Blood, 15 February 2002, Vol. 99, No. 4, pp. 1373-1380
NEOPLASIA
Functional role of alternatively spliced deoxycytidine kinase in
sensitivity to cytarabine of acute myeloid leukemic cells
Marjan J. T. Veuger,
Mirjam
H. M. Heemskerk,
M. Willy Honders,
Roel Willemze, and
Renée M. Y. Barge
From the Laboratory of Experimental Hematology,
Department of Hematology, Leiden University Medical Center, The
Netherlands
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.
