Correlation analysis between tumor-associated antigen sialyl-Tn expression and ST6GalNAc I activity in human colon adenocarcinoma

CDX2 homeoprotein is involved in the regulation of ST6GalNAc-I gene in intestinal metaplasia

De novo expression of Sialyl-Tn (STn) antigen is one of the most common features of intestinal metaplasia (IM) and gastric carcinomas, and its biosynthesis has been mostly attributed to ST6GalNAc-I activity. However, the regulation of this glycosyltransferase expression is not elucidated. In IM lesions and in the intestine, CDX2 homeobox transcription factor is co-expressed with STn and ST6GalNAc-I. We therefore hypothesized that CDX2 might induce STn expression by positive regulation of ST6GalNAc-I. We showed that ST6GalNAc-I transcript levels and CDX2 have a coordinated expression upon Caco-2 in vitro differentiation, and overexpression of CDX2 in MKN45 gastric cells increases ST6GalNAc-I transcript levels. Nine putative CDX-binding sites in the ST6GalNAc-I-regulatory sequence were identified and analyzed by chromatin immunoprecipitation in Caco-2 cells and in IM. The results showed that CDX2 protein is recruited to all regions, being the most proximal sites preferentially occupied in vivo. Luciferase assays demonstrated that CDX2 is able to transactivate ST6GalNac-I-regulatory region. The induction was stronger for the regions mapped in the neighbourhood of ATG start codon and site-directed mutagenesis of these sites confirmed their importance. In conclusion, we show that CDX2 transcriptionally regulates ST6GalNAc-I gene expression, specifically in the preneoplastic IM lesion.

Significance of β-Galactoside α2,6 Sialyltranferase 1 in Cancers

Altered glycosylation is a common feature of cancer cells. It takes a variety of forms, which includes loss of expression or excessive expression of some structures, the accumulation of precursors, the appearance of novel structures, etc. Notably, these changes in glycan structure do not occur as a random consequence of disorder biology. Only a limited subset of oligosaccharides is found frequently enriched on the tumor cell surface and implicated in different tumor phenotypes. Among these, altered sialylation has long been associated with metastatic cell behaviors such as invasion and enhanced cell survival and accumulating evidence points to the alteration occurring in the sialic acid linkage to other sugars, which normally exists in three main configurations: α2,3, α2,6, and α2,8, catalyzed by a group of sialyltransferases. The aberrant expression of all three configurations has been described in cancer progression. However, the increased α2,6 sialylation catalyzed by β-galactoside α2,6 sialyltranferase 1 (ST6Gal I) is frequently observed in many types of the cancers. In this review, we describe the findings on the role of ST6Gal I in cancer progression, and highlight in particular the knowledge of how ST6Gal I-mediated α2,6 sialylated glycans or sialylated carrier proteins regulate cell signaling to promote the malignant phenotype of human carcinoma.

Simple sugars to complex disease--mucin-type O-glycans in cancer

Mucin-type O-glycans are a class of glycans initiated with N-acetylgalactosamine (GalNAc) α-linked primarily to Ser/Thr residues within glycoproteins and often extended or branched by sugars or saccharides. Most secretory and membrane-bound proteins receive this modification, which is important in regulating many biological processes. Alterations in mucin-type O-glycans have been described across tumor types and include expression of relatively small-sized, truncated O-glycans and altered terminal structures, both of which are associated with patient prognosis. New discoveries in the identity and expression of tumor-associated O-glycans are providing new avenues for tumor detection and treatment. This chapter describes mucin-type O-glycan biosynthesis, altered mucin-type O-glycans in primary tumors, including mechanisms for structural changes and contributions to the tumor phenotype, and clinical approaches to detect and target altered O-glycans for cancer treatment and management.

