Epithelial-mesenchymal transition (EMT) is pivotal in the initiation and development of cancer cell metastasis. We observed that the abundance of glycosphingolipids (GSLs), especially ganglioside... Show moreEpithelial-mesenchymal transition (EMT) is pivotal in the initiation and development of cancer cell metastasis. We observed that the abundance of glycosphingolipids (GSLs), especially ganglioside subtypes, decreased significantly during TGF-beta-induced EMT in NMuMG mouse mammary epithelial cells and A549 human lung adenocarcinoma cells. Transcriptional profiling showed that TGF-beta/SMAD response genes and EMT signatures were strongly enriched in NMuMG cells, along with depletion of UDP-glucose ceramide glucosyltransferase (UGCG), the enzyme that catalyzes the initial step in GSL biosynthesis. Consistent with this finding, genetic or pharmacological inhibition of UGCG promoted TGF-beta signaling and TGF-beta-induced EMT. UGCG inhibition promoted A549 cell migration, extravasation in the zebrafish xenograft model, and metastasis in mice. Mechanistically, GSLs inhibited TGF-beta signaling by promoting lipid raft localization of the TGF-beta type I receptor (T beta RI) and by increasing T beta RI ubiquitination and degradation. Importantly, we identified ST3GAL5-synthesized a-series gangliosides as the main GSL subtype involved in inhibition of TGF-beta signaling and TGF-beta-induced EMT in A549 cells. Notably, ST3GAL5 is weakly expressed in lung cancer tissues compared to adjacent nonmalignant tissues, and its expression correlates with good prognosis. Show less
Aberrant expression of certain glycosphingolipids (GSLs) is associated withthe differentiation of acute myeloid leukemia (AML) cells. However, the expressionpatterns of GSLs in AML are still poorly... Show moreAberrant expression of certain glycosphingolipids (GSLs) is associated withthe differentiation of acute myeloid leukemia (AML) cells. However, the expressionpatterns of GSLs in AML are still poorly explored because of their complexity, the presenceof multiple isomeric structures, and tedious analytical procedures. In this study, weperformed an in-depth GSL glycan analysis of 19 AML cell lines using porous graphitizedcarbon liquid chromatography-mass spectrometry revealing strikingly different GSL glycanprofiles between the various AML cell lines. The cell lines of the M6 subtype showed a highexpression of gangliosides with alpha 2,3-sialylation and Neu5Gc, while the M2 and M5subtypes were characterized by high expression of (neo)lacto-series glycans and Lewis A/Xantigens. Integrated analysis of glycomics and available transcriptomics data revealed theassociation of GSL glycan abundances with the transcriptomics expression of certainglycosyltransferases (GTs) and transcription factors (TFs). In addition, correlations werefound between specific GTs and TFs. Our data reveal TFsGATA2,GATA1, andRUNX1as candidate inducers of the expression of gangliosides and sialylation via regulation of the GTsST3GAL2andST8SIA1.Inconclusion, we show that GSL glycan expression levels are associated with hematopoietic AML classifications and TF and GT geneexpression. Further research is needed to dissect the regulation of GSL expression and its role in hematopoiesis and associated malignancies. Show less
Zhang, J.; Dijke, P. ten; Wuhrer, M.; Zhang, T. 2020
Glycosylation is a common posttranslational modification on membrane-associated and secreted proteins that is of pivotal importance for regulating cell functions. Aberrant glycosylation can lead to... Show moreGlycosylation is a common posttranslational modification on membrane-associated and secreted proteins that is of pivotal importance for regulating cell functions. Aberrant glycosylation can lead to uncontrolled cell proliferation, cell-matrix interactions, migration and differentiation, and has been shown to be involved in cancer and other diseases. The epithelial-to-mesenchymal transition is a key step in the metastatic process by which cancer cells gain the ability to invade tissues and extravasate into the bloodstream. This cellular transformation process, which is associated by morphological change, loss of epithelial traits and gain of mesenchymal markers, is triggered by the secreted cytokine transforming growth factor-beta (TGF-beta). TGF-beta bioactivity is carefully regulated, and its effects on cells are mediated by its receptors on the cell surface. In this review, we first provide a brief overview of major types of glycans, namely,N-glycans,O-glycans, glycosphingolipids and glycosaminoglycans that are involved in cancer progression. Thereafter, we summarize studies on how the glycosylation of TGF-beta signaling components regulates TGF-beta secretion, bioavailability and TGF-beta receptor function. Then, we review glycosylation changes associated with TGF-beta-induced epithelial-to-mesenchymal transition in cancer. Identifying and understanding the mechanisms by which glycosylation affects TGF-beta signaling and downstream biological responses will facilitate the identification of glycans as biomarkers and enable novel therapeutic approaches. Show less
