title: The absence of functional glucosylceramide synthase does not sensitize melanoma cells for anticancer drugs.
abstract: Conversion of ceramide, a putative mediator of anticancer drug-induced apoptosis, into glucosylceramide, by the action of glucosylceramide synthase (GCS), has been implicated in drug resistance. Herein, we compared GM95 mouse melanoma cells deficient in GCS activity, with cells stably transfected with a vector encoding GCS (GM95/GCS). Enzymatic and metabolic analysis demonstrated that GM95/GCS cells expressed a fully functional enzyme, resulting in normal ceramide glycosylation. However, cytotoxicity assays, as well as caspase activation and cytochrome c release studies, did not reveal any difference between the two cell lines with respect to their sensitivity toward doxorubicin, vinblastine, paclitaxel, cytosine arabinoside, or short-chain ceramide analogs. Administration of doxorubicin resulted in ceramide accumulation in both cell lines, with similar kinetics and amplitude. Although glucosylceramide formation was detected in doxorubicin-treated GM95/GCS cells, metabolism of drug-induced ceramide did not appear to be instrumental in cell survival. Furthermore, N-(n-butyl)deoxynojirimycin, a potent and non-toxic GCS inhibitor, had no chemosensitizing effect on wild-type melanoma cells. Altogether, both genetic and pharmacological alterations of the cellular ceramide glycosylation capacity failed to sensitize melanoma cells to anticancer drugs, therefore moderating the importance of ceramide glucosylation in drug-resistance mechanisms.
authors.affiliation: INSERM U.466, Laboratoire de Biochimie, Institut Louis Bugnard, CHU Rangueil, 1 avenue Jean Poulhès, TSA 50032, 31059 Toulouse Cedex 9, France.
authors.forename: Robert Jan
authors.initials: RJ
authors.lastname: Veldman
authors.forename: Alain
authors.initials: A
authors.lastname: Mita
authors.forename: Olivier
authors.initials: O
authors.lastname: Cuvillier
authors.forename: Virginie
authors.initials: V
authors.lastname: Garcia
authors.forename: Karin
authors.initials: K
authors.lastname: Klappe
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Medin
authors.forename: John D
authors.initials: JD
authors.lastname: Campbell
authors.forename: Stéphane
authors.initials: S
authors.lastname: Carpentier
authors.forename: Jan Willem
authors.initials: JW
authors.lastname: Kok
authors.forename: Thierry
authors.initials: T
authors.lastname: Levade
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000032:analysis; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis; D002470:Cell Survival; D002518:Ceramides / Q000096:biosynthesis / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D017353:Gene Deletion; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008546:Melanoma, Experimental / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008954:Models, Biological; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D002518:Ceramides; D004317:Doxorubicin; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase