A new experimental vaccine, which researchers say could be effective for breast cancer, has been developed. The new vaccine, which is an improved version of an earlier vaccine is said to deliver a gene into cells which can fight the cancer which grows in response to a growth factor called HER-2. About 25 % of the women with breast cancer have tumors that are HER-2 positive and the new vaccine hopes to produce immune system proteins as well as tumor destroying cells.

Wei-Zen Wei of Wayne State University in Detroit, who led the study, said in a telephone interview, "In our own mind it is a very significant advance because we have put the gene into the cells in the body. The vaccine is produced by your own cells. It is made right in your body."

Made by Genentech Inc., Herceptin, also known as trastuzumab, is an expensive man-made antibody approved for the treatment of breast cancer, which targets cancers with HER-2 tumors. Tumor cells often become resistant to Herceptin after a while and start growing again.
 
Wei, says the new vaccine elicits immune responses that kill HER-2 positive breast tumors in mice, irrespective of whether or not they've become Herceptin resistant, "Regardless of whether tumor cells are resistant, if immune cells are properly primed by immunization we can destroy these cells," Wei tells WebMD.

The new vaccine uses naked DNA that carries the genetic code for a key piece of the HER-2 molecule. After injection of the DNA into the skin, a process called electroporation is undertaken in which a small electric pulse is administered to help cells take up the DNA and produce the protein that elicits immune responses. "Both tumor cells that respond to current targeted therapies and those that are resistant to these treatments were eradicated," Wei said. "This may be an answer for women with these tumors who become resistant to the current therapies."

A different HER-2 vaccine made headlines last April when it halved the number of deaths in women with HER-2 positive breast cancer and also slowed breast cancer recurrence. A study undertaken by researchers at San Antonio's Brooke Army Medical Center found no significant difference in cancer recurrence between vaccinated and unvaccinated women after 26 months.

Tests on mice with the new vaccine have shown positive results including eliminating HER-2 tumors that had developed resistance to drugs designed to fight them said the researchers in the journal Cancer Research.

The vaccine is now undergoing human safety tests, which is a major step forward according to Gary Yang, MD, associate professor of radiation medicine at Roswell Park Cancer Institute in Buffalo, N.Y. "These studies accomplished a lot -- but we need to find out why the immune system cannot sustain this efficacy,"  said Yang to WebMD. "The clinical research into breast cancer vaccines is not going to be a home run," he added.

According to the American Cancer Society Breast cancer with 1.3 million new cases diagnosed annually and 465,000 deaths is the top cause of cancer death among women worldwide.

Wei is feels that the vaccines will prove to be powerful cancer treatments in the long run and might even be useful in preventing cancer from recurring in women who have been successfully treated using Herceptin or other drugs.

"Ultimately, we will be using the best defense we have to fight cancer -- the human immune system," she says. "It is a very challenging thing to do. We hope we have reached a point where we can make it useful to patients.”

There are several groups who are working on breast cancer vaccines that target HER2, including Seattle-based Dendreon Corp, with its vaccine Neuvenge, and Apthera, whose vaccine is called Neuvax.