MONDAY, SEPTEMBER 26, 2016

Study may show why some cancer vaccines are unsuccessful

A recent study in mice suggests that a traditional ingredient in therapeutic cancer vaccines may be preventing the vaccines from achieving successful results.

Cancer vaccines typically include IFA, which is short for incomplete Freund's adjuvant. Adjuvants are chemicals added to vaccines that can stimulate an immune response. IFA is non-biodegradable and it was thought the adjuvant could allow the vaccine to stay in the body longer and elicit a greater immune response. The study found that most T-cells attacked the injection site, not the site of a tumor, NPR reports.

"The body doesn't know how to deal with the mineral oil (in IFA), and the body cannot get rid of that big blob of vaccine... that sits under the skin," Willem Overwijk, an author of the study, said, according to NPR. "The T-cells go back and try to kill the oil, but they can't."

Therapeutic cancer vaccines contain a cancer-specific peptide, or protein fragment, that is injected under the skin of a patient. The immune system is meant to recognize the peptide, generate cancer-fighting T-cells and attack the cancer. For the vaccines to work, the T-cells must find their way to the tumors.

When IFA was replaced with saline and water, substances easily processed by humans and mice, the T-cells went to the tumors and started to destroy them.

If the results are confirmed by future studies, cancer vaccine developers could change their approach in making the vaccines, NPR reports.

"(It's) an eye-opener," Overwijk said, according to NPR. "(A kind of) 'Aha!' moment after years of using these same vaccines."

The study was published in the latest issue of Nature Medicine.