Linked Life Data

14522924

Source:http://linkedlifedata.com/resource/pubmed/id/14522924

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
18
pubmed:dateCreated
2003-10-2
pubmed:abstractText
In common with other bioreductive drugs, metabolic reduction is required for activation of the benzotriazine-di-N-oxide tirapazamine (TPZ) in hypoxic regions of tumors. This same metabolism also consumes the drug as it diffuses, impeding its penetration into hypoxic tissue. In this study, we develop a pharmacokinetic (PK)/pharmacodynamic (PD) model for TPZ that explicitly includes its diffusion characteristics as measured in multicellular layer (MCL) cultures of HT29 colon carcinoma cells. The kinetics of TPZ metabolism to its mono-N-oxide derivative SR 4317, determined by high-performance liquid chromatography using anoxic HT29 single cell suspensions, demonstrated both a first order and saturable (K(m) = 3.6 micro M) component. Cell killing, assessed by clonogenic assay under the same conditions, demonstrated an approximately quadratic concentration dependence and linear time dependence. TPZ transport through MCLs, determined under hyperoxic conditions (95% O(2)) to suppress reductive metabolism, provided a concentration-independent diffusion coefficient of 0.40 x 10(-6) cm(2)s(-1). Under anoxia, this transport was strongly suppressed and was well predicted by the single cell metabolism parameters (scaled to the cell density in MCLs). These PK (transport) and PD (cytotoxicity) parameters were used to calculate cell killing as a function of distance in anoxic HT29 MCLs after the addition of TPZ to both sides of the MCL. The predicted average cell kill was in good agreement with measured values, which showed much less killing than for single cell suspensions under the same conditions. The success of this PK/PD model in predicting response in MCL shows that inefficient transport, rather than changes in intrinsic sensitivity, is responsible for TPZ resistance in these three-dimensional cell cultures and suggests that optimization of transport properties is a high priority in developing second-generation TPZ analogues.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0008-5472
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
63
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5970-7
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
Multicellular resistance to tirapazamine is due to restricted extravascular transport: a pharmacokinetic/pharmacodynamic study in HT29 multicellular layer cultures.
pubmed:affiliation
Auckland Cancer Society Research Centre, The University of Auckland, New Zealand. k.hicks@auckland.ac.nz
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't