A New Acycloguanosine-Specific Supermutant of Herpes Simplex Virus Type 1 Thymidine Kinase Suitable for PET Imaging and Suicide Gene Therapy for Potential Use in Patients Treated with Pyrimidine-Based Cytotoxic Drugs

• DOI: 10.2967/jnumed.107.046425
• Publication Date: 2008-04-16T00:58:45Z
• Authors: Yury Likar; Konstantin Dobrenkov; Malgorzata Olszewska; Elena Vider; Larissa Shenker; Shangde Cai; Nagavarakishore P...; Hedvig Hricak; Vladimir Ponomarev
• Keywords: Thymidine kinase; Suicide gene

The herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene is widely used as a suicide in combination with ganciclovir (GCV) and nuclear imaging reporter an appropriate probe. Wild-type HSV1-tk recognizes variety of pyrimidine acycloguanosine nucleoside analogs, including clinically antiviral drugs. PET expression will be compromised patients receiving nucleoside-based treatment. With the use acycloguanosine-specific mutant enzyme, can successfully performed acycloguanosine-based radiotracers without interference from pyrimidine-based <b>Methods:</b> levels wild-type HSV1-A167Ytk, HSV1-sr39tk, HSV1-A167Ysr39tk mutants fused green fluorescent protein (GFP) transduced into U87 cells were normalized to mean fluorescence GFP measured by fluorescence-activated cell sorting. enzymatic activities its compared 2-h vitro radiotracer uptake assays ³H-2′-fluoro-2′-deoxy-1-β-d-arabinofuranosyl-5-ethyluracil (³H-FEAU), ³H-pencyclovir (³H-PCV), ³H-GCV drug sensitivity assays. ¹⁸F-FEAU ¹⁸F-9-[4-fluoro-3-(hydroxymethyl)butyl]guanine (¹⁸F-FHBG) was mice established subcutaneous tumors, expressing mutants, followed tissue sampling. <b>Results:</b> FEAU accumulation not detected HSV1-A167Ysr39tk–expressing xenografts. Lack conversion derivatives supermutant also confirmed assay, which 50% inhibitory concentrations for thymine 1-β-d-arabinofuranoside bromovinyldeoxyuridine found similar those nontransduced cells. In contrast, we that could readily phosphorylate at HSV1-A167Ytk but showed enhanced activity ³H-PCV ¹⁸F-FHBG vivo. <b>Conclusion:</b> We developed new gene, HSV1-A167Ysr39tk, exhibits specificity high phosphorylation derivatives. resulting suicidal therapy protocols GCV treated cytotoxic