title: Inhibition of leukemic cell growth by the protein kinase C activator bryostatin 1 correlates with the dephosphorylation of cyclin-dependent kinase 2.
abstract: Bryostatin 1 is a natural antineoplastic agent that activates protein kinase C. Treatment of U937 human leukemic cells with bryostatin 1 caused a 60% reduction in cell growth, whereas another protein kinase C activator, phorbol myristate acetate (PMA), completely inhibited U937 cell growth. Both bryostatin 1 and PMA induced inhibition of cyclin-dependent kinase 2 (cdk2) activity. The first phase of cdk2 inhibition correlated with the transient induction of p21, a known inhibitor of cdk2. In contrast, the second phase of cdk2 inhibition correlated with the dephosphorylation of cdk2 on threonine-160, which must be phosphorylated for cdk2 activity. The level of growth inhibition induced by these two compounds correlated with the degree of cdk2 dephosphorylation as follows: bryostatin 1, 60%; PMA, 100%.
authors.affiliation: Division of Hematology/Oncology, University of Alabama, Birmingham 35294, USA.
authors.forename: C
authors.initials: C
authors.lastname: Asiedu
authors.forename: J
authors.initials: J
authors.lastname: Biggs
authors.forename: M
authors.initials: M
authors.lastname: Lilly
authors.forename: A S
authors.initials: AS
authors.lastname: Kraft
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001483:Base Sequence; D015153:Blotting, Western; D054713:Bryostatins; D042846:CDC2-CDC28 Kinases; D002455:Cell Division / Q000187:drug effects; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism*; D006801:Humans; D007783:Lactones / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000378:metabolism* / Q000473:pathology*; D018942:Macrolides; D008969:Molecular Sequence Data; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D054713:Bryostatins; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007783:Lactones; D018942:Macrolides; D012333:RNA, Messenger; C046785:bryostatin 1; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D013755:Tetradecanoylphorbol Acetate