title: DNA damage induces down-regulation of UDP-glucose ceramide glucosyltransferase, increases ceramide levels and triggers apoptosis in p53-deficient cancer cells.
abstract: DNA damaging agents typically induce an apoptotic cascade in which p53 plays a central role. However, absence of a p53-mediated response does not necessarily abrogate programmed cell death, due to the existence of p53-independent apoptotic pathways, such as those mediated by the pro-apoptotic molecule ceramide. We compared ceramide levels before and after DNA damage in human osteosarcoma (U2OS) and colon cancer (HCT116) cells that were either expressing or deficient in p53. When treated with mitomycin C, p53-deficient cells, but not p53-expressing cells, showed a marked increase in ceramide levels. Microarray analysis of genes involved in ceramide metabolism identified acid ceramidase (ASAH1, up-regulated), ceramide glucosyltransferase (UGCG, down-regulated), and galactosylceramidase (GALC, up-regulated) as the three genes most affected. Experiments employing pharmacological and siRNA agents revealed that inhibition of UGCG is sufficient to increase ceramide levels and induce cell death. When inhibition of UGCG and treatment with mitomycin C were combined, p53-deficient, but not p53-expressing cells, showed a significant increase in cell death, suggesting that the regulation of sphingolipid metabolism could be used to sensitize cells to chemotherapeutic drugs.
authors.affiliation: Loma Linda University, Department of Basic Science, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
authors.forename: Teka-Ann S
authors.initials: TA
authors.lastname: Haynes
authors.forename: Valery
authors.initials: V
authors.lastname: Filippov
authors.forename: Maria
authors.initials: M
authors.lastname: Filippova
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Kangling
authors.initials: K
authors.lastname: Zhang
authors.forename: Penelope J
authors.initials: PJ
authors.lastname: Duerksen-Hughes
mesh_terms: D055573:Acid Ceramidase / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D001859:Bone Neoplasms; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002518:Ceramides / Q000819:agonists / Q000096:biosynthesis*; D003110:Colonic Neoplasms; D004249:DNA Damage; D005698:Galactosylceramidase / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D016685:Mitomycin / Q000494:pharmacology; D012516:Osteosarcoma; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000172:deficiency / Q000235:genetics*
chemical_list: D002518:Ceramides; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D005698:Galactosylceramidase; C526693:ASAH1 protein, human; D055573:Acid Ceramidase