Deficiency of GMDS leads to escape from NK cell-mediated tumor surveillance through modulation of TRAIL signaling

Development of a FUT8 Inhibitor with Cellular Inhibitory Properties

Core fucosylation is catalyzed by α-1,6-fucosyltransferase (FUT8), which fucosylates the innermost GlcNAc of N-glycans. Given the association of FUT8 with various diseases, including cancer, selective FUT8 inhibitors applicable to in vivo or cell-based systems are highly sought-after. Herein, we report the discovery of a compound that selectively inhibits FUT8 in cell-based assays. High-throughput screening revealed a FUT8-inhibiting pharmacophore, and further structural optimization yielded an inhibitor with a KD value of 49 nM. Notably, this binding occurs only in the presence of GDP (a product of the enzymatic reaction catalyzed by FUT8). Mechanistic studies suggested that this inhibitor generates a highly reactive naphthoquinone methide derivative at the binding site in FUT8, which subsequently reacts with FUT8. Furthermore, prodrug derivatization of this inhibitor improved its stability, enabling suppression of core fucose expression and subsequent EGFR and T-cell signaling in cell-based assays, paving the way for the development of drugs targeting core fucosylation.

FUCA1: An Underexplored p53 Target Gene Linking Glycosylation and Cancer Progression

Cancer is a difficult-to-cure disease with high worldwide incidence and mortality, in large part due to drug resistance and disease relapse. Glycosylation, which is a common modification of cellular biomolecules, was discovered decades ago and has been of interest in cancer research due to its ability to influence cellular function and to promote carcinogenesis. A variety of glycosylation types and structures regulate the function of biomolecules and are potential targets for investigating and treating cancer. The link between glycosylation and carcinogenesis has been more recently revealed by the role of p53 in energy metabolism, including the p53 target gene alpha-L-fucosidase 1 (FUCA1), which plays an essential role in fucosylation. In this review, we summarize roles of glycan structures and glycosylation-related enzymes to cancer development. The interplay between glycosylation and tumor microenvironmental factors is also discussed, together with involvement of glycosylation in well-characterized cancer-promoting mechanisms, such as the epidermal growth factor receptor (EGFR), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and p53-mediated pathways. Glycan structures also modulate cell-matrix interactions, cell-cell adhesion as well as cell migration and settlement, dysfunction of which can contribute to cancer. Thus, further investigation of the mechanistic relationships among glycosylation, related enzymes and cancer progression may provide insights into potential novel cancer treatments.

Involvement of tumor immune microenvironment metabolic reprogramming in colorectal cancer progression, immune escape, and response to immunotherapy

Metabolic reprogramming is a k`ey hallmark of tumors, developed in response to hypoxia and nutrient deficiency during tumor progression. In both cancer and immune cells, there is a metabolic shift from oxidative phosphorylation (OXPHOS) to aerobic glycolysis, also known as the Warburg effect, which then leads to lactate acidification, increased lipid synthesis, and glutaminolysis. This reprogramming facilitates tumor immune evasion and, within the tumor microenvironment (TME), cancer and immune cells collaborate to create a suppressive tumor immune microenvironment (TIME). The growing interest in the metabolic reprogramming of the TME, particularly its significance in colorectal cancer (CRC)-one of the most prevalent cancers-has prompted us to explore this topic. CRC exhibits abnormal glycolysis, glutaminolysis, and increased lipid synthesis. Acidosis in CRC cells hampers the activity of anti-tumor immune cells and inhibits the phagocytosis of tumor-associated macrophages (TAMs), while nutrient deficiency promotes the development of regulatory T cells (Tregs) and M2-like macrophages. In CRC cells, activation of G-protein coupled receptor 81 (GPR81) signaling leads to overexpression of programmed death-ligand 1 (PD-L1) and reduces the antigen presentation capability of dendritic cells. Moreover, the genetic and epigenetic cell phenotype, along with the microbiota, significantly influence CRC metabolic reprogramming. Activating RAS mutations and overexpression of epidermal growth factor receptor (EGFR) occur in approximately 50% and 80% of patients, respectively, stimulating glycolysis and increasing levels of hypoxia-inducible factor 1 alpha (HIF-1α) and MYC proteins. Certain bacteria produce short-chain fatty acids (SCFAs), which activate CD8+ cells and genes involved in antigen processing and presentation, while other mechanisms support pro-tumor activities. The use of immune checkpoint inhibitors (ICIs) in selected CRC patients has shown promise, and the combination of these with drugs that inhibit aerobic glycolysis is currently being intensively researched to enhance the efficacy of immunotherapy.

Highly accurate carbohydrate-binding site prediction with DeepGlycanSite

As the most abundant organic substances in nature, carbohydrates are essential for life. Understanding how carbohydrates regulate proteins in the physiological and pathological processes presents opportunities to address crucial biological problems and develop new therapeutics. However, the diversity and complexity of carbohydrates pose a challenge in experimentally identifying the sites where carbohydrates bind to and act on proteins. Here, we introduce a deep learning model, DeepGlycanSite, capable of accurately predicting carbohydrate-binding sites on a given protein structure. Incorporating geometric and evolutionary features of proteins into a deep equivariant graph neural network with the transformer architecture, DeepGlycanSite remarkably outperforms previous state-of-the-art methods and effectively predicts binding sites for diverse carbohydrates. Integrating with a mutagenesis study, DeepGlycanSite reveals the guanosine-5'-diphosphate-sugar-recognition site of an important G-protein coupled receptor. These findings demonstrate DeepGlycanSite is invaluable for carbohydrate-binding site prediction and could provide insights into molecular mechanisms underlying carbohydrate-regulation of therapeutically important proteins.

Core Fucosylation Mediated by the FucT-8 Enzyme Affects TRAIL-Induced Apoptosis and Sensitivity to Chemotherapy in Human SW480 and SW620 Colorectal Cancer Cells

Epithelial cells can undergo apoptosis by manipulating the balance between pro-survival and apoptotic signals. In this work, we show that TRAIL-induced apoptosis can be differentially regulated by the expression of α(1,6)fucosyltransferase (FucT-8), the only enzyme in mammals that transfers the α(1,6)fucose residue to the pentasaccharide core of complex N-glycans. Specifically, in the cellular model of colorectal cancer (CRC) progression formed using the human syngeneic lines SW480 and SW620, knockdown of the FucT-8-encoding FUT8 gene significantly enhanced TRAIL-induced apoptosis in SW480 cells. However, FUT8 repression did not affect SW620 cells, which suggests that core fucosylation differentiates TRAIL-sensitive premetastatic SW480 cells from TRAIL-resistant metastatic SW620 cells. In this regard, we provide evidence that phosphorylation of ERK1/2 kinases can dynamically regulate TRAIL-dependent apoptosis and that core fucosylation can control the ERK/MAPK pro-survival pathway in which SW480 and SW620 cells participate. Moreover, the depletion of core fucosylation sensitises primary tumour SW480 cells to the combination of TRAIL and low doses of 5-FU, oxaliplatin, irinotecan, or mitomycin C. In contrast, a combination of TRAIL and oxaliplatin, irinotecan, or bevacizumab reinforces resistance of FUT8-knockdown metastatic SW620 cells to apoptosis. Consequently, FucT-8 could be a plausible target for increasing apoptosis and drug response in early CRC.