The Cosmc connection to the Tn antigen in cancer

The Tn antigen is a tumor-associated carbohydrate antigen that is not normally expressed in peripheral tissues or blood cells. Expression of this antigen, which is found in a majority of human carcinomas of all types, arises from a blockage in the normal O-glycosylation pathway in which glycans are extended from the common precursor GalNAcα1-O-Ser/Thr (Tn antigen). This precursor is generated in the Golgi apparatus on newly synthesized glycoproteins by a family of polypeptide α-N-acetylgalactosaminyltransferases (ppGalNAcTs) and then extended to the common core 1 O-glycan Galβ1-3GalNAcα1-O-Ser/Thr (T antigen) by a single enzyme termed the T-synthase (core 1 β3-galactosyltransferase or C1GalT). Formation of the active form of the T-synthase requires a unique molecular chaperone termed Cosmc, encoded by Cosmc on the X-chromosome (Xq24 in humans, Xc3 in mice). Cosmc resides in the endoplasmic reticulum (ER) and prevents misfolding, aggregation, and proteasome-dependent degradation of newly synthesized T-synthase. Loss of expression of active T-synthase or Cosmc can lead to expression of the Tn antigen, along with its sialylated version Sialyl Tn antigen as observed in several cancers. Both genetic and epigenetic pathways, in addition to potential metabolic regulation, can result in abnormal expression of the Tn antigen. Engineered expression of the Tn antigen by disruption of either C1GalT (T-syn) or Cosmc in mice is associated with a tremendous range of pathologies and engineered expression of the Tn antigen in mouse embryos leads to embryonic death. Studies indicate that many membrane glycoproteins expressing the Tn antigen and/or truncated O-glycans may be dysfunctional, due to degradation and/or misfolding. Thus, expression of normal O-glycans is associated with health and homeostasis whereas truncation of O-glycans, e.g. the Tn and/or Sialyl Tn antigens is associated with cancer and other pathologies.

A cancer therapeutic vaccine based on clustered Tn-antigen mimetics induces strong antibody-mediated protective immunity

Tumor-associated carbohydrate antigens (TACAs) are key components of cancer vaccines. A variety of vaccines based on native TACAs such as α-Tn have shown immunogenicity and protection in preclinical animal studies, however, their weak immunogenicity, low in vivo instability, and poor bioavailability, have discouraged their further evaluations in clinical studies. A new improved vaccine prototype is reported. It is composed of four clustered Tn-antigen mimetics and a immunogenic peptide epitope that are conjugated to a cyclopeptide carrier. The immunization of mice with this vaccine 1) was safe, 2) induced a strong and long-lasting Tn-specific response with IgM/IgG antibodies able to recognize native carbohydrate antigens; 3) produced high titers of IgG1, IgG2a, and IgG3 antibodies; and 4) produced a significant antibody-dependent regression of tumors and conferred protection. Altogether, these findings pave the way for the clinical development of safe and effective therapeutic vaccines against Tn-expressing cancers.

Expression of leukocyte adhesion-related glycosyltransferase genes in acute coronary syndrome patients

INTRODUCTION

Acute coronary syndrome (ACS) is caused by destabilization and rupture of atherosclerotic plaque in the coronary artery via mechanisms affecting leukocyte signaling, rolling, adhesion, extravasation and inflammation-promoting factors. The majority of cellular communication takes place on the membrane surface that is covered with glycoproteins and glycolipids synthesized by glycosyltransferases. The aim of this study was to determine the mRNA expression of leukocyte adhesion-related glycosyltransferases in patients during the onset and the chronic phase of ACS and to compare the expression with matching subjects without coronary disease.

SUBJECTS AND METHODS

The study included 26 ACS patients and 26 ACS-free matched-pair controls. Blood samples were collected at the time of hospital admittance and 8 days later. Expression analysis of six fucosyltransferases and six sialyltransferases was performed by a real-time polymerase chain reaction.

RESULTS

At the time of admittance ACS subjects had lower expression levels of FUT4, ST6GalNac4, ST6Gal1 and GM3 synthase (p < 0.05) than the control subjects, and moreover, after 8 days down-regulation of FUT7 and ST6GalNac3 was also observed (p < 0.05). When compared to the initial gene expression, after treatment and stabilization of ACS subjects, FUT7, ST6GalNac2 and ST6GalNac3 were down-regulated, whereas ST6GalNac1 was up-regulated. Expression levels of FUT7, ST6GalNac1, ST6GalNac2 and ST6GalNac3 were predicted by several drugs and medical history.

