Serum sialyl-Tn antigen levels in patients with digestive cancers

Aberrant Glycosylation as Immune Therapeutic Targets for Solid Tumors

Glycosylation occurs at all major types of biomolecules, including proteins, lipids, and RNAs to form glycoproteins, glycolipids, and glycoRNAs in mammalian cells, respectively. The carbohydrate moiety, known as glycans on glycoproteins and glycolipids, is diverse in their compositions and structures. Normal cells have their unique array of glycans or glycome which play pivotal roles in many biological processes. The glycan structures in cancer cells, however, are often altered, some having unique structures which are termed as tumor-associated carbohydrate antigens (TACAs). TACAs as tumor biomarkers are glycan epitopes themselves, or glycoconjugates. Some of those TACAs serve as tumor glyco-biomarkers in clinical practice, while others are the immune therapeutic targets for treatment of cancers. A monoclonal antibody (mAb) to GD2, an intermediate of sialic-acid containing glycosphingolipids, is an example of FDA-approved immune therapy for neuroblastoma indication in young adults and many others. Strategies for targeting the aberrant glycans are currently under development, and some have proceeded to clinical trials. In this review, we summarize the currently established and most promising aberrant glycosylation as therapeutic targets for solid tumors.

Role of tumor cell sialylation in pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies and is currently the third leading cause of cancer death. The aggressiveness of PDAC stems from late diagnosis, early metastasis, and poor efficacy of current chemotherapies. Thus, there is an urgent need for effective biomarkers for early detection of PDAC and development of new therapeutic strategies. It has long been known that cellular glycosylation is dysregulated in pancreatic cancer cells, however, tumor-associated glycans and their cognate glycosylating enzymes have received insufficient attention as potential clinical targets. Aberrant glycosylation affects a broad range of pathways that underpin tumor initiation, metastatic progression, and resistance to cancer treatment. One of the prevalent alterations in the cancer glycome is an enrichment in a select group of sialylated glycans including sialylated, branched N-glycans, sialyl Lewis antigens, and sialylated forms of truncated O-glycans such as the sialyl Tn antigen. These modifications affect the activity of numerous cell surface receptors, which collectively impart malignant characteristics typified by enhanced cell proliferation, migration, invasion and apoptosis-resistance. Additionally, sialic acids on tumor cells engage inhibitory Siglec receptors on immune cells to dampen anti-tumor immunity, further promoting cancer progression. The goal of this review is to summarize the predominant changes in sialylation occurring in pancreatic cancer, the biological functions of sialylated glycoproteins in cancer pathogenesis, and the emerging strategies for targeting sialoglycans and Siglec receptors in cancer therapeutics.

Identification of internally sialylated carbohydrate tumor marker candidates, including Sda/CAD antigens, by focused glycomic analyses utilizing the substrate specificity of neuraminidase

In our previous study, 14 sulfated carbohydrate tumor marker candidates were identified by focused glycomic analyses. Here, glycomic analyses focused on internally sialylated glycans to identify novel marker candidates. Internally sialylated glycans were enriched by digestion of pyridylaminated glycans prepared from sera with α-neuraminidase from Salmonella typhimurium, which did not cleave sialic acids linked to internal residues, followed by anion-exchange chromatography. Next, internally sialylated O-glycan profiles were constructed using two types of high performance liquid chromatography, which were compared between 20 healthy controls and 11 patients with gastric cancer and 9 patients with pancreatic cancer. In all, 17 marker candidates were identified. The structures of glycan candidates were precisely analyzed using enzymatic digestion, glycan synthesis, 2D mapping and mass spectrometry. Among 17 candidates, one was STn, and the other 16 comprised 10 core1, 1 core2 and 5 core3 glycans. The various structures included a α2,6-sialylated reducing terminal GalNAc and α2,6-sialylated type1 N-acetyl-lactosamine. Eight candidates possessed the Sda/CAD antigen. The levels of these candidate glycans in sera from all 40 subjects were quantified using a selected reaction monitoring assay and found to be elevated in at least one or more patients. Although the serum levels of each candidate glycan varied between patients, those candidates having the same backbone or determinant, such as core3 backbone and core1 structures with extended type1 N-acetyl-lactosamine, displayed similar patterns of elevation. These results suggest that analysis of multiple markers may be an effective means of diagnosing various cancers.

