Cytosolic 5'-nucleotidase II (NT5C2) is involved in the development of ara-C resistance and has been associated with clinical outcome in patients receiving ara-C- based chemotherapy. NT5C2 inactivates ara-C by dephosphorylating ara-CMP to ara-C. In this study, we sequenced NT5C2 in genomic DNA samples from International HapMap project panels with European (CEU; n=90) or African (YRI; n=90) ancestry. We identified 41 genetic variants (one insertion-deletion and 40 SNPs), including three non-synonymous SNPs (Thr3Ala, Lys47Arg, Gln136Arg). Twenty-five SNPs were novel and 16 overlapped with the HapMap data. Subjects with African ancestry had NT5C2 mRNA expression levels that was significantly higher than those with European ancestry (p = 0.005). Further, there was a correlation between NT5C2 mRNA expression and ara-C sensitivity in CEU but not in YRI cell lines. None of the non-synonymous SNPs demonstrated any effect on NT5C2 activity. The genotypes of several SNPs were significantly associated with NT5C2 mRNA expression and/or ara-C sensitivity in CEU cell lines but very few were significant in YRI cell lines. Most interestingly, SNPs (LD group CEU.12) in the 5'UTR were associated with NT5C2 expression and ara-C sensitivity in HapMap cell lines, and with NT5C2 mRNA expression and ara-C sensitivity in diagnostic leukemic blasts from pediatric patients with acute myeloid leukemia. Functional genomics analysis demonstrated that the promoter SNP rs11191612 was associated with altered luciferase activation in reporter assays and altered DNA-protein binding in gel shift assays. These results suggest that genetic variations in NT5C2 influence its expression and, potentially, cellular responses to nucleoside analogs.
- Received April 19, 2011.
- Revision received June 10, 2011.
- Accepted June 13, 2011.
- The American Society for Pharmacology and Experimental Therapeutics