Reduced αGlcNAc glycosylation on gastric gland mucin is a biomarker of malignant potential for gastric cancer, Barrett’s adenocarcinoma, and pancreatic cancer

The Role of Mucin Expression in the Diagnosis of Oesophago-Gastric Cancer: A Systematic Literature Review

Survival in oesophago-gastric cancer (OGC) is poor due to early diagnostic challenges. Non-invasive risk stratification may identify susceptible patients with pre-malignant or benign disease. Following diagnostic confirmation with endoscopic biopsy, early OGC may be treated sooner. Mucins are transmembrane glycoproteins implicated in OGC with potential use as biomarkers of malignant transformation. This systematic review defines the role of mucins in OGC diagnosis. A literature search of MEDLINE, Web of Science, Embase and Cochrane databases was performed following PRISMA protocols for studies published January 1960-December 2022. Demographic data and data on mucin sampling and analysis methods were extracted. The review included 124 studies (n = 11,386 patients). Gastric adenocarcinoma (GAc) was the commonest OG malignancy (n = 101) followed by oesophageal adenocarcinoma (OAc, n = 24) and squamous cell carcinoma (OSqCc, n = 10). Mucins MUC1, MUC2, MUC5AC and MUC6 were the most frequently implicated. High MUC1 expression correlated with poorer prognosis and metastases in OSqCc. MUC2 expression decreases during progression from healthy mucosa to OAc, causing reduced protection from gastric acid. MUC5AC was upregulated, and MUC6 downregulated in GAc. Mucin expression varies in OGC; changes may be epigenetic or mutational. Profiling upper GI mucin expression in OGC, with pre-malignant, benign and healthy controls may identify potential early diagnostic biomarkers.

Esophagogastroduodenal Findings in Patients with Intraductal Papillary Mucinous Neoplasms

The association between intraductal papillary mucinous neoplasms (IPMNs) and extra-pancreatic malignancies is controversial. This cross-sectional study compared esophagogastroduodenal findings in 340 IPMN patients to those of age- and gender-matched controls without known IPMNs who underwent esophagogastroduodenoscopies (EGDs) for similar clinical reasons. The presence of gastric and esophageal cancer, Barrett's esophagus, neuroendocrine tumors (NETs), gastrointestinal stromal tumors (GISTs), gastric adenomas, and ampullary tumors was assessed. The results showed that 4/340 (1.2%) of the IPMN patients had gastric cancer and 1/340 (0.3%) had esophageal cancer. The matched control group had a similar incidence of gastric cancer (5/340) (1.5%), with no esophageal cancer cases (p > 0.999). The overall incidence of other esophagogastroduodenal conditions did not significantly differ between the IPMN patients and the controls. However, the incidence of gastric cancer in the IPMN patients was higher than expected based on national cancer registry data (standardized incidence ratio of 31.39; p < 0.001; CI 8.38-78.76). In conclusion, IPMN patients have a significantly higher incidence of gastric cancer compared to the general population. However, the incidence of esophagogastroduodenal findings, including gastric and esophageal cancer, is similar between IPMN patients and those who undergo an EGD for similar clinical indications. Further research is needed to determine optimal surveillance strategies for IPMN patients regarding their risk of developing gastric cancer.

Mucins as contrast agent targets for fluorescence-guided surgery of pancreatic cancer

Pancreatic cancer is difficult to resect due to its unique challenges, often leading to incomplete tumor resections. Fluorescence-guided surgery (FGS), also known as intraoperative molecular imaging and optical surgical navigation, is an intraoperative tool that can aid surgeons in complete tumor resection through an increased ability to detect the tumor. To target the tumor, FGS contrast agents rely on biomarkers aberrantly expressed in malignant tissue compared to normal tissue. These biomarkers allow clinicians to identify the tumor and its stage before surgical resection and provide a contrast agent target for intraoperative imaging. Mucins, a family of glycoproteins, are upregulated in malignant tissue compared to normal tissue. Therefore, these proteins may serve as biomarkers for surgical resection. Intraoperative imaging of mucin expression in pancreatic cancer can potentially increase the number of complete resections. While some mucins have been studied for FGS, the potential ability to function as a biomarker target extends to the entire mucin family. Therefore, mucins are attractive proteins to investigate more broadly as FGS biomarkers. This review summarizes the biomarker traits of mucins and their potential use in FGS for pancreatic cancer.

