A DNA vaccine targeting mammaglobin-A, a breast cancer-associated antigen, was proven safe and found to effectively elicit immune responses in women with metastatic breast cancer, according to a new study. The study was published in Clinical Cancer Research (2014; doi:10.1158/1078-0432.CCR-14-0059).
“This study builds on extensive studies of mammaglobin-A immunobiology and confirms that it is an attractive target for immune intervention in breast cancer patients,” said study author William E. Gillanders, MD, professor of surgery at Washington University School of Medicine in St. Louis, Missouri.
“Mammaglobin-A is an excellent target for breast cancer vaccine therapy because it is specific to breast cancer tissue, and it is overexpressed in most breast cancers, including noninvasive, invasive, or metastatic breast cancers,” said Gillanders. “These unique properties mean that a mammaglobin-A vaccine could be therapeutic, given after breast cancer has developed to treat or prevent disease recurrence, or preventive, given to patients before they are diagnosed with breast cancer.”
Gillanders and colleagues treated 14 patients with metastatic breast cancer with the mammaglobin-A vaccine and observed no significant adverse events. The patients reported only minor adverse effects such as reactions at the vaccination site or temporary fevers.
Using flow cytometry, the researchers measured the frequency of mammaglobin-A-specific CD8 T cells at baseline and after vaccination, and found that it increased more than fourfold, indicating a robust immune response.
“Measuring mammaglobin-A-specific CD8 T cells is one way to measure vaccine efficacy,” Gillanders explained. “Although CD8 T cells are only one component of the immune response, they are arguably the most important component.”
The analysis also showed that the patients treated with the vaccine had prolonged progression-free survival compared with those who did not receive the vaccine; however, the study was not designed to compare survival among these groups.
“I predict that this vaccine and similar vaccines could have the greatest clinical impact in patients who have completed standard treatment regimens, such as chemotherapy, surgery, or radiation, to minimize the risk of recurrence,” Gillanders said. “That would help to improve the overall success rate associated with current treatment paradigms.”
This study was funded by the US Department of Defense, Gateway for Cancer Research, the Foundation for Barnes-Jewish Hospital, and the National Cancer Institute. Gillanders declared no conflicts of interest.