IN-VIVO GENE-THERAPY OF CANCER WITH ESCHERICHIA-COLI PURINE NUCLEOSIDE PHOSPHORYLASE

We have developed a new strategy for the gene therapy of cancer based on the activation of purine nucleoside analogs by transduced E. coli p urine nucleoside phosphorylase (PNP, E.C. 2.4.2.1), The approach is de signed to generate antimetabolites intracellularly that would be too t oxic for systemic administration, To determine whether this strategy c ould be used to kill tumor cells without host toxicity, nude mice bear ing human malignant D54MG glioma tumors expressing E. coli PNP (D54-PN P) were treated with either 6-methylpurine-2'-deoxyriboside (MeP-dR) o r arabinofuranosyl-2-fluoroadenine monophosphate (F-araAMP, fludarabin e, a precursor of F-araA), Both prodrugs exhibited significant antitum or activity against established D54-PNP tumors at doses that produced no discernible systemic toxicity, Significantly, MeP-dR was curative a gainst this slow growing solid tumor after only 3 doses, The antitumor effects showed a dose dependence on both the amount of prodrug given and the level of E. coli PNP expression within tumor xenografts, These results indicated that a strategy using E. coli PNP to create highly toxic, membrane permeant compounds that kill both replicating and nonr eplicating cells is feasible in vivo, further supporting development o f this cancer gene therapy approach.