THE EXPRESSION OF BACTERIAL NITROREDUCTASE IN TRANSGENIC MICE RESULTSIN SPECIFIC CELL-KILLING BY THE PRODRUG CB1954

The enzyme nitroreductase, isolated from Escherichia coli B, converts CB1954 ((5-aziridin-1-yl)-2,4-dinitro-benz-amide) into a cytotoxic DNA interstrand cross-linking agent. The E. coli B gene (nfnB, NTR) encod ing nitroreductase (NTR) was cloned into eukaryotic expression vectors . When driven by a CMV promoter, 5-10% of the stably transfected mouse fibroblasts expressed the NTR enzyme. These cells were killed at a co ncentration of 20 mu M CB1954 comparison to nonexpressing cells which were killed at a much higher concentration (500 mu M). We subsequently a generated transgenic mice to test the prodrug system in vivo. Nitro reductase was expressed specifically in T cells driven by the control elements of the human CD2 locus, Upon CB1954 treatment, transgenic mic e show extensive cell depletion in thymus and spleen (14-16% of normal cell numbers), whereas all other tissues are unaffected by prodrug ad ministration. These results raise the possibility of using the NTR gen e in anticancer therapy.