Our body’s immune system forms a defensive shield that would impress any fighting force. One of its most powerful weapons is inflammation, a carefully orchestrated maneuver designed to eliminate enemies such as bacteria, injured cells, and chemical irritants. We probably wouldn’t survive beyond infancy without it.
But inflammation has a split personality – besides the beneficial elimination, it can wreak havoc for those unfortunate enough to experience it. We now know that inflammation’s dark side is a powerful force in cancer development where it aids and abets tumor growth to spread it around the body.
Experts have long suspected inflammation may play some role in cancer’s development, but researchers have only recently pinpointed chronic inflammation as a primary risk factor for cancer and other serious health conditions. In 1863, German scientist and physician Rudolf Virchow was the first to make the connection when observing that cancer often develops at sites of chronic inflammation. Because chronic inflammation causes few, if any, outward symptoms and because inflammation also benefits us at times, it’s taken quite a long time to see the relationship between inflammation and cancer.
Inflammation is a normal physiological response that causes injured tissue to heal. An inflammatory process starts when chemicals are released by the damaged tissue, and in response, white blood cells aid other cells to divide and grow in rebuilding tissue and repairing the injury. Once the wound is healed, the inflammatory process ends.
In chronic inflammation, the inflammatory process may begin even if there is no injury, and it does not end when it should. Why the inflammation continues is not always known. Chronic inflammation may be caused by infections that don’t go away, abnormal immune reactions to normal tissues, or conditions such as obesity. Over time, chronic inflammation can cause DNA damage and lead to cancer. For example, people with chronic inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, have an increased risk of colon cancer.
When a tiny tumor starts growing from a few rogue cells, it can scavenge enough oxygen and nutrients from its surroundings. As it grows bigger, it’s demand starts to outstrip the supply, and cancer cells suffer. In their struggle to survive, they accumulate more and more genetic faults and release chemical signals that lure immune cells called macrophages and granulocytes to infiltrate the tumor.
Once inside the tumor’s inner sanctum, these cells secrete molecules called cytokines that kick-start the growth of blood vessels (angiogenesis) to ferry in much needed oxygen and nutrients. Other cytokines encourage growth of a sort of cellular ‘pillow’ called the stroma against which the tumor rests. Meanwhile, other inflammatory cells spritz the tumor with free radical molecules that further damage their DNA. Inflammation might also fire the starting gun for metastasis by producing chemicals that help tumor cells nibble through the molecules tethering them to their surroundings.
Taking all this together, it’s clear that fledgling tumors hijack inflammation and use it to accelerate the progression towards full-blown cancer.
The reason inflammation becomes chronic isn’t always apparent. It may be caused by infections that don’t go away, abnormal immune reactions to normal tissues, or certain conditions like obesity. Over time, chronic inflammation may damage DNA, leading to conditions like heart disease, type 2 diabetes, stroke and cancer. “Anything that causes inflammation will cause the DNA of a cell to replicate faster,” says Brad Mons, DO, Head and Neck Surgeon at our hospital in Tulsa. “The more your cells replicate, the higher chance you have of cancers developing.”
Sometimes, cancer-causing chronic inflammation stems from a disease characterized by inflammation; colitis, pancreatitis, and hepatitis, are linked to a greater risk of colon, pancreatic, and liver cancers, respectively. In these diseases, immune cells create highly reactive molecules containing oxygen and nitrogen that can damage DNA.
Chronic inflammation also may result from a chronic infection; H. pylori is often linked to stomach cancer, and hepatitis B and hepatitis C are often linked to liver cancer. HIV increases the risk of other viruses and very rare cancers, including Kaposi sarcoma, non-Hodgkin lymphoma, and invasive cervical cancer.
In other cases, environmental factors are the culprits. Asbestos exposure increases the risk for mesothelioma. In fact, many environmental carcinogens and risk factors are associated with some form of chronic inflammation.
Today, researchers are exploring whether oxygen sensors in the body can be manipulated to reduce chronic inflammation. One study found that tricking immune cells into believing they’re lacking oxygen makes them retreat from the site of inflammation to conserve energy. Researchers are now studying whether medications could be developed to turn on certain proteins that, when activated, inhibit the body’s inflammatory response.
Evidence is also building that aspirin may help prevent chronic inflammation; the non-steroidal anti-inflammatory drug works by reducing the production of prostaglandins, chemicals that promote inflammation, pain, and fever. In a 2016 report published in the Journal of the American Medical Association, researchers who studied aspirin use in 135,000 patients concluded “long-term aspirin use was associated with a modest but significantly reduced risk for overall cancer, especially gastrointestinal tract tumors. Regular aspirin use may prevent a substantial proportion of colorectal cancers too.
Foods that help reduce your cancer risk also help reduce chronic inflammation and vice-versa. So, following these guidelines will ultimately reduce your risk of a variety of chronic diseases and improve your quality of life.
The bottom line
Better known to most of us by its brand name aspirin, acetylsalicyclic acid has been used for over a century to quell inflammation, and there’s now a body of evidence highlighting its potential in cancer prevention. While there’s still a ways to go to work out who should take aspirin, how much, and for how long, it’s becoming clear that blocking inflammation will play a big role in cancer prevention and treatment in the future.