A need to teach tumor-killing viruses not to suppress the immune system

A number of novel potential antitumor therapeutics are currently being tested in laboratory studies. Tumor-killing oncolytic viruses, such as vesicular stomatitis virus (VSV), hold much promise. These viruses are an attractive potential therapy due to their ability to pass on their oncolytic activity, their specificity for tumor cells, and their capability to be eliminated in normal cells via induction of type I interferons.

While VSV has been shown to effectively kill tumor cells in tissue culture, this does not always translate in the body, where the virus seems less effective. Apparently, the virus creates a response that suppresses rather than elevates the immune system’s attack against the tumor.

In this month’s Molecular Therapy article, the authors delve into the mechanisms behind the immunosuppressive effects of VSV in a model of mesothelioma tumors (a rare cancer affecting the lining of the body’s organs). Initially hoping to enhance the anti-tumor effect of the cancer drug cyclophosphamide, they instead found a decrease in antitumor activity.

This study highlights the intricate roles exerted by multiple agents in combination therapies. Further study of the interplay between oncolytic virus therapy and other anti-tumor therapeutics will help researchers to understand these complex interactions – and maximize the effectiveness of cancer treaments.