Differential glycosylation of MUC1 and CEACAM5 between normal mucosa and tumour tissue of colon cancer patients

Decoding the glycoproteome: a new frontier for biomarker discovery in cancer

Cancer early detection and treatment response prediction continue to pose significant challenges. Cancer liquid biopsies focusing on detecting circulating tumor cells (CTCs) and DNA (ctDNA) have shown enormous potential due to their non-invasive nature and the implications in precision cancer management. Recently, liquid biopsy has been further expanded to profile glycoproteins, which are the products of post-translational modifications of proteins and play key roles in both normal and pathological processes, including cancers. The advancements in chemical and mass spectrometry-based technologies and artificial intelligence-based platforms have enabled extensive studies of cancer and organ-specific changes in glycans and glycoproteins through glycomics and glycoproteomics. Glycoproteomic analysis has emerged as a promising tool for biomarker discovery and development in early detection of cancers and prediction of treatment efficacy including response to immunotherapies. These biomarkers could play a crucial role in aiding in early intervention and personalized therapy decisions. In this review, we summarize the significant advance in cancer glycoproteomic biomarker studies and the promise and challenges in integration into clinical practice to improve cancer patient care.

Different glycosylation profiles of cystatin F alter the cytotoxic potential of natural killer cells

Cystatin F, a cysteine peptidase inhibitor, is a potent modulator of NK cytotoxicity. By inhibiting granule-mediated cytotoxicity pathway, cystatin F induces formation of non-functional NK cell stage, called split-anergy. We show that N-glycosylation determines the localization and cellular function of cystatin F. Cystatin F mostly exhibited high-mannose glycosylation in U-937 cells, both high-mannose and complex glycosylation in NK-92 and primary NKs, and predominantly complex glycosylation in super-charged NKs. Manipulating N-glycosylation with kifunensine increased high-mannose glycosylation of cystatin F and lysosome localisation, which decreased cathepsin C activity and reduced NK cytotoxicity. Mannose-6-phosphate could significantly reduce the internalization of extracellular cystatin F. By comparing NK cells with different cytotoxic potentials, we found that high-mannose cystatin F was strongly associated with lysosomes and cathepsin C in NK-92 cell line. In contrast, in highly cytotoxic super-charged NKs, cystatin F with complex glycosylation was associated with the secretory pathway and less prone to inhibit cathepsin C. Modulating glycosylation to alter cystatin F localisation could increase the cytotoxicity of NK cells, thereby enhancing their therapeutic potential for treating cancer patients.

Capitalizing glycomic changes for improved biomarker-based cancer diagnostics

Cancer serum biomarkers are valuable or even indispensable for cancer diagnostics and/or monitoring and, currently, many cancer serum markers are routinely used in the clinic. Most of those markers are glycoproteins, carrying cancer-specific glycan structures that can provide extra-information for cancer monitoring. Nonetheless, in the majority of cases, this differential feature is not exploited and the corresponding analytical assays detect only the protein amount, disregarding the analysis of the aberrant glycoform. Two exceptions to this trend are the biomarkers α-fetoprotein (AFP) and cancer antigen 19-9 (CA19-9), which are clinically monitored for their cancer-related glycan changes, and only the AFP assay includes quantification of both the protein amount and the altered glycoform. This narrative review demonstrates, through several examples, the advantages of the combined quantification of protein cancer biomarkers and the respective glycoform analysis, which enable to yield the maximum information and overcome the weaknesses of each individual analysis. This strategy allows to achieve higher sensitivity and specificity in the detection of cancer, enhancing the diagnostic power of biomarker-based cancer detection tests.

The hidden potential of glycomarkers: Glycosylation studies in the service of cancer diagnosis and treatment

Changes in the glycosylation process appear early in carcinogenesis and evolve with the growth and spread of cancer. The correlation of the characteristic glycosylation signature with the tumor stage and the appropriate therapy choice is an important issue in translational medicine. Oncologists also pay attention to extracellular vesicles as reservoirs of new cancer glycomarkers that can be potent for cancer diagnosis/prognosis. In this review, we recall glycomarkers used in oncology and show their new glycoforms of improved clinical relevance. We summarize current knowledge on the biological functions of glycoepitopes in cancer-derived extracellular vesicles and their potential use in clinical practice. Is glycomics a future of cancer diagnosis? It may be, but in combination with other omics analyses than alone.

The Glycosylated N-Terminal Domain of MUC1 Is Involved in Chemoresistance by Modulating Drug Permeation Across the Plasma Membrane

Mucin 1 (MUC1) is aberrantly expressed in various cancers and implicated in cancer progression and chemoresistance. Although the C-terminal cytoplasmic tail of MUC1 is involved in signal transduction, promoting chemoresistance, the role of the extracellular MUC1 domain [N-terminal glycosylated domain (NG)-MUC1] remains unclear. In this study, we generated stable MCF7 cell lines expressing MUC1 and cytoplasmic tail-deficient MUC1 (MUC1ΔCT) and show that NG-MUC1 is involved in drug resistance by modulating the transmembrane permeation of various compounds without cytoplasmic tail signaling. Heterologous expression of MUC1ΔCT increased cell survival in treating anticancer drugs (such as 5-fluorouracil, cisplatin, doxorubicin, and paclitaxel), in particular by causing an approximately 150-fold increase in the IC₅₀ of paclitaxel, a lipophilic drug, compared with the control [5-fluorouracil (7-fold), cisplatin (3-fold), and doxorubicin (18-fold)]. The uptake studies revealed that accumulations of paclitaxel and Hoechst 33342, a membrane-permeable nuclear staining dye, were reduced to 51% and 45%, respectively, in cells expressing MUC1ΔCT via ABCB1/P-gp-independent mechanisms. Such alterations in chemoresistance and cellular accumulation were not observed in MUC13-expressing cells. Furthermore, we found that MUC1 and MUC1ΔCT increased the cell-adhered water volume by 2.6- and 2.7-fold, respectively, suggesting the presence of a water layer on the cell surface created by NG-MUC1. Taken together, these results suggest that NG-MUC1 acts as a hydrophilic barrier element against anticancer drugs and contributes to chemoresistance by limiting the membrane permeation of lipophilic drugs. Our findings could help better the understanding of the molecular basis of drug resistance in cancer chemotherapy. SIGNIFICANCE STATEMENT: Membrane-bound mucin (MUC1), aberrantly expressed in various cancers, is implicated in cancer progression and chemoresistance. Although the MUC1 cytoplasmic tail is involved in proliferation-promoting signal transduction thereby leading to chemoresistance, the significance of the extracellular domain remains unclear. This study clarifies the role of the glycosylated extracellular domain as a hydrophilic barrier element to limit the cellular uptake of lipophilic anticancer drugs. These findings could help better the understanding of the molecular basis of MUC1 and drug resistance in cancer chemotherapy.

High-Throughput Glycomic Methods

Glycomics aims to identify the structure and function of the glycome, the complete set of oligosaccharides (glycans), produced in a given cell or organism, as well as to identify genes and other factors that govern glycosylation. This challenging endeavor requires highly robust, sensitive, and potentially automatable analytical technologies for the analysis of hundreds or thousands of glycomes in a timely manner (termed high-throughput glycomics). This review provides a historic overview as well as highlights recent developments and challenges of glycomic profiling by the most prominent high-throughput glycomic approaches, with N-glycosylation analysis as the focal point. It describes the current state-of-the-art regarding levels of characterization and most widely used technologies, selected applications of high-throughput glycomics in deciphering glycosylation process in healthy and disease states, as well as future perspectives.

