Deoxycytidine kinase modulates the impact of the ABC transporter ABCG2 on clofarabine cytotoxicity.
Purine nucleoside antimetabolites, such as clofarabine, are effective antileukemic agents. However, their effectiveness depends on an initial activation step in which they are monophosphorylated by deoxycytidine kinase (dCK). Some purine nucleoside antimetabolites and their monophosphate derivatives are exported by the ABC transporter ABCG2. Because clofarabine is a dCK substrate, and we show substantial variation in dCK and ABCG2 in myeloid leukemia, we hypothesized that the activity of dCK may modulate ABCG2-mediated resistance to clofarabine by regulating the formation of clofarabine monophosphate. We show that ABCG2 influence on clofarabine cytotoxicity was markedly influenced by dCK activity. When dCK expression was reduced by siRNA, clofarabine cytotoxicity was strongly reduced by enhanced ABCG2-mediated efflux. Conversely, dCK overexpression blunted ABCG2-mediated efflux of clofarabine by increasing the formation of clofarabine nucleotides. The use of an ABCG2 inhibitor confirmed that ABCG2 export of clofarabine is maximal when dCK levels are minimal. Analysis of intracellular clofarabine metabolites suggested that ABCG2 exported clofarabine more readily than clofarabine monophosphate. That ABCG2 primarily effluxes clofarabine, but not chlorfarabine-monophosphate, was confirmed by HPLC analysis of drug exported from ABCG2-overexpressing cells. Because the level and function of dCK and ABCG2 vary substantially among other types of cancer, these findings have important implications not only for clofarabine therapy but for purine nucleoside therapy in general. Therefore, we propose that addition of ABCG2 inhibitors would effectively increase the antitumor efficacy of purine nucleosides by blocking drug efflux that may be a significant mode of resistance when dCK levels are low.
Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Shinjiro
S
Nagai
Kazumasa
K
Takenaka
Deepa
D
Nachagari
Charles
C
Rose
Kali
K
Domoney
Daxi
D
Sun
Alex
A
Sparreboom
John D
JD
Schuetz
D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000227:Adenine Nucleotides / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000378:metabolism*; D001087:Arabinonucleosides / Q000378:metabolism*; D045744:Cell Line, Tumor; D000077866:Clofarabine; D003842:Deoxycytidine Kinase / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction
C116614:ABCG2 protein, human; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000227:Adenine Nucleotides; D000970:Antineoplastic Agents; D001087:Arabinonucleosides; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D000077866:Clofarabine; D003842:Deoxycytidine Kinase
Leuk Lymphoma. 2007 Oct;48(10):1922-30
17852710
Cancer Res. 1999 Dec 1;59(23):5956-63
10606241
Clin Cancer Res. 1999 Sep;5(9):2438-44
10499616
Clin Cancer Res. 2006 Jul 1;12(13):4011-7
16818700
Mol Cancer Ther. 2008 Sep;7(9):3092-102
18765824
Nat Med. 1999 Sep;5(9):1048-51
10470083
Physiol Rev. 2006 Oct;86(4):1179-236
17015488
Antiviral Res. 2004 Apr;62(1):1-7
15026196
Curr Opin Investig Drugs. 2004 Jun;5(6):592-6
15242246
Haematologica. 2003 Mar;88(3):324-32
12651272
Nat Rev Drug Discov. 2006 Oct;5(10):855-63
17016426
Curr Opin Oncol. 2006 Nov;18(6):584-90
16988579
Blood. 1993 Jan 1;81(1):143-50
8093345
Proc Natl Acad Sci U S A. 1992 Apr 1;89(7):2970-4
1348362
Blood. 2003 Oct 1;102(7):2379-86
12791647
Blood. 2004 Feb 1;103(3):784-9
14551141
Clin Cancer Res. 2009 Oct 1;15(19):6062-9
19773380
Cancer Res. 2007 Jul 15;67(14):6965-72
17638908
J Biol Chem. 2002 Oct 11;277(41):38998-9004
12105214
Proc Natl Acad Sci U S A. 2000 Jun 20;97(13):7476-81
10840050
Oncogene. 2003 Oct 20;22(47):7524-36
14576856
J Pharmacol Exp Ther. 2007 Dec;323(3):935-45
17855478
Mol Pharmacol. 2006 Jan;69(1):346-53
16234483
Physiology (Bethesda). 2008 Feb;23:41-8
18268364
Cancer Res. 1991 May 1;51(9):2386-94
1707752
Mol Pharmacol. 2002 Dec;62(6):1321-31
12435799
Nat Struct Biol. 2003 Jul;10(7):513-9
12808445