Multi-modal Cell Labelling for Quantification and Optimization of Stem Cell Delivery to Orthotopic Breast Tumors

Stem cells have been utilized as anti-cancer agents due to their ability to home to and integrate within tumors. Methods to augment stem cell homing to tumors are being investigated with the goal of enhancing treatment efficacy. However, it is currently not possible to evaluate both cell localization and cell viability after engraftment, hindering optimization of therapy. In this study, luciferase expressing human adipocyte derived stem cells (ADSCs) were labelled with superparamagnetic iron oxide nanoparticles (SPIONs) conjugated to Indium-111 to produce cells with tri-modal imaging capabilities. ADSCs were administered intravenously (IV) or intracardially (IC) to mice bearing 4T1 orthotopic breast tumors. Cell fate was monitored serially using bioluminescence imaging (BLI) as a measure of cell viability, magnetic resonance imaging (MRI) for cell localization and single photon emission computer tomography (SPECT) for cell quantification. BLI/MRI/SPECT imaging revealed differences in whole body cell distribution between injection routes. BLI showed the presence of viable ADSCs within tumors as early as 1-hour post IC injection compared to 3 days post IV injection. SPECT data showed the percentage of ADSCs within tumors to be 2-fold higher after IC than IV at 5-hour post injection. Whereas, MRI confirmed the localization of SPION labelled cells in tumors after IC injection but not IV. Finally, histological analysis was used to validate engraftment of ADSC within tumor tissue. These findings demonstrate that multi-modal imaging can be used to evaluate the efficiency of stem cell delivery to tumors and that IC cell administration is more effective for tumor targeting.