Correlation of serum sialyl Tn antigen values determined by immunoassay and SRM based method

We previously identified four glycan tumor marker candidates using a HPLC-based method. One candidate was sialyl Tn (STN), NeuAcα2-6-GalNAc. In this study, glycans were prepared from sera by hydrazine treatment followed by fluorescent labeling with aminopyridine. Pyridylaminated-STN levels of 147 gastric cancer, 85 pancreatic cancer and 10 cholangiocarcinoma patients together with 102 normal controls were accurately quantified using HPLC separation followed by selected reaction monitoring (SRM) assay, which used a stable isotope, tetradeuterium-labeled pyridylamino glycan as an internal standard. Additionally, STN values were also quantified using conventional competitive inhibition radioimmunoassay (RIA). The two STN levels determined by RIA and SRM gave a similar distribution pattern in sera. STN levels were increased in sera from cancer patients compared to those from normal controls. Moreover, the STN levels in sera of cancer patients determined by the two different assay procedures showed a good correlation (i.e., correlation coefficient >0.9). Our results suggest it may be better to determine STN levels using SRM instead of RIA.

Various sulfated carbohydrate tumor marker candidates identified by focused glycomic analyses

Glycomic analysis focused on sulfated O-glycans was performed to identify novel serum carbohydrate tumor markers. Sulfated glycans were enriched by α-neuraminidase digestion of pyridylaminated glycans prepared from sera, followed by anion exchange chromatography. Sulfated O-glycan profiles were constructed by two types of high performance liquid chromatography separation. Comparison of the profiles from 20 healthy controls with those of 11 gastric and 9 pancreatic cancer patients identified 14 marker candidates. The structures of these candidates were precisely analyzed using various methods including enzymatic digestion and mass spectrometry. The candidates comprised 9 core1 and 5 core2 glycans. All these candidates were monosulfated, and 11 were also mono- or difucosylated, and included various determinants such as 6-sulfo type2 lactosamine, 6-sulfo Lewis X, 6-sulfo Lewis Y, 3'-sulfo type1 lactosamine and 3'-sulfo Lewis A. Furthermore, among the core1 glycans, five candidates displayed a type1 and type2 lactosamine hybrid backbone. The levels of these candidate glycans in the sera from all 40 subjects were quantified using a selected reaction monitoring assay. These analyses revealed: (i) the levels of all candidates were elevated in sera of at least one or more patients; (ii) core1 candidates having type1-type2 hybrid backbones with 6-sulfo Lewis X, 6-sulfo type2 lactosamine or 3'-sulfo Lewis A were elevated in sera of variety of patients; and (iii) levels of the candidates varied widely among patients, suggesting analysis of multiple candidates will be an effective means of screening various cancers. To fully evaluate the clinical utility of these candidates, a further verification study is required.

A meta-analysis of the diagnostic value of detecting K-ras mutation in pancreatic juice as a molecular marker for pancreatic cancer

BACKGROUND

K-ras codon 12 mutation is one of the earliest genetic changes in the development of pancreatic cancer (PC) and accurate detection of K-ras mutations is gaining increasing attention in the field of molecular diagnosis.

METHODS

Original research articles which evaluated the diagnostic accuracy of K-ras mutation detection in PC were selected. Data were presented as forest plots and summary receiver operating characteristic curve analysis was used to summarize the overall test performance.

RESULTS

We assessed 16 studies from 15 published articles. The pooled sensitivity and specificity were 59% (95%CI: 54%-64%) and 87% (95%CI: 84%-89%), respectively. The pooled positive likelihood ratio and negative likelihood ratio were 4.13 (95%CI: 2.73-6.25) and 0.42 (95%CI: 0.32-0.56), respectively, and the pooled diagnostic odds ratio was 13.66 (95% CI: 7.25-25.74).

CONCLUSIONS

Our results indicate that the analysis of K-ras mutations in pancreatic juice has a considerable diagnostic value in PC. Further studies with rigorous design, large sample size, and multi-regional co-operation are needed.

