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Schematic structure of heavily glycosylated glycoproteins. (a) Proteoglycans are transmembrane glycoproteins that consist of a core protein decorated with glycosaminoglycan (GAG) chains. In glypicans, the protein core is stabilized by disulphide bridges and linked to the cell membrane via GPI-anchors. Both glypicans and syndecans contain serine-linked heparin sulphate and chondroitin sulphate GAGs at both sides of the protein (here only depicted on one side), classifying them as HSPGs. (b) Mucins are high-molecular weight proteins that are extensively decorated with mucin-type O-Glycans, schematically illustrated here by the sTn epitope. Mucins are subdivided into transmembrane (MUC1, MUC3, MUC4, MUC12, MUC13, MUC16, and MUC17) and secreted mucins (MUC2, MUC5AC, MUC5B, and MUC6).
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Distinguishing malignancy from healthy tissue is essential for oncologic surgery. Targeted imaging during an operation aids the surgeon to operate better. The present tracers for detecting cancer are directed against proteins that are overexpressed on the membrane of tumor cells. This review evaluates the use of tumor-associated suga...
Citations
... Malignant transformation is accompanied by changes in tumor cell surface glycoconjugates [13,14], including the aberrant or incomplete glycosylation of heavily glycosylated structures such as mucins and proteoglycans [15]. These structures are often overexpressed and shed from tumor cells, having a strong influence on tumor progression by modulating cell adhesion, neoangiogenesis and metastasis [16]. ...
Functional Tregs play a key role in tumor development and progression, representing a major barrier to anticancer immunity. The mechanisms by which Tregs are generated in cancer and the influence of the tumor microenvironment on these processes remain incompletely understood. Herein, by using NMR, chemoenzymatic structural assays and a plethora of in vitro and in vivo functional analyses, we demonstrate that the tumoral carbohydrate A10 (Ca10), a cell-surface carbohydrate derived from Ehrlich’s tumor (ET) cells, is a heparan sulfate-related proteoglycan that enhances glycolysis and promotes the development of tolerogenic features in human DCs. Ca10-stimulated human DCs generate highly suppressive Tregs by mechanisms partially dependent on metabolic reprogramming, PD-L1, IL-10, and IDO. Ca10 also reprograms the differentiation of human monocytes into DCs with tolerogenic features. In solid ET-bearing mice, we found positive correlations between Ca10 serum levels, tumor size and splenic Treg numbers. Administration of isolated Ca10 also increases the proportion of splenic Tregs in tumor-free mice. Remarkably, we provide evidence supporting the presence of a circulating human Ca10 counterpart (Ca10H) and show, for the first time, that serum levels of Ca10H are increased in patients suffering from different cancer types compared to healthy individuals. Of note, these levels are higher in prostate cancer patients with bone metastases than in prostate cancer patients without metastases. Collectively, we reveal novel molecular mechanisms by which heparan sulfate-related structures associated with tumor cells promote the generation of functional Tregs in cancer. The discovery of this novel structural-functional relationship may open new avenues of research with important clinical implications in cancer treatment.
... In this regard, aberrant glycosylation profiles add to understanding pathological steps of tumor development and progression and have become a hallmark of cancer [4,5]. For example, in the case of colorectal cancer (CRC), aberrant N-glycosylation with regard to the tumor microenvironment is increasingly studied in CRC tissue samples using imaging mass spectrometry (MS) [6][7][8][9]. Other glycomics studies also reported associations of N-glycome alterations with survival and tumor stage in CRC [10][11][12]. ...
