These findings should prove to be a key weapon in treating this form of leukaemia

Dr David Grant

More than 2,500 new cases of the disease are recorded each year in Britain.

It has been known for many years that a gene called p53 plays an important role in the majority of human cancers including CLL.

The gene helps to protect the body from cancer by keeping its genetic material healthy.

It ensures that cells that have damaged or altered genes are destroyed if they cannot be repaired.

Damage to this gene is therefore implicated in a number of cancers.

Second gene

The LRF scientists have now found for the first time that damage to another gene - dubbed ATM - can have a knock-on effect on the p53 gene.

A healthy ATM gene plays a key role in helping the body to detect unwanted damage to DNA.

this mutant gene can deactivate the 'cell destruct' button

Dr Tanya Stankovic

But a defective ATM gene can interfere with p53 thereby allowing potentially cancerous cells to multiply.

Dr Tanya Stankovic, from the University of Birmingham, said: "It is almost as if this mutant gene can deactivate the 'cell destruct' button, allowing the rogue cells to multiply.

"It is well known that p53's protein helps protect us from cancer but this is the first time that scientists have shown that another gene can have a knock on effect on p53 function in tumour cells."

The researchers found that around 20% of CLL tumours had a faulty ATM gene, and another 10-15% had an abnormality in the p53 gene.

Scientists believe that patients with this mutant ATM gene may have a more aggressive form of CLL which is more difficult to treat with conventional drugs.

Dr David Grant, Scientific Director of the Leukaemia Research Fund, said: "These findings should prove to be a key weapon in treating this form of leukaemia.

"It is vital that we pick out patients with a poor prognosis at an early stage so we can give them more aggressive therapy when they are fitter and in a better position to tolerate it."

Characteristics

CLL mainly affects older people.

It is characterised by a build up of poorly functioning immune cells called lymphocytes in the blood. This is mainly because these cells fail to die at the end of their normal lifespan.

The most common symptoms are weakness, fatigue, night sweats and repeated infections.

Some patients may require no treatment in the early stages of CLL. Removal of the spleen may be required if it has become enlarged and is causing distress.

Younger patients with CLL may be considered for a transplant of immature stem cells from their own bone marrow.