Galectin-9 in Gastroenterological Cancer

Immunochemotherapy has become popular in recent years. The detailed mechanisms of cancer immunity are being elucidated, and new developments are expected in the future. Apoptosis allows tissues to maintain their form, quantity, and function by eliminating excess or abnormal cells. When apoptosis is inhibited, the balance between cell division and death is disrupted and tissue homeostasis is impaired. This leads to dysfunction and the accumulation of genetically abnormal cells, which can contribute to carcinogenesis. Lectins are neither enzymes nor antibodies but proteins that bind sugar chains. Among soluble endogenous lectins, galectins interact with cell surface sugar chains outside the cell to regulate signal transduction and cell growth. On the other hand, intracellular lectins are present at the plasma membrane and regulate signal transduction by regulating receptor–ligand interactions. Galectin-9 expressed on the surface of thymocytes induces apoptosis of T lymphocytes and plays an essential role in immune self-tolerance by negative selection in the thymus. Furthermore, the administration of extracellular galectin-9 induces apoptosis of human cancer and immunodeficient cells. However, the detailed pharmacokinetics of galectin-9 in vivo have not been elucidated. In addition, the cell surface receptors involved in galectin-9-induced apoptosis of cancer cells have not been identified, and the intracellular pathways involved in apoptosis have not been fully investigated. We have previously reported that galectin-9 induces apoptosis in various gastrointestinal cancers and suppresses tumor growth. However, the mechanism of galectin-9 and apoptosis induction in gastrointestinal cancers and the detailed mechanisms involved in tumor growth inhibition remain unknown. In this article, we review the effects of galectin-9 on gastrointestinal cancers and its mechanisms.

GLUT1 is a highly efficient L-fucose transporter

Understanding L-fucose metabolism is important because it is used as a therapy for several congenital disorders of glycosylation. Exogenous L-fucose can be activated and incorporated directly into multiple N- and O-glycans via the fucose salvage/recycling pathway. However, unlike for other monosaccharides, no mammalian L-fucose transporter has been identified. Here, we functionally screened nearly 140 annotated transporters and identified GLUT1 (SLC2A1) as an L-fucose transporter. We confirmed this assignment using multiple approaches to alter GLUT1 function, including chemical inhibition, siRNA knockdown, and gene KO. Collectively, all methods demonstrate that GLUT1 contributes significantly to L-fucose uptake and its utilization at low micromolar levels. Surprisingly, millimolar levels of D-glucose do not compete with L-fucose uptake. We also show macropinocytosis, but not other endocytic pathways, can contribute to L-fucose uptake and utilization. In conclusion, we determined that GLUT1 functions as the previously missing transporter component in mammalian L-fucose metabolism.

Lewis glycosphingolipids as critical determinants of TRAIL sensitivity in cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces cancer cell death and contributes to tumor rejection by cytotoxic lymphocytes in cancer immunosurveillance and immunotherapy. TRAIL and TRAIL receptor agonists have garnered wide popularity as promising agents for cancer therapy. We previously demonstrated that the loss of fucosylation in cancer cells impairs TRAIL sensitivity; however, the precise structures of the fucosylated glycans that regulate TRAIL sensitivity and their carrier molecules remain elusive. Herein, we observed that Lewis glycans among various fucosylated glycans positively regulate TRAIL-induced cell death. Specifically, Lewis glycans on lacto/neolacto glycosphingolipids, but not glycoproteins including TRAIL receptors, enhanced TRAIL-induced formation of the cytosolic caspase 8 complex, without affecting the formation of the membranous receptor complex. Furthermore, type I Lewis glycan expression in colon cancer cell lines and patient-derived cancer organoids was positively correlated with TRAIL sensitivity. These findings provide novel insights into the regulatory mechanism of TRAIL-induced cell death and facilitate the identification of novel predictive biomarkers for TRAIL-related cancer therapies in future.

Fucosylation in Urological Cancers

Fucosylation is an oligosaccharide modification that plays an important role in immune response and malignancy, and specific fucosyltransferases (FUTs) catalyze the three types of fucosylations: core-type, Lewis type, and H type. FUTs regulate cancer proliferation, invasiveness, and resistance to chemotherapy by modifying the glycosylation of signaling receptors. Oligosaccharides on PD-1/PD-L1 proteins are specifically fucosylated, leading to functional modifications. Expression of FUTs is upregulated in renal cell carcinoma, bladder cancer, and prostate cancer. Aberrant fucosylation in prostate-specific antigen (PSA) could be used as a novel biomarker for prostate cancer. Furthermore, elucidation of the biological function of fucosylation could result in the development of novel therapeutic targets. Further studies are needed in the field of fucosylation glycobiology in urological malignancies.

Simultaneous analysis of serum α2,3-linked sialylation and core-type fucosylation of prostate-specific antigen for the detection of high-grade prostate cancer

BACKGROUND

Altered prostate-specific antigen (PSA) glycosylation patterns can be useful biomarkers in detecting high-grade prostate cancer (HGPC). The microfluidic immunoassay system can analyse α2,3-linked sialylated PSA (α2,3-Sia-PSA) and α1,6-linked fucosylated PSA (α1,6-Fuc-PSA) using different lectins, Mackkia amurensis agglutinin and Pholiota squarrosa lectin, respectively. Here, we investigated the diagnostic value of simultaneous analysis of α2,3-Sia-PSA and α1,6-Fuc-PSA for the detection of HGPC.

METHODS

Men with serum PSA levels of 4-20 ng/mL who underwent prostate biopsy were included. The model to predict HGPC (Gleason grade ≥2) was constructed by multivariate logistic regression analysis, in combination with α2,3-Sia-PSA and α1,6-Fuc-PSA (SF index).

RESULTS

In the development cohort (n = 150), the SF index showed good discrimination for HGPC (area under the receiver-operating curve (AUC) 0.842; 95% confidence interval (CI) 0.782-0.903), compared to the single PSA test (AUC 0.632, 95% CI 0.543-0.721), α2,3-Sia-PSA (AUC 0.711, 95% CI 0.629-0.793) and α1,6-Fuc-PSA (AUC 0.738, 95% CI 0.657-0.819). Decision-curve analysis showed the superior benefit of the SF index. In the validation cohort (n = 57), the SF index showed good discrimination for HGPC (AUC 0.769, 95% CI 0.643-0.895).

CONCLUSIONS

The SF index could differentiate HGPC, providing useful information for decision making for prostate biopsy in men with abnormal PSA levels.

Proteome-wide mapping of short-lived proteins in human cells

Rapid protein degradation enables cells to quickly modulate protein abundance. Dysregulation of short-lived proteins plays essential roles in disease pathogenesis. A focused map of short-lived proteins remains understudied. Cycloheximide, a translational inhibitor, is widely used in targeted studies to measure degradation kinetics for short-lived proteins. Here, we combined cycloheximide chase assays with advanced quantitative proteomics to map short-lived proteins under translational inhibition in four human cell lines. Among 11,747 quantified proteins, we identified 1,017 short-lived proteins (half-lives ≤ 8 h). These short-lived proteins are less abundant, evolutionarily younger, and less thermally stable than other proteins. We quantified 103 proteins with different stabilities among cell lines. We showed that U2OS and HCT116 cells express truncated forms of ATRX and GMDS, respectively, which have lower stability than their full-length counterparts. This study provides a large-scale resource of human short-lived proteins under translational arrest, leading to untapped avenues of protein regulation for therapeutic interventions.

TRAIL signaling promotes entosis in colorectal cancer

Entosis is a form of nonphagocytic cell-in-cell (CIC) interaction where a living cell enters into another. Tumors show evidence of entosis; however, factors controlling entosis remain to be elucidated. Here, we find that besides inducing apoptosis, TRAIL signaling is a potent activator of entosis in colon cancer cells. Initiation of both apoptosis and entosis requires TRAIL receptors DR4 and DR5; however, induction of apoptosis and entosis diverges at caspase-8 as its structural presence is sufficient for induction of entosis but not apoptosis. Although apoptosis and entosis are morphologically and biochemically distinct, knockout of Bax and Bak, or inhibition of caspases, also inhibits entotic cell death and promotes survival and release of inner cells. Analysis of colorectal cancer tumors reveals a significant association between TRAIL signaling and CIC structures. Finally, the presence of CIC structures in the invasive front regions of colorectal tumors shows a strong correlation with adverse patient prognosis.

