Deoxycytidine Kinase (DCK) Mutations in Human Acute Myeloid Leukemia Resistant to Cytarabine

Abstract

Resistance to cytarabine is an important cause of therapy failure in persons with acute myeloid leukemia (AML). Deoxycytidine kinase, encoded by <i>DCK</i>, catalyzes phosphorylation of cytarabine to cytarabine monophosphate, a necessary step for eventual incorporation of cytarabine triphosphate into DNA and for clinical efficacy. Whether <i>DCK</i> mutations make AML cells resistant to cytarabine is controversial. We studied <i>DCK</i> mutations and messenger RNA (mRNA) concentrations in leukemia cells from 10 subjects with AML who received cytarabine-based therapy and relapsed and in 2 artificially induced cytarabine-resistant AML cell lines. <i>DCK</i> mutations were detected in 4 subjects with AML relapsing after achieving a complete remission and receiving high-dose cytarabine postremission therapy. Most mutations were in exons 4–6 and were not present before therapy. <i>DCK</i> was also mutated in cytarabine-resistant but not parental AML cell lines. <i>DCK</i> mRNA concentrations were significantly decreased in cytarabine-resistant K562 and SHI-1 cells compared with cytarabine-sensitive parental cells. Mutation frequency of <i>DCK</i> and mRNA concentration did not correlate with the extent of cytarabine resistance indicating other factors operate. Overexpression of wild-type <i>DCK</i> restored cytarabine sensitivity to previously resistant leukemia cell lines. Our data contribute to the understanding of cytarabine resistance in persons with AML.