Etoposide (VP-16)-related secondary myeloid leukemias (t-AML) are most frequently associated with MLL gene translocations at 11q23. Our central hypothesis is that redox cycling of VP-16 initiated by myeloperoxidase (MPO) found prominently in myeloid precursors amplifies the genotoxicity and carcinogenicity of this otherwise clinically effective DNA topoisomerase II (topo ll)-targeted anticancer agent. We propose that MPO converts VP-16 to free radical species and oxidized metabolites that induce oxidative DNA damage and initiate recombinogenic events in myeloid precursor stem cells leading to the chromosomal translocations responsible for t-AML. Specifically, it is proposed: 1) that oxidative damage and abasic DNA sites formed as a consequence of peroxidative activation of VP-16 result in loci that will increase topo II poisoning; and/or: 2) that electrophilic VP-16-ortho-quinone formed in MPO-rich progenitors will poison topo II by adduction to sulfhydryl groups on the enzyme. We further posit that nutritional antioxidants such as vitamin C and vitamin E homologs will prevent VP-16-induced AML by reducing or preventing production of peroxidase-dependent free radical and electrophilic metabolites. We propose to determine the mechanism(s) by which peroxidative activation of VP-16 to phenoxyl radical and ortho-quinone metabolites enhances its DNA damaging and recombinogenic activities in genomic regions of the MLL gene known to contain breakpoints associated with t-AML. In order to test the stated hypotheses four specific aims will be pursued to: 1) determine the role of MPO-mediated VP-16 oxidative activation in MLL gene translocations in MPO-rich HL-60 cells and normal human CD34+ progenitor cells. 2) establish that VP-16-induced oxidative DNA damage and consequent abasic sites on DNA result in enhanced DNA topo ll-mediated strand breaks and increased MLL gene rearrangements. 3) identify functionally important modifications in DNA topo IIa caused by VP-16 oxidative activation in vitro and in intact cells utilizing biochemical and protein mass spectrometric techniques. 4) determine the in vivo effects of ascorbate supplementation on VP-16-induced MLL gene arrangements in CD34+ cells using a unique ascorbate-dependent rat model. Relevance: The current proposal will investigate whether the free radical forms of VP-16 produced in certain normal blood cells are responsible for specific DNA aberrations causal for myeloid leukemia. This work will also examine whether nutritional antioxidants can prevent VP-16-induced leukemia. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA090787-05A1
Application #
7268262
Study Section
Developmental Therapeutics Study Section (DT)
Program Officer
Steele, Vernon E
Project Start
2001-07-01
Project End
2012-05-31
Budget Start
2007-07-26
Budget End
2008-05-31
Support Year
5
Fiscal Year
2007
Total Cost
$317,600
Indirect Cost
Name
University of Pittsburgh
Department
Pharmacology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Hasinoff, Brian B; Wu, Xing; Patel, Daywin et al. (2016) Mechanisms of Action and Reduced Cardiotoxicity of Pixantrone; a Topoisomerase II Targeting Agent with Cellular Selectivity for the Topoisomerase II? Isoform. J Pharmacol Exp Ther 356:397-409
Yadav, Arun A; Chee, Gaik-Lean; Wu, Xing et al. (2015) Structure-based design, synthesis and biological testing of piperazine-linked bis-epipodophyllotoxin etoposide analogs. Bioorg Med Chem 23:3542-51
Hasinoff, Brian B; Wu, Xing; Yadav, Arun A et al. (2015) Cellular mechanisms of the cytotoxicity of the anticancer drug elesclomol and its complex with Cu(II). Biochem Pharmacol 93:266-76
Ren, Yulin; Yuan, Chunhua; Deng, Youcai et al. (2015) Cytotoxic and natural killer cell stimulatory constituents of Phyllanthus songboiensis. Phytochemistry 111:132-40
Ren, Yulin; Lantvit, Daniel D; Deng, Youcai et al. (2014) Potent cytotoxic arylnaphthalene lignan lactones from Phyllanthus poilanei. J Nat Prod 77:1494-504
Yadav, Arun A; Wu, Xing; Patel, Daywin et al. (2014) Structure-based design, synthesis and biological testing of etoposide analog epipodophyllotoxin-N-mustard hybrid compounds designed to covalently bind to topoisomerase II and DNA. Bioorg Med Chem 22:5935-49
Hasinoff, Brian B; Wu, Xing; Nitiss, John L et al. (2012) The anticancer multi-kinase inhibitor dovitinib also targets topoisomerase I and topoisomerase II. Biochem Pharmacol 84:1617-26
Yalowich, Jack C; Wu, Xing; Zhang, Rui et al. (2012) The anticancer thiosemicarbazones Dp44mT and triapine lack inhibitory effects as catalytic inhibitors or poisons of DNA topoisomerase II?. Biochem Pharmacol 84:52-8
Zhang, Rui; Wu, Xing; Yalowich, Jack C et al. (2011) Design, synthesis, and biological evaluation of a novel series of bisintercalating DNA-binding piperazine-linked bisanthrapyrazole compounds as anticancer agents. Bioorg Med Chem 19:7023-32
Wu, Xing; Yalowich, Jack C; Hasinoff, Brian B (2011) Cadmium is a catalytic inhibitor of DNA topoisomerase II. J Inorg Biochem 105:833-8

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