The Role of Sialyl-Tn in Cancer

Activation of an aberrant glycosylation pathway in cancer cells can lead to expression of the onco-foetal sialyl-Tn (sTn) antigen. STn is a truncated O-glycan containing a sialic acid α-2,6 linked to GalNAc α-O-Ser/Thr and is associated with an adverse outcome and poor prognosis in cancer patients. The biosynthesis of the sTn antigen has been linked to the expression of the sialytransferase ST6GalNAc1, and also to mutations in and loss of heterozygosity of the COSMC gene. sTn neo- or over-expression occurs in many types of epithelial cancer including gastric, colon, breast, lung, oesophageal, prostate and endometrial cancer. sTn is believed to be carried by a variety of glycoproteins and may influence protein function and be involved in tumour development. This review discusses how the role of sTn in cancer development and tumour cell invasiveness might be organ specific and occur through different mechanisms depending on each cancer type or subtype. As the sTn-antigen is expressed early in carcinogenesis targeting sTn in cancer may enable the targeting of tumours from the earliest stage.

Elevation of CA19-9-Related Novel Marker, Core 1 Sialyl Lewis A, in Sera of Adenocarcinoma Patients Verified by a SRM-Based Method

We have attempted to identify a novel glycan tumor marker. Pyridylaminated (PA) O-glycans were prepared from sera, and the corresponding O-glycan profiles were constructed by HPLC separation. By comparing the serum O-glycan profiles from healthy controls with those of cancer patients, we identified a marker candidate, core 1 sialyl Lewis A (NeuAcα2-3Galβ1-3(Fucα1-4)GlcNAcβ1-3Gal) (abbreviated C1SLA), whose concentration appeared to be weakly correlated with CA19-9 values. To quantify this glycan, we developed a selected reaction monitoring (SRM) assay that used a stable isotope, tetradeuterium-labeled pyridylamino (d4-PA) glycan, as an internal standard. The analyte (d0-PA-C1SLA) and the internal standard (d4-PA-C1SLA) were subjected to SRM analyses after two types of HPLC separation. Serum levels of C1SLA, determined as the relative ratio to total O-glycans, were then measured. These analyses revealed that (i) C1SLA is a CA19-9-related glycan, (ii) the mean value of C1SLA in normal controls is 3.41 ppm, (iii) the level of C1SLA was significantly higher in samples of stages II-IV stomach cancers (P = 0.0036) as well as pancreatic cancers (P < 0.0001) compared to that of normal controls, (iv) the relationship between C1SLA and CA19-9 varies from poor to weak depending on the cancer, and (v) C1SLA could be valuable as a diagnostic adjunct for cancer.

Probing the O-glycoproteome of gastric cancer cell lines for biomarker discovery

Circulating O-glycoproteins shed from cancer cells represent important serum biomarkers for diagnostic and prognostic purposes. We have recently shown that selective detection of cancer-associated aberrant glycoforms of circulating O-glycoprotein biomarkers can increase specificity of cancer biomarker assays. However, the current knowledge of secreted and circulating O-glycoproteins is limited. Here, we used the COSMC KO "SimpleCell" (SC) strategy to characterize the O-glycoproteome of two gastric cancer SimpleCell lines (AGS, MKN45) as well as a gastric cell line (KATO III) which naturally expresses at least partially truncated O-glycans. Overall, we identified 499 O-glycoproteins and 1236 O-glycosites in gastric cancer SimpleCells, and a total 47 O-glycoproteins and 73 O-glycosites in the KATO III cell line. We next modified the glycoproteomic strategy to apply it to pools of sera from gastric cancer and healthy individuals to identify circulating O-glycoproteins with the STn glycoform. We identified 37 O-glycoproteins in the pool of cancer sera, and only nine of these were also found in sera from healthy individuals. Two identified candidate O-glycoprotein biomarkers (CD44 and GalNAc-T5) circulating with the STn glycoform were further validated as being expressed in gastric cancer tissue. A proximity ligation assay was used to show that CD44 was expressed with the STn glycoform in gastric cancer tissues. The study provides a discovery strategy for aberrantly glycosylated O-glycoproteins and a set of O-glycoprotein candidates with biomarker potential in gastric cancer.

COSMC knockdown mediated aberrant O-glycosylation promotes oncogenic properties in pancreatic cancer

BACKGROUND

Human pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal malignancies in the world and despite great efforts in research types of treatment remain limited. A frequently detected alteration in PDACs is a truncated O-linked N-acetylgalactosamine (GalNAc) glycosylation with expression of the Tn antigen. Changes in O-glycosylation affect posttranslationally modified O-GalNAc proteins resulting in profound cellular alterations. Tn antigen is a tumor associated glycan detected in 75-90 % of PDACs and up to 67 % in its precursor lesions. Since the role of Tn antigen expression in PDAC is insufficiently understood we analyzed the impact of COSMC mediated Tn antigen expression in two human PDAC cell lines on cellular oncogenic properties.

METHODS

Forced expression of Tn antigen on O-glycosylated proteins in pancreatic cancer cells was induced by lentiviral-mediated knockdown of the COSMC chaperone, which prevented O-glycan elongation beyond the initial GalNAcα1- residue on O-linked glycoproteins. Altered O-GalNAc glycosylation was analyzed in human pancreatic cancer cell lines Panc-1 and L3.6pl using Western and Far-Western blot as well as immunocytochemical techniques. To assess the biological implications of COSMC function on oncogenic properties, cell viability assays, scratch assays combined with live cell imaging, migration and apoptosis assays were performed. Lectin based glycoprotein enrichment with subsequent mass spectrometric analysis identified new cancer O-GalNAc modified proteins. Expression of Tn antigen bearing Nucleolin in patient derived PDAC tumor specimens was evaluated and correlated with clinicopathological data.

RESULTS

Tn antigen expression was induced on various O-GalNAc glycoproteins in COSMC deficient cell lines compared to the control. Proliferation was reduced (p < 0.001) in COSMC knockdown cells, whereas migration was increased (p < 0.001) and apoptosis was decreased (p = 0.03), highlighting the importance of Tn antigen expression on metastatic and anti-apoptotic behavior of PDAC derived cells. Nucleolin was identified as O-GalNAc modified protein in COSMC deficient PDAC cell lines. Interestingly, immunohistochemical staining and co-localization studies of patient derived PDACs revealed poor survival for patients with strong co-localization of Tn antigen and Nucleolin (p = 0.037).

CONCLUSION

This study substantiates the influence of altered O-glycan (Tn/STn) expression on oncogenic properties in pancreatic cancer and identifies O-GalNAc modified Nucleolin as novel prognostic marker.

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.

Precise structural analysis of O-linked oligosaccharides in human serum

O-glycans are suitable targets as novel and useful tumor markers. The structures of O-glycans in human sera from four healthy controls were precisely analyzed to obtain the reference O-glycan database. O-glycans were prepared from sera by hydrazine treatment followed by fluorescent labeling with aminopyridine and identified using two-dimensional mapping, enzymatic digestion and mass spectrometry (MS) together with methanolysis and the use of newly synthesized sulfated oligosaccharides as standards. O-glycans, present at more than 0.01% of the total O-glycans, were analyzed, and 18 kinds of acidic and 2 kinds of neutral glycans were identified. NeuAcα2-3Galβ1-3N-acetylgalactosamine (GalNAc) (61-64%), NeuAcα2-3Galβ1-3(NeuAcα2-6)GalNAc (15-26%) and Galβ1-3GalNAc (6-14%) were major components while other sialylated glycans, Galβ1-3(NeuAcα2-6)GalNAc, Galβ1-4GlcNAcβ1-6(NeuAcα2-3Galβ1-3)GalNAc and NeuAcα2-3Galβ1-4GlcNAcβ1-6(NeuAcα2-3Galβ1-3)GalNAc were relatively minor components, accounting for ∼1-2%. Very minor glycans accounting for ∼0.01-0.1% of the total include (i) the neutral glycan, Galβ1-4GlcNAcβ1-6(Galβ1-3)GalNAc, (ii) sialylated glycans, having sialyl Tn antigen, agalacto and trisialylated structures, (iii) fucosylated glycans forming blood type H antigen, blood type A antigen, blood type B antigen, Lewis X antigen and sialyl Lewis X antigen and (iv) sulfated glycans, having 6-sulfo and 3'-sulfo structures. Two kinds of clinically applied tumor markers namely sialyl Tn antigen and sialyl Lewis X antigen in healthy controls sera were revealed to be present at ∼0.1-0.2% of the total. However, other markers such as CA19-9 and DU-PAN-2 were not found, suggesting the relative amounts of these glycans to be <0.01%. These detailed O-glycan profiles will help to find novel carbohydrate tumor markers.

