Use of L-plastin promoter to develop an adenoviral system that confers transgene expression in ovarian cancer cells but not in normal mesothelial cells

The objective of this study was to develop an adenoviral Vector system that would generate a pattern of expression of exogenous therapeutic genes appr opriate for the treatment of ovarian cancer. For this purpose, we have gene rated a replication-deficient recombinant adenoviral vector, AdLPLacZ, whic h contains the human L-plastin (LP) promoter (LP-P) driving the Escherichia coli LacZ gene. LP is constitutively expressed at high levels in malignant epithelial cells but is not expressed in normal tissues, except at low lev els in mature hematopoietic cells. Because adenoviral vectors infect early hematopoietic multilineage precursor cells only poorly or not at all, this vector would be of use in the peritoneal cavity and in vitro for marrow pur ging. We first analyzed the expression of the LacZ reporter gene in ovarian and breast cancer cell lines, normal fibroblasts, and leukemia cell lines using the adenoviral vector in which the LacZ gene is governed by the LP-P promoter (AdLPLacZ) or in which the LacZ gene is governed by the cytomegalo virus (CMV) promoter (AdCMVLacZ). We found equivalent and high levels of ex pression of beta-galactosidase (beta-gal) by AdLPLacZ and AdCMVLacZ vectors in the breast or ovarian cancer cell lines as well as in a fibrosarcoma ce ll line, indicating that the adenoviral vectors infected these cells and ex pressed their transgenes equally with the LP and CMV promoters. Expression of the LacZgene with the CMV vector but not with the LP-P vector was observ ed in experiments with normal fibroblasts, indicating that the vectors infe cted the cells, but that the LP-P was not active within them. In hematopoie tic cells such as U937 cells, no measurable beta-gal activity was detected in cells infected either by AdLPLacZ or by AdCMVLacZ, indicating that the a denoviral vectors were not infecting the cells. Although beta-gal activity was observed in fresh ascitic ovarian cancer cells after infection with ade noviral vectors containing CMV or the LP promoters, beta-gal activity was d etected in a portion of a biopsy of normal peritoneum when the tissues were exposed to the AdCMVLacZ vector, but not when tissues were exposed to the AdLPLacZ vector. These results suggest that the transcription of therapeuti c genes in cells infected by the AdLP vectors would be restricted to LP exp ression-positive ovarian carcinoma cells but would not be seen in the norma l mesothelial cells of the peritoneal cavity. This possibility implies that adenoviral vectors carrying therapeutic genes driven by the LP-P would be of use for the intracavitary treatment ovarian cancer.