CEA is the major PHA-L-reactive glycoprotein in colon carcinoma cell lines and tumors: relationship between K-ras activation and beta1-6 branching of N-linked carbohydrate on CEA

Aberrant Glycosylation in Pancreatic Ductal Adenocarcinoma 3D Organoids Is Mediated by KRAS Mutations

Aberrant glycosylation in tumor cells is a hallmark during carcinogenesis. KRAS gene mutations are the most well-known oncogenic abnormalities but their association with glycan alterations in pancreatic ductal adenocarcinoma (PDAC) is largely unknown. We employed patient-derived 3D organoids to culture pure live PDAC cells, excluding contamination by fibroblasts and immune cells, to gasp the comprehensive cancer cell surface glycan expression profile using lectin microarray and transcriptomic analyses. Surgical specimens from 24 PDAC patients were digested and embedded into a 3D culture system. Surface-bound glycans of 3D organoids were analyzed by high-density, 96-lectin microarrays. KRAS mutation status and expression of various glycosyltransferases were analyzed by RNA-seq. We successfully established 16 3D organoids: 14 PDAC, 1 intraductal papillary mucinous neoplasm (IPMN), and 1 normal pancreatic duct. KRAS was mutated in 13 (7 G12V, 5 G12D, 1 Q61L) and wild in 3 organoids (1 normal duct, 1 IPMN, 1 PDAC). Lectin reactivity of AAL (Aleuria aurantia) and AOL (Aspergillus oryzae) with binding activity to α1-3 fucose was higher in organoids with KRAS mutants than those with KRAS wild-type. FUT6 (α1-3fucosyltransferase 6) and FUT3 (α1-3/4 fucosyltransferase 3) expression was also higher in KRAS mutants than wild-type. Meanwhile, mannose-binding lectin (rRSL [Ralstonia solanacearum] and rBC2LA [Burkholderia cenocepacia]) signals were higher while those of galactose-binding lectins (rGal3C and rCGL2) were lower in the KRAS mutants. We demonstrated here that PDAC 3D-cultured organoids with KRAS mutations were dominantly covered in increased fucosylated glycans, pointing towards novel treatment targets and/or tumor markers.

KRAS Mutational Profiles among Colorectal Cancer Patients in the East Coast of Peninsular Malaysia

BACKGROUND

KRAS is a key driver gene in colorectal carcinogenesis. Despite this, there are still limited data on the mutational status of KRAS amongst colorectal cancer (CRC) patients in Malaysia. In the present study, we aimed to analyze the KRAS mutational profiles on codons 12 and 13 amongst CRC patients in Hospital Universiti Sains Malaysia, Kelantan, located on the East Coast of Peninsular Malaysia.

METHODS

DNA were extracted from formalin-fixed, paraffin-embedded tissues obtained from 33 CRC patients diagnosed between 2018 and 2019. Amplifications of codons 12 and 13 of KRAS were conducted using conventional polymerase chain reaction (PCR) followed by Sanger sequencing.

RESULTS

Mutations were identified in 36.4% (12/33) of patients, with G12D (50%) being the most frequent single-point mutation observed, followed by G12V (25%), G13D (16.7%), and G12S (8.3%). No correlation was found between mutant KRAS and location of the tumor, staging, and initial carcinoembryonic antigen (CEA) level.

CONCLUSION

Current analyses revealed that a significant proportion of CRC patients in the East Coast of Peninsular Malaysia have KRAS mutations, where this frequency is higher compared to those in the West Coast. The findings of this study would serve as a precursor for further research that explores KRAS mutational status and the profiling of other candidate genes among Malaysian CRC patients.

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.

Wisteria floribunda agglutinin-binding glycan expression is decreased in endometriomata

BACKGROUND

Glycosylation is one of the most common post-translational modifications of eukaryotic proteins and is known to undergo dynamic changes in a wide range of biological processes. To date, however, the glycan expression profiles in endometriosis are largely unknown. The objective of the study was to identify the panel of glycans that were aberrantly expressed in endometriosis, a hormone-dependent disease.

METHODS

The glycan expression profiles in primary cultured human endometriotic cyst stromal cells (ECSCs) and normal endometrial stromal cells (NESCs) were determined by lectin microarray analysis. Distribution of Wisteria floribunda agglutinin (WFA)-binding glycans in ovarian endometriotic cysts and eutopic proliferative phase endometrium were assessed by lectin histochemistry. The expressions of N-acetylgalactosaminyl transferases that synthesize WFA-binding glycans were evaluated in ECSCs and NESCs.

RESULTS

We found that the levels of WFA-binding glycans were decreased in ECSCs. Lectin histochemistry revealed that WFA-binding glycans were decreased only in the stromal components of the ovarian endometriotic cysts, but not in the epithelial components, compared to the eutopic proliferative phase endometrium. The expressions of N-acetylgalactosaminyl transferases that synthesize WFA-binding glycans were downregulated in ECSCs.

