Childhood leukaemia may be attributed to exposure to common infections, claim scientists.
The researchers claimed to have identified a molecule called TGF, produced by the body in response to infection, which appears to trigger multiplication of pre-cancerous stem cells at the expense of its healthy counterparts.
Researchers had previously identified a genetic mutation linked to stimulation of pre-leukaemic cells. It is believed to occur in 1 in 100 newborns and one in 100 of these children develop leukaemia.
This suggests that the cells will only complete the transformation to fully-fledged cancer cells if they exposed to an independent trigger.
The research team believes that TGF production in response to an infection could be that trigger.
"Identifying this step means we can determine how an unusual immune response to infection may trigger the development of the full leukaemia and eventually perhaps develop preventative measures such as a vaccine," The BBC quoted researcher Professor Mel Greaves as saying.
"Before this study, there had been only circumstantial evidence to implicate infections in the progression from a child carrying pre-leukaemic cells to actually having leukaemia," said Dr Shabih Syed, scientific director at the charity Leukaemia Research.
There was no evidence of the mechanism by which this might happen.
"While infection is clearly only one factor in triggering progression, this study greatly increases the strength of evidence for its role in the commonest form of childhood leukaemia," Syed added.
The study appears in the Journal of Clinical Investigation.