The Role of C-Type Lectin Receptor Signaling in the Intestinal Microbiota-Inflammation-Cancer Axis

As a subset of pattern recognition receptors (PRRs), C-type lectin-like receptors (CLRs) are mainly expressed by myeloid cells as both transmembrane and soluble forms. CLRs recognize not only pathogen associated molecular patterns (PAMPs), but also damage-associated molecular patterns (DAMPs) to promote innate immune responses and affect adaptive immune responses. Upon engagement by PAMPs or DAMPs, CLR signaling initiates various biological activities in vivo, such as cytokine secretion and immune cell recruitment. Recently, several CLRs have been implicated as contributory to the pathogenesis of intestinal inflammation, which represents a prominent risk factor for colorectal cancer (CRC). CLRs function as an interface among microbiota, intestinal epithelial barrier and immune system, so we firstly discussed the relationship between dysbiosis caused by microbiota alteration and inflammatory bowel disease (IBD), then focused on the role of CLRs signaling in pathogenesis of IBD (including Mincle, Dectin-3, Dectin-1, DCIR, DC-SIGN, LOX-1 and their downstream CARD9). Given that CLRs mediate intricate inflammatory signals and inflammation plays a significant role in tumorigenesis, we finally highlight the specific effects of CLRs on CRC, especially colitis-associated cancer (CAC), hoping to open new horizons on pathogenesis and therapeutics of IBD and CAC.

Extracellular vesicles expressing CEACAM proteins in the urine of bladder cancer patients

Early detection and long‐term monitoring are important for urothelial carcinoma of the bladder (UCB). Urine cytology and existing markers have insufficient diagnostic performance. Here, we examined medium‐sized extracellular vesicles (EVs) in urine to identify specific markers for UCB and evaluated their usefulness as diagnostic material. To identify specific markers in urinary EVs derived from UCB, we undertook shotgun proteomics using urine from four UCB patients and four healthy subjects. Next, 29 healthy specimens, 18 noncancer specimens, and 33 UCB specimens, all from men, were analyzed for urinary EVs by flow cytometry to evaluate the diagnostic performance of UCB‐specific EVs. Nanoparticle‐tracking analysis indicated that the size of EVs extracted from urine was mostly <400 nm. By shotgun proteomics, we detected several proteins characteristic of UCB and found that carcinoembryonic antigen‐related adhesion molecule (CEACAM) proteins were increased in patients. Flow cytometric analysis revealed that the degree of expression of CEACAM1, CEACAM5, and CEACAM6 proteins on the surface of EVs varied among patients. Extracellular vesicles expressing CEACAM proteins also expressed mucin 1, suggesting that they were derived from tumorigenic uroepithelial cells. The number of EVs expressing CEACAM1, 5, and 6 proteins was significantly increased in UCB (mean ± SD, 8.6 ± 13%) compared to non‐UCB (0.69 ± 0.46) and healthy (0.46 ± 0.34) by flow cytometry. The results of receiver operating characteristic (ROC) analysis showed a good score of area under the ROC curve of 0.907. We identified EVs that specifically express CEACAM proteins in urine and have potential for diagnostic applications. These EVs are potential targets in a new liquid biopsy test for UCB patients.

Advances in the Immunomodulatory Properties of Glycoantigens in Cancer

Simple Summary

This work reviews the role of aberrant glycosylation in cancer cells during tumour growth and spreading, as well as in immune evasion. The interaction of tumour-associated glycans with the immune system through C-type lectin receptors can favour immune escape but can also provide opportunities to develop novel tumour immunotherapy strategies. This work highlights the main findings in this area and spotlights the challenges that remain to be investigated.

Abstract

Aberrant glycosylation in tumour progression is currently a topic of main interest. Tumour-associated carbohydrate antigens (TACAs) are expressed in a wide variety of epithelial cancers, being both a diagnostic tool and a potential treatment target, as they have impact on patient outcome and disease progression. Glycans affect both tumour-cell biology properties as well as the antitumor immune response. It has been ascertained that TACAs affect cell migration, invasion and metastatic properties both when expressed by cancer cells or by their extracellular vesicles. On the other hand, tumour-associated glycans recognized by C-type lectin receptors in immune cells possess immunomodulatory properties which enable tumour growth and immune response evasion. Yet, much remains unknown, concerning mechanisms involved in deregulation of glycan synthesis and how this affects cell biology on a major level. This review summarises the main findings to date concerning how aberrant glycans influence tumour growth and immunity, their application in cancer treatment and spotlights of unanswered challenges remaining to be solved.

Abnormal sialylation and fucosylation of saliva glycoproteins: Characteristics of lung cancer-specific biomarkers

Dysregulated surface glycoproteins play an important role in tumor cell proliferation and progression. Abnormal glycosylation of these glycoproteins may activate tumor signal transduction and lead to tumor development. The tumor microenvironment alters its molecular composition, some of which regulate protein glycosylation biosynthesis. The glycosylation of saliva proteins in lung cancer patients is different from healthy controls, in which the glycans of cancer patients are highly sialylated and hyperfucosylated. Most studies have shown that O-glycans from cancer are truncated O-glycans, while N-glycans contain fucoses and sialic acids. Because glycosylation analysis is challenging, there are few reports on how glycosylation of saliva proteins is related to the occurrence or progression of lung cancer. In this review, we discussed glycoenzymes involved in protein glycosylation, their changes in tumor microenvironment, potential tumor biomarkers present in body fluids, and abnormal glycosylation of saliva or lung glycoproteins. We further explored the effect of glycosylation changes on tumor signal transduction, and emphasized the role of receptor tyrosine kinases in tumorigenesis and metastasis.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

Expression of estrogen-related receptors in ovarian cancer and impact on survival

PURPOSE

This study further approaches the role of estrogen-related receptors (ERRs) in ovarian cancer. Protein expression of ERRα, ERRβ and ERRγ in ovarian cancer was assessed and was correlated with ovarian cancer markers, steroid hormone receptors and cancer-associated genes. Additionally, we examined to what extent expression of ERRs affects survival of ovarian cancer patients.

METHODS

For this purpose, we established a tissue microarray from 208 ovarian cancer patients and performed immunohistochemical analyses of the mentioned proteins.

RESULTS

ERRα and ERRγ protein could be detected at different levels in more than 90% of all ovarian cancer tissues, whereas expression of ERRβ was observed in 82.2% of the cases. ERRα was found to positively correlate with ovarian cancer marker CEA (p < 0.005) and ERRγ correlated with ERα (p < 0.001). Univariate survival analyses revealed that ERRα expression did not affect overall (OS) or progression-free survival (PFS) of ovarian cancer patients. In contrast, higher expression of ERRβ in serous ovarian cancers was found to lead to a significantly decreased OS (p < 0.05). The strongest impact on survival was exhibited by ERRγ. Lower expression of this receptor in women with serous ovarian cancers indicated significantly increased OS compared to those with higher levels of ERRγ (p < 0.05). Multivariate survival analyses revealed ERRγ as an independent prognostic marker regarding OS of patients with serous ovarian cancer.

CONCLUSION

Our data demonstrating that ERR proteins are frequently expressed in ovarian cancer and high levels of ERRβ and ERRγ significantly decreased OS of serous ovarian cancer patients suggest that these proteins might be interesting therapy targets in this cancer entity.

Carcinoembryonic antigen as a specific glycoprotein ligand of rBC2LCN lectin on pancreatic ductal adenocarcinoma cells

The rBC2LCN lectin, known as a stem cell marker probe that binds to an H type 3 fucosylated trisaccharide motif, was recently revealed to also bind to pancreatic ductal adenocarcinoma (PDAC) cells. A lectin‐drug conjugate was generated by fusing rBC2LCN with a cytocidal toxin, and it showed a strong anticancer effect in in vitro and in vivo PDAC models. However, it is unclear which molecules are carrier proteins of rBC2LCN on PDAC cells. In this study, we identified a rBC2LCN‐positive glycoprotein expressed in PDAC. Tumor lysates of PDAC patient‐derived xenografts (PDXs) were coprecipitated with rBC2LCN lectin and analyzed by liquid chromatography–mass spectrometry. A total of 343 proteins were initially identified. We used a web‐based database to select five glycoproteins and independently evaluated their expression in PDAC by immunohistochemistry (IHC). Among them, we focused on carcinoembryonic antigen 5 (CEA) as the most cancer‐specific carrier protein in PDAC, as it showed the most prominent difference in expression rate between PDAC cells (74%) and normal pancreatic duct cells (0%, P > .0001). rBC2LCN lectin and CEA colocalization in PDAC samples was confirmed by double‐staining analysis. Furthermore, rBC2LCN‐precipitated fractions were blotted with an anti‐CEA polyclonal antibody (pAb), and CEA pAb–precipitated fractions were blotted with rBC2LCN lectin. The results demonstrate that CEA is in fact a ligand of rBC2LCN lectin.

