Epidermal growth factor receptors (EGFRs) belong to the ErbB family of receptor tyrosine kinases (TKs).
Based on the role of EGFR signaling pathway in malignant progression of various types of tumors, a growing interest in
the use of EGFR-TK inhibitors as probes for molecular imaging of EGFR-overexpressing tumors via positron emission
tomography (PET) and single photon emission computed tomography (SPECT) is being notable. On one side, such noninvasive
and repetitive monitoring of the activity of EGFR at the kinase level is intended to provide a direct measure of
EGFR occupancy and inhibition by EGFR-targeting drugs. On the other side, all oncologic imaging tracers are molecularly
targeted radiopharmaceuticals, which are strongly dependent on the tumor biochemistry including increased metabolism,
hyperproliferation, angiogenesis, hypoxia, apoptosis, and specific tumor biomarkers (tumor specific antigens and
tumor-specific receptors). The present article is an attempt to reconcile these two vital standpoints influencing the choice
of appropriate radiolabeled agents for PET and SPECT imaging aimed to support the development of a new generation of
multi-targeted kinase inhibitors in the time ahead, because the routine accomplishment of drug selectivity for particular
protein kinases is a substantial challenge.
Keywords: EGFR, Growth factor, Imaging, Inhibitor, PET/SPECT, Receptor, Tumor targeting, Tyrosine kinase
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