Stress can give you cancer, scientists prove

Published on Wednesday 13 January 2010 21:36

A DIRECT connection between stress and cancer has been confirmed by scientists for the first time.

Researchers found stressed cells can generate tumour-inducing signals that affect their neighbours.

Although the study was carried out on fruit flies, the same genes and biological pathways involved are found in humans.

Chronic inflammation, a key cause of stress, is already known to be associated with tumour growth in human cancer patients. Some experts believe negative emotions, stress hormones, inflammation and cancer may all be linked, but the evidence is not clear.

Until now, it was widely believed that cancer-causing genetic mutations affected only individual cells.

The new research shows this is not always the case. Different cancer mutations in separate cells can co-operate to promote the development of tumours.

Scientists in the US and China focused on the activity of two mutant genes known to be involved in human cancers. One of these, called RAS, has been implicated in 30 per cent of cancers. The other, a tumour-suppressing gene called "scribble", allows cancers to develop when it becomes defective.

However, neither a mutated RAS gene nor a mutant version of scribble can cause cancer on its own. The researchers studied fruit flies carrying both gene mutations. They found that a cell with only mutant RAS can develop into a malignant tumour if assisted by a nearby cell with defective scribble.

Stress was the factor that linked them together, causing signalling proteins called cytokines to travel between the cells.

The process of stress signalling, which is known as JNK, can be activated by a range of environmental influences.

Study leader Professor Tian Xu, from Yale University School of Medicine in the United States, said: "A lot of different conditions can trigger stress signalling: physical stress, emotional stress, infections, inflammation – all these things. Bad news for cancer."

The research is reported in the journal Nature.

In their paper, the scientists pointed out that the same signalling pathways identified in fruit flies exist in humans.

They wrote: "Given the conservation of the pathways examined here, similar co-operative mechanisms could have a role in the development of human cancers."

The research shows it is easier than previously thought for cancer to take root in the body, since mutations are more likely to accumulate in different cells than in the same cells.

But it also identifies a potential new way to stop cancer, by blocking JNK stress signalling.