Imaging of adenoviral-directed herpes simplex virus type 1 thymidine kinase reporter gene expression in mice with radiolabeled ganciclovir

Sanjiv S. Gambhir, Jorge R. Barrio, Lily Wu, Meera Iyer, Mohammad Namavari, Nagichettiar Satyamurthy, Eileen Bauer, Capella Parrish, Duncan C. MacLaren, Ali R. Borghei, Leeta A. Green, Susan Sharfstein, Arnold J. Berk, Simon R Cherry, Michael E. Phelps, Harvey R. Herschman

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275 Scopus citations

Abstract

We are developing procedures to repeatedly and noninvasively image the expression of transplanted reporter genes in living animals and in patients, using PET. We have investigated the use of the Herpes Simplex Virus type 1 thymidine kinase gene (HSV1-tk) as a reporter gene and [8-14C]-ganciclovir as a reporter probe. HSV1-tk, when expressed, leads to phosphorylation of [8- 14C]-ganciclovir. As a result, specific accumulation of phosphorylated [8- 14C]-ganciclovir should occur almost exclusively in tissues expressing the HSV1-tk gene. Methods: An adenoviral vector was constructed carrying the HSV1-tk gene along with a control vector. C6 rat glioma cells were infected with either viral vector and uptake of [8-3H]-ganciclovir was determined. In addition, 12 mice were injected with varying levels of either viral vector. Adenovirus administration in mice leads primarily to liver infection. Forty- eight hours later the mice were injected with [8-14C]-ganciclovir, and 1 hr later the mice were sacrificed and biodistribution studies performed. Digital whole-body autoradiography also was performed on separate animals. HSV1-tk expression was assayed, using both normalized HSV1-tk mRNA levels and relative HSV1-TK enzyme levels, in both the cell culture and murine studies. Results: Cell culture, murine tissue biodistribution and murine in vivo digital whole-body autoradiography all demonstrate the feasibility of HSV1- tk as a reporter gene and [8-14C]-ganciclovir as an imaging reporter probe. A good correlation (r2 = 0.86) between the [8-14C]-ganciclovir percent injected dose per gram tissue from HSV1-tk positive tissues and HSV1-TK enzyme levels in vivo was found. An initial study in mice with [8-18F]- fluoroganciclovir and microPET imaging supports further investigation of [8- 18F]fluoroganciclovir as a PET reporter probe for imaging HSV1-tk gene expression. Conclusion: These results demonstrate the feasibility of using [8-14C]-ganciclovir as a reporter probe for the HSV1-tk reporter gene, using an in vivo adenoviral mediated gene delivery system in a murine model. The results form the foundation for further investigation of [8-18F]- fluoroganciclovir for noninvasive and repeated imaging of gene expression with PET.

Original languageEnglish (US)
Pages (from-to)2003-2011
Number of pages9
JournalJournal of Nuclear Medicine
Volume39
Issue number11
StatePublished - Nov 1998
Externally publishedYes

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Keywords

  • Gene expression
  • Imaging
  • PET
  • Reporter gene
  • Thymidine kinase

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology

Cite this

Gambhir, S. S., Barrio, J. R., Wu, L., Iyer, M., Namavari, M., Satyamurthy, N., Bauer, E., Parrish, C., MacLaren, D. C., Borghei, A. R., Green, L. A., Sharfstein, S., Berk, A. J., Cherry, S. R., Phelps, M. E., & Herschman, H. R. (1998). Imaging of adenoviral-directed herpes simplex virus type 1 thymidine kinase reporter gene expression in mice with radiolabeled ganciclovir. Journal of Nuclear Medicine, 39(11), 2003-2011.