Bisected, complex N-glycans and galectins in mouse mammary tumor progression and human breast cancer

Regulation of intracellular activity of N-glycan branching enzymes in mammals

Most proteins in the secretory pathway are glycosylated, and N-glycans are estimated to be attached to over 7000 proteins in humans. As structural variation of N-glycans critically regulates the functions of a particular glycoprotein, it is pivotal to understand how structural diversity of N-glycans is generated in cells. One of the major factors conferring structural variation of N-glycans is the variable number of N-acetylglucosamine branches. These branch structures are biosynthesized by dedicated glycosyltransferases, including GnT-III (MGAT3), GnT-IVa (MGAT4A), GnT-IVb (MGAT4B), GnT-V (MGAT5), and GnT-IX (GnT-Vb, MGAT5B). In addition, the presence or absence of core modification of N-glycans, namely, core fucose (included as an N-glycan branch in this manuscript), synthesized by FUT8, also confers large structural variation on N-glycans, thereby crucially regulating many protein-protein interactions. Numerous biochemical and medical studies have revealed that these branch structures are involved in a wide range of physiological and pathological processes. However, the mechanisms regulating the activity of the biosynthetic glycosyltransferases are yet to be fully elucidated. In this review, we summarize the previous findings and recent updates regarding regulation of the activity of these N-glycan branching enzymes. We hope that such information will help readers to develop a comprehensive overview of the complex system regulating mammalian N-glycan maturation.

Galectin-8 involves in arthritic condylar bone loss via podoplanin/AKT/ERK axis-mediated inflammatory lymphangiogenesis

OBJECTIVE

The lymphatic system plays a crucial role in the maintenance of tissue fluid homeostasis and the immunological response to inflammation. Galectin-8 (Gal-8) regulates pathological lymphangiogenesis but the effects of which on inflammation-related condylar bone loss in temporomandibular joint (TMJ) have not been well studied.

DESIGN

We used TNFα-transgenic (TNF^TG) mice and their wildtype (WT) littermates to compare their inflammatory phenotype in TMJs. Next, lymphatic endothelial cells (LECs) were used to examine the effects of which on osteoclast formation, pro-inflammatory factor expression, and inflammatory lymphangiogenesis with or without thiodigalactoside (TDG, a Gal-8 inhibitor) treatment. At last, two murine models (TNF^TG arthritic model and forced mouth opening model) were used to explore TDG as a potential drug for the treatment of inflammation-related condylar bone loss.

RESULTS

In comparison to WT mice, lymphatic areas of lymphatic vessel endothelial receptor 1 (LYVE1)⁺/podoplanin (PDPN)⁺ and Gal-8⁺/PDPN⁺, TRAP-positive osteoclast number, and condylar bone loss are increased in TNF^TG mice. Inhibition of Gal-8 in LECs by TDG, reduces TNFα-induced osteoclast formation, pro-inflammatory factor expression, and inflammatory lymphangiogenesis. In addition, Gal-8 promotes TNFα-activated AKT/ERK/NF-κB pathways by binding to PDPN. Finally, the administration of TDG attenuates inflammatory lymphangiogenesis, inhibits osteoclast activity, and reduces condylar bone loss in TNF^TG arthritic mice and forced mouth opening mice.

CONCLUSIONS

Our findings reveal the important role of Gal-8-promoted pathological lymphangiogenesis in inflammation-related condylar bone loss.

Overexpression of galectin2 (LGALS2) predicts a better prognosis in human breast cancer

BACKGROUND

Galectins (LGALS) are a family of carbohydrate-binding proteins, and LGALS family members have shown prognostic roles in various types of cancers. However, the prognostic significance of some LGALS family members has not been studied in breast malignancy.

METHODS

The prognostic value of LGALS family mRNA expression in breast cancer patients was investigated according to distinct clinicopathological features (including lymph node, intrinsic subtype, pathological grade, HER2, and TP53 status) using the Kaplan-Meier plotter database. Quantitative real-time polymerase chain reaction and western blotting were used to detect the mRNA and protein expression of LGALS in breast cancer and normal breast cells. The aberrant expression of specific LGALS and its correlation with breast cancer outcomes remains elusive. In the present analysis, we comprehensively explored an immunohistochemistry-based map of protein expression profiles in normal tissues, cancer, and cell lines from the widely available Human Protein Atlas (HPA) database. Immunohistochemistry was applied to evaluate the expression of LGALS between cancer and normal tissues.

RESULTS

Our results showed that overexpression of LGALS2 mRNA were correlated with satisfactory overall survival among all breast cancer patients. Furthermore, LGALS2 and LGALS4 expression correlated with a better overall survival (OS) in grade III breast cancer patients; LGALS2 also predicted a better OS in basal-like subtype patients, luminal B patients, HER2-overexpressing patients, TP53 mutated and wild breast cancer patients. Notably, the mRNA and protein expression levels of LGALS2 were decreased in cancer cells compared with normal cells (P<0.05). Furthermore, LGALS2 expression in immunostaining score was lower in cancer tissues than in normal tissues (P<0.005).

CONCLUSION

In conclusion, LGALS2 has potential as a valuable biomarker for envisaging a satisfactory prognosis in patients with breast tumours, particularly those with luminal and basal B types, all stages and grade III tumours.

Exosomal miR‑663b exposed to TGF‑β1 promotes cervical cancer metastasis and epithelial‑mesenchymal transition by targeting MGAT3

Transforming growth factor (TGF)‑β1 is a key cytokine affecting the pathogenesis and progression of cervical cancer. Tumor‑derived exosomes contain microRNAs (miRNAs/miRs) that interact with cancer and stromal cells, thereby contributing to tissue remodeling in the tumor microenvironment (TME). The present study was designed to clarify how TGF‑β1 affects tumor biological functions through exosomes released by cervical cancer cells. Deep RNA sequencing found that TGF‑β1 stimulated cervical cancer cells to secrete more miR‑663b‑containing exosomes, which could be transferred into new target cells to promote metastasis. Further studies have shown that miR‑663b directly targets the 3'-untranslated regions (3'‑UTR) of mannoside acetylglucosaminyltransferase 3 (MGAT3) and is involved in the epithelial‑mesenchymal transition (EMT) process. Remarkably, the overexpression of MGAT3 suppressed cervical cancer cell metastasis promoted by exosomal miR‑663b, causing increased expression of epithelial differentiation marker E‑cadherin and decreased expression of mesenchymal markers N‑cadherin and β‑catenin. Throughout our study, online bioinformation tools and dual luciferase reporter assay were applied to identify MGAT3 as a novel direct target of miR‑663b. Exosome PKH67‑labeling experiment verified that exosomal miR‑663b could be endocytosed by cervical cancer cells and subsequently influence its migration and invasion functions which were measured by wound healing and Transwell assays. The expression of miR‑663b and MGAT3 and the regulation of the EMT pathway caused by MGAT3 were detected by quantitative real‑time transcription‑polymerase chain reaction (qPCR) and western blot analysis. These results, thus, provide evidence that cancer cell‑derived exosomal miR‑663b is endocytosed by cervical cancer cells adjacent or distant after TGF‑β1 exposure and inhibits the expression of MGAT3, thereby accelerating the EMT process and ultimately promoting local and distant metastasis.

Potential of MALDI-TOF-based serum N-glycan analysis for the diagnosis and surveillance of breast cancer

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based serum N-glycan analysis has gained acknowledgment for the diagnosis of breast cancer in recent years. In this study, the possibilities of expanding its application for breast cancer management and surveillance were discovered and evaluated. First, a novel MALDI-TOF platform, IDsys RT, was confirmed to be effective for breast cancer analysis, showing a maximum area under the curve of 0.91. Multiple N-glycan markers were identified and validated using this process, and they were found to be applicable for differentiating recurring breast cancer samples from healthy control or ordinary breast cancer samples. Recurrence samples were especially distinct from non-recurrence samples when N-glycan signatures were sampled in multiple time points and monitored via MALDI-TOF, throughout the therapy. These results suggested the feasibility of MALDI-TOF-based N-glycan analysis for tracking the molecular signatures of breast cancer and predicting recurrence.

MGAT3-mediated glycosylation of tetraspanin CD82 at asparagine 157 suppresses ovarian cancer metastasis by inhibiting the integrin signaling pathway

Background: Tetraspanins constitute a family of transmembrane spanning proteins that function mainly by organizing the plasma membrane into micro-domains. CD82, a member of tetraspanins, is a potent inhibitor of cancer metastasis in numerous malignancies. CD82 is a highly glycosylated protein, however, it is still unknown whether and how this post-translational modification affects CD82 function and cancer metastasis.

Methods: The glycosylation of CD82 profiles are checked in the paired human ovarian primary and metastatic cancer tissues. The functional studies on the various glycosylation sites of CD82 are performed in vitro and in vivo.

Results: We demonstrate that CD82 glycosylation at Asn157 is necessary for CD82-mediated inhibition of ovarian cancer cells migration and metastasis in vitro and in vivo. Mechanistically, we discover that CD82 glycosylation is pivotal to disrupt integrin α5β1-mediated cellular adhesion to the abundant extracellular matrix protein fibronectin. Thereby the glycosylated CD82 inhibits the integrin signaling pathway responsible for the induction of the cytoskeleton rearrangements required for cellular migration. Furthermore, we reveal that the glycosyltransferase MGAT3 is responsible for CD82 glycosylation in ovarian cancer cells. Metastatic ovarian cancers express reduced levels of MGAT3 which in turn may result in impaired CD82 glycosylation.

Conclusions: Our work implicates a pathway for ovarian cancers metastasis regulation via MGAT3 mediated glycosylation of tetraspanin CD82 at asparagine 157.

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

Mass spectrometry analysis reveals aberrant N-glycans in colorectal cancer tissues

Aberrant glycosylation is strongly correlated with the development of various cancers. Tumor-associated carbohydrate antigens, including N-glycans, are predominantly expressed on the tumor cell surface. Because the incidence of colorectal cancer is high in China, we investigated aberrant N-glycans from colorectal cancer tissues (CRC) in Chinese patients. By Linear ion trap quadrupole-electrospray ionization mass spectrometry, we performed glycomic assays on N-glycans obtained from solid CRC tissues and paired peritumoral tissues. In total, aberrant N-glycans were expressed in the colorectal tumor tissues. Specifically, seven bisecting structures (M/Z 9732+, 10602+, 10752+, 11622+, 11772+, 12642+, 13522+) decreased, M/Z 10552+ (two-antennae complex N-glycan) and M/Z 12792+ (three-antennae complex N-glycan) decreased, M/Z 10132+ and M/Z 11162+ (high-mannose N-glycan) increased, and M/Z 12282+ (bifucosylated N-glycan) increased. To evaluate the MS profile data, several statistical tools were applied, including student's t test, orthogonal partial least squares discriminant analysis and receiver operating characteristic curve. The measurement of the degree of bisecting N-glycans had an area under the curve value of 0.823. Interestingly, we observed that the bisecting N-glycans decreased with the tumor stages. This phenomenon was not found in esophageal squamous cell carcinoma, in which the bisecting N-glycans had no change. Thus, the expression of bisecting N-glycans may be an interesting point in the study of colorectal cancer.

