FLT3-ITD induces ara-C resistance in myeloid leukemic cells through the repression of the ENT1 expression

• Published in: Biochemical and biophysical research communications Vol. 390; no. 3; pp. 1001 - 1006
• Main Authors: Jin, Guilan, Matsushita, Hiromichi, Asai, Satomi, Tsukamoto, Hideo, Ono, Ryoichi, Nosaka, Tetsuya, Yahata, Takashi, Takahashi, Shinichiro, Miyachi, Hayato
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18.12.2009
• Subjects: Antimetabolites, Antineoplastic - pharmacology; Ara-C resistance; Cell Line, Tumor; Cytarabine - pharmacology; Down-Regulation; ENT1; Equilibrative Nucleoside Transporter 1 - antagonists & inhibitors; Equilibrative Nucleoside Transporter 1 - genetics; FLT3-ITD; fms-Like Tyrosine Kinase 3 - metabolism; Gene Expression Regulation, Leukemic; HIF-1α; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Leukemia, Myeloid, Acute - metabolism; Myeloid leukemia; Promoter Regions, Genetic; HIF-1α; Myeloid leukemia; FLT3-ITD; ENT1; Ara-C resistance
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2009.10.094

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-1α 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-1α, 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.