Functional role of alternatively spliced deoxycytidine kinase in sensitivity to cytarabine of acute myeloid leukemic cells

• Published in: Blood Vol. 99; no. 4; pp. 1373 - 1380
• Main Authors: Veuger, Marjan J.T., Heemskerk, Mirjam H.M., Honders, M. Willy, Willemze, Roel, Barge, Renée M.Y.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 15.02.2002; The Americain Society of Hematology
• Subjects: Acute Disease; Alternative Splicing - physiology; Animals; Antineoplastic agents; Biological and medical sciences; Bone Marrow Cells - pathology; Cell Survival - drug effects; Chemotherapy; Cytarabine - antagonists & inhibitors; Cytarabine - pharmacology; Cytarabine - therapeutic use; Deoxycytidine Kinase - genetics; Deoxycytidine Kinase - metabolism; Deoxycytidine Kinase - pharmacology; Dose-Response Relationship, Drug; Drug Resistance; Hematologic and hematopoietic diseases; Humans; Leukemia, Myeloid - drug therapy; Leukemia, Myeloid - pathology; Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis; Medical sciences; Pharmacology. Drug treatments; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein Isoforms - pharmacology; Rats; Transduction, Genetic; Tumor Cells, Cultured - drug effects; Antineoplastic agent; Human; Treatment resistance; Enzyme; Transferases; Acute; Malignant hemopathy; In vitro; Mechanism; Chemotherapy; Deoxycytidine kinase; Sensitivity; Cytarabine; Antimetabolic; Lymphoproliferative syndrome; Established cell line; Mechanism of action; Pyrimidine nucleoside; Acute myelocytic leukemia
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V99.4.1373

Development of resistance to cytarabine (AraC) is a major problem in the treatment of patients with acute myeloid leukemia (AML). Inactivation of deoxycytidine kinase (dCK) plays an important role in AraC resistance in vitro. We have identified inactive, alternatively spliced dCK forms in leukemic blasts from patients with resistant AML. Because these dCK-spliced variants were only detectable in resistant AML, it was hypothesized that they might play a role in AraC resistance in vivo. In the current study, the biologic role of the alternatively spliced dCK forms in AraC resistance was further investigated by retroviral transductions in rat leukemic cells. Introduction of inactive, alternatively spliced dCK forms into AraC-resistant K7 cells, with no endogenous wild-type (wt) dCK activity, could not restore AraC sensitivity, whereas wt dCK fully restored the AraC-sensitive phenotype. Transfection of alternatively spliced dCK forms into AraC-sensitive KA cells, as well as in human leukemic U937 cells and in phytohemagglutinin-stimulated T cells, did not significantly change sensitivity toward AraC. In addition, cotransduction of wt dCK with alternatively spliced dCK in K7 cells did not result in altered sensitivity to AraC compared with K7 cells only transduced with wt dCK. These data indicate that the alternatively spliced dCK forms cannot act as a dominant-negative inhibitor on dCK wt activity when they are coexpressed in a single cell. However, a cell expressing alternatively spliced dCK forms that has lost wt dCK expression is resistant to the cytotoxic effects of AraC.