title: Glycosylation of ceramide potentiates cellular resistance to tumor necrosis factor-alpha-induced apoptosis.
abstract: Ceramide, as a second messenger, initiates one of the major signal transduction pathways in tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. Glucosylceramide synthase (GCS) catalyzes glycosylation of ceramide and produces glucosylceramide. By introduction of the GCS gene, cytotoxic resistance to TNF-alpha has been conferred in human breast cancer cells. MCF-7/GCS-transfected cells expressed 4.1-fold higher levels of GCS activity and exhibited a 15-fold (P < 0.0005) greater EC(50) for TNF-alpha, compared with the parental MCF-7 cell line. DNA fragmentation and DNA synthesis studies showed that TNF-alpha had little influence on the induction of apoptosis or on growth arrest in MCF-7/GCS cells, compared to MCF-7 cells. These studies reveal that TNF-alpha resistance in MCF-7/GCS cells is closely related to ceramide hyperglycosylation, a hallmark of this transfected cell line, and resistance was not aligned with changes in TNF receptor 1 expression. This work demonstrates that GCS, which catalyzes ceramide glycosylation, potentiates cytotoxic resistance to TNF-alpha.
authors.affiliation: John Wayne Cancer Institute at Saint John's Health Center, Santa Monica, California, 90404, USA.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Liu
authors.forename: T Y
authors.initials: TY
authors.lastname: Han
authors.forename: A E
authors.initials: AE
authors.lastname: Giuliano
authors.forename: S
authors.initials: S
authors.lastname: Ichikawa
authors.forename: Y
authors.initials: Y
authors.lastname: Hirabayashi
authors.forename: M C
authors.initials: MC
authors.lastname: Cabot
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002518:Ceramides / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D005964:Glucosyltransferases / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D002518:Ceramides; D014409:Tumor Necrosis Factor-alpha; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase