Gene therapy approaches for solid tumors: Ovarian carcinoma and bioreductive chemotherapy

Ovarian carcinoma remains a leading cause of death due to gynecological malignancies. A new therapeutic approach currently under development for the treatment of solid tumors is gene therapy. Transgenes may be limited in expression to a particular subset of cells by placing them under the control of regulatory elements that are induced following cellular exposure to stress. Tumor cells experience stresses from such agents as hypoxia, radiotherapy, and chemotherapy.; Virally directed enzyme prodrug therapy is one strategy designed to employ a viral vector to deliver an enzyme that transforms a prodrug into a more toxic compound. The enzymology of bioreductive chemotherapy bioactivation may have the potential to be exploited in this strategy. The knowledge of the role of a particular reductase in the bioactivation of a drug allows for the design of treatment strategies aimed at targeting the cytotoxic actions of that compound.; The objectives of this work were: (1) to examine the ability to control transgene expression with the transcriptional response to cellular stress; and (2) to develop a virally directed enzyme prodrug approach based on the relationship between bioreductive chemotherapy agents and their bioactivation by cellular reductases.; Modest increases in gene expression were observed in the ovarian tumor cells only at clinically irrelevant doses following transfection of adenovirus and adeno-associated virus proviral plasmids containing the stress responsive promoters of genes induced by hypoxia, radiotherapy, and chemotherapy. The relationship between oxygenation status, NQO1 and CYPOR expression, and the cytotoxicity of MMC, EO9, and tirapazamine was examined in ovarian tumor cells to determine enzyme/drug relationships that may be exploited in an enzyme-directed manner.; A strong enzyme/drug correlation was revealed for NQO1/EO9. An enhanced cytotoxic response to EO9 was observed in those tumor cell lines that had elevated NQO1 levels. To test the ability to improve the cytotoxicity of EO9 in ovarian tumor cells that are inherently low in NQO1 expression, we delivered and overexpressed NQO1 using recombinant gene delivery systems prior to bioreductive drug administration. These cells exhibited increased sensitivity to EO9 following gene delivery. These experiments set the stage for examining the ability of improving the in vivo response of low NQO1 expressing human ovarian tumor xenografts to EO9 using recombinant gene delivery systems.