CONCLUSION

Expression of glycosyltransferase genes differs in ACS and control subjects. During the course of the ACS study we established further changes in gene expression levels. Medical history was predictive of gene expression levels while drugs were shown to modulate expression levels.

Reciprocal relationship of Tn/NF-κB and sTn as an indicator of the prognosis of oral squamous cell carcinoma

AIMS

In order to determine whether the expression of tumour-associated carbohydrate antigens (Tn/sTn) and a representative inflammation marker, nuclear factor-κB (NF-κB), is associated with the invasiveness of oral squamous cell carcinoma (OSCC), this study has attempted to investigate the correlation of the aforementioned markers with the well-established invasive pattern grading score (IPGS) and clinicopathological parameters.

METHODS AND RESULTS

Specimens from 143 OSCC patients with classified clinicopathological parameters and IPGS were stained immunohistochemically using anti-Tn, sTn and NF-κB antibodies. Our results showed that the expression of both Tn and NF-κB was correlated positively with staging (P = 0.036; P = 0.015), recurrence (P < 0.001; P < 0.001) and distant metastasis (P = 0.005; P = 0.009), as well as with IPGS, while the expression of sTn was correlated inversely. In addition, poor survival was associated with overexpression of Tn and NF-κB but not with expression of sTn.

CONCLUSIONS

Our results indicate that a reciprocal relationship between Tn and sTn expression may serve as a reliable indicator for OSCC prognostic evaluation. In addition, expression of Tn rather than sTn may play an important role in deeply invasive OSCC via regulation of NF-κB signalling.

Overexpression of tumour-associated carbohydrate antigen sialyl-Tn in advanced bladder tumours

Little is known on the expression of the tumour-associated carbohydrate antigen sialyl-Tn (STn), in bladder cancer. We report here that 75% of the high-grade bladder tumours, presenting elevated proliferation rates and high risk of recurrence/progression expressed STn. However, it was mainly found in non-proliferative areas of the tumour, namely in cells invading the basal and muscle layers. STn was also found in tumour-adjacent mucosa, which suggests its dependence on a field effect of the tumour. Furthermore, it was not expressed by the normal urothelium, demonstrating the cancer-specific nature of this antigen. STn expression correlated with that of sialyltransferase ST6GalNAc.I, its major biosynthetic enzyme. The stable expression of ST6GalNAc.I in the bladder cancer cell line MCR induced STn expression and a concomitant increase of cell motility and invasive capability. Altogether, these results indicate for the first time a link between STn expression and malignancy in bladder cancer. Hence, therapies targeting STn may constitute new treatment approaches for these tumours.

Overview of molecular pathways in inflammatory bowel disease associated with colorectal cancer development

Patients with long-standing inflammatory bowel disease (IBD) are at a higher risk of developing colorectal cancer (CRC). This risk increases with the longer duration of colitis, greater extent of inflammation, a family history of CRC, severity of bowel inflammation, and a coexistent primary sclerosing cholangitis. The cornerstone for comprehending the development of CRC in IBD and hence early detection is based on the understanding of the molecular pathways of IBD itself. At a molecular level, the pathogenesis of CRC is related to understanding the inflammatory changes and involves multiple inter-related pathways including (i) genetic alterations (e.g. chromosomal and microsatellite instability and hypermethylation), (ii) mucosal inflammatory mediators (e.g. COX-2, interleukin-6, interleukin-23, tumor necrosis factor-α, nuclear factor-κB, and chemokines), (iii) changes in the expression of receptors on the epithelial cells, and (iv) oxidant stress, mucosal breakdown, and intestinal microbiota. The aim of this review is to provide an evidence-based approach for the role of chronic inflammatory mechanisms and the molecular basis of these mechanisms in the development of CRC. Therefore, understanding the molecular basis of CRC is an important step for the identification of new biomarkers that can help in the early detection of CRC in these patients.

