The most aggressive kind of brain tumor, glioblastoma multiforme involves the glial cells of the brain. Regarded as the glue that holds the nervous system together, the glial cells provide oxygen and nutrients to nerve cells, and help to maintain the barrier separating cerebrospinal fluid from circulating blood. These glial cells stop dividing soon after birth, but genetic malfunctions cause the cells to resume multiplying, causing glioblastomas. The cause of these genetic alterations is still unclear, but research shows that glioblastomas may be more likely to develop in people with certain risk factors.

Ionizing Radiation

Of all the factors that have been studied as possible causes of glioblastoma, only ionizing radiation exposure has repeatedly been linked to the tumor. This type of exposure comes as a result of radiation therapy to the head or neck for some other type of tumor, such as thyroid or laryngeal cancer. These high-powered X-rays damage cell DNA, which is desired when treating the original cancer, but can lead to irregular cell division and trigger the formation of a tumor.

Family History and Genetic Factors

Although heredity seems to a play a role in the genetic malfunctions that cause glioblastomas, brain tumors are very rarely diagnosed in more than one family member. In very isolated cases, a mutation in a single gene is passed from a grandparent to a parent and then to a child. Adults may be at greater risk for glioblastoma or other glial tumors if they have certain other rare genetic disorders, including neurofibromatosis, Turcot syndrome or Li-Fraumeni syndrome. Most genetic risk factors are not inherited at birth but rather emerge over time as individual genes with highly specialized responsibilities begin to malfunction. Researchers at the M.D. Anderson Cancer Center report that the gene responsible for regulating cell growth behaves abnormally in more than half of patients with glioblastoma. [ref 4] Known as the EGFR gene because it produces a protein called epidermal growth factor, this gene helps to govern normal cell division and survival. When the EGFR gene malfunctions, cells multiply too quickly---which is why glioblastoma tumors grow exceptionally fast.