The O-GalNAcylating enzyme GALNT5 mediates carcinogenesis and progression of cholangiocarcinoma via activation of AKT/ERK signaling

Abstract

Mucin type O-glycosylation is a posttranslational modification of membrane and secretory proteins. Transferring of N-acetylgalactosamine, the first sugar of O-glycosylation, is catalyzed by one of the 20 isoforms of polypeptide N-acetylgalactosaminyltransferases (GALNTs). In this study, Vicia villosa lectin (VVL), a lectin that recognizes O-GalNAcylated glycans, was used to detect VVL-binding glycans (VBGs) in cholangiocarcinoma (CCA). The elevation of VBGs in tumor tissues of the liver fluke associated with CCA from hamsters and patients was noted. VBGs were detected in hyperplastic/dysplastic bile ducts and CCA but not in normal biliary epithelia and hepatocytes, indicating the association of VBGs with CCA development and progression. GALNT5 was shown to be the major isoform found in human CCA cell lines with high VBG expression. Suppression of GALNT5 expression using siRNA significantly reduced VBG expression, signifying the connection of GALNT5 and VBGs observed. Knocked-down GALNT5 expression considerably inhibited proliferation, migration and invasion of CCA cells. Increased expression of GALNT5 using pcDNA3.1-GALNT5 expression vector induced invasive phenotypes in CCA cells with low GALNT5 expression. Increasing of claudin-1 and decreasing of slug and vimentin expression together with inactivation of Akt/Erk signaling were noted in GALNT5 knocked-down cells. These observations were reversed in GALNT5 over-expressing cells. GALNT5-modulated progression of CCA cells was shown to be, in part, via GALNT5-mediated autocrine/paracrine factors that stimulated activations of Akt/Erk signaling and the epithelial to mesenchymal transition process. GALNT5 and its O-GalNAcylated products may have important roles in promoting progression of CCA and could possibly be novel targets for treatment of metastatic CCA.

Epithelial–Mesenchymal Transition in Liver Fluke-Induced Cholangiocarcinoma

“…GalNAc transferase 5 (GALNT5) was a major enzyme in liver fluke-associated human CCA cell lines with high O-GalNAcylated glycan. Knockdown of GALNT5 expression inhibited migration and invasion of CCA cell lines via an increase in claudin-1 and a decrease in slug and vimentin expression [27]. A study on TNFα's effort on EMT markers Zeb2 and S100A4 supported involvement of EMT regulation in liver fluke-associated CCA [28].…”

Wnt/β-catenin signaling as an emerging potential key pharmacological target in cholangiocarcinoma

“…External-beam radiation therapy (EBRT) has also emerged as a valuable alternative for patients with localized, unresectable intrahepatic CCA [16]. The different new molecular targets that have been exploited in the preclinical and clinical trials for the management of CCA include fibroblast growth factor receptors [17], heat-shock protein 90 [18], tyrosine-kinase [19], ROS1 kinase fusion proteins [20], Akt/Erk signaling [21], SOX17, a transcription factor [22], Maternal Embryonic Leucine Zipper Kinase (MELK), a protooncogene [23] and mesothelin [24] etc. However, the development of drugs based on these molecular targets is still in the different stages of preclinical or clinical trials.…”

Glycans: potential therapeutic targets for cholangiocarcinoma and their therapeutic and diagnostic implications

“…N-acetyl galactosamine (GalNAc)-containing glycans were drastically increased in CCA compared with the normal bile ducts in adjacent tissues [3][4][5]. The O-linked GalNAc glycan was found to regulate CCA metastasis via Akt/Erk signaling pathway.…”

“…The O-linked GalNAc glycan was found to regulate CCA metastasis via Akt/Erk signaling pathway. Modulation of GalNAc modification by knockdown or overexpression of GalNAc-transferase (GalNT)-5 was shown to affect the metastatic ability of CCA cells [5].…”

“…The information obtained through glycomic analysis using lectin-based approaches showed that many GalNAc-binding lectins; including Wisteria floribunda agglutinin (WFA) [4], Sophora japonica agglutinin (SJA) [3], and Vicia villosa lectin (VVL) [5]; exhibited a strong reactivity with preneoplastic bile ducts and CCA, but not normal bile ducts, suggesting their specificity to bile duct pathology. The glycans comprised in mucin glycoproteins are possibly been shredded and secreted into serum and bile of CCA patients.…”