Flu Shots As Cancer Treatment
Written by Laurel Geraci
Edited by Tanishq Vaidya
July 31st 2021
Edited by Tanishq Vaidya
July 31st 2021
By now, we’re all aware of the benefits of a seasonal flu shot for immunocompetent persons--but are you aware of the extra benefits that cancer patients can receive from it? According to new scientific studies, the average influenza shot shows great potential for cancer treatment! Scientists are finding that when the seasonal flu shot is injected into a cancerous tumor, the tumor undergoes a microenvironmental change such that the immune system can help eradicate cancer cells!
So how exactly does this work? First, we need to understand the two main types of tumor microenvironments: cold and hot. Cold tumors are often described as “immune deserts” because they mainly host regulatory T cells, which are white blood cells that help the body distinguish its own cells from other cells to prevent autoimmune diseases (Lindau et al., 2013). On the other hand, hot tumors host inflammatory immune cells, which are capable of signalling the immune system to attack foreign cells in order to prevent cell damage (Martínez-Lostao et al., 2015). Since hot tumor microenvironments have better resources to fight invaders, it’s no wonder that immunotherapy proves more successful when used in hot tumors compared to cold! It might also seem clear that current immunotechnology research has a great focus on converting cold tumors into hot.
However, a major challenge of fighting cancer cells using this method is that tumor cells originate from cells that were once normal, making it difficult for the immune system to make strong differentiations against healthy and cancerous cells. This is where the flu vaccine can help; when injected directly into a cold tumor, the body better recognizes the infected tumor as foreign. This causes an immune response which recruits CD8+ T cells to the tumor location. These cells are cytotoxic white blood cells that specifically target tumor cells to reduce tumor growth! Researchers observed this immune response results in the microenvironmental change from a cold to a hot tumor, which has the potential to improve the efficacy of immunotherapy (Newman et al., 2020).
There are of course limitations to this study. It’s important to note that the combination of both the tumor cells and the flu vaccine working together produce this result. Thus, the type of cancer cells matters in the overall outcome. For example, cancer patients with lung tumors saw a great reduction in tumors injected with the influenza virus vaccine--yet patients with melanoma saw little to no changes in their tumor size. This is because lung tissue possesses a specific sugar residue (a sugar monomer; only 1 molecule) that influenza A viruses can bind to (called sialic acid residues), while skin tissue does not have this sugar (Kumlin et al., 2008). Yet regardless of its implication for cancer treatment, skin cancer patients should still receive an inactivated seasonal influenza vaccine. The flu shot still serves as a very effective tool against infection from the flu for everyone, and can even protect against influenza lung infections in lung cancer patients when injected into tumorous lung tissue! With this newfound tumor technology, we can expect to see greater outcomes for cancer patients all around the globe.
References
Kumlin, U., Olofsson, S., Dimock, K., & Arnberg, N. (2008). Sialic acid tissue distribution and influenza virus tropism. Influenza and other respiratory viruses, 2(5), 147–154. https://doi.org/10.1111/j.1750-2659.2008.00051.x
Lindau, D., Gielen, P., Kroesen, M., Wesseling, P., & Adema, G. J. (2013). The immunosuppressive tumour network: myeloid-derived suppressor cells, regulatory T cells and natural killer T cells. Immunology, 138(2), 105–115. https://doi.org/10.1111/imm.12036
Martínez-Lostao, L., Anel, A., & Pardo, J. (2015). How Do Cytotoxic Lymphocytes Kill Cancer Cells?. Clinical cancer research : an official journal of the American Association for Cancer Research, 21(22), 5047–5056. https://doi.org/10.1158/1078-0432.CCR-15-0685
Newman, J. H., Chesson, C. B., Herzog, N. L., Bommareddy, P. K., Aspromonte, S. M., Pepe, R., Estupinian, R., Aboelatta, M. M., Buddhadev, S., Tarabichi, S., Lee, M., Li, S., Medina, D. J., Giurini, E. F., Gupta, K. H., Guevara-Aleman, G., Rossi, M., Nowicki, C., Abed, A., Goldufsky, J. W., … Zloza, A. (2020). 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, 117(2), 1119–1128. https://doi.org/10.1073/pnas.1904022116