Sialyl-tn in cancer: (how) did we miss the target?

Sialyl-Tn antigen (STn) is a short O-glycan containing a sialic acid residue α2,6-linked to GalNAcα-O-Ser/Thr. The biosynthesis of STn is mediated by a specific sialyltransferase termed ST6GalNAc I, which competes with O-glycans elongating glycosyltransferases and prevents cancer cells from exhibiting longer O-glycans. While weakly expressed by fetal and normal adult tissues, STn is expressed by more than 80% of human carcinomas and in all cases, STn detection is associated with adverse outcome and decreased overall survival for the patients. Because of its pan-carcinoma expression associated with an adverse outcome, an anti-cancer vaccine, named Theratope, has been designed towards the STn epitope. In spite of the great enthusiasm around this immunotherapy, Theratope failed on Phase III clinical trial. However, in lieu of missing this target, one should consider to revise the Theratope design and the actual facts. In this review, we highlight the many lessons that can be learned from this failure from the immunological standpoint, as well as from the drug design and formulation and patient selection. Moreover, an irrefutable knowledge is arising from novel immunotherapies targeting other carbohydrate antigens and STn carrier proteins, such as MUC1, that will warrantee the future development of more successful anti-STn immunotherapy strategies.

The prognostic significance of sialyl-Tn antigen in women treated with breast carcinoma treated with adjuvant chemotherapy

BACKGROUND

Sialyl-Tn (STn) represents an aberrantly glycosylated mucin epitope that is expressed in breast carcinoma and other adenocarcinomas and is an important factor in the development of novel immunotherapeutic approaches. The primary aim of the current study was to investigate the influence of STn expression on the prognoses of patients with breast carcinoma.

METHODS

A cohort of 207 women diagnosed with invasive breast carcinoma who were treated with anthracycline-containing adjuvant chemotherapy and were enrolled in a randomized clinical trial were studied. Expression of STn was determined by an immunohistochemical procedure in which the B72.3 monoclonal antibody was used. Kaplan-Meier and Cox proportional regression survival analyses were used to compare low STn and high STn patients.

RESULTS

Forty-eight (23%) of the 207 specimens demonstrated high STn staining (>25% cells were immunoreactive). During a median follow-up of 5 years, high STn patients had worse disease free survival than low STn patients (55% vs. 74%, respectively; P = 0.03). High STn expression was significantly associated with age (P = 0.04) but not with other conventional prognostic markers. In multivariate analysis using the Cox regression model, high STn emerged as an independent prognostic indicator for disease free survival (hazard ratio [HR], 2.02; 95% confidence interval [CI], 1.09-3.73) and for overall survival (HR, 2.16; 95% CI, 0.95-4.92).

CONCLUSIONS

The results of this study suggest that STn may be a valuable marker for identifying women at high risk of developing recurrent breast carcinoma who may be candidates for trials investigating new therapies in combination with standard adjuvant therapy.

Sialosyl-Tn antigen as a marker of gastric cancer progression: an international study