Tumor-associated glycans and their role in gynecological cancers: accelerating translational research by novel high-throughput approaches

Glycans are important partners in many biological processes, including carcinogenesis. The rapidly developing field of functional glycomics becomes one of the frontiers of biology and biomedicine. Aberrant glycosylation of proteins and lipids occurs commonly during malignant transformation and leads to the expression of specific tumor-associated glycans. The appearance of aberrant glycans on carcinoma cells is typically associated with grade, invasion, metastasis and overall poor prognosis. Cancer-associated carbohydrates are mostly located on the surface of cancer cells and are therefore potential diagnostic biomarkers. Currently, there is increasing interest in cancer-associated aberrant glycosylation, with growing numbers of characteristic cancer targets being detected every day. Breast and ovarian cancer are the most common and lethal malignancies in women, respectively, and potential glycan biomarkers hold promise for early detection and targeted therapies. However, the acceleration of research and comprehensive multi-target investigation of cancer-specific glycans could only be successfully achieved with the help of a combination of novel high-throughput glycomic approaches.

Transmembrane mucins as novel therapeutic targets

Membrane-tethered mucin glycoproteins are abundantly expressed at the apical surfaces of simple epithelia, where they play important roles in lubricating and protecting tissues from pathogens and enzymatic attack. Notable examples of these mucins are MUC1, MUC4 and MUC16 (also known as cancer antigen 125). In adenocarcinomas, apical mucin restriction is lost and overall expression is often highly increased. High-level mucin expression protects tumors from killing by the host immune system, as well as by chemotherapeutic agents, and affords protection from apoptosis. Mucin expression can increase as the result of gene duplication and/or in response to hormones, cytokines and growth factors prevalent in the tumor milieu. Rises in the normally low levels of mucin fragments in serum have been used as markers of disease, such as tumor burden, for many years. Currently, several approaches are being examined that target mucins for immunization or nanomedicine using mucin-specific antibodies.

Disease-free survival of colorectal cancer patients in relation to CDw75 antigen expression

OBJECTIVE

CDw75 is an α(2,6)-sialylated antigen associated with a poor prognosis in gastric cancer. In the present study, we examined if CDw75 expression in colorectal cancer (CRC) predicts tumour recurrence. Besides, we evaluated CDw75 expression in different colorectal tissue specimens to clarify their role in tumour development and progression.

METHODS

We analyzed CDw75 expression in 34 specimens of healthy disease-free colorectal mucosa, 19 specimens of inflammatory colorectal mucosa, 73 colorectal adenomas, 35 specimens of healthy tissue and 101 specimens of tumoural tissue from CRC patients.

RESULTS

None of the healthy disease-free and inflammatory colorectal mucosa specimens showed the presence of the epitope. CDw75 was expressed in 26% of the colorectal adenomas. In healthy and tumoural tissue from CRC patients, CDw75 was detected in 22.9% and 82.2% of the specimens, respectively. CDw75 expression in tumoural tissue was correlated with growth pattern (p = 0.044), Dukes stage (p = 0.002), TNM stage (p = 0.020) and distant metastasis (p = 0.005). Survival analysis showed that CDw75 expression is not associated with tumour recurrence.

CONCLUSION

CDw75 expression in CRC is not a prognostic factor for predicting disease-free survival. Nevertheless, CDw75 expression may be a good marker of tumour progression and of the malignant potential of CRC.

Linear and branched glyco-lipopeptide vaccines follow distinct cross-presentation pathways and generate different magnitudes of antitumor immunity

BACKGROUND

Glyco-lipopeptides, a form of lipid-tailed glyco-peptide, are currently under intense investigation as B- and T-cell based vaccine immunotherapy for many cancers. However, the cellular and molecular mechanisms of glyco-lipopeptides (GLPs) immunogenicity and the position of the lipid moiety on immunogenicity and protective efficacy of GLPs remain to be determined.

