Causes:

Genetics

Only 5 - 10% of primary brain tumors are associated with genetic disorders. These inherited conditions and associated genes include:

• Von Recklinghausen disease, also called neurofibromatosis 1 (NF1 gene) and neurofibromatosis 2 (NF2 gene)
• Turcot syndrome (APC gene)
• Gorlin syndrome, also called basal cell naevus syndrome (PTCH gene)
• Tuberous sclerosis (TSC1 and TSC2 genes)
• Li-Fraumeni syndrome (TP53 gene)

Certain types of brain tumors are specifically linked with these genetic conditions. For example, neurofibromatosis 1 is associated with about 15% of cases of pilocytic astrocytomas, the most common type of childhood glioma. Both of these result from defects in specific tumor suppressor genes.

Tumor suppressor genes regulate cell division and help repair DNA damage. When mutations that affect protein encoding occur, unregulated cell division and growth can lead to the development of a tumor. Tumor suppressor genes are sometimes described as being in a tug-of-war with cancer-causing genes called oncogenes.

Many different oncogenes are involved in cancer. Growth factors are a particularly important type of oncogene associated with brain tumors. Growth factors attach to receptors (connectors) that stimulate cell growth. Epidermal growth factor receptor (EGFR) has been shown to play a role in high-grade brain tumors such as glioblastoma multiforme. Knowing the molecular origin of a brain tumor may help determine the treatment course, both for standard chemotherapy and "targeted therapy" biologic drugs, such as gefitinib (Iressa) or erlotinib (Tarceva).

Most genetic abnormalities that cause brain tumors are not inherited but occur as a result of environmental or other factors that affect genetic materials (DNA) in the cells. Researchers are studying various environmental factors (such as viruses, hormones, chemicals, and radiation) that may trigger the genetic disruptions that lead to brain tumors in susceptible individuals. They are also working to identify the specific genes that are affected by these environmental triggers.