C1GALT1 in health and disease

O-linked glycosylation (O-glycosylation) and N-linked glycosylation (N-glycosylation) are the two most important forms of protein glycosylation, which is an important post-translational modification. The regulation of protein function involves numerous mechanisms, among which protein glycosylation is one of the most important. Core 1 synthase glycoprotein-N-acetylgalactosamine 3-β-galactosyltransferase 1 (C1GALT1) serves an important role in the regulation of O-glycosylation and is an essential enzyme for synthesizing the core 1 structure of mucin-type O-glycans. Furthermore, C1GALT1 serves a vital role in a number of biological functions, such as angiogenesis, platelet production and kidney development. Impaired C1GALT1 expression activity has been associated with different types of human diseases, including inflammatory or immune-mediated diseases, and cancer. O-glycosylation exists in normal tissues, as well as in tumor tissues. Previous studies have revealed that changes in the level of glycosyltransferase in different types of cancer may be used as potential therapeutic targets. Currently, numerous studies have reported the dual role of C1GALT1 in tumors (carcinogenesis and cancer suppression). The present review reports the role of C1GALT1 in normal development and human diseases. Since the mechanism and regulation of C1GALT1 and O-glycosylation remain elusive, further studies are required to elucidate their effects on development and disease.

The Role of Glycosyltransferases in Colorectal Cancer

Colorectal cancer (CRC) is one of the main causes of cancer death in the world. Post-translational modifications (PTMs) have been extensively studied in malignancies due to its relevance in tumor pathogenesis and therapy. This review is focused on the dysregulation of glycosyltransferase expression in CRC and its impact in cell function and in several biological pathways associated with CRC pathogenesis, prognosis and therapeutic approaches. Glycan structures act as interface molecules between cells and their environment and in several cases facilitate molecule function. CRC tissue shows alterations in glycan structures decorating molecules, such as annexin-1, mucins, heat shock protein 90 (Hsp90), β1 integrin, carcinoembryonic antigen (CEA), epidermal growth factor receptor (EGFR), insulin-like growth factor-binding protein 3 (IGFBP3), transforming growth factor beta (TGF-β) receptors, Fas (CD95), PD-L1, decorin, sorbin and SH3 domain-containing protein 1 (SORBS1), CD147 and glycosphingolipids. All of these are described as key molecules in oncogenesis and metastasis. Therefore, glycosylation in CRC can affect cell migration, cell–cell adhesion, actin polymerization, mitosis, cell membrane repair, apoptosis, cell differentiation, stemness regulation, intestinal mucosal barrier integrity, immune system regulation, T cell polarization and gut microbiota composition; all such functions are associated with the prognosis and evolution of the disease. According to these findings, multiple strategies have been evaluated to alter oligosaccharide processing and to modify glycoconjugate structures in order to control CRC progression and prevent metastasis. Additionally, immunotherapy approaches have contemplated the use of neo-antigens, generated by altered glycosylation, as targets for tumor-specific T cells or engineered CAR (Chimeric antigen receptors) T cells.

Research progress on O-GlcNAcylation in the occurrence, development, and treatment of colorectal cancer

For a long time, colorectal cancer (CRC) has been ranked among the top cancer-related mortality rates, threatening human health. As a significant post-translational modification, O-GlcNAcylation plays an essential role in complex life activities. Related studies have found that the occurrence, development, and metastasis of CRC are all related to abnormal O-GlcNAcylation and participate in many critical biological processes, such as gene transcription, signal transduction, cell growth, and differentiation. Recently, nucleotide sugar analogs, tumor-specific carbohydrate vaccine, SIRT1 longevity gene, dendritic cells as targets, and NOTCH gene have become effective methods to induce antitumor therapy. Not long ago, checkpoint kinase 1 and checkpoint kinase 2 were used as therapeutic targets for CRC, but there are still many problems to be solved. With an in-depth study of protein chip, mass spectrometry, chromatography, and other technologies, O-GlcNAcylation research will accelerate rapidly, which may provide new ideas for the research and development of antitumor drugs and the discovery of new CRC diagnostic markers.

Identification of hub genes associated with adult acute myeloid leukemia progression through weighted gene co-expression network analysis

Acute myeloid leukemia (AML) is a malignancy of hematopoietic stem cells. Although many candidate genes such as CEBPA, FLT3, IDH1, and IDH2 have been associated with AML initiation and prognosis, the molecular mechanisms underlying this disease remain unclear. In this study, we used a systemic co-expression analysis method, namely weighted gene co-expression network analysis (WGCNA), to identify new candidate genes associated with adult AML progression and prognosis. We identified around 5,138 differentially expressed genes (DEGs) between AML samples (from The Cancer Genome Atlas database) and normal control samples (from the Genotype-Tissue Expression database). WGCNA identified nine co-expression modules with significant differences based on the DEGs. Among modules, the turquoise and blue ones were the most relevant to AML (P-value: turquoise 0, blue 4.64E-77). GO term and KEGG pathway analyses revealed that pathways that are commonly dysregulated in AML were all enriched in the blue and turquoise modules. A total of 15 hub genes were identified to be crucial for AML progression. PIVOT analysis revealed non-coding RNAs, transcriptional factors, and drugs associated with the hub genes. Finally, survival analysis revealed that one of the hub genes, CEACAM5, was significantly associated with AML prognosis and could serve as a potential target for AML treatment.

Site-Specific N-Linked Glycosylation Analysis of Human Carcinoembryonic Antigen by Sheathless Capillary Electrophoresis-Tandem Mass Spectrometry

With 28 potential N-glycosylation sites, human carcinoembryonic antigen (CEA) bears an extreme amount of N-linked glycosylation, and approximately 60% of its molecular mass can be attributed to its carbohydrates. CEA is often overexpressed and released by many solid tumors, including colorectal carcinomas. CEA displays an impressive heterogeneity and variability in sugar content; however, site-specific distribution of carbohydrate structures has not been reported so far. The present study investigated CEA samples purified from human colon carcinoma and human liver metastases and enabled the characterization of 21 out of 28 potential N-glycosylation sites with respect to their occupancy. The coverage was achieved by a multienzymatic digestion approach with specific enzymes, such as trypsin, endoproteinase Glu-C, and the nonspecific enzyme, Pronase, followed by analysis using sheathless CE-MS/MS. In total, 893 different N-glycopeptides and 128 unique N-glycan compositions were identified. Overall, a great heterogeneity was found both within (micro) and in between (macro) individual N-glycosylation sites. Moreover, notable differences were found on certain N-glycosylation sites between primary adenocarcinoma and metastatic tumor in regard to branching, bisection, sialylation, and fucosylation. Those features, if further investigated in a targeted manner, may pave the way toward improved diagnostics and monitoring of colorectal cancer progression and recurrence. Raw mass spectrometric data and Skyline processed data files that support the findings of this study are available in the MassIVE repository with the identifier MSV000086774 [DOI: 10.25345/C5Z50X].

