Significance of carbohydrate antigen sialyl-Lewis X, sialyl-Lewis A, and possible unknown ligands to adhesion of human urothelial cancer cells to activated endothelium

Pathophysiological roles and applications of glycosphingolipids in the diagnosis and treatment of cancer diseases

Glycosphingolipids (GSLs) are major amphiphilic glycolipids present on the surface of living cell membranes. They have important biological functions, including maintaining plasma membrane stability, regulating signal transduction, and mediating cell recognition and adhesion. Specific GSLs and related enzymes are abnormally expressed in many cancer diseases and affect the malignant characteristics of tumors. The regulatory roles of GSLs in signaling pathways suggest that they are involved in tumor pathogenesis. GSLs have therefore been widely studied as diagnostic markers of cancer diseases and important targets of immunotherapy. This review describes the tumor-related biological functions of GSLs and systematically introduces recent progress in using diverse GSLs and related enzymes to diagnose and treat tumor diseases. Development of drugs and biomarkers for personalized cancer therapy based on GSL structure is also discussed. These advances, combined with recent progress in the preparation of GSLs derivatives through synthetic biology technologies, suggest a strong future for the use of customized GSL libraries in treating human diseases.

Glycosylation: Rising Potential for Prostate Cancer Evaluation

Simple Summary

Aberrant protein glycosylation is a well-known hallmark of cancer and is associated with differential expression of enzymes such as glycosyltransferases and glycosidases. The altered expression of the enzymes triggers cancer cells to produce glycoproteins with specific cancer-related aberrations in glycan structures. Increasing number of data indicate that glycosylation patterns of PSA and other prostate-originated proteins exert a potential to distinguish between benign prostate disease and cancer as well as among different stages of prostate cancer development and aggressiveness. This review summarizes the alterations in glycan sialylation, fucosylation, truncated O-glycans, and LacdiNAc groups outlining their potential applications in non-invasive diagnostic procedures of prostate diseases. Further research is desired to develop more general algorithms exploiting glycobiology data for the improvement of prostate diseases evaluation.

Abstract

Prostate cancer is the second most commonly diagnosed cancer among men. Alterations in protein glycosylation are confirmed to be a reliable hallmark of cancer. Prostate-specific antigen is the biomarker that is used most frequently for prostate cancer detection, although its lack of sensitivity and specificity results in many unnecessary biopsies. A wide range of glycosylation alterations in prostate cancer cells, including increased sialylation and fucosylation, can modify protein function and play a crucial role in many important biological processes in cancer, including cell signalling, adhesion, migration, and cellular metabolism. In this review, we summarize studies evaluating the prostate cancer associated glycosylation related alterations in sialylation, mainly α2,3-sialylation, core fucosylation, branched N-glycans, LacdiNAc group and presence of truncated O-glycans (sTn, sT antigen). Finally, we discuss the great potential to make use of glycans as diagnostic and prognostic biomarkers for prostate cancer.

Branched I antigen regulated cell susceptibility against natural killer cytotoxicity through its N-linked glycosylation and overall expression

Cell surface glycosylation has been known as an important modification process that can be targeted and manipulated by malignant cells to escape from host immunosurveillance. We previously showed that the blood group branched I antigen on the leukemia cell surface can regulate the cell susceptibility against natural killer (NK) cell-mediated cytotoxicity through interfering target-NK interaction. In this work, we first identified N-linkage as the major glycosylation linkage type for branched I glycan formation on leukemia cells, and this linkage was responsible for cell sensitivity against therapeutic NK-92MI targeting. Secondly, by examining different leukemia cell surface death receptors, we showed death receptor Fas had highest expressions in both Raji and TF-1a cells. Mutations on two Fas extracellular N-linkage sites (118 and 136) for glycosylation impaired activation of Fas-mediated apoptosis during NK-92MI cytotoxicity. Last, we found that the surface I antigen expression levels enable leukemia cells to respond differently against NK-92MI targeting. In low I antigen expressing K-562 cell, reduction of I antigen presence greatly reduced leukemia cell susceptibility against NK-92MI targeting. But in other high I antigen expressing leukemia cells, similar reduction in I antigen expression did not affect cell susceptibility.

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.

