Cancer vaccine uses immune system to attack tumour cells


THE US-BASED researchers who developed a vaccine against breast cancer have shown that it works against hidden, undetected tumours but can also attack established cancers.

The team in Cleveland, Ohio also believes that it could make significant improvements to its vaccine and then apply the technology to other cancers.

The highly significant findings were published on Monday in the journal, Nature Medicine. The vaccine is designed for use in mice and so would have to undergo significant long-term testing before being used in human trials.

Even so the researchers, led by Dr Vincent Tuohy in the Department of Immunology at the Lerner Research Institute, Cleveland Clinic, achieved a very high success rate in test mice. The vaccine provided protection against disease in mice that are genetically altered to develop cancers and also stopped tumour growth when given after a cancer was already established.

The treatment is so powerful because it uses the body's own immune system to attack the tumour cells. The vaccine is given to raise antibodies and these then attach to the tumour cells, calling in killer cells that attack the cancer. The success was based on finding a substance, alpha- lactalbumin, that is only released by breast cancer cells and by normal cells during lactation.

The researchers were able to use the alpha-lactalbumin to make a working vaccine and to raise antibodies against the tumours. The vaccine worked in two ways, first as a "prophylactic" that blocked the development of tumours in these cancer-prone mice and also as a "therapeutic" in attacking pre-existing tumours.

The researchers showed that if a mouse was producing breast milk to feed pups then breast tissue would become inflamed. No inflammation occurred if there was no lactation.

This meant that if developed for humans the vaccine should not be given to a woman who plans to breast-feed subsequent children.

"This unique conditional expression of [ alpha-lactalbumin] provides an opportunity for prophylactic breast cancer vaccination of normal healthy women who are either willing to avoid lactation or are past their child-bearing years and at an increased risk for breast cancer."

It may also be that the best is yet to come. The researchers point out that they had yet to develop "an optimised cancer vaccination strategy". There were many ways to improve on the initial vaccine by employing other known aspects of the body's immune system.

"In any event our data provide experimental support for developing safe and effective protection against breast tumours, and potentially tumours derived from other organs, by targeted vaccination against conditionally expressed, tissue specific . . . proteins."

A vaccine against cervical cancer is available but this works in a much different way. When given to young women it raises antibodies against a major cause of cervical cancer, the human papillomavirus. Blocking the virus greatly reduces the risk of developing cervical cancer, but it does not provide any therapeutic help if a cancer develops.