Mucin-Type O-GalNAc Glycosylation in Health and Disease

Mucin-type GalNAc O-glycosylation is one of the most abundant and unique post-translational modifications. The combination of proteome-wide mapping of GalNAc O-glycosylation sites and genetic studies with knockout animals and genome-wide analyses in humans have been instrumental in our understanding of GalNAc O-glycosylation. Combined, such studies have revealed well-defined functions of O-glycans at single sites in proteins, including the regulation of pro-protein processing and proteolytic cleavage, as well as modulation of receptor functions and ligand binding. In addition to isolated O-glycans, multiple clustered O-glycans have an important function in mammalian biology by providing structural support and stability of mucins essential for protecting our inner epithelial surfaces, especially in the airways and gastrointestinal tract. Here the many O-glycans also provide binding sites for both endogenous and pathogen-derived carbohydrate-binding proteins regulating critical developmental programs and helping maintain epithelial homeostasis with commensal organisms. Finally, O-glycan changes have been identified in several diseases, most notably in cancer and inflammation, where the disease-specific changes can be used for glycan-targeted therapies. This chapter will review the biosynthesis, the biology, and the translational perspectives of GalNAc O-glycans.

Identification of Tn antigen O-GalNAc-expressing glycoproteins in human carcinomas using novel anti-Tn recombinant antibodies

The Tn antigen is a neoantigen abnormally expressed in many human carcinomas and expression correlates with metastasis and poor survival. To explore its biomarker potential, new antibodies are needed that specifically recognize this antigen in tumors. Here we generated two recombinant antibodies to the Tn antigen, Remab6 as a chimeric human IgG1 antibody and ReBaGs6 as a murine IgM antibody and characterized their specificities using multiple biochemical and biological approaches. Both Remab6 and ReBaGs6 recognize clustered Tn structures, but most importantly do not recognize glycoforms of human IgA1 that contain potential cross-reactive Tn antigen structures. In flow cytometry and immunofluorescence analyses, Remab6 recognizes human cancer cell lines expressing the Tn antigen, but not their Tn-negative counterparts. In immunohistochemistry (IHC), Remab6 stains many human cancers in tissue array format but rarely stains normal tissues and then mostly intracellularly. We used these antibodies to identify several unique Tn-containing glycoproteins in Tn-positive Colo205 cells, indicating their utility for glycoproteomics in future biomarker studies. Thus, recombinant Remab6 and ReBaGs6 are useful for biochemical characterization of cancer cells and IHC of tumors and represent promising tools for Tn biomarker discovery independently of recognition of IgA1.

O-glycan recognition and function in mice and human cancers

Protein glycosylation represents a nearly ubiquitous post-translational modification, and altered glycosylation can result in clinically significant pathological consequences. Here we focus on O-glycosylation in tumor cells of mice and humans. O-glycans are those linked to serine and threonine (Ser/Thr) residues via N-acetylgalactosamine (GalNAc), which are oligosaccharides that occur widely in glycoproteins, such as those expressed on the surfaces and in secretions of all cell types. The structure and expression of O-glycans are dependent on the cell type and disease state of the cells. There is a great interest in O-glycosylation of tumor cells, as they typically express many altered types of O-glycans compared with untransformed cells. Such altered expression of glycans, quantitatively and/or qualitatively on different glycoproteins, is used as circulating tumor biomarkers, such as CA19-9 and CA-125. Other tumor-associated carbohydrate antigens (TACAs), such as the Tn antigen and sialyl-Tn antigen (STn), are truncated O-glycans commonly expressed by carcinomas on multiple glycoproteins; they contribute to tumor development and serve as potential biomarkers for tumor presence and stage, both in immunohistochemistry and in serum diagnostics. Here we discuss O-glycosylation in murine and human cells with a focus on colorectal, breast, and pancreatic cancers, centering on the structure, function and recognition of O-glycans. There are enormous opportunities to exploit our knowledge of O-glycosylation in tumor cells to develop new diagnostics and therapeutics.

Potential of Anti-MUC1 Antibodies as a Targeted Therapy for Gastrointestinal Cancers

Gastrointestinal cancers (GI) account for 26% of cancer incidences globally and 35% of all cancer-related deaths. The main challenge is to target cancer specific antigens. Mucins are heavily O-glycosylated proteins overexpressed in different cancers. The transmembrane glycoprotein MUC1 is the most likeable target for antibodies, owing to its specific overexpression and aberrant glycosylation in many types of cancers. For the past 30 years, MUC1 has remained a possible diagnostic marker and therapeutic target. Despite initiation of numerous clinical trials, a comprehensively effective therapy with clinical benefit is yet to be achieved. However, the interest in MUC1 as a therapeutic target remains unaltered. For all translational studies, it is important to incorporate updated relevant research findings into therapeutic strategies. In this review we present an overview of the antibodies targeting MUC1 in GI cancers, their potential role in immunotherapy (i.e., antibody-drug and radioimmunoconjugates, CAR-T cells), and other novel therapeutic strategies. We also present our perspectives on how the mechanisms of action of different anti-MUC1 antibodies can target specific hallmarks of cancer and therefore be utilized as a combination therapy for better clinical outcomes.

MUC1 antibody-based therapeutics: the promise of cancer immunotherapy

Antibody-based targeted therapies have been able to target cancers with enhanced specificity and high efficacy. In this regard, identifying cancer markers (antigens) that are only present (tumor-specific antigens) or have an increased expression (tumor-associated antigen) on the surface of cancer cells is a crucial step for targeted cancer treatment. Various cancer antigens have already been used for therapeutic and diagnostic purposes. MUC1 is one of the most important tumor markers with high levels of expression in various solid tumors which makes it as a potential target for antibody-based therapies. This review discusses preclinical and clinical results from various platforms based on monoclonal antibodies, nanobodies as well as bispecific antibodies against MUC1. We also highlight unmet challenges that must be overcome to generate more effective cancer immunotherapy strategies.

Natural-based Hydrogels: A Journey from Simple to Smart Networks for Medical Examination

Natural hydrogels, due to their unique biological properties, have been used extensively for various medical and clinical examinations that are performed to investigate the signs of disease. Recently, complex-crosslinking strategies improved the mechanical properties and advanced approaches have resulted in the introduction of naturally derived hydrogels that exhibit high biocompatibility, with shape memory and self-healing characteristics. Moreover, the creation of self-assembled natural hydrogels under physiological conditions has provided the opportunity to engineer fine-tuning properties. To highlight recent studies of natural-based hydrogels and their applications for medical investigation, a critical review was undertaken using published papers from the Science Direct database. This review presents different natural-based hydrogels (natural, natural-synthetic hybrid and complex-crosslinked hydrogels), their historical evolution, and recent studies of medical examination applications. The application of natural-based hydrogels in the design and fabrication of biosensors, catheters and medical electrodes, detection of cancer, targeted delivery of imaging compounds (bioimaging) and fabrication of fluorescent bioprobes is summarised here. Without doubt, in future, more useful and practical concepts will be derived to identify natural-based hydrogels for a wide range of clinical examination applications.

N-Glycoproteins Have a Major Role in MGL Binding to Colorectal Cancer Cell Lines: Associations with Overall Proteome Diversity

Colorectal cancer (CRC) is the second-leading cause of cancer death worldwide due in part to a high proportion of patients diagnosed at advanced stages of the disease. For this reason, many efforts have been made towards new approaches for early detection and prognosis. Cancer-associated aberrant glycosylation, especially the Tn and STn antigens, can be detected using the macrophage galactose-type C-type lectin (MGL/CLEC10A/CD301), which has been shown to be a promising tool for CRC prognosis. We had recently identified the major MGL-binding glycoproteins in two high-MGL-binding CRC cells lines, HCT116 and HT29. However, we failed to detect the presence of O-linked Tn and STn glycans on most CRC glycoproteins recognized by MGL. We therefore investigated here the impact of N-linked and O-linked glycans carried by these proteins for the binding to MGL. In addition, we performed quantitative proteomics to study the major differences in proteins involved in glycosylation in these cells. Our results showed that N-glycans have a significant, previously underestimated, importance in MGL binding to CRC cell lines. Finally, we highlighted both common and cell-specific processes associated with a high-MGL-binding phenotype, such as differential levels of enzymes involved in protein glycosylation, and a transcriptional factor (CDX-2) involved in their regulation.

Evaluation of the Anti-Tumor Activity of the Humanized Monoclonal Antibody NEO-201 in Preclinical Models of Ovarian Cancer

Purpose: Despite high initial response rates with cytoreductive surgery, conventional chemotherapy and the incorporation of biologic agents, ovarian cancer patients often relapse and die from their disease. New approaches are needed to improve patient outcomes. This study was designed to evaluate the antitumor activity of NEO-201 monoclonal antibody (mAb) in preclinical models of ovarian cancer where the NEO-201 target is highly expressed.

Experimental Design: Functional analysis of NEO-201 against tumor cell lines was performed by antibody-dependent cellular cytotoxicity (ADCC) assays. Binding of NEO-201 to tumor tissues and cell lines were determined by immunohistochemistry (IHC) and flow cytometry, respectively. Further characterization of the antigen recognized by NEO-201 was performed by mass spectrometry. Ovarian cancer models were used to evaluate the anti-tumor activity of NEO-201 in vivo. NEO-201 at a concentration of 250 g/mouse was injected intraperitoneally (IP) on days 1, 4, and 8. Human PBMCs were injected IP simultaneously as effector cells.

Results: Both IHC and flow cytometry revealed that NEO-201 binds prominently to the colon, pancreatic, and mucinous ovarian cancer tissues and cell lines. Immunoprecipitation of the antigen recognized by NEO-201 was performed in human ovarian, colon, and pancreatic cancer cell lines. From these screening, carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and CEACAM6 were identified as the most likely targets of NEO-201. Our results confirmed that NEO-201 binds different types of cancers; the binding is highly selective for the tumor cells without cross reactivity with the surrounding healthy tissue. Functional analysis revealed that NEO-201 mediates ADCC killing against human ovarian and colorectal carcinoma cell lines in vitro. In addition, NEO-201 inhibited tumor growth in the presence of activated human PBMCs in orthotopic mouse models of both primary and metastatic ovarian cancer. Importantly, NEO-201 prolonged survival of tumor-bearing mice.

Conclusions: These data suggested that NEO-201 has an antitumor activity against tumor cells expressing its antigen. Targeting an antigen expressed in tumors, but not in normal tissues, allows patient selection for optimal treatment. These findings strongly indicate that NEO-201 warrants clinical testing as both a novel therapeutic and diagnostic agent for treatment of ovarian carcinomas. A first in human clinical trial evaluating NEO-201 in adults with chemo-resistant solid tumors is ongoing at the NIH clinical Center.

Reduced DAXX Expression Is Associated with Reduced CD24 Expression in Colorectal Cancer

The presence of an activating mutation of the Wnt/β-catenin signaling pathway is found in ~90% of colorectal cancer (CRC) cases. Death domain-associated protein (DAXX), a nuclear protein, interacts with β-catenin in CRC cells. We investigated DAXX expression in 106 matched sample pairs of CRC and adjacent normal tissue by Western blotting. This study evaluated DAXX expression and its clinical implications in CRC. The results revealed that DAXX expression was significantly lower in the patients with the positive serum carcinoembryonic antigen (CEA) screening results compared to the patients with negative CEA screening levels (p < 0.001). It has been reported that CD24 is a Wnt target in CRC cells. Here, we further revealed that DAXX expression was significantly correlated with CD24 expression (rho = 0.360, p < 0.001) in 106 patients. Consistent with this, in the CEA-positive subgroup, of which the carcinomas expressed DAXX at low levels, they were significantly correlated with CD24 expression (rho = 0.461, p < 0.005). Therefore, reduced DAXX expression is associated with reduced CD24 expression in CRC. Notably, in the Hct116 cells, DAXX knockdown using short-hairpin RNA against DAXX (shDAXX) not only caused significant cell proliferation, but also promoted metastasis. The DAXX-knockdown cells also demonstrated significantly decreased CD24 expression, however the intracellular localization of CD24 did not change. Thus, DAXX might be considered as a potential regulator of CD24 or β-catenin expression, which might be correlated with proliferative and metastatic potential of CRC.

Lectin nanoparticle assays for detecting breast cancer-associated glycovariants of cancer antigen 15-3 (CA15-3) in human plasma

Cancer antigen 15–3 (CA15-3) is widely utilized for monitoring metastatic breast cancer (BC). However, its utility for early detection of breast cancer is severely limited due to poor clinical sensitivity and specificity. The glycosylation of CA15-3 is known to be affected by BC, and therefore it might offer a way to construct CA15-3 glycovariant assays with improved cancer specificity. To this end, we performed lectin-based glycoprofiling of BC-associated CA15-3. CA15-3 expressed by a BC cell line was immobilized on microtitration wells using an anti-CA15-3 antibody. The glycosylation of the immobilized CA15-3 was then detected by using lectins coated onto europium (III)-doped nanoparticles (Eu⁺³-NPs) and measuring the time-resolved fluorescence of Eu. Out of multiple lectin-Eu⁺³-NP preparations, wheat germ agglutinin (WGA) and macrophage galactose-type lectin (MGL) -Eu³⁺-NPs bound to the BC cell line-dericed CA15-3 glycovariants (CA15-3^Lectin). To evaluate the clinical performance of these two lectin-based assays, plasma samples from metastatic BC patients (n = 53) and healthy age-matched women (n = 20).Plasma CA15-3^Lectin measurements better distinguished metastatic BC patients from healthy controls than the conventional CA15-3 immunoassay. At 90% specificity, the clinical sensitivity of the assays was 66.0, 67.9 and 81.1% for the conventional CA15-3, CA15-3^MGL and CA15-3^WGA assays, respectively. Baseline CA15-3^MGL and CA15-3^WGA were correlated to conventional baseline CA15-3 levels (r = 0.68, p<0.001, r = 0.90, p>0.001, respectively). However, very low baseline CA15-3^MGL levels ≤ 5 U/mL were common in this metastatic breast cancer patient population.In conclusion, the new CA15-3^Lectin concept could considerably improve the clinical sensitivity of BC detection compared to the conventional CA15-3 immunoassays and should be validated further on a larger series of subjects with different cancer subtypes and stages.

Investigation on core-fucosylated prostate-specific antigen as a refined biomarker for differentiation of benign prostate hyperplasia and prostate cancer of different aggressiveness

Prostate cancer represents a major cause of cancer death in men worldwide. Novel non-invasive methods are still required for differentiation of non-aggressive from aggressive tumors. Recently, changes in prostate-specific antigen glycosylation pattern, such as core-fucosylation, have been described in prostate cancer. The objective of this study was to evaluate whether the core-fucosylation determinant of serum prostate-specific antigen may serve as refined marker for differentiation between benign prostate hyperplasia and prostate cancer or identification of aggressive prostate cancer. A previously developed liquid chromatography-mass spectrometry/mass spectrometry-based strategy was used for multiplex analysis of core-fucosylated prostate-specific antigen (fuc-PSA) and total prostate-specific antigen levels in sera from 50 benign prostate hyperplasia and 100 prostate cancer patients of different aggressiveness (Gleason scores, 5-10) covering the critical gray area (2-10 ng/mL). For identification of aggressive prostate cancer, the ratio of fuc-PSA to total prostate-specific antigen (%-fuc-PSA) yielded a 5%-8% increase in the area under the curve (0.60) compared to the currently used total prostate-specific antigen (area under the curve = 0.52) and %-free prostate-specific antigen (area under the curve = 0.55) tests. However, our data showed that aggressive prostate cancer (Gleason score > 6) and non-aggressive prostate cancer (Gleason score ≤ 6) could not significantly (p-value = 0.08) be differentiated by usage of %-fuc-PSA. In addition, both non-standardized fuc-PSA and standardized %-fuc-PSA had no diagnostic value for differentiation of benign prostate hyperplasia from prostate cancer. The %-fuc-PSA serum levels could not improve the differentiation of non-aggressive and aggressive prostate cancer compared to conventional diagnostic prostate cancer markers. Still, it is unclear whether these limitations come from the biomarker, the used patient cohort, or the imprecision of the applied method itself. Therefore, %-fuc-PSA should be further investigated, especially by more precise methods whether it could be clinically used in prostate cancer diagnosis.

Differential expression of mucin 1 and mucin 2 in colorectal cancer

AIM

To determine tissue expression (mRNA, protein) of two types of mucins [mucin 1 (MUC1) and mucin 2 (MUC2)] in patients with colorectal cancer (CRC).

METHODS

Expression of membrane-bound mucin (MUC1) and secretory mucin (MUC2) in CRC (mRNA, protein) were analyzed in tissue material including fragments of tumors obtained from CRC patients (n = 34), and fragments of normal colorectal tissue from the same patients (control). The analysis was conducted using real-time quantitative polymerase chain reaction (RT-qPCR) (transcripts), immunohistochemistry (IHC) (apomucins), and the modern approach for morphometric analysis of IHC reaction (HSV filter software). Results on tissue expression of both mucins (mRNA, protein) were compared to histological alterations in colorectal cancer samples and correlated with selected clinical data in the patients. The statistical analysis was conducted using Statistica PL v. 12.0 software.

RESULTS

Significantly higher expression of the MUC1 mRNA in the CRC, compared with the control and the borderline correlation of mRNA expression with MUC1 protein levels in colorectal samples was observed. The expression of apomucins concerned cell membranes (MUC1) and cytoplasm (MUC2) and occurred both in control tissues and in most cancerous samples. There were no significant relationships between MUC1 (mRNA, protein) and the clinicopathological data of patients. MUC2 protein expression was significantly lower as compared to the control, while MUC2 mRNA expression was comparable in both groups. The MUC1/MUC2 ratio was significantly higher in CRC tissues than in the control. The higher expression of MUC2 was a feature of mucinous CRC subtypes, and characterized higher histological stage of tumors. Negative correlations have been obtained between MUC2 and the Ki-67 antigen, as well as between MUC2 and p53 protein expressions in CRC.

CONCLUSION

A combination of tissue overexpression of MUC1, reduced MUC2 expression, and high ratio of MUC1/MUC2 is a factor of poor prognosis in CRC patients. MUC2 tissue expression allows to differentiate mucinous and nonmucinous CRC subtypes.

Unusual N-type glycosylation of salivary prolactin-inducible protein (PIP): multiple LewisY epitopes generate highly-fucosylated glycan structures

Prolactin-inducible protein (PIP) is a glycoprotein found in body secretions from exocrine glands like saliva and seminal plasma. Important biological functions of PIP concentrations have been demonstrated, e.g. in tumor diagnosis and progression. PIP quantity has been also found useful to determine the success of chemotherapy of mammary carcinoma. Here, we present the analysis of the N-glycosylation of PIP isolated from different sources by LC-MS(/MS) and ¹H-NMR. We found a very uncommon N-type glycosylation of PIP in healthy individuals from both, seminal fluid and saliva. PIP carries unusual highly fucosylated N-linked glycans with multiple Lewis^y (Le^y) epitopes on bi-, tri- and tetraantennary structures resulting in up to nine fucosyl residues on a tetraantennary glycan. In most organs, Le^y epitopes are not present on N-glycans except in case of a tumor when it is highly up-regulated and important for prognosis. Here, for the first time on a specific glycoprotein Le^y antigens are unambiguously characterized on an N-type glycan by NMR spectroscopy. So far, for specific glycoproteins Le^y epitopes had only been reported on O-glycans. Furthermore, a correlation between a nonsynonymous single nucleotide polymorphism (SNP) and glycosylation pattern was detected: individuals heterozygous for the SNP causing the amino acid exchange ⁵¹Gln to ⁵¹His have glycan structures with a higher degree of sialylation compared to individuals lacking the SNP.

Diagnostic utility of glycosyltransferase mRNA expression in gastric cancer

OBJECTIVE/BACKGROUND

Posttranslational modification of proteins, including glycosylation, is known to differ between normal and tumor cells. Altered glycosyltransferase levels have been observed in tumor tissues and their role in tumor metastasis and invasion has been implicated. In this study the role of altered glycosyltransferase messenger RNA (mRNA) levels in serum of gastric cancer patients as early markers of gastric cancer was evaluated.

METHODS

In this case control study the expression profile of ppGalNAc-T6, GlcNAcT-V, ST3Gal I, ST3 Gal IV, and ST6GalNAc-I in normal healthy control and gastric cancer patients was compared. Serum was isolated from blood samples of gastric cancer patients (n = 200) and controls (n = 200). Following RNA extraction, reverse transcription was carried out and transcript levels of glycosyltransferases were determined using real-time quantitative polymerase chain reaction and normalized against glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression. The amount of target gene, normalized to an endogenous reference gene relative to calibrator was calculated by using ΔΔCT method. Transcript levels in the serum samples of gastric cancer patients were compared with those of controls; also the same was correlated within sex and different stages of disease.

RESULTS

The mRNA expression of ppGalNAc-T6 and ST6GalNAc-I was significantly higher in serum samples of gastric cancer patients on comparison with controls (p = .008), however, there was no significant difference in mRNA expression of GlcNAcT-V, ST3Gal I, and ST3 Gal IV in serum samples of gastric cancer patients and controls (p = .097). In addition, no significant association of mRNA expression of these glycosyltransferases was found within sex and stages in this study.

CONCLUSION

This study revealed the potential of ppGalNAc-T6 and ST6GalNAc-I mRNA transcript levels in serum as markers of gastric cancer. Further studies on the wider range of glycosyltransferases in various cancers are needed to establish signature mRNA batteries as minimally invasive markers of gastric cancer.

Serum sialylation changes in cancer

Cancer is a major cause of death in both developing and developed countries. Early detection and efficient therapy can greatly enhance survival. Aberrant glycosylation has been recognized to be one of the hallmarks of cancer as glycans participate in many cancer-associated events. Cancer-associated glycosylation changes often involve sialic acids which play important roles in cell-cell interaction, recognition and immunological response. This review aims at giving a comprehensive overview of the literature on changes of sialylation in serum of cancer patients. Furthermore, the methods available to measure serum and plasma sialic acids as well as possible underlying biochemical mechanisms involved in the serum sialylation changes are surveyed. In general, total serum sialylation levels appear to be increased with various malignancies and show a potential for clinical applications, especially for disease monitoring and prognosis. In addition to overall sialic acid levels and the amount of sialic acid per total protein, glycoprofiling of specific cancer-associated glycoproteins, acute phase proteins and immunoglobulins in serum as well as the measurements of sialylation-related enzymes such as sialidases and sialyltransferases have been reported for early detection of cancer, assessing cancer progression and improving prognosis of cancer patients. Moreover, sialic-acid containing glycan antigens such as CA19-9, sialyl Lewis X and sialyl Tn on serum proteins have also displayed their value in cancer diagnosis and management whereby increased levels of these factors positively correlated with metastasis or poor prognosis.