Dynamic tracing of sugar metabolism reveals the mechanisms of action of synthetic sugar analogs

Synthetic sugar analogs are widely applied in metabolic oligosaccharide engineering (MOE) and as novel drugs to interfere with glycoconjugate biosynthesis. However, mechanistic insights on their exact cellular metabolism over time are mostly lacking. We combined ion-pair ultrahigh performance liquid chromatography–triple quadrupole mass spectrometry mass spectrometry using tributyl- and triethylamine buffers for sensitive analysis of sugar metabolites in cells and organisms and identified low abundant nucleotide sugars, such as UDP-arabinose in human cell lines and CMP-sialic acid (CMP-NeuNAc) in Drosophila. Furthermore, MOE revealed that propargyloxycarbonyl (Poc)-labeled ManNPoc was metabolized to both CMP-NeuNPoc and UDP-GlcNPoc. Finally, time-course analysis of the effect of antitumor compound 3F_ax-NeuNAc by incubation of B16-F10 melanoma cells with N-acetyl-D-[UL-¹³C6]glucosamine revealed full depletion of endogenous ManNAc 6-phosphate and CMP-NeuNAc within 24 h. Thus, dynamic tracing of sugar metabolic pathways provides a general approach to reveal time-dependent insights into the metabolism of synthetic sugars, which is important for the rational design of analogs with optimized effects.

Protein fucosylation is required for Notch dependent vascular integrity in zebrafish

The onset of circulation in a developing embryo requires intact blood vessels to prevent hemorrhage. The development of endothelial cells, and their subsequent recruitment of perivascular mural cells are important processes to establish and maintain vascular integrity. These processes are genetically controlled during development, and mutations that affect endothelial cell specification, pattern formation, or maturation through the addition of mural cells can result in early developmental hemorrhage. We created a strong loss of function allele of the zebrafish GDP-mannose 4,6 dehydratase (gmds) gene that is required for the de novo synthesis of GDP-fucose, and homozygous embryos display cerebral hemorrhages. Our data demonstrate that gmds mutants have early defects in vascular patterning with ectopic branches observed at time of hemorrhage. Subsequently, defects in the number of mural cells that line the vasculature are observed. Moreover, activation of Notch signaling rescued hemorrhage phenotypes in gmds mutants, highlighting a potential downstream pathway that requires protein fucosylation for vascular integrity. Finally, supplementation with fucose can rescue hemorrhage frequency in gmds mutants, demonstrating that synthesis of GDP-fucose via an alternative (salvage) pathway may provide an avenue toward therapeutic correction of phenotypes observed due to defects in de novo GDP-fucose synthesis. Together, these data are consistent with a novel role for the de novo and salvage protein fucosylation pathways in regulating vascular integrity through a Notch dependent mechanism.

Sweet modification and regulation of death receptor signaling pathway

Death receptors, members of the tumor necrosis factor receptor (TNFR) superfamily, are characterized by the presence of a death domain in the cytosolic region. TNFR1, Fas, and TNF-related apoptosis-inducing ligand receptors, which are prototypical death receptors, exert pleiotropic functions in cell death, inflammation, and immune surveillance. Hence, they are involved in several human diseases. The activation of death receptors and downstream intracellular signaling are regulated by various post-translational modifications, such as phosphorylation, ubiquitination, and glycosylation. Glycosylation is one of the most abundant and versatile modifications to proteins and lipids, and it plays a critical role in the development and physiology of organisms, as well as the pathology of many human diseases. Glycans control a number of cellular events, such as receptor activation, signal transduction, endocytosis, cell recognition, and cell adhesion. It has been demonstrated that oligo- and monosaccharides modify death receptors and intracellular signaling proteins, and regulate their functions. Here, we review the current understanding of glycan modifications of death receptor signaling and their impact on signaling activity.

Genome-wide comparative analyses reveal selection signatures underlying adaptation and production in Tibetan and Poll Dorset sheep

The identification of genome-wide selection signatures can provide insights on the mechanisms of natural and/or artificial selection and uncover genes related to biological functions and/or phenotypes. Tibetan sheep are an important livestock in Tibet, providing meat and wool for Tibetans who are renown for breeding livestock that adapt well to high altitudes. Using whole-genome sequences with an effective sequencing depth of 5×, we investigated the genomic diversity and structure and, identified selection signatures of White Tibetan, Oula and Poll Dorset sheep. We obtained 30,163,679 Single Nucleotide Polymorphisms (SNPs) and 5,388,372 indels benchmarked against the ovine Oar_v4.0 genome assembly. Next, using F_ST, ZHp and XP-EHH approaches, we identified selection signatures spanning a set of candidate genes, including HIF1A, CAPN3, PRKAA1, RXFP2, TRHR and HOXA10 that are associated with pathways and GO categories putatively related to hypoxia responses, meat traits and disease resistance. Candidate genes and GO terms associated with coat color were also identified. Finally, quantification of blood physiological parameters, revealed higher levels of mean corpuscular hemoglobin measurement and mean corpuscular hemoglobin concentration in Tibetan sheep compared with Poll Dorset, suggesting a greater oxygen-carrying capacity in the Tibetan sheep and thus better adaptation to high-altitude hypoxia. In conclusion, this study provides a greater understanding of genome diversity and variations associated with adaptive and production traits in sheep.

Notch-Regulated Dendritic Cells Restrain Inflammation-Associated Colorectal Carcinogenesis

Conventional dendritic cells (cDC) play a central role in T-cell antitumor responses. We studied the significance of Notch-regulated DC immune responses in a mouse model of colitis-associated colorectal cancer in which there is epithelial downregulation of Notch/Hes1 signaling. This defect phenocopies that caused by GMDS (GDP-mannose 4,6-dehydratase) mutation in human colorectal cancers. We found that, although wild-type immune cells restrained dysplasia progression and decreased the incidence of adenocarcinoma in chimeric mice, the immune system with Notch2 deleted in all blood lineages or in only DCs promoted inflammation-associated transformation. Notch2 signaling deficiency not only impaired cDC terminal differentiation, but also downregulated CCR7 expression, reduced DC migration, and suppressed antigen cross-presentation to CD8⁺ T cells. Transfer of Notch-primed DCs restrained inflammation-associated dysplasia progression. Consistent with the mouse data, we observed a correlation between infiltrating cDC1 and Notch2 signaling in human colorectal cancers and found that GMDS-mutant colorectal cancers showed decreased CCR7 expression and suppressed cDC1 signature gene expression. Suppressed cDC1 gene signature expression in human colorectal cancer was associated with a poor prognosis. In summary, our study supports an important role for Notch2 signaling in cDC1-mediated antitumor immunity and indicates that Notch2-controlled DCs restrain inflammation-associated colon cancer development in mice.

Fucosylated C4b-binding protein α-chain, a novel serum biomarker that predicts lymph node metastasis in pancreatic ductal adenocarcinoma

C4b-binding protein α-chain (C4BPA) was previously identified as a novel serum biomarker for pancreatic ductal adenocarcinoma (PDAC). To apply this biomarker for clinical diagnosis, a lectin ELISA was established to measure serum fucosylated (Fuc)-C4BPA levels in 45 patients with PDAC, 20 patients with chronic pancreatitis (CP) and 50 healthy volunteers (HVs) in one training and three validation sets. The lecithin ELISA developed in the current study exhibited satisfactory within-run (2.6–6.7%) and between-day (1.8–3.6%) coefficient of variations. Serum Fuc-C4BPA levels in patients with PDAC (0.54±0.27 AU/ml) was significantly higher than that in HVs (0.21±0.06 AU/ml; P<0.0001) and patients with CP (0.25±0.03 AU/ml; P<0.0001). Additionally, serum Fuc-C4BPA levels in preoperative patients were significantly decreased compared with postoperative patient sera (P<0.0003). The receiver operating characteristic (ROC) curve analyses revealed that the area under the curve (AUC) of Fuc-C4BPA (0.985) was higher than that of carbohydrate antigen (CA)19-9 (0.843), carcinoembryonic antigen (0.548) and total C4BPA (0.875) (P<0.001). To analyze the clinical significance of Fuc-C4BPA, the ability of Fuc-C4BPA to predict lymph node metastasis was compared with that of CA19-9. The AUC of serum Fuc-C4BPA levels (0.703) was significantly higher than that of serum CA19-9 levels (0.500) in patients with PDAC (P<0.001). The current study established a novel lectin ELISA for measuring serum Fuc-C4BPA levels. Thus, Fuc-C4BPA has potential clinical applications owing to its high diagnostic value in PDAC.

Synthetic Fluorinated l-Fucose Analogs Inhibit Proliferation of Cancer Cells and Primary Endothelial Cells

Fucosylation is one of the most prevalent modifications on N- and O-glycans of glycoproteins, and it plays an important role in various cellular processes and diseases. Small molecule inhibitors of fucosylation have shown promise as therapeutic agents for sickle cell disease, arthritis, and cancer. We describe here the design and synthesis of a panel of fluorinated l-fucose analogs bearing fluorine atoms at the C2 and/or C6 positions of l-fucose as metabolic fucosylation inhibitors. Preliminary study of their effects on cell proliferation revealed that the 6,6-difluoro-l-fucose (3) and 6,6,6-trifluoro-l-fucose (6) showed significant inhibitory activity against proliferation of human colon cancer cells and human umbilical vein endothelial cells. In contrast, the previously reported 2-deoxy-2-fluoro-l-fucose (1) had no apparent effects on proliferations of all the cell lines tested. To understand the mechanism of cell proliferation inhibition by the fluorinated l-fucose analogs, we performed chemoenzymatic synthesis of the corresponding GDP-fluorinated l-fucose analogs and tested their inhibitory activities against the mammalian α1,6-fucosyltransferase (FUT8). Interestingly, the corresponding GDP derivatives of 6,6-difluoro-l-fucose (3) and 6,6,6-trifluoro-l-fucose (6), which are the stronger proliferation inhibitors, showed much weaker inhibitory activity against FUT8 than that of the 2-deoxy-2-fluoro-l-fucose (1). These results suggest that FUT8 is not the major target of the 6-fluorinated fucose analogs (3 and 6). Instead, other factors, such as the key enzymes involved in the de novo GDP-fucose biosynthetic pathway and/or other fucosyltransferases involved in the biosynthesis of tumor-associated glyco-epitopes are most likely the targets of the fluorinated l-fucose analogs to achieve cell proliferation inhibition. To our knowledge, this is the first comparative study of various fluorinated l-fucose analogs for suppressing the proliferation of human cancer and primary endothelial cells required for angiogenesis.

van Vliet S. FUT9-Driven Programming of Colon Cancer Cells towards a Stem Cell-Like State

Cancer stem cells (CSCs) are located in dedicated niches, where they remain inert to chemotherapeutic drugs and drive metastasis. Although plasticity in the CSC pool is well appreciated, the molecular mechanisms implicated in the regulation of cancer stemness are still elusive. Here, we define a fucosylation-dependent reprogramming of colon cancer cells towards a stem cell-like phenotype and function. De novo transcriptional activation of Fut9 in the murine colon adenocarcinoma cell line, MC38, followed by RNA seq-based regulon analysis, revealed major gene regulatory networks related to stemness. Lewis^x, Sox2, ALDH and CD44 expression, tumorsphere formation, resistance to 5-FU treatment and in vivo tumor growth were increased in FUT9-expressing MC38 cells compared to the control cells. Likewise, human CRC cell lines highly expressing FUT9 displayed phenotypic features of CSCs, which were significantly impaired upon FUT9 knock-out. Finally, in primary CRC FUT9⁺ tumor cells pathways related to cancer stemness were enriched, providing a clinically meaningful annotation of the complicity of FUT9 in stemness regulation and may open new avenues for therapeutic intervention.

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.

Functional glycomics: Application to medical science and hepatology

Glycomics refers to the comprehensive analysis of glycans. Recent progress in glycotechnology enables the determination of a variety of biological functions of glycans. Among different glycosylation patterns, certain types of aberrant glycosylation are linked to cancer and/or inflammation, and thus have biological importance. Glycotechnology has been applied to many fields of medical science, including hepatology. In particular, dramatic changes in glycosylation are observed in the progression of liver diseases. As the liver produces so many serum glycoproteins, changes in glycosylation of these proteins might provide useful disease biomarkers. Furthermore, many patients with genetic diseases of glycosylation who have liver dysfunction have been found as a result from whole genome sequencing, and various kinds of glycotherapy have been developed, especially in immunotherapy. In this review, we describe our basic knowledge of glycobiology and discuss the application of these data to medical science, especially hepatology.

The Role of TRAIL/DRs in the Modulation of Immune Cells and Responses

Expression of TRAIL (tumor necrosis factor–related apoptosis–inducing ligand) by immune cells can lead to the induction of apoptosis in tumor cells. However, it becomes increasingly clear that the interaction of TRAIL and its death receptors (DRs) can also directly impact immune cells and influence immune responses. Here, we review what is known about the role of TRAIL/DRs in immune cells and immune responses in general and in the tumor microenvironment in particular.

The TRAIL to cancer therapy: Hindrances and potential solutions

Apoptosis is an ordered and orchestrated cellular process that occurs in physiological and pathological conditions. Resistance to apoptosis is a hallmark of virtually all malignancies. Despite being a cause of pathological conditions, apoptosis could be a promising target in cancer treatment. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of TNF cytokine superfamily. It is a potent anti-cancer agent owing to its specific targeting towards cancerous cells, while sparing normal cells, to induce apoptosis. However, resistance occurs either intrinsically or after multiple treatments which may explain why cancer therapy fails. This review summarizes the apoptotic mechanisms via extrinsic and intrinsic apoptotic pathways, as well as the apoptotic resistance mechanisms. It also reviews the current clinically tested recombinant human TRAIL (rhTRAIL) and TRAIL receptor agonists (TRAs) against TRAIL-Receptors, TRAIL-R1 and TRAIL-R2, in which the outcomes of the clinical trials have not been satisfactory. Finally, this review discusses the current strategies in overcoming resistance to TRAIL-induced apoptosis in pre-clinical and clinical settings.

Protein Glycosylation and Tumor Microenvironment Alterations Driving Cancer Hallmarks

Decades of research have disclosed a plethora of alterations in protein glycosylation that decisively impact in all stages of disease and ultimately contribute to more aggressive cell phenotypes. The biosynthesis of cancer-associated glycans and its reflection in the glycoproteome is driven by microenvironmental cues and these events act synergistically toward disease evolution. Such intricate crosstalk provides the molecular foundations for the activation of relevant oncogenic pathways and leads to functional alterations driving invasion and disease dissemination. However, it also provides an important source of relevant glyco(neo)epitopes holding tremendous potential for clinical intervention. Therefore, we highlight the transversal nature of glycans throughout the currently accepted cancer hallmarks, with emphasis on the crosstalk between glycans and the tumor microenvironment stromal components. Focus is also set on the pressing need to include glycans and glycoconjugates in comprehensive panomics models envisaging molecular-based precision medicine capable of improving patient care. We foresee that this may provide the necessary rationale for more comprehensive studies and molecular-based intervention.

