactivator overcomes imatinib‐resistance in chronic myeloid leukaemia
RAD51 recombinase activity plays a critical role for cancer cell proliferation and survival, and often contributes to drug‐resistance. Abnormally elevated RAD51 function and hyperactive homologous recombination (HR) rates have been found in a panel of cancers, including breast cancer and chronic myeloid leukaemia (CML). Directly targeting RAD51 and attenuating the deregulated RAD51 activity has therefore been proposed as an alternative and supplementary strategy for cancer treatment. Here we show that a newly identified small molecule, IBR2, disrupts RAD51 multimerization, accelerates proteasome‐mediated RAD51 protein degradation, reduces ionizing radiation‐induced RAD51 foci formation, impairs HR, inhibits cancer cell growth and induces apoptosis. In a murine imatinib‐resistant CML model bearing the T315I Bcr‐abl mutation, IBR2, but not imatinib, significantly prolonged animal survival. Moreover, IBR2 effectively inhibits the proliferation of CD34 + progenitor cells from CML patients resistant to known BCR‐ABL inhibitors. Therefore, small molecule inhibitors of RAD51 may suggest a novel class of broad‐spectrum therapeutics for difficult‐to‐treat cancers. Graphical Abstract A newly identified RAD51 inhibitor leading to degradation of RAD51 via the proteasome pathway inhibits cancer cell survival and greatly increases life spans in a mouse chronic myeloid leukaemia model.