Comprehensive N-Glycome Profiling of Cells and Tissues for Breast Cancer Diagnosis

Aberrant protein glycosylation is observed in the progression of many types of diseases, including different cancers. In this study, we assess differential N-glycan patterns of human breast cancer cells and tissues by PGC-ESI-MS/MS. Compared with mammary epithelial cells, high-mannose glycans were significantly elevated in breast cancer cells. However, the alteration of N-glycans in tissues was more obvious than that in cells. Sixty-three kinds of different N-glycans were stably identified, and 38 types of them exhibited significant differences between para-carcinoma and breast cancer tissues. High-mannose glycans and core-fucosylated glycans were increased in the breast cancer tissues, while bisected glycans and sialylated glycans were decreased. Moreover, a total of 27 types of N-glycans displayed evident differences between benign breast tumor and breast cancer tissues, and most of them including bisected and sialylated glycans exhibited decreased relative abundances in cancer tissues. Overall, three high-mannose N-glycans (F0H6N2S0, F0H7N2S0, F0H8N2S0) exhibited significant diagnostic accuracy in both breast cancer cells and tissues, suggesting their potential role in biomarkers. Furthermore, a negative correlation between sialylated glycans and age of patients was identified. In conclusion, our results may be beneficial to understand the role that N-glycan plays on the progression of breast cancer and propose potential diagnostic biomarkers.

Bisecting N-Acetylglucosamine Structures Inhibit Hypoxia-Induced Epithelial-Mesenchymal Transition in Breast Cancer Cells

The epithelial-mesenchymal transition (EMT) process plays a key role in many biological processes, including tissue fibrosis, metastatic diseases, and cancer progression. EMT can be induced by certain factors, notably hypoxia, in the tumor microenvironment. Aberrant levels of certain N-glycans is associated with cancer progression. We used an integrated strategy (mass spectrometry in combination with lectin microarray analysis) to elucidate aberrant glycosylation in a hypoxia-induced EMT model using breast cancer cell lines MCF7 and MDA-MB-231. The model showed reduced levels of bisecting GlcNAc structures, and downregulated expression of the corresponding glycosyltransferase MGAT3. MGAT3 overexpression in MCF7 suppressed cell migration, proliferation, colony formation, expression of EMT markers, and AKT signaling pathway, whereas MGAT3 knockdown (shRNA silencing) had opposite effects. Our findings clearly demonstrate the functional role (and effects of dysregulation) of bisecting GlcNAc structures in hypoxia-induced EMT, and provide a useful basis for further detailed studies of physiological functions of these structures in breast cancer.

Hallmarks of glycosylation in cancer

Aberrant glycosylation plays a fundamental role in key pathological steps of tumour development and progression. Glycans have roles in cancer cell signalling, tumour cell dissociation and invasion, cell-matrix interactions, angiogenesis, metastasis and immune modulation. Aberrant glycosylation is often cited as a ‘hallmark of cancer’ but is notably absent from both the original hallmarks of cancer and from the next generation of emerging hallmarks. This review discusses how glycosylation is clearly an enabling characteristic that is causally associated with the acquisition of all the hallmark capabilities. Rather than aberrant glycosylation being itself a hallmark of cancer, another perspective is that glycans play a role in every recognised cancer hallmark.

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.

Mass spectrometry-assisted gel-based proteomics in cancer biomarker discovery: approaches and application

There is a critical need for the discovery of novel biomarkers for early detection and targeted therapy of cancer, a major cause of deaths worldwide. In this respect, proteomic technologies, such as mass spectrometry (MS), enable the identification of pathologically significant proteins in various types of samples. MS is capable of high-throughput profiling of complex biological samples including blood, tissues, urine, milk, and cells. MS-assisted proteomics has contributed to the development of cancer biomarkers that may form the foundation for new clinical tests. It can also aid in elucidating the molecular mechanisms underlying cancer. In this review, we discuss MS principles and instrumentation as well as approaches in MS-based proteomics, which have been employed in the development of potential biomarkers. Furthermore, the challenges in validation of MS biomarkers for their use in clinical practice are also reviewed.

