Tumour imaging by Positron Emission Tomography using fluorinase generated 5-[18F]fluoro-5-deoxyribose as a novel tracer

Introduction: 5-[F-18]Fluoro-5-deoxyribose ([F-18]FDR) 3 was prepared as a novel monosaccharide radiotracer in a two-step synthesis using the fluorinase, a C-F bond forming enzyme, and a nucleoside hydrolase. The resulting [F-18]FDR 3 was then explored as a radiotracer for imaging tumours (A431 human epithelial carcinoma) by positron emission tomography in a mice model. Methods: 5-[F-18]Fluoro-5-deoxyribose ([F-18]FDR) 3, was prepared by incubating S-adenosyl-L-methionine (SAM) and [F-18]fluoride with the fluorinase enzyme, and then incubating the product of this reaction, [F-18]-5'-fluoro-5'-deoxadenosine ([F-18]FDA) 2, with an adenosine hydrolase to generate [F-18]FDR 3. The enzymes were freeze-dried and were used on demand by dissolution in buffer solution. The resulting [F-18]FDR 3 was then administered to four mice that had tumours induced-from the A431 human epithelial carcinoma cell line. Results: The tumour (A431 human epithelial carcinoma) bearing mice were successfully imaged with [F-18]FDR 3. The radiotracer displayed good tumour imaging resolution. A direct comparison of the uptake and efflux of [F-18]FDR 3 with 2-[F-18]fluoro-2-deoxyglucose ([F-18]FDG) was made, revealing comparative tumour uptake and imaging potential over the first 10-20 min. The study revealed however that [F-18]FDR 3 does not accumulate in the tumour as efficiently as [F-18]FDG over longer time periods. Conclusions: [F-18]FDR 3 can be rapidly synthesised in a two enzyme protocol and used to image tumours in small animal models. (C) 2013 Elsevier Inc. All rights reserved.