Pharmacological and biochemical strategies to increase the accumulation of arabinofuranosylguanine triphosphatein primary human leukemia cells.

Abstract

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-beta-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 microM ara-G for 4 h produced a linear median accumulation rate of 19 microM/h (range, 2-45 microM/h; n = 15) in lymphoid leukemia cells and 16 microM/h (range, 0.5-41 microM/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 microM 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 microM 9-beta-D-arabinofuranosyl-2-fluoroadenine for 3 h, followed by either 50 or 100 microM 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.

• Authors: C O Rodriguez Jr, J K Legha, E Estey, M J Keating, V Gandhi
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 3 Issue 11 Pg. 2107-13 (Nov 1997) ISSN: 1078-0432 [Print] United States
• PMID: 9815603 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antineoplastic Agents
• Arabinonucleosides
• Arabinonucleotides
• 9-arabinofuranosylguanine
• 9-beta-D-arabinofuranosylguanosine 5'-triphosphate
• Guanosine Triphosphate

Topics

• Antineoplastic Agents (blood, pharmacokinetics)
• Arabinonucleosides (blood, pharmacokinetics)
• Arabinonucleotides (blood, pharmacokinetics)
• Biotransformation
• Guanosine Triphosphate (analogs & derivatives, blood, pharmacokinetics)
• Humans
• In Vitro Techniques
• Kinetics
• Leukemia (blood)
• Leukemia, B-Cell (blood)
• Leukemia, Myeloid (blood)