Genetic mutations re-set brain cells to cause brain cancer

A study on the most common type of brain cancer in humans has found that expressing cancer genes, also known as
oncogenes, in fully developed brain cells can return them
to an immature state that results in the formation of tumours. The findings challenge the current thinking that brain cancer only arises from stem cells. 

'What we're saying is, any cell in the brain that gets an oncogenic insult has the ability to dedifferentiate and form tumors', Dr Inder Verma, the team leader and geneticist who led the research at the Salk Institute in La Jolla, California, told The Scientist.

Glioblastoma multiforme (GMB), the cancer under investigation, accounts for over half of all human cases of brain cancer and is the most aggressive type. Its prognosis is very poor, with an average survival time of 12-14 months from diagnosis.

In the study, researchers injected viruses containing two cancer-related genes into the brains of mice. They then monitored the progression of the resulting tumours, called gliomas. The team expected the tumours to arise predominantly from neural stem cells that had taken up the genes. However results showed that mature brain cells, including neurons, also took up the genes and progressed into gliomas.

Dr Martine Roussel, a molecular biologist at St Jude Children's Research Hospital in Memphis, said in Science News: 'To me it says something very scary. With just the right combination of hits you can become a glioma'.

Eight weeks after the injection, the neurons displayed increased stem cell-like properties and decreased neuronal characteristics, suggesting the cells had reverted to a more immature state as the tumours developed.

It is not yet clear if mature neurons in humans can also return to a more immature state and subsequently develop into brain tumours, though early findings from Dr Verma's team suggest this may be the case. Dr Verma told The Scientist, 'by knowing the mechanism, we at least have a handle to start thinking about treatments'.

The study was published in the journal Science.