Sialosyl-Tn, a mucin-associated carbohydrate antigen, is not expressed by normal mucus-producing cells of the stomach but becomes expressed in metaplastic, pre-malignant and malignant gastric tissues. Reports vary as to the frequency of STn expression and its prognostic role in gastric cancer. To determine whether these differences might be due to inter-country variations in gastric cancer biology, we immunohistochemically analyzed 340 gastric cancers from 2 countries at high-risk (high incidence) for gastric cancer (Japan and Chile), one with intermediate risk (Brazil) and one with low-risk (USA). Expression of STn was correlated with clinico-pathological features of the tumors and with cancer-related survival. Regardless of country, the frequency of STn-positive tumors was lower in non-invasive ("early") than in advanced gastric cancer. Consequently, high-risk countries where early gastric cancer is more common demonstrated a lower overall frequency of STn-positive tumors. In all 4 countries, STn expression directly correlated with depth of invasion, stage, and lymph node involvement. In addition, STn expression correlated with a poor prognosis in all 4 countries, but the effect of STn on survival was not independent of tumor stage. Our findings indicate the need to consider the inherent gastric cancer risk and prevalence of early gastric cancer in the study population when reporting frequency of STn expression in gastric cancer. Regardless of country, however, STn expression is a marker of gastric cancer progression suggesting that cancer-associated mucins play a role in the malignant behavior of this tumor.

Expression of sialyl-Tn in gastric cancer: correlation with known prognostic factors

Sialyl-Tn (STn) is a core region carcinoma-associated carbohydrate determinant expressed on cancer-associated mucins. Expression of STn has been associated with poor prognosis in colon and ovarian cancer, independent of other prognostic factors such as tumour grade, stage or histological type. Recent studies have suggested that STn expression may be an independent prognostic variable in gastric cancer. We have examined 158 patients with gastric cancer using the antibody B72.3 (Biomira, Edmonton, Alberta, Canada). Of these, 110 patients (70%) expressed STn. Expression of STn did not correlate with tumour differentiation or the Ming classification, but expression was noted more frequently in the relatively good prognosis intestinal type of tumours (chi 2 = 6.9, P = 0.03). Conversely, early-stage cancers showed a significantly lower frequency of expression than more advanced cases (chi 2 = 13.75, P = 0.003). In this patient group, STn expression did not influence survival, and in multivariate regression analysis only tumour stage and Lauren classification were found to be independent prognostic variables.

Variability of neoplastic parameters in colon tumours, and its significance in diagnostic practice

We have reviewed the value of individual variability in the reaction of tissues to treatment with carcinogens, and the manifestation of this variability in different morphological (histological, morphometric, and ultrastructural), histochemical and immunohistochemical parameters generated in tumorous tissues. Moreover, we also reviewed data in the literature on individual variability in the manifestation of some biochemical and immunochemical markers which are accumulated in the serum of tumour-bearing patients and which are characteristic for the different phases of tumourigenesis. The high variability of different tumorous parameters suggests that none can be utilized alone as a conclusive marker of neoplasia and that only their combined use can give objective information. We also reviewed the impact of this variability in the evaluation of various pathological methods to detect different stages of neoplastic transformation in the colon. It has been concluded that none of the present approaches can be absolutely conclusive and without false results, and that objective information regarding early cancerous changes may be obtained only by use of combined analyses utilizing several laboratory methods. The diagnostic procedures should be based on the complex utilization of all appropriate methods using the quantitative interpretation of the obtained data. Multivariate analysis of many parameters should be very effective for the prediction of therapeutic results.

Correlation between sialyl Tn antigen and lymphatic metastasis in patients with Borrmann type IV gastric carcinoma

The expression of sialyl Tn (STn) antigen in 180 patients with Borrmann type IV gastric carcinomas was examined immunohistochemically. The rate of positive STn staining was 32% (57/180) for the primary tumours, and this positive staining correlated well with tumour extension, lymph node metastasis (P < 0.05) and peritoneal dissemination (P < 0.01). One-third (5/15) of patients with positive STn-staining cancer cells had a high level of serum STn. Lesions with positive STn staining were related to a lower survival rate for the patients (P < 0.05). Proliferative activity of the tumour, as measured by proliferating nuclear antigen (PCNA) labelling percentage and argyrophilic nucleolar organiser region (AgNOR) count, was significantly higher (41.5 +/- 13.0%, 3.78 +/- 0.98) in the STn-positive group than in the STn-negative group (34.2 +/- 13.2%, 3.48 +/- 0.85) (P < 0.01, P < 0.05 respectively). Estimating STn antigen may be useful for predicting the likelihood of lymph node metastasis or peritoneal dissemination and the clinical prognosis for patients with Borrmann type IV gastric carcinoma.

