Viral oncolysis by herpes simplex virus and other viruses

The use of viruses to destroy tumors, also known as viral oncolysis, dates back to the early 1900's. Although the mechanism of cancer cell lysis was unknown in the early years of development, advances in tumor biology, molecular biology, and virology have been critical for numerous advances that have brought the field to where it is today. Oncolytic viruses have been developed based on innate and engineered properties to preferentially target tumor cells. Engineered properties include alterations in endogenous gene expression and introduction of foreign genes. Methods to non-invasively monitor sites of viral replication is required for preclinical and clinical studies. Positron emission tomography (PET) can be used for this purpose. This review focuses on commonly used oncolytic viruses, their selection for oncolytic therapy, the design of HSV-1 viral mutants, and monitoring their replication by PET.