Scientists believe they may have identified the mechanism that shows a link between head injuries and the risk of a rare and aggressive form of brain tumour.
Researchers from the University College London’s (UCL) Cancer Institute said their work, published in the journal Current Biology provides an “important molecular understanding” of how brain traumas may contribute to the development of glioma.
Glioma is a growth of cells that starts in the brain or spinal cord.
As it grows, a glioma forms a mass of cells known as tumour.
More mature types of brain cells – known as astrocytes – have been deemed as less likely to give rise to tumours.
However, recent findings have demonstrated that a brain injury can cause astrocytes to behave like stem cells – the body’s raw materials – again.
As part of the study, Professor Simona Parrinello and her colleagues investigated whether a head injury can cause astrocytes to form a tumour.
They injected young adult mice with a substance that targeted astrocytes and disabled the function of a gene known as p53 – which is thought to play a key role in suppressing many different cancers.
Another group of mice also had the p53 gene inactivated but these rodents did not have brain trauma.
The p53 gene was left intact in the third control group.
Professor Parrinello said: “Normally astrocytes are highly branched – they take their name from stars – but what we found was that without p53 and only after an injury, the astrocytes had retracted their branches and become more rounded.
“They weren’t quite stem cell-like, but something had changed.
“So we let the mice age, then looked at the cells again and saw that they had completely reverted to a stem-like state with markers of early glioma cells that could divide.”
According to Professor Parrinello, this suggests inflammation as a result of severe brain injury can result in mutations in certain genes.
Researchers said that, over time, these changes can make astrocytes more likely to initiate a cancer.
The scientists then looked at the medical records of over 20,000 people diagnosed with head injuries, comparing the rate of brain cancer with a control group.
They found patients who experienced a head injury were up to four times more likely to develop a brain cancer later in life, than those without head trauma.
However, the researchers said it is important to note that the risk of developing a brain cancer is overall low so, even after an injury, the risk remains modest.
Professor Parrinello said: “We know that normal tissues carry many mutations which seem to just sit there and not have any major effects.
“Our findings suggest that if on top of those mutations, an injury occurs, it creates a synergistic effect.
“In a young brain, basal inflammation is low so the mutations seem to be kept in check even after a serious brain injury.
“However, upon ageing, our mouse work suggests that inflammation increases throughout the brain but more intensely at the site of the earlier injury.
“This may reach a certain threshold after which the mutation now begins to manifest itself.”