Clinicopathological significance of core 3 O-glycan synthetic enzyme, β1,3-N-acetylglucosaminyltransferase 6 in pancreatic ductal adenocarcinoma

Cancer snap-shots: Biochemistry and glycopathology of O-glycans: A review

Cancer pathogenesis is strongly linked to the qualitative and quantitative alteration of the cell surface glycans, that are glycosidically linked to proteins and lipids. Glycans that are covalently linked to the polypeptide backbone of a protein through nitrogen or oxygen, are known as N-glycans or O-glycans, respectively. Although the role of glycans in the expression, physiology, and communication of cells is well documented, the function of these glycans in tumor biology is not fully elucidated. In this context, current review summarizes biosynthesis, modifications and pathological implications of O-glycans The review also highlights illustrative examples of cancer types modulated by aberrant O-glycosylation. Related O-glycans like Thomsen-nouveau (Tn), Thomsen-Friedenreich (TF), Lewisa/x, Lewisb/y, sialyl Lewisa/x and some other O-glycans are discussed in detail. Since, the overexpression of O-glycans are attributed to the aggressiveness and metastatic behavior of cancer cells, the current review attempts to understand the relation between metastasis and O-glycans.

Correlation of Vein-Rich Tumor Microenvironment of Intrahepatic Cholangiocarcinoma With Tertiary Lymphoid Structures and Patient Outcome

Intrahepatic cholangiocarcinoma (iCCA) is an aggressive cancer composed of large-duct and small-duct types. Understanding the tumor immune microenvironment and its related vascular system is important for developing novel and efficient therapies. We focused on tertiary lymphoid structure (TLS) as a hallmark of antitumor immunity and investigated the clinicopathologic significance of TLSs and the influence of vascular microenvironment on TLS formation in iCCAs. We examined 261 iCCA cases clinicopathologically and analyzed the vascular system using immunohistochemistry. Single-cell (102,685 cells) and bulk RNA (33 iCCA cases) sequencing analyses were performed using data sets downloaded from public databases, and endothelial cell characteristics in iCCA tissues and functional networks related to the tumor microenvironment were bioinformatically examined. High densities of both intratumoral and peritumoral TLSs were significantly associated with prolonged survival only in large-duct-type iCCA. Multivariate analyses showed that peritumoral TLS was a prognostic factor for the large-duct type. TLS-rich iCCA had a significantly higher vein density and tumor-infiltrating T-cell count than TLS-poor iCCA. Both the presence of TLSs and high vein endothelial cells in iCCA tissues were significantly associated with molecular networks representing active immune responses in transcriptomic analysis. Vein density was a prognostic factor in patients with large-duct and small-duct types. This suggests that TLS formation is involved in a microenvironment with high vein density, which represents an antitumor-directed immune microenvironment.

Droplet-Based Glycan and RNA Sequencing for Profiling the Distinct Cellular Glyco-States in Single Cells

Plate-based single-cell glycan and RNA sequencing (scGR-seq) is previously developed to realize the integrated analysis of glycome and transcriptome in single cells. However, the sample size is limited to only a few hundred cells. Here, a droplet-based scGR-seq is developed to address this issue by adopting a 10x Chromium platform to simultaneously profile ten thousand cells' glycome and transcriptome in single cells. To establish droplet-based scGR-seq, a comparative analysis of two distinct cell lines is performed: pancreatic ductal adenocarcinoma cells and normal pancreatic duct cells. Droplet-based scGR-seq revealed distinct glycan profiles between the two cell lines that showed a strong correlation with the results obtained by flow cytometry. Next, droplet-based scGR-seq is applied to a more complex sample: peripheral blood mononuclear cells (PBMC) containing various immune cells. The method can systematically map the glycan signature for each immune cell in PBMC as well as glycan alterations by cell lineage. Prediction of the association between the glycan expression and the gene expression using regression analysis ultimately leads to the identification of a glycan epitope that impacts cellular functions. In conclusion, the droplet-based scGR-seq realizes the high-throughput profiling of the distinct cellular glyco-states in single cells.

IGF2BP2 promotes pancreatic carcinoma progression by enhancing the stability of B3GNT6 mRNA via m6A methylation

BACKGROUND

Pancreatic carcinoma (PC) is a highly lethal cancer with an increasing mortality rate, its five-year survival rate is only approximately 4%. N6-methyladenosine (m6A) modification is the most common posttranscriptional modification of RNA, it could affect tumor formation by regulating m6A modifications in the mRNA of key oncogenes or tumor suppressor genes. However, its role in PC remains unclear.