N-Glycomic and Transcriptomic Changes Associated with CDX1 mRNA Expression in Colorectal Cancer Cell Lines

The caudal-related homeobox protein 1 (CDX1) is a transcription factor, which is important in the development, differentiation, and homeostasis of the gut. Although the involvement of CDX genes in the regulation of the expression levels of a few glycosyltransferases has been shown, associations between glycosylation phenotypes and CDX1 mRNA expression have hitherto not been well studied. Triggered by our previous study, we here characterized the N-glycomic phenotype of 16 colon cancer cell lines, selected for their differential CDX1 mRNA expression levels. We found that high CDX1 mRNA expression associated with a higher degree of multi-fucosylation on N-glycans, which is in line with our previous results and was supported by up-regulated gene expression of fucosyltransferases involved in antenna fucosylation. Interestingly, hepatocyte nuclear factors (HNF)4A and HNF1A were, among others, positively associated with high CDX1 mRNA expression and have been previously proven to regulate antenna fucosylation. Besides fucosylation, we found that high CDX1 mRNA expression in cancer cell lines also associated with low levels of sialylation and galactosylation and high levels of bisection on N-glycans. Altogether, our data highlight a possible role of CDX1 in altering the N-glycosylation of colorectal cancer cells, which is a hallmark of tumor development.

Fucosylation in cancer biology and its clinical applications

Fucosylation is the process of transferring fucose from GDP-fucose to their substrates, which includes certain proteins, N- and O-linked glycans in glycoprotein or glycolipids, by fucosyltransferases in all mammalian cells. Fucosylated glycans play vital role in selectin-mediated leukocyte extravasation, lymphocyte homing, and pathogen-host interactions, whereas fucosylated proteins are essential for signaling transduction in numerous ontogenic events. Aberrant fucosylation due to the availability of high energy donor GDP-fucose, abnormal expression of FUTs and/or α-fucosidase, and the availability of their substrates leads to different fucosylated glycan or protein structures. Accumulating evidence demonstrates that aberrant fucosylation plays important role in all aspects of cancer biology. In this review, we will summarize the current knowledge about fucosylation in different physiological and pathological processes with a focus on their roles not only in cancer cell proliferation, invasion, and metastasis but also in tumor immune surveillance. Furthermore, the clinical potential and applications of fucosylation in cancer diagnosis and treatment will also be discussed.

Death receptor 5 is activated by fucosylation in colon cancer cells

The remarkable pro‐apoptotic properties of tumour necrosis factor (TNF)‐related apoptosis‐inducing ligand (TRAIL) have led to considerable interest in this protein as a potential anticancer therapeutic. However, TRAIL is largely ineffective in inducing apoptosis in certain cancer cells, and the mechanisms underlying this selectivity are unknown. In colon adenocarcinomas, posttranslational modifications including O‐ and N‐ glycosylation of death receptors were found to correlate with TRAIL‐induced apoptosis. Additionally, mRNA levels of fucosyltransferase 3 (FUT3) and 6 (FUT6) were found to be high in the TRAIL‐sensitive colon adenocarcinoma cell line COLO 205. In this study, we use agonistic receptor‐specific TRAIL variants to dissect the contribution of FUT3 and FUT6‐mediated fucosylation to TRAIL‐induced apoptosis via its two death receptors, DR4 and DR5. Triggering of apoptosis by TRAIL revealed that the low FUT3/6‐expressing cells DLD‐1 and HCT 116 are insensitive to DR5 but not to DR4‐mediated apoptosis. By contrast, efficient apoptosis is mediated via both receptors in high FUT3/6‐expressing COLO 205 cells. The reconstitution of FUT3/6 expression in DR5‐resistant cells completely restored TRAIL sensitivity via this receptor, while only marginally enhancing apoptosis via DR4 at lower TRAIL concentrations. Interestingly, we observed that induction of the salvage pathway by external administration of l‐fucose restores DR5‐mediated apoptosis in both DLD‐1 and HCT 116 cells. Finally, we show that fucosylation influences the ligand‐independent receptor association that leads to increased death inducing signalling complex (DISC) formation and caspase‐8 activation. Taken together, these results provide evidence for the differential impact of fucosylation on signalling via DR4 or DR5. These findings provide novel opportunities to enhance TRAIL sensitivity in colon adenocarcinoma cells that are highly resistant to DR5‐mediated apoptosis.

High TSTA3 Expression as a Candidate Biomarker for Poor Prognosis of Patients With ESCC

Esophageal squamous cell carcinoma is the sixth most lethal cancer worldwide and the fourth most lethal cancer in China. Tissue-specific transplantation antigen P35B codifies the enzyme GDP-d-mannose-4,6-dehydratase, which participates in the biosynthesis of GDP-l-fucose. GDP-l-fucose is an important substrate involved in the biosynthesis of many glycoproteins. Cancer cells are often accompanied by the changes in glycoprotein structure, which affects the adhesion, invasion, and metastasis of cells. It is not clear whether tissue-specific transplantation antigen P35B has any effect on the development of esophageal squamous cell carcinoma. We used an immunohistochemical method to assess the expression of tissue-specific transplantation antigen P35B in 104 esophageal squamous cell carcinoma samples. The results showed tissue-specific transplantation antigen P35B expression was associated with some clinical features in patients, such as age (P = .017), clinical stage (P = .010), and lymph node metastasis (P = .043). Kaplan-Meier analysis and log-rank test showed that patients with esophageal squamous cell carcinoma having high tissue-specific transplantation antigen P35B expression had a worse prognosis compared to the patients with low expression (P = .048). Multivariate Cox proportional hazards regression model showed that high expression of tissue-specific transplantation antigen P35B could predict poor prognosis for patients with esophageal squamous cell carcinoma independently. In conclusion, abnormal fucosylation might participate in the progress of esophageal squamous cell carcinoma and tissue-specific transplantation antigen P35B may serve as a novel biomarker for prognosis of patients with esophageal squamous cell carcinoma.

Pathogenic Variants in Fucokinase Cause a Congenital Disorder of Glycosylation

FUK encodes fucokinase, the only enzyme capable of converting L-fucose to fucose-1-phosphate, which will ultimately be used for synthesizing GDP-fucose, the donor substrate for all fucosyltransferases. Although it is essential for fucose salvage, this pathway is thought to make only a minor contribution to the total amount of GDP-fucose. A second pathway, the major de novo pathway, involves conversion of GDP-mannose to GDP-fucose. Here we describe two unrelated individuals who have pathogenic variants in FUK and who presented with severe developmental delays, encephalopathy, intractable seizures, and hypotonia. The first individual was compound heterozygous for c.667T>C (p.Ser223Pro) and c.2047C>T (p.Arg683Cys), and the second individual was homozygous for c.2980A>C (p.Lys994Gln). Skin fibroblasts from the first individual confirmed the variants as loss of function and showed significant decreases in total GDP-[³H] fucose and [³H] fucose-1-phosphate. There was also a decrease in the incorporation of [5,6-³H]-fucose into fucosylated glycoproteins. Lys994 has previously been shown to be an important site for ubiquitin conjugation. Here, we show that loss-of-function variants in FUK cause a congenital glycosylation disorder characterized by a defective fucose-salvage pathway.

Glycomic Profiling Highlights Increased Fucosylation in Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a subtype of mucinous adenocarcinoma that most often originates from the appendix, and grows in the peritoneal cavity filling it with mucinous ascites. KRAS and GNAS mutations are frequently found in PMP, but other common driver mutations are infrequent. As altered glycosylation can promote carcinogenesis, we compared N-linked glycan profiles of PMP tissues to those of normal appendix. Glycan profiles of eight normal appendix samples and eight low-grade and eight high-grade PMP specimens were analyzed by mass spectrometry. Our results show differences in glycan profiles between PMP and the controls, especially in those of neutral glycans, and the most prominent alteration was increased fucosylation. We further demonstrate up-regulated mRNA expression of four fucosylation-related enzymes, the core fucosylation performing fucosyltransferase 8 and three GDP-fucose biosynthetic enzymes in PMP tissues when compared with the controls. Up-regulated protein expression of the latter three enzymes was further observed in PMP cells by immunohistochemistry. We also demonstrate that restoration of fucosylation either by salvage pathway or by introduction of an expression of intact GDP-mannose 4,6-dehydratase enhance expression of MUC2, which is the predominant mucin molecule secreted by the PMP cells, in an intestinal-derived adenocarcinoma cell line with defective fucosylation because of deletion in the GDP-mannose 4,6-dehydratase gene. Thus, altered glycosylation especially in the form of fucosylation is linked to the characteristic mucin production of PMP. Glycomic data are available via ProteomeXchange with identifier PXD010086.

