title: Glioma cell death induced by irradiation or alkylating agent chemotherapy is independent of the intrinsic ceramide pathway.
abstract: OBJECTIVE
  Resistance to genotoxic therapy is a characteristic feature of glioma cells. Acid sphingomyelinase (ASM) hydrolyzes sphingomyelin to ceramide and glucosylceramide synthase (GCS) catalyzes ceramide metabolism. Increased ceramide levels have been suggested to enhance chemotherapy-induced death of cancer cells.
  
  
  METHODS
  Microarray and clinical data for ASM and GCS in astrocytomas WHO grade II-IV were acquired from the Rembrandt database. Moreover, the glioblastoma database of the Cancer Genome Atlas network (TCGA) was used for survival data of glioblastoma patients. For in vitro studies, increases in ceramide levels were achieved either by ASM overexpression or by the GCS inhibitor DL-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (PPMP) in human glioma cell lines. Combinations of alkylating chemotherapy or irradiation and ASM overexpression, PPMP or exogenous ceramide were applied in parental cells. The anti-glioma effects were investigated by assessing proliferation, metabolic activity, viability and clonogenicity. Finally, viability and clonogenicity were assessed in temozolomide (TMZ)-resistant cells upon treatment with PPMP, exogenous ceramide, alkylating chemotherapy, irradiation or their combinations.
  
  
  RESULTS
  Interrogations from the Rembrandt and TCGA database showed a better survival of glioblastoma patients with low expression of ASM or GCS. ASM overexpression or PPMP treatment alone led to ceramide accumulation but did not enhance the anti-glioma activity of alkylating chemotherapy or irradiation. PPMP or exogenous ceramide induced acute cytotoxicity in glioblastoma cells. Combined treatments with chemotherapy or irradiation led to additive, but not synergistic effects. Finally, no synergy was found when TMZ-resistant cells were treated with exogenous ceramide or PPMP alone or in combination with TMZ or irradiation.
  
  
  CONCLUSIONS
  Modulation of intrinsic glioma cell ceramide levels by ASM overexpression or GCS inhibition does not enhance the anti-glioma activity of alkylating chemotherapy or irradiation.
authors.affiliation: Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Gramatzki
authors.forename: Caroline
authors.initials: C
authors.lastname: Herrmann
authors.forename: Caroline
authors.initials: C
authors.lastname: Happold
authors.forename: Katrin Anne
authors.initials: KA
authors.lastname: Becker
authors.forename: Erich
authors.initials: E
authors.lastname: Gulbins
authors.forename: Michael
authors.initials: M
authors.lastname: Weller
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Tabatabai
mesh_terms: D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology / Q000627:therapeutic use*; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002518:Ceramides / Q000378:metabolism* / Q000494:pharmacology; D002999:Clone Cells; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000528:radiation effects; D004357:Drug Synergism; D005910:Glioma / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology*; D005964:Glucosyltransferases / Q000378:metabolism; D006801:Humans; D008614:Meperidine / Q000031:analogs & derivatives / Q000494:pharmacology; D011839:Radiation, Ionizing; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D000077204:Temozolomide; D016896:Treatment Outcome
chemical_list: D018906:Antineoplastic Agents, Alkylating; D002518:Ceramides; C026733:4-propionyloxy-4-phenyl-N-methylpiperidine; D003606:Dacarbazine; D008614:Meperidine; D005964:Glucosyltransferases; C023246:ceramide glucosyltransferase; D013108:Sphingomyelin Phosphodiesterase; D000077204:Temozolomide