title: Cell cycle arrest of hematopoietic cell lines after treatment with ceramide is commonly associated with retinoblastoma activation.
abstract: BACKGROUND
  Leukaemia cells differ from their normal counterparts in that their ability to properly regulate survival, proliferation, differentiation, and apoptosis is aberrant. Understanding the molecular mechanisms controlling cell proliferation and developing therapeutic strategies to correct nonfunctional regulatory mechanisms are emerging areas of medical research. Ceramide, a metabolite of membrane sphingomyelin hydrolysis, has recently emerged as a key regulator of cellular proliferation, differentiation, and apoptosis in leukaemia cells.
  
  
  METHODS
  Leukaemia cell lines were treated with a biologically active analogue of ceramide, C(2)-ceramide. Cell cycle status was assessed flow cytometrically using propidium iodide. Induction of apoptosis was confirmed by annexin V staining of externalised phosphatidylserine and retinoblastoma activation was determined by Western blotting.
  
  
  RESULTS
  C(2)-ceramide induced activation of retinoblastoma tumour suppressor protein, G(0)/G(1) cell cycle arrest, or apoptosis in leukaemia cell lines. In addition, these effects differed depending upon cell type, thus confirming the pleiotropic nature of the ceramide signalling pathway. Most cells studied responded to exogenous C(2)-ceramide by entering growth arrest, evidently resulting from activation of retinoblastoma protein, and by displaying some degree of apoptosis.
  
  
  CONCLUSIONS
  Taken together, these findings suggest that signalling via ceramide has novel therapeutic applications for treatment of leukaemia.
authors.affiliation: Division of Medicine, University of Tasmania, Hobart, Tasmania, Australia.
authors.forename: C E
authors.initials: CE
authors.lastname: Connor
authors.forename: J
authors.initials: J
authors.lastname: Burrows
authors.forename: A C
authors.initials: AC
authors.lastname: Hearps
authors.forename: G M
authors.initials: GM
authors.lastname: Woods
authors.forename: R M
authors.initials: RM
authors.lastname: Lowenthal
authors.forename: S J
authors.initials: SJ
authors.lastname: Ragg
mesh_terms: D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry / Q000379:methods; D016193:G1 Phase; D018922:HL-60 Cells; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D019169:Jurkat Cells; D007938:Leukemia; D010766:Phosphorylation; D016192:Resting Phase, Cell Cycle; D016160:Retinoblastoma Protein / Q000187:drug effects / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D020298:U937 Cells
chemical_list: D004791:Enzyme Inhibitors; C064769:N-acetylsphingosine; D016160:Retinoblastoma Protein; D013110:Sphingosine