Biological functions of fucose in mammals

Fucose is a 6-deoxy hexose in the l-configuration found in a large variety of different organisms. In mammals, fucose is incorporated into N-glycans, O-glycans and glycolipids by 13 fucosyltransferases, all of which utilize the nucleotide-charged form, GDP-fucose, to modify targets. Three of the fucosyltransferases, FUT8, FUT12/POFUT1 and FUT13/POFUT2, are essential for proper development in mice. Fucose modifications have also been implicated in many other biological functions including immunity and cancer. Congenital mutations of a Golgi apparatus localized GDP-fucose transporter causes leukocyte adhesion deficiency type II, which results in severe developmental and immune deficiencies, highlighting the important role fucose plays in these processes. Additionally, changes in levels of fucosylated proteins have proven as useful tools for determining cancer diagnosis and prognosis. Chemically modified fucose analogs can be used to alter many of these fucose dependent processes or as tools to better understand them. In this review, we summarize the known roles of fucose in mammalian physiology and pathophysiology. Additionally, we discuss recent therapeutic advances for cancer and other diseases that are a direct result of our improved understanding of the role that fucose plays in these systems.

GMDS knockdown impairs cell proliferation and survival in human lung adenocarcinoma

Background

Lung adenocarcinoma is the most common type of lung cancer and one of the most lethal and prevalent cancers. Aberrant glycosylation was common and essential in tumorigenesis, with fucosylation as one of the most common types disrupted in cancers. However, it is still unknown whether genes involved in fucosylation are important for lung adenocarcinoma development and process.

Methods

GMDS is involved in cellular fucosylation. Here we examined GMDS expression level at both mRNA and protein level in lung adenocarcinoma. The impact of GMDS knockdown on lung adenocarcinoma in vitro and in vivo was investigated. Transcriptome changes with GMDS knockdown in lung adenocarcinoma cells were also examined to provide insights into related molecular mechanisms.

Results

GMDS expression is significantly upregulated in lung adenocarcinoma at both mRNA and protein levels. Lentivirus-mediated shRNA strategy inhibited GMDS expression efficiently in human lung adenocarcinoma cells A549 and H1299, and GMDS knockdown impaired cell proliferation, colony formation ability, induced cell cycle arrest, and apoptosis in both cell lines. Furthermore, GMDS knockdown inhibited tumorigenesis in a xenograft mice model of lung adenocarcinoma. Microarray analysis explored the GMDS-mediated molecular network and revealed that the CASP8-CDKN1A axis might be critical for lung adenocarcinoma development.

Conclusions

These findings suggest that GMDS upregulation is critical for cell proliferation and survival in human lung adenocarcinoma and might serve as a potential biomarker for lung adenocarcinoma diagnosis and treatment.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4524-1) contains supplementary material, which is available to authorized users.

Regulation of TNF-Related Apoptosis-Inducing Ligand Signaling by Glycosylation

Tumor necrosis-factor related apoptosis-inducing ligand, also known as TRAIL or APO2L (Apo-2 ligand), is a cytokine of the TNF superfamily acknowledged for its ability to trigger selective apoptosis in tumor cells while being relatively safe towards normal cells. Its binding to its cognate agonist receptors, namely death receptor 4 (DR4) and/or DR5, can induce the formation of a membrane-bound macromolecular complex, coined DISC (death-signaling inducing complex), necessary and sufficient to engage the apoptotic machinery. At the very proximal level, TRAIL DISC formation and activation of apoptosis is regulated both by antagonist receptors and by glycosylation. Remarkably, though, despite the fact that all membrane-bound TRAIL receptors harbor putative glycosylation sites, only pro-apoptotic signaling through DR4 and DR5 has, so far, been found to be regulated by N- and O-glycosylation, respectively. Because putative N-glycosylation sequons and O-glycosylation sites are also found and conserved in all these receptors throughout all animal species (in which these receptors have been identified), glycosylation is likely to play a more prominent role than anticipated in regulating receptor/receptor interactions or trafficking, ultimately defining cell fate through TRAIL stimulation. This review aims to present and discuss these emerging concepts, the comprehension of which is likely to lead to innovative anticancer therapies.

Establishment of an antibody specific for cancer-associated haptoglobin: a possible implication of clinical investigation

We previously found that the serum level of fucosylated haptoglobin (Fuc-Hpt) was significantly increased in pancreatic cancer patients. To delineate the mechanism underlying this increase and develop a simple detection method, we set out to generate a monoclonal antibody (mAb) specific for Fuc-Hpt. After multiple screenings by enzyme-linked immunosorbent assay (ELISA), a 10-7G mAb was identified as being highly specific for Fuc-Hpt generated in a cell line as well as for Hpt derived from a pancreatic cancer patient. As a result from affinity chromatography with 10-7G mAb, followed by lectin blot and mass spectrometry analyses, it was found that 10-7G mAb predominantly recognized both Fuc-Hpt and prohaptoglobin (proHpt), which was also fucosylated. In immunohistochemical analyses, hepatocytes surrounding metastasized cancer cells were stained by the 10-7G mAb, but neither the original cancer cells themselves nor normal hepatocytes exhibited positive staining, suggesting that metastasized cancer cells promote Fuc-Hpt production in adjacent hepatocytes. Serum level of Fuc-Hpt determined with newly developed ELISA system using the 10-7G mAb, was increased in patients of pancreatic and colorectal cancer. Interestingly, dramatic increases in Fuc-Hpt levels were observed at the stage IV of colorectal cancer. These results indicate that the 10-7G mAb developed is a promising antibody which recognizes Fuc-Hpt and could be a useful diagnostic tool for detecting liver metastasis of cancer.

Stage Dependence, Cell-Origin Independence, and Prognostic Capacity of Serum Glycan Fucosylation, β1-4 Branching, β1-6 Branching, and α2-6 Sialylation in Cancer

Glycans represent a promising but only marginally accessed source of cancer markers. We previously reported the development of a molecularly bottom-up approach to plasma and serum (P/S) glycomics based on glycan linkage analysis that captures features such as α2-6 sialylation, β1-6 branching, and core fucosylation as single analytical signals. Based on the behavior of P/S glycans established to date, we hypothesized that the alteration of P/S glycans observed in cancer would be independent of the tissue in which the tumor originated yet exhibit stage dependence that varied little between cancers classified on the basis of tumor origin. Herein, the diagnostic utility of this bottom-up approach as applied to lung cancer patients (n = 127 stage I; n = 20 stage II; n = 81 stage III; and n = 90 stage IV) as well as prostate (n = 40 stage II), serous ovarian (n = 59 stage III), and pancreatic cancer patients (n = 15 rapid autopsy) compared to certifiably healthy individuals (n = 30), nominally healthy individuals (n = 166), and risk-matched controls (n = 300) is reported. Diagnostic performance in lung cancer was stage-dependent, with markers for terminal (total) fucosylation, α2-6 sialylation, β1-4 branching, β1-6 branching, and outer-arm fucosylation most able to differentiate cases from controls. These markers behaved in a similar stage-dependent manner in other types of cancer as well. Notable differences between certifiably healthy individuals and case-matched controls were observed. These markers were not significantly elevated in liver fibrosis. Using a Cox proportional hazards regression model, the marker for α2-6 sialylation was found to predict both progression and survival in lung cancer patients after adjusting for age, gender, smoking status, and stage. The potential mechanistic role of aberrant P/S glycans in cancer progression is discussed.

The role of N-glycans in colorectal cancer progression: potential biomarkers and therapeutic applications

Changes in glycosylation, which is one of the most common protein post-translational modifications, are considered to be a hallmark of cancer. N-glycans can modulate cell migration, cell-cell adhesion, cell signaling, growth and metastasis. The colorectal cancer (CRC) is a leading cause of cancer-related mortality and the correlation between CRC progression and changes in the pattern of expression of N-glycans is being considered in the search for new biomarkers. Here, we review the role of N-glycans in CRC cell biology. The perspectives on emerging N-glycan-related anticancer therapies, along with new insights and challenges, are also discussed.

