title: The vascular targeting agent combretastatin-A4 and a novel cis-Restricted {beta}-Lactam Analogue, CA-432, induce apoptosis in human chronic myeloid leukemia cells and ex vivo patient samples including those displaying multidrug resistance.
abstract: Combretastatin-A4 (CA-4) is a natural derivative of the African willow tree Combretum caffrum. CA-4 is one of the most potent antimitotic components of natural origin, but it is, however, intrinsically unstable. A novel series of CA-4 analogs incorporating a 3,4-diaryl-2-azetidinone (β-lactam) ring were designed and synthesized with the objective to prevent cis -trans isomerization and improve the intrinsic stability without altering the biological activity of CA-4. Evaluation of selected β-lactam CA-4 analogs demonstrated potent antitubulin, antiproliferative, and antimitotic effects in human leukemia cells. A lead β-lactam analog, CA-432, displayed comparable antiproliferative activities with CA-4. CA-432 induced rapid apoptosis in HL-60 acute myeloid leukemia cells, which was accompanied by depolymerization of the microtubular network, poly(ADP-ribose) polymerase cleavage, caspase-3 activation, and Bcl-2 cleavage. A prolonged G(2)M cell cycle arrest accompanied by a sustained phosphorylation of mitotic spindle checkpoint protein, BubR1, and the antiapoptotic proteins Bcl-2 and Bcl-x(L) preceded apoptotic events in K562 chronic myeloid leukemia (CML) cells. Molecular docking studies in conjunction with comprehensive cell line data rule out CA-4 and β-lactam derivatives as P-glycoprotein substrates. Furthermore, both CA-4 and CA-432 induced significantly more apoptosis compared with imatinib mesylate in ex vivo samples from patients with CML, including those positive for the T315I mutation displaying resistance to imatinib mesylate and dasatinib. In summary, synthetic intrinsically stable analogs of CA-4 that display significant clinical potential as antileukemic agents have been designed and synthesized.
authors.affiliation: School of Biochemistry and Immunology, Trinity College, Dublin 2, Ireland. greeneli@tcd.ie
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Greene
authors.forename: Seema M
authors.initials: SM
authors.lastname: Nathwani
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Bright
authors.forename: Darren
authors.initials: D
authors.lastname: Fayne
authors.forename: Aisling
authors.initials: A
authors.lastname: Croke
authors.forename: Maria
authors.initials: M
authors.lastname: Gagliardi
authors.forename: Anthony M
authors.initials: AM
authors.lastname: McElligott
authors.forename: Lisa
authors.initials: L
authors.lastname: O'Connor
authors.forename: Miriam
authors.initials: M
authors.lastname: Carr
authors.forename: Niall O
authors.initials: NO
authors.lastname: Keely
authors.forename: Niamh M
authors.initials: NM
authors.lastname: O'Boyle
authors.forename: Peig
authors.initials: P
authors.lastname: Carroll
authors.forename: Balazs
authors.initials: B
authors.lastname: Sarkadi
authors.forename: Eibhlin
authors.initials: E
authors.lastname: Conneally
authors.forename: David G
authors.initials: DG
authors.lastname: Lloyd
authors.forename: Mark
authors.initials: M
authors.lastname: Lawler
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Meegan
authors.forename: Daniela M
authors.initials: DM
authors.lastname: Zisterer
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001384:Azetidines / Q000737:chemistry / Q000494:pharmacology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D006139:Guaiacol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D020014:K562 Cells; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D015394:Molecular Structure; D013237:Stereoisomerism; D013267:Stilbenes / Q000737:chemistry / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism; D047090:beta-Lactams / Q000737:chemistry*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D001384:Azetidines; C553484:CA 432; C581630:CA-104; D013267:Stilbenes; D014404:Tubulin; D047090:beta-Lactams; D006139:Guaiacol; C058728:fosbretabulin