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 human patients, 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 tumor cells are strikingly similar to healthy tissues.
A poorly designed cancer vaccine could easily turn the immune system against other parts of the body and cause more harm than good, while 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 only be given 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 onward,” Tuohy said.
Details of the vaccine were reported in the Nature Medicine journal.
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 increase a woman’s chances of developing breast cancer, while 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 tumors 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 the mice that received the sham vaccine had developed serious breast tumors. None of the mice given the real vaccine showed any signs of tumors in their breast tissue.
“Over the duration of the study, it was completely effective,” Tuohy said.
The vaccine was far less effective when administered to mice that already had breast cancer.
Previous studies show half to 70 percent of human breast cancer cells carry the alpha-lactalbumin protein the vaccine targets — figures that suggest the jab would not destroy all of 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.
“This research could have important implications for how we might prevent breast cancer in the future,” said Caitlin Palframan, policy manager at Breakthrough Breast Cancer.
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