High-Sensitivity and Low-Toxicity Fucose Probe for Glycan Imaging and Biomarker Discovery

Fucose, a terminal sugar in glycoconjugates, critically regulates various physiological and pathological phenomena, including cancer development and inflammation. However, there are currently no probes for efficient labeling and detection of this sugar. We chemically synthesized a novel series of alkynyl-fucose analogs as probe candidates and found that 7-alkynyl-fucose gave the highest labeling efficiency and low cytotoxicity. Among the fucose analogs, 7-alkynyl-fucose was the best substrate against all five fucosyltransferases examined. We confirmed its conversion to the corresponding guanosine diphosphate derivative in cells and found that cellular glycoproteins were labeled much more efficiently with 7-alkynyl-fucose than with an existing probe. 7-Alkynyl-fucose was detected in the N-glycan core by mass spectrometry, and 7-alkynyl-fucose-modified proteins mostly disappeared in core-fucose-deficient mouse embryonic fibroblasts, suggesting that this analog mainly labeled core fucose in these cells. These results indicate that 7-alkynyl-fucose is a highly sensitive and powerful tool for basic glycobiology research and clinical application for biomarker discovery.

An Alkynyl-Fucose Halts Hepatoma Cell Migration and Invasion by Inhibiting GDP-Fucose-Synthesizing Enzyme FX, TSTA3

Fucosylation is a glycan modification critically involved in cancer and inflammation. Although potent fucosylation inhibitors are useful for basic and clinical research, only a few inhibitors have been developed. Here, we focus on a fucose analog with an alkyne group, 6-alkynyl-fucose (6-Alk-Fuc), which is used widely as a detection probe for fucosylated glycans, but is also suggested for use as a fucosylation inhibitor. Our glycan analysis using lectin and mass spectrometry demonstrated that 6-Alk-Fuc is a potent and general inhibitor of cellular fucosylation, with much higher potency than the existing inhibitor, 2-fluoro-fucose (2-F-Fuc). The action mechanism was shown to deplete cellular GDP-Fuc, and the direct target of 6-Alk-Fuc is FX (encoded by TSTA3), the bifunctional GDP-Fuc synthase. We also show that 6-Alk-Fuc halts hepatoma invasion. These results highlight the unappreciated role of 6-Alk-Fuc as a fucosylation inhibitor and its potential use for basic and clinical science.

Inhibition of fucosylation by 2-fluorofucose suppresses human liver cancer HepG2 cell proliferation and migration as well as tumor formation

Core fucosylation is one of the most important glycosylation events in the progression of liver cancer. For this study, we used an easily handled L-fucose analog, 2-fluoro-L-fucose (2FF), which interferes with the normal synthesis of GDP-fucose, and verified its potential roles in regulating core fucosylation and cell behavior in the HepG2 liver cancer cell line. Results obtained from lectin blot and flow cytometry analysis clearly showed that 2FF treatment dramatically inhibited core fucosylation, which was also confirmed via mass spectrometry analysis. Cell proliferation and integrin-mediated cell migration were significantly suppressed in cells treated with 2FF. We further analyzed cell colony formation in soft agar and tumor xenograft efficacy, and found that both were greatly suppressed in the 2FF-treated cells, compared with the control cells. Moreover, the treatment with 2FF decreased the core fucosylation levels of membrane glycoproteins such as EGF receptor and integrin β1, which in turn suppressed downstream signals that included phospho-EGFR, -AKT, -ERK, and -FAK. These results clearly described the roles of 2FF and the importance of core fucosylation in liver cancer progression, suggesting 2FF shows promise for use in the treatment of hepatoma.

Novel Candidate Genes Underlying Extreme Trophic Specialization in Caribbean Pupfishes

The genetic changes responsible for evolutionary transitions from generalist to specialist phenotypes are poorly understood. Here we examine the genetic basis of craniofacial traits enabling novel trophic specialization in a sympatric radiation of Cyprinodon pupfishes endemic to San Salvador Island, Bahamas. This recent radiation consists of a generalist species and two novel specialists: a small-jawed "snail-eater" and a large-jawed "scale-eater." We genotyped 12 million single nucleotide polymorphisms (SNPs) by whole-genome resequencing of 37 individuals of all three species from nine populations and integrated genome-wide divergence scans with association mapping to identify divergent regions containing putatively causal SNPs affecting jaw size-the most rapidly diversifying trait in this radiation. A mere 22 fixed variants accompanied extreme ecological divergence between generalist and scale-eater species. We identified 31 regions (20 kb) containing variants fixed between specialists that were significantly associated with variation in jaw size which contained 11 genes annotated for skeletal system effects and 18 novel candidate genes never previously associated with craniofacial phenotypes. Six of these 31 regions showed robust signs of hard selective sweeps after accounting for demographic history. Our data are consistent with predictions based on quantitative genetic models of adaptation, suggesting that the effect sizes of regions influencing jaw phenotypes are positively correlated with distance between fitness peaks on a complex adaptive landscape.

[Role of Fucosylation in Cancer]

岩藻糖基化是重要的糖基化修饰方式，在哺乳动物中发挥重要作用，其参与ABO血型H抗原、Lewis血型抗原形成、选择素介导的白细胞外渗或归巢、宿主病原相互作用及信号通路修饰。在多种肿瘤中存在岩藻糖基化异常，其在肿瘤生长、侵袭、转移、免疫逃逸以及药物敏感性方面发挥重要作用，与肺癌的发生发展及预后密切相关。因此，靶向肿瘤中异常岩藻糖基化可能成为治疗肿瘤的新策略。本文将对岩藻糖基化在肿瘤发生发展中的作用进行综述。

Hyperglycemia exacerbates colon cancer malignancy through hexosamine biosynthetic pathway

Hyperglycemia is a common feature of diabetes mellitus, considered as a risk factor for cancer. However, its direct effects in cancer cell behavior are relatively unexplored. Herein we show that high glucose concentration induces aberrant glycosylation, increased cell proliferation, invasion and tumor progression of colon cancer. By modulating the activity of the rate-limiting enzyme, glutamine-fructose-6-phosphate amidotransferase (GFAT), we demonstrate that hexosamine biosynthetic pathway (HBP) is involved in those processes. Biopsies from patients with colon carcinoma show increased levels of GFAT and consequently aberrant glycans’ expression suggesting an increase of HBP flow in human colon cancer. All together, our results open the possibility that HBP links hyperglycemia, aberrant glycosylation and tumor malignancy, and suggest this pathway as a potential therapeutic target for colorectal cancer.

Selectin Ligands Sialyl-Lewis a and Sialyl-Lewis x in Gastrointestinal Cancers

The tetrasaccharide structures Siaα2,3Galβ1,3(Fucα1,4)GlcNAc and Siaα2,3Galβ1,4(Fucα1,3)GlcNAc constitute the epitopes of the carbohydrate antigens sialyl-Lewis a (sLe^a) and sialyl-Lewis x (sLe^x), respectively, and are the minimal requirement for selectin binding to their counter-receptors. Interaction of sLe^x expressed on the cell surface of leucocytes with E-selectin on endothelial cells allows their arrest and promotes their extravasation. Similarly, the rolling of cancer cells ectopically expressing the selectin ligands on endothelial cells is potentially a crucial step favoring the metastatic process. In this review, we focus on the biosynthetic steps giving rise to selectin ligand expression in cell lines and native tissues of gastrointestinal origin, trying to understand whether and how they are deregulated in cancer. We also discuss the use of such molecules in the diagnosis of gastrointestinal cancers, particularly in light of recent data questioning the ability of colon cancers to express sLe^a and the possible use of circulating sLe^x in the early detection of pancreatic cancer. Finally, we reviewed the data dealing with the mechanisms that link selectin ligand expression in gastrointestinal cells to cancer malignancy. This promising research field seems to require additional data on native patient tissues to reach more definitive conclusions.

