Metabolic pathways for the activation of the antiviral agent 2',3'- dideoxyguanosine in human lymphoid cells

LL Bondoc , G Ahluwalia, DA Cooney, NR Hartman, DG Johns and A Fridland

Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.

2',3'-Dideoxyguanosine (ddGuo) is a selective inhibitor of the replication of human immunodeficiency virus in vitro and the most active antihepadnavirus nucleoside analog known in vitro and in vivo, in a Peking duck model. However, the exact route by which this and related guanosine analogs are anabolized to their putative active metabolites in target cells is controversial. The anabolic pathway for the activation of ddGuo was investigated with the use of mutant human lymphoid CCRF-CEM and WI-L2 cell lines deficient in known nucleoside kinases. Uptake of ddGuo by human lymphoid cells and subsequent conversion to mono-, di-, and triphosphorylated metabolites is dose dependent and occurs proportionately to the exogenous concentration of drug. Studies with kinase-deficient CCRF-CEM and WI-L2 mutants revealed that at least two different routes of metabolism are operating in these cells to initiate the phosphorylation of ddGuo to its active dideoxynucleotides, one being deoxycytidine (dCyd) kinase and the other a cytosolic-5'-nucleotidase acting in the anabolic direction as a phosphotransferase. The evidence for this included 1) a lower but significant accumulation of drug anabolites in dCyd kinase-deficient mutants, 2) a lack of cross-resistance of the kinase-deficient mutants to growth inhibition by ddGuo, compared with that by the related analogs dideoxycytidine and arabinosylcytosine, known substrates for dCyd kinase, and 3) identification of different phosphorylation activities for ddGuo in extracts of wild-type cells and kinase- deficient mutants. Knowledge of the enzyme systems involved in anabolism of ddGuo analogs should be important for both new drug design and optimal therapeutic application.

Volume 42, Issue 3, pp. 525-530, 09/01/1992
Copyright © 1992 by American Society for Pharmacology and Experimental Therapeutics

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