Oncolytic herpes simplex virus therapy for peripheral nerve tumors

Oncolytic viruses are one of many emerging cancer therapies. The surgical management of peripheral nerve tumors carries an inherent risk of damaging the nerves involved and so the search for novel therapies with reduced risk of morbidity continues. In this review the authors discuss the use of oncolytic herpes simplex virus (HSV) in the treatment of peripheral nerve tumors. Herpes simplex virus has a number of characteristics that make it a useful oncolytic vector, including its large, sequenced genome that can accommodate multiple transgenes, its lack of insertional mutagenesis, its ability to infect a wide array of cell types in various species, and the availability of well-established antiviral therapies to treat it. The efficacy of oncolytic HSV therapy against schwannomas and malignant peripheral nerve sheath tumors has been studied in multiple experimental models both in vitro and in vivo. The virus utilizes cell pathways unique to tumors to enhance its oncolytic efficacy, preferentially and effectively targeting and destroying peripheral nerve tumor cells without harming normal cells. This effect is augmented by transgenes expressing antiangiogenic factors, such as dominant-negative fibroblast growth factor receptor and platelet factor 4, and displays synergy with chemotherapy. Different oncolytic HSV vectors have been tested, including hrR3, G207, and G47D. In addition, new animal models have been developed to test the efficacy of oncolytic HSV therapy in peripheral nerve tumors. The safety of oncolytic HSV is well established and has been tested in nonhuman primates and in human clinical trials.