A newly developed analytical strategy was applied to profile the total serum N-glycome of 64 colorectal cancer (CRC) patients before and after surgical intervention. In this cohort, it was previously found that serum N-glycome alterations in CRC were associated with patient survival. Here, fluorescent labeling of serum N-glycans was applied using procainamide and followed by sialic acid derivatization specific for α2,6- and α2,3-linkage types via ethyl esterification and amidation, respectively. This strategy allowed efficient separation of specific positional isomers on reversed-phase liquid chromatography–fluorescence detection–mass spectrometry (RPLC-FD-MS) and complemented the previous glycomics data based on matrix-assisted laser desorption/ionization (MALDI)-MS that did not include such separations. The results from comparing pre-operative CRC to post-operative samples were in agreement with studies that identified a decrease in di-antennary structures with core fucosylation and an increase in sialylated tri- and tetra-antennary N-glycans in CRC patient sera. Pre-operative abundances of N-glycans showed good performance for the classification of adenocarcinoma and led to the revisit of the previous MALDI-MS dataset with regard to histological and clinical data. This strategy has the potential to monitor patient profiles before, during, and after clinical events such as treatment, therapy, or surgery and should also be further explored.
... In parallel to commonly studied integrins' or cadherins' involvement in cell adhesion, glycans attract attention due to aberrant glycosylation of proteins and lipids observed in various cancers [36]. Cancer-specific changes can serve as novel targets for various applications, such as targeted tumor imaging [37]. These reports motivate the idea of using lectin-coated surfaces in microfluidic devices to capture cells similar to those demonstrated for cancerous B and T lymphocytes flowing through a post-device, resulting in the lectin-type-dependent attachment of cells [38]. ...
Aberrant expression of glycans, i.e., oligosaccharide moiety covalently attached to proteins or lipids, is characteristic of various cancers, including urothelial ones. The binding of lectins to glycans is classified as molecular recognition, which makes lectins a strong tool for understanding their role in developing diseases. Here, we present a quantitative approach to tracing glycan–lectin interactions in cells, from the initial to the steady phase of adhesion. The cell adhesion was measured between urothelial cell lines (non-malignant HCV29 and carcinoma HT1376 and T24 cells) and lectin-coated surfaces. Depending on the timescale, single-cell force spectroscopy, and adhesion assays conducted in static and flow conditions were applied. The obtained results reveal that the adhesion of urothelial cells to two specific lectins, i.e., phytohemagglutinin-L and wheat germ agglutinin, was specific and selective. Thus, these lectins can be applied to selectively capture, identify, and differentiate between cancer types in a label-free manner. These results open up the possibility of designing lectin-based biosensors for diagnostic or prognostic purposes and developing strategies for drug delivery that could target cancer-associated glycans.
... Cancer cells overexpress a variety of glycosylation patterns in membrane biomolecules like glycoproteins, glycolipids, and the selective recognition of these aberrant glycosylation patterns may provide a basis for the site-specific drug delivery. Sugar antigens expressed in many tumor represent a target for site-specific drug delivery [19]. An increased overexpression of sialylated epitopes on tumour cells causes progression in cancer and poor prognosis in cancers patients [20]. ...
... Clinical imaging of the specific components of the tumor ECM may enable a more direct assessment of disease status, including presurgical tumor margins (Narunsky et al. 2013). ECM components such as fibrillar proteins, collagen and collagen degradation products, fibronectin and glycosaminoglycans (Houvast et al. 2020 ) can all be imaged with or without the use of optical probes. For example, multiple investigators (Brown et al. 2003;Nadiarnykh et al. 2010) have used high-resolution Second Harmonic Generation (SHG) imaging microscopy to quantify differences in the structure of the ECM in both mouse models and in biopsied human tumors. ...
... Targeting glycans may have several benefits compared to protein targeting. Namely, the TACAs are expressed on the cell surface, directly accessible to therapeutics and can be carried by multiple proteins, reflecting the overall glycosylation phenotype of the cell, providing a broader tumor targeting strategy [64]. Ideally, the expression of TACAs is absent or limited in normal colon mucosa. ...
Cells are covered with a dense layer of carbohydrates, some of which are solely present on neoplastic cells. The so-called tumor-associated carbohydrate antigens (TACAs) are increasingly recognized as promising targets for immunotherapy. These carbohydrates differ from those of the surrounding non-cancerous tissues and contribute to the malignant phenotype of the cancer cells by promoting proliferation, metastasis, and immunosuppression. However, due to tumor tissue heterogeneity and technological limitations, TACAs are insufficiently explored.
