messenger RNA (or mRNA) “Teaches” Our Bodies How to Fight Diseases on Our Own

Dozens of clinical trials are testing mRNA treatment vaccines in people with various types of cancer, including pancreatic cancer, colorectal cancer, and melanoma. Some vaccines are being evaluated in combination with drugs that enhance the body’s immune response to tumors. But no mRNA cancer vaccine has been approved by the US Food and Drug Administration for use either alone or with other cancer treatments.

“mRNA vaccine technology is extremely promising for infectious diseases and may lead to new kinds of vaccines,” said Elad Sharon, M.D., M.P.H., of NCI‘s Division of Cancer Treatment and Diagnosis. “For other applications, such as the treatment of cancer, research on mRNA vaccines also appears promising, but these approaches have not yet proven themselves.”

With findings starting to emerge from ongoing clinical trials of mRNA cancer vaccines, researchers could soon learn more about the safety and effectiveness of these treatments, Dr. Sharon added. Over the past 30 years, researchers have learned how to engineer stable forms of mRNA and deliver these molecules to the body through vaccines. Once in the body, the mRNA instructs cells that take up the vaccine to produce proteins that may stimulate an immune response against these same proteins when they are present in intact viruses or tumor cells. Among the cells likely to take up mRNA from a vaccine are dendritic cells, which are the sentinels of the immune system. After taking up and translating the mRNA, dendritic cells present the resulting proteins, or antigens, to immune cells such as T cells, starting the immune response.

“Dendritic cells act as teachers, educating T cells so that they can search for and kill cancer cells or virus-infected cells,” depending on the antigen, said Karine Breckpot, Ph.D., of the Vrije Universiteit Brussel in Belgium, who studies mRNA vaccines. The mRNA included in the Pfizer-BioNTech and the Moderna coronavirus vaccines instructs cells to produce a version of the “spike” protein that studs the surface of SARS-CoV-2. The immune system sees the spike protein presented by the dendritic cells as foreign and mobilizes some immune cells to produce antibodies and other immune cells to fight off the apparent infection. Having been exposed to the spike protein free of the virus, the immune system is now prepared, or primed, to react strongly to a subsequent infection with the actual SARS-CoV-2 virus.

Source: https://www.cancer.gov/