Biology and management of lobular endocervical glandular hyperplasia

AIM

Lobular endocervical glandular hyperplasia (LEGH) is a multicystic proliferative disorder of the uterine cervix. The aim of this review was to clarify the current understanding of this unique tumor.

METHOD

This article reviews the chronological progress of research regarding clinico-pathological and genetic aspects of LEGH and related cervical cystic diseases such as Nabothian cyst and adenocarcinoma of gastric type (GAS), using the literature and data from our institute. We also describe clinical management including preoperative diagnosis and adequate surgical/expectant treatment based on the biological features.

RESULTS

Recent studies revealed several unique aspects of LEGH, that is, (i) production of gastric mucin, (ii) symptomatic and histological similarity with minimal deviation adenocarcinoma (MDA), and (iii) frequent association with GAS, including MDA. These findings indicated that LEGH is a gastric metaplasia, as well as pre-cancerous neoplasia. For the preoperative diagnosis of LEGH, the combination of "cosmos" sign on magnetic resonance imaging, detection of gastric mucin, and lack of nuclear atypia on cytology is important. Cone biopsy is effective for pathological diagnosis. Simple hysterectomy is indicated as surgical treatment for LEGH; however, meticulous follow-up is also an option, especially for young patients, because the rate of malignant transformation was reported to be 1%-2%. For LEGH patients who selected follow-up, a worsening cytology and increase in lesion size were important signs of malignant change of LEGH for safe follow-up.

CONCLUSION

Proper understanding of the characteristics of LEGH is important for adequate management.

Abnormal B cell glycosylation in autoimmunity: A new potential treatment strategy

Systemic lupus erythematosus (SLE) and primary Sjögren’s syndrome (pSS) are two autoimmune diseases characterised by the production of pathogenic autoreactive antibodies. Their aetiology is poorly understood. Nevertheless, they have been shown to involve several factors, such as infections and epigenetic mechanisms. They also likely involve a physiological process known as glycosylation. Both SLE T cell markers and pSS-associated autoantibodies exhibit abnormal glycosylation. Such dysregulation suggests that defective glycosylation may also occur in B cells, thereby modifying their behaviour and reactivity. This study aimed to investigate B cell subset glycosylation in SLE, pSS and healthy donors and to extend the glycan profile to serum proteins and immunoglobulins. We used optimised lectin-based tests to demonstrate specific glycosylation profiles on B cell subsets that were specifically altered in both diseases. Compared to the healthy donor B cells, the SLE B cells exhibited hypofucosylation, whereas only the pSS B cells exhibited hyposialylation. Additionally, the SLE B lymphocytes had more galactose linked to N-acetylglucosamine or N-acetylgalactosamine (Gal-GlcNAc/Gal-GalNAc) residues on their cell surface markers. Interestingly, some similar alterations were observed in serum proteins, including immunoglobulins. These findings indicate that any perturbation of the natural glycosylation process in B cells could result in the development of pathogenic autoantibodies. The B cell glycoprofile can be established as a preferred biomarker for characterising pathologies and adapted therapeutics can be used for patients if there is a correlation between the extent of these alterations and the severity of the autoimmune diseases.

α1,4-linked N-acetylglucosamine suppresses gastric cancer development by inhibiting MUC1-mediated signaling

