Oral Breast Cancer Vaccine May Offer New Preventative Medicine

Breast cancer recurrence may be prevented by a novel two-pronged immune system attack on cancer cells, according to new research.

This is the first scientific study that involved using oral delivery of a unique virus—known as recombinant adeno-associated virus (AAV)—as a cancer vaccine. First author and University of Cincinnati (UC) Cancer Institute (OH, USA) research assistant professor Jason Steel, PhD, and colleagues reported their findings in the January 8, 2013, issue of Molecular Therapy, the journal of the American Society of Gene and Cell Therapy.

While other oral breast vaccines have been studied in animal models, these vaccines raised human safety concerns because they used bacteria known to have potential harm to human health. Working with US National Institutes of Health (NIH; Bethesda, MD, USA) researchers, the UC scientists looked for a way to develop a vaccine using AAV, a virus that has been shown to have nominal negative effects on human health and is currently being evaluated as a gene therapy platform for the treatment of inherited genetic disorders.

“AAV is special because the virus survives the stomach,” explained Dr. Steel. “Normally, you introduce a virus by mouth and it is broken down in the stomach. This virus is resistant to breakdown, which opened up the possibility of administering it orally as a cancer vaccine.”

In this preclinical animal study, the UC scientists assessed two strains of AAV—one that had the capability of leaving the stomach and move into the bloodstream, the other staying in the stomach. Studies were conducted to validate both short-term and long-term impact on the reduction of breast cancer tumors. The scientists also evaluated which delivery method was more effective—oral versus the traditional intramuscular (IM) injection.

“The strain that remained in the stomach was more effective at preventing breast cancer tumors than the strain that traveled systemically—100% of study subjects had no tumors for over a year following the treatment,” said Dr. Steel. “Additionally, we showed that oral delivery [versus IM injection] was more effective, resulting in a stronger immune response with greater than a 100% increase in antitumor antibodies at the lower doses and increased survival.”

Researchers noted that this AAV-based oral cancer vaccine has possibilities as a human breast cancer-prevention approach in individuals who have been treated for a specific type of breast cancer or those considered at increased risk for the disease. “We have done similar studies with different virus strains that have produced an antibody response,” added Dr. Steel. “With this virus, we get both an antibody and a tumor-killer T-cell response. By combining the two mechanisms of action in one vaccine, we are creating a two-pronged immune system attack on the cancer cells that appears to be more effective.”

The UC researchers plan to begin testing the AAV-based oral vaccine for prevention of other cancers, including lung cancer, sometime in 2013.

Related Links:
University of Cincinnati Cancer Institute
US National Institutes of Health