Gene and microRNA modulation upon trabectedin treatment in a human intrahepatic cholangiocarcinoma paired patient derived xenograft and cell line

Intrahepatic cholangiocarcinoma (ICC) is an aggressive and lethal malignancy with limited therapeutic options. Trabectedin has a high antitumor activity in preclinical models of biliary tract carcinoma (BTC), being a promising alternative treatment. Here, we studied the effect of trabectedin at transcriptomic level on an ICC patient derived xenograft (PDX) and on the derived cell line, MT-CHC01. Further, putative targets of trabectedin were explored in the in vitro model. In vitro, trabectedin inhibited genes involved in protein modification, neurogenesis, migration, and motility; it induced the expression of genes involved in keratinization, tissues development, and apoptotic processes. In the PDX model, trabectedin affected ECM-receptor interaction, focal adhesion, complement and coagulation cascades, Hedgehog, MAPK, EGFR signaling via PIP3 pathway, and apoptosis. Among down-regulated genes, we selected SYK and LGALS1; their silencing caused a significantly reduction of migration, but did not affect proliferation in in vitro models. In MT-CHC01 cells, 24 microRNAs were deregulated upon drug treatment, while only 5 microRNAs were perturbed by trabectedin in PDX. The target prediction analysis showed that SYK and LGALS1 are putative targets of up-regulated microRNAs. In conclusion, we described that trabectedin affected genes and microRNAs involved in tumor progression and metastatic processes, reflecting data previously obtained at macroscopically level; in particular, we identified SYK and LGALS1 as new putative targets of trabectedin.

Glycan analysis of colorectal cancer samples reveals stage-dependent changes in CEA glycosylation patterns

Background

Carcinoembryonic antigen (CEA) is a glycoprotein associated with colorectal cancer (CRC). While the functions of its gene and protein have been fully characterized, its post-translational modifications in the context of CRC development remain undefined.

Methods

To show the correlation between the different stages of CRC development and changes in the glycosylation patterns of CEA, we analyzed CEA in tumor tissues (CEA-T) and paired tumor-adjacent normal tissues (CEA-A) from 53 colorectal cancer patients using a high-density lectin microarray containing 56 plant lectins.

Results

We detected higher expression levels of fucose, mannose and Thomsen–Friedenreich antigen, and lower expression levels of N-acetylgalactosamine, N-acetylglucosamine, galactose, branched and bisecting N-glycans on CEA in the tumor tissues relative to the tumor-adjacent normal tissues. Furthermore, a combinatorial assessment of 9 lectins is sufficient to distinguish CRC tumor tissues from tumor-adjacent normal tissues with 83% sensitivity and ~ 90% specificity. Moreover, the levels of N-acetylgalactosamine, mannose, galactose, N-acetylglucosamine on CEA showed a downward trend after first experiencing an increase at Stage II with the stages of CRC.

Conclusions

Our insights into the changing CEA glycosylation patterns and their role in the development of CRC highlight the importance of glycan variants on CEA for early clinical detection and staging of CRC.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9182-4) contains supplementary material, which is available to authorized users.

Synergistic interaction between galectin-3 and carcinoembryonic antigen promotes colorectal cancer metastasis

In this study, we investigated the role of galectin-3 and carcinoembryonic antigen (CEA) in metastasis and survival of colorectal cancer (CRC) patients. CEA interacted with galectin-3 at the cell surface and cytoplasm of Caco2 and DLD1 CRC cells. Knocking down galectin-3 did not affect CEA expression in CRC cells. However, there was a dose-dependent increase in CRC cell migration upon addition of small amounts of exogenous CEA (≤1ng/ml). Galectin-3 knockdown blocked induction of CRC cell migration by CEA, suggesting interaction between galectin-3 and CEA was necessary for CRC cell migration. Exogenous CEA and galectin-3 synergistically promoted migration of galectin-3 knockdown DLD1 cells. Immunohistochemical analysis showed that CEA co-localized with galectin-3 in CRC patient tissues. In additon, advanced stage CRC patients had higher serum galectin-3 and CEA levels than early stage CRC patients. High serum CEA and galectin-3 levels correlated with advanced N stage and poor survival in CRC patients. These findings suggest interaction between galectin-3 and CEA promotes CRC migration and metastasis, and correlates with poor survival of CRC patients. Thus combinatorial therapy targeting galectin-3 and CEA may improve outcomes for advanced stage CRC patients.

The Roles of Carcinoembryonic Antigen in Liver Metastasis and Therapeutic Approaches

Metastasis is a highly complicated and sequential process in which primary cancer spreads to secondary organic sites. Liver is a well-known metastatic organ from colorectal cancer. Carcinoembryonic antigen (CEA) is expressed in most gastrointestinal, breast, and lung cancer cells. Overexpression of CEA is closely associated with liver metastasis, which is the main cause of death from colorectal cancer. CEA is widely used as a diagnostic and prognostic tumor marker in cancer patients. It affects many steps of liver metastasis from colorectal cancer cells. CEA inhibits circulating cancer cell death. CEA also binds to heterogeneous nuclear RNA binding protein M4 (hnRNP M4), a Kupffer cell receptor protein, and activates Kupffer cells to secrete various cytokines that change the microenvironments for the survival of colorectal cancer cells in the liver. CEA also activates cell adhesion-related molecules. The close correlation between CEA and cancer has spurred the exploration of many CEA-targeted approaches as anticancer therapeutics. Understanding the detailed functions and mechanisms of CEA in liver metastasis will provide great opportunities for the improvement of anticancer approaches against colorectal cancers. In this report, the roles of CEA in liver metastasis and CEA-targeting anticancer modalities are reviewed.

Starch-enriched diet modulates the glucidic profile in the rat colonic mucosa

PURPOSE

The protective function of the intestinal mucosa largely depends on carbohydrate moieties that as a part of glycoproteins and glycolipids form the epithelial glycocalyx or are secreted as mucins. Modifications of their expression can be induced by an altered intestinal microenvironment and have been associated with inflammatory disorders and colorectal cancer. Given the influence of dietary factors on the gut ecosystem, here we have investigated whether a long term feeding on a starch-rich diet can modulate the glucidic profile in the colonic mucosa of rats.

METHODS

Animals were divided into two groups and maintained for 9 months at different diets: one group was fed a standard diet, the second was fed a starch-enriched diet. Samples of colonic mucosa, divided in proximal and distal portions, were processed for microscopic analysis. Conventional stainings and lectin histochemistry were applied to identify acidic glycoconjugates and specific sugar residues in oligosaccharide chains, respectively. Some lectins were applied on adjacent sections after sialidase/fucosidase digestion, deacetylation, and oxidation to characterize either terminal dimers or sialic acid acetylation.

RESULTS

An increase in sulfomucins was found to be associated with the starch-enriched diet that affected also the expression of several sugar residues as well as fucosylated and sialylated sequences in both proximal and distal colon.

CONCLUSIONS

Although the mechanisms leading to such a modulation are at present unknown, either an altered intestinal microbiota or a dysregulation of glycosylation patterns might be responsible for the types and distribution of changes in the glucidic profile here observed.

Tumor sialylation impedes T cell mediated anti-tumor responses while promoting tumor associated-regulatory T cells

The increased presence of sialylated glycans on the tumor surface has been linked to poor prognosis, yet the effects on tumor-specific T cell immunity are hardly studied. We here show that hypersialylation of B16 melanoma substantially influences tumor growth by preventing the formation of effector T cells and facilitating the presence of high regulatory T cell (Treg) frequencies. Knock-down of the sialic acid transporter created "sialic acid low" tumors, that grew slower in-vivo than hypersialylated tumors, altered the Treg/Teffector balance, favoring immunological tumor control. The enhanced effector T cell response in developing "sialic acid low" tumors was preceded by and dependent on an increased influx and activity of Natural Killer (NK) cells. Thus, tumor hypersialylation orchestrates immune escape at the level of NK and Teff/Treg balance within the tumor microenvironment, herewith dampening tumor-specific T cell control. Reducing sialylation provides a therapeutic option to render tumors permissive to immune attack.

