Vaccine Effectively Decreases Breast Cancer in Mice

A vaccine that significantly decreases tumors in a mouse model closely imitating 90% of human breast and pancreatic cancer cases—including ones that do not respond to traditional therapies—has been developed by researchers at the Mayo Clinic in Arizona and the University of Georgia.

The distinctive mice used in the study were engineered by Sandra Gendler, PhD, a professor of therapeutics for cancer research at Mayo Clinic in Arizona and co-senior author on the study.

These mice, like humans, develop tumors that overexpress the protein MUC1, which is frequently associated with tumors, on the exterior of their cells. Cancer alters the makeup of cellular structure, causing MUC1 to be produced at high levels and thereby promoting tumor formation. According to Gendler, MUC1 is observed on over 70% of all deadly cancers, including those of the breast, pancreas, ovaries, and skin.

The new vaccine works by targeting and acting against the MUC1 proteins expressed along the exterior of the cancerous cells, said Gendler.

"This is the first time that a vaccine has been developed that trains the immune system to distinguish and kill cancer cells based on their different sugar structures on proteins such as MUC1," said Gendler in a press release from the Mayo Clinic. "We are especially excited about the fact that MUC1 was recently recognized by the National Cancer Institute as one of the three most important tumor proteins for vaccine development."

The vaccine has the potential ability to prevent recurrence in cancer patients, or even to help protect individuals at high risk for particular cancers, said Gendler. The vaccine could also be paired with traditional treatments such as chemotherapy to treat cancers that cannot be treated with surgery, such as pancreatic cancer.

"This vaccine elicits a very strong immune response," said study co-senior author Geert-Jan Boons, PhD, a professor of chemistry and a researcher in the UGA Cancer Center and its Complex Carbohydrate Research Center in Athens.

This vaccine may also one day be used to help treat a subset of patients whose cancer is unresponsive to hormonal therapies like tamoxifen or aromatase inhibitors, or the drug Herceptin. These individuals suffer from “triple-negative tumors,” which are exceedingly aggressive and difficult to treat, said Boons.

"In the US alone, there are 35,000 patients diagnosed every year whose tumors are triple-negative," Boons said. "So we might have a therapy for a large group of patients for which there is currently no drug therapy aside from chemotherapy."

Currently, Gendler and her colleagues are testing the vaccine's effectiveness against human cancer cells in culture with the hopes of starting phase 1 clinical trials to test the safety of the vaccine by late 2013.

The study abstract is available online from the journal Proceedings of the National Academy of Sciences.