The use of the L-plastin promoter for adenoviral-mediated, tumor-specific gene expression in ovarian and bladder cancer cell lines

A 2,4-kb truncated L-plastin promoter was inserted either 5 ' to the LacZ g ene (Ad-Lp-LacZ) or 5 ' to the cytosine deaminase (CD) gene (Ad-Lp-CD) in a replication-incompetent adenoviral vector backbone. Infectivity and cytoto xicity experiments with the LacZ and CD vectors suggested that the L-plasti n promoter-driven transcriptional units were expressed at much higher level s in explants of ovarian cancer cells from patients and in established ovar ian or bladder cancer cell lines than they mere in normal peritoneal mesoth elial cells from surgical specimens, in organ cultures of normal ovarian ce lls, or in the established CCD minimal deviation fibroblast cell line. Cont rol experiments showed that this difference was not attributable to the lac k of infectivity of the normal peritoneal cells, the normal ovarian cells, or the minimal deviation CCD fibroblast cell line, because these cells shel ved expression of the LacZ reporter gene when exposed to the replication-in competent adenoviral vector carrying the cytomegalovirus (CMV)-driven LacZ gene (Ad-CMV-LacZ). The Ovcar-5 and Skov-3 ovarian cancer cell lines expose d to the Ad-Lp-CD adenoviral vector were much more sensitive to the prodrug 5-fluorocytosine (5FEC), which is converted from the 5FC prodrug into the toxic chemical 5-fluorouracil, than was the CCD minimal deviation fibroblas t cell line after exposure to the same vector. A mouse xenograft model was used to show that the Ad-Lp-CD vector/5FC system could prevent engraftment of ovarian cancer cells in nude mice. Finally, injection of the Ad-Lp-CD ve ctor into s.c. tumor nodules generated a greater reduction of the size of t he tumor nodules than did injection of the Ad-CMV-LacZ vectors into tumor n odules, The Ad-Lp-CD vectors were as suppressive to tumor growth as the Ad- CMV-CD vectors. These results suggest that an adenoviral vector carrying th e CD gene controlled by the L-plastin promoter (Ad-Lp-CD) may be of potenti al value for the i.p. therapy of ovarian cancer.