MUC1-ARF-A Novel MUC1 Protein That Resides in the Nucleus and Is Expressed by Alternate Reading Frame Translation of MUC1 mRNA

Translation of mRNA in alternate reading frames (ARF) is a naturally occurring process heretofore underappreciated as a generator of protein diversity. The MUC1 gene encodes MUC1-TM, a signal-transducing trans-membrane protein highly expressed in human malignancies. Here we show that an AUG codon downstream to the MUC1-TM initiation codon initiates an alternate reading frame thereby generating a novel protein, MUC1-ARF. MUC1-ARF, like its MUC1-TM 'parent’ protein, contains a tandem repeat (VNTR) domain. However, the amino acid sequence of the MUC1-ARF tandem repeat as well as N- and C- sequences flanking it differ entirely from those of MUC1-TM. In vitro protein synthesis assays and extensive immunohistochemical as well as western blot analyses with MUC1-ARF specific monoclonal antibodies confirmed MUC1-ARF expression. Rather than being expressed at the cell membrane like MUC1-TM, immunostaining showed that MUC1-ARF protein localizes mainly in the nucleus: Immunohistochemical analyses of MUC1-expressing tissues demonstrated MUC1-ARF expression in the nuclei of secretory luminal epithelial cells. MUC1-ARF expression varies in different malignancies. While the malignant epithelial cells of pancreatic cancer show limited expression, in breast cancer tissue MUC1-ARF demonstrates strong nuclear expression. Proinflammatory cytokines upregulate expression of MUC1-ARF protein and co-immunoprecipitation analyses demonstrate association of MUC1-ARF with SH3 domain-containing proteins. Mass spectrometry performed on proteins coprecipitating with MUC1-ARF demonstrated Glucose-6-phosphate 1-dehydrogenase (G6PD) and Dynamin 2 (DNM2). These studies not only reveal that the MUC1 gene generates a previously unidentified MUC1-ARF protein, they also show that just like its ‘parent’ MUC1-TM protein, MUC1-ARF is apparently linked to signaling and malignancy, yet a definitive link to these processes and the roles it plays awaits a precise identification of its molecular functions. Comprising at least 524 amino acids, MUC1-ARF is, furthermore, the longest ARF protein heretofore described.

Tumor-associated antigens: Tn antigen, sTn antigen, and T antigen

Glycosylation is one of the major posttranslational modifications of proteins. N-glycosylation (Asn-linked) and O-glycosylation (Ser/Thr-linked) are the two main forms. Abnormal O-glycosylation is frequently observed on the surface of tumor cells, and is associated with an adverse outcome and poor prognosis in patients with cancer. O-glycans (Tn, sTn, and T antigen) can be synthesized in the Golgi apparatus with the aid of several glycosyltransferases (such as T-synthase and ST6GalNAc-I) in a suitable environment. The unique molecular chaperone of T-synthase is Cosmc, which helps T-synthase to fold correctly in the endoplasmic reticulum. Dysregulation of these glycosyltransferases, molecular chaperones, or the environment is involved in the dysregulation of O-glycans. Tn, sTn, and T antigen neo- or over-expression occurs in many types of cancer including gastric, colon, breast, lung, esophageal, prostate, and endometrial cancer. This review discusses the major synthetic pathway of O-glycans and the mechanism by which Tn, sTn, and T antigens promote tumor metastasis.

A Nanoparticle-Lectin Immunoassay Improves Discrimination of Serum CA125 from Malignant and Benign Sources

BACKGROUND

Measurement of serum cancer antigen 125 (CA125) is the standard approach for epithelial ovarian cancer (EOC) diagnostics and follow-up. However, the clinical specificity is not optimal because increased values are also detected in healthy controls and in benign diseases. CA125 is known to be differentially glycosylated in EOC, potentially offering a way to construct CA125 assays with improved cancer specificity. Our goal was to identify carbohydrate-reactive lectins for discriminating between CA125 originating from EOC and noncancerous sources.

METHODS

CA125 from the OVCAR-3 cancer cell line, placental homogenate, and ascites fluid from patients with cirrhosis were captured on anti-CA125 antibody immobilized on microtitration wells. A panel of lectins, each coated onto fluorescent europium-chelate-doped 97-nm nanoparticles (Eu(+3)-NPs), was tested for detection of the immobilized CA125. Serum samples from high-grade serous EOC or patients with endometriosis and healthy controls were analyzed.

RESULTS

By using macrophage galactose-type lectin (MGL)-coated Eu(+3)-NPs, an analytically sensitive CA125 assay (CA125(MGL)) was achieved that specifically recognized the CA125 isoform produced by EOC, whereas the recognition of CA125 from nonmalignant conditions was reduced. Serum CA125(MGL) measurement better discriminated patients with EOC from endometriosis compared to conventional immunoassay. The discrimination was particularly improved for marginally increased CA125 values and for earlier detection of EOC progression.

CONCLUSIONS

The new CA125(MGL) assay concept could help reduce the false-positive rates of conventional CA125 immunoassays. The improved analytical specificity of this test approach is dependent on a discriminating lectin immobilized in large numbers on Eu(+3)-NPs, providing both an avidity effect and signal amplification.

Multiplex determination of serological signatures in the sera of colorectal cancer patients using hydrogel biochips

Colorectal cancer (CRC) is the third most common malignancy in industrialized countries. Despite the advances in diagnostics and development of new drugs, the 5-year survival remains only 60-65%. Our approach to early diagnostics of CRC is based on the determination of serological signatures with an array of hemispherical hydrogel cells containing immobilized proteins and oligosaccharides (glycochip). The compounds immobilized on the glycochip include tumor-associated glycans (SiaTn, Tn, TF, Le(C) , Le(Y) , SiaLe(A) , and Manβ1-4GlcNAcβ) and antibodies against human immunoglobulins IgG, IgA, and IgM. The glycochip detects antibodies against tumor-associated glycans in patients' sera. The simultaneous measurement of the levels of immunoglobulins enhances the diagnostic impact of the signatures. In this work, we found previously unreported increase in antibodies against oligosaccharide Manβ1-4GlcNAcβ in patients with CRC. In parallel with these experiments, we determined the levels of oncomarkers carcinoembryonic antigen (CEA), cancer antigen (CA) 19-9, CA 125, CA 15-3, human chorionic gonadotropin (HCG), and alpha-fetoprotein (AFP) using another gel-based biochip with immobilized antibodies (oncochip) developed earlier in our laboratory. In total, 69 samples from healthy donors, 33 from patients with colorectal carcinoma, and 27 from patients with inflammatory bowel diseases were studied. The use of combined signatures of antiglycan antibodies and oncomarkers provides much better predictive value than the conventional measurement of oncomarkers CEA and CA 19-9. Positive predictive value of CRC diagnoses using together glycochip and oncochip reached 95% with the sensitivity and specificity 88% and 98%, respectively. Thus, the combination of antibody profiling with detection of conventional oncomarkers proved to be a promising tool in diagnostics of CRC.

A Bitter Sweet Symphony: Immune Responses to Altered O-glycan Epitopes in Cancer

The appearance of aberrant glycans on the tumor cell surface is one of the emerging hallmarks of cancer. Glycosylation is an important post-translation modification of proteins and lipids and is strongly affected by oncogenesis. Tumor-associated glycans have been extensively characterized regarding their composition and tumor-type specific expression patterns. Nevertheless whether and how tumor-associated glycans contribute to the observed immunomodulatory actions by tumors has not been extensively studied. Here, we provide a detailed overview of the current knowledge on how tumor-associated O-glycans affect the anti-tumor immune response, thereby focusing on truncated O-glycans present on epithelial tumors and mucins. These tumor-associated O-glycans and mucins bind a variety of lectin receptors on immune cells to facilitate the subsequently induction of tolerogenic immune responses. We, therefore, postulate that tumor-associated glycans not only support tumor growth, but also actively contribute to immune evasion.