Enhanced Peptide Radiotherapy of Prostate Cancer Using Targeted Adenoviral Vectors
Abstract
An adenovirus encoding the genes for human somatostatin receptor subtype 2 and bacterial cytosine deaminase (AdSSTR2CD) was constructed. The SSTR2 allows for non-invasive imaging of gene transfer and therapy with radiolabeled somatostatin analogues. The CD converts the prodrug 5-fluorocytosine (5-FC) to the toxic and radiosensitzing 5-fluorouracil (5-FU). Thus, it is hypothesized that AdSSTR2CD can be used for the simultaneous expression of SSTR2 and CD for the detection and treatment of prostate cancer. In vitro experiments were performed with DU-l45 and PC-3 human prostate cancer cells. Expression levels of SSTR2 were determined using 125 I-somatostatin in competitive inhibition assays on cell membrane preparations. Activity of CD was determined using an MTS assay to demonstrate sensitivity of the infected cells to 5-FC. In vivo experiments were conducted in athymic nude mice bearing subcutaneous DU-l45 or PC-3 cells (n 3-4). AdSSTR2CD was injected intratumorally followed 48 h later by an i.v. injection of 99mTc-P2045 (a radiolabeled somatostatin analogue kindly provided by Diatide Research Laboratories). The mice were imaged 5 h later with an Anger gamma camera equipped with a pinhole collimator and terminated for biodistribution analyses. The expression of SSTR2 on PC-3 cells was 209 fmol/mg of protein after AdSSTR2CD infection at 10 pfu/cell. DU-145 cells showed that SSTR2 expression was 4215 fmol/mg after infection at 10 pfu/cell. The 1C50 values of 5-FC were 682 micronM in PC-3 cells and 29 micronM in DU- 145 after infection with AdSSTR2CD at 10 pfu/cell. The PC-3 and DU-145 tumors injected with AdSSTR2CD could be visualized by imaging 99mTc-P2045 uptake. The PC-3 tumors averaged 1.1+1-0.4% dose/g, while the DU-145 tumors averaged 0.7+1-0.3 dose/g. Uninfected tumors demonstrated < 0.2 dose/g.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2002
- Accession Number
- ADA410511
Entities
People
- Buck E. Rogers
Organizations
- University of Alabama