title: Betuletol 3-methyl ether induces G(2)-M phase arrest and activates the sphingomyelin and MAPK pathways in human leukemia cells.
abstract: Betuletol 3-methyl ether (BME) is a natural phenylbenzo-gamma-pyrone that inhibits cell proliferation in human tumor cell lines and induces apoptotic cell death in HL-60 cells. Here we show that BME displays strong cytotoxic properties in several human leukemia cell lines (U937, K-562, THP-1, Jurkat, and Molt-3) and in cells that over-express two anti-apoptotic proteins, namely Bcl-2 and Bcl-x(L). BME arrested HL-60 cells at G(2)-M phase of the cell cycle, which was associated with the accumulation of cyclin B1 and p21(Cip1). Fluorescence microscopy experiments suggest that BME blocked the cell cycle in mitosis. The in vivo tubulin polymerization assay shows that BME inhibits tubulin polymerization and causes similar changes of cellular microtubule network as colchicine. Our results demonstrate that BME-induced cell death is (i) triggered in human myeloid leukemia cell that over-express Bcl-2 and Bcl-x(L), and (ii) associated with loss of inner mitochondrial membrane potential (DeltaPsim) and an increase in reactive oxygen species (ROS). Although ROS increased in response to BME, this did not seem to play a pivotal role in the apoptotic process since the anti-oxidant trolox was unable to provide cell protection. The treatment of HL-60 cells with BME induces the activation of mitogen-activated protein kinases (MAPKs) such as c-Jun N-terminal kinases, p38 mitogen-activated protein kinases and extracellular signal-regulated kinases (ERK)1/2 and stimulates the acid sphingomyelinase with concomitant ceramide generation. The findings of this study suggest that BME could be useful in the development of novel anticancer agents.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Las Palmas de Gran Canaria, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Rubio
authors.forename: José
authors.initials: J
authors.lastname: Quintana
authors.forename: José L
authors.initials: JL
authors.lastname: Eiroa
authors.forename: Jorge
authors.initials: J
authors.lastname: Triana
authors.forename: Francisco
authors.initials: F
authors.lastname: Estévez
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004987:Ethers / Q000737:chemistry / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D016195:G2 Phase / Q000187:drug effects*; D018922:HL-60 Cells; D006801:Humans; D019169:Jurkat Cells; D020014:K562 Cells; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D015394:Molecular Structure; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism*; D020298:U937 Cells; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D004987:Ethers; D005419:Flavonoids; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013109:Sphingomyelins; D051020:bcl-X Protein; C515374:betuletol 3-methyl ether; D020928:Mitogen-Activated Protein Kinases