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The human equilibrative nucleoside transporter 1 mediates in vitro cytarabine sensitivity in childhood acute myeloid leukaemia.

Hubeek I, Stam RW, Peters GJ, Broekhuizen R, Meijerink JP, van Wering ER, Gibson BE, Creutzig U, Zwaan CM, Cloos J, Kuik DJ, Pieters R, Kaspers GJ - Br. J. Cancer (2005)

Bottom Line: 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).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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric Hematology/Oncology, VU University Medical Center, De Boelelaan 1117, Postbus 7057, 1007 MB, Amsterdam, The Netherlands. isabelle.hubeek@vumc.nl

ABSTRACT
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.

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hENT1 mRNA expression in relation to in vitro ara-C sensitivity. AML patient samples were divided into three groups based on in vitro ara-C sensitivity (sensitive=LC50<0.98 μM), intermediate=0.98<LC50 <5.18 μM) and resistant=LC50>5.18 μM) (Zwaan et al, 2000). Patient resistant to ara-C in vitro expressed 3.0-fold lower hENT1 mRNA levels compared to sensitive patients. The lines indicate the median value. P-value determined by one-way ANOVA.
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fig3: hENT1 mRNA expression in relation to in vitro ara-C sensitivity. AML patient samples were divided into three groups based on in vitro ara-C sensitivity (sensitive=LC50<0.98 μM), intermediate=0.98<LC50 <5.18 μM) and resistant=LC50>5.18 μM) (Zwaan et al, 2000). Patient resistant to ara-C in vitro expressed 3.0-fold lower hENT1 mRNA levels compared to sensitive patients. The lines indicate the median value. P-value determined by one-way ANOVA.

Mentions: mRNA expression levels of hENT1, dCK, PN-I, CDA, dCMPd, RR1/2 and CTPs were entered into a stepwise multivariate regression model to identify the most important indicators with respect to in vitro sensitivity to deoxynucleoside analogues (dependent variables LC50 values ara-C, 2-CdA, DAC, F-ara-A or dFdC). In multivariate analysis, hENT1 mRNA expression predicted in vitro sensitivity to ara-C (P=0.002). Furthermore, CDA mRNA expression levels seemed to predict in vitro sensitivity to DAC (P=0.02), while other factors did not reach significance. Also, when we divided the AML samples in three subgroups based on their in vitro ara-C sensitivity, resistant patients expressed three-fold lower hENT1 mRNA levels compared to sensitive patients (P=0.003; Figure 3).


The human equilibrative nucleoside transporter 1 mediates in vitro cytarabine sensitivity in childhood acute myeloid leukaemia.

Hubeek I, Stam RW, Peters GJ, Broekhuizen R, Meijerink JP, van Wering ER, Gibson BE, Creutzig U, Zwaan CM, Cloos J, Kuik DJ, Pieters R, Kaspers GJ - Br. J. Cancer (2005)

hENT1 mRNA expression in relation to in vitro ara-C sensitivity. AML patient samples were divided into three groups based on in vitro ara-C sensitivity (sensitive=LC50<0.98 μM), intermediate=0.98<LC50 <5.18 μM) and resistant=LC50>5.18 μM) (Zwaan et al, 2000). Patient resistant to ara-C in vitro expressed 3.0-fold lower hENT1 mRNA levels compared to sensitive patients. The lines indicate the median value. P-value determined by one-way ANOVA.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2361532&req=5

fig3: hENT1 mRNA expression in relation to in vitro ara-C sensitivity. AML patient samples were divided into three groups based on in vitro ara-C sensitivity (sensitive=LC50<0.98 μM), intermediate=0.98<LC50 <5.18 μM) and resistant=LC50>5.18 μM) (Zwaan et al, 2000). Patient resistant to ara-C in vitro expressed 3.0-fold lower hENT1 mRNA levels compared to sensitive patients. The lines indicate the median value. P-value determined by one-way ANOVA.
Mentions: mRNA expression levels of hENT1, dCK, PN-I, CDA, dCMPd, RR1/2 and CTPs were entered into a stepwise multivariate regression model to identify the most important indicators with respect to in vitro sensitivity to deoxynucleoside analogues (dependent variables LC50 values ara-C, 2-CdA, DAC, F-ara-A or dFdC). In multivariate analysis, hENT1 mRNA expression predicted in vitro sensitivity to ara-C (P=0.002). Furthermore, CDA mRNA expression levels seemed to predict in vitro sensitivity to DAC (P=0.02), while other factors did not reach significance. Also, when we divided the AML samples in three subgroups based on their in vitro ara-C sensitivity, resistant patients expressed three-fold lower hENT1 mRNA levels compared to sensitive patients (P=0.003; Figure 3).

Bottom Line: 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).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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatric Hematology/Oncology, VU University Medical Center, De Boelelaan 1117, Postbus 7057, 1007 MB, Amsterdam, The Netherlands. isabelle.hubeek@vumc.nl

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus