Our Research & Initiatives

Research in our laboratory integrates synthetic chemistry with glycobiology to explore the cellular and molecular mechanisms that control immune responses to cancer and human pathogens. We focus on developing chemoenzymatic tools to study these processes and engineer the cell surface of immune cells for therapeutic applications.

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Our early work focused on the development of chemical tools to investigate the relevance of protein glycosylation in human disease. The glycome, the complete set of glycans produced by a cell, regulates key physiological processes such as angiogenesis, fertilization, stem cell development, and neuronal function. Glycosylation changes serve as informative biomarkers for cancer and inflammation. Unlike proteins and nucleic acids, glycans are not directly encoded by the genome but are synthesized through stepwise enzymatic reactions. As a result, traditional genetic and biochemical approaches alone cannot fully characterize the glycome. To address this challenge, we develop complementary chemical tools for both “bottom-up” and “top-down” glycan analysis. Two key chemical tools developed by my lab are:

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• Biocompatible copper catalysts for Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC)—a cornerstone of click chemistry—enabling proteomic analysis and in vivo biomolecule labeling, now widely adopted by over 200 labs worldwide.

• Chemoenzymatic methods for detecting and modifying cell-surface glycans, facilitating functional studies and therapeutic applications.

 

These tools have enabled glycan imaging in living organisms, led to the discovery of novel disease biomarkers, and opened new therapeutic avenues. Major discoveries enabled by these tools include:

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• The discovery of fucosylated glycans as alternative receptors for influenza virus, expanding the known set of host-virus interactions beyond sialylated glycans.

• Increased N-glycan α1,3-fucosylation enhances Wnt co-receptor Lrp6 endocytosis, suppressing Wnt-β-catenin signaling.

• Mutation of the cloche gene reduces fucosylation in zebrafish embryogenesis. Supplementing fucose or GDP-fucose partially rescues this defect, significantly extending mutant lifespans.

• A 13-fold decrease in N-acetyllactosamine (LacNAc) expression in early-stage lung adenocarcinoma, suggesting LacNAc as a potential early diagnostic marker.​

 

In these studies, we discovered that H. pylori α1-3-fucosyltransferase possesses a previously unappreciated donor substrate scope: it is able of transferring biopolymers, such as a full-length antibody, to LacNAc, the most common glycan building block, in the glycocalyx of live cells when the antibody is conjugated to the enzyme’s natural donor substrate GDP-fucose. This process is specific, quantitative, and fast with little interference to cells’ endogenous functions. To the best of our knowledge, this is the first example of a promiscuous glycosyltransferase that can accept an unnatural nucleotide sugar donor (molecular weight = 589) conjugated to a protein (molecular weight = 150 kD).

Exploiting the unprecedented substrate scope of this enzyme, we developed a simple and cost-effective technique to fabricate antibody-cell conjugates (ACCs) using primary immune cells and NK-92MI cells that are currently in clinical trials as an “off-the-shelf therapeutic” for cancer immunotherapy. NK-92MI cells lack Fc receptors that are required for antibody-dependent cell-mediated cytotoxicity (ADCC) to induce specific cell lysis, which significantly limited their therapeutic applications. By incorporating the HER2-specific antibody Herceptin onto NK-92MI cells via the chemoenzymatic approach, we endowed the modified NK-92MI cells with specific targeting abilities. The resulting Herceptin-NK-92MI conjugates exhibit remarkably enhanced activities to induce the lysis of HER2+ cancer cells both ex vivo and in vivo in a human tumor xenograft model. This technique offers several advantages over genetic-based engineering, e.g., rapid modification, the capability to install multiple functional molecules simultaneously, and therefore serves as a nice complement to the permanent, genetic engineering approach.

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From the above studies, we found ourselves in a unique position to contribute new tools that would propel the field of immunobiology, and this has been the theme of my group at Scripps for the past nine years. We are developing chemical tools to explore the cellular and molecular mechanisms that control immune responses toward cancer and human pathogens with a focus on the following unsolved problems in immunology: What are the compositions and properties of tumor-specific antigen (TSA)-reactive and bystander tumor-infiltrating lymphocytes (TILs) in the tumor microenvironment? How to address the on-target, off-tumor toxicity of chimeric antigen receptor (CAR)-T cells? Can we enhance effector function and longevity of T cells for treating chronic infection and cancer? And how to overcome the immunosuppressive tumor microenvironment to treat solid tumors?

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