The use of a purine nucleoside phosphorylase or nucleoside hydrolase or a vector encoding expression of one of these enzymes is detailed along with the use of a prodrug cleaved by the purine nucleoside phosphorylase or nucleoside hydrolase for the preparation of a direct injection inhibition of replicating or non-replicating targeted cells. The targeted cells do not normally express the introduced purine nucleoside phosphorylase or nucleoside hydrolase. The enzyme and prodrug are amenable to intermixing and injection as a single dose or as separate injection or administration to the targeted cells. The substance and prodrug efficacy are enhanced through exposure of the targeted cells to X-ray radiation. Administration of a prodrug regardless of administration route to the targeted cells is effective in combination with X-ray radiation therapy to kill or inhibit function of the targeted cells.