Methods: A workflow was established to decode the colorectal cancer (CRC)-associated O-linked glycans from approximately 20,000 cell extracts. Extracts were obtained through laser capture microdissection of formalin fixed paraffin embedded tissues of both primary tumors and metastatic sites, and compared to healthy colon mucosa from the same patients. The released O-glycans were analyzed by porous graphitized carbon liquid chromatography-tandem mass spectrometry in negative ion mode.
Results: Distinctive O-glycosylation features were found in cancerous, stromal and normal colon mucosal regions. Over 100 O-linked glycans were detected in cancerous regions with absence in normal mucosa. From those, six core 2 O-glycans were exclusively found in more than 33% of the cancers, carrying the terminal (sialyl-)LewisX/A antigen. Moreover, two O-glycans were present in 72% of the analyzed cancers and 94% of the investigated cancers expressed at least one of these two O-glycans. In contrast, normal colon mucosa predominantly expressed core 3 O-glycans, carrying α2-6-linked sialylation, (sulfo-)LewisX/A and Sda antigens.
Conclusion: In this study, we present a novel panel of highly specific TACAs, based upon differences in the glycomic profiles between CRC and healthy colon mucosa. These TACAs are promising new targets for development of innovative cancer immune target therapies and lay the foundation for the targeted treatment of CRC.
... Thirdly, as atypically-expressed glycans tend to amplify their expression on glycoproteins, glycosylation changes are more reflective of disease process than changes in the proteome (Fuster and Esko 2005;Lebrilla and An 2009). In a similar vein, these characteristics also make cancer-associated glycans ideal candidates for targeted glycan-based tumor imaging and for use as potential cancer glycobiomarkers (i.e. for diagnosis, follow-up, monitoring of therapeutic response, or patient stratification) (Houvast et al. 2020). Moreover, cancer-associated glycans were considered as promising targets for the design of anticancer vaccines but their clinical application was hampered by many obstacles. ...
Unlike cytotoxic chemotherapy, cancer immunotherapy offers targeted therapies that exploit the effector mechanisms of the immune system to combat cancer. However, most therapeutic strategies have so far focused predominantly on the orchestration of the adaptive immune responses to anti-cancer immunotherapies. Unfortunately, the emergence of resistance and associated severe toxicities rendered this modality of treatment imperfect. Because of their complex nature and the late ability to selectively separate distinct innate immune responses, the enormous potential of innate immunity as an immunotherapy was largely neglected. Recently, the growing demand to find alternatives to adaptive immunity-based immunotherapy concurred with growing appreciation of the innate immune effectors contributions to anti-tumor immunity. In particular, the innate immunity anti-infective responses overlap with those that target cancer indicating that these responses can readily be manipulated to design new therapeutic approaches. The paradigm of lectin pathway in recognition of distinct ‘non-self’ (antigenic) glycans on the surface of pathogenic microbes in concert with cancer’s indigenous aberrant (antigenic) glycans render lectin pathway a canonical component of innate immune system that can be extrapolated to cancer immunotherapy. By virtue of recent advances in lectin engineering, the encouraging results of using engineered lectins as anti-viral agents can be replicated in cancer immunotherapy.
... In addition to CA19-9, several CA19-9-related glycans are highly expressed on PDAC tissues, while expression on chronic pancreatitis and healthy pancreatic parenchyma is low or absent. Due to their amplified expression on the outermost layer of the tumor cell, tumor-associated glycans may provide several advantages for tumor targeting beyond proteins [56]. ...