Gastric cancer is the second leading cause of cancer deaths worldwide, and more understanding of its molecular basis is urgently needed. Gastric gland mucin secreted from pyloric gland cells, mucous neck cells, and cardiac gland cells of the gastric mucosa harbors unique O‐glycans carrying terminal α1,4‐linked N‐acetylglucosamine (αGlcNAc) residues. We previously reported that αGlcNAc loss correlated positively with poor outcomes for patients with differentiated‐type gastric cancer. However, the molecular mechanisms underlying these outcomes remained poorly understood. Here, we examined the effects of upregulated αGlcNAc expression on malignant phenotypes of the differentiated‐type gastric cancer cell lines, AGS and MKN7. Upregulation of αGlcNAc following ectopic expression of its biosynthetic enzyme attenuated cell proliferation, motility, and invasiveness of AGS and MKN7 cells in vitro. Moreover, AGS cell tumorigenicity was significantly suppressed by αGlcNAc overexpression in a xenograft model. To define the molecular mechanisms underlying these phenotypes, we investigated αGlcNAc binding proteins in AGS cells and identified Mucin‐1 (MUC1) and podocalyxin. Both proteins were colocalized with αGlcNAc on human gastric cancer cells. We also found that αGlcNAc was bound to MUC1 in murine normal gastric mucosa. When we assessed the effects of αGlcNAc binding to MUC1, we found that αGlcNAc blocked galectin‐3 binding to MUC1, phosphorylation of the MUC1 C‐terminus, and recruitment of Src and β‐catenin to that C‐terminus. These results suggest that αGlcNAc regulates cancer cell phenotypes by dampening MUC1 signal transduction.

The malignant potential of pancreatic intraductal papillary mucinous neoplasm is reflected in expression levels of fucosylated glycans in α1 -acid glycoprotein

BACKGROUND

Pancreatic intraductal papillary mucinous neoplasm (IPMN) involves multiple histopathological stages from benign to malignant lesions. Further, a biomarker to diagnose the malignant IPMN (IPMC) is clinically relevant. Recently, we found that serum fucosylated α₁ -acid glycoprotein (fAGP) level markedly elevated along with disease progression in large cohorts of patients with various cancers.

METHODS

The fAGP level was retrospectively analyzed in preoperative sera from 109 patients with IPMN, and the clinical relevance of fAGP was compared with currently available predictors as standard.

RESULTS

The fAGP level in IPMC was found to be significantly higher than in benign IPMN (P=0.0012). At a cutoff value of 27.04 U/μg, its sensitivity, specificity, and accuracy for IPMC were determined to be 83.61, 65.96 and 75.93%, respectively. Multivariate analyses revealed that the fAGP level was the only independent risk factor for predicting IPMC. Additionally, a combination of the fAGP level and ¹⁸ F-fluorodeoxyglucose uptake on the PET/CT imaging in the lesions seemed to offer the best diagnosis of IPMN. Accordingly, 27 of the 28 patients who were positive in both tests had IPMC, while patients who are negative had benign IPMN.

CONCLUSIONS

The fAGP level appeared to be a relevant biomarker for malignant potential of IPMN.

Glycosylation of MUC6 by α1,4-linked N-acetylglucosamine enhances suppression of pancreatic cancer malignancy

Biomarkers for early diagnosis of pancreatic cancer are greatly needed, as the high fatality of this cancer is in part due to delayed detection. α1,4‐linked N‐acetylglucosamine (αGlcNAc), a unique O‐glycan specific to gastric gland mucus, is biosynthesized by α1,4‐N‐acetylglucosaminyltransferase (α4GnT) and primarily bound at the terminal glycosylated residue to scaffold protein MUC6. We previously reported that αGlcNAc expression decreases at early stages of neoplastic pancreatic lesions, followed by decreased MUC6 expression, although functional effects of these outcomes were unknown. Here, we ectopically expressed α4GnT, the αGlcNAc biosynthetic enzyme, together with MUC6 in the human pancreatic cancer cell lines MIA PaCa‐2 and PANC‐1, neither of which expresses α4GnT and MUC6. We observed significantly suppressed proliferation in both lines following coexpression of α4GnT and MUC6. Moreover, cellular motility decreased following MUC6 ectopic expression, an effect enhanced by cotransduction with α4GnT. MUC6 expression also attenuated invasiveness of both lines relative to controls, and this effect was also enhanced by additional α4GnT expression. We found αGlcNAc‐bound MUC6 formed a complex with trefoil factor 2. Furthermore, analysis of survival curves of patients with pancreatic ductal adenocarcinoma using a gene expression database showed that samples marked by higher A4GNT or MUC6 mRNA levels were associated with relatively favorable prognosis. These results strongly suggest that αGlcNAc and MUC6 function as tumor suppressors in pancreatic cancer and that decreased expression of both may serve as a biomarker of tumor progression to pancreatic cancer.