Identification of hub genes and pathways associated with bladder cancer based on co-expression network analysis

The aim of the present study was to identify hub genes and signaling pathways associated with bladder cancer (BC) utilizing centrality analysis and pathway enrichment analysis. The differentially expressed genes (DEGs) were screened from the ArrayExpress database between normal subjects and BC patients. Co-expression networks of BC were constructed using differentially co-expressed genes and links, and hub genes were investigated by degree centrality analysis of co-expression networks in BC. The enriched signaling pathways were investigated by Kyoto Encyclopedia of Genes and Genomes database analysis based on the DEGs. The hub gene expression in BC tissues was validated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. A total of 329 DEGs were screened, including 147 upregulated and 182 downregulated genes. The co-expression network constructed between BC and normal controls consisted of 182 nodes and 434 edges, and the two genes in each gene pair were differentially co-expressed genes. Centrality analysis of co-expression networks suggested that the top 5 hub genes with high degree included lectin, galactoside-binding, soluble, 4 (LGALS4), protein tyrosine phosphatase, receptor type N2 (PTPRN2), transmembrane protease, serine 11E (TMPRSS11E), tripartite motif containing 31 (TRIM31) and potassium voltage-gated channel subfamily D member 3 (KCND3). Pathway analysis revealed that the 329 DEGs were significantly enriched in 5 terms (cell cycle, DNA replication, oocyte meiosis, p53 signaling pathway and peroxisome proliferator-activated receptor signaling pathway). According to RT-qPCR and western blot analysis, 4/5 hub genes were significantly expressed, including LGALS4, PTPRN2, TMPRSS11E, TRIM31; however, KCND3 was not significantly expressed. In the present study, 5 hub genes were successfully identified (LGALS4, PTPRN2, TMPRSS11E, TRIM31 and KCND3) and 5 biological pathways that may be underlying biomarkers for early diagnosis and treatment associated with bladder cancer were revealed.

Galectin signatures contribute to the heterogeneity of breast cancer and provide new prognostic information and therapeutic targets

Because of their ability to induce local immunosuppression and to confer cancer cells with resistance to apoptosis, members of the galectin family are emerging as a new class of actionable targets in cancer. Unfortunately, we have yet to obtain a clear picture of the galectin signatures in cancer cells and the surrounding tumor microenvironment. The aim of this study was to provide the first detailed analysis of the galectin signature in molecular subtypes of breast cancer. Expression signatures of galectins were obtained at the mRNA and protein levels. A particular attention was paid to stromal versus epithelial staining and to subcellular compartmentalization. Analysis of the stromal signature showed that gal-1, -3, -9-positive stroma were preferentially found in triple-negative (TN) and HER2 subtypes. In cancer cells, gal-1, −3, -8, and -9 showed a dual expression pattern, being found either in the cytosol or in the cytosol and the nucleus. TN patients with gal-8-positive nuclei had significantly better disease-free survival (DFS), distant-disease-free survival (DDFS), and overall survival (OS). In contrast, high expression of nuclear gal-1 correlated with poor DDFS and OS. TNBC patients who were positive for both nuclear gal-1 and gal-8 had 5-year DFS and DDFS of 100%, suggesting a dominance of the gal-8 phenotype. Overall, the results indicate that specific galectin expression signatures contribute to the phenotypic heterogeneity of aggressive subtypes of breast cancer. Our data also suggest that galectins have clinical utility as indicators of disease progression and therapeutic targets in aggressive molecular subtypes of breast cancer.

