Clustered carbohydrates as a target for natural killer cells: a model system

Triply Enhanced Immunotherapy via Dual Glycan Reforming Integrated with Perforation

The enhancement of immunotherapy is an emerging direction to develop highly effective and practical cancer therapeutic methods. Here a triply enhanced immunotherapy drug (TEID) is designed for ingeniously integrating in situ dual glycan reforming with perforation on cell membrane. The TEID is composed of galactose and neuraminidase conjugated streptolysin O (SLO-Gal and SLO-NEU), which are encapsulated in a hyaluronic acid (HA) shell for targeted recognition to tumor tissue via cell surface CD44. After targeted delivery and HAase-mediated degradation in the tumor region, the TEID releases SLO-Gal and SLO-NEU, which can easily anchor Gal and NEU on the tumor cell membrane via the perforation of SLO to perform dual glycan reforming for the introduction of Gal and the cleavage of sialic acid. The former can activate immune cells to secret cytokines for immune-killing, and the latter can weaken the immune inhibition to improve the immunotherapeutic efficacy. Meanwhile, the perforation of SLO can promote the delivery of cytokines into the tumor cells to further enhance the efficacy. The designed triply enhanced immunotherapy strategy opens a significant and promising route to promote clinical immunotherapy of cancer.

Research progress in leveraging biomaterials for enhancing NK cell immunotherapy

NK cell immunotherapy is a promising antitumor therapeutic modality after the development of T cell immunotherapy. Structural modification of NK cells with biomaterials may provide a precise, efficient, and low-cost strategy to enhance NK cell immunotherapy. The biomaterial modification of NK cells can be divided into two strategies: surface engineering with biomaterials and intracellular modification. The surface engineering strategies include hydrophobic interaction of lipids, receptor-ligand interaction between membrane proteins, covalent binding to amino acid residues, click reaction and electrostatic interaction. The intracellular modification strategies are based on manipulation by nanotechnology using membranous materials from various sources of NK cells (such as exosome, vesicle and cytomembranes). Finally, the biomaterials-based strategies regulate the recruitment, recognition and cytotoxicity of NK cells in the solid tumor site in situ to boost the activity of NK cells in the tumor. This article reviews the recent research progress in enhancing NK cell therapy based on biomaterial modification, to provide a reference for further researches on engineering NK cell therapy with biomaterials.

Membrane-Fusion-Mediated Multiplex Engineering of Tumor Cell Surface Glycans for Enhanced NK Cell Therapy

Natural killer (NK) cell therapies show potential for tumor treatment but are immunologically resisted by the overexpressed immunosuppressing tumor cell surface glycans. To reverse this glycan-mediated immunosuppression, the surface NK-inhibitory glycan expressions need to be downregulated and NK-activating glycan levels should be elevated synchronously with optimal efficiency. Here, a core-shell membrane-fusogenic liposome (MFL) is designed to simultaneously achieve the physical modification of NK-activating glycans and biological inhibition of immunosuppressing glycans on the tumor cell surface via a membrane-fusion manner. Loaded into a tumor-microenvironment-triggered-degradable thermosensitive hydrogel, MFLs could be conveniently injected and controllably released into local tumor. Through fusion with tumor cell membrane, the released MFLs could simultaneously deliver sialyltransferase-inhibitor-loaded core into cytoplasm, and anchor NK-activating-glycan-modified shell onto tumor surface. This spatially-differential distribution of core and shell in one cell ensures the effective inhibition of intracellular sialyltransferase to downregulate immunosuppressing sialic acid, and direct presentation of NK-activating Lewis X trisaccharide (LeX) on tumor surface simultaneously. Consequentially, the sialic acid-caused immunosuppression of tumor surface is reprogrammed to be LeX-induced NK activation, resulting in sensitive susceptibility to NK-cell-mediated recognition and lysis for improved tumor elimination. This MFL provides a novel platform for multiplex cell engineering and personalized regulation of intercellular interactions for enhanced cancer immunotherapy.

Bacterial lipopolysaccharide activates CD57-negative human NK cells

NK cells play an important regulatory role in sepsis by induction and augmentation of proinflammatory reactions in early stages of the septic process and by suppression of immune response in later stages of inflammation. The present work was aimed at the effect of bacterial lipopolysaccharide (LPS), the main pathogenic factor of sepsis development, on human NK cells ex vivo. We show that LPS activates immature CD57-negative NK cells, which typically constitute less than half of the normal NK cell population in human peripheral blood. Under conditions of NK cell stimulation with IL-2, addition of LPS provokes an increase in IFN-γ production. However, LPS both increased and inhibited NK cell cytotoxic activity. It is important to note that the activation of NK cells on LPS addition was observed in the absence of TLR4 on the NK cell surface. These results confirm our previous data arguing for a direct interaction of LPS with NK cells and evidence an atypical mechanism of LPS-induced NK cell activation without the involvement of surface TLR4.

Tumor-Associated Glycans and Immune Surveillance

Changes in cell surface glycosylation are a hallmark of the transition from normal to inflamed and neoplastic tissue. Tumor-associated carbohydrate antigens (TACAs) challenge our understanding of immune tolerance, while functioning as immune targets that bridge innate immune surveillance and adaptive antitumor immunity in clinical applications. T-cells, being a part of the adaptive immune response, are the most popular component of the immune system considered for targeting tumor cells. However, for TACAs, T-cells take a back seat to antibodies and natural killer cells as first-line innate defense mechanisms. Here, we briefly highlight the rationale associated with the relative importance of the immune surveillance machinery that might be applicable for developing therapeutics.