Fucosylation Deficiency in Mice Leads to Colitis and Adenocarcinoma

BACKGROUND & AIMS

De novo synthesis of guanosine diphosphate (GDP)-fucose, a substrate for fucosylglycans, requires sequential reactions mediated by GDP-mannose 4,6-dehydratase (GMDS) and GDP-4-keto-6-deoxymannose 3,5-epimerase-4-reductase (FX or tissue specific transplantation antigen P35B [TSTA3]). GMDS deletions and mutations are found in 6%-13% of colorectal cancers; these mostly affect the ascending and transverse colon. We investigated whether a lack of fucosylation consequent to loss of GDP-fucose synthesis contributes to colon carcinogenesis.

METHODS

FX deficiency and GMDS deletion produce the same biochemical phenotype of GDP-fucose deficiency. We studied a mouse model of fucosylation deficiency (Fx-/- mice) and mice with the full-length Fx gene (controls). Mice were placed on standard chow or fucose-containing diet (equivalent to a control fucosylglycan phenotype). Colon tissues were collected and analyzed histologically or by enzyme-linked immunosorbent assays to measure cytokine levels; T cells also were collected and analyzed. Fecal samples were analyzed by 16s ribosomal RNA sequencing. Mucosal barrier function was measured by uptake of fluorescent dextran. We transplanted bone marrow cells from Fx-/- or control mice (Ly5.2) into irradiated 8-week-old Fx-/- or control mice (Ly5.1). We performed immunohistochemical analyses for expression of Notch and the hes family bHLH transcription factor (HES1) in colon tissues from mice and a panel of 60 human colorectal cancer specimens (27 left-sided, 33 right-sided).

RESULTS

Fx-/- mice developed colitis and serrated-like lesions. The intestinal pathology of Fx-/- mice was reversed by addition of fucose to the diet, which restored fucosylation via a salvage pathway. In the absence of fucosylation, dysplasia appeared and progressed to adenocarcinoma in up to 40% of mice, affecting mainly the right colon and cecum. Notch was not activated in Fx-/- mice fed standard chow, leading to decreased expression of its target Hes1. Fucosylation deficiency altered the composition of the fecal microbiota, reduced mucosal barrier function, and altered epithelial proliferation marked by Ki67. Fx-/- mice receiving control bone marrow cells had intestinal inflammation and dysplasia, and reduced expression of cytokines produced by cytotoxic T cells. Human sessile serrated adenomas and right-sided colorectal tumors with epigenetic loss of MutL homolog 1 (MLH1) had lost or had lower levels of HES1 than other colorectal tumor types or nontumor tissues.

CONCLUSIONS

In mice, fucosylation deficiency leads to colitis and adenocarcinoma, loss of Notch activation, and down-regulation of Hes1. HES1 loss correlates with the development of human right-sided colorectal tumors with epigenetic loss of MLH1. These findings indicate that carcinogenesis in a subset of colon cancer is consequent to a molecular mechanism driven by fucosylation deficiency and/or HES1-loss.

Cancer Therapy Due to Apoptosis: Galectin-9

Dysregulation of apoptosis is a major hallmark in cancer biology that might equip tumors with a higher malignant potential and chemoresistance. The anti-cancer activities of lectin, defined as a carbohydrate-binding protein that is not an enzyme or antibody, have been investigated for over a century. Recently, galectin-9, which has two distinct carbohydrate recognition domains connected by a linker peptide, was noted to induce apoptosis in thymocytes and immune cells. The apoptosis of these cells contributes to the development and regulation of acquired immunity. Furthermore, human recombinant galectin-9, hG9NC (null), which lacks an entire region of the linker peptide, was designed to resist proteolysis. The hG9NC (null) has demonstrated anti-cancer activities, including inducing apoptosis in hematological, dermatological and gastrointestinal malignancies. In this review, the molecular characteristics, history and apoptosis-inducing potential of galectin-9 are described.

Role of aberrant IgG glycosylation in the pathogenesis of inflammatory bowel disease

The intestine is one of the most important organs associated with the immune system. It is thought that disruption of intestinal immunity causes inflammatory bowel disease (IBD). Recent advances in immune glycobiology have provided novel insights into many human diseases. For example, studies of glycosylation remodeling in mice have underscored the importance of oligosaccharides in the pathogenesis of IBD. Furthermore, aberrant glycosylation of IgG is a good serum marker of IBD activity. In this review, we examine current understanding of the role of aberrant glycosylation in the pathogenesis of IBD in terms of our original data and recent reports.

The transcription factor ATF2 promotes melanoma metastasis by suppressing protein fucosylation

Melanoma is one of the most lethal skin cancers worldwide, primarily because of its propensity to metastasize. Thus, the elucidation of mechanisms that govern metastatic propensity is urgently needed. We found that protein kinase Cε (PKCε)-mediated activation of activating transcription factor 2 (ATF2) controls the migratory and invasive behaviors of melanoma cells. PKCε-dependent phosphorylation of ATF2 promoted its transcriptional repression of the gene encoding fucokinase (FUK), which mediates the fucose salvage pathway and thus global cellular protein fucosylation. In primary melanocytes and cell lines representing early-stage melanoma, the abundance of PKCε-phosphorylated ATF2 was low, thereby enabling the expression of FUK and cellular protein fucosylation, which promoted cellular adhesion and reduced motility. In contrast, increased expression of the gene encoding PKCε and abundance of phosphorylated, transcriptionally active ATF2 were observed in advanced-stage melanomas and correlated with decreased FUK expression, decreased cellular protein fucosylation, attenuated cell adhesion, and increased cell motility. Restoring fucosylation in mice either by dietary fucose supplementation or by genetic manipulation of murine Fuk expression attenuated primary melanoma growth, increased the number of intratumoral natural killer cells, and decreased distal metastasis in murine isograft models. Tumor microarray analysis of human melanoma specimens confirmed reduced fucosylation in metastatic tumors and a better prognosis for primary melanomas that had high abundance of fucosylation. Thus, inhibiting PKCε or ATF2 or increasing protein fucosylation in tumor cells may improve clinical outcome in melanoma patients.

Fut3 role in breast invasive ductal carcinoma: Investigating its gene promoter and protein expression

Fucosylated glycans synthesized by α1,3/4-fucosyltransferase (FUT3) enzyme play an important role in breast cancer prognosis and metastasis, being involved in the binding of circulating tumor cells to the endothelium and being related to tumor stage, metastatic potential and chemoresistance. Despite the pro-tumor action of this enzyme, studies have demonstrated its role in natural killer-induced cytotoxicity through the recognition of sialyl Lewis X by C-type lectin receptors and through extrinsic apoptosis pathway triggered by Apo2L-TRAIL. This study aimed to investigate the expression pattern of FUT3 in invasive breast carcinoma (IDC) from patients of Pernambuco state, Northeast of Brazil, and genotype FUT3 promoter region to identify possible SNPs that could be associated with variations in FUT3 expression. Immunohistochemistry assay was used to access the FUT3 expression in normal (n=11) and tumor tissues (n=85). DNA sequencing was performed to genotype the FUT3 promoter region in patients with IDC (n=109) and healthy controls (n=110). Our results demonstrated that the absence of FUT3 enzyme is related to breast's IDC. The non-expression of FUT3 was more frequent in larger lesions and also in HER2 negative IDC tumors. Genomic analysis showed that two variations localized in FUT3 promoter region are possibly associated with IDC. Our results suggest that minor allele T of SNP rs73920070 (-6933 C>T) confers protection whereas minor allele T of SNP rs2306969 (-6951 C>T) triggers to susceptibility to IDC in the population of Pernambuco state, Northeast of Brazil.