Pharmacological and biochemical strategies to increase the accumulation of arabinofuranosylguanine triphosphate in primary human leukemia cells

Carlos O. Rodriguez, Jaswinder K. Legha, Elihu Estey, Michael J. Keating, Varsha Gandhi

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Purine nucleoside phosphorylase deficiency leads to a dGTP-mediated T- lymphopenia, suggesting that an analogue of deoxyguanosine would be selectively effective in T-cell disease. 9-β-D-Arabinofuranosylguanine (ara- G) is relatively resistant to hydrolysis by purine nucleoside phosphorylase and selectively toxic to T cells, but its low solubility has prevented its use in the clinic. 2-Amino-6-methoxy-arabinofuranosylpurine (GW506U) serves as the water-soluble prodrug for ara-G. A Phase I trial in patients with refractory hematological malignancies demonstrated that the clinical responses to this agent were directly related to the peak levels of ara-G 5'- triphosphate (ara-GTP) in target cells. The aim of the present study was to develop and test strategies to increase intracellular accumulation of ara- GTP in primary human leukemia cells of myeloid and B-lymphoid origin. Three strategies were tested. First, incubations with 100 μM ara-G for 4 h produced a linear median accumulation rate of 19 μM/h (range, 2-45 μM/h; n = 15) in lymphoid leukemia cells and 16 μM/h (range, 0.5-41 μM/h; n = 11) in myeloid leukemia cells. Saturation of ara-GTP accumulation was achieved only after 6-8 h exposure in both lymphoid and myeloid leukemia cells, suggesting a rationale for prolonged infusion. Second, a dose-dependent increase in ara-GTP accumulation was observed with incubations of 10-300 μM ara-G for 3 h. Hence, dosing regimens that achieve high plasma levels of ara- G during therapy may increase cellular levels of ara-GTP. Finally, a biochemical modulation approach using in vitro incubation of leukemia cells with 10 μM 9-β-D-arabinofuranosyl-2-fluoroadenine for 3 h, followed by either 50 or 100 μM ara-G for 4 h, resulted in a statistically significant median 1.3-fold (range, 1.1-9.0-fold; P = 0.034) and 1.8-fold (range, 0.9- 10.6 fold; P = 0.018) increase in ara-GTP compared to cells incubated with ara-G alone. Extension of these studies to ex vivo incubations confirmed our in vitro findings. These strategies will be used in the design of clinical protocols to increase ara-GTP accumulation in leukemia cells during therapy.

Original languageEnglish (US)
Pages (from-to)2107-2113
Number of pages7
JournalClinical Cancer Research
Issue number11
StatePublished - Nov 1997
Externally publishedYes

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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