METHODS/PRINCIPAL FINDINGS

We have constructed two structural analogues of HER-2 glyco-lipopeptide (HER-GLP) by synthesizing a chimeric peptide made of one universal CD4(+) epitope (PADRE) and one HER-2 CD8(+) T-cell epitope (HER(420-429)). The C-terminal end of the resulting CD4-CD8 chimeric peptide was coupled to a tumor carbohydrate B-cell epitope, based on a regioselectively addressable functionalized templates (RAFT), made of four alpha-GalNAc molecules. The resulting HER glyco-peptide (HER-GP) was then linked to a palmitic acid moiety, attached either at the N-terminal end (linear HER-GLP-1) or in the middle between the CD4+ and CD8+ T cell epitopes (branched HER-GLP-2). We have investigated the uptake, processing and cross-presentation pathways of the two HER-GLP vaccine constructs, and assessed whether the position of linkage of the lipid moiety would affect the B- and T-cell immunogenicity and protective efficacy. Immunization of mice revealed that the linear HER-GLP-1 induced a stronger and longer lasting HER(420-429)-specific IFN-gamma producing CD8(+) T cell response, while the branched HER-GLP-2 induced a stronger tumor-specific IgG response. The linear HER-GLP-1 was taken up easily by dendritic cells (DCs), induced stronger DCs maturation and produced a potent TLR- 2-dependent T-cell activation. The linear and branched HER-GLP molecules appeared to follow two different cross-presentation pathways. While regression of established tumors was induced by both linear HER-GLP-1 and branched HER-GLP-2, the inhibition of tumor growth was significantly higher in HER-GLP-1 immunized mice (p<0.005).

SIGNIFICANCE

These findings have important implications for the development of effective GLP based immunotherapeutic strategies against cancers.

Human tumor antigens Tn and sialyl Tn arise from mutations in Cosmc

Neoplastic lesions typically express specific carbohydrate antigens on glycolipids, mucins, and other glycoproteins. Such antigens are often under epigenetic control and are subject to reversion and loss upon therapeutic selective pressure. We report here that two of the most common tumor-associated carbohydrate antigens, Tn and sialyl Tn (STn), result from somatic mutations in the gene Cosmc that encodes a molecular chaperone required for formation of the active T-synthase. Diverse neoplastic lesions, including colon cancer and melanoma-derived cells lines, expressed both Tn and STn antigen due to loss-of-function mutations in Cosmc. In addition, two human cervical cancer specimens that showed expression of the Tn/STn antigens were also found to have mutations in Cosmc and loss of heterozygosity for the cross-linked Cosmc locus. This is the first example of somatic mutations in multiple types of cancers that cause global alterations in cell surface carbohydrate antigen expression.

The ST6GalNAc-I sialyltransferase localizes throughout the Golgi and is responsible for the synthesis of the tumor-associated sialyl-Tn O-glycan in human breast cancer

The functional properties of glycoproteins are strongly influenced by their profile of glycosylation, and changes in this profile are seen in malignancy. In mucin-type O-linked glycosylation these changes can result in the production of mucins such as MUC1, carrying shorter sialylated O-glycans, and with different site occupancy. Of the tumor-associated sialylated O-glycans, the disaccharide, sialyl-Tn (sialic acid alpha2,6GalNAc), is expressed by 30% of breast carcinomas and is the most tumor-specific. The ST6GalNAc-I glycosyltransferase, which can catalyze the transfer of sialic acid to GalNAc, shows a highly restricted pattern of expression in normal adult tissues, being largely limited to the gastrointestinal tract and absent in mammary gland. In breast carcinomas, however, a complete correlation between the expression of RNA-encoding ST6GalNAc-I and the expression of sialyl-Tn is evident, demonstrating that the expression of sialyl-Tn results from switching on expression of hST6GalNAc-I. Endogenous or exogenous expression of hST6GalNAc-I (but not ST6GalNAc-II) always results in the expression of sialyl-Tn. This ability to override core 1/core 2 pathways of O- linked glycosylation is explained by the localization of ST6GalNAc-I, which is found throughout the Golgi stacks. The development of a Chinese hamster ovary (CHO) cell line expressing MUC1 and ST6GalNAc-I allowed the large scale production of MUC1 carrying 83% sialyl-Tn O-glycans. The presence of ST6GalNAc-I in the CHO cells reduced the number of O-glycosylation sites occupied in MUC1, from an average of 4.3 to 3.8 per tandem repeat. The availability of large quantities of this MUC1 glycoform will allow the evaluation of its efficacy as an immunogen for immunotherapy of MUC1/STn-expressing tumors.