According to a recent publication in Cancer Research (65[7], 2832–2839 [2005]), viruses may one day help to treat malignant gliomas. A genetically modified herpes simplex virus that selectively infects, reproduces in and kills, malignant glioma cells was used to treat mice with implanted human gliomas. Results found that the virus significantly increased the survival of these mice, even, in some cases, in the presence of advanced disease. The treatment left normal tissue unharmed.
The strain of herpes simplex virus used by the researchers lacked several genes present in the wild-type virus. In initial research, although the altered virus infected malignant cells only, its ability to kill these cells was weak due to impaired replication. One of the removed genes was therefore reinserted into the viral genome after being modified so that it would be active solely in cells that produced the protein nestin. This protein is usually only produced in cells during embryonic development and is otherwise absent, the exception being in malignant glioma, and some other cancers, allowing the targeted killing of cancer cells.
Although this preliminary study is a step towards the use of safe an effective oncolytic viruses in the treatment of human cancer, the progression from animal to human studies seems distant. The authors highlight that the survival time of malignant glioma patients, which stands at approximately 1 year after diagnosis, has failed to improve in over 30 years. New therapies to replace or assist the current options of surgery, chemotherapy and radiation are therefore required in the treatment of this -predominantly fatal and rapidly progressing disease.