In a new study, researchers found that injecting tumors with influenza vaccines, including some FDA-approved seasonal flu shots, turns cold tumors to hot.
This discovery could lead to immunotherapy to treat cancer.
The research was conducted by physicians and scientists at Rush University Medical Center
Currently, some immunotherapies utilize live pathogens (disease-causing organisms) as cancer treatments, but these treatments only have shown lasting effects in a limited number of patients and cancer types.
In the study, the team wanted to understand how strong immune responses against pathogens like influenza and their components could improve the much weaker immune response against some tumors.
Drawing on a National Cancer Institute database, the researchers found that people who had lung cancer and hospitalization for a lung infection from influenza at the same time lived longer than those who had lung cancer with no influenza.
They found a similar outcome in mice with tumors and influenza infection in the lung.
To find an alternative to the limitations of live infection, the researchers inactivated the influenza virus, essentially creating a flu vaccine.
They found that direct injection of this vaccine into the skin melanoma of the mice resulted in the tumors either growing slower or shrinking.
The injection made the tumor hot by increasing the proportion of a type of immune-stimulating cells (called dendritic cells) in the tumor, leading to an increase in a type of cells known as CD8+ T cells, which recognize and kill tumor cells.
Importantly, injecting a skin melanoma tumor on one side of the body not only resulted in the reduced growth of that tumor, but also in reduced growth of a second skin tumor on the other side of the same mouse that was not injected.
The study authors note that they found similar outcomes in mice with metastatic triple-negative breast cancer, in which both primary tumor growth and the natural spread of the breast tumor to the lungs were reduced after injection only into the primary tumor.
Based on this result, they hope that in patients, injecting one tumor with an influenza vaccine with lead to immune responses in their other tumors as well.
The team also examined if seasonal flu vaccines that are already FDA-approved could be repurposed as treatments for cancer.
The researchers found that injection of such flu shots also resulted in the reduction of tumor growth.
They used a patient’s lung tumor and melanoma metastasis. They found that putting the flu shot in these patient-derived tumors causes them to shrink, while untreated tumors continued to grow.
Five different influenza shots for the 2017-2018 flu season were used in this research. Four were effective in achieving the same results in fighting tumors.
One flu shot with a synthetic adjuvant (an immune modifier) had no antitumor effect and maintained other cells (called regulatory B cells or Bregs) that suppress an immune response.
When the adjuvant was removed from the vaccine, it became effective. Similarly, when the B cells were removed, the vaccine also then became effective.
The team says since humans and mice are about 95% genetically identical, the hope is that this approach will work in patients. The next step planned is to conduct clinical trials to test various factors.
One author of the study is Andrew Zloza, MD, Ph.D., assistant professor at Rush Medical College.
The study is published in the Proceedings of the National Academy of Sciences.
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