- Expression of Escherichia coli B nitroreductase in established human tumor xenografts in mice results in potent antitumoral and bystander effects upon systemic administration of the prodrug CB1954. Djeha, A.H., Hulme, A., Dexter, M.T., Mountain, A., Young, L.S., Searle, P.F., Kerr, D.J., Wrighton, C.J. Cancer Gene Ther. (2000)