Multidisciplinary Cancer Therapy with Telomerase-Specific Oncolytic Adenovirus

A multidisciplinary approach of combining surgery, chemotherapy and radiotherapy has remained the accepted standard management for various types of human cancer. However, many new treatment options have recently become available, including molecular targeted therapies, immunotherapies and oncolytic virotherapies. Replication-selective tumor-specific viruses have been designed to induce virus-mediated lysis of tumor cells after selective viral propagation within the tumor. We constructed an attenuated adenovirus 5 vector, telomelysin (OBP-301), in which the telomerase-specific promoter drives expression of viral replication-inducible E1 genes. Although telomelysin alone exhibited substantial antitumor effects both in animal models and in clinical trials, telomelysin has the potential to be the first-in-class oncolytic virus for combination therapy based on our current understanding of the molecular mechanisms. Telomelysin sensitizes human cancer cells to ionizing radiation by inhibiting the radiation-induced DNA repair machinery, and also eliminates radio-resistant quiescent cancer stem-like cells by promoting cell cycle entry. A clinical trial of intratumoral administration of telomelysin with radiotherapy in esophageal cancer patients is currently underway. This article reviews recent highlights in the rapidly evolving field of multidisciplinary therapy with telomelysin.