Decreased Gastric Gland Mucin-specific O-glycans Are Involved in the Progression of Ovarian Primary Mucinous Tumours

Ovarian primary mucinous tumours (OPMTs) show an adenoma–borderline–carcinoma sequence with gastrointestinal metaplasia. Gastric gland mucin-specific O-glycans are unique with an α1,4-linked N-acetylglucosamine (αGlcNAc) residue attached to mucin 6 (MUC6). Although αGlcNAc is expected to be expressed in OPMTs, the relationship between αGlcNAc expression and OPMT progression remains unknown. Here, we analysed 104 areas of benign mucinous tumours (benign), 55 areas of borderline mucinous tumours (borderline), and 18 areas of malignant mucinous tumours (malignant) to investigate the expression patterns of αGlcNAc, mucin 2 (MUC2), mucin 5AC (MUC5AC), and MUC6 during the progression of OPMT from benign to malignant. MUC5AC expression was observed in all areas. The frequencies of MUC6- and αGlcNAc-positive areas were decreased with tumour progression. In particular, the decrease in αGlcNAc-positive areas was remarkable. Furthermore, αGlcNAc expression was lower than MUC6 expression at all grades (benign, p < 0.0001; borderline, p = 0.0014; malignant, p = 0.0039). Conversely, there was no difference in the expression frequency or level of MUC2 among the three grades. These results suggest that decreased expression of αGlcNAc relative to MUC6 occurs early in tumour development and marks the initiation of OPMT progression.

Phenotype characteristics of gastric epithelial mucus in patients with different gastric diseases: from superficial gastritis to gastric cancer

Background

Gastric gland mucin is important for maintaining the basic function of the gastric mucosa, protecting it from foreign substances and reducing the occurrence of gastric diseases. Exploring the phenotype of gastric gland mucus changes during the progression of gastric disease is of great clinical significance.

Methods

A total of 483 patients with different gastric diseases were collected in this study, including 82 superficial gastritis (SG), 81 atrophic gastritis (AG), 168 dysplasia (GD), and 152 gastric cancer (GC). Mucin staining was performed using HID-ABpH2.5-PAS method and was further grouped according to the mucin coloration.

Results

The phenotypic characteristics of mucin during disease progression were divided into neutral, acidic, and mucus-free types. Furthermore, acidic mucus can be divided into type I, type II, and type III. The SG group was dominated by neutral mucus (100%), and the AG was dominated by acid mucus (81.48%), which gradually increased with the severity of atrophy (P < 0.05). The GD and GC groups were dominated by mucus-free (43.45%, 78.29%), and as the degree of GD worsened, neutral and acidic mucus gradually decreased and mucus-free increased (P < 0.001). From the SG, AG, GD, and GC progression, neutral and acidic mucus gradually decreased, and mucus- free gradually increased. Acidic mucin revealed that type III (red-brown black) mucin was predominant in AG, GD, and GC, and increased with the degree of AG, GD, as well as the biological behavior of GC. In the lesion adjacent to high-grade GD or GC, type III acid mucin is predominant.

Conclusion

There were three mucin phenotypes in the process of gastric diseases. With the disease progression, the trend of phenotypic change was that neutral and acidic mucus gradually decreased and mucus-free increased. The appearance of type III mucin suggested a relatively serious phase of gastric diseases and may be a more suitable candidate for follow-up monitoring of patients with GC risk.

Diffuse MIST1 expression and decreased α1,4-linked N-acetylglucosamine (αGlcNAc) glycosylation on MUC6 are distinct hallmarks for gastric neoplasms showing oxyntic gland differentiation

AIMS

Gastric neoplasms showing oxyntic gland differentiation (GAOGs) constitute a gastric neoplasm subtype that shows low atypia, thus similar to non-neoplastic gastric oxyntic glands. Therefore, their diagnosis in biopsy specimens is difficult. GAOGs were first described in 2007, and introduced in the latest World Health Organization classification book as gastric adenocarcinoma of the fundic gland type (GA-FG) and oxyntic gland adenoma. Previously, we assessed α1,4-linked N-acetylglucosamine (αGlcNAc) residues attached to the MUC6 scaffold in gastric neoplasms, and observed decreased αGlcNAc glycosylation in both differentiated-type gastric cancer and high-grade pyloric gland adenoma (PGA), a gastric cancer precursor. GA-FG and PGA often harbour the same mutations. However, the αGlcNAc status in GAOGs remained unknown. To elucidate αGlcNAc expression in GAOGs, we performed the study.

