Determinants of sensitivity of human T-cell leukemia CCRF-CEM cells to immucillin-H
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- 作者：Min Huang ; Yanhong Wang ; Jingjin Gu ; Jing Yang ; Karen Noel ; Beverly S. Mitchell ; Vern L. Schramm ; Lee M. Graves
- 关键词：Immucillin ; T-cell leukemia ; Nucleoside transporters ; Deoxycytidine kinase ; Hypoxanthine– ; guanine phosphoribosyltransferase ; Deoxyguanosine
- 刊名：Leukemia Research
- 出版年：2008
- 出版时间：August 2008
- 年：2008
- 卷：32
- 期：8
- 页码：1268-1278
- 全文大小：678 K
文摘
Immucillin-H (BCX-1777, forodesine) is a transition state analogue and potent inhibitor of PNP that shows promise as a specific agent against activated human T-cells and T-cell leukemias. The immunosuppressive or antileukemic effects of Immucillin-H (ImmH) in cultured cells require co-administration with deoxyguanosine (dGuo) to attain therapeutic levels of intracellular dGTP. In this study we investigated the requirements for sensitivity and resistance to ImmH and dGuo. 3H-ImmH transport assays demonstrated that the equilibrative nucleoside transporters (ENT1 and ENT2) facilitated the uptake of ImmH in human leukemia CCRF-CEM cells whereas 3H-dGuo uptake was primarily dependent upon concentrative nucleoside transporters (CNTs). Analysis of lysates from ImmH-resistant CCRF-CEM-AraC-8D cells demonstrated undetectable deoxycytidine kinase (dCK) activity, suggesting that dCK and not deoxyguanosine kinase (dGK) was the rate-limiting enzyme for phosphorylation of dGuo in these cells. Examination of ImmH cytotoxicity in a hypoxanthine–guanine phosphoribosyltransferase (HGPRT)-deficient cell line CCRF-CEM-AraC-8C, demonstrated enhanced sensitivity to low concentrations of ImmH and dGuo. RT-PCR and sequencing of HGPRT from the HGPRT-deficient CCRF-CEM-AraC-8C cells identified an Exon 8 deletion mutation in this enzyme. Thus these studies show that specific nucleoside transporters are required for ImmH cytotoxicity and predict that ImmH may be more cytotoxic to 6-thioguanine (6-TG) or 6-thiopurine-resistant leukemia cells caused by HGPRT deficiency.