CONCLUSIONS

Utilizing lectin microarray analysis and lectin histochemistry, we found that WFA-binding glycans were decreased in endometriosis. The synthetic enzymes of WFA-binding glycans were significantly downregulated in ECSCs. It is suggested that reduced expression of N-glycans with WFA-binding properties on ECSCs is a novel characteristics of endometriosis.

Are high initial CEA and CA 19-9 levels associated with the presence of K-ras mutation in patients with metastatic colorectal cancer?

In certain cell culture studies, significant CEA expression was observed in K-ras mutant cells. However, the relationship between high CEA levels and K-ras status has not been sufficiently investigated. In the present study, we aimed to determine the prognostic role of initial CEA and CA 19-9 values in metastatic colorectal cancer patients according to the status of K-ras. Between 2000 and 2010, a total of 215 patients with metastatic colorectal cancer who were treated and followed up in our oncology center were analyzed. Smokers were excluded from the study. The clinicopathological findings and initial CEA and CA19-9 values were determined. K-ras mutation analysis was performed using quantitative PCR evaluation of the DNA from the tumor tissues. Eighty-two patients (38.1 %) were female and 133 (61.9 %) were male, with a median age of 59 years (range 27-83). Based on tumor localization, 127 patients (59 %) were classified as colon cancer patients and 88 patients (41 %) were classified as rectal cancer patients. The majority of patients (83.3 %) had pure adenocarcinoma histology, while 36 cases (16.7 %) had mucinous adenocarcinoma. The initial CEA levels were detected to be high (>5 ng/mL) in 108 of the patients (50.2 %), while high levels of initial CA 19-9 (>37 ng/mL) were found in 90 patients (41.8 %). K-ras mutations were detected in 99 of the patients (46 %). K-ras was found to be wild type in 116 patients (54 %). Significant differences were detected between the K-ras wild-type and mutant groups with respect to age and the initial serum CEA levels. Patients with K-ras mutations were younger (p = 0.04) and had higher initial CEA levels (p = 0.02) compared to patients with K-ras wild type. The median overall survival (OS) time and 3-year OS rate for patients with a high initial CEA level (>5 ng/mL) were significantly shorter than those of patients with a low initial CEA level (<5 ng/mL) (50.5 months and 61.8 % vs. 78.6 months and 79.1 %, p = 0.014). Furthermore, the patients with low initial CA 19-9 levels (<37 ng/mL) had a significant better median OS interval and 3-year OS rate (76.1 months and 80.1 %) compared to patients with high initial CA 19-9 levels (>37 ng/mL) (37.6 months and 55.7 %, p = 0.04). Multivariate analysis indicated that stage at the time of diagnosis (p < 0.001) and low initial serum CEA level (p = 0.037) were independent prognostic factors of OS. For K-ras mutant patients, the stage at diagnosis (p = 0.017), low initial serum CEA level (p = 0.001), and low initial serum CA 19-9 level were found to be independent prognostic indicators of OS. Our findings demonstrate for the first time that the presence of a K-ras mutation correlated with high initial CEA and CA 19-9 levels in patients with metastatic colorectal cancer. Patients with high initial CEA and CA 19-9 levels may potentially predict the presence of a K-ras mutation, and this prediction may guide targeted therapies in these patients.

Development of an all-in-one technology for glycan profiling targeting formalin-embedded tissue sections

An ultra-sensitive method for glycan analysis targeting small tissue sections (1.5mm in diameter) is described as an application of a recently-established lectin microarray technology. The developed system achieved a high level of detection of a tissue section consisting of approximately 500 cells for differential profiling, where both N- and O-glycans attached to a pool of glycoproteins are subjected to multiplex analysis with 43 lectins. By using an optimized protocol for differential glycan analysis, sections of adenocarcinoma (n=28) and normal epithelia (n=12) of the colon were analyzed in an all-in-one manner. As a result, Wisteria floribunda agglutinin (WFA) was found to clearly differentiate cancerous from normal epithelia with P<0.0001. The obtained results correlated well with the subsequent histochemical study using biotinylated WFA. Thus, the developed technology proved to be valid for expanding the lectin microarray applications to tissue-based glycomics, and hence, should accelerate a discovery phase of glycan-related biomarkers.