Galectin-7 Expression Potentiates HER-2-Positive Phenotype in Breast Cancer

HER-2 positive tumors are among the most aggressive subtypes of breast cancer and are frequently associated with metastasis and poor outcome. As with other aggressive subtypes of breast cancer, these tumors are associated with abnormally high expression of galectin-7 (gal-7), which confers metastatic breast tumor cells with increased invasive behavior. Although previous studies in the rat model of breast tumorigenesis have shown that gal-7 is also increased in primary breast tumor, its contribution to the development of the primary breast tumors remains unclear. In the present work, we have used genetically-engineered gal-7-deficient mice to examine the role of gal-7 in the development of the mammary gland and of breast cancer. Using histological and immunohistological analysis of whole mammary glands at different stages of development, we detected no significant changes between normal and gal-7-deficient mice. To test the involvement of gal-7 in breast cancer, we next examined the effects of loss of gal-7 on mammary tumor development by crossing gal-7-deficient mice with the mammary tumor transgenic mouse strain FVB-Tg(MMTV-Erbb2)NK1Mul/J. Finally, assessment of mice survival and tumor volume showed a delay of mammary tumor growth in the absence of systemic gal-7. These data suggest that gal-7 could potentiate the phenotype of HER-2 positive primary breast cancer.

Glycosylation-dependent binding of galectin-8 to activated leukocyte cell adhesion molecule (ALCAM/CD166) promotes its surface segregation on breast cancer cells

BACKGROUND

We previously demonstrated that the activated leukocyte cell adhesion molecule (ALCAM/CD166) can interact with galectin-8 (Gal-8) in endothelial cells. ALCAM is a member of the immunoglobulin superfamily that promotes homophilic and heterophilic cell-cell interactions. Gal-8 is a "tandem-repeat"-type galectin, known as a matricellular protein involved in cell adhesion. Here, we analyzed the physical interaction between both molecules in breast cancer cells and the functional relevance of this phenomenon.

METHODS

We performed binding assays by surface plasmon resonance to study the interaction between Gal-8 and the recombinant glycosylated ALCAM ectodomain or endogenous ALCAM from MDA-MB-231 breast cancer cells. We also analyzed the binding of ALCAM-silenced or control breast cancer cells to immobilized Gal-8 by SPR. In internalization assays, we evaluated the influence of Gal-8 on ALCAM surface localization.

RESULTS

We showed that recombinant glycosylated ALCAM and endogenous ALCAM from breast carcinoma cells physically interacted with Gal-8 in a glycosylation-dependent fashion displaying a differential behavior compared to non-glycosylated ALCAM. Moreover, ALCAM-silenced breast cancer cells exhibited reduced binding to Gal-8 relative to control cells. Importantly, exogenously added Gal-8 provoked ALCAM segregation, probably trapping this adhesion molecule at the surface of breast cancer cells.

CONCLUSIONS

Our data indicate that Gal-8 interacts with ALCAM at the surface of breast cancer cells through glycosylation-dependent mechanisms.

GENERAL SIGNIFICANCE

A novel heterophilic interaction between ALCAM and Gal-8 is demonstrated here, suggesting its physiologic relevance in the biology of breast cancer cells.

Serum N-glycan analysis in breast cancer patients--Relation to tumour biology and clinical outcome

Glycosylation and related processes play important roles in cancer development and progression, including metastasis. Several studies have shown that N-glycans have potential diagnostic value as cancer serum biomarkers. We have explored the significance of the abundance of particular serum N-glycan structures as important features of breast tumour biology by studying the serum glycome and tumour transcriptome (mRNA and miRNA) of 104 breast cancer patients. Integration of these types of molecular data allows us to study the relationship between serum glycans and transcripts representing functional pathways, such as metabolic pathways or DNA damage response. We identified tri antennary trigalactosylated trisialylated glycans in serum as being associated with lower levels of tumour transcripts involved in focal adhesion and integrin-mediated cell adhesion. These glycan structures were also linked to poor prognosis in patients with ER negative tumours. High abundance of simple monoantennary glycan structures were associated with increased survival, particularly in the basal-like subgroup. The presence of circulating tumour cells was found to be significantly associated with several serum glycome structures like bi and triantennary, di- and trigalactosylated, di- and trisialylated. The link between tumour miRNA expression levels and N-glycan production is also examined.