METHODS

We combined bioinformatic analysis with in vitro and in vivo experiments to investigate the expression profile of methylation modulators and identify key m6A regulators in the progression of PC. Further study focused on exploring the target genes binding to the regulators through RIP and immunofluorescence staining experiment.

RESULTS

TCGA and Gene Expression Omnibus (GEO) analyses revealed an overall increasing trend in the expression of m6A regulators in PC, and consensus clustering analysis of m6A modification showed that the expression of regulators was negatively correlated with the survival rate. LASSO-Cox regression analysis revealed that IGF2BP2, METTL3, ALKBH5 and KIAA1429 were associated with hazard ratios (HR), but only IGF2BP2 was sufficiently appropriate for the m6A survival prognosis model. The IHC and WB results verified high protein expression of IGF2BP2 in PC, and IGF2BP2 knockdown inhibited the proliferation and migration of PC cells. We predicted and verified B3GNT6 was observably regulated by IGF2BP2 via RIP assays. In addition, IF staining confirmed the co-expression of IGF2BP2 and B3GNT6. The tumor-promoting effect of IGF2BP2 and its co-expression with B3GNT6 were verified in an animal model.

CONCLUSIONS

Elevated m6A levels promote PC progression. IGF2BP2 is a credible marker and modulates B3GNT6 mRNA stability, indicating that IGF2BP2 is a potential prognostic marker and therapeutic target in PC progression.

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.

Neoadjuvant therapy alters the collagen architecture of pancreatic cancer tissue via Ephrin-A5

BACKGROUND

The treatment of pancreatic cancer (PDAC) remains clinically challenging, and neoadjuvant therapy (NAT) offers down staging and improved surgical resectability. Abundant fibrous stroma is involved in malignant characteristic of PDAC. We aimed to investigate tissue remodelling, particularly the alteration of the collagen architecture of the PDAC microenvironment by NAT.

METHODS

We analysed the alteration of collagen and gene expression profiles in PDAC tissues after NAT. Additionally, we examined the biological role of Ephrin-A5 using primary cultured cancer-associated fibroblasts (CAFs).

RESULTS

The expression of type I, III, IV, and V collagen was reduced in PDAC tissues after effective NAT. The bioinformatics approach provided comprehensive insights into NAT-induced matrix remodelling, which showed Ephrin-A signalling as a likely pathway and Ephrin-A5 (encoded by EFNA5) as a crucial ligand. Effective NAT reduced the number of Ephrin-A5⁺ cells, which were mainly CAFs; this inversely correlated with the clinical tumour shrinkage rate. Experimental exposure to radiation and chemotherapeutic agents suppressed proliferation, EFNA5 expression, and collagen synthesis in CAFs. Forced EFNA5 expression altered CAF collagen gene profiles similar to those found in PDAC tissues after NAT.

CONCLUSION

These results suggest that effective NAT changes the extracellular matrix with collagen profiles through CAFs and their Ephrin-A5 expression.

Application of Proteomics in Pancreatic Ductal Adenocarcinoma Biomarker Investigations: A Review

Pancreatic ductal adenocarcinoma (PDAC), a highly aggressive malignancy with a poor prognosis is usually detected at the advanced stage of the disease. The only US Food and Drug Administration-approved biomarker that is available for PDAC, CA 19-9, is most useful in monitoring treatment response among PDAC patients rather than for early detection. Moreover, when CA 19-9 is solely used for diagnostic purposes, it has only a recorded sensitivity of 79% and specificity of 82% in symptomatic individuals. Therefore, there is an urgent need to identify reliable biomarkers for diagnosis (specifically for the early diagnosis), ascertain prognosis as well as to monitor treatment response and tumour recurrence of PDAC. In recent years, proteomic technologies are growing exponentially at an accelerated rate for a wide range of applications in cancer research. In this review, we discussed the current status of biomarker research for PDAC using various proteomic technologies. This review will explore the potential perspective for understanding and identifying the unique alterations in protein expressions that could prove beneficial in discovering new robust biomarkers to detect PDAC at an early stage, ascertain prognosis of patients with the disease in addition to monitoring treatment response and tumour recurrence of patients.