Expression of sialyl-Tn predicts the effect of adjuvant chemotherapy in node-positive breast cancer

Sialyl-Tn (STn) is a carcinoma-associated carbohydrate determinant expressed on cancer-associated mucins and has the structure NANA alpha(2-6)alpha GalNAc. Expression of STn in colon and ovarian cancer is associated with a poor prognosis independent of tumour grade, stage or histological type. We have examined 237 cases of primary breast cancer for expression of this antigen using the antibody HB-STn (Dako). The frequency of STn expression was 31% in the whole group, 36% in the node-negative and 28% in the node-positive group. Survival was lower, but not significantly so, in the STn-positive group (P = 0.07), but this effect was highly significant for patients with node-positive disease (P < 0.002), the curves for node-negative disease being coincident (P = 0.31). In node-positive disease the effect was limited to those receiving adjuvant chemotherapy (P = 0.001). In a multivariate (Cox) analysis on the whole group STn staining, combined with adjuvant chemotherapy, showed a highly significant correlation with survival. In STn-negative cases, adjuvant chemotherapy improved survival (relative risk 2.3, 95% confidence intervals 1.4-3.9), whereas adjuvant chemotherapy did not influence survival in patients which expressed STn (relative risk 1.1, 95% confidence intervals 0.6-2.2). Thus, by either direct or indirect mechanisms, STn positivity appears to be a marker of resistance to adjuvant chemotherapy.

Expression of sialosyl-Tn antigen (monoclonal antibody MLS102 reactive) in normal tissues and malignant tumors of the digestive tract

Oncogenic transformation is often associated with changes in the glycosylation state of malignant cells. We investigated the immunohistochemical localization of sialosyl-Tn antigen [O-linked NeuAc(alpha 2-->6)GAINAc] using a novel monoclonal antibody MLS102 in normal and malignant digestive-tract tissues. In normal tissues, weak MLS102 immunoreactivity was observed in the epithelium of the esophagus, stomach and colon. However, MLS102 immunoreactivity was strong in the goblet cells of the duodenum, but not in the Brunner glands. In carcinomas of the esophagus, stomach, colon, pancreas and biliary tract, positive staining was detected with a high frequency (80%-100%). In mucinous carcinomas and signet-ring cell carcinomas, malignant cells themselves and the mucins they secreted were strongly positive for sialosyl-Tn antigen. There was no significant correlation between the frequency of expression of sialosyl-Tn antigen and the degree of differentiation (grade). However, in the case of well-differentiated adenocarcinomas, sialosyl-Tn antigen was found mainly in the supranuclear areas (Golgi area), on the apical surface and in the adjacent cytoplasm. In poorly differentiated adenocarcinomas, the antigen was often detected in the whole plasma membrane and cytoplasm. Therefore, monoclonal antibody MLS102 may be useful in further elucidating the characteristics of digestive-tract cancers, and possibly in their treatment.

Mucin-associated sialosyl-Tn antigen expression in gastric cancer correlates with an adverse outcome

The expression of sialosyl-Tn (STn) antigen was evaluated by immunohistochemistry in primary gastric cancers. Twenty-one of 31 (68%) gastric cancers expressed STn, regardless of tumour location, stage or histological type. Eighty-one per cent of patients with STn-positive tumours died of their disease or had recurrent cancer, compared with 20% of patients with STn-negative tumours (P < 0.002). STn may be a useful prognostic marker in patients with gastric cancer.

Association between expression of sialosyl-Tn antigen and intestinalization of gastric carcinomas