Galectin expression in cancer diagnosis and prognosis: A systematic review

Galectins are a family of proteins that bind to specific glycans thereby deciphering the information captured within the glycome. In the last two decades, several galectin family members have emerged as versatile modulators of tumor progression. This has initiated the development and preclinical assessment of galectin-targeting compounds. With the first compounds now entering clinical trials it is pivotal to gain insight in the diagnostic and prognostic value of galectins in cancer as this will allow a more rational selection of the patients that might benefit most from galectin-targeted therapies. Here, we present a systematic review of galectin expression in human cancer patients. Malignant transformation is frequently associated with altered galectin expression, most notably of galectin-1 and galectin-3. In most cancers, increased galectin-1 expression is associated with poor prognosis while elevated galectin-9 expression is emerging as a marker of favorable disease outcome. The prognostic value of galectin-3 appears to be tumor type dependent and the other galectins require further investigation. Regarding the latter, additional studies using larger patient cohorts are essential to fully unravel the diagnostic and prognostic value of galectin expression. Furthermore, to better compare different findings, consensus should be reached on how to assess galectin expression, not only with regard to localization within the tissue and within cellular compartments but also regarding alternative splicing and genomic variations. Finally, linking galectin expression and function to aberrant glycosylation in cancer cells will improve our understanding of how these versatile proteins can be exploited for diagnostic, prognostic and even therapeutic purposes in cancer patients.

Alteration of N-glycans and expression of their related glycogenes in the epithelial-mesenchymal transition of HCV29 bladder epithelial cells

The epithelial-mesenchymal transition (EMT) is an essential step in the proliferation and metastasis of solid tumor cells, and glycosylation plays a crucial role in the EMT process. Certain aberrant glycans have been reported as biomarkers during bladder cancer progression, but global variation of N-glycans in this type of cancer has not been previously studied. We examined the profiles of N-glycan and glycogene expression in transforming growth factor-beta (TGFβ)-induced EMT using non-malignant bladder transitional epithelium HCV29 cells. These expression profiles were analyzed by mass spectrometry, lectin microarray analysis, and GlycoV4 oligonucleotide microarray analysis, and confirmed by lectin histochemistry and real-time RT-PCR. The expression of 5 N-glycan-related genes were notably altered in TGFβ-induced EMT. In particular, reduced expression of glycogene man2a1, which encodes α-mannosidase 2, contributed to the decreased proportions of bi-, tri- and tetra-antennary complex N-glycans, and increased expression of hybrid-type N-glycans. Decreased expression of fuca1 gene, which encodes Type 1 α-L-fucosidase, contributed to increased expression of fucosylated N-glycans in TGFβ-induced EMT. Taken together, these findings clearly demonstrate the involvement of aberrant N-glycan synthesis in EMT in these cells. Integrated glycomic techniques as described here will facilitate discovery of glycan markers and development of novel diagnostic and therapeutic approaches to bladder cancer.

Enhancing MS(n) mass spectrometry strategy for carbohydrate analysis: A b2 ion spectral library

Searchable mass spectral libraries for glycans may be enhanced using a B2 ion library. Using a quadrupole ion-trap mass spectrometer, successive fragmentations of sodiated oligosaccharides were carried out in the positive ion mode. In B,Y-type fragmentation, disaccharide B2 ions are generated which correspond to specific glycosidic linkages using progressive MS stages. Fragmentation of "B2 ions" corresponding to glycosidic linkages such as Hex-Fuc, Hex-Hex, Hex-HexNAc, HexNAc-Hex and HexNAc-HexNAc, were systematically studied in low energy CID and collected to form a "B2 library". Linkages produce characteristic fragmentation patterns in the absence of cross-ring fragmentation. Patterns of "B2 ions" rely on relative stability of glycosidic bonds and carbohydrate-metal complexes in the gas phase. MS(n) studies of linear, branched trisaccharides and tetrasaccharides show that isomers for which B2 ion information is not available are rarely a problem in practice by their absence in an isomeric sequence or by their scarcity in nature. This MS strategy for linkage determination of carbohydrates aided by a "B2 library" was developed with a scope for expansion, providing an improved tool for glycomics. We validated this method examining levels of expressed activities of two glycosyl transferases in cancer cell lines: β3(B3GALNT2) and β4GalNAcT(B4GALNT3&4) that generate GalNAcβ3GlcNAcβ and GalNAcβ4GlcNAcβ.

