ABSTRACT
This chapter describes the novel reporter probes radiolabeled with various radioisotopes that are developed and currently used in the laboratory research and preclinical and clinical trials for imaging Herpes simplex virus type 1 thymidine kinase (HSV1-tk). Cancer cells are transduced with a retroviral vector carrying HSV1-tk gene. The purine nucleoside analogues radiolabeled for imaging HSV1-tk gene expression includes primarily acycloguanosine analogues, and only one compound with the cyclic sugar. High levels of HSV1-tk expression ensure sufficient prodrug ganciclovir conversion and activation for bystander effects that kill the surrounding untransduced tumor cells. The most advantage with F-fluoro-3-hydroxymethyl-butyl guanine is its approval by the food and drug administration for its clinical applications; and fluoro-5-ethyl-1-β-d-arabinofuranosyluracil is under the process of submission for an investigational new drug. CED does not increase adenoviral vector distribution in a glioma xenograft model compared with single injection (SI). CED and SI resulted in equal uptake of radioactivity in the tumors.
