title: 3-Hydrogenkwadaphnin targets inosine 5'-monophosphate dehydrogenase and triggers post-G1 arrest apoptosis in human leukemia cell lines.
abstract: 3-Hydrogenkwadaphnin (3-HK) is a recently characterized daphnane-type compound isolated from Dendrostellera lessertii with high anti-tumor activity in animal models. Herein, we report on time- and dose-dependent effects of this compound on growth, differentiation, IMPDH inhibition, cell cycle and apoptosis of a panel of human leukemia cell lines (HL-60, K562 and Molt4). The drug decreased the growth of leukemia cells in less than 24 h of treatment. However, longer exposure times and/or higher concentrations were required to promote cell apoptosis. Cell cycle analysis revealed the accumulation of cells in their G1 phase as early as 12 h after drug exposure but sub-G1 population was recorded after 24 h. Occurrence of apoptosis was constantly accompanied by morphological (staining with DNA-binding dyes) and biochemical (DNA fragments) variations among drug-treated cells. Despite these observations, non-activated normal human PBL were insensitive to the drug action. In addition, treatment of PHA-activated PBL, K562, Molt4 and HL-60 cells with a single dose of the drug for 24 h led to the inhibition of IMPDH activity by almost 37, 38, 44 and 50%, respectively. In contrast, no difference in IMPDH activities were seen between normal PBL and the drug treated PBL cells. Restoration of the depleted GTP concentration by exogenous addition of guanosine (25-50 microM) reversed the drug effects on cell growth, DNA fragmentation and apoptosis. Furthermore, the drug effects were potentiated by exogenous addition of hypoxanthine to the drug-treated cells. Reduction of the drug potency on the non-proliferative (retinoic acid treated) HL-60 cells by almost 40%, compared to the proliferative cells, clearly shows type II IMPDH as one of the main targets of the drug. These results suggest that 3-HK may be a powerful candidate for treatment of leukemia.
authors.affiliation: Institute of Biochemistry and Biophysics, P.O. Box 13145-1384, University of Tehran, Tehran, Iran.
authors.forename: Mohammad Amin
authors.initials: MA
authors.lastname: Moosavi
authors.forename: Razieh
authors.initials: R
authors.lastname: Yazdanparast
authors.forename: Mohammad Hasan
authors.initials: MH
authors.lastname: Sanati
authors.forename: Abdolfattah Sarraf
authors.initials: AS
authors.lastname: Nejad
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D004224:Diterpenes / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D016193:G1 Phase / Q000502:physiology*; D006151:Guanosine / Q000378:metabolism; D006801:Humans; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D007938:Leukemia / Q000378:metabolism*; D008297:Male; D015394:Molecular Structure; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects*
chemical_list: C505417:3-hydrogenkwadaphnin; D000972:Antineoplastic Agents, Phytogenic; D004224:Diterpenes; D007527:Isoenzymes; D006151:Guanosine; D007168:IMP Dehydrogenase