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Previous studies demonstrated that certain glycosphingolipids (GSL5) are involved in various cell functions, such as cell growth and motility. Recent studies showed changes in GSL expression during differentiation of human embryonic stem cells; however, little is known about expression profiles of GSLs in cancer stem cells (CSC5). CSC5 are a small subpopulation in cancer and are proposed as cancer-initiating cells, have been shown to be resistant to numerous chemotherapies, and may cause cancer recurrence. Here, we analyzed GSL5 expressed in human breast CSC5 by applying a CSC model induced through epithelial-mesenchymal transition, using mass spectrometry, TLC immunostaining, and cell staining. We found that (I) Fuc-(n)Lc4Cer and Gb3Cer were drastically reduced in CSCs, whereas GD2, GD3, GM2, and GOla were greatly increased in CSCs; (ii) among various glycosyltransferases tested, mRNA levels for ST3GAL5, B4GALNT1, ST8SIA1, and ST3GAL2 were increased in CSCs, which could explain the increased expression of GD3, GD2, GM2, and GD1a in CSC5; (iii) the majority of GD2+ cells and GD3+ cells were detected in the CD44hi/CD2410 cell population; and (iv) knockdown of ST8SIA1 and B4GALNT1 significantly reduced the expression of GD2 and GD3 and caused a phenotype change from CSC to a non-CSC, which was detected by reduced mammosphere formation and cell motility. Our results provide insight into GSL profiles in human breast CSC5, indicate a functional role of GD2 and GD3 in CSCs, and suggest a possible novel approach in targeting human breast CSCs to interfere with cancer recurrence. [ABSTRACT FROM AUTHOR]

Epithelial-to-mesenchymal cell transition (EMT) is a basic process in embryonic development and cancer progression. The present study demonstrates involvement of glycosphingolipids (GSLs) in the EMT process by using normal murine mammary gland NMuMG, human normal bladder HCV29, and human mammary carcinoma MCF7 cells. Treatment of these cells with D-threo-1 -(3'.4'-ethylenedioxy)phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (EtDO-P4), the glucosylceramide (GicCer) synthase inhibitor, which depletes all GSL5 derived from GicCer, (i) down-regulated expression of a major epithelial cell marker, E-cadherin; (ii) up-regulated expression of mesenchymal cell markers vimentin. fibronectin, and N-cadherin; (iii) enhanced haptotactic cell motility; and (iv) converted epithelial to fibroblastic morphology. These changes also were induced in these cell lines with TGF-β, which is a well-documented EMT inducer. A close association between specific GSL changes and EMT processes induced by EtDO-P4 or TGF-β is indicated by the following findings: (I) The enhanced cell motility of EtDO-P4-treated cells was abrogated by exogenous addition of GM2 or Gg4. but not GM 1 or GM3, in all 3 cell lines. (ii) TGF-β treatment caused changes in the GSL composition of cells. Notably, Gg4 or GM2 was depleted or reduced in NMuMG, and GM2 was reduced in HCV29. (iii) Exogenous addition of Gg4 inhibited TGF-β-induced changes of morphology, motility, and levels of epithelial and mesenchymal markers. These observations indicate that specific GSL5 play key roles in defining phenotypes associated with EMT and its reverse process (i.e., mesenchymal-to-epithelial transition). [ABSTRACT FROM AUTHOR]

Epidermal growth factor receptor (EGFR) at membrane microdomains plays an essential role in the growth control of epidermal cells, including cancer cells derived therefrom. Ligand-dependent activation of EGFR tyrosine kinase is known to be inhibited by ganglioside GM3, but to a much lesser degree by other glycosphin- golipids. However, the mechanism of the inhibitory effect of GM3 on EGFR tyrosine kinase has been ambiguous. The mechanism is now defined by binding of N-linked glycan having multiple GlcNAc termini to GM3 through carbohydrate-to-carbohydrate interaction, based on the following data: (i) EGFR (molecular mass, ≈17O kDa) has N-linked glycan with GIcNAc termini, as probed by mAb (J1) or lectin (GS-ll); (ii) GS-ll-bound EGFR also bound to anti-EGFR Ab as well as to GM3-coated beads; (ii,) GM3 inhibitory effect on EGFR tyrosine kinase was abrogated in vitro by coincubation with glycan having multiple GIcNAc termini and in cell culture in situ incubated with the same glycan; and (iv) cells treated with swainsonine, which increased expression of complex-type and hybrid- type glycans with GIcNAc termini. displayed higher inhibition of EGFR kinase by GM3 than swainsonine-untreated control cells. A similar effect was observed with 1-deoxymannojirimycin, which increased hybrid-type structure in addition to major accumulation of high mannose-type glycan. These findings indicate that N-linked glycan with GIcNAc termini linked to EGFR is the target to interact with GM3, causing inhibition of EGF-induced EGFR tyrosine kinase. [ABSTRACT FROM AUTHOR]

Examines the mechanism of gangliosides found in sperm of rainbow trout (Oncorhynchus mykiss). Assessment of the interaction between (KDN) GM3 (deaminated neuraminyl ganglioside) in liposomes; Influence of Gg3Cer-coated plates on the physiological condition of KDN; Understanding of the sperm-egg adhesion in the fertilization process.