Probing real-time response to multitargeted tyrosine kinase inhibitor 4-n-(3'-Bromo-Phenyl) amino-6, 7-dimethoxyquinazoline in single living cells using biofuntionalized quantum dots

Recently, the quinazolinederivative, 4-N-(3'-bromo-phenyl) amino-6, 7-dimethoxyquinazoline (PD153035), has been reported not only to inhibit the epidermal growth factor receptor (EGFR) tyrosine kinase but also to bind to DNA double helical structures by intercalation. However, several important pharmacology issues such as whether PD153035 is a specific and reversible inhibitor of the EGFR tyrosine kinase should be addressed in more detail. In this study, we propose a nanotechnology-based approach to monitoring the real-time EGF-EGFR complex trafficking process and its relationship to cytoskeleton, as well as spatio-temporal cellular response to PD153035 at the single-cell level. We utilize the biofunctionalized quntum dots (QDs) conjugated with EGF to monitor the cellular distribution of QD-EGF-EGFR complexes, which can provide a more direct access to probing the spatio-temporal distribution of EGF-EGFR complex in the absence and presence of PD153035. We found that QD-EGF-EGFR complexes undergo retrograde transport before receptor-mediated internalization. In addition, QD-EGF-EGFR complexes colocalize with actin filaments, especially in filopodia regions. Furthermore, the cellular distribution of fluorescing QDs was strongly localized inside the cell after washing PD153035 for time period longer than 15 minutes. This observation demonstrated that PD153035 could be removed from the intracellular kinase domain, namely, PD153035 is a reversible EGFR inhibitor. We anticipate these approaches based on the platform at single-cell level could be applied to build a quick screening method for detection and treatment evaluation of many types of cancer expressed high levels of EGFR.