Abstract 1170: Correlation between cytidine deaminase single nucleotide polymorphisms and in vitro drug sensitivity, DNA methylation and outcome in normal karyotype acute myelogenous leukemia.
Authors: Jakobsen Falk Ingrid , Fyrberg Anna , Hermanson Monica , Höglund Martin , Nahi Hareth , Palmqvist Lars , Paul Christer , Paul Esbjörn , Rosenquist Richard , Stockelberg Dick , Wei Yuan , Green Henrik , Lotfi Kourosh 
Published: August 2014

Abstract
Background: De novo AML with normal karyotype (NK-AML) comprise a large group of patients without common cytogenetic alterations but with a large variation in treatment response. New tools such as the analysis of nucleophosmine 1 (NPM1), FMS-like tyrosine kinase 3 (FLT3) and CCAAT/enhancer binding protein (CEBPA) mutations has emerged as clinical markers of prognosis, but there is still a need for additional tools to explain the variation in outcome. Cytarabine (Ara-C), a cornerstone in AML chemotherapy, is activated intracellularly by deoxycytidine kinase (dCK), and deactivated by cytidine deaminase (CDA) and poor treatment outcome or development of chemotherapy resistance can be due to altered activity of these enzymes. Single nucleotide polymorphisms (SNPs) of CDA genes have previously been reported to result in lower CDA allelic expression and to affect the outcome of treatment. In addition, pharmacological inhibition of CDA has been shown to reduce the degree of DNA methylation. DNA methylation may be an important regulatory mechanism for the expression of genes related to drug effect, and we therefore aimed to investigate the relationship between CDA polymorphisms and outcome in NK-AML, DNA methylation, and in vitro drug cytotoxicity. Method: 207 Swedish NK-AML patients were genotyped for the CDA SNPs 79A&gt;C (rs2072671) and -451C&gt;T (rs532545) and the results were correlated to treatment response and overall survival (OS) in the material as a whole as well as stratified based on FLT3 and NPM1 status. Cells from a subset of the patients were also investigated for genotype association with in vitro drug cytotoxicity (n=56) and global DNA methylation (n=82). Results: CDA 79C/C or -451T/T genotype was associated to a shorter OS compared to other genotypes (0.44 vs. 1.86 years, p=0.004; and 0.45 vs. 1.79 years, p=0.051) for FLT3-ITD+ patients, and this was even more pronounced in the FLT3-ITD+/NPM1+ cases. There was significantly less DNA methylation in cells heterozygous for both polymorphisms (A/C+C/T) compared to homozygous A/A+C/C cells (p=0.018). There was also a lower degree of methylation in homozygous C/C+T/T cells, but due to the small number of samples in this group significance was not reached. An altered in vitro sensitivity towards topoisomerase inhibitory drugs, but not towards nucleoside analogues was seen for both CDA SNPs with homozygous C/C or T/T cells being more sensitive. Conclusions: We found a significant correlation between CDA genotype and OS in NK-AML, the degree of DNA methylation in AML cells, and in vitro drug sensitivity. The change in methylation related to CDA genotype may be associated with differences in drug activation and subsequent sensitivity, making these polymorphisms potential markers of use for future individual chemotherapy decisions such as dose adjustments.
Citation Format: Ingrid Jakobsen Falk, Anna Fyrberg, Monica Hermanson, Martin Höglund, Hareth Nahi, Lars Palmqvist, Christer Paul, Esbjörn Paul, Richard Rosenquist, Dick Stockelberg, Yuan Wei, Henrik Green, Kourosh Lotfi. Correlation between cytidine deaminase single nucleotide polymorphisms and in vitro drug sensitivity, DNA methylation and outcome in normal karyotype acute myelogenous leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1170. doi:10.1158/1538-7445.AM2013-1170