Functions and Inhibition of Galectin-7, an Emerging Target in Cellular Pathophysiology

Development of Galectin-7-Specific Nanobodies: Implications for Immunotherapy and Molecular Imaging in Cancer

Galectins play significant roles in regulating immune responses, posing challenges for cancer immunotherapy. The development of galectin inhibitors has been limited by their high structural homology and the lack of noninvasive imaging tools to identify potential responsive patients. We developed 12 galectin-7-specific inhibitors using nanobodies (Nbs) and identified G7N8 as the lead Nb. G7N8 was conjugated with the NOTA chelator, labeled with copper-64 ([64Cu]Cu), and used as a radiotracer for PET imaging in a triple-negative breast cancer (TNBC) mouse model. Nbs demonstrated high affinity for galectin-7, with no binding activity for other galectins tested. The lead Nbs inhibited galectin-7 binding to T-cell glycoreceptors and reduced subsequent apoptosis. PET imaging with [64Cu]Cu-NOTA-G7N8 showed selective radiotracer accumulation at 20 h (P = 0.001). We developed galectin-7-specific Nbs that inhibit T-cell apoptosis and enable PET imaging of TNBC, providing novel tools for investigating immune regulation and enhancing cancer immunotherapy.

Multifaceted roles of Galectins: from carbohydrate binding to targeted cancer therapy

Galectins play pivotal roles in cellular recognition and signaling processes by interacting with glycoconjugates. Extensive research has highlighted the significance of Galectins in the context of cancer, aiding in the identification of biomarkers for early detection, personalized therapy, and predicting treatment responses. This review offers a comprehensive overview of the structural characteristics, ligand-binding properties, and interacting proteins of Galectins. We delve into their biological functions and examine their roles across various cancer types. Galectins, characterized by a conserved carbohydrate recognition domain (CRD), are divided into prototype, tandem-repeat, and chimera types based on their structural configurations. Prototype Galectins contain a single CRD, tandem-repeat Galectins contain two distinct CRDs linked by a peptide, and the chimera-type Galectin-3 features a unique structural arrangement. The capacity of Galectins to engage in multivalent interactions allows them to regulate a variety of signaling pathways, thereby affecting cell fate and function. In cancer, Galectins contribute to tumor cell transformation, angiogenesis, immune evasion, and metastasis, making them critical targets for therapeutic intervention. This review discusses the multifaceted roles of Galectins in cancer progression and explores current advancements in the development of Galectin-targeted therapies. We also address the challenges and future directions for integrating Galectin research into clinical practice to enhance cancer treatment outcomes. In brief, understanding the complex functions of Galectins in cancer biology opens new avenues for therapeutic strategies. Continued research on Galectin interactions and their pathological roles is essential for developing effective carbohydrate-based treatments and improving clinical interventions for cancer patients.

Tear Protein Biomarkers for Ocular Mucous Membrane Pemphigoid Uncovered Using Targeted LC-MS/MS

Mucous membrane pemphigoid (MMP) is a multisystemic rare autoimmune disease affecting the skin and mucous membranes. Ocular involvement is characterized by chronic conjunctival inflammation causing scar formation, leading to corneal opacification and vision loss. Conjunctival biopsies are currently used to confirm diagnosis, and the associated immunosuppression treatments prescribed can have serious consequences on patients. To address these challenges, a noninvasive approach to collect patient tears using untargeted and targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses has been developed to identify a list of potential biomarkers of ocular MMP. Samples were collected on Schirmer strips and subjected to tryptic digestion and LC-MS/MS analysis. Three cohorts of patients were studied, and targeted LC-scheduled multiple reaction monitoring (LC-sMRM) methods were developed for the verification of putative biomarkers. The comparison of three groups of patients, those diagnosed with ocular MMP, non-ocular MMP, and lichen planus, another ocular cicatricial conjunctivitis disorder, yielded 56 biomarkers of interest. Proteins distinguishing MMP patients with and without ocular involvement were linked to the extracellular matrix, metabolism, and neutrophil degranulation. The comparison between MMP and lichen planus patients highlighted lower levels of metabolic enzymes in the latter. This study highlights the use of multiple patient cohorts and tailored targeted quantitative proteomics methods for the discovery of biomarkers for diagnostic and prognostic purposes.

Exploring Glycan-Lectin Interactions in Natural-Like Environments: A View Using NMR Experiments Inside Cell and on Cell Surface

Glycan-mediated molecular recognition events are essential for life. NMR is widely used to monitor glycan binding to lectins in solution using isolated glycans and lectins. In this context, we herein explore diverse NMR methodologies, from both the receptor and ligand perspectives, to monitor glycan-lectin interactions under experimental conditions mimicking the native milieu inside cells and on cell surface. For the NMR experiments inside cells, galectin-7 is employed as model, since most galectins are soluble and carry out their functions in the cellular micro-environment. Using Danio Rerio oocytes, the 1H-15N HMQC NMR spectrum of a folded galectin has been observed inside cell for the first time, using a glycomimetic ligand (TDG) to overcoming the natural tendency of galectins to bind to numerous galactose-containing receptors within cells. Alternatively, most lectins, other than galectins, are displayed on the cell surface, providing a multivalent presentation to bind their glycan partners in cis (at the same cell) or in trans (on other cells). In this case, ligand-based STD-NMR experiments have been successfully applied to account for the interactions of natural glycans and glycomimetics with Siglec-10. These methodologies provide the proof-of-concept to open the door to the NMR analysis of the recognition of glycans in native-like settings.