Expression of bladder cancer-associated glycans in murine tumor cell lines

The characterization of murine cell lines is of great importance in order to identify preclinical models that could resemble human diseases. Aberrant glycosylation includes the loss, excessive or novel expression of glycans and the appearance of truncated structures. MB49 and MB49-I are currently the only two murine cell lines available for the development of preclinical bladder cancer models. The glycans Lewis X (LeX), Sialyl lewis X (SLeX) and Sialyl Tn (STn) have previously been associated with aggressiveness, dissemination and poor prognosis in human bladder cancer, additionally N-glycolyl GM3 (NGcGM3) is a neo-antigen expressed in many types of tumors; however, to the best of our knowledge, its expression has not previously been assessed in this type of cancer. Taking into account the relevance of glycans in tumor biology and considering that they can act as targets of therapies and biomarkers, the present study evaluated the expression of LeX, SLeX, STn and NGcGM3 in MB49 and MB49-I cells, in different growth conditions such as monolayer cultures, three-dimensional multicellular spheroids and mouse heterotopic and orthotopic tumors. The expression of LeX was not detected in either cell line, whereas SLeX was expressed in monolayers, spheroids and orthotopic tumors of both cell lines. STn was only identified in MB49 monolayers and spheroids. There are no reports concerning the expression of NGcGM3 in human or murine bladder cancer. In our hands, MB49 and MB49-I expressed this ganglioside in all the growth conditions evaluated. The assessment of its expression in cancer cell lines and patient tumors is of great importance, considering the relevance of this ganglioside in tumor biology. The data obtained by the present study demonstrates that glycan expression may be substantially altered depending on the growth conditions, highlighting the importance of the characterization of murine cancer models. To the best of our knowledge, the present study is the first to examine the expression of cancer-associated glycans, in the two murine cell lines available for the development of preclinical studies in bladder cancer.

Clinicopathological implications to micropapillary bladder urothelial carcinoma of the presence of sialyl Lewis X-decorated mucin 1 in stroma-facing membranes

OBJECTIVES

Bladder urothelial carcinoma (UC) comprises more than 90% of all bladder cancers. Among several UC variants, micropapillary UC (MPUC) is a rare one with high potential for lymphovascular invasion and subsequent lymph node metastasis. Histologically, MPUC is characterized by the presence of small papillary carcinoma cell clusters surrounded by lacunar spaces. Immunohistochemically, the outer circumference of these clusters, that is, the stroma-facing membrane of carcinoma cells, is reportedly almost invariably positive for mucin 1 (MUC1) protein and to a lesser extent for sialyl Lewis X (sLeX) carbohydrates; however, the clinicopathological implications of these expression patterns have not been fully investigated.

MATERIALS AND METHODS

We performed immunohistochemical analysis of MPUC (n = 11) and conventional UC (n = 57) for MUC1 and sLeX to determine whether these factors immunolocalized. Dual immunofluorescence staining was also carried out to assess MUC1 and sLeX colocalization. We also performed Western blot analysis of Chinese hamster ovary cells misexpressing both recombinant epitope-tagged MUC1 and glycosyltransferases enabling sLeX biosynthesis.

RESULTS

MPUC samples preferentially exhibited both MUC1 protein and sLeX carbohydrate expression on the stroma-facing membrane of carcinoma cells. Based on univariate analysis, MUC1 expression in that pattern was positively correlated with tumor extension, lymphovascular invasion, lymph node metastasis, disease stage, and relatively poor patient prognosis. A comparable sLeX expression pattern also correlated positively with tumor extension and nodal metastasis. Based on multivariate analysis, localization of MUC1 and sLeX on the stroma-facing side of the membrane was positively correlated with lymph node metastasis.

CONCLUSIONS

Overall, our immunofluorescence findings as well as immunoprecipitation analyses of Chinese hamster ovary cell transfectants strongly suggest that MUC1 is a potential scaffold protein for sLeX carbohydrates in MPUC. Both MUC1 and sLeX may cooperatively contribute to MPUC histogenesis and clinicopathological characteristics.

A potential role for 6-sulfo sialyl Lewis X in metastasis of bladder urothelial carcinoma

OBJECTIVES

It is widely accepted that sialyl Lewis X (sLeX) and sialyl Lewis A (sLeA, also known as CA 19-9) glycans expressed on cancer cells function in E-selectin-mediated metastasis. Recently, it was reported that 6-sulfo sLeX glycans detected by the MECA-79 monoclonal antibody are expressed in roughly a quarter of gastric adenocarcinoma cases, and that these cases show a poorer prognosis than MECA-79-negative cases do. The present study was undertaken to assess expression of 6-sulfo sLeX glycans in bladder urothelial carcinoma and evaluate potential clinical implications.

MATERIALS AND METHODS

We analyzed 78 specimens representing bladder urothelial carcinoma, as well as 4 bladder urothelial carcinoma cell lines, by immunostaining with a battery of anticarbohydrate antibodies. We also undertook an E-selectin·IgM chimera binding assay to assess E-selectin binding to 6-sulfo sLeX expressed on bladder urothelial carcinoma cells and performed reverse transcription polymerase chain reaction and complementary DNA transfection to determine which N-acetylglucosamine-6-O-sulfotransferases function in 6-sulfo sLeX biosynthesis in those cells. Finally, we performed double-immunofluorescence staining for MECA-79 and either CD3 or CD8 to evaluate potential association between high endothelial venule (HEV)-like vessels and tumor-infiltrating T lymphocytes.