BIOLOGICAL SIGNIFICANCE

Glycosylation is an important class of the "postranslationome", which includes manifold aspects of post-translational protein modification, affecting protein conformation, providing ligands for protein receptors [1-5], and encoding unique haptenic [6,7] or antigenic markers for oncology [8-11] and other applications. Identification of individual monomeric units, linkages, ring size, branching and anomerity has posed significant challenges to mass spectrometrists. MS(n) is a growing key instrumental method to differentiate among isomers [12]. While the potential isomers in oligosaccharides are impossibly large [12], likely possibilities can be limited by the biological system, including the expressed glycosyl transferases [13-20]. Mass spectra from sequential stages of collision activation (MS(n)) can supply structural details for precise characterization of linkage, monomer ID, substitutions, anomerity and branching [21-25]. There is a fundamental need for high throughput tools in glycomics to complement proteome studies. In that regard, nothing could be more important than searchable spectral library files for structural confirmation. The National Academy of Science (NAS) report (http://glyco.nas.edu) recommends the need of more than 10,000 synthetic structures of carbohydrates to advance the field of glycomics. This study demonstrates that the general reproducibility of ion trap spectra, and energy independence from modes of ionization and collisional activation, make compiling an MS(n) library for carbohydrate identification an achievable research target [26]. We intend to use the new B2 library for carbohydrate differences found on cancers, where we profile the glycosyltransferases to predict classes of potential structures, and use the library for MS identification of the expected cohort of altered structures.

Decreased core-fucosylation contributes to malignancy in gastric cancer

The object of the study is to identify N-glycan profiling changes associated with gastric cancer and explore the impact of core-fucosylation on biological behaviors of human gastric cancer cells. A total of 244 subjects including gastric cancer, gastric ulcer and healthy control were recruited. N-glycan profiling from serum and total proteins in gastric tissues was analyzed by DNA sequencer-assisted fluorophore-assisted capillary electrophoresis. The abundance of total core-fucosylated residues and the expression of enzymes involved in core-fucosylation were analyzed with lectin blot, quantitative reverse transcription-polymerase chain reaction, western blot, Immunohistochemical staining and lectin-histochemical staining. The recombinant plasmids of GDP-fucose transporter and α-1,6-fucosyltransferase (Fut8) were constructed and transfected into gastric cancer cell lines BGC-823 and SGC-7901. CCK-8 and wound healing assay were used to assess the functional impact of core-fucosylation modulation on cell proliferation and migration. Characteristic serum N-glycan profiles were found in gastric cancer. Compared with the healthy control, a trianntenary structure abundance, peak 9 (NA3Fb), was increased significantly in gastric cancer, while the total abundance of core-fucosylated residues (sumfuc) was decreased. Core-fucosylated structures, peak6(NA2F) and peak7(NA2FB) were deceased in gastric tumor tissues when compared with that in adjacent non-tumor tissues. Consistently, lens culinaris agglutinin (LCA)-binding proteins were decreased significantly in sera of gastric cancer, and protein level of Fut8 was decreased significantly in gastric tumor tissues compared with that in adjacent non-tumor tissues. Upregulation of GDP-Tr and Fut8 could inhibit proliferation, but had no significant influence on migration of BGC-823 and SGC-7901 cells. Core-fucosylation is down regulated in gastric cancer. Upregulation of core-fucosylation could inhibit proliferation of the human gastric cancer cells.