Biological applications of a chimeric probe for the assessment of galectin-3 ligands

Beta1-6 branching of N-linked oligosaccharides has been correlated with the progression of different cancers. The leukoagglutinins of Phaseolus vulgaris (L-PHA) have been used to study this pattern of glycosylation whose biological significance is incompletely understood. The animal lectin, galectin-3, also binds to structures recognized by L-PHA. To develop a functional tool for the in situ identification of this pattern of glycosylation, human galectin-3 was fused to bacterial alkaline phosphatase (gal3/AP). Gal3/AP recognized both A and B blood group saccharides (B>A) and lactosamine derivatives. Gal3/AP recognition depended at least in part on the N-linked oligosaccharides of different glycoproteins. The presence and distribution of galectin-3 ligands were analyzed in both murine and human normal and tumor samples. Loss of apical expression of galectin-3 ligands was commonly found in carcinomas. Endothelial and inflammatory cells were enriched in galectin-3 ligands as compared with tumor cells; thus, gal3/AP is a suitable tool for studying tumor microenvironments. Comparative analysis of both gal3/AP and L-PHA binding patterns indicated that although similar, these patterns are not identical. The probe developed was useful for several immunoenzymatic assays and will allow the physiological and clinical significance of the expression pattern of galectin-3 ligands to be established. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Identification of proteins bearing beta1-6 branched N-glycans in human melanoma cell lines from different progression stages by tandem mass spectrometry analysis

The common structural alterations in the cell-surface glycoproteins concern the highly elevated expression of tri- and tetra-antennary beta1-6-N-acetylglucosamine (beta1-6 GlcNAc) bearing N-glycans, which are recognised by Phaseolus vulgaris agglutinin (PHA-L). In this report we identified proteins bearing beta1-6 GlcNAc branched N-glycans in three human melanoma cell lines: WM35--from the primary tumour site, as well as WM239 and WM9 from different metastatic sites: the skin and the lymph node, respectively, by tandem mass spectrometry (MS/MS) on PHA-L agarose bound material, followed by immunochemical identification. Our results show that melanoma cell lines differ from each other in the number of N-glycoproteins bearing beta1-6 GlcNAc branched oligosaccharides. Among identified proteins the largest group consists of integrin subunits. In addition, L1-CAM, Mac-2 binding protein, melanoma cell adhesion molecule, intercellular adhesion molecule, melanoma associated antigen, tumour rejection antigen-1, melanoma-associated chondroitin sulfate proteoglycan 4 and lysosome-associated membrane protein (LAMP-1) were found. It was indicated that WM35 cell line showed the lowest number of proteins possessing beta1-6 GlcNAc branched N-glycans in comparison to metastatic WM9 and WM239 cell lines. Our data suggest that changes in the number of proteins being a substrate for GlcNAc-TV are better correlated with melanoma development and progression than with expression of cell adhesion molecules.

Specific Detection of Glycans on a Plasma Membrane of Living Cells with Atomic Force Microscopy

Among the many alterations of cancer cells is the expression of different surface oligosaccharides. In this work, oligosaccharide expression in living cells (cancer and reference ones) was studied with atomic force microscopy by using lectins as probes. The unbinding force obtained for the same lectin type (concanavalin A or Sambucus nigra) suggested slightly dissimilar structures of binding sites of the same ligand type. For the lectin from Phaseolus vulgaris, a much larger unbinding force indicated a distinct structure of the binding site in cancer cells. The unbinding probability confirmed a higher content of both sialic acid and mannose-containing ligands in cancer and reference cells, respectively. These results demonstrate the potential of atomic force microscopy to directly probe the presence of molecules on a living cell surface, together with the quantitative description of their expression.

Control of colorectal metastasis formation by K-Ras

Mutational activation of the K-Ras proto-oncogene is frequently observed during the very early stages of colorectal cancer (CRC) development. The mutant alleles are preserved during the progression from pre-malignant lesions to invasive carcinomas and distant metastases. Activated K-Ras may therefore not only promote tumor initiation, but also tumor progression and metastasis formation. Metastasis formation is a very complex and inefficient process: Tumor cells have to disseminate from the primary tumor, invade the local stroma to gain access to the vasculature (intravasation), survive in the hostile environment of the circulation and the distant microvascular beds, gain access to the distant parenchyma (extravasation) and survive and grow out in this new environment. In this review, we discuss the potential influence of mutant K-Ras on each of these phases. Furthermore, we have evaluated the clinical evidence that suggests a role for K-Ras in the formation of colorectal metastases.

