Association between single nucleotide polymorphisms in deoxycytidine kinase and treatment response among acute...

Development of resistance to 1-beta-arabinofuranosylcytosine (AraC) is a major obstacle in the treatment of patients with acute myeloid leukaemia (AML). Deficiency of functional deoxycytidine kinase (dCK) plays an important role in AraC resistance in vitro. We screened 5378 bp sequences of the dCK gene, including all exons and the 5' flanking region, and identified two single nucleotide polymorphisms (SNPs) in the regulatory region (rSNPs) with high allele frequencies. These two rSNPs (-201C>T and -360C>G) formed two major haplotypes. Genotyping with sequencing and MassARRAY system among 122 AML patients showed that those with -360CG/-201CT and -360GG/-201TT compound genotypes (n = 41) displayed a favourable response to chemotherapy whereas those with -360CC/-201CC (n = 81) tended to have a poor response (P = 0.025). Moreover, real-time quantitative reverse transcriptase-polymerase chain reaction showed that patients with -360CG/-201CT and -360GG/-201TT genotypes expressed higher level of dCK mRNA compared to those with the -360CC/-201CC genotype (P = 0.0034). Luciferase-reporter assay showed that dCK 5' regulatory region bearing -360G/-201T genotype alone had an eight-fold greater transcriptional activation activity compared to that with -360C/-201C genotype, whereas co-transfection of both -360G/-201T and -360C/-201C constructs mimicked the heterozygous genotype, which exhibited a four-fold greater activity compared to that with -360C/-201C. These results indicate that rSNP haplotypes of dCK gene may serve as a genetic marker for predicting drug responsiveness, which will be beneficial in establishing more effective AML chemotherapeutic regimens.