gateway the newsletter of the snm molecular imaging center of excellence

gateway the newsletter of the snm molecular imaging center of excellence Reporter Genes for Molecular and Cellular Imaging With more than 20,000 genes in the human genome now identified and a similar number of genes in the rat and mouse genome known (1), explanation of the function of genes has become the next major challenge. Clarification of the function of genes has been facilitated by the development of reporter genes, which are revolutionizing the way many current biomedical studies are designed and performed. A reporter gene is a gene whose product can be readily detected and either be fused to the gene of interest or can replace it. The main applications for these reporters include monitoring gene expression levels, investigating dynamic molecular interactions between proteins, studying cellular interactions, tracking cells in normal and abnormal development or in cell transplantation therapy, and monitoring gene replacement therapy. Optical reporter genes are probably the most commonly used and widely developed for imaging. Throughout the years, multiple genes were cloned from a variety of organisms that emit light via bioluminescence or fluorescence in multiple distinguishable wave lengths. Probably the most recent and exciting implementation of optical reporter genes was the development of the transgenic " brainbow " mouse, in which combinatorial expression of fluorescent proteins in the mouse brain resulted in the production of more than 89 distinguishable colors (2). An emerging new class of reporter genes encodes for proteins with affinity for radioisotopes or positron emitter probes. These receptors, transporters or enzymes can provide quantitative images on administration of suitable radiolabeled probes (3). MRI reporter genes are unique among all reporter genes used with the various imaging modalities because they can provide information on gene expression that can be coregistered with anatomic and functional information (4). With the approval of the first multi-center IND for 18 F-fluorothymidine (FLT) in September of this year, the SNM Clinical Trails Network has achieved an important early success toward integrating imaging biomarkers into therapeutic clinical trials. Previously, FLT had been available for investigational use only at a limited number of individual clinical centers that have Food and Drug Administration (FDA) single-center INDs in place. As a result of obtaining the first centralized molecular imaging IND, reproducible, standardized investigational imaging will be achievable within multicenter clinical trials using the imaging agent. FLT is an investigational positron emission tomography (PET) imaging bio-marker that has apparent promise for demonstration of …