Linked Life Data

9815818

Source:http://linkedlifedata.com/resource/pubmed/id/9815818

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1999-2-25
pubmed:abstractText
Fludarabine and 1-beta-D-arabinofuranosylcytosine (ara-C) are effective nucleoside analogues for the treatment of leukemias when used as single agents or together. Recent trials of the fludarabine and ara-C therapy with or without growth factors suggested an improved clinical response by combining fludarabine and ara-C. The activity of these antimetabolites depends on their phosphorylation to the respective triphosphates, F-ara-ATP and ara-CTP. The principal mechanism through which these triphosphates cause cytotoxicity is incorporation into DNA and inhibition of further DNA synthesis. A model system of DNA primer extension on a defined template sequence was used to quantitate the consequences of incorporation of one or two analogues by human DNA polymerase alpha (pol alpha). The template (31-mer) was designed so that DNA pol alpha incorporated six deoxynucleotides (alternately G and T) on the 17-mer primer, followed by insertion of an A and then a C. The primer was then elongated with G and T to the full-length product. The apparent Kms of DNA pol alpha to incorporate these analogues (0. 053 and 0.077 microM, respectively) were similar to the Km for dCTP (0.037 microM) and dATP (0.044 microM), suggesting that the enzyme recognized these analogues and incorporated them efficiently on the growing DNA primer. The velocity of extension (Vmax) of these primers ranged between 0.53 and 0.77%/min when normal nucleotides were present. Once inserted at the 3'-terminus, F-ara-AMP or ara-CMP were poor substrates for extension. However, in reactions lacking dCTP and dATP and with high concentrations of ara-CTP, ara-CMP was inserted by pol alpha after incorporation of the F-ara-AMP residue. This tandem incorporation of the two analogues resulted in almost complete inhibition (99.3%) of further extension of the primer. In the presence of competing deoxynucleotides, each analogue resulted in a dose-dependent inhibition of DNA synthesis. When present together, inhibition of the primer elongation was more than additive at low concentrations of analogue triphosphates. Based on these results and the intracellular pharmacokinetics of ara-CTP and F-ara-ATP in leukemia blasts, we propose a pharmacodynamic model to explain interactions between these analogues during combination chemotherapy.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
1078-0432
pubmed:author
pubmed:issnType
Print
pubmed:volume
3
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1347-55
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Incorporation of fludarabine and 1-beta-D-arabinofuranosylcytosine 5'-triphosphates by DNA polymerase alpha: affinity, interaction, and consequences.
pubmed:affiliation
Department of Clinical Investigation, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't