Researchers investigating a severe type of brain cancer - glioblastoma multiforme - have identified eight genes that predict how long a patient will survive following diagnosis. The genes, which are linked to the immune system, could help clinicians determine the best course of treatment in the future.
Gliomas are a type of tumor that starts in the glial cells of the central nervous system (brain and spinal cord). Glia are the support cells of the nervous system, providing physical support and insulation to neurons.
Glioblastoma multiforme, also known as grade 4 astrocytoma, is the most common and aggressive form of glioma.
Glioblastoma multiforme does not respond well to current treatments. There are a number of reasons for this resistance to interventions, these include the difficulty of getting drugs to the tumor site due to disrupted blood supply and a build up of fluid in the area.
The tumors associated with glioblastoma multiforme grow particularly quickly and migrate easily into neighboring sections of brain tissue.
Because of the tumor's position in the brain, even when surgery is performed, it is virtually impossible to remove all of the cancerous tissue, making relapse inevitable. This cancer type accounts for more than half of all brain tumors and affects an estimated 2-3 people per 100,000.
Immunity, genes, and gliomas
A team of scientists from the First Hospital of China Medical University in Shenyang, China, recently embarked on research investigating the role of genetics and immunity on the survival rates of this pernicious cancer variant.
In other cancers, drugs have been designed that improve the immune system's ability to attack the cancer. The treatments effectively "take the brakes off" the immune system. However, to date, this has not been possible in gliomas.
In the current study, the researchers, headed up by Dr. Anhua Wu, looked at tissue samples from 297 people with brain tumors. Of these, 127 people had glioblastoma and the others had less aggressive forms of glioma.
In all, the team analyzed 322 genes involved in the immune system. After extensive screening, eight specific genes were identified as playing a significant role in glioblastoma multiforme.
Gene signature and survival rates
Three of the eight genes were shown to have a protective role, while the other five increased the risk of earlier death. The researchers were able to construct a genetic signature that predicted the survival times of the patients and divide them into low- and high-risk groups.
Even after controlling for factors such as treatment type, those in the high-risk genetic group were twice as likely to have a shorter survival time than those in the low-risk group.
The high-risk group survived an average of 348 days after diagnosis, the low-risk group survived an average of 493 days. Those in the high-risk group were also likely to have a shorter time between diagnosis and the first signs that the tumor was becoming worse - 242 days compared with 369 for the lower-risk group.
These genes were also found to predict survival rates of the patients with other forms of glioma.
To add further weight to the findings, the researchers dipped into a database of 536 glioblastoma samples. Within these samples, they were able to identify the same eight-gene signature at work.
The research is accompanied by an editorial, written by Dr. Rifaat Bashir, a retired neurologist in Reston, VA and a fellow of the American Academy of Neurology and the American Neurological Association.
"The looming question in brain cancer research today is whether the launch of immunotherapy will help control an uncontrollable disease. While this study does not answer this question, it brings us one step closer to believing that one day we will be able to exploit the immune system to better treat glioblastoma."
Dr. Rifaat Bashir
Dr. Wu believes that the findings might help improve the treatment of glioblastoma. He hopes that, in the future, it will be possible to "use this gene signature to determine the best treatments or path of treatment."