The human equilibrative nucleoside transporter 1 mediates in vitro cytarabine sensitivity in childhood acute myeloid leukaemia.
Cytarabine (ara-C) is the most effective agent for the treatment of acute myeloid leukaemia (AML). Aberrant expression of enzymes involved in the transport/metabolism of ara-C could explain drug resistance. We determined mRNA expression of these factors using quantitative-real-time-PCR in leukemic blasts from children diagnosed with de novo AML. Expression of the inactivating enzyme pyrimidine nucleotidase-I (PN-I) was 1.8-fold lower in FAB-M5 as compared to FAB-M1/2 (P=0.007). In vitro sensitivity to deoxynucleoside analogues was determined using the MTT-assay. Human equilibrative nucleoside transporter-1 (hENT1) mRNA expression and ara-C sensitivity were significantly correlated (rp=-0.46; P=0.001), with three-fold lower hENT1 mRNA levels in resistant patients (P=0.003). hENT1 mRNA expression also seemed to correlate inversely with the LC50 values of cladribine (rp=-0.30; P=0.04), decitabine (rp=-0.29; P=0.04) and gemcitabine (rp=-0.33; P=0.02). Deoxycytidine kinase (dCK) and cytidine deaminase (CDA) mRNA expression seemed to correlate with in vitro sensitivity to gemcitabine (rp=-0.31; P=0.03) and decitabine (rp=0.33; P=0.03), respectively. The dCK/PN-I ratio correlated inversely with LC50 values for gemcitabine (rp=-0.45, P=0.001) and the dCK/CDA ratio seemed to correlate with LC50 values for decitabine (rp=-0.29; 0.04). In conclusion, decreased expression of hENT1, which transports ara-C across the cell membrane, appears to be a major factor in ara-C resistance in childhood AML.
Hubeek
I
I
Department of Pediatric Hematology/Oncology, VU University Medical Center, De Boelelaan 1117, Postbus 7057, 1007 MB, Amsterdam, The Netherlands. isabelle.hubeek@vumc.nl
Stam
R W
RW
Peters
G J
GJ
Broekhuizen
R
R
Meijerink
J P P
JP
van Wering
E R
ER
Gibson
B E S
BE
Creutzig
U
U
Zwaan
C M
CM
Cloos
J
J
Kuik
D J
DJ
Pieters
R
R
Kaspers
G J L
GJ
D000208:Acute Disease; D000964:Antimetabolites, Antineoplastic / Q000493:pharmacokinetics / Q000494:pharmacology*; D002462:Cell Membrane; D002648:Child; D003561:Cytarabine / Q000493:pharmacokinetics / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D033721:Equilibrative Nucleoside Transporter 1 / Q000502:physiology*; D020869:Gene Expression Profiling; D006801:Humans; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D000964:Antimetabolites, Antineoplastic; D033721:Equilibrative Nucleoside Transporter 1; D012333:RNA, Messenger; C438649:SLC29A1 protein, human; D003561:Cytarabine