A New Pyrimidine-Specific Reporter Gene: A Mutated Human Deoxycytidine Kinase Suitable for PET During Treatment with Acycloguanosine-Based Cytotoxic Drugs

In this article, we describe a series of new human-derived reporter genes based on human deoxycytidine kinase (dCK) suitable for clinical PET. Methods: Native dCK and its mutant reporter genes were tested in vitro and in vivo for their phosphorylation of pyrimidine-and acycloguanosine-based radiotracers including 2'-deoxy-2'-fluoroarabinofuranosylcytosine, 2'-fluoro-2'-deoxyarabinofuranosyl-5-ethyluracil (FEAU), penciclovir, and 9-[4-fluoro-3-(hydroxymethyl)butyl]guanine (FHBG) and clinically applied antiviral and anticancer drugs. Results: Cells transduced with dCK mutant reporter genes showed high in vitro and in vivo uptake of pyrimidine-based radiopharmaceuticals (F-18-FEAU) comparable to that of herpes simplex virus type-1 thymidine kinase (HSV1-tk)-transduced cells. These mutants did not phosphorylate acycloguanosine-based radiotracers (F-18-FHBG) or antiviral drugs (ganciclovir). Furthermore, the mutants displayed suicidal activation of clinically used pyrimidine-based prodrugs (cytarabine, gemcitabine). Conclusion: The mutants of human dCK can be used as pyrimidine-specific PET reporter genes for imaging with F-18-FEAU during treatment with acycloguanosine-based antiviral drugs. Additionally, the prosuicidal activity of these reporters with pyrimidine-based analogs will allow for the safe elimination of transduced cells.