Injecting tumors with influenza vaccines, including some FDA-approved seasonal flu shots, can trigger an immune system response, according to a study published in the Proceedings of the National Academy of Sciences.

The majority of patients with cancer have “cold” tumors, according to the study authors. This includes tumors that do not contain many immune cells or ones that have cells that suppress the ability of the immune system to fight them. “Hot” tumors show higher rates of response to treatment and patients with such tumors have improved survival rates.

Changing the microenvironment of tumors to increase the immune system’s response to them has been the goal of research and clinical studies. Currently, some immunotherapies use live pathogens as cancer therapy, but these treatments have shown lasting effects in a limited number of patients and cancer types. The study authors wanted to understand how the immune response against pathogens such as influenza and their components could improve weaker response against tumors.

Using the National Cancer Institute database, researchers found that patients with lung cancer and hospitalization for a lung infection from influenza at the same time lived longer than patients who had lung cancer with no influenza.

Researchers inactivated the influenza virus, thereby creating a flu vaccine, and directly injected it into melanoma. They found that the injection either slowed the growth or shrunk the tumor itself. The injection also made the tumor “hot” by increasing the proportion of a type of immune-stimulating cells, known as dendritic cells, into the tumor. This process led to an increase in CD8+ T cells that recognize and kill tumor cells.

Researchers then tested whether an FDA-approved flu vaccination could be repurposed as a cancer treatment. This infection of flu shots also resulted in reduction of tumor growth, according to the study.

Five different influenza shots for the 2017-2018 flu season were used in this research and 4 were effective in achieving the same results in fighting tumors. Only 1 flu shot with a synthetic adjuvant had no antitumor effect; it also maintained B cells 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 was effective.

More research is needed for additional consideration regarding which adjuvants are included in immunotherapies and which vaccines could be used to treat cancer, the study authors concluded.


Reference

Newman J, Chesson C, Herzog N, et al. Intratumoral injection of the seasonal flu shot converts immunologically cold tumors to hot and serves as an immunotherapy for cancer. Proceedings of the National Academy of Sciences of the United States of America. Published December 30, 2019. https://doi.org/10.1073/pnas.1904022116. Accessed January 9, 2020.