Abstract: Methods of killing neoplastic cells are provided. The invention relates to the use of NADPH-cytochrome P450 reductase (RED) gene transfer in combination with cytochrome P450 gene transfer to enhance the sensitivity of tumor cells to anti-cancer drugs that are activated by P450 enzymes. The use of bioreductive drugs that are activated by RED and/or cytochrome P450, in this paradigm, is also provided.