Restricted replication-competent adenovirus: A novel strategy for cancer gene therapy

Mutant adenoviruses that are selectively replication- competent in tumor cells have been developed as a novel strategy for gene therapy of cancer. Such selectively replicating viruses may overcome the limitations of the gene transfer of adenoviral vectors. The replication of such viruses in a small fraction of the tumor cells leads to amplification and extension of the antitumor effect, with cell killing being caused exclusively by viral replication and cell lysis. Replication-competent adenoviruses have several theoretical advantages over replication-defective adenoviruses for cancer gene therapy. It has been demonstrated that replication-competent adenoviruses are not only a strong weapon themselves but that they are also useful carriers of genes for anti-tumor factors, acting as virus vectors specific to tumors without normal p53 function or an intact retinoblastoma gene (RB) pathway. Clinical trials will clarify these advantages in future.