demonstrated that radio-inducible suicide gene therapy, using a cytotoxic expression vector of herpes simplex virus thymidine kinase controlled by a radiation-inducible promoter, was significantly enhanced in its efficacy by addition of a recombinant adenovirus expressing human Flt3 ligand (Adeno-Flt3L) in a hepatoma mouse tumor model. The gene discussed is FLT3LG; the disease is hepatocellular carcinoma.