How Cancers Hide From Our Immune Response
Written by Lance Jimenez
Edited by Hannah Parducho
May 2, 2021
Edited by Hannah Parducho
May 2, 2021
Our immune system is our body’s security system: it monitors and protects our body from bacteria, viruses, and even cancer! It detects and removes these disease-causing agents to keep us happy and healthy. Though it works hard, this system is not perfect, so we get sick from time to time. The problem arises when certain disease-causing agents, such as cancer cells, become sneaky and avoid our bodies’ defenses. Cancer has become an increasingly concerning disease with approximately 158.3 deaths per 100,000 affected people and an expected 39.5% of people being diagnosed with cancer in their lifetime (National Cancer Institute, 2020). Cancer cells are created when normal cells become mutated. As a result, they grow and duplicate uncontrollably and become a serious risk when they outcompete our normal cells for nutrients. Finding out how cancers avoid our immune system is essential to improving human health.
How does the human body normally respond to cancer cells? Cancer cells mutate and replicate their DNA very quickly, and small segments of that DNA may end up in the wrong parts of the cell (Li, et al. 2020). These DNA segments are sensed as intruders, so the cell responds by releasing a signalling molecule called cGAMP (Li, et al. 2020). cGAMP acts like a flare gun, altering immune cells of the cancer’s presence. Our immune system finds the source of the signal then attacks the cancer cells. This response to cancer is so effective that it is the basis of a common cancer treatment, immunotherapy (National Cancer Institute, 2019).
What was puzzling, however, was that some cancer cells can avoid being detected by the body’s immune response. Researchers from the Memorial Sloan Kettering Cancer Center discovered cancer cells that create the protein, ENPP1 (Memorial Sloan Kettering Cancer Center, 2020). This protein, found on the outside of the cell, degrades the cGAMP as it exits the cell. If the immune system cannot detect cGAMP, it will not get alerted. Cancer cells are then free to grow uncontrollably, without being noticed. This protein weakens the effectiveness of the immune response and remains a problem for cancer treatments.
It’s not all bad news, though. Now that ENPP1 has been identified, new cancer treatments can be developed against it. ENPP1 is present on the outside of the cell, so it can be a target for pharmaceuticals. Drugs are less likely to harm normal cells since ENPP1 is only expressed by cancer cells. ENPP1 becomes a double-edged sword; it may help cancer cells evade our immune system, but it also marks which cells need to be eliminated. Each new discovery in cancer function allows researchers to create new ways of fighting the disease. Eventually, we can help out our bodies’s security catch and remove even the sneakiest of cancer cells!
References
Li, J. , et al. (2020). “Metastasis and immune evasion from extracellular cGAMP hydrolysis.” Cancer Discovery. 10.1158/2159-8290.CD-20-0387
Memorial Sloan Kettering Cancer Center. (2020, December 28). “Discovery about how cancer cells evade immune defenses inspires new treatment approach.” ScienceDaily. Retrieved January 22, 2021 from www.sciencedaily.com/releases/2020/12/201228114557.htm
National Cancer Institute. (2020, September 25). “Cancer Statistics.” NCI. Retrieved January 23, 2021 from https://www.cancer.gov/about-cancer/understanding/statistics
National Cancer Institute. (2019, September 24). “Immunotherapy to Treat Cancer.” NCI. Retrieved January 23, 2021 from https://www.cancer.gov/about-cancer/treatment/types/immunotherapy