Researchers from the Washington University School of Medicine carried out an early clinical trial to test how safe a breast cancer vaccine is. Preliminary results, however, also point to the possibility of the vaccine slowing down cancer progression by working with a patient's immune system.

Published in the journal Clinical Cancer Research, the clinical trial involved 14 patients diagnosed with metastatic breast cancer and have the protein mammaglobin-A in their systems. It's unclear what the protein's role is in healthy breast tissue but it is expressed in abnormally high levels when tumors are present. The breast cancer vaccine then works by stimulating the immune system to target mammaglobin-A, attacking and destroying cells containing the protein to hamper tumor growth.

"Being able to target mammaglobin is exciting because it is expressed broadly in up to 80 percent of breast cancers, but not at meaningful levels in other tissues. In theory, this means we could treat a large number of breast cancer patients with potentially fewer side effects," said William E. Gillanders, MD, professor of surgery, breast cancer surgeon, and the study's senior author.

During the clinical trial, subjects reported few side effects, with eight experiencing mild or moderate effects like tenderness at the site of vaccination, mild flu-like symptoms and rashes. None of the patients manifested severe or life-threatening side effects after being vaccinated.

After one year of receiving the vaccine, around half of the subjects showed no cancer progression. In a control group with 12 patients who did not receive the vaccine, a fifth of the subjects showed no cancer progression.

Based on the results of the clinical trial, Gillanders and his colleagues are gearing up for a larger study to test out the vaccine on newly diagnosed patients of breast cancer. Newly diagnosed patients are ideal subjects because they still have healthier immune systems than those who have already undergone therapy.

"If we give the vaccine to patients at the beginning of treatment, the immune systems should not be compromised like in patients with metastatic disease. We also will be able to do more informative immune monitoring than we did in this preliminary trial," explained Gillanders.

The clinical trial received support from the Breast Cancer Research Program, Gateway for Cancer Research, The Foundation for Barnes-Jewish Hospital, the NCI Cancer Center Support Grant, the National Cancer Institute, and George and Diana Holway.

Other authors include: Thalachallour Mohanakumar; Peter Goedegebuure; Timothy Fleming; Feng Gao; A. Craig Lockhart; Michael Naughton; Cynthia Ma; Matthew Ellis; Mark Sturmoski; Lijin Li; John Herndon; Natalia Tucker; and Venkataswarup Tiriveedhi.

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