METHODS AND RESULTS

We assessed the expression of αGlcNAc; the mucin markers MUC6, MUC5AC, and MUC2; the gastric gland cell markers MIST1, pepsinogen 1 (PG1), H/K-ATPase and chromogranin-A (CGA); and the proliferation marker Ki67 in 13 GAOG lesions. All 13 (100%) were MUC6-positive, whereas 10 (76.2%) were αGlcNAc-negative. Moreover, all 13 (100%) were MIST1- and PG1-positive, three (23.1%) were MUC5AC-positive, four (30.8%) were H/K-ATPase-positive, and one (7.7%) was CGA-positive.

CONCLUSIONS

GAOGs frequently lost αGlcNAc residues on MUC6, but expressed the gastric gland progenitor marker MIST1 and aberrantly expressed various types of gastric gland cell lineage marker, suggestive of immature differentiation to gastric gland cells. Thus, diffuse MIST1 positivity and decreased αGlcNAc glycosylation on MUC6-positive cells could serve as important biomarkers for the histopathological diagnosis of GAOG.

Establishment of a 1, 4, 7, 10-tetraazacyclododecane-1,4,7,10-tetraacetic acid mono-N-hydroxysuccinimide ester (DOTA-NHS-ester) based lectin microarray for efficiently detecting serum glycans in gastric cancers

Development of cancers is involved in changes of a variety of glycans. Lectin microarray is one of the most powerful methodologies for investigation of glycan alterations in biological samples with its advantages of high through-put, selectivity and specificity of the technique. However, utilization of lectin microarrays available commercially keeps of great challenges. In this study, we took use of the molecular self-assembled monolayer technique to modify a gold surface with the reagent 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid mono-N-hydroxysuccinimide ester (DOTA-NHS-ester) in combination with 16-amino-1-hexadecanethiol hydrochloride. Cross-linking effect of DOTA-NHS-ester is brought about via activating three -OH ends to three terminals of succinylimidines, making selective binding of the terminal amino groups in proteins possible. We immobilized ten commercial lectins on the platform and measured changes of serum lectin-matched glycans in patients with gastric cancer. The results demonstrated that this biochip modification platform conferred impressive chemical surface stabilization, sensitivity and geometric images. We observed that all the serum glycans tested in the patients were significantly higher than those in the controls (P < 0.05). The biochip would provide a versatile platform for investigation of potential glycan biomarkers in making tumor diagnosis decision and analyzing escape of tumors from immunity.

Analysis of A4gnt Knockout Mice Reveals an Essential Role for Gastric Sulfomucins in Preventing Gastritis Cystica Profunda

Gastric adenocarcinoma cells secrete sulfomucins, but their role in gastric tumorigenesis remains unclear. To address that question, we generated A4gnt/Chst4 double-knockout (DKO) mice by crossing A4gnt knockout (KO) mice, which spontaneously develop gastric adenocarcinoma, with Chst4 KO mice, which are deficient in the sulfotransferase GlcNAc6ST-2. A4gnt/Chst4 DKO mice lack gastric sulfomucins but developed gastric adenocarcinoma. Unexpectedly, severe gastric erosion occurred in A4gnt/Chst4 DKO mice at as early as 3 weeks of age, and with aging these lesions were accompanied by gastritis cystica profunda (GCP). Cxcl1, Cxcl5, Ccl2, and Cxcr2 transcripts in gastric mucosa of 5-week-old A4gnt/Chst4 DKO mice exhibiting both hyperplasia and severe erosion were significantly upregulated relative to age-matched A4gnt KO mice, which showed hyperplasia alone. However, upregulation of these genes disappeared in 50-week-old A4gnt/Chst4 DKO mice exhibiting high-grade dysplasia/adenocarcinoma and GCP. Moreover, Cxcl1 and Cxcr2 were downregulated in A4gnt/Chst4 DKO mice relative to age-matched A4gnt KO mice exhibiting adenocarcinoma alone. These combined results indicate that the presence of sulfomucins prevents severe gastric erosion followed by GCP in A4gnt KO mice by transiently regulating a set of inflammation-related genes, Cxcl1, Cxcl5, Ccl2, and Cxcr2 at 5 weeks of age, although sulfomucins were not directly associated with gastric cancer development.