Background:
Despite recent advances in the multimodal treatment of pancreatic ductal adenocarcinoma (PDAC), overall survival remains poor with a 5-year cumulative survival of approximately 10%. Neoadjuvant (chemo- and/or radio-) therapy is increasingly incorporated in treatment strategies for patients with (borderline) resectable and locally advanced disease. Neoadjuvant therapy aims to improve radical resection rates by reducing tumor mass and (partial) encasement of important vascular structures, as well as eradicating occult micrometastases. Results from recent multicenter clinical trials evaluating this approach demonstrate prolonged survival and increased complete surgical resection rates (R0). Currently, tumor response to neoadjuvant therapy is monitored using computed tomography (CT) following the RECIST 1.1 criteria. Accurate assessment of neoadjuvant treatment response and tumor resectability is considered a major challenge, as current conventional imaging modalities provide limited accuracy and specificity for discrimination between necrosis, fibrosis, and remaining vital tumor tissue. As a consequence, resections with tumor-positive margins and subsequent early locoregional tumor recurrences are observed in a substantial number of patients following surgical resection with curative intent. Of these patients, up to 80% are diagnosed with recurrent disease after a median disease-free interval of merely 8 months. These numbers underline the urgent need to improve imaging modalities for more accurate assessment of therapy response and subsequent re-staging of disease, thereby aiming to optimize individual patient's treatment strategy. In cases of curative intent resection, additional intra-operative real-time guidance could aid surgeons during complex procedures and potentially reduce the rate of incomplete resections and early (locoregional) tumor recurrences. In recent years intraoperative imaging in cancer has made a shift towards tumor-specific molecular targeting. Several important molecular targets have been identified that show overexpression in PDAC, for example: CA19.9, CEA, EGFR, VEGFR/VEGF-A, uPA/uPAR, and various integrins. Tumor-targeted PET/CT combined with intraoperative fluorescence imaging, could provide valuable information for tumor detection and staging, therapy response evaluation with re-staging of disease and intraoperative guidance during surgical resection of PDAC.
Methods:
A literature search in the PubMed database and (inter)national trial registers was conducted, focusing on studies published over the last 15 years. Data and information of eligible articles regarding PET/CT as well as fluorescence imaging in PDAC were reviewed. Areas covered: This review covers the current strategies, obstacles, challenges, and developments in targeted tumor imaging, focusing on the feasibility and value of PET/CT and fluorescence imaging for integration in the work-up and treatment of PDAC. An overview is given of identified targets and their characteristics, as well as the available literature of conducted and ongoing clinical and preclinical trials evaluating PDAC-targeted nuclear and fluorescent tracers.
... Within the continuing search for novel targets for molecular imaging, tumor-associated glycans and mucins have gained significant interest (reviewed in [11]). In cancer, many proteins and lipids are aberrantly glycosylated, which results in the appearance of truncated O-glycans, such as sialyl-Thomsen-Nouveau (sTn) and Lewis glycans, such as sialyl-Lewis a (sLe a ) and sialyl-Lewis x (sLe x ), Lewis a/c/x (Le a/c/x) , sialyl-di-Lewis a (sdi-Le a ) and related glyco-epitopes [12][13][14][15]. ...
... In reference to glycans, mucins, which are high-molecular-weight proteins that are extensively coated with O-glycans, seem interesting tumor-specific targets based on their high expression on tumor tissues, low abundance in healthy tissues and pivotal roles in carcinogenesis [18,19] Especially, transmembrane mucin-1 (MUC1) and secreted mucin-5AC (MUC5AC), which are both, directly and indirectly, involved in tumor progression via their truncated sTn glycans, are considered promising targets for PDAC targeting [18]. As a result of mucin overexpression, tumor-associated glycans become strongly amplified on the outermost layer of multiple proteins simultaneously, making them a set of high-potential molecular imaging targets with advantages for targeting beyond proteins [11,20]. Although the aforementioned tumor-associated O-glycans and mucins are strongly expressed on pancreatic cancers cells, their relative expression on (surrounding) chronic pancreatitis as well as on healthy pancreas and duodenum and metastatic lymph nodes, which defines their molecular imaging suitability, is underexplored. ...
