Design of a mucin-selective protease for targeted degradation of cancer-associated mucins

Pulmonary mucinous adenocarcinoma: An overview of pathophysiology and advancements in treatment

Pulmonary mucinous adenocarcinoma (PMA), a distinct subtype of non-small cell lung cancer (NSCLC), is characterized by an abundance of mucin-producing cells. Although this subtype comprises a relatively small fraction of lung adenocarcinomas, PMA stands apart due to its unique clinical, pathological, and molecular features. This review comprehensively discusses the pathophysiology and etiology, clinical features, diagnostic methods, treatment strategies, prognosis, and future directions for PMA, drawing from relevant literature and existing studies. Advances in PMA treatment includes surgical intervention, targeted therapy, immunotherapy, and adjuvant therapy. Particularly, we discussed factors influencing the prognosis of PMAs, such as molecular markers, pathological features, and the impact of the latest treatment advances on prognosis. Moreover, we intended this review to be a comprehensive reference for diagnosing, treating, and assessing the prognosis of PMA, providing valuable guidance for clinical practice.

Imaging the extracellular matrix in live tissues and organisms with a glycan-binding fluorophore

All multicellular systems produce and dynamically regulate extracellular matrices (ECM) that play important roles in both biochemical and mechanical signaling. Though the spatial arrangement of these extracellular assemblies is critical to their biological functions, visualization of ECM structure is challenging, in part because the biomolecules that compose the ECM are difficult to fluorescently label individually and collectively. Here, we present a cell-impermeable small molecule fluorophore, termed Rhobo6, that turns on and red shifts upon reversible binding to glycans. Given that most ECM components are densely glycosylated, the dye enables wash-free visualization of ECM, in systems ranging from in vitro substrates to in vivo mouse mammary tumors. Relative to existing techniques, Rhobo6 provides a broad substrate profile, superior tissue penetration, nonperturbative labeling, and negligible photobleaching. This work establishes a straightforward method for imaging the distribution of ECM in live tissues and organisms, lowering barriers for investigation of extracellular biology.

Chemoproteomics reveals immunogenic and tumor-associated cell surface substrates of ectokinase CK2α

New epitopes for immune recognition provide the basis of anticancer immunity. Due to the high concentration of extracellular adenosine triphosphate in the tumor microenvironment, we hypothesized that extracellular kinases (ectokinases) could have dysregulated activity and introduce aberrant phosphorylation sites on cell surface proteins. We engineered a cell-tethered version of the extracellular kinase CK2α, demonstrated it was active on cells under tumor-relevant conditions, and profiled its substrate scope using a chemoproteomic workflow. We then demonstrated that mice developed polyreactive antisera in response to syngeneic tumor cells that had been subjected to surface hyperphosphorylation with CK2α. Interestingly, these mice developed B cell and CD4+ T cell responses in response to these antigens but failed to develop a CD8+ T cell response. This work provides a workflow for probing the extracellular phosphoproteome and demonstrates that extracellular phosphoproteins are immunogenic even in a syngeneic system.

Immunoengineering can overcome the glycocalyx armour of cancer cells

Cancer cell glycocalyx is a major line of defence against immune surveillance. However, how specific physical properties of the glycocalyx are regulated on a molecular level, contribute to immune evasion and may be overcome through immunoengineering must be resolved. Here we report how cancer-associated mucins and their glycosylation contribute to the nanoscale material thickness of the glycocalyx and consequently modulate the functional interactions with cytotoxic immune cells. Natural-killer-cell-mediated cytotoxicity is inversely correlated with the glycocalyx thickness of the target cells. Changes in glycocalyx thickness of approximately 10 nm can alter the susceptibility to immune cell attack. Enhanced stimulation of natural killer and T cells through equipment with chimeric antigen receptors can improve the cytotoxicity against mucin-bearing target cells. Alternatively, cytotoxicity can be enhanced through engineering effector cells to display glycocalyx-editing enzymes, including mucinases and sialidases. Together, our results motivate the development of immunoengineering strategies that overcome the glycocalyx armour of cancer cells.

Two in one: the emerging concept of bifunctional antibodies

Therapeutic antibodies have become indispensable for treating a wide range of diseases, and their significance in drug discovery has expanded considerably over the past few decades. Bifunctional antibodies are now emerging as a promising new drug modality to address previously unmet needs in antibody therapeutics. Distinct from traditional antibodies that operate through an 'occupancy-based' inhibition mechanism, these innovative molecules recruit the protein of interest to a 'biological effector,' initiating specific downstream consequences such as targeted protein degradation or posttranslational modifications. In this review, we emphasize the potential of bifunctional antibodies to tackle diverse biomedical challenges.

Extracellular targeted protein degradation: an emerging modality for drug discovery

Targeted protein degradation (TPD) has emerged in the past decade as a major new drug modality to remove intracellular proteins with bispecific small molecules that recruit the protein of interest (POI) to an E3 ligase for degradation in the proteasome. Unlike classic occupancy-based drugs, intracellular TPD (iTPD) eliminates the target and works catalytically, and so can be more effective and sustained, with lower dose requirements. Recently, this approach has been expanded to the extracellular proteome, including both secreted and membrane proteins. Extracellular targeted protein degradation (eTPD) uses bispecific antibodies, conjugates or small molecules to degrade extracellular POIs by trafficking them to the lysosome for degradation. Here, we focus on recent advances in eTPD, covering degrader systems, targets, molecular designs and parameters to advance them. Now almost any protein, intracellular or extracellular, is addressable in principle with TPD.

The glycoimmune checkpoint receptor Siglec-7 interacts with T-cell ligands and regulates T-cell activation

Siglec-7 (sialic acid-binding immunoglobulin-like lectin 7) is a glycan-binding immune receptor that is emerging as a significant target of interest for cancer immunotherapy. The physiological ligands that bind Siglec-7, however, remain incompletely defined. In this study, we characterized the expression of Siglec-7 ligands on peripheral immune cell subsets and assessed whether Siglec-7 functionally regulates interactions between immune cells. We found that disialyl core 1 O-glycans are the major immune ligands for Siglec-7 and that these ligands are particularly highly expressed on naïve T-cells. Densely glycosylated sialomucins are the primary carriers of these glycans, in particular a glycoform of the cell-surface marker CD43. Biosynthesis of Siglec-7-binding glycans is dynamically controlled on different immune cell subsets through a genetic circuit involving the glycosyltransferase GCNT1. Siglec-7 blockade was found to increase activation of both primary T-cells and antigen-presenting dendritic cells in vitro, indicating that Siglec-7 binds T-cell glycans to regulate intraimmune signaling. Finally, we present evidence that Siglec-7 directly activates signaling pathways in T-cells, suggesting a new biological function for this receptor. These studies conclusively demonstrate the existence of a novel Siglec-7-mediated signaling axis that physiologically regulates T-cell activity. Going forward, our findings have significant implications for the design and implementation of therapies targeting immunoregulatory Siglec receptors.

COLLAGEN MINERALIZATION DECREASES NK CELL-MEDIATED CYTOTOXICITY OF BREAST CANCER CELLS VIA INCREASED GLYCOCALYX THICKNESS

Skeletal metastasis is common in patients with advanced breast cancer, and often caused by immune evasion of disseminated tumor cells (DTCs). In the skeleton, tumor cells not only disseminate to the bone marrow, but also to osteogenic niches in which they interact with newly mineralizing bone extracellular matrix (ECM). However, it remains unclear how mineralization of collagen type I, the primary component of bone ECM, regulates tumor-immune cell interactions. Here, we have utilized a combination of synthetic bone matrix models with controlled mineral content, nanoscale optical imaging, and flow cytometry to evaluate how collagen type I mineralization affects the biochemical and biophysical properties of the tumor cell glycocalyx, a dense layer of glycosylated proteins and lipids decorating their cell surface. Our results suggest that collagen mineralization upregulates mucin-type O-glycosylation and sialylation by tumor cells, which increased their glycocalyx thickness while enhancing resistance to attack by Natural Killer (NK) cells. These changes were functionally linked as treatment with a sialylation inhibitor decreased mineralization-dependent glycocalyx thickness and made tumor cells more susceptible to NK cell attack. Together, our results suggest that interference with glycocalyx sialylation may represent a therapeutic strategy to enhance cancer immunotherapies targeting bone-metastatic breast cancer.

Cell surface sculpting using logic-gated protein actuators

Cell differentiation and tissue specialization lead to unique cellular surface landscapes and exacerbated or loss of expression patterns can result in further heterogenicity distinctive of pathological phenotypes1-3. Immunotherapies and emerging protein therapeutics seek to exploit such differences by engaging cell populations selectively based on their surface markers. Since a single surface antigen rarely defines a specific cell type4,5, the development of programmable molecular systems that integrate multiple cell surface features to convert on-target inputs to user-defined outputs is highly desirable. Here, we describe an autonomous decision-making protein device driven by proximity-gated protein trans-splicing that allows local generation of an active protein from two otherwise inactive fragments. We show that this protein actuator platform can perform various Boolean logic operations on cell surfaces, allowing highly selective recruitment of enzymatic and cytotoxic activities to specific cells within mixed populations. Due to its intrinsic modularity and tunability, this technology is expected to be compatible with different types of inputs, targeting modalities and functional outputs, and as such will have broad application in the synthetic biology and biotechnology areas.

Shearing of surface mucin saps tumor cell strength

Aberrant expression of transmembrane mucins promotes tumor progression and interferes with immunological and medicinal elimination of cancer cells. In a recent article, Pedram et al. directed an attenuated bacterial mucin-specific protease to HER2-positive tumor cells and observed decreased tumor growth rates and extended survival of mice bearing HER2-positive tumors.