RESULTS

6-Sulfo sLeX glycans were expressed in ~20% of bladder urothelial carcinoma cases, particularly in plasmacytoid and micropapillary variants. Positive cells were also bound by E-selectin·IgM chimeras in a calcium-dependent manner. Transcripts encoding N-acetylglucosamine-6-O-sulfotransferase-2 were detected preferentially in HT-1197 bladder urothelial carcinoma cells expressing 6-sulfo sLeX, and transfection of the enzyme complementary DNA into HT-1376 cells, which do not express 6-sulfo sLeX glycans, resulted in cell surface expression of 6-sulfo sLeX. Furthermore, 6-sulfo sLeX glycans were expressed in HEV-like vessels induced in and around lymphocyte aggregates formed near carcinoma cell nests. These HEV-like vessel-associated tumor-infiltrating lymphocytes were composed primarily of CD3(+) T cells, with a fraction of CD8(+) cytotoxic T cells.

CONCLUSIONS

Our findings indicate that 6-sulfo sLeX glycans likely play 2 roles in bladder urothelial carcinoma progression: one in lymphocyte recruitment to enhance antitumor immune responses, and the other in E-selectin-mediated tumor cell adhesion to vascular endothelial cells, which is potentially associated with metastasis.

In vitro evaluation of sialyl Lewis X relationship with head and neck cancer stem cells

OBJECTIVE

To evaluate in vitro the potential links between sialyl Lewis X (sLeX) and cancer stem cells (CSC) in head and neck squamous cell carcinoma (HNSCC). HNSCC is an aggressive malignancy with high mortality mainly due to metastasis. CSC have emerged as important players in HNSCC metastasis. sLeX is a tetrasaccharide carbohydrate known to play a key role in metastatic dissemination by promoting binding of the tumor cells to the endothelium.

STUDY DESIGN

Experimental, in vitro.

SETTING

Laboratory of Head and Neck Cancer Metastasis, University of Michigan.

SUBJECTS AND METHODS

A panel of stage- and anatomic-site specific primary and metastatic HNSCC cell lines was assessed by flow cytometry to quantify sLeX relative expression levels. Serum-free conditioned media from the same HNSCC lines was collected over a time course of 72 hours and assessed by Western blot for secreted sLeX expression. Representative HNSCC cell lines were cultured as floating orospheres (condition that enhance CSC growth) or under normal adherent conditions and characterized by flow cytometry for CSC markers (CD44, aldehyde dehydrogenase [ALDH]) comparatively with sLeX expression.

RESULTS

sLeX is predominantly expressed in carcinomas originating from the oral cavity. Secreted sLeX is also found to be high in oral carcinomas and increased over the analyzed time course. Floating orospheres were strongly positive for CD44 and ALDH, confirming CSC enrichment of the orospheres. Tumor cells grown as orospheres are 95% to 100% positive for sLeX compared to 10% to 40% of adherent counterpart.

CONCLUSION

These studies provide the first evidence of sLeX relationship with CSC in HNSCC.

Using boronolectin in MALDI-MS imaging for the histological analysis of cancer tissue expressing the sialyl Lewis X antigen

Certain carbohydrate-based biomarkers are known to correlate with cancer formation and progression. By targeting sialyl Lewis X, we have developed the first boronolectin-MS tag conjugate, which allows for MALDI-based imaging of cancer based on its cell surface carbohydrate.

Carbohydrate biomarkers for future disease detection and treatment

Carbohydrates are considered as one of the most important classes of biomarkers for cell types, disease states, protein functions, and developmental states. Carbohydrate "binders" that can specifically recognize a carbohydrate biomarker can be used for developing novel types of site specific delivery methods and imaging agents. In this review, we present selected examples of important carbohydrate biomarkers and how they can be targeted for the development of therapeutic and diagnostic agents. Examples are arranged based on disease categories including (1) infectious diseases, (2) cancer, (3) inflammation and immune responses, (4) signal transduction, (5) stem cell transformation, (6) embryo development, and (7) cardiovascular diseases, though some issues cross therapeutic boundaries.

Airway epithelial wound repair: role of carbohydrate sialyl Lewisx

Epithelial repair is a complex cellular and molecular process, the details of which are still not clearly understood. Plasma membrane glycoconjugates can modulate cell function by altering the function of protein and lipids. Sialyl Lewisx (sLex), a fucose-containing tetrasaccharide, decorates membrane-bound and secreted proteins and mediates cell-cell interaction. In the present study we investigated the role of sLex in airway epithelial repair. Using immunohistochemistry, we showed an increased expression of sLex in areas of damaged bronchial epithelium compared with intact regions. Confluent monolayers of airway epithelial cells were mechanically wounded and allowed to close. Wounded monolayers were photographed for wound closure kinetics, fixed for immunocytochemical studies, or subjected to RNA extraction. Examining the expression of different alpha1,3-fucosyltransferases (FucT), enzymes that mediate the final step in the synthesis of sLex, we found that FucT-IV was the common gene expressed in all cell lines and primary airway epithelial cells. We demonstrated an increased expression of sLex over time after mechanical injury. Blocking of sLex with an inhibitory antibody completely prevented epithelial repair. Our data suggest an essential functional role for sLex in epithelial repair. Further studies are necessary to explore the exact mechanism for sLex in mediating cell-cell interaction in bronchial epithelial cells to facilitate epithelial migration and repair.