... Due to their tumor-specific (over)expression and excellent in vivo accessibility, tumorassociated glycans, which are present on the outermost layer of the cell membrane, are of particular interest for molecular imaging [11]. Several glycan-specific tracers were successfully evaluated for molecular imaging of PDAC in a preclinical setting, but only a few studies have described glycan-based imaging in a clinical context. ...
Targeted molecular imaging may overcome current challenges in the preoperative and intraoperative delineation of pancreatic ductal adenocarcinoma (PDAC). Tumor-associated glycans Lea/c/x, sdi-Lea, sLea, sLex, sTn as well as mucin-1 (MUC1) and mucin-5AC (MU5AC) have gained significant interest as targets for PDAC imaging. To evaluate their PDAC molecular imaging potential, biomarker expression was determined using immunohistochemistry on PDAC, (surrounding) chronic pancreatitis (CP), healthy pancreatic, duodenum, positive (LN+) and negative lymph node (LN−) tissues, and quantified using a semi-automated digital image analysis workflow. Positive expression on PDAC tissues was found on 83% for Lea/c/x, 94% for sdi-Lea, 98% for sLea, 90% for sLex, 88% for sTn, 96% for MUC1 and 67% for MUC5AC, where all were not affected by the application of neoadjuvant therapy. Compared to PDAC, all biomarkers were significantly lower expressed on CP, healthy pancreatic and duodenal tissues, except for sTn and MUC1, which showed a strong expression on duodenum (sTn tumor:duodenum ratio: 0.6, p < 0.0001) and healthy pancreatic tissues (MUC1 tumor:pancreas ratio: 1.0, p > 0.9999), respectively. All biomarkers are suitable targets for correct identification of LN+, as well as the distinction of LN+ from LN− tissues. To conclude, this study paves the way for the development and evaluation of Lea/c/x-, sdi-Lea-, sLea-, sLex- and MUC5AC-specific tracers for molecular imaging of PDAC imaging and their subsequent introduction into the clinic.
... Indeed, the numerous advantages of peptides (such as low cost of production, good stability, and ease of conjugation to the surface of NPs at a high density due to their small size), make them appropriate anti-glycans ligands to target cancer cells. Different examples can be found in the literature [9,88,89]. For instance, Rossez et al. prepared ultrasmall particles of iron oxide (USPIOs) conjugated with disulfide constrained heptapeptide, that were identified using a screening phage display, for the early detection by magnetic resonance imaging (MRI) of colon cancer using human gastric mucin MUC5AC as a specific marker [90]. ...
... The pros and cons of the target, the tumor-associated glycans, are important. TACAs properties offer the following major advantages [88]: (i) their dense epitope expression on a wide range of tumors, but not in healthy tissue, resulting in a denser accumulation of anti-glycan molecules; (ii) their expression on the outermost layer of cell surface layer, making them easily accessible by targeting moieties; (iii) their ability to be expressed in target multiple tumor-associated proteins, then providing a more efficient targeting than single protein targeting. ...
Nanotechnology is in the spotlight of therapeutic innovation, with numerous advantages for tumor visualization and eradication. The end goal of the therapeutic use of nanoparticles, however, remains distant due to the limitations of nanoparticles to target cancer tissue. The functionalization of nanosystem surfaces with biological ligands is a major strategy for directing the actions of nanomaterials specifically to tumor cells. Cancer formation and metastasis are accompanied by profound alterations in protein glycosylation. Hence, the detection and targeting of aberrant glycans are of great value in cancer diagnosis and therapy. In this review, we provide a brief update on recent progress targeting aberrant glycosylation by functionalizing nanoparticles with glycan-binding molecules (with a special focus on lectins and anti-glycan antibodies) to improve the efficacy of nanoparticles in cancer targeting, diagnosis, and therapy and outline the challenges and limitations in implementing this approach. We envision that the combination of nanotechnological strategies and cancer-associated glycan targeting could remodel the field of cancer diagnosis and therapy, including immunotherapy.