Novel insights into immunohistochemical analysis for diagnosing serous neoplasm of the pancreas: aquaporin 1, stereocilin, and transmembrane protein 255B

AIMS

Serous (cystic) neoplasm (SCN) of the pancreas is generally benign, and surgical treatment is recommended in only a limited number of cases. To avoid unnecessary surgery, an accurate diagnosis of SCN is essential. In the present study, we aimed to identify new immunohistochemical markers with which to distinguish SCN from other tumours.

METHODS AND RESULTS

We compared the comprehensive gene expression profiles of SCN with those of normal pancreas and pancreatic ductal adenocarcinoma (PDAC). We selected the candidate molecules that were up-regulated in SCN, were minimally expressed or unexpressed in PDAC, and had specific and available antibodies suitable for immunohistochemistry, and then analysed their immunohistochemical expression in various tumours. We selected aquaporin 1 (AQP1), stereocilin (STRC), fibroblast growth factor receptor 3 (FGFR3), and transmembrane protein 255B (TMEM255B), which were diffusely expressed in SCN cells in 79%, 100%, 100% and 100% of SCN cases. AQP1 was not expressed in other tumours, except in 20% of mucinous cystic neoplasms (MCNs) and 19% of PDACs. STRC was rarely expressed in MCNs, neuroendocrine neoplasms (NENs), and PDACs. FGFR3 was expressed in 31% of intraductal papillary mucinous neoplasms (IPMNs), 50% of intraductal oncocytic papillary neoplasms, 40% of NENs, 30% of acinar cell carcinomas, 40% of solid pseudopapillary neoplasms, and 52% of PDACs. TMEM255B was not expressed in the other tumours, except in 50% of MCNs, 80% of gastric-subtype IPMNs, and 29% of PDACs. All antigens were usually expressed in a small proportion of cells when they were positive in tumours other than SCN.

CONCLUSIONS

These findings indicate that AQP1 and STRC, and potentially TMEM255B, may act as SCN markers.

Association between the expression of core 3 synthase and survival outcomes of patients with cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly aggressive and metastatic type of malignant carcinoma that is associated with high mortality rates and is difficult to detect at early stages. Core 3 structure is a mucin-type O-glycans synthesized by β1,3-N-acetylglucosaminyltransferase 6 (core 3 synthase), which plays an important role in the digestive system, in particular gastrointestinal goblet cells. It has been reported that core 3 synthase-expressing cells show lower migratory and invasive rates, and lower metastatic activity. A immunohistochemical study also showed that this enzyme was expressed in normal epithelial cells of the colon, but completely disappeared in colorectal cancer cells. The present study aimed to identify biomarkers that could be used to predict the prognosis of patients with CCA. Pathological specimens of 185 CCA tissues were immunohistochemically stained with two antibodies, G8-144 and MECA-79, which recognize core 3 synthase and 6-sulfated N-acetyllactosamine on the extended core-1 O-glycans, respectively. The association between G8-144 or MECA-79 positivity and patient prognosis was statistically analyzed. Positive expression of G8-144 was associated with improved prognosis in patients with distal CCA (dCCA). Patients with dCCA positive for G8-144 showed lower mortality rates than those with negative expression. However, the positive expression of MECA-79 was associated with CCA progression and metastasis, indicating that it is a poor prognostic marker for CCA. In conclusion, as both antibodies resulted in mirror-image staining, the involvement of G8-144 and MECA-79 in O-glycan synthesis could be considered as potential favorable and unfavorable biomarkers, respectively, for CCA prognosis.

Mucins as anti-cancer targets: perspectives of the glycobiologist

Mucins are highly O-glycosylated glycoproteins that carry a heterogenous variety of O-glycan structures. Tumor cells tend to overexpress specific mucins, such as the cell surface mucins MUC1 and MUC4 that are engaged in signaling and cell growth, and exhibit abnormal glycosylation. In particular, the Tn and T antigens and their sialylated forms are common in cancer mucins. We review herein methods chosen to use cancer-associated glycans and mucins as targets for the design of anti-cancer immunotherapies. Mucin peptides from the glycosylated and transmembrane domains have been combined with immune-stimulating adjuvants in a wide variety of approaches to produce anti-tumor antibodies and vaccines. These mucin conjugates have been tested on cancer cells in vitro and in mice with significant successes in stimulating anti-tumor responses. The clinical trials in humans, however, have shown limited success in extending survival. It seems critical that the individual-specific epitope expression of cancer mucins is considered in future therapies to result in lasting anti-tumor responses.