Scientists trace a gene that triggers cancer

Scientists shed new light yesterday on why a single gene can trigger breast cancer in 80 per cent of women who carry it.

In healthy women, the BRCA-1 gene, found on chromosome 17, helps the body to detect potentially cancerous cells and forces them to self- destruct. But researchers at Queen's University, Belfast say that when the gene is faulty, the "radar" system is blinded and tumours develop. Women who inherit a mutation in the BRCA-1 gene are known to have a 65 to 85 per cent chance of developing breast cancer.

They also have a 40 per cent chance of ovarian cancer by the age of 70. But the role the gene plays in this elevated risk is not fully understood. Dr Paul Harkin and colleagues at Queen's used the latest technology to study thousands of cells containing normal BRCA-1 genes and cells with defective genes.

In normal circumstances, the gene interacts with a chemical called interferon gamma, the "eyes and ears" of the immune system, and scours the body for diseased cells, which are killed off.

When the BRCA-1 gene is dysfunctional, the surveillance system appears to break down. But by adding a healthy copy of the BRCA-1 gene, the researchers were able to restore the surveillance system.

Sir Paul Nurse, chief executive of Cancer Research UK, which supported the work, said: "We need to understand why one faulty gene can make such a big difference. Dr Harkin and his team are bringing us closer to this aim."