Intratumoral Activation and Enhanced Chemotherapeutic Effect of Oxazaphosphorines following Cytochrome P-450 Gene Transfer: Development of a Combined Chemotherapy/Cancer Gene Therapy Strategy

摘要: Abstract Cyclophosphamide and its isomer ifosfamide are cell cycle-nonspecific alkylating agents that undergo bioactivation catalyzed by liver cytochrome P-450 enzymes. The therapeutic efficacy of these oxazaphosphorine anticancer drugs is limited host toxicity resulting from the systemic distribution activated drug metabolites formed in liver. Since tumor cells ordinarily do not have capacity to activate oxazaphosphorines, we examined whether introduction into a cDNA encoding CYP2B1, major catalyst activation, sensitizes cytotoxic effects cyclophosphamide ifosfamide. Here show 9L gliosarcoma stably transfected with rat CYP2B1 highly sensitive cytotoxicity as compared parental or an Escherichia coli β-galactosidase gene. enzyme inhibitor metyrapone protects CYP2B1-expressing cytotoxicity, demonstrating chemosensitivity direct consequence intracellular prodrug activation. Moreover, potentiate toward cocultured CYP2B1-negative cells. This “bystander effect” does require cell-cell contact, therefore may advantage distributing wide area within solid mass. In vivo experiments using Fischer 344 rats implanted s.c. demonstrated intratumoral expression gene provides substantial over provided P-450-dependent activation alone; treatment resulted complete growth inhibition CYP2B1-positive tumors, whereas only modest delay effect was obtained tumors. These studies establish drug-activating CYP genes be useful for development novel combined chemotherapy/gene therapy strategies cancer utilizing established chemotherapeutic agents.