Biography
Biography: Margarida Barroso
Abstract
Traditional cancer therapy generally leads to harmful side effects, thus warranting development of targeted therapies, which are better tolerated by cancer patients. Our goal is to develop in vivo non-invasive optical imaging assays for optimization of anti-cancer drug targeted therapy. We have established a fluorescence lifetime Förster Resonance Energy Transfer (FL-FRET) non-invasive whole-body in vivo tomographic imaging technique that can discriminate bound and internalized near-infrared (NIR)-labeled transferrin (Tfn) from free, soluble NIR-Tfn. This FRET-based assay exploits the homodimeric nature of transferrin receptor (TFR) that binds two molecules of Tfn in close proximity to determine dimerization and internalization of TFR-Tfn complexes into cancer cells. The Tfn FRET assay has been validated in vitro by visible and NIRFRET microscopy. FL-FRET tomographic imaging in vivo has been used to measure the internalization of tail-vein injected NIR-Tfn into human breast T47D tumor xenografts in live nude mice. Quantification of FRET donor % (FD%) in T47D tumor xenografts in vivo, indicates a higher proportion of FD% with increasing acceptor:donor ratio, demonstrating tumor uptake of NIR-Tfn. Tfn uptake concentration curve shows high sensitivity of FL-FRET imaging using NIR-Tfn as low as 10µg/ml of blood. Furthermore, relative high FD% for holo-Tfn (iron-loaded) compared to that of apo-Tfn (iron-depleted) demonstrates specific TFR-mediated uptake of holo-Tfn by T47D tumor xenografts, as expected since iron-depleted apo-Tfn shows reduced binding affinity towards TFR. In conclusion, we have successfully demonstrated the quantitative receptor-mediated uptake of Tfn into human breast tumors in vivo using a novel non-invasive NIR FL-FRET tomographic imaging assay.