αGlcNAc and its catalyst α4GnT are diagnostic and prognostic markers in uterine cervical tumor, gastric type

Cervical adenocarcinoma, gastric type (GAS) is not associated with human papilloma virus (HPV) infection. GAS patients prognoses are significantly worse compared with cervical adenocarcinoma associated with HPV infection, as their tumors exhibit resistance to conventional chemotherapy and radiotherapy. GAS is often associated with lobular endocervical glandular hyperplasia (LEGH), which is regarded as a precursor to GAS in the latest WHO classification. Recently, we reported that a decrease in expression of terminal α1,4-linked N-acetylglucosamine (αGlcNAc) relative to that of MUC6 was already apparent in atypical LEGH in the LEGH-GAS sequence. Here, we analyzed expression of α1,4-N-acetylglucosaminyltransferase (α4GnT), the sole enzyme catalyzing αGlcNAc biosynthesis, and that of αGlcNAc and MUC6 in cases representing non-neoplastic endocervical gland (NNEG) (11 cases), LEGH (26 cases) and GAS (12 cases). α4GnT protein was detected in a "dot-like" pattern, indicating localization in the Golgi apparatus in all 26 LEGH cases and 5 of 12 GAS cases. α4GnT- and αGlcNAc-positive cells largely overlapped, suggesting that α4GnT gene expression regulates αGlcNAc biosynthesis. Interestingly, all NNEG cases were negative for α4GnT and αGlcNAc expression, but 7 of 11 NNEG and all LEGH cases were MUC6-positive. In GAS cases, patients whose tumors were α4GnT- and αGlcNAc-positive had more favorable prognosis than others. Multivariate analysis revealed that positive expressions of α4GnT and αGlcNAc were independent prognostic indicators. These results indicate that α4GnT and αGlcNAc could serve as useful markers not only to distinguish LEGH from NNEG but to evaluate prognoses of GAS patients.

Gastric gland mucin-specific O-glycan expression decreases as tumor cells progress from lobular endocervical gland hyperplasia to cervical mucinous carcinoma, gastric type

Gastric gland mucin-specific O-glycans are unique in having α1,4-linked N-acetylglucosamine (αGlcNAc) attached to MUC6. We previously reported decreased expression of αGlcNAc relative to MUC6 in gastric and pancreatic neoplasms, but its significance in cervical glandular lesions remained unclear. Here, we analyzed MUC5AC, MUC6, αGlcNAc, and p16 expression in 9 lesions of mucinous carcinoma, gastric type with minimal deviation adenocarcinoma (GAS-MDA), 5 of GAS with nonMDA (GAS-nonMDA), 14 of typical lobular endocervical gland hyperplasia (LEGH), and 5 of atypical LEGH (33 total lesions). All 33 were MUC5AC-positive. Moreover, all 14 typical LEGH, 5 atypical LEGH, 8 of 9 GAS-MDA, and 3 of 5 GAS-nonMDA were MUC6-positive. All 14 typical LEGH, 2 of 5 atypical LEGH, 3 of 9 GAS-MDA, and 1 of 5 GAS-nonMDA were αGlcNAc-positive. The proportion of αGlcNAc-positive atypical LEGH or GAS-MDA or GAS-nonMDA lesions was significantly smaller than that seen in typical LEGH lesions (P < 0.001 and P < 0.01, respectively). Of 33 lesions, 32 were p16-negative. Furthermore, when we evaluated MUC6 and αGlcNAc immunoreactivity semi-quantitatively in all 33 lesions, in typical LEGH and GAS-MDA, the immunohistochemical score for αGlcNAc was significantly lower than that for MUC6 (P < 0.01). We did not observe significantly decreased αGlcNAc expression relative to MUC6 in typical LEGH lesions. These studies suggest that αGlcNAc expression decreases as typical LEGH progresses to GAS. Given the difficulty in distinguishing MDA and atypical LEGH from typical LEGH in H.E. staining, we propose that immunohistochemical analysis of αGlcNAc and MUC6 could be useful.