Fluorescent Sensors of Protein Kinases: From Basics to Biomedical Applications - Progress in Molecular Biology and Translational Science - page 260

and drug-resistant cells and can further be applied for direct evaluation of
kinase inhibitor efficacy. 48 This highly sensitive biosensor was therefore ap-
plied to assess Bcr-Abl activity from patient cells and further employed to
establish a correlation with the disease status: a clinical diagnosis of Bcr-Abl
kinase activity in CML. Moreover, this probe has been used to monitor re-
sponse to therapy and to detect the onset of drug-resistant cells, thereby all-
owing foreseeing when and how to employ second-generation inhibitors or
novel compounds to treat drug-resistant mutants. 95,96 Wang et al. developed
fluorescent peptide biosensors that are enzymatically and photophysically
distinct, allowing the simultaneous monitoring of Bcr-Abl and Lyn
tyrosine kinase activity through multicolor imaging. In particular, this
combination of orthogonal probes revealed significant differences in Lyn
kinase activity, but not in Abl kinase activity, between CML cell lines
that are sensitive to imatinib or which develop resistance to this drug. 128
It can be expected that the potential of fluorescent biosensors will be
harnessed for clinical diagnostics in the coming years, not only for early stage
detection but also for monitoring kinase activities throughout disease progres-
sion and for assessing the benefits of therapeutic intervention, drug efficiency,
and resistance, in particular, but not exclusively in the field of cancer. 152

4.3. Drug discovery strategies HTS/HCS assays and

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postscreening evaluation
Protein kinases constitute one of the major classes of therapeutic targets for
drug discovery programs developed by academia and the pharmaceutical in-
dustry. In this respect, fluorescent biosensors constitute sensitive and selec-
tive tools that provide a means of monitoring protein kinase activity in a
continuous fashion in vitro or in cell-based assays, in high-throughput and
high content screening assays. Indeed, fluorescent biosensors are particularly
well suited to screen large, complex libraries for inhibitors that affect enzy-
matic activity or function in high-throughput formats because of the high sen-
sitivity of response to compounds that affect kinase activity. Moreover, as
fluorescent reporters allow visualization of the activity of target enzymes in
a continuous fashion, they allow establishing screens that follow the action
of compounds on kinase activity over time, rather than at a static point. Fluo-
rescent biosensors are further well suited to the qualitative and quantitative
evaluation of kinase inhibitor efficacy in living cells at a postscreening stage,
to gain insight into the pharmacokinetics and pharmacodynamics of hits and
to determine the efficacy of novel leads and optimize derivative compounds
for therapeutic applications. Finally, biosensor technology can be employed to