1. ¹Department of Radiation Oncology, Detroit, Michigan 48202, USA
2. ²Department of Nuclear Medicine, Detroit, Michigan 48202, USA
3. ³Department of Urology, Detroit, Michigan 48202, USA
4. ⁴Department of Bioresources, Detroit, Michigan 48202, USA
5. ⁵Department of Anesthesiology, Henry Ford Health Systems, Detroit, Michigan 48202, USA
6. ⁶Department of Physiology and Cell Biology, Ohio State University, Columbus, Ohio 43210, USA

Correspondence: Svend O. Freytag, Molecular Biology Research, Henry Ford Health Systems, One Ford Place, Wing 5D, Detroit, MI 48202-3450. Fax: (313) 876-1950. E-mail: sfreyta1@hfhs.org.

Received 21 February 2003; Accepted 24 April 2003.

Abstract

With the goal of optimizing adenovirus-mediated suicide gene therapy for prostate cancer, we have developed a method based on the human sodium iodide symporter (hNIS) that allows for noninvasive monitoring of adenoviral vectors and quantification of gene expression magnitude and volume within the prostate. A replication-competent adenovirus (Ad5-yCD/mutTK_SR39rep-hNIS) coexpressing a therapeutic yeast cytosine deaminase (yCD)/mutant herpes simplex virus thymidine kinase (mutTK_SR39) fusion gene and the hNIS gene was developed. Ad5-yCD/mutTK_SR39rep-hNIS and a replication-defective hNIS adenovirus (rAd-CMV-FLhNIS) were injected into contralateral lobes of the dog prostate and hNIS activity was monitored in live animals following administration of Na^99mTcO₄ using gamma camera scintigraphy. Despite the close proximity of the urinary bladder, ^99mTcO₄^- uptake was readily detected in the prostate using viral dose levels (10¹⁰ to 10¹² viral particles) that have been safely administered to humans. Due to its rapid clearance and short physical half-life (6 h), it was possible to obtain daily measurements of ^99mTcO₄^- uptake in vivo, allowing for dynamic monitoring of reporter gene expression within the prostate as well as biodistribution throughout the body. High-resolution autoradiography of prostate sections coupled with 3D reconstruction of gene expression demonstrated that the magnitude and volume of gene expression could be quantified with submillimeter resolution. Implementation of the GENIS (gene expression of Na/I symporter) technology in the clinic will facilitate optimization of future human gene therapy trials.