Sunday, September 21, 2008

Can a vaccine help fight breast cancer?

A new vaccine in development targets breast cancers that proliferate aggressively in response to the growth factor HER-2. About 25-30% of women with breast cancer have HER-2 positive tumours. Herceptin (trastuzumab), a man-made antibody approved for the treatment of breast cancer, targets these cancers. However, tumour cells often become resistant to Herceptin over time. The experimental breast cancer vaccine makes mice reject tumours, even in cancers that are no longer sensitive to Herceptin.

The researchers published in the findings in Cancer Research and found that the vaccine elicits immune responses that kill HER-2 positive breast tumours in mice, irrespective of whether they become Herceptin resistant. If immune cells are properly primed by immunisation, then the cells can be destroyed.

The vaccine, developed at the Karmanos Cancer Center in Detroit, used DNA that carries the genetic code for a key piece of the HER-2 molecule. After injection of the DNA into the skin, a small electric pulse is administered to help cells take up the DNA and produce the protein that elicits immune responses.

Mice given the vaccine made anti-HER-2 antibodies. The vaccine also primed cellular immune responses that attacked breast cancer tumours. These cellular responses alone were enough to kill HER-2 positive cells in mice unable to make antibodies.

A version of the vaccine is now undergoing human safety tests.

A different HER-2 vaccine made headlines earlier this year when it halved the number of deaths in women with HER-2 positive breast cancer. The vaccine also slowed breast cancer recurrence. However, the researchers found that 26 months after vaccination, there was no significant difference in cancer recurrence between vaccinated and unvaccinated women.

In the long run, it is vitally important to test the animal research in humans to determine which approaches are valid and which are not. Early promising results do not always translate into survival advantages, but as we learn more about the science and biology of cancer, the technical approaches can only improve.

The concept behind using the bodies immune system to fight disease, including cancer, is a solid one but getting vaccines to work has proven elusive so far in solid tumours. More promising results have been seen in immune-related cancers such as NHL, but as the technology improves, we may one day see some advances in women with breast cancer.

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