N-glycoproteins bearing beta1-6 branched oligosaccharides from the A375 human melanoma cell line analysed by tandem mass spectrometry

Tumour-associated alterations of cell surface glycosylation play a crucial role in the adhesion and metastasis of cancer cells. It is well known that the metastatic potential is associated with increased GlcNAc beta1-6 branching in N-glycans of tumour cells specifically recognized by a lectin from Phaseolus vulgaris leukoagglutinin (PHA-L). We identified proteins bearing GlcNAc beta1-6 branched N-glycans in the A375 human melanoma cell line by affinity chromatography separation on a PHA-L agarose column, followed by immunoidentification and tandem mass spectrometry (MS/MS) analysis. Amongst the proteins identified were integrin subunits alpha2, alpha3, alpha5 and beta1, as well as N-cadherin and lysosome-associated membrane proteins (LAMP-1 and LAMP-2). In addition, L1, Mac-2 binding protein (Mac-2-BP), activated leukocyte cell adhesion molecule/CD166 (ALCAM) and melanotransferrin were shown to react with PHA-L. Some of these proteins are connected mainly with nervous tissues or the immune system and play a crucial role in cell adhesion processes. The presence of GlcNAc beta1-6 branched oligosaccharides in these proteins may influence their adhesion properties, reducing adhesion of the cells to the extracellular matrix (ECM) and thus facilitating tumour cell invasion.

Glycosylation profile of integrin α3β1 changes with melanoma progression

Glycosylation of integrins has been implicated in the modulation of their function. Characterisation of carbohydrate moieties of alpha(3) and beta(1) subunits from non-metastatic (WM35) and metastatic (A375) human melanoma cell lines was carried out on peptide-N-glycosidase F-released glycans using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). beta(1) integrin subunit from both cell lines displayed tri- and tetraantennary oligosaccharides complex type glycans, but only in A375 cell line was the sialylated tetraantennary complex type glycan (Hex(7)HexNAc(6)FucSia(4)) present. In contrast, only alpha(3) subunit from metastatic cells possessed beta1-6 branched structures. Our data indicate that the beta(1) and alpha(3) subunits expressed by the metastatic A375 cell line carry beta1-6 branched structures, suggesting that these cancer-associated glycan chains may modulate tumor cell adhesion by affecting the ligand binding properties of alpha(3)beta(1) integrin. In direct ligand binding assays, alpha(3)beta(1) integrin from both cell lines binds strongly to fibronectin and to much lesser degree to placental laminin. No binding to collagen IV was observed. Enzymatic removal of sialic acid residues from purified alpha(3)beta(1) integrin stimulates its adhesion to all examined ECM proteins. Our data suggest that the glycosylation profile of alpha(3)beta(1) integrin in human melanoma cells correlates with the acquisition of invasive capacity during melanoma progression.

beta 1,3-Galactosyltransferase beta 3Gal-T5 acts on the GlcNAcbeta 1-->3Galbeta 1-->4GlcNAcbeta 1-->R sugar chains of carcinoembryonic antigen and other N-linked glycoproteins and is down-regulated in colon adenocarcinomas

We attempted to determine whether beta1,3-galactosyltransferase beta3Gal-T5 is involved in the biosynthesis of a specific subset of type 1 chain carbohydrates and expressed in a cancer-associated manner. We transfected Chinese hamster ovary (CHO) cells expressing Fuc-TIII with beta3Gal-T cDNAs and studied the relevant glycoconjugates formed. beta3Gal-T5 directs synthesis of Lewis type 1 antigens in CHO cells more efficiently than beta3Gal-T1, whereas beta3Gal-T2, -T3, and -T4 are almost unable to direct synthesis. In the clone expressing Fuc-TIII and beta3Gal-T5 (CHO-FT-T5), sialyl-Lewis a synthesis is strongly inhibited by swainsonine but not by benzyl-alpha-GalNAc, and sialyl-Lewis x is absent, although it is detected in the clones expressing Fuc-TIII and beta3Gal-T1 (CHO-FT-T1) or Fuc-TIII and beta3Gal-T2 (CHO-FT-T2). Endo-beta-galactosidase treatment of N- glycans prepared from clone CHO-FT-T5 releases (+/-NeuAcalpha2-->3)Galbeta1-->3[Fucalpha1-->4]GlcNAcbeta1-->3Gal but not GlcNAcbeta1-->3Gal or type 2 chain oligosaccharides, which are found in CHO-FT-T1 cells. This result indicates that beta3Gal-T5 expression prevents poly-N-acetyllactosamine and sialyl-Lewis x synthesis on N-glycans. Kinetic studies confirm that beta3Gal-T5 prefers acceptors having the GlcNAcbeta1-->3Gal end, including lactotriosylceramide. Competitive reverse transcriptase mediated-polymerase chain reaction shows that the beta3Gal-T5 transcript is expressed in normal colon mucosa but not or poorly in adenocarcinomas. Moreover, recombinant carcinoembryonic antigen purified from a CHO clone expressing Fuc-TIII and beta3Gal-T5 reacts with anti-sialyl-Lewis a and carries type 1 chains on oligosaccharides released by endo-beta-galactosidase. We conclude that beta3Gal-T5 down-regulation plays a relevant role in determining the cancer-associated glycosylation pattern of N-glycans.