We examined immunohistochemically the expression of sialosyl-Tn antigen (STN) in 137 primary gastric carcinomas. In the non-neoplastic mucosa, STN was expressed in all goblet cells, most absorptive cells and Paneth cells of intestinalized tubules, whereas it was not seen in the gastric mucosa proper. We evaluated the association between the mucin-histochemical findings of intramucosal carcinomas and the STN-expression. STN was expressed in 8 of 20 undifferentiated-type carcinomas, all of which were mucin-histochemically of the gastric type. STN was expressed in 25 of 51 differentiated-type carcinomas, among which it was expressed in 3 of 12 gastric-type, 11 of 17 intestinal-type and 11 of 22 mixed-type adenocarcinomas. The extent of STN expression in the intestinal-type adenocarcinomas was significantly higher than in gastric-type adenocarcinomas and undifferentiated-type carcinomas, and that seen in mixed-type adenocarcinomas was significantly higher than in the gastric-type adenocarcinomas. We also examined STN expression in early and advanced carcinomas. As the depth of carcinoma invasion progressed, the extent of STN expression was significantly higher and its incidence was significantly higher. Our findings suggest that STN expression reflects intestinalization of the gastric mucosa, and that a kind of intestinal metaplasia occurs in progressing gastric carcinoma cells.

Comparison of two sialosyl-Tn binding monoclonal antibodies (MLS102 and B72.3) in detecting pancreatic cancer

An immunohistochemical study has been carried out to compare and contrast the cellular distribution of two different sialosyl-Tn antigen binding monoclonal antibodies, MLS102 and B72.3, in the pancreas. MLS102 but not B72.3 monoclonal antibody binding increases with the content of the sialosyl-Tn epitopes. It was found that all 13 pancreatic cancer specimens bound both MLS102 and B72.3 monoclonal antibodies. Their cellular distribution in the cancer was virtually identical. Fifteen of 20 (75%) patients with chronic pancreatitis and five of 10 (50%) normal subjects were B72.3 positive, but MLS102 was completely negative in the latter group. Both monoclonal antibodies bound fetal pancreas diffusely. Thus, when pancreatic ductal cells have undergone malignant transformation, like the fetal pancreas, they express cell surface and secreted glycoconjugates with increased sialosyl-Tn epitopes suggesting enhanced 2-6 sialosyltransferase activity. This study shows that MLS102 is an extremely sensitive and specific tumour marker in the pancreas and that it is better than B72.3 in distinguishing pancreatic cancer from normal and chronic pancreatitis.

Predictive value of preoperative serum sialyl Tn antigen levels in prognosis of patients with gastric cancer

BACKGROUND

Expression of sialyl Tn antigen (STN) or serum STN levels were reported to be the independent prognostic factors of colon and ovarian cancers, respectively. The clinical significance of serum STN was evaluated as a tumor marker in gastric cancer.

METHODS

Preoperative STN levels were examined in 350 patients with gastric cancer, surgically treated in the Department of Surgery II, Kyushu University Hospital, and in the National Kyushu Cancer Center, between April, 1981 and April, 1986. The patients were divided into two groups: a high STN group (n = 304), with over 45 U/ml of STN, and a low STN group (n = 46), with less than or equal to 45 U/ml.

RESULTS

In the high STN group, the patients were older and the tumors were larger, compared to the low STN group. Histologically, tumors in the high STN group were deeply penetrating and the rates of lymphatic involvement, vascular involvement, and lymph node and hepatic metastases were higher. Infiltrative growth patterns dominated. Thus, the tumors were in an advanced stage. The 5-year survival rate for patients in the high STN group was significantly less than that of patients in the low STN group (44.8% +/- 7.9% versus 75.1% +/- 2.6%, P < 0.05).

CONCLUSIONS

Because a high STN level correlates with an advanced tumor stage and a poorer prognosis, close follow-up and aggressive therapy are recommended.

Expression of sialyl-Tn antigen is correlated with survival time of patients with gastric carcinomas

Expression of sialyl-Tn antigen (STN) was examined by an immunohistochemical method in 85 primary gastric carcinomas. The STN expression occurred in 53 (62.4%) cancers, and the positive staining was correlated with degree of gastric wall and lymph vessel invasion, lymph node metastasis, and stage of tumour. Five-year survival rates of patients with STN-positive cancers (47.2%) were significantly lower than those with STN-negative cancers (84.4%) (P < 0.01), and patients with STN-positive cancers at stage III and stage IV had a worse prognosis. In the cancers with serosal invasion, patients with STN-positive cancer disclosed a significantly poorer prognosis than those with STN-negative cancers (P < 0.01). Therefore, it is suggested that a careful follow-up study and intensive postoperative therapy are needed for patients with advanced gastric cancers with positive STN expression.