A cancer vaccine could one day lessen the need for chemotherapy treatments like this one being mixed in a pharmacy at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins School of Medicine. Image credit: Win McNamee/Getty Images
Though a true cure for all cancer has yet to be achieved, researchers have taken another step closer to creating a vaccine to treat advanced stage cancers. The results, recently published in the journal Nature, showed a remarkable ability to reduce tumor size and teach the immune system to prevent regrowth. Called nanoparticle RNA vaccine, it’s part of a new realm of cancer immunotherapy treatments, which harness the body’s own immune system to fight cancer, resulting in fewer side effects and better tumor suppression rates than traditional chemotherapy.
The trial started in May 2015 with a single patient. Since then, three patients with metastatic stage-four cancer have completed a treatment of six weekly vaccinations, a total of seven patients have received treatment so far. All patients had received conventional cancer treatments before, and one had also received a different form of cancer immunotherapy known as a checkpoint inhibitor. The study continues to recruit patients through the end of 2017.
Study authors Mustfa Diken, deputy director of the Immunotherapy Development Center at Translational Oncology (TRON) at the University Medical Center of the Johannes Gutenberg University Mainz (JGU), and Lena M. Kranz, project leader at TRON, described how the vaccine works in a jointly composed email to mental_floss. “Nanoparticle RNA vaccine consists of a biological model that is used by the body to translate genomic information into proteins,” they said. “You can envision the nanoparticle RNA vaccine as an envelope containing a message for the immune system on what the tumor looks like."
The researchers injected a low dose of the vaccine—RNA surrounded by a fatty acid (lipid) membrane—intravenously into mouse models and human subjects with advanced melanoma. “The vaccine … finds its way specifically to cells of the immune system residing in lymphoid compartments, such as the spleen and the lymph nodes, due to its unique properties,” they said. These cells are called dendritic cells, and they specialize in “taking up” particles and fluids from their surroundings and converting information about these foreign intruders in such a way “that they educate the immune system on who to fight.”
The dendritic cells are then able to “open” the envelope of the vaccine, “read” the message, and pass that on to antigen-specific T-cells, which then recognize a cancerous tumor and attack it. Antigens, often proteins, are any molecules that stimulate the immune system to produce antibodies, and RNA is the molecule from which the proteins are synthesized.
The vaccine induced an immune response to multiple tumor antigens in the first three patients, and caused what they refer to as “stable disease.” That means patients stayed tumor-free during and after the vaccination, so long as their tumor had been removed prior to the vaccination, or their metastases stayed stable (did not spread) during and after vaccination.
While the idea of a cancer vaccine may give some hope that this vaccine can prevent cancer, as is the case with existing vaccines for cancers caused by viruses like those in the human papilloma virus family and hepatitis B, this is a prophylactic vaccine; it would only be given to those already with cancer. “Nevertheless, the immunological mechanism of the treatment is that of a vaccine … or more precisely, a therapeutic vaccine,” the researchers said.
They were pleasantly surprised to find that even lower doses in the first few patients induced immunity. In the next patients, they’ll test higher doses. Most exciting, they said, is the fact that, since RNA can encode any antigen, any antigen for a given tumor can be incorporated into the vaccine, making it applicable to any type of tumor.