Strategies to accomplish targeted expression of transgenes in ovarian cancer for molecular therapeutic applications

Purpose: The purpose of the study was to determine the capability of the mi dkine (MK) and cycooxygenase-2 (cox-2) gene promoter regions to function as tumor-specific promoters for use in targeted gene therapy of ovarian cance r. Experimental Design: Established and primary ovarian cancer and mesothelial cells were transduced by adenoviral vectors containing a reporter or thymi dine kinase gene expressed under the control of the MK, cox-2, or cytomegal ovirus (CMV) promoters. SCID or C57BL/6 mice were injected i.p. with these same vectors. In vitro reporter gene expression and cellular cytotoxicity w as determined using luciferase and 3-(4,5-dimethylthiazol-2-yl)-2,5-dipheny ltetrazolium bromide (MTT) assays, respectively. Acute toxicity in vivo was assessed by histological evaluation of harvested tissues. Results: Consistent activation of the MK and cox-2 promoters was noted in a ll of the ovarian cancer cell lines in addition to primary ovarian cancer c ells. In contrast, reduced reporter activity was reported in mesothelial ce lls transduced with adenoviruses containing the test promoters, which was e specially apparent for the cox-2 promoter. Additionally, the cox-2 promoter exhibited significantly lower reporter gene levels in liver and peritoneum than the control promoter in in vivo experiments. Tumor-cell killing induc ed by Adcox-2 MTK was comparable to that observed with AdCMVTK. However, a clear differential toxicity pattern was observed in favor of animals treate d with Adcox-2 MTK when compared with controls. Conclusions: These data clearly demonstrate that the transcriptional contro l afforded by the cox-2 promoter is tumor-specific and is able to mitigate associated toxicity in normal tissue while maintaining therapeutic efficacy in the context of an ovarian cancer molecular chemotherapeutic approach.