Researchers believe lithium can boost the fitness of healthy stem cells in the gut, making them more resistant to sabotage from mutant cells that cause the cancer.
Their findings have led to the launch of a new clinical trial to test if lithium – a commonly used drug for the treatment of several psychiatric disorders – could be used to prevent the development of bowel cancer.
The study, funded by the Dutch Cancer Society (KWF), will recruit patients with a genetic mutation known as familial adenomatous polyposis (FAP).
FAP is a relatively uncommon genetic syndrome that affects about one in 7,000 to one in 22,000 people, in which individuals are almost certain to develop bowel cancer unless their entire large bowel is removed.
The majority of bowel cancer cases are thought to be caused by mutations in a gene called APC.
Intestinal stem cells with mutations to the APC gene have been shown to have a competitive advantage over their healthy counterparts and frequently outcompete them.
This leads to unrestricted growth and cancer, researchers say.
Patients who have FAP have mutations in their APC gene and develop hundreds of non-cancerous polyps and adenomas in their bowel.
Professor Louis Vermeulen, senior author of the paper published in Nature, said: "We have uncovered the very first steps in the development of bowel cancer.
"We found that, following the occurrence of a mutation in a key gene that regulates stem cells in the intestine, these cells turn into cheaters that actively suppress the normal cells in the environment.
"This is a totally new concept as it was always thought that mutant cells that can turn into cancer simply proliferate faster or are resistant to cell death.
"But our findings indicate that cells on their way to a full malignancy can actively suppress the stem cells in the vicinity to gain a competitive edge. This is a concept we refer to as super-competition."
Dr Helen Rippon, chief executive at Worldwide Cancer Research, said: "The discoveries made by Professor Vermeulen and his team are a huge breakthrough in our understanding of how bowel cancer develops.
"We are all very excited to see the results from this clinical trial and the future impact these findings might have on other people with inherited cancer syndromes."
Bowel cancer is the fourth most common cancer in the UK, with more than 43,000 people diagnosed with the condition in the UK every year.
The NHS estimates that around one in 20 people will get bowel cancer during their lifetime.
Symptoms of the condition include a persistent change in bowel habit, abdominal pain, and blood in the stool.
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