In vivo evaluation of 2′-deoxy-2′-[18F]fluoro-5-iodo-1-β-D-arabinofuranosyluracil ([18F]FIAU) and 2′-deoxy-2′-[18F]fluoro-5-ethyl-1-β-D-arabinofuranosyluracil ([18F]FEAU) as markers for suicide gene expression

Purpose FIAU and FEAU were evaluated in vitro and in vivo as markers for HSV1-tk gene expression. Methods In vitro and biodistribution studies were performed in wild type and transduced HT-29 cells using [C-14]FIAU and [H-3]FEAU. PET imaging was performed using [F-18]FIAU and [F-18]FEAU. In vitro uptake of [C-14]FIAU in tk-positive cells was 39-fold, 49-fold, and 43-fold higher (p<0.001) than in wild type cells at 30, 60, and 120 min, respectively. Uptake of [H-3]FEAU in transduced cells was 46-fold, 62-fold, and 121-fold higher (p<0.001) than in wild type cells at the same time points. In vivo uptake of [C-14]FIAU at 2 h in HSV1-tk positive tumors was 15.48 +/- 3.94, 6.7-fold higher (p<0.001) than in wild type tumors. Uptake of [H-3]FEAU in transduced tumors was 9.98 +/- 1.99, 5.0-fold higher (p<0.001) than in wild type tumors. Micro-PET images using [F-18]FIAU and [F-18]FEAU also showed very high uptake in HSV-tk tumors. [F-18]FIAU and [F-18]FEAU appear to be potential PET imaging agents for gene expression.