Biomedical Engineering Reference
In-Depth Information
Quantification of nilotinib, dasatinib, and bosutinib was done in K562 leukemia
cells by protein precipitation using acetonitrile, followed by triple quadrupole mass
spectrometer analysis operated in positive ion electrospray mode [
142
] . Nilotinib
and dasatinib were found to act both as transported substrates and, at high concen-
trations, inhibitors of
ABCB1
(gene coding for P-glycoprotein) and
ABCG2
(gene
coding for BCRP) [
142
]. Whereas neither ABCB1 nor ABCG2 could confer bosu-
tinib resistance; this TKI efficiently inhibited both transporters at higher concentra-
tions [
142
] .
In our laboratory, an assay has been developed for the determination of cellular
concentration of imatinib in peripheral blood monocytes cells (PBMCs) isolated
from patients [
42
]. Intracellular concentrations of imatinib were measured in
PBMCs from five patients using validated LC MS/MS methods [
42
] . The intra/
extracellular ratio appeared to be constant over the observation period indicating an
average eightfold accumulation of imatinib in cells. More recently, as part of our
in vitro studies on the consequence of drug transporters expression on TKIs disposi-
tion, we have developed a simplified methodology for the intracellular determina-
tion of several major TKIs (imatinib, nilotinib, dasatinb, sunitinib, and sorafenib) in
K562 cell lines [
143
]. Incubated cells were first extracted with 0.5 ml MeOH/H
2
O
50:50 by vortex mixing, ultrasonication, and centrifugation, yielding cellular
extracts. TKIs were subsequently quantified over the relevant concentration range
of 0.1-5,000 ng/ml with an adaptation of our validated multiplex LC-MS/MS
method [
122
]. These experiments have revealed that the differential expression and/
or function of P-gp was not affecting the cellular disposition of nilotinib, in contrast
to the other tested TKIs.
Lately, the development of an assay by LC coupled to single quadrupole mass
spectrometry has been recently published for the determination of cellular concen-
trations of imatinib, dasatinib, and nilotinib in PBMCs, but the authors did not give
much details on the results obtained with patients samples [
144
] .
In conclusion, the multiple-analytes LC-MS methods represent an improvement
over previous single-analyte methods in terms of convenience (a single extraction
procedure for several TKIs, reducing significantly the analytical time), sensitivity,
selectivity, and throughput. The current facilitated access to LC-MS technology may
contribute to filling our current knowledge gap in the pharmacokinetics-pharmaco-
dynamics relationships of the latest TKIs developed following imatinib. It might
better define therapeutic ranges of TKIs in various patient populations prior to the
evaluation of a systematic TDM-guided dose adjustment of these anticancer drugs.
3
Tamoxifen as the First Targeted Anticancer Agent
Introduced into the clinic some 30 years ago, tamoxifen selectively modulates estro-
gen receptors and thus can be considered as one of the first examples of “targeted”
anticancer therapy, years before the era of TKIs described in Section 2. This largely
justifies that a section of the present review is devoted to tamoxifen, especially in
