In Vivo Imaging of Mesenchymal Stem Cell Recruitment into the Tumor Stroma of Hepatocellular Carcinoma (HCC) Using a HIF-Specific Sodium Iodide Symporter (NIS) Gene System

The tumor-homing property of mesenchymal stem cells (MSCs) has lead to their use as delivery vehicles for therapeutic genes. The application of the sodium iodide symporter (NIS) as reporter and therapy gene allows non-invasive imaging of MSC biodistribution and functional transgene expression by 123I-scintigraphy or PET-imaging, as well as therapeutic application of 131I. Hypoxia-inducible factor 1 (HIF-1) is a key mediator of the cellular response to hypoxia and therefore highly expressed in solid malignancies. Placing NIS under the control of the HIF-1-promoter should consequently allow tumor-specific NIS expression after MSC-mediated delivery.