Galectin-7 Expression in the Placentas of Women with Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a common condition during pregnancy. The prevalence of GDM is continuously increasing worldwide. Due to accessible diagnostic methods and a clear understanding of risk factors, GDM can be effectively diagnosed and managed. Galectins may influence immunomodulatory and inflammatory processes. This study examines the expression of galectin-7 in the placentas of women with gestational diabetes (GDM), compares it to its expression in healthy pregnancies, and evaluates the associated clinical outcomes. The placentas of 40 healthy women and 40 GDM placentas were included in the cohort. The expression level of galecin-7 was measured in the syncytiotrophoblast (SCT) and in the decidua of the placenta by immunohistochemistry and double immunofluorescence staining. The evaluation was performed by an immunoreactivity score (IRS). The study results show an increased expression of galectin-7 in the SCT and the decidua of GDM placentas as compared to the placentas of the control group. Elevated levels of galectin-7 were observed in both the nucleus and the cytoplasm. This study investigated the hypothesis that galectins are involved in pathophysiological processes of gestational diabetes. Statistical analysis of gene expression patterns confirmed that galectin-7 is indeed upregulated in GDM placentas. Further studies are needed to show the correlation of galectin-7 and the development and maintenance of gestational diabetes mellitus.

The Role of Galectins in Asthma Pathophysiology: A Comprehensive Review

Galectins are a group of β-galactoside-binding proteins with several roles in immune response, cellular adhesion, and inflammation development. Current evidence suggest that these proteins could play a crucial role in many respiratory diseases such as pulmonary fibrosis, lung cancer, and respiratory infections. From this standpoint, an increasing body of evidence have recognized galectins as potential biomarkers involved in several aspects of asthma pathophysiology. Among them, galectin-3 (Gal-3), galectin-9 (Gal-9), and galectin-10 (Gal-10) are the most extensively studied in human and animal asthma models. These galectins can affect T helper 2 (Th2) and non-Th2 inflammation, mucus production, airway responsiveness, and bronchial remodeling. Nevertheless, while higher Gal-3 and Gal-9 concentrations are associated with a stronger degree of Th-2 phlogosis, Gal-10, which forms Charcot-Leyden Crystals (CLCs), correlates with sputum eosinophilic count, interleukin-5 (IL-5) production, and immunoglobulin E (IgE) secretion. Finally, several galectins have shown potential in clinical response monitoring after inhaled corticosteroids (ICS) and biologic therapies, confirming their potential role as reliable biomarkers in patients with asthma.

Galectin-7 reprograms skin carcinogenesis by fostering innate immune evasive programs

Non-melanoma skin cancer (NMSC) has risen dramatically as a result of chronic exposure to sunlight ultraviolet (UV) radiation, climatic changes and clinical conditions associated with immunosuppression. In spite of considerable progress, our understanding of the mechanisms that control NMSC development and their associated molecular and immunological landscapes is still limited. Here we demonstrated a critical role for galectin-7 (Gal-7), a β-galactoside-binding protein preferentially expressed in skin tissue, during NMSC development. Transgenic mice (Tg46) overexpressing Gal-7 in keratinocytes showed higher number of papillomas compared to WT mice or mice lacking Gal-7 (Lgals7-/-) when subjected to a skin carcinogenesis protocol, in which tumor initiator 7,12-dimethylbenz[a]anthracene (DMBA) and tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) were sequentially administered. RNAseq analysis of Tg46 tumor lesions revealed a unique profile compatible with cells of the myelomonocytic lineage infiltrating these tumors, an effect that was substantiated by a higher number of CD11b+Gr1+ cells in tumor-draining lymph nodes. Heightened c-Met activation and Cxcl-1 expression in Tg46 lesions suggested a contribution of this pathway to the recruitment of these cells. Remarkably, Gal-7 bound to the surface of CD11b+Ly6ChiLy6Glo monocytic myeloid cells and enhanced their immunosuppressive activity, as evidenced by increased IL-10 and TGF-β1 secretion, and higher T-cell inhibitory activity. In vivo, carcinogen-treated Lgals7-/- animals adoptively transferred with Gal-7-conditioned monocytic myeloid cells developed higher number of papillomas, whereas depletion of these cells in Tg46-treated mice led to reduction in the number of tumors. Finally, human NMSC biopsies showed increased LGALS7 mRNA and Gal-7 protein expression and displayed transcriptional profiles associated with myeloid programs, accompanied by elevated CXCL1 expression and c-Met activation. Thus, Gal-7 emerges as a critical mediator of skin carcinogenesis and a potential therapeutic target in human NMSC.

Galectin functions in cancer-associated inflammation and thrombosis

Galectins are carbohydrate-binding proteins that regulate many cellular functions including proliferation, adhesion, migration, and phagocytosis. Increasing experimental and clinical evidence indicates that galectins influence many steps of cancer development by inducing the recruitment of immune cells to the inflammatory sites and modulating the effector function of neutrophils, monocytes, and lymphocytes. Recent studies described that different isoforms of galectins can induce platelet adhesion, aggregation, and granule release through the interaction with platelet-specific glycoproteins and integrins. Patients with cancer and/or deep-venous thrombosis have increased levels of galectins in the vasculature, suggesting that these proteins could be important contributors to cancer-associated inflammation and thrombosis. In this review, we summarize the pathological role of galectins in inflammatory and thrombotic events, influencing tumor progression and metastasis. We also discuss the potential of anti-cancer therapies targeting galectins in the pathological context of cancer-associated inflammation and thrombosis.

Identification of Galectin-7 as a crucial metastatic enhancer of squamous cell carcinoma associated with immunosuppression

Metastasis predicts poor prognosis in cancer patients. It has been recognized that specific tumor microenvironment defines cancer cell metastasis, whereas the underlying mechanisms remain elusive. Here we show that Galectin-7 is a crucial mediator of metastasis associated with immunosuppression. In a syngeneic mouse squamous cell carcinoma (SCC) model of NR-S1M cells, we isolated metastasized NR-S1M cells from lymph nodes in tumor-bearing mice and established metastatic NR-S1M cells in in vitro culture. RNA-seq analysis revealed that interferon gene signature was markedly downregulated in metastatic NR-S1M cells compared with parental cells, and in vivo NR-S1M tumors heterogeneously developed focal immunosuppressive areas featured by deficiency of anti-tumor immune cells. Spatial transcriptome analysis (Visium) for the NR-S1M tumors revealed that various pro-metastatic genes were significantly upregulated in immunosuppressive areas when compared to immunocompetent areas. Notably, Galectin-7 was identified as a novel metastasis-driving factor. Galectin-7 expression was induced during tumorigenesis particularly in the microenvironment of immunosuppression, and extracellularly released at later stage of tumor progression. Deletion of Galectin-7 in NR-S1M cells significantly suppressed lymph node and lung metastasis without affecting primary tumor growth. Therefore, Galectin-7 is a crucial mediator of tumor metastasis of SCC, which is educated in the immune-suppressed tumor areas, and may be a potential target of cancer immunotherapy.

Galectin Family Members: Emerging Novel Targets for Lymphoma Therapy?

The galectin family of proteins has high affinity with β-galactoside-containing glycans. These proteins participate in cell growth and differentiation, cell adhesion, cell signal transduction, cell apoptosis, and other cellular activities. In recent years, a large number of studies have described the expression and correlation of galectins in different tumors. Each member of the family plays a vital role in tumor growth, progression, angiogenesis, adhesion, and tumor immune escape. Studies on the roles of galectins in lymphoma have mainly involved galectin-1, -3, -7, and -9. The results suggest that galectins may become novel targets for precise tumor treatment. This article reviews current research progress regarding galectins in lymphoma and provides new ideas for exploring them as novel targets for treating lymphoma and other important medical issues.

Inhibition of Galectin-3 Impairs Antifungal Immune Response in Fungal Keratitis

Galectin-3 is one of the galectin family members which are master regulators of immune homeostasis, especially in infectious diseases. However, its mechanism of immune regulation in fungal keratitis has not been thoroughly studied. Our study is aimed at clarifying the role of galectin-3 in the fungal keratitis mouse model in vivo, thereby providing a new biomarker of antifungal therapy. In our study, aspergillus, the most common pathogenic fungi of fungal keratitis, was identified and isolated by corneal tissue fungus culture. Then, the RNA expression levels of galectin family members in corneas of the mouse model with aspergillus fumigatus keratitis were screened by transcriptome sequencing (RNA-seq). The expression of the galectin-3 was detected by quantitative real-time Polymerase Chain Reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence in the corneal tissue of the fungal keratitis mouse model. Recruitment of neutrophils and the co-immunofluorescence of galectin-3 and related markers in corneal tissue were determined by flow cytometry analysis and immunofluorescence staining. The regulatory role of galectin-3 for proinflammatory cytokines and neutrophils was validated by the knockout mouse model. Galectin-3 knockout deteriorated the condition for the inhibition of galectin-3 was benefecial for fungi to survive and thrive in corneal lesions. These results demonstrated that in the ocular fungal infection, galectin-3 is capable of regulating the pathogenesis of fungal keratitis by modulating neutrophil recruitment. The deterioration of fungal keratitis and increased fungal load in corneal lesions of galectin-3 knockout mice proved the regulatory role of galectin-3 in fungal keratitis. In conclusion, galectin-3 is going to be an essential target to modulate neutrophil recruitment and its related antifungal immune response in fungal keratitis.