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  • Title: FLT3-ITD induces ara-C resistance in myeloid leukemic cells through the repression of the ENT1 expression.
    Author: Jin G, Matsushita H, Asai S, Tsukamoto H, Ono R, Nosaka T, Yahata T, Takahashi S, Miyachi H.
    Journal: Biochem Biophys Res Commun; 2009 Dec 18; 390(3):1001-6. PubMed ID: 19853583.
    Abstract:
    Fms-related tyrosine kinase 3-internal tandem duplications (FLT3-ITD) are strongly associated with the refractory nature of acute myeloid leukemia (AML) by the standard combined chemotherapy. FLT3-ITD-expressing murine and human myeloid cell lines, HF6/FLT3-ITD and K562/FLT3-ITD cells, respectively, were developed in order to clarify whether FLT3-ITD is involved in the resistance to cytotoxic agents in AML. Both of these cell lines were specifically resistant to the pyrimidine analogue cytosine arabinoside (ara-C), an essential agent for AML, accompanied by the downregulation of equilibrative nucleoside transporter 1 (ENT1), a transporter responsible for the cellular uptake of ara-C. The ENT1 promoter activity and the cellular uptake of ara-C were reduced in K562/FLT3-ITD cells, and rescued by pretreating the cells with PKC412, a FLT3 inhibitor. In addition, the expression of hypoxia inducible factor 1 alpha subunit (HIF1A) transcripts was upregulated in K562/FLT3-ITD cells, and the induction of HIF-1alpha reduced the promoter activity of ENT1 gene in K562 cells. Taken together, these findings suggest that FLT3-ITD specifically induces ara-C resistance in leukemic cells by the repression of ENT1 expression, possibly through the upregulation of HIF-1alpha, while also partially accounting for the poor prognosis of AML with FLT3-ITD due to resistance to the standard chemotherapy protocols which include ara-C.
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