Clinical trials of a vaccine designed to protect healthy women against breast cancer could begin within the next two years.
The jab is still under development, but its effectiveness has impressed doctors who tested it on animals prone to the disease. If the vaccine works on humans, researchers say doctors could offer it to women before they reach their mid-40s, when the risk of developing breast cancer starts to rise steeply.
‘We think it will provide substantial protection,” said Vincent Tuohy, an immunologist at the Cleveland Clinic in Ohio. ‘Our view is that breast cancer is a completely preventable disease.”
Effective cancer vaccines have proved notoriously difficult to make, not least because tumour cells are strikingly similar to healthy ones. A poorly designed cancer vaccine could easily turn the immune system against other parts of the body and cause more harm than good, and another problem is that many cancers weaken the immune system as they grow.
Tuohy’s vaccine makes the immune system attack a particular protein found in most breast cancer cells and the mammary tissues of breastfeeding women. As such, it would be given only to women who are not going to breastfeed in the future.
‘The frequency of women who breastfeed in their early 40s and above is very low, so we are looking at vaccinating women against the disease from this stage of life onwards,” Tuohy said.
Details of the vaccine are reported in the Nature Medicine journal. Breast cancer is the most common form of cancer in Britain. In 2007 nearly 45 700 women and 277 men were diagnosed with the condition. Among women breast cancer rates have risen by 50% in the past 25 years. About 80% of cases are diagnosed in women aged 50 and over.
Although the disease kills about 12 000 British women each year, national screening programmes and other public health measures have helped cut death rates by nearly one-third from their peak in the late 1980s.
The causes of breast cancer are not fully understood, but hormonal changes, genetic factors, a family history of the condition, smoking and drinking alcohol are all known to affect the risk of developing the disease.
Obesity and hormone replacement therapy (HRT) increase a woman’s chances of developing breast cancer, whereas bearing children reduces the risk.
Tuohy’s team tested the vaccine on mice bred to be prone to breast cancer. Usually such mice develop large breast tumours within 10 months of being born.
The researchers injected six mice with a vaccine made from the target protein, alpha-lactalbumin, and a chemical called an adjuvant, which boosts the immune system response to the vaccine. Six other mice were given a sham vaccine.
All the mice were two months old and clear of cancer when they had their jabs. After 10 months all mice that received the sham vaccine had developed serious breast tumours. None of the mice given the real vaccine showed any signs of tumours in its breast tissue.
Previous studies show half to 70% of human breast cancer cells carry the alpha-lactalbumin protein the vaccine targets; figures that suggest the jab would not destroy all a patient’s breast cancer cells. But the Cleveland Clinic group suspect far more cancer cells produce the protein temporarily as they grow.
If they are right, the vaccine could be more effective than